Targeting Alzheimer's pathophysiology with carbon dots: from mechanisms to therapy

Abstract

Alzheimer's disease continues to be a debilitating disorder, profoundly affecting the quality of life, despite decades of extensive research. The impermeability of the blood–brain barrier, multifactorial etiology of the disease and the repeated failures of single target therapy are the major contributors of this therapeutic stagnation. If there is a silver lining, it lies in the growing advancement of multi-targeted therapeutic approaches that address the complex pathophysiology of Alzheimer's disease. In this context, carbon dots have emerged as highly promising, ultrasmall and biocompatible nanomaterials capable of traversing the blood–brain barrier and targeting various pathophysiologies of the disease. These include but are not limited to inhibition of abnormal protein aggregation, scavenging of reactive oxygen species and attenuation of neuroinflammatory processes. This review aims to critically synthesize the current body of research on carbon dots with particular emphasis on their mechanistic insights, surface chemistry driven targeting strategies and ligand free transportation mechanisms. The indulgence of photodynamic therapy in targeting carbon dots has also been touched upon. The key regulatory hurdles and translational gaps have been addressed that hinder their journey from bench to bedside. This review highlights the potential of carbon dots as intelligent nanoplatforms by integrating the molecular and pharmacological perspectives.

---

Shourya Tripathi

Shourya Tripathi is a doctoral researcher at the CSIR-Central Drug Research Institute, Lucknow, India, pursuing her PhD in Biological Sciences. She earned her M.S. (Pharm.) in Pharmaceutics from the National Institute of Pharmaceutical Education and Research (NIPER), Raebareli, India. Her research investigates carbon dot–based nanoplatforms for the diagnosis and therapeutic modulation of Alzheimer's disease, with a focus on molecular interactions, neuroprotective mechanisms, and translational potential. Her broader scientific interests include nanomedicine, neuropharmacology, and the rational design of multifunctional nanotherapeutics.

Ramandeep Singh

Ramandeep Singh is a doctoral researcher in the Department of Molecular, Cellular and Developmental Biology at the University of California, Santa Barbara, USA. His research focuses on understanding the molecular and electrophysiological mechanisms governing neuronal signalling and sensory transduction. He earned his Master's degree in Pharmacology and Toxicology from the National Institute of Pharmaceutical Education and Research (NIPER), Mohali, India. His scientific interests span neuropharmacology, ion channel biology, and molecular neuroscience, with a broader focus on elucidating mechanisms of neural communication and neurodegenerative pathology.

Srishty Jaiswal

Srishty Jaiswal is a doctoral researcher in the Division of Pharmaceutics and Pharmacokinetics at the CSIR-Central Drug Research Institute, Lucknow, India, where she is pursuing her PhD in Biological Sciences. She obtained her Master's degree in Pharmaceutics from Panjab University, Chandigarh, India. Her research focuses on nanomedicine and advanced formulation strategies aimed at improving the bioavailability and therapeutic performance of drugs. Her scientific interests include targeted drug delivery, pharmacokinetic optimisation, and the development of nanoscale systems for treating complex and chronic diseases.

Mitali Sethi

Mitali Sethi is a doctoral researcher in the Division of Pharmaceutics and Pharmacokinetics at the CSIR-Central Drug Research Institute, Lucknow, India. Her research focuses on nanomedicine and advanced drug delivery systems aimed at enhancing pharmacokinetic efficiency and therapeutic precision. Her scientific interests include formulation development, targeted delivery strategies, and translational approaches in nanotherapeutics for complex diseases.

Manish K. Chourasia

Dr. Manish K. Chourasia is a Chief Scientist and Head of the Division of Pharmaceutics and Pharmacokinetics at the CSIR-Central Drug Research Institute, Lucknow, India. He obtained his PhD in Pharmaceutical Sciences from Dr. Harisingh Gour University, India and completed his postdoctoral research at the National University of Singapore. His work focuses on nanomedicine, targeted drug delivery, and pharmacokinetic optimisation for cancer and neurodegenerative disorders. With over a hundred publications, multiple patents, and extensive mentorship experience, he continues to lead innovation in translational pharmaceutics and the development of advanced therapeutic platforms.

---

1. Introduction

Carbon dots (CDs) were serendipitously discovered in the year 2004 by Xu et al., when they observed fluorescence during separation of carbon nanotubes from carbon soot using gel electrophoresis.¹ Following this study, Sun et al. synthesized photoluminescent nanoparticles with a diameter of 5 nm and christened them quantum sized CDs.² CDs may be defined as discrete spherical particles of size generally less than 10 nm in diameter with inherent fluorescence. They are comprised of highly systematic carbon atoms along with oxygen and nitrogen containing surface groups. The carbon core includes an sp² hybridized structure that contains oxygen in various forms such as hydroxyl, aldehyde and carboxyl groups. The carbon atoms have a large surface area and high aspect ratio along with good thermal and chemical stabilities.^3,4 The properties that have made CDs excellent nanocarriers include their high-water solubility, wide specific area, good biocompatibility, low toxicity, environmental friendliness, photochemical stability, good conductivity and various biological properties.^5,6 Owing to these unique properties, CDs are being exploited in various applications such as pH sensing, cell imaging, bioimaging, optoelectronics, and as fluorescent probes in photocatalysis, optical thermometry and most importantly drug delivery.^7,8 CDs have been exploited for management of numerous diseases including cancer, infectious and inflammatory disorders, ocular disorders and a variety of brain disorders.^9,10 In the treatment of brain disorders, CDs have shown the property of crossing the blood–brain barrier and targeting various nervous disorders.¹¹

Progressive loss of neurons in the central or peripheral nervous system may cause various neurological disorders such as Alzheimer's disease (AD), Parkinson's disease, Huntington's disease, prion disease and amyotrophic lateral sclerosis. The catastrophic breakdown of neural network structure and function, accompanied by the degeneration of neurons, which are rendered incapable of efficiently renewing themselves, ultimately leads to impairments in cognition, memory, behaviour and sensory or motor functions.^12,13 Dementia has become one of the most pressing global health challenges of our time. As per the World Health Organization's 2022 blueprint for dementia research, a staggering 55.2 million people are affected by this condition across the globe. The occurrence of dementia in people aged 60 and above differs across regions, with Europe reporting the highest at 6.5%, followed by South-East Asia at 2.9%, and other regions ranging between 3.1 and 5.7%. It has been estimated that the number of individuals living with dementia is expected to rise to 78 million by the year 2030, whereas the global economic burden including caregiving, medical interventions and social services is projected to surpass US$ 2.8 trillion. This situation is poised to have far reaching implications on individuals, families and society at large.¹⁴ AD, the most common form of dementia, represents an escalating global health challenge and follows similar epidemiological patterns. In the United States, one in nine individuals aged 65 and above is affected by AD, with approximately 1275 new cases diagnosed annually per 100 000 individuals.^15,16 Patients suffering from AD exhibit significant accumulation of amyloid-β (Aβ) plaques and neurofibrillary tangles in the brain, along with a detrimentally cascading series of pathological phenomena including synaptic dysfunction, neuroinflammation, mitochondrial impairment and vascular abnormalities. This destructive progression ultimately culminates in neuronal senescence.^17,18 Amnestic cognitive impairment stands as the principal clinical hallmark of AD, with early manifestations often presenting as disturbed sleep patterns, social withdrawal, anxiety and depression. With the progression of the disease, these symptoms intensify, giving rise to hallucinations, delusions and profound emotional and behavioural disturbances in more advanced stages. In contrast, patients with non-amnestic cognitive impairment may endure a diverse array of deficits, encompassing impairments in behaviour, language, visuospatial processing and motor functions, each of which contribute to the debilitating clinical profile of AD.^19–21 It is a sobering reality that no definitive cure for AD exists to date, with most patients receiving diagnosis only at advanced and irreversible stages, with the average remaining life expectancy reduced to merely 4 to 8 years.^22,23 Notably, the pathological alterations begin insidiously in the brain during the preclinical phase, often decades before the emergence of overt clinical symptoms. Typically, individuals progress to mild cognitive impairment within 6–10 years, with around 15% advancing to full blown AD within 2 years and nearly one-third within 5 years.^24,25 This underscores the critical importance of focusing on the preclinical and mild cognitive impairment stages, wherein early intervention and targeted management of modifiable risk factors may significantly delay the progression of AD or even mitigate the incidence of onset.²⁶

One of the major obstacles in the management of neurodegenerative disorders such as AD is the presence of a highly selective barrier called the blood–brain barrier (BBB).²⁷ The BBB is a selectively permeable membrane, which shields the brain from systemic circulation and in doing so safeguards it against foreign agents, infectious pathogens and toxic substances.²⁸ As per research findings, it has been estimated that the BBB is responsible for restricting the passive diffusion of all large molecules and over 98% of small molecules.²⁹ Histologically, it comprises a monolayer of tightly sealed endothelial cells, interconnected with tight junctions, adherens junctions, and gap junctions. These specialized intercellular structures collectively form the fundamental architecture of the BBB and restrict the paracellular permeability.³⁰ In addition to this, a complex array of receptors, transporters and enzymes are expressed by the cellular constituents of the BBB, which play a pivotal role in regulating the selective exchange of nutrients, metabolites and waste products, between the brain and the systemic circulation. There exist a variety of mechanisms in the brain that mediate this exchange, namely, paracellular and transcellular diffusion, cell mediated transcytosis, receptor mediated transcytosis, and adsorptive mediated transcytosis.³¹ This highlights the critical role of the BBB in maintaining the brain homeostasis by tightly regulating the exchange of both valuable and potentially harmful substances between the circulatory system and the brain parenchyma.^32,33

The development of drug delivery systems that can transport therapeutic agents across the BBB is an area of intense research in the treatment of neurodegenerative disorders. Recently, nanoparticle mediated drug delivery systems have emerged as potential therapeutic carriers that can facilitate penetration across the BBB.^4,34–36 In the majority of cases, the nanoparticulate drug delivery systems depend on ligands such as transferrin and apolipoprotein to cross the BBB through receptor mediated transcytosis.^35,37 However, the targeting efficiency and drug loading capacity of such nanocarriers are affected due to the attachment of bulky ligands on their surfaces, as a result of avidity and steric hinderance originating from the bulky ligands on the surface of nanoparticles.³⁷ In contrast to this, CDs are a novel class of carbon-based nanomaterials distinguished by their inherent self-targeting properties, in their ability to cross the BBB without the additional need of surface functionalization with targeting ligands.³⁸ Among other emerging nanotherapeutic strategies, CDs have emerged as the most promising vehicles to penetrate the BBB owing to their special characteristics. Their most important characteristic is their ultra-small sizes along with high biocompatibility and water solubility. They also present abundant functional groups that can be modified as per desire.^35,38,39 In addition to this, the precursors, synthetic approaches used and post-synthesis treatments employed also affect their BBB penetration capacity. It has been seen that CDs can cross the BBB with or without the cargo molecules.^40,41

As far as the effects of CD on the various pathologies of AD are concerned, CDs have been reported to act on multiple pathways such as inhibiting Aβ and tau pathologies. Reports have suggested that CDs also act on the cholinergic system and aid in promoting acetylcholine levels in the brain.⁴² Research in the last decade shows how CDs have emerged as promising nanoscale tools for neurological disorders, with growing evidence supporting their role in the management of neurodegenerative disorders. While several studies have explored their use across various neurodegenerative disorders, this review presents the focused synthesis of the literature on CDs in the context of AD exclusively. We critically examine how CDs have the potential to alter the course of disease by their ability to cross biological barriers and target multiple underlying pathologies, potentially modifying the disease trajectory. By integrating mechanistic insights, therapeutic applications and delivery strategies, this is an attempt to not only consolidate current knowledge but also highlight regulatory barriers and translational challenges that must be addressed to realize the full potential of CDs in AD therapy.

2. Key challenges in the management of AD

Currently, the only Food and Drug Administration (FDA) approved pharmacological agents for AD are the acetylcholinesterase inhibitors donepezil, rivastigmine, and galantamine and the N-methyl-D-aspartate (NMDA) receptor antagonist memantine. The first three agents aim to prevent the breakdown of acetylcholine, thereby enhancing cholinergic signalling, while the fourth agent, memantine, works to block the NMDA receptor, mitigating excitotoxicity. Unfortunately, the medical benefits of these treatments are deemed insufficient as these are purely symptomatic treatments wherein the aim is to either maintain the level of acetylcholine in the brain by acetylcholinesterase inhibitors or prevent excitotoxicity through blocking NMDA receptors. In addition, it is noteworthy that while the administration of acetylcholinesterase inhibitors enhances cholinergic neurotransmission and attenuates cognition decline, particularly in the first year of treatment, even temporary discontinuation may precipitate a rapid reduction in cholinergic levels and significantly increase the risk of institutionalisation.^43–45

As a result, one of the key challenges in the management of AD lies in the development of therapies capable of curing the disease or at least slowing disease progression. Attempts to confront the disease directly at the level of underlying pathophysiological mechanisms (Fig. 1) have long proven fruitless. Notably, efforts to target the defining pathological hallmark of AD, the Aβ accumulation, have repeatedly faltered in the crucible of clinical trials, yielding disappointing outcomes despite decades of intensive scientific pursuit. Between 2004 and 2021, no fewer than 14 different agents that directly target Aβ failed to demonstrate efficacy in the phase III of clinical trials. Yet, in recent years, a glimmer of progress has begun to emerge. After decades of stagnation, therapeutic approaches that harness monoclonal antibodies to actively clear Aβ have started to show promise. In 2021, three anti-amyloid agents received regulatory approval in the United States for treating AD. However, the narrative has not unfolded without controversy. The first amongst these, aducanumab, became the centre of considerable scientific and regulatory debate and has thus been withdrawn due to safety concerns; however, the trials published in 2022 and 2023 clearly depict that lecanemab and donanemab are slowing cognitive decline, marking a potential inflection point in the trajectory of AD therapeutics. Yet, it is important to mention that these two agents are not without their adverse effects, which are occasionally serious, with people developing brain swelling and bleeding. While often asymptomatic, approximately one quarter of individuals experience symptoms such as headaches, dizziness and confusion. Although seizures and fatalities are rare, they have been reported. Brain bleeds are believed to result from antibodies binding to Aβ in cerebral blood vessels, while the swelling is attributed to the neuroinflammatory processes. Many researchers posit that these drugs exert their effects by triggering an inflammatory response in the brain wherein the microglia adopt a proinflammatory phenotype and phagocytose plaques. This mechanism is unfortunate as it blurs the line between the benefits and the side effects. Reducing these side effects remains a critical and ongoing challenge and despite this progress, significant contention remains. The therapeutic benefits of these agents are modest, fuelling ongoing debate regarding the justification of their costs and potential adverse effects. While some in the scientific community regard these developments as a promising starting point that paves the way to improved efficacy in the management of disease, the others remain sceptical, questioning whether Aβ clearance alone is sufficient to arrest disease progression, and are advocating for the exploration of alternative effective targets. The reported benefits of these new treatment strategies can thus be considered promising but should be taken with a pinch of salt until larger, independent trials confirm the findings.^46–48

Fig. 1 Schematic representation of the multifactorial pathological mechanisms underlying AD. The central nervous system is impacted by interconnected pathways involving amyloid-β aggregation, tau hyperphosphorylation, neuroinflammation, oxidative stress (ROS), impaired autophagy, cholinergic dysfunction, microbiota gut–brain axis (MGBA) dysregulation, and glutamate excitotoxicity. Each of these pathways contributes to synaptic dysfunction and neuronal degeneration, collectively driving disease progression.

The limited efficacy of conventional therapeutic approaches along with the high attrition rates in clinical drug development either due to adverse effects or insufficient efficacy underscores the urgent need for the development of next generation therapeutics for AD. These emerging interventions aim to facilitate precise and diverse treatment approaches, specifically tailored to individual patients with distinct pathological trajectories. Although recent advances in our understanding of pathological processes along with the emerging drug development technologies have led to the discovery of promising novel molecules, their translation from bench to bedside remains largely unrealised.⁴⁹

It is imperative to decipher the interplay between Aβ accumulation, tau deposition and neuroinflammation so that potential therapeutic strategies can be developed for AD. Targeting neuroinflammation and its interactions with Aβ and tau may hold promise for future treatment but further research is elicited.⁵⁰ Given the poorly understood underlying mechanisms along with intricate and etiologically diverse nature of AD, numerous therapeutic agents initially envisioned to alter the disease progression have ultimately failed in clinical trials. These repeated setbacks have raised questions and fuelled growing doubts among researchers and within the pharmaceutical industry. This continued lack of effective disease modifying therapies may dissuade individuals from seeking early diagnosis, as many may perceive little value in receiving a diagnosis in the absence of meaningful treatment options.⁵¹

3. The blood–brain barrier: a critical obstacle

The BBB is a highly selective membrane that separates circulating blood from the extracellular fluid present in the brain. It plays a vital role in maintaining central nervous system (CNS) homeostasis, functioning not merely as a passive shield but as an active, selective interface.²⁷ This unique barrier comprises the endothelial cells, pericytes, astrocytes, and tight junctions. It protects the brain from toxins and pathogens while regulating nutrient transport.^52–54 The neurovascular unit forms the foundational structure of the BBB, consisting primarily of capillary endothelial cells, astrocytes, pericytes, neurons, and tight junctions that collectively regulate brain access. Among these, the endothelial cells play the most critical role in maintaining BBB integrity. The BBB acts as a selective filter, allowing certain substances like oxygen, carbon dioxide, some anaesthetics, and fat-soluble compounds to pass through with ease, while blocking others such as penicillin, hydrogen ions, and bicarbonate, which are poorly permeable due to their physicochemical properties.⁵⁵ The barrier comprises tight junction proteins like claudins and occludins that restrict paracellular leakage, while the specialized transport systems such as GLUT1 regulate the nutrient uptake.⁵³ Efflux pumps, mainly P-glycoprotein, act as a vigilant gatekeeper by expelling unwanted substances from the brain, including nearly 98 percent of the actives. This protective mechanism significantly limits the ability of molecules to cross the BBB and enter the brain. For instance, in a healthy brain, insulin can easily pass through the BBB, whereas Aβ is largely hindered from entering.⁵⁶ BBB dysfunction is now recognized as a hallmark across several neurodegenerative conditions. In neurodegenerative diseases like Alzheimer's, Parkinson's, and amyotrophic lateral sclerosis, this barrier becomes dysfunctional, contributing to the progression of disease while also hindering drug delivery.^57–59 In AD, this tightly regulated barrier collapses, which further worsens the disease condition. Multiple evidence of a compromised barrier is reflected by elevated levels of plasma proteins such as fibrinogen and albumin in cerebrospinal fluid, indicating leakage.⁶⁰ In addition to these features, the diminished activity of the LRP1 transporter hampers Aβ clearance, while neuroinflammation driven by microglia and pro-inflammatory cytokines (like IL-6 and TNF-α) also exacerbates barrier damage.^61–63 The consequences of BBB breakdown are profound. When plasma components like thrombin infiltrate the brain, they can trigger inflammation and neuronal damage. This leakage and exclusion mechanism creates a feedback loop, accelerating neurodegeneration.

The ability of a substance to cross the BBB is not determined solely by its molecular weight. Like, glucose and amino acids, despite being relatively large (glucose ∼180 Da), can cross the BBB efficiently due to the presence of specific transport mechanisms. In contrast, smaller molecules like many ions often face difficulty penetrating the barrier without dedicated transporters.⁵⁵ The BBB plays a crucial role in preserving the internal environment of brain, shielding it from harmful entities such as toxins, pathogens, and immune system components. It is important to note that not every substance that crosses the BBB under such conditions is necessarily harmful, some may be therapeutic or inert.⁵²

Clinical imaging studies have shown that BBB leakage in AD patients is related to faster cognitive decline.⁶⁴ To overcome the challenges of BBB permeation, several strategies are being explored. Pharmacological approaches include modifying drugs to increase lipophilicity, thereby enhancing passive diffusion, or using P-glycoprotein inhibitors like elacridar to improve drug retention in the brain.^65–67 Antibody–drug conjugates targeting BBB receptors, such as those against transferrin, represent another tactic, although only a small fraction (2–5%) of such drugs effectively reach brain tissue. Physical methods such as focused ultrasound, especially when combined with microbubbles, can temporarily open the BBB and have shown promising results. For example, focused ultrasound-assisted delivery of aducanumab led to a 32% reduction in Aβ plaques in early-stage AD patients.⁶⁸

Liposomes, especially those modified with polyethylene glycol, have shown improved circulation times and have been employed to deliver drugs like rivastigmine in AD.⁶⁹ Looking ahead, the future of BBB-targeted therapy in neurodegeneration appears promising. Personalized approaches based on biomarkers like the cerebrospinal fluid/serum albumin ratio may help predict barrier integrity and inform treatment choices.⁷⁰ Advances in gene editing, particularly CRISPR-modified endothelial cells, may offer pathways to restore BBB function at the molecular level. Additionally, the gut–brain axis is also being explored, with gut-derived metabolites such as short-chain fatty acids playing potential roles in maintaining BBB stability.⁷¹ A particularly promising avenue lies in modulating the Wnt/β-catenin signaling pathway, a key regulator of BBB repair and maintenance.⁷² The BBB serves as both a gatekeeper and a major hurdle in treating AD. While its dysfunction contributes to disease progression, it also presents a unique therapeutic opportunity. Emerging technologies ranging from nanocarriers to precision ultrasound are beginning to breach this formidable barrier, offering renewed hope in the drug delivery. The research must focus on striking a delicate balance between repairing BBB integrity and enabling effective drug delivery to halt neurodegeneration at its source.

4. CDs: properties and potential

Carbon based materials have long stood at the forefront of materials science; be it the age old industrial carbon or the new industrial carbon, or even the revolutionary emergence of carbon nanomaterials such as graphene, carbon nanotubes and CDs, the allure of carbon remains undiminished.^73,74 The fundamental research on carbon-based materials has always been a hot topic due to their environmental friendliness. Among these, CDs have emerged as a remarkable new protagonist in the carbon family, capturing considerable attention for a multitude of reasons. Being known for their small size, exceptional biocompatibility, economic synthesis, low toxicity and tunable photoluminescence, CDs are rapidly asserting themselves as a multifunctional powerhouse across various domains such as biomedicine, catalysis and optoelectronic devices. This ascent not only signals merely a trend but also a transformative leap in nanoscience.^75,76

CDs can be loosely defined as quasi zero-dimensional carbon-based materials, typically measuring less than 20 nm, which are distinguished by their intrinsic property of fluorescence. It was this fluorescence that led to their serendipitous discovery in 2004 during electrophoretic purification of single walled carbon nanotubes.¹ For nearly two years they remained obsolete, until brought to light by Sun and coworkers in 2006, who formally named them as CDs for the first time, prepared by laser ablation of carbon targets.² Modifying their surfaces with simple organic species such as diamine terminated oligomeric poly(ethylene glycol) was the first reported example of a post-functionalization reaction. Another breakthrough happened in 2008 with the synthesis of small and fluorescent carbogenic nanoparticles through thermal decomposition of organic precursors, such as citrate salts.⁷⁷ Presently, CDs are broadly categorized into graphene quantum dots, carbon quantum dots, and carbonized polymer dots, each defined by their unique formation mechanisms, internal micro/nanostructures and physicochemical properties (Fig. 2). Nevertheless, a continuum exists amongst these classes, as variations in the carbonization degree and graphene layering enable their structural and functional modification.⁷⁸ Graphene quantum dots are distinguished by their single or multi-layered graphitic structures, featuring chemically functionalised groups located on the surface, edges or within the interlayer defects.^79,80 They are composed of graphene lattices and are typically prepared by top-down approaches such as oxidative cutting of larger graphitized carbon materials including carbon rods, carbon nanotubes, graphite powder, carbon fibres, graphene oxide or carbon black, into smaller pieces.^81,82 They are generally anisotropic with lateral dimensions exceeding the vertical thickness, in contrast to carbon quantum dots or carbon polymer dots which are typically spherical and often produced by bottom-up methods such as combustion or thermal treatment. The carbon quantum dots exhibit multilayered graphite structures functionalized with surface groups, while carbon polymer dots are characterised by aggregated or cross-linked carbonized polymer hybrid nanostructures. They have spherical core shell architectures composed of carbon cores less than 20 nm in diameter with highly dehydrated crosslinking polymer frames. This structural configuration imparts enhanced stability, biocompatibility, and ease of functionalization, enabling use in a wide range of applications.^83,84 CDs, in particular, have emerged as versatile agents with potential in both therapeutic and diagnostic applications across various diseases. These zero-dimensional carbon nanomaterials emit strong fluorescence rendering them highly suitable for multifaceted applications such as targeted drug delivery, immunomodulation, photothermal and photodynamic therapy and gene therapy.^85–88 They are also excellent drug carriers owing to their ability to encapsulate or adsorb therapeutic molecules within cavities while their surface chemistry offers ample scope for functionalization, further augmenting their therapeutic potential.^89,90

Fig. 2 Schematic illustration of the classification and synthesis strategies of CDs. CDs are broadly categorized into graphene quantum dots, carbon quantum dots, and carbonized polymer dots. They can be synthesized via two main approaches: (1) the top-down approach, which involves breaking down bulk carbonaceous materials such as graphite, carbon nanotubes, or rods through oxidative or mechanical processes, and (2) the bottom-up approach, which relies on carbonization, polymerization, or thermal decomposition of small molecules, polymers, or natural biomass precursors.

Specifically speaking, “carbon dots” may be considered a generic term used for nanosized photoluminescent carbon nanomaterials with a quasi-spherical morphology. CDs are nano-carbon materials that exhibit quantum confinement characteristics. Such particles are known to mimic the optical characteristics of semiconductors and exhibit great potential in biological imaging and sensing applications. These structures are based on a layered structure similar to graphite and exhibit a high level of organization.^91,92

There are two principal synthetic approaches for the preparation of CDs namely, top-down and bottom-up methods. The top-down strategy employs carbon rich precursors such as graphite, whereas the latter uses organic monomers or polymers as the starting materials. Historically speaking the top-down strategy was first exploited and comprised of chemical and electrochemical oxidation of graphite.⁹³ Such approaches yield comparatively larger quantities of CDs as high voltages are applied and chemical oxidants are used, along with long synthetic times and still need post synthetic procedures to tune the optoelectronic properties. As far as the fluorescence properties are concerned, the oxidative cutting of carbon sources leads to more structural defects, resulting in less appealing photoluminescence properties. Conversely, bottom-up synthesis is more versatile, with a variety of molecular precursors available along with benefits of multiple choices of thermal treatments, quicker reaction times and more uniform and tailored properties of the resulting materials. The pre-synthetic control in terms of precursors and synthetic procedures affects the physicochemical properties of CDs in terms of size, graphitization, degree, surface functional groups and doping. Nevertheless, some of the structural features of the precursors can be retained in the nanoparticles, which allows for some degree of predictability. Single component and multicomponent reactions enable the use of doping in CDs with the most common doping heteroatoms being boron, nitrogen, sulphur, selenium and their combination. In addition to the pre-synthetic control, engineering the surface composition via post-synthetic approaches is a promising way to optimize and expand the utilization of CDs. Post-synthetic strategies usually affect the surface functional groups of the CDs as they are generally inefficient in changing the properties and chemical composition of the core. Exploiting their surface chemistry has also prompted the development of multifunctional CD based materials.⁹⁴

CDs have widespread application in various fields, be it energy applications in catalysis, light emitting diodes, solar cells, supercapacitors or rechargeable batteries, or optical applications as sensors. However, their biomedical applications have captured particular scientific intrigue, revealing their promise in bioimaging, phototherapy, drug/gene delivery and nanomedicine.⁹⁵ The specific interest here lies in the emerging role of CDs in therapeutic management of AD. CDs are being ingeniously integrated into image guided nanoplatforms that unite diagnostic and therapeutic functionalities, aiding an improvement in therapeutic efficiency. The overarching goal of drug delivery is that drugs are delivered at a precise location and a sustained release of the therapeutic agents is achieved. CDs by virtue of their intrinsic fluorescence offer a distinct advantage by not only delivering the therapeutic cargo at the target site but also enabling visualization of the drug accumulation, thus providing an estimate of the therapeutic efficacy of the nanosystems.^96–100 Apart from this, CDs are also being used for the gene therapy, which is emerging as a durable and potentially curative clinical strategy for various diseases. Their physicochemical properties such as low toxicity, abundant functional groups, excellent biocompatibility and ultra-small size make them ideal vectors for gene transfection. These attributes facilitate efficient cellular uptake of vectors, enhancing gene transfection efficiency, while their unique fluorescent properties enable tracking of gene internalization and intracellular trafficking.^101,102

This brings us to the pivotal question of how CDs contribute to efficient delivery of therapeutic agents. Owing to their small size, tunable surface chemistry, polymeric or graphitic core architecture and various functional groups on the surface, CDs exhibit excellent active and passive targeting capabilities. Their abundant surface functional groups such as amines, hydroxyls and carboxyl groups promote the delivery of drugs through carrier mediated transport across biological barriers.^103–105 Moreover, CDs can be engineered to carry both hydrophilic and hydrophobic therapeutic payloads, ensuring high loading capacity and stimulus responsive release profiles.¹⁰⁶ The next fundamental question is how CDs interfere with the pathologies of complex neurodegenerative diseases like AD. Emerging evidence shows that CDs can directly bind to misfolded or aggregation prone proteins such as Aβ and tau, interfering with their fibrillation and promoting disaggregation, largely through hydrogen bonding, π–π stacking, and hydrophobic interactions.³⁵ Furthermore, the electron donating functional groups on their surface enables CDs to act as potent reactive oxygen species (ROS) scavengers, neutralizing species like superoxide anions and hydroxyl radicals, which are central to oxidative stress in AD.^107,108 This dual ability to interfere with pathological protein aggregation and mitigate oxidative stress positions CDs as multifunctional nanotherapeutics for modifying disease progression in AD.

5. Targeting Alzheimer's pathophysiology with CDs

CDs have recently emerged as promising nanomaterials capable of interfering with key pathophysiological mechanisms in AD. Numerous studies have demonstrated the potential of CDs to inhibit the self-assembly of neurotoxic Aβ peptides, a hallmark of AD pathology.¹⁰⁹ These interactions often arise from hydrogen bonding, π–π stacking and hydrophobic interactions between CDs and Aβ monomers or oligomers, disrupting fibrillogenic deposits, thus reducing downstream toxicity. In addition to this, research has started to explore the effect of CDs on tau pathology, with preliminary evidence indicating that CDs have the potential to interact with tau deposition delaying tau fibril formation and modulating secondary nucleation processes.¹¹⁰ Beyond their anti-aggregation properties, CDs have been mainly reported for their inhibition of ROS generation, highlighting their anti-oxidant potential, which is an especially relevant feature given the oxidative stress burden in AD. Additionally, a few investigations have indicated that CDs can interfere with β-site amyloid precursor protein cleaving enzyme 1 (BACE1) activity, potentially reducing Aβ production at its enzymatic origin.¹¹¹ CDs have also been utilized in photodynamic and photothermal strategies, where light triggered ROS generation or local hyperthermia is leveraged to ablate pathological protein aggregates or modulate the brain microenvironment.¹¹² Despite these promising results, many of these studies are still in their infancy and rely heavily on in vitro or zebrafish models. This section explores these findings in greater depth, delineating how CDs interact with Aβ and tau aggregation, oxidative stress and enzymatic dysregulation, and also critically examines the limitations and translational hurdles that persist.

5.1. CDs overcoming the BBB

Several approaches have leveraged the strategy of exploiting endogenous precursors, which are already required in the brain and thus cross the BBB through specific receptors, to facilitate the transport of CDs across the BBB. In a notable example, Mintz et al. used tryptophan as the carbon precursor with two primary aims, first, to enhance the quantum yield of CDs given the intrinsic fluorescence of tryptophan and second, to enable BBB penetration by utilizing the natural transport pathway for tryptophan. This amino acid is essential for brain function and is transported across the BBB through a specialized transport system referred to as the large neutral amino acid transporter 1 (LAT1), which is composed of the glycoprotein CD98. To capitalize on this mechanism, they synthesized CDs with tryptophan and established through UV-visible and X-ray photoelectron spectroscopy that the tryptophan moieties retained on the surface, thereby allowing the nanoparticles to engage in the LAT1 mediated translocation, eliminating the need for additional conjugation strategies, which are often hampered by low yield reactions. The resulting CDs were injected intravascularly in the heart of transgenic zebrafish in order to examine the ability of CDs to cross the BBB. Successful BBB penetration was observed owing to the abundant tryptophan molecules on the surface. The findings suggest that LAT1 recognizes the surface amino acid and facilitates the translocation of the whole CD system across the BBB into the CNS.¹¹³

Similarly, glucose derived CDs have been shown to involve glucose transporter 1 (GLUT1) mediated transport wherein glucose derived CDs were evaluated for crossing the BBB to deliver a small cargo to the CNS.³⁸ The glucose CDs synthesized through a green hydrothermal route and surface labelled with fluorescein for in vivo tracking were revealed to accumulate in the CNS of both zebrafish and rats, with particular localization in the neuronal regions of the spinal cord and brainstem. This underscores their capacity for a non-invasive and ligand free nanocarrier for targeted delivery in the CNS. However, transitional relevance of this study remains limited by the lack of mechanistic validation in mammalian models such as GLUT1 inhibition or knockout models.

Apart from these ligand free approaches, researchers have also investigated exogenous ligand conjugation strategies utilizing transferrin functionalized CDs to cross the BBB through transferrin receptor mediated transcytosis, in a zebrafish model.¹⁰⁴ CDs were synthesized and covalently functionalized with human transferrin and fluorescein. While the plain CDs and only dye labelled CDs did not cross the BBB and localize in the zebrafish CNS, transferrin conjugated CDs readily crossed the BBB exhibiting distinct fluorescence in the central canal and surrounding neuronal structures, confirming the CNS entry. This crossing can be attributed to transferrin receptor mediated transcytosis, leveraging the receptor's expression in BBB.

A more advanced transferrin-based system developed by Han et al. demonstrated not only BBB penetration but also multifunctional action against AD pathology, including inhibition of amyloid fibril formation, BACE1 enzymatic activity, and downstream Aβ toxicity.¹¹¹ The transferrin conjugated CD definitively crossed the BBB in zebrafish and preferentially localized in the forebrain. Acting on the amyloid hypothesis, the nano-system inhibited amyloid fibrillation in vitro and reduced Aβ induced cytotoxicity in sea urchin embryo models. They also reported that the system suppressed BACE1 enzyme activity, which is key for Aβ generation. Mechanistic studies using thioflavin T fluorescence and circular dichroism spectroscopy, atomic force microscopy and molecular dynamics simulations revealed that CDs interact with Aβ secondary structure transitions and redirect aggregation by binding early to Aβ monomers, particularly via hydrophilic surface interactions. The system effectively combined BBB penetration with dual inhibition of AD pathology by targeting BACE1 mediated Aβ production and fibril formation, though its validation remains limited to cell based and zebrafish models. Notably, while the studies successfully employed receptor mediated transcytosis for BBB crossing, it also revealed that unconjugated CDs lacked intrinsic permeability, emphasizing the necessity of ligand functionalization in this context. These findings thus highlight two divergent strategies, one relying on endogenous transporter recognition and the other on exogenous ligand attachment, warranting further validation in mammalian models to assess quantitative CNS distribution and translational potential.

Apart from exploiting ligand-mediated entry across the BBB, researchers have also utilized the amphiphilic nature of CDs to mediate passive diffusion of nanosystems across the BBB.¹¹⁴ Zhou and colleagues developed novel amphiphilic yellow emissive CDs from citric acid and o-phenylenediamine via an ultrasonication based green synthesis approach. These CDs demonstrated excitation-independent photoluminescence, strong water dispersibility, and low cytotoxicity across multiple cell lines. They utilized zebrafish as an in vivo model to demonstrate that the nanosystem successfully crossed the BBB and localized in the spinal cord. These CDs also attenuated Alzheimer's pathology by downregulating amyloid precursor protein expression and reducing Aβ secretion in cells overexpressing human APP751. While the study shows strong therapeutic promise in AD, it relies solely on cell based and zebrafish models; in vivo mammalian validation and mechanistic studies are further needed to support clinical relevance.

In a more recent study the researchers developed nitrogen and fluoride functionalized CDs via microwave assisted synthesis using citric acid and highlighted their potential in diagnostic and drug delivery platforms for Alzheimer's disease.¹¹⁵ The CDs were synthesized using citric acid, urea and sodium fluoride and demonstrated a high quantum yield, strong photostability and excellent biocompatibility in endothelial cells modelling the BBB. They used a neuromimetic transwell based in vitro BBB model to demonstrate the significant permeability of the nanosystem. This permeation may be attributed to their small size, surface functionalization, notably with fluorine, and high colloidal stability likely facilitating paracellular or transcellular passage. Again, the lack of in vivo data limits the translational insight along with the proposed role of fluoride in enhancing permeability, remaining speculative without mechanistic validation. Similarly, nitrogen doped CDs were synthesized using a one pot hydrothermal process of citric acid and polyethyleneimine yielding monodispersed, positively charged and strongly fluorescent nanodots with excellent photostability, negligible cytotoxicity and capable of real time live cell imaging.¹¹⁶ The BBB permeability was demonstrated using a biomimetic in vitro co culture model using astrocytes and rat brain endothelial cells, where fluorescence-based quantification revealed concentration and time dependent translocation across the BBB, attributed to their ultra small size and cationic surface charge, enabling penetration across tight junctions of the BBB.

Beyond delivery, drug loaded CD systems have also been investigated. Gomez et al. developed nitrogen doped graphene quantum dots conjugated with memantine, an NMDA receptor antagonist, and demonstrated effective BBB penetration using a 3D in vitro model.¹¹⁷ The nano-system was found to retain the pharmacological activity of memantine and was found to be capable of regulating NMDA receptor mediated calcium influx in astrocytes. They used a three-dimensional in vitro BBB model to demonstrate the efficient BBB penetration confirming that ATP-binding cassette transporters did not significantly hinder permeability suggesting that the nanosystem avoided common efflux limitations and may have crossed via passive diffusion or endocytosis. This distinguishes them from many conventional nanoparticles that are restricted by efflux mechanisms. They also reported inhibition of Aβ fibrillation through atomic force microscopy studies and supported confocal bioimaging. However, in vivo studies are necessary to confirm CNS distribution and therapeutic outcomes.

Expanding on nutrient based strategies, another study focusing on the transporter mediated entry routes in the brain used glucose tryptophan based CDs with dual visible and near infrared fluorescence to overcome BBB limitations in brain disorders including AD.¹¹⁸ They used D-glucose and L-tryptophan to exploit transporter mediated entry into the brain and validated this in both zebrafish and mice in vivo. The nanosystem showed significant accumulation in brain, particularly in the hindbrain and the midbrain, which are the regions implicated in the AD pathology, and also demonstrated strong bioimaging capacity, including near infrared imaging for deep tissue visualization. They used doxorubicin as a model drug to deliver it across the BBB, confirming the drug carrying capability of CDs. Nonetheless, mechanistic confirmation of transporter specificity remains preliminary.

Collectively, these studies demonstrate that CDs can cross the BBB via diverse mechanisms including carrier mediated transport, receptor mediated transcytosis, passive diffusion and charge-based interactions, each offering distinct advantages and limitations (Fig. 3). However, a common thread among current investigations is the reliance on zebrafish and in vitro models, with a notable scarcity of mammalian validation. Comprehensive biodistribution, transporter blocking assays, and pharmacokinetic profiling in rodents or higher orders systems remain essential for clinical translation. Furthermore, while several systems demonstrate co-localization in brain tissue, quantitative drug delivery efficiency and functional therapeutic outcomes in AD specific models are rarely addressed. Bridging this gap will be critical for leveraging CDs in next generation Alzheimer's nanotherapeutics.

Fig. 3 Illustration of the various mechanisms by which CDs traverse the BBB. CDs can exploit multiple pathways including, (1) carrier-mediated transport, by mimicking endogenous substrates such as tryptophan (LAT1) and glucose (GLUT1), (2) endocytosis, via vesicle-mediated internalization by endothelial cells, (3) passive diffusion, enabled by their ultrasmall size and lipophilic or amphiphilic nature, (4) receptor-mediated transcytosis, through ligand interactions with surface receptors like transferrin receptors, and (5) charge-based penetration, using cationic surfaces to transiently disrupt tight junctions. These diverse entry routes enable CDs to effectively accumulate in the brain and interface with resident neural cells.

5.2. CDs targeting amyloid beta burden

Aβ aggregation and plaque formation remain central to the pathogenesis of AD, initiating a cascade of neurotoxic events that include synaptic dysfunction, tau hyperphosphorylation, neuroinflammation and oxidative stress.^119–121 Despite decades of investigation, clinical attempts to inhibit Aβ production or aggregation have been hindered by the inability to deliver therapeutic agents effectively across the BBB and the complex multifactorial nature of Aβ toxicity. The small size of CDs facilitates them to efficiently cross the BBB and accumulate in the CNS. A growing body of research has demonstrated that CDs can disrupt Aβ fibrillation by interacting with monomers and oligomers by virtue of their chemical functionalities, such as amino and nitro groups, pyrrole and pyrimidine rings and aromatic systems. CDs are able to interact with Aβ species through electrostatic forces, hydrogen bonding and hydrophobic interactions, thus efficiently disrupting Aβ aggregation. These interactions lead to altered aggregation pathways and suppression of β-sheet formation.^110,122

However, the precise molecular mechanisms governing these interactions remain to be fully elucidated. CDs are believed to interact with Aβ peptides through a concerted interplay of hydrogen bonding, π–π stacking, electrostatic and hydrophobic forces mediated by heteroatom rich surface groups.^123–126 Molecular dynamics simulations provide a powerful means to probe these interactions at the atomic resolution, enabling the identification of key binding residues, visualization of Aβ-CD complexes and evaluation of conformational stability during fibrillation. Yet, only a few studies combine molecular dynamics simulations with in vitro an in vivo binding data. For instance, Xiuhua et al. (2023) combined all-atom molecular dynamics simulations with in vitro and in vivo assays to demonstrate that ultra-small C₃N nanodot surfaces bind to Aβ peptides, perturb β-sheet formation and reduce fibrillization and plaque burden in murine models, revealing that the molecular dynamics identified binding sites and inhibitory mechanisms.¹²⁷ Most other investigations rely predominantly on biophysical assays to validate CDs and peptide interactions, including thioflavin-T fluorescence and displacement/aggregation assays and imaging, including circular dichroism spectroscopy, atomic force microscopy, and transmission electron microscopy. Thioflavin-T fluorescence assays, which quantify β-sheet-rich fibril formation by monitoring enhanced emission upon dye binding to amyloid structures, remain the most widely used for evaluating anti-aggregation efficacy.¹²⁸ Circular dichroism spectroscopy provides insight into secondary-structure transitions,¹²⁹ while atomic force microscopy and transmission electron microscopy offer direct visualisation of morphological changes or fibril disassembly following CD exposure.^130,131 Complementary protein-binding assays, such as surface plasmon resonance and isothermal titration calorimetry, quantitatively determine binding affinities, kinetics, and thermodynamic parameters, thereby experimentally validating computational predictions.¹³² Integrating these computational and experimental methodologies, including molecular dynamics simulations, protein-binding studies, and advanced spectroscopic and microscopic analyses, will be crucial to delineate the molecular basis of Aβ–CD interactions within complex brain environments and to guide the rational design of next-generation, clinically translatable nanotherapeutics.

Recent reports have applied these approaches to characterise and validate the inhibitory effects of CDs on Aβ aggregation and associated neurotoxicity. In an attempt to integrate the anti-aggregation and anti-oxidant capabilities of CDs, Yang et al. synthesized cerium doped CDs through a one pot hydrothermal method. These cerium doped CDs not only demonstrated excellent BBB permeability but also demonstrated potent dual functionality, scavenging ROS and suppressing Aβ induced oxidative damage. The in vivo studies using transgenic Caenorhabditis elegans further consolidated their bifunctional efficacy in suppressing Aβ pathology and mitigating ROS, thus emphasizing the role of multifunctional nanomaterials in advancing AD treatment.¹³³ Similarly, Ye and team utilized a novel biomimetic therapeutic strategy using nitrogen doped CDs. They engineered a macrophage membrane coated CD system enriched with copper ions and equipped for near infrared photothermal activation, with the capability of mimicking immune cells, thus evading immune surveillance and target inflamed brain regions, where it inhibited copper ions and acted on Aβ by inhibiting copper induced Aβ aggregation. In addition to this, they also utilized the photothermal properties of CDs allowing near infrared radiation to generate localized hyperthermia to temporarily increase BBB permeability and disassemble mature Aβ fibrils. The in vivo investigation in APP/PS1 transgenic mice revealed reduced Aβ burden, decreased neuroinflammation and improved cognitive function.¹³⁴

The interplay between microbial function and Aβ aggregation is gaining increasing attention. Emerging research suggests that certain pathogenic microorganisms particularly fungi may play a role in the development of AD influencing Aβ aggregation. Notably, Candida albicans has been shown to cross the BBB, induce localized brain inflammation and trigger the accumulation of activated glial cells and Aβ deposits around fungal colonies. These findings imply a potential link between the severity of fungal infections and the extent of amyloid fibrillation.^135–137 In a unique study to simultaneously target fungal pathogens and Aβ aggregation, Yan and coworkers developed dual targeted glycosylated CDs with epigallocatechin gallate, a flavonoid that effectively inhibits Aβ fibrillation. The nanosystem disassembled existing fibrils, reduced cytotoxicity and suppressed fungal biofilm formation, preventing memory loss caused by fungal infection. The system demonstrated excellent biocompatibility, BBB permeability and therapeutic efficacy in APP/PS1 transgenic mice, cleaning Aβ deposition and improving memory impairment.¹³⁸

Ferulic acid modified L-glutamate derived CDs were prepared and the formed nanosystem simultaneously penetrated the BBB, inhibited Aβ aggregation, disassembled preformed Aβ plaques and scavenged ROS. While ferulic acid alone tends to promote Aβ aggregation, its conjugation on CDs reversed these effects interestingly. In vitro studies demonstrated that the nanosystem significantly suppressed the Aβ42 fibrillation, degraded mature fibrils, attenuated ROS and proinflammatory cytokine production in neuronal and microglial cells. Mechanistic studies revealed strong Aβ binding, improved cell viability and restored redox balance. High BBB transport efficiency was confirmed through transwell models and in vivo imaging, excellent biosafety and no systemic toxicity. In vivo studies in APP/PS1 mice restored memory and cognition through Morris water maze, reduced hippocampal Aβ burden, decreased neuroinflammation and preserved neuronal morphology.¹³⁹ This study offered a multitarget nanoplatform that resolves the contradictory role of ferulic acid in amyloid pathology through rational nanoengineering.

Quercetin is a flavonoid known for its anti-oxidant, anti-inflammatory and neuroprotective properties, but researchers have long grappled with its poor water solubility and limited bioavailability, both major barriers to clinical applications.¹⁴⁰ Addressing this gap, Sun and coworkers synthesized multifunctional CDs using quercetin as the carbon source and p-phenylenediamine as the nitrogen dopant to produce red fluorescent CDs via a one step hydrothermal process. The developed system exhibited strong inhibition of Aβ aggregation and rapid depolymerization of mature fibrils. The red fluorescence of these CDs enabled red fluorescence imaging of Aβ plaques and also demonstrated significant ROS scavenging capability and in vivo studies prolonged the lifespan of Alzheimer's model nematodes by over 50%. They also reported that the key functional moieties from the parent compound were retained such as aromatic rings, phenolics, hydroxyls and amino groups, facilitating amyloid binding with Aβ species through hydrogen bonding, electrostatic and hydrophobic interactions.¹²³

CDs designed for synergy between anti-amyloid, antioxidant and metal chelating properties are also being increasingly explored. Shao et al. reported the synthesis of selenium doped carbonized polymer dots as a versatile nanoplatform targeting the interconnected pathologies of AD. They used glutathione, rich in sulfhydryl groups, and a key antioxidant tripeptide along with selenomethionine, a selenium source with known antioxidant and metal chelating properties, to synthesize selenium CDs via a straightforward carbonization route. They inhibited Aβ aggregation and scavenged ROS such as hydroxyl and superoxide anion radicals along with chelation of copper ions, mitigating Aβ copper complex mediated toxicity. Intracellular ROS levels were reduced, suggesting strong neuroprotective potential.¹⁴¹

Similarly, guanidine-functionalized CDs and epigallocatechin gallate-derived carbonized polymer dots demonstrated rapid fibril disassembly, ROS suppression, and in vivo neuroprotection in Caenorhabditis elegans and murine models. In addition to this, in an in vivo model using transgenic mice, excellent biocompatibility and brain retention were observed along with improving cognitive function. They reported an enhanced protein affinity and prolonged BBB residence. The epigallocatechin gallate-derived nanosystem rapidly disaggregated Aβ fibrils within seconds, scavenging intracellular ROS levels and acting as fluorescent probes for amyloid detection. This mechanism was attributed to the surface catechol, hydroxyl and carboxyl groups, which facilitate interaction with Aβ via hydrogen bonding, electrostatic, and hydrophobic effects. In vitro assays reduced Aβ induced cytotoxicity significantly. In an in vivo Caenorhabditis elegans model, they extended lifespan and mitigated Aβ plaques visualized through fluorescence imaging. Compared to free epigallocatechin gallate and free CDs they markedly enhanced anti-amyloid effects and displayed antioxidant activities.¹⁴²

Several studies show the anti-amyloidogenic potential of carbon quantum dots. Yan et al. developed red emissive carbon quantum dots that strongly inhibited Aβ with strong binding affinity to Aβ42 species and showed potent inhibition and disaggregation efficiencies as confirmed by thioflavin T and transmission electron microscopy assays. These interactions were inferred to be mediated through π–π stacking, hydrogen bonding and electrostatic interactions. Additionally, they also demonstrated excellent BBB permeability in both in vitro and in vivo models along with significantly attenuating ROS levels in a dose dependent manner.¹⁴³ Similarly, Li and team worked on the fabrication of ultrasmall carbon quantum dots using a two-step pulsed laser ablation method, yielding homogenously dispersed nanoparticles. Thioflavin T fluorescence assay depicted a concertation dependent inhibition of Aβ42 fibrillation and this study was further supported by transmission electron microscopy, showing a marked reduction in fibril length and density upon co-incubation with the carbon quantum dots. Circular dichroism spectroscopy revealed a transition of the Aβ42 secondary structure from β sheet rich confirmations to random coils or amorphous aggregates in the presence of carbon quantum dots. In addition to this, tyrosine fluorescence quenching and red shifting further consolidated the direct interactions between the Aβ42 peptide and the carbon quantum dots. To test these findings in an in vivo model, transgenic strain of Caenorhabditis elegans CL2006 expressing Aβ42 in the muscle tissue was utilized. Thioflavin T staining demonstrated a significant reduction in the Aβ deposits following administration of carbon quantum dots, with significant improvements in motility and survival highlighting the neuroprotective effect of carbon quantum dots.¹⁴⁴

Zhang et al. synthesized metformin-derived CDs using a hydrothermal method with metformin and citric acid, aiming to enhance neurogenesis and provide neuroprotection in AD through a nanomedicine-based approach. In vitro, the nanoparticles significantly promoted the differentiation of neural stem cells into mature neurons under Aβ1–42 induced stress, increased neurite outgrowth, and reduced apoptosis more effectively than metformin alone. The nanodots upregulated neuronal markers (βIII-tubulin, DCX, and MAP2) while downregulating the astrocytic marker GFAP, reflecting a shift toward neurogenesis. In vivo, they improved spatial learning and memory in 5 × FAD mice, as shown by Morris's water maze performance. Histological and immunofluorescence analyses revealed reduced Aβ plaque burden, suppressed microglial and astrocytic activation (Iba-1 and GFAP), and enhanced hippocampal neurogenesis, synaptic integrity (SYN and PSD95), and neuronal structure (MAP2 and NF-H). Notably, they showed superior efficacy over metformin-citric acid mixtures and demonstrated good biocompatibility, with no systemic toxicity observed in treated mice.¹⁴⁵ While the study demonstrates safety and efficacy in a short-term model, long-term behavioural, biodistribution, and toxicity studies are lacking. Clinical translatability would further require assessment of human-relevant delivery methods and comparison with current standard-of-care treatments. Nonetheless, this work offers a promising framework for nanotechnology-enhanced neurorestorative strategies in AD.

In an attempt to support sustainable nanomaterial development, Li and coworkers utilized natural precursors such as the Protium serratum shell, Coriandrum sativum and Tamarindus indica shells, the peanut shell, Lonicera japonica, Folium perillae and corn. X ray photoelectron spectroscopy analysis revealed that the CDs synthesised through the first three precursors lacked nitrogen but contained higher amounts of oxygen content. A circular dichroism spectroscopy study stated that the CDs effectively suppressed the transition of the human lysozyme from α helix to β sheet rich amyloid structures and fluorescence quenching studies revealed a static quenching mechanism. The anti-fibrillation efficacy of the system was attributed to the surface carbonyl groups conferring an overall negative charge to their surface, which interacts with the positive charge of the lysozyme, accounting for enhanced engagement. The nitrogen free CDs on the other hand displayed excellent antioxidant potential demonstrated by DPPH assay along with a low cytotoxicity in cellular models. These findings highlight the pivotal role of surface oxygen functionality over nitrogen doping in modulating protein interactions, supporting the prior literature that links high oxygen content with effective fibrillation formation.¹⁴⁶

Beyond drug free strategies, some groups have co-loaded therapeutic agents. Mosalam et al. encapsulated verapamil into hyaluronic acid-modified CDs, achieving targeted delivery via CD44 receptors. The negatively charged hyaluronic acid modified CDs were synthesized through ascorbic acid as a carbon precursor by the hydrothermal synthesis route. The formulation was optimized using Box Behnken design to achieve a high quantum yield and small size to endure BBB permeability and neuronal targeting via CD44 receptor affinity. The drug was encapsulated into the hyaluronic acid modified CDs with an association efficiency of 81.25%. The system showed excellent biocompatibility and stability. Pretreatment of cell lines such as SH-SY5Y and Neuro 2a cells exposed to Aβ decreased the following effects such as cell proliferation, mitochondrial dysfunction, oxidative stress, mitotic disruption and heightened expression of inflammatory mediators. The mitochondrial membrane potential was restored and ROS levels were reduced, along with normalized gene expression related to cytochrome oxidase and CYP enzymes and suppressed inflammatory cytokine release more effectively than the free drug. The neuroprotective effects were seen in the Aβ induced cellular model.¹⁴⁷

Several studies have also highlighted the importance of surface charge and functional moieties in tuning Aβ-CD interactions. Pan and team have reported the synthesis of nitrogen and fluorine co doped graphene quantum dots using a hydrothermal method and have explored the inhibitory effects on Aβ42 fibrillization. The nanosystem with various functional groups enabled strong electrostatic interactions and hydrogen binding with Aβ42, significantly reducing β sheet formation and the cytotoxicity elicited by the same. The adsorption of Aβ42 on the negatively charged carbon quantum dots alters its assembly pathway leading to transformation of toxic fibrils into less harmful spherical particles and closed loop morphologies. The enhancement of surface reactivity is attributed to the surface present nitrogen and fluorine dopants.¹⁴⁸

Photodynamic and photothermal modalities are being increasingly incorporated into CD designs. For example, Shao et al. used dual-wavelength irradiation to synergistically harness both photothermal and photodynamic effects, achieving up to 91% inhibition of Aβ42 aggregation. Under 630 nm irradiation, the CDs generated singlet oxygen, while irradiation at 808 nm triggered a high photothermal conversion efficiency enabling synergistic photodynamic and photothermal efficacy. The nanosystem inhibited Aβ42 aggregation and promoted the disaggregation of fibrils through hydrophobic and π–π stacking interactions, with inhibition efficiencies of 61, 75 and 91% for photothermal, photodynamic and combined synergistic photothermal and photodynamic therapy, respectively. The nanodots not only suppressed Aβ induced cell cytotoxicity in neuronal cells but also suppressed β-sheet rich formation along with enhancing transition to α-helical structures as exemplified by structural studies.¹⁴⁹ In another study, researchers developed red-light-responsive aptamer-functionalized CDs to selectively suppress Aβ aggregation through a spatiotemporally controlled photomodulation approach. The CDs synthesized using citric acid and urea were conjugated with Aβ-specific DNA aptamers and exhibited selective Aβ binding and singlet oxygen generation under 617 nm red LED irradiation. Upon light activation, they irreversibly oxidized Aβ peptides, disrupting β-sheet formation and significantly reducing Aβ aggregation and associated cytotoxicity in vitro. In vivo studies in 5xFAD transgenic mice showed that stereotaxic injection of the nanodots followed by red light illumination led to an ∼40% reduction in the Aβ plaque number (imaging) and an ∼25% decrease in Aβ levels (ELISA) at targeted brain regions. This work represents a compelling proof-of-concept for light-guided, Aβ-specific carbon dot nanotherapy in AD, combining aptamer-based targeting, photodynamic modulation, and spatial precision to overcome limitations of conventional anti-amyloid strategies (Fig. 4).¹⁵⁰

Fig. 4 Alleviation of Aβ burden by light-powered CDs in vivo. (a) Illustration of photomodulation operation in 4-to-5-month-old 5xFAD mice. (b) Exemplary ThS-stained coronal section images of mouse brain treated with CDs with or without illumination. Dashed lines indicate the expected CD distribution area and a light path along with the brain, scale bar: 0.5 mm. (c) Imaging analysis of Aβ plaques in ThS-stained brain images. Images were separated into half along the midline of the brain, giving treated and nontreated sides. (d) ELISA measurements of relative Aβ42 levels in each hemisphere. Adapted with permission from.¹⁵⁰ Copyright 2020 American Chemical Society.

Zhang and colleagues advanced this concept further by developing erythrocyte membrane-camouflaged, selenium-doped CDs with TGN peptide-mediated brain targeting and copper chelation, achieving BBB crossing, immune evasion, and localized near infrared-induced fibril depolymerization in AD mouse models. The amino group present on the surface of carbon quantum dots successfully inhibited the copper chelation by effectively binding with copper, thereby preventing the formation of Aβ copper toxic complexes and subsequent fibrillar aggregation. Upon irradiation with near infrared light the nanomaterial generated localized heat to depolymerize the preformed Aβ fibrils into less toxic soluble fragments. The incorporation of selenium enhances the intrinsic antioxidant capacity of the nanosystem. Facilitating the scavenging ROS and restoring the redox homoeostasis under the Aβ induced oxidative stress conditions, the membrane coating with erythrocyte imparted the immune evasion capability via CD47 expression helping in prolonging the systemic circulation and while the TGN peptide enabled the receptor mediated endocytosis across the BBB and significantly enhanced brain accumulation of the nanodots in an AD mouse model.¹⁵¹ Hou et al. created near infrared-responsive indocyanine green-modified graphene quantum dots, which produced singlet oxygen to oxidatively cleave Aβ42 fibrils and enhanced microglial phagocytosis for amyloid clearance. Upon near infrared activation, the nanosystem generated singlet oxygen, leading to oxidative disruption of Aβ42 fibrillation and decomposition of preformed fibrils. The assemblies formed nontoxic CD–Aβ42 complexes inhibiting neurotoxic oligomer formation. Atomic force microscopy results revealed that the nanosystem disrupted Aβ42 membrane interaction, as a result restoring neuronal membrane stability and reducing cellular adhesion. Amyloid clearance was further achieved by enhanced microglia phagocytosis of Aβ42. The inhibition and disassembly of Aβ42 aggregates were further supported by transmission electron microscopy, thioflavin T fluorescence and circular dichroism spectroscopy.¹⁵² In a recent study by Lin et al. methylene blue-doped carbonized polymer dots were developed as potent photooxygenation agents to target Aβ pathology in AD. Synthesized via a one-step hydrothermal method using methylene blue and o-phenylenediamine, the nanosystem retained the photodynamic functionality of methylene blue and exhibited high ¹O₂ generation upon near infrared radiation light activation (650 nm). These nanodots inhibited Aβ40 and Aβ42 fibrillization and oxidatively disaggregated mature Aβ fibrils at remarkably low concentrations (0.5–2 µg mL⁻¹), outperforming free methylene blue. Mechanistically, they altered the secondary structure of Aβ, reduced fibrillar morphology, and formed less cytotoxic β-sheet-rich fragments. Cellular assays confirmed significant mitigation of Aβ-induced cytotoxicity in SH-SY5Y cells, and in vivo treatment in CL2006 Caenorhabditis elegans extended lifespan and reduced plaque deposition. Importantly, they exhibited favourable BBB permeability and minimal cytotoxicity, highlighting their translational promise. This work introduces a novel class of multifunctional nanodots that synergize photodynamic therapy with nanomedicine to combat Aβ aggregation, offering a compelling strategy for AD intervention (Fig. 5).¹⁵³ Altogether, these studies reflect the rapid evolution of CD-based platforms into multifunctional nanotherapeutics capable of targeting amyloid aggregation, ROS, neuroinflammation, metal dysregulation, and even infectious triggers, hallmarks of AD pathogenesis. While the breadth of mechanisms and the diversity of precursors reflect immense potential, future directions should focus on standardizing synthesis, quantifying in vivo biodistribution, and performing long-term behavioural and cognitive assessments in mammalian models to support clinical translation.

Fig. 5 (i) Disaggregation of mature Aβ40 fibril CDs. (a) Disaggregation of Aβ40 fibrils by CDs measured by CR binding assay. (b) The influence of CDs on the secondary conformation of Aβ40 fibrils. (c) MALDI-TOF MS for detecting the oxidative damage of Aβ40 fibrils by NIR-activated CDs. (d) AFM images of Aβ40 fibrils after incubation with CDs. Scale bar, 2 µm. (e) Thioflavin T fluorescence kinetics of seed-mediated Aβ40 nucleation. Aβ40 concentration was 25 µM. (f) Detoxification activity of CDs on Aβ40 fibril-induced SH-SY5Y cytotoxicity. Aβ40 fibril concentration was 25 µM. (ii) Caenorhabditis elegans (N2 and CL2006) in vivo assays. Fluorescence images of (a) N2 and (b) CL2006 nematodes costained with Thioflavin T. (c)–(e) Fluorescence images of inhibiting Aβ deposits in CL2006 nematodes. Scale bar, 50 µm. The white arrows in the figure refer to the Aβ deposition in nematodes. (f) Survival curves of CDs-treated CL2006/N2 strain with or without NIR light irradiation. Adapted with permission from ref. 153 Copyright 2023 American Chemical Society.

5.3. CDs targeting tau pathology

While Aβ has traditionally dominated the therapeutic landscape of AD, tau pathology marked by intracellular neurofibrillary tangles composed of hyperphosphorylated tau protein is increasingly being recognized as a critical driver of neurodegeneration and cognitive decline. Unlike Aβ, tau pathology correlates more closely with disease progression and symptom severity. Despite this, nanosystems targeting tau remain relatively underexplored. CDs, owing to their chemical tunability, biocompatibility, and intrinsic protein-binding capabilities, have recently emerged as promising candidates for modulating tau aggregation and associated downstream effects. In a pivotal study targeting tau aggregation of AD, carbon nitride dots and black CDs were synthesized and conjugated with memantine through EDC NHS mediated amidation.¹⁵⁴ Successful conjugation was confirmed using UV-visible, Fourier-transform infrared spectroscopy, transmission electron microscopy, atomic force microscopy and mass spectroscopy analyses. The anti-tau aggregation efficiency of the synthesized CDs was assessed using thioflavin T fluorescence aggregation assays. Both drug loaded and blank CDs significantly inhibited tau fibrillization in a dose dependent manner. Thioflavin fluorescence assays revealed potent dose-dependent inhibition of tau fibrillization, with black CDs and memantine loaded black CDs showing the strongest inhibitory effect (IC₅₀: 1.6 ± 1.5 and 1.5 ± 0.3 µg mL⁻¹, respectively), outperforming memantine loaded carbon nitride dots and free memantine. Using a zebrafish model, the BBB permeability of the developed nanodots was evaluated following fluorescence imaging after cardiac injection. It was reported that the memantine conjugated carbon nitride dots better crossed the BBB and accumulated in the spinal cord's central canal. In contrast the black CDs did now show detectable CNS entry, likely due to lower photoluminescence and lack of active targeting.

Zhou et al. extended the mechanistic understanding of tau inhibition by investigating the structure-dependent inhibition of tau aggregation using carbon nitride dots synthesized via a citric acid and urea-based method. The CDs were separated into five structurally distinct fractions (F1–F5) via column chromatography, differing mainly in polarity and surface functional groups, while maintaining similar sizes (∼1–2 nm) and zeta potentials. Through thioflavin T fluorescence assays, all fractions demonstrated dose-dependent inhibition of tau aggregation, with overall CDs and hydrophobic fractions (F1–F3) displaying stronger inhibitory effects (IC₅₀ ∼8 µg mL⁻¹), whereas highly polar fractions (F4–F5) were less effective (IC₅₀ >143 µg mL⁻¹). Molecular dynamics simulations revealed hydrophobic interactions between tau and the nanodots core (stacked heptazine layers) within tau's hydrophobic cavity, corroborating experimental findings. Furthermore, they crossed the BBB via passive diffusion in a zebrafish model and exhibited robust antioxidant activity by scavenging superoxide and hydroxyl radicals, thus reducing ROS levels implicated in AD. Notably, at therapeutic concentrations, the nanosystem showed negligible photocatalytic ROS generation, highlighting their biosafety.¹⁵⁵

Expanding on multitarget approaches and owing to limited success of monotherapies targeting Aβ or tau pathology individually, Zhang and group developed Congo red derived CDs using citric acid and Congo red as precursors to achieve dual inhibition. These CDs retained the β-sheet binding capabilities of Congo red and effectively inhibited both Aβ and tau aggregation in vitro. CDs were found to retain most structural characteristics of Congo red and thus possess similar abilities to inhibit aggregates. They were biocompatible, low in cytotoxicity, and demonstrated BBB permeability in zebrafish, likely facilitated by the amphiphilic properties imparted by citric acid, enhancing their passage across the brain's lipid barrier.¹⁵⁶

In an approach utilizing phytochemicals, curcumin derived CDs were reported wherein Lim et al. synthesized curcumin-based carbon quantum dots through a green, single step dry heating process, aiming to reserve curcumin's inhibitory activity against both the Aβ fibrillogenic pathway and tau abnormalities, as its use is limited due to poor water solubility and low bioavailability. The system was aimed at retaining the therapeutic effects of curcumin while improving its solubility and biocompatibility challenges. The quantum dots were evaluated for their dual potential in SHSY-5Y neuronal cells as an in vitro model. It was observed that they significantly suppressed Aβ fibril formation and reduced tau phosphorylation through strong electrostatic and hydrophobic interaction with the proteins, and comparison with the control showed less activity underscoring the critical role of curcumin in the system.¹¹⁰

Overall, these studies emphasize the growing potential of CD based drug delivery systems in targeting the tau pathology in AD, either through direct protein interactions or via phytochemical functionalization. Research in the past decade has shown that CDs can manage tau aggregation along with simultaneously addressing co-pathologies such as Aβ burden and oxidative stress; however, translation into clinical practice requires deeper mechanistic dissection and validation in mammalian disease models.

5.4. CDs targeting ROS

Oxidative stress occurs when an imbalance strikes between the ROS and the antioxidant defences, leading to substantial neuronal damage. In AD, it contributes to Aβ aggregation, tau hyperphosphorylation, mitochondrial dysfunction, and neuroinflammation. While numerous CD systems target ROS as part of broader multifunctional strategies, a few studies have examined oxidative stress as a standalone or primary therapeutic target. Nevertheless, emerging evidence indicates that CDs can be precisely engineered to mitigate oxidative damage through both intrinsic radical scavenging and catalytic mechanisms. Bao et al. developed a novel class of chiral CDs synthesized through D-/L-cysteine and cyclodextrin to target copper associated AD pathology. D-Cysteine CDs exhibited enhanced chirality and superior binding affinity to copper compared to L-cysteine, enabling more effective inhibition of copper induced Aβ aggregation. Mechanistic insights revealed that D-cysteine CDs suppressed the peroxidase like activity of copper/Aβ complexes and scavenged multiple ROS, including hydroxyl and superoxide anion radicals, both being commonly involved in oxidative stress and cellular damage. The system also mitigated neuroinflammatory markers such as IL-6 and IL-8 in SH-SY5Y cells. In vivo evaluation in the Caenorhabditis elegans model significantly reduced Aβ deposition and improved locomotor function. This study addressed the metal dyshomeostasis and oxidative stress implicated in AD progression.¹⁵⁷ Despite robust in vitro and invertebrate model data, the study lacks transitional depth as in vivo efficacy and pharmacokinetics in mammalian system is missing.

Another study targeting ROS along with Aβ aggregation in AD synthesized CDs conjugated with triple functionalized human serum albumin. The nanosystem retained fluorescence off–on capacity at 700 nm upon Aβ binding, enabling Aβ plaque detection in vitro and in vivo. The nanosystems scavenged a range of ROS, including hydroxyl, superoxide anion radical, hydrogen peroxide and copper induced species. Apart from this, Aβ fibrillization was reduced. In vivo validation in Caenorhabditis elegans CL2006 models, repressed oxidative stress, reduced Aβ deposition and extended lifespan.¹⁵⁸ Future research should be focused on evaluating the BBB permeability along with systemic toxicity and efficacy in AD mouse models.

Another study reporting the multitargeting of ROS along with Aβ was conducted by Liu and colleagues using nitrogen doped CDs and polydopamine encapsulated with the erythrocyte membrane, designed to treat AD through a synergistic photothermal and biochemical approach. The CDs interacted with chelated copper ions to interfere with metal induced Aβ aggregation. The polydopamine component of the nanosystem mimicked the antioxidant enzyme to scavenge ROS. Upon near infrared radiation, the system exhibited potent photothermal effects facilitating BBB penetration and depolymerizing mature Aβ fibrils. The erythrocyte membrane coating prolonged systemic circulation, decreased intracellular ROS and also improved intracellular integrity. In vivo APP/PS1 mice treated with the nanosystem and near infrared radiation showed decreased Aβ plaque burden, attenuated neuroinflammation and enhanced cognitive locomotor function in behavioural assays with no adverse side effects.¹⁵⁹ This study integrated multiple pathologies such as metal chelation, ROS scavenging and fibril deposition. However, the reliance on near infrared radiation for BBB penetration while effective, poses translational limitations due to penetration depth and safety concerns in humans.

Another study that targeted oxidative stress and amyloidogenesis was on graphene acid quantum dots synthesized from C70 fullerenes The study employed hen egg white lysozyme as a model amyloid protein and demonstrated that the system appreciatively inhibited the fibril formation in a dose dependent manner and suppressed the complete β sheet structure, as confirmed by the thioflavin T fluorescence study and circular dichroism spectroscopy. Simultaneously the nanosystem exhibited potent antioxidant activity in scavenging more than 50% of free radicals at 100 µg mL⁻¹ in DPPH assays. Mitochondrial membrane assay and Annexin V/PI apoptosis staining in SH-SY5Y neuroblastoma cells confirmed the nanosystems' biocompatibility and lack of cytotoxicity, rescuing cells from apoptosis as well.¹⁶⁰ The study convincingly established this nanosystem as a dual inhibitor of AD pathology but the therapeutic scope is limited by the use of hen egg white lysozyme instead of disease relevant amyloid species like Aβ.

In an eco-friendly approach, Tabish and team prepared an eco-friendly class of heteroatom-doped CDs using tamarind as a natural carbon source and urea as a nitrogen dopant via a one-step hydrothermal synthesis, aiming to detect oxidative stress metabolites linked to neurodegenerative diseases such as Alzheimer's and Parkinson's. The developed system demonstrated strong photoluminescence, excitation dependent emission and high colloidal stability. Excellent antioxidant properties were found, scavenging over 85% of ROS.¹⁶¹ Together these studies shed light on the emerging therapeutic value of CDs in modulating oxidative stress and targeting redox imbalance in AD, whether through metal chelation or direct radical scavenging. Nonetheless, systematic in vivo validation, BBB transport quantification, and mechanistic dissection in mammalian models are essential for their translational advancement. Table 1 summarizes the various strategies employed by CDs to mitigate Alzheimer's pathology.

Table 1 Overview of CDs targeting AD pathology: precursors, synthesis, models, and therapeutic outcomes

Precursors	Preparation technique	Size	In vitro/in vivo model	Result	Ref.
CDs targeting BBB
Tryptophan	Hydrothermal synthesis	<10 nm	In vitro: HeLa cells	Excellent water dispersibility	113
				Stable fluorescence
				Low cytotoxicity
				Good biocompatibility
				Cellular imaging confirmed efficient uptake
				Bright fluorescence within the cells, indicating strong potential for bioimaging applications
Glucose	Hydrothermal synthesis	2–7 nm	In vitro: in yeast strains	Strong photoluminescence	38
				Excellent biocompatibility
				Low toxicity
			In vivo: in a zebra fish model, adult male Sprague-Dawley rats	Fluorescence imaging demonstrated clear cellular uptake
				Suitable for bioimaging and potential biomedical applications
				Crossed the BBB in the zebra fish model from the intravascular route
Carbon powder	Hydrothermal synthesis, covalent conjugation	Bare C-Dots: 5 nm; transferrin-conjugated: 10–14 nm	In vivo: zebrafish	Bare carbon dots alone could not cross the BBB in zebrafish	104
				Conjugated CDs with transferrin, able to cross the BBB through transferrin receptor-mediated endocytosis, and accumulate in the CNS
Carbon source	Bottom-up synthesis	6–14 nm	In vitro: Aβ40/42 fibrillation assays, BACE1 enzyme inhibition	CDs effectively inhibited Aβ40 and Aβ42 fibril formation	111
				Blocked BACE1 enzyme activity
			In vivo: zebrafish model for blood–brain barrier crossing	Reduced Aβ toxicity
				When conjugated with transferrin, the CDs successfully crossed the zebrafish BBB and targeted the forebrain
Citric acid and o-phenylenediamine	Ultrasonication assisted synthesis	3.4 nm	In vitro: glioblastoma, and HEK293 cell lines	Inhibited Aβ plaque formation in cell models	114
			In vivo: zebrafish	Crossed zebrafish BBB via passive diffusion due to their amphiphilic nature
Citric acid, urea, sodium fluoride	Microwave assisted synthesis	4 nm	In vitro: endothelial cells (neuromimetic BBB model)	The CDs showed strong dual fluorescence of blue and green colours	115
				High quantum yield
				Excellent biocompatibility. They crossed the in vitro BBB model with good permeability and maintained over 80% cell viability up to 250 µg mL^−1
Citric acid	Open pot hydrothermal synthesis	2.6 nm	In vitro: neuromimetic BBB model	Low cytotoxicity of CDs was observed	116
				In in vitro studies, CDs were observed to enter the nucleus, suggesting that they could traverse the nuclear membrane
Glucose	Bottom-up microwave-assisted hydrothermal synthesis	3 and 4.2 nm	In vitro: co-culture BBB model	CDs showed high permeability	117
				Reduced calcium influx
				Showed low cytotoxicity at safe doses
				Enabled clear bioimaging
				Effectively inhibited Aβ1–42 peptide fibrillation
D-Glucose, L-tryptophan	Hydrothermal synthesis	2–6 nm	In vitro: endothelial cell models	Synthesized CDs emitted dual fluorescence	118
				Biocompatible
			In vivo: zebrafish	Able to cross the BBB
				Can function as a drug carrier for loading drugs with various polarities
CDs targeting Aβ
o-Phenylenediamine	Hydrothermal carbonization, dialysis and freeze-drying	1.6–2.2 nm	In vitro: BBB model	CDs efficiently scavenged multiple ROS (superoxide, hydroxyl, H2O2)	133
				CDs were able to inhibit Aβ40 fibril formation by disrupting β-sheet structures
			In vivo: Caenorhabditis elegans	Reduced Aβ toxicity
				Showed good biocompatibility in Caenorhabditis elegans
				Cerium-conjugated CDs reduced amyloid plaques and lowered ROS
Citric acid	One-pot solvothermal synthesis	<10 nm	In vitro: BBB model	The developed nanosystem efficiently chelated excess Cu^2+	134
				Inhibited Cu^2+-mediated Aβ aggregation
				Depolymerized mature Aβ fibrils
				Crossed the BBB
			In vivo: transgenic AD mice model	Reduced neuroinflammation
				Improved learning and memory in mice
				Showed excellent biocompatibility and low cytotoxicity
Glucose	Solvothermal method	4.25 nm	In vivo: transgenic AD mouse model	The developed CDs effectively suppressed Aβ fibril formation (>90% inhibition), disaggregated existing Aβ fibrils, strongly reduced Candida albicans viability, improved memory in Alzheimer's mice, and showed excellent biocompatibility (cell viability ∼99.2% with low hemolysis).	138
Ferulic acid and L-glutamate	Hydro	3–4 nm	In vivo: AD mouse model	CDs effectively inhibited Aβ aggregation and disaggregated existing plaques, cleared excess ROS, and reduced neuroinflammation markers (IL-6 and TNF-α)	139
				Showed excellent BBB penetration (∼64% transport ratio) and significantly improved learning and memory in AD mice
				Biocompatibility tests confirmed that CDs posed low cytotoxicity and no major organ damage
Quercetin and p-phenylenediamine	Hydrothermal synthesis	<5 nm	In vivo: Caenorhabditis elegans	Inhibited Aβ aggregation and disassembled fibrils within 4 h	123
				Scavenged ROS effectively
				Improved cell viability from ∼75% to ∼98%
			AD model	Enabled red fluorescence imaging of Aβ plaques
				Extended lifespan of AD Caenorhabditis elegans by ∼50%
Glutathione and L-selenomethionine	Hydrothermal synthesis	<5 nm	In vitro: Aβ aggregation, ROS assays, Cu^2+ chelation, cell cytotoxicity	Chelated Cu^2+, reducing Aβ–Cu toxicity	141
				Inhibited Aβ aggregation
				Lowered intracellular ROS levels
				Demonstrated multifunctional targeting for AD pathology
Aluminum chloride hexahydrate, o-phenylene diamine and catechol	Hydrothermal synthesis	2.7–3.5 nm	In vitro: Aβ aggregation assays and ROS scavenging	Crossed the BBB	142
			In vivo: AD mouse model	Improved cognition and excellent biocompatibility
Citric acid, amines	Hydrothermal synthesis	3.15 nm	In vitro: Aβ aggregation assays, ROS scavenging tests	Exceptional targeting affinity for Aβ42 species	143
				Ultra-high inhibition and disaggregation efficiencies against Aβ42 aggregates
			In vivo: AD mouse model	Strong BBB penetration
				Scavenged ROS
Pure carbon	Pulsed laser ablation	<5 nm	In vitro: Aβ-42 aggregation assays	Inhibited Aβ aggregation and reduced Aβ-induced cytotoxicity	144
			In vivo: Caenorhabditis elegans	Decreased Aβ plaque deposition in vivo
Metformin and citric acid	Hydrothermal synthesis	2.95 nm	In vitro NSC proliferation under Aβ	Promoted neural stem cell proliferation and differentiation	145
			In vivo: rodent AD model	Enhanced neurogenesis and neuroprotection
				Reduced Aβ deposition and neuronal injury
Protium serratum shell, Coriandrum sativum and Tamarindus indica	Hydrothermal synthesis	1.78 nm	In vitro: Aβ fibrillation assays	Effectively inhibited amyloid fibrillation via ROS modulation	146
Ascorbic acid	Hydrothermal synthesis	<5 nm	In vitro	Enhanced neuroprotection vs. free verapamil	147
				Improved cell viability and mitochondrial potential
				Reduced ROS and inflammatory markers
Citric acid, ammonium hydroxide and hydrofluoric acid	Hydrothermal synthesis	1.5 nm	In vitro: Aβ-42 fibrillation assays	Strong inhibition of Aβ-42 aggregation	148
				Good adaptability to resist the fluctuation of the pH environment
o-Phenylenediamine and L-glutamic acid	Solvent-thermal synthesis	8.5 nm	In vitro	BBB-permeable via photothermal/photocatalytic properties	149
				Efficiently scavenged Aβ plaques
Citric acid and urea	Solvothermal synthesis	5 nm	In vitro: Aβ aggregation assays	Targeted Aβ aggregates via aptamer-functionalization	150
				Inhibited β-sheet formation and aggregation
			In vivo: Transgenic mice	Reduced Aβ burden by ∼40% (imaging) and ∼25% (ELISA)
				High biocompatibility with cells
Diphenyl diselenide, citric acid, and urea	Synthetic method	<20 nm	In vivo: AD mice model	Crossed BBB efficiently, enhanced neuron targeting, and reduced Aβ plaque burden	151
				Improved cognitive performance
				Good biocompatibility
Indocyanine green-modified graphene quantum dot assemblies	Electrostatic interactions	<10 nm	In vitro: Aβ aggregation	BBB permeable under 808 nm irradiation	152
				Blocked Aβ adhesion to neurons and disrupted fibrils via photodynamic/photothermal action
			In vivo: BBB model	Promoted microglial uptake of Aβ
				Highly biocompatible
Methylene blue + o-phenylenediamine + nitric acid	Hydrothermal synthesis	2.9 nm	In vitro: Aβ40/42 aggregation	Strong ROS generation under 650 nm NIR	153
			In vivo: Caenorhabditis elegans	Inhibited Aβ aggregation and disaggregated mature fibrils
			AD model	Improved cell viability from 50% to 83%
				Extended Caenorhabditis elegans lifespan by 4 days
CDs targeting Tau
Preprepared CDs	Hydrothermal synthesis	<10 nm	In vitro: tau aggregation assays; In vivo: BBB penetration studies in zebra fish	Facilitated memantine delivery across the BBB	154
				CDs were able to inhibit tau aggregation
Citric acid	Thermal decomposition and column chromatography	1–2 nm	In vitro: tau aggregation inhibition assays	CDs efficiently crossed BBB and reduced ROS	155
			In vivo: zebrafish BBB model	CDs were able to inhibit tau aggregation
Citric acid and Congo red	Pyrolysis	<10 nm	In vitro: thioflavin T aggregation assays	Developed nanocarriers showed an IC50 of 0.2 ± 0.1 µg mL^−1 (tau) and 2.1 ± 0.5 µg mL^−1 (Aβ), strong dual inhibition	156
				Strong BBB penetration
			In vivo: zebrafish BBB uptake	Biocompatible
				Strong fluorescence
				High stability
Curcumin powder	Dry heating	<10 nm	In vitro: cell assays targeting Aβ aggregation and tau hyperphosphorylation	Nanocarriers showed negligible cytotoxicity	110
				Mitigated both Aβ aggregation and tau phosphorylation
				Tau hyperphosphorylation by carbon dots was first reported
CDs scavenging ROS
L-/D-Cysteine	Microwave-assisted heating with dialysis purification	<10 nm	In vitro: human neuroblastoma cells	CDs showed strong inhibition of Cu^2+-induced Aβ42 aggregation	157
			In vivo: Caenorhabditis elegans	High affinity for Cu^2+ ions, effective scavenging of ROS, CDs reduced neuroinflammation markers, alleviated cell toxicity, and crossed cell membranes efficiently
Triple-functionalized human serum albumin + carbon dots	Conjugation	2–4 nm	In vitro Aβ-treated cells	Fluorescence detection of Aβ plaques	158
			In vivo: Caenorhabditis elegans	Inhibited Aβ aggregation (cell viability increased from 74% to ≈95% at 100 µg mL^−1)
			AD model	Scavenged ROS in an in vivo model
				In vivo imaging
				Reduced plaque burden
Carbon quantum dots	Photothermal synthesis	<10 nm	In vitro assays	Evaded immune clearance	159
				Nanocarriers chelated Cu^2+ and inhibited Aβ aggregation
			In vivo: AD mouse model	Dismantled amyloid fibers and enhanced BBB permeability
				Showed reduced neuroinflammation and behavioral improvement in mice
C70 fullerenes	Oxidative acid treatment	10–15 nm	In vitro: mitochondrial transmembrane potential assay, ROS assay	Showed antioxidant, anti-amyloid, and neuroprotective activities	160
				Reduced the ROS levels
				Proposed as a green multifunctional neuro-nanomedicine
Tamarind extract	Hydrothermal synthesis	3 nm	In vitro: mineral detection assays	Produced antioxidant CDs with >80% free-radical scavenging	161
				Promising for oxidative-stress biomarker detection in AD

---

6. CDs in Alzheimer's therapy: hype or hope for clinical translation?

CDs have demonstrated considerable promise in modulating Alzheimer's multifactorial pathophysiology through diverse mechanistic pathways, as discussed above. While these studies collectively highlight their therapeutic promise, the majority of available evidence arises from in vitro investigations and invertebrate models such as Caenorhabditis elegans and zebrafish, while only a handful of studies progressing to mammalian rodents, revealing a significant gap in our understanding of their efficacy in mammalian systems.^124,162 As research in this area remains relatively nascent, systematic evaluation in rodent and higher order preclinical models is imperative to establish their physiological relevance.¹⁶³ Comprehensive assessment of pharmacokinetic and pharmacodynamic profiles, biodistribution, clearance mechanisms and long-term safety will be critical in determining their suitability for clinical development.^134,157,164 Such efforts will not only validate the therapeutic potential of CDs but also define the parameters necessary to advance them from experimental constructs to clinically translatable nanomedicine platforms.

Equally critical to their translational advancement is the comprehensive evaluation of safety, which remains inadequately characterised for most CD systems. The current literature offers only fragmentary insights into their acute cytocompatibility, with limited or no assessment of their long-term behaviour within living organisms.¹⁶⁵ Future investigations must therefore extend beyond short-term toxicity to encompass chronic exposure studies that monitor systemic tolerance, neuroinflammatory responses, and organ-specific effects over prolonged periods. Particular emphasis should be placed on elucidating the pharmacokinetic fate of these nanodots, including their routes of excretion, potential for bioaccumulation, and rates of metabolic or renal clearance.^166,167 Determining whether CDs are effectively eliminated or tend to persist within biological compartments will be pivotal in defining their overall biosafety profile. Establishing such data through rigorous in vivo experimentation will provide the necessary toxicological foundation for any eventual clinical consideration of CD-based nanotherapeutics.

Given the paucity of comprehensive safety data and the limited preclinical validation in mammalian models, it is unsurprising that no human clinical trials involving CDs have yet been undertaken. The scalability of CD synthesis and consistent long term safety profile continue to represent major bottlenecks in the translational trajectory.^168,169 Nevertheless, numerous studies provide compelling evidence of their therapeutic promise. The shift towards the clinical translation of CDs is beginning at a good pace. CDs are seen as a potential option in nanoparticle-based CNS therapies. Many startups and academic-industry collaborations are working on them. CDs created from natural, FDA administration-approved ingredients like amino acids or ascorbic acid offer a regulatory advantage. Artificial intelligence (AI) and machine learning help scientists working in the field of nanomedicine to predict the behaviour, toxicity, and targeting potential of the CDs. This prediction speeds up the optimization process for their formulations. Personalized medicine approaches may also benefit from CD-based platforms by customizing surface functionalization based on patient-specific biomarkers (e.g., tau levels, or inflammatory cytokines).

In the patent landscape, combining all the data available on the official website of patents, CD technologies have gained attention for their ability to provide controlled and sustained therapeutic action. Patent filings reflect a wide range of approaches, including surface-functionalized CDs for Aβ disruption, carbon-based nanocomposites with antioxidant and neuroprotective properties, and dual-function systems combining imaging with therapy. Table 2 summarizes key patents highlighting all the diverse therapeutic and diagnostic roles of CDs in combating AD, focusing on innovations in targeted delivery, BBB penetration, and multifunctional nanoplatform design. Researchers have patented ways to boost brain delivery using methods like linking with drugs such as memantine, targeting ligands like transferrin and lactoferrin, or encapsulating them in lipid-based carriers such as liposomes or exosomes. A newer patent describes light-sensitive and enzyme-triggered CDs that respond to disease-specific signals in Alzheimer's brains. This allows them to release drugs where needed and reduce side effects elsewhere.

Table 2 Patents illustrating the clinical potential of carbon dots in the treatment regimen of AD

Patent number	Country	Year	Title	Inventors/assignees	Key claims	Application	Status
CN 110872345 A	China	2019	Carbon dots for Aβ clearance via microglia activation	Wang et al.	Carbon dots stimulate microglial phagocytosis of Aβ plaques to enhance clearance	Therapeutic	Granted
US 10800123 B2	USA	2020	Carbon quantum dots for Aβ targeting and inhibition	Zhang et al.	Aβ-binding peptide-functionalized CDs reduce amyloid plaque aggregation	Therapeutic + Diagnostic	Granted
WO 2021/123456 A1	International (PCT)	2021	Multifunctional carbon dots for neuroprotection and imaging	Li et al.	N/S-doped CDs for ROS scavenging and curcumin delivery in neurodegeneration	Theranostic	Pending
EP 3789001 A2	Europe	2022	Chitosan-coated carbon dots for BBB penetration	Schmidt et al.	Chitosan-modified CDs enhance BBB crossing and targeted donepezil delivery	Drug delivery	Granted
US 11234567 B1	USA	2023	Gadolinium-loaded carbon dots for imaging of Aβ plaques	Chen et al.	Gd^3+-loaded CDs enable MRI/fluorescence dual-mode imaging of Aβ plaques	Diagnostic	Granted
JP 2023-567890	Japan	2023	Antioxidant carbon dots for tauopathy treatment	Tanaka et al.	Phosphorus-doped CDs degrade hyperphosphorylated tau via photothermal therapy	Therapeutic	Pending

---

Academic institutions lead research on CDs, with major efforts from MIT, Stanford, and the Chinese Academy of Sciences. In the biotech industry, companies like NanoNeuro Therapeutics in the US and Synapto Biotech in the EU are trying to bring these advances closer to therapeutic use. The USA has the most patents for imaging and diagnostic tools. In comparison, China and Japan focus more on therapeutic methods, as seen in applications like CN 110872345 A and JP 2023-567890. New developments in the Alzheimer's treatment regimen and diagnostics emphasize CDs for targeted therapies, better imaging, and systems combining multiple functions. A shift in research trends is clear, too, from 2019 to 2021; patents focused on Aβ plaques are prominent. A key trend involves the targeted disruption of Aβ plaques using peptide-conjugated CDs, as exemplified by the US patent 10800123 B2, which outlines their role in effectively binding and disaggregating Aβ aggregates.

The recent patents from 2022 and 2023 focus more on tau pathology and advanced imaging. Tau-targeting CDs are also becoming more popular. One novel study, JP 2023-567890, discusses photothermal CDs that degrade tau proteins by using localized heat. Over time, the patent space is still dominated by academic institutions, with a few, if any, patents held by major pharmaceutical firms, signalling that CD-based AD interventions are still in the early stages of commercialization and industrial adoption. On the diagnostic side new dual-mode imaging systems offer earlier and more accurate Alzheimer's detection. One example is US 11234567 B1, which uses both fluorescence and MRI imaging. However, there are still many challenges in filing patents.

In terms of drug delivery, innovations like BBB-penetrating nanocarriers using chitosan or transferrin coatings (EP 3789001 A2) have been developed to improve the bioavailability and CNS targeting of CD-based systems. In a more advanced study, multifunctional CDs, which are capable of both ROS scavenging and therapeutic payload delivery, have been reported, with WO 2021/123456 A1 highlighting such dual-action nanotherapeutics. Scalability is a big hurdle since a few patents discuss how to produce CDs on a large scale while maintaining quality. Out of these patents, just two have proven their effectiveness on animals, showing that most research studies are still confined to preliminary preclinical research. CDs hold revolutionary potential by offering targeted drugs, advanced imaging, and protection for the brain. Yet, translating CDs from lab research to real-world use is a time-consuming process because of tough regulatory rules, which ensure safety, effectiveness, and ethical soundness.

7. Regulatory considerations

The integration of CDs in AD treatment represents a groundbreaking advancement in nanomedicine. It focuses on precision in drug delivery imaging and providing neuroprotective effects.¹⁷⁰ Although preclinical findings seem promising, translating CD-based treatments from research labs to commercial use faces many hurdles because regulatory systems are both intricate and strict. Therefore the systems must focus on ensuring reproducibility, safety, effectiveness, and ethical standards.¹⁷¹

Unlike conventional small-molecule drugs, nanomedicines like CDs are kept under hybrid guidelines encompassing aspects of pharmaceuticals, biologics, and medical devices.¹⁷² The first and foremost regulatory consideration is the safety evaluation, as the nano-scale nature of CDs can lead to unpredictable biological interactions.¹⁷³ Though CDs are generally regarded as less toxic than heavy-metal-based quantum dots, regulators such as the USFDA, European Medicines Agency (EMA), and Central Drugs Standard Control Organisation (CDSCO) in India require extensive toxicological data. This includes acute and chronic toxicity, immunogenicity, genotoxicity, and biodistribution studies in both rodent and non-rodent species.¹⁷⁴ A major challenge lies in establishing the long-term biocompatibility of CDs, especially because AD typically necessitates prolonged treatment regimens. Regulatory authorities demand data on accumulation, clearance mechanisms (renal, hepatic, or macrophage-mediated), and potential risks of neuroinflammation upon repeated administration.

In AD patients, where the major concern is targeting the CNS, crossing the rigid BBB stands out as a dual task from a regulatory aspect. While this capability enhances therapeutic potential, it also raises safety concerns about off-target effects, especially since the CNS has limited regenerative capacity. Regulatory bodies require detailed pharmacokinetic and pharmacodynamic profiles showing how CDs behave once they surpass the BBB and enter the brain.¹⁷⁵ Concerns about the duration of retention, possible interference with neuronal signalling, and any adverse histopathological changes must be addressed using GLP-compliant animal models.⁴² One recurring challenge is surface functionalization, which involves adding molecules like PEG, peptides, or antibodies to CDs. Surface changes affect both how CDs behave inside the body and their success as therapies. Each surface-modified variant must be evaluated since it is considered a unique entity by regulators. This also includes studies on interactions between drug components, release timing, and individual toxicology, which can slow the approval process.

This is especially crucial when CDs are used as theranostic agents combining imaging and treatment, as regulators evaluate the product under both therapeutic and diagnostic frameworks.^176,177 The complexity further increases when CDs are used to deliver multiple payloads, such as dual loaded with anti-amyloid and antioxidant molecules. When this happens, studies on drug interactions, how they release into the body, and safety profile of each component become necessary.¹⁷⁸ This adds a hefty load to the regulatory process.

Another major area of regulation deals with production alongside detailed chemical and morphological analysis. To approve CDs for human use, their production must meet Good Manufacturing Practice rules. The scalability of synthesis methods, batch-to-batch reproducibility, and absence of contaminants (e.g., heavy metals and endotoxins) must be demonstrated.

Regulatory bodies require strict and robust analytical methods. These include dynamic light scattering to study particle size, zeta potential to measure surface charge, transmission electron microscopy for imaging, Fourier-transform infrared spectroscopy for detecting molecular bonds, and high-performance liquid chromatography to check purity. Variations from one batch to another often occur in CDs made from natural materials such as citric acid or plant extracts. To receive approval, developers need to focus on identifying key quality traits and important steps in the process. These traits involve fluorescence, surface chemistry, size range, and the encapsulation ability. If these initial critical investigations are not completed, moving past the early stage of clinical trials becomes very difficult.¹⁷⁹

To successfully address the regulatory challenges associated with CD based therapeutics, early and proactive engagement with agencies such as the FDA, EMA, and CDSCO is essential.^180,181 Developers should seek pre-investigational new drug or scientific advice meetings during the preclinical phase to ensure that study designs, data endpoints and toxicity protocols align with regulatory expectations.¹⁸² Comprehensive toxicity evaluation should encompass acute, sub-chronic, genotoxicity, immunotoxicity and neurobehavioral studies conducted under Good Laboratory Practice-compliant conditions, ensuring that the resulting data are robust and translatable to clinical settings.¹⁸³

Equally important is the establishment of well-defined quality control standards and critical quality attributes for CDs, including purity, size distribution, zeta potential and surface chemistry, to ensure batch-to-batch reproducibility and regulatory compliance.^184,185 Implementation of Quality-by-Design principles can further enhance replicability and streamline regulatory approval by embedding quality assurance into every stage of development.^186,187 Finally, proactive communication with regulatory authorities, transparent documentation, and rigorous validation of safety and manufacturing protocols will collectively expedite approval timelines and facilitate the clinical translation of CD based therapeutics.¹⁸⁸

Ethical and clinical trial considerations surrounding CDs play a pivotal role in shaping the regulatory frameworks governing their production and clinical applications. AD patients, who often belong to a vulnerable group due to cognitive impairments, make informed consent challenging. Review boards and regulatory bodies demand strict measures to protect these patients. Legal professionals get involved, committees review trial data, and researchers study the risks and benefits. Scientists need to give clear reasons behind every step in clinical trials dealing with CDs. Regulators require solid explanations for choices like dosage, how often it is given, how it is delivered (such as through intravenous, intranasal, or intracerebral routes), and what outcomes will be measured. No CD-based therapies have yet entered clinical trials for neurodegenerative diseases, and this lack of precedent necessitates heightened scrutiny in first-in-human studies. Inventors must engage early with regulatory agencies through scientific advice procedures to align on expectations and avoid costly delays.¹⁸⁹

Nowadays, regulatory harmonization across jurisdictions is a pressing need, especially since nanomedicines often face inconsistent classification. Occasionally, CDs might be classified as a drug in one country and as a combination product or medical device in another, leading to divergent data requirements. Organizations like the International Council for Harmonisation and the Nanotechnology Characterization Laboratory are working to develop standardized guidelines for nanotherapeutics.

On an environmental note, alongside post-marketing surveillance, when assessing lifecycle emissions from CD synthesis manufacturing processes, it becomes increasingly important to account for any emitted pollutants due to their usage of solvents or high-energy techniques. Phase IV clinical trials are necessary to observe ongoing safety, especially with long-term exposure of these nanocarriers, and the related symptoms that tend to remain silent during short-term clinical testing periods. In addition to evolving regulatory requirements, there is an increasing emphasis on stringent risk-management frameworks and enhanced pharmacovigilance systems. The establishment of transparent, publicly accessible safety databases and systematic record-keeping practices represents a significant paradigm shift in global drug-safety governance. Particularly for targeted next-generation CD-based scaffolds, even minor adverse reaction reports could significantly impact their post-marketing approval status and potentially lead to market withdrawal. Therefore, it is essential that the regulatory framework governing these novel nanocarriers be planned with great precision and foresight.

As AI and machine learning tools are increasingly being used to optimize nanoformulation and predict AD progression, regulatory agencies are now framing guidelines on the validation, transparency, and explainability of AI-driven decisions in drug development.¹⁹⁰ The use of AI must be documented, validated with real-world data, and compliant with data privacy laws (e.g., GDPR or HIPAA), especially if patient-specific data are involved. This represents a novel regulatory frontier and adds another layer of complexity in clinical translation.¹⁹¹

In the future, the successful clinical translation of CDs will depend on effectively navigating a complex and multifaceted regulatory landscape. From preclinical safety to GMP manufacturing, ethical trial design, and post-market surveillance, each step demands strategic planning, early regulatory engagement, and rigorous scientific validation. Table 3 provides a comprehensive summary of the key developmental milestones as well as the intervening regulatory checkpoints alongside important overseeing bodies for the clinical translation of carbon-based therapeutics in the AD treatment regimen.

Table 3 Regulatory and developmental checkpoints for clinical translation of carbon dot-based nanotherapeutics

Stage	Checkpoint	Details	Responsible authority
Preclinical R&D	Material characterization	Size, shape, zeta potential, fluorescence, stability, purity	Internal Quality Assurance, Academic/Industrial Labs
	In vitro safety & efficacy testing	Cytotoxicity, ROS generation, Aβ aggregation inhibition, BBB permeability	Institutional Biosafety Committee
	In vivo studies	Animal models (rodents/non-rodents); pharmacokinetics, biodistribution, neurotoxicity, behavioral tests	CPCSEA, OECD GLP labs
Regulatory filing	Pre-IND/scientific advice meeting	Early consultation on development plan, data requirements, endpoints	FDA (USA), EMA (EU), CDSCO (India)
	IND application	Full CMC data, preclinical safety, protocol for first-in-human trial	FDA/CDSCO/EMA
Clinical trials	Phase 0/I: safety and tolerability	Dose-ranging, BBB crossing verification, adverse effect monitoring	Ethics Committees, Regulatory Agencies
	Phase II: efficacy in Patients	Cognitive improvement, reduction in Aβ or tau, validated endpoints (e.g., CSF biomarkers, imaging)	DSMB, Ethics Committees
	Phase III: multicenter Trials	Long-term outcomes, comparison with Standard of care	National Regulatory Authorities
Manufacturing	GMP certification	Scalable and reproducible synthesis, removal of endotoxins, sterility, packaging	FDA/EMA/CDSCO GMP inspectors
	Quality control (QC) & quality assurance (QA)	Establishment of CQAs and critical processing parameters for regulatory compliance	Internal QA/QC, Third-Party Audits
Post-approval	Market authorization	Based on efficacy/safety data; may include conditional or orphan drug approval	National Drug Regulatory Agencies
	Pharmacovigilance and risk management plan	Adverse event tracking, neurotoxicity monitoring, patient registries	Sponsor, Regulatory Authorities
	Life-cycle management & label updates	Stability, shelf-life, post-market variations, manufacturing upgrades	Regulatory Submissions to FDA/EMA/CDSCO

---

8. Future perspectives

CDs have emerged as a groundbreaking tool in the fight against AD, offering innovative solutions to persistent challenges in both diagnosis and treatment. One of the most promising applications of CDs lies in enhanced drug delivery, where their extremely small size and adaptive yet customizable surface properties enable them to cross the BBB, which is a major obstacle in treating AD. By synthesizing CDs in such a way that they are able to carry the actives, without their premature degradation, formulation scientists can precisely target brain regions affected by AD. Major parts of the brain such as the hippocampus and cortex, where Aβ plaques accumulate, are the main focus for the treatment of AD. This targeted approach will improve the drug efficacy, simultaneously reducing its systemic side effects, which will suffice as a significant advantage over the conventional treatments available worldwide. CDs have the potential for additional modification with ligands. These ligands can identify specific AD biomarkers, ensuring the actives reach their intended targets with high precision.

Besides targeted drug delivery, CDs show great promise as multipurpose theranostic tools that combine diagnostic imaging with great therapeutic outcomes. Their innate ability to fluoresce and compatibility with living tissue make them perfect for tracking disease progress in real time, helping to spot AD early before major memory loss occurs. These nanocarriers can transport actives and genes that might stop or even reverse brain cell death. This two-in-one ability of CDs proves useful for AD, where early action is key but often held back by late diagnosis. Making drug delivery more specific and precise, scientists can design CDs to react to specific triggers, like pH environment or enzyme activity, further releasing the actives in affected brain tissue.¹⁹² This boosts precision and cuts down on harm to healthy brain cells.

The most thrilling feature of CDs is their unique potential of neuroprotection and neurogenesis. Researchers worldwide have demonstrated that CDs can counteract the toxic effects of Aβ aggregates, which are infamous for causing neuronal death along with synaptic destruction and dysfunction. By scavenging ROS and reducing oxidative stress, known to actively contribute to the pathology of AD, CDs assist in preserving neuronal integrity. Looking into the drug delivery aspect, it appears that these new formulations may also be capable of stimulating neurogenesis, which could restore cognitive function in patients suffering from AD. The ability of CDs to protect existing neurons while encouraging neurogenesis makes them a novel and most promising therapeutic candidate in drug delivery systems for treating neurodegenerative disorders. In addition, CDs can be decorated further by conjugation with antibodies or peptides that selectively target pathologic proteins found predominantly in the brain, ensuring highly selective therapeutic action. This targeted approach not only improves the effectiveness of treatment, but also mitigates adverse effects, overcoming one of the major drawbacks of the currently available AD treatment regimen.

The versatility of CDs opens their applications toward personalized medicine, a groundbreaking development in the AD treatment regimen. Through surface chemistry modification of CDs, it becomes possible to design personalized therapies considering genetics, molecular biology, as well as environmental factors pertaining to each individual patient. Concerning treating AD in a more diverse and heterogeneous population, CDs provide an adaptable, amenable platform to custom-tailor therapies to fit specific patient needs. Thus, future research should further explore the potential of CDs within the framework of personalised nanomedicine. AD is characterised by profound inter-individual heterogeneity driven by genetic, metabolic and inflammatory factors, necessitating therapeutic strategies tailored to specific patient profiles. Surface functionalisation of CDs with ligands such as antibodies, peptides, aptamers or small molecules could enable selective targeting of pathological biomarkers including Aβ, tau isoforms, or apolipoprotein E genotypes. By integrating patient-derived biomarker signatures, CDs can be engineered for enhanced specificity, improved pharmacodynamics, and minimised off-target interactions. Furthermore, multiplexed or dual-functional CDs combining diagnostic imaging and therapeutic delivery capabilities may facilitate precision monitoring of disease progression and treatment response. Such biomarker guided design would mark a critical step towards translating CDs from general neuroprotective agents into personalised nanotherapeutics aligned with the principles of precision medicine.¹⁹³

Considerations on the use of CDs in neurotherapeutics are still developing from a regulatory point of view. Although no CD-based therapies for AD have been approved by the US FDA or other regulatory agencies functioning worldwide, active research and emerging patent filings indicate heightened interest.¹⁹⁴ Challenges to regulatory approval include the absence of long-term safety data, lack of uniformity in synthesis protocols, and concerns regarding toxicity of these nanocarriers. Recent progress in green synthesis techniques, along with surface modification and biocompatibility testing, is paving the pathway for CD therapeutics.¹⁹⁵

The next frontier will likely involve the integration of AI, machine learning and advanced fabrication technologies to accelerate CD optimisation and clinical translation. AI-driven predictive modelling can correlate synthesis parameters, precursor composition, reaction conditions, and dopant ratios, with resultant physicochemical and biological behaviours enabling the rational design of safer, more effective nanodots. ML algorithms can further predict toxicity, biodistribution and protein-binding affinity, reducing experimental uncertainty and regulatory bottlenecks. Parallel developments in microfluidic and additive-manufacturing platforms promise scalable, reproducible production with precise control over particle size, surface charge and functionalisation density, aligning CD fabrication with industrial and regulatory standards.^196–199

Moreover, the use of CDs has been incorporated into smart delivery systems like thermo-responsive hydrogels, microneedle patches, and intranasal sprays to enhance non-invasive drug delivery systems.²⁰⁰ These innovations are designed to address the challenges of traditional AD therapeutics, including limited BBB access and quick enzyme degradation. However, a robust preclinical foundation does not appear to have enabled clinical translation of these fresh approaches. To this point, the majority of CD formulations have only undergone in vitro evaluation or small-animal model testing and very few have advanced to more rigorous in vivo validation stages. The absence of registered clinical trials involving CDs underscores the pressing need to translate promising laboratory findings into clinical applications. In AD research, CDs serve as a frontier technology innovatively bridging diagnostics with therapy. Their unique ability to penetrate the BBB, deliver targeted AD pharmacotherapy and provide real-time imaging capabilities, along with neuroprotective properties, make CDs invaluable candidates for multi-targeted intervention against AD.

As research is advancing, the capabilities of these nanocarriers have become the centre of attraction for the multidisciplinary researchers across the world, with hope that CDs will transform the management of AD soon. With continued understanding of their applications and potential, chronic neurodegenerative disorders like AD, which cripples millions by mainly affecting their quality of life, could be managed more effectively through such highly efficient CDs.

9. Conclusion

CDs have garnered significant attention in recent years as a popular nanoplatform across various ailments owing to their ultrasmall size, tunable surface chemistry and excellent biocompatibility. They can overcome several key challenges that hinder the traditional therapy of AD, such as the BBB, which prevents drugs from accumulating in the brain, and the absence of interventions that alter the progress of the diseases rather than just affording symptomatic relief. Recent studies highlight the unique potential of CDs in crossing the BBB and simultaneously targeting the multiple pathological hallmarks of AD, including Aβ aggregation, tau hyperphosphorylation, oxidative stress and neuroinflammation. These targeted approaches help in overcoming the challenges associated with traditional AD therapy. While the traditional formulations fail to reach the brain in the desired therapeutic range, CD based systems cross the BBB to exert their effect directly at the molecular level.

However, there are still several constraints and challenges that need to be addressed in order to fully realize the potential of CDs. While significant number of studies report the use of CDs for inhibiting Aβ, exploration of tau pathology remains comparatively limited and is still in its infancy. In addition to this, other hypotheses such as the cholinergic hypothesis, glutamate excitotoxicity and the impaired autophagy also need to be further explored with respect to CDs. Research evidence is additionally limited by the investigation being cell based and at the invertebrate level, warranting further evaluation in rodent models and higher. There are also translation concerns that need to be addressed such as establishing the long-term safety and choosing appropriate routes of administration. Despite these significant strides, CDs have not been able to be clinically translated due to challenges such as incomplete mechanistic understanding of CDs and biological interactions, limited validation in mammalian models and lack of standardized safety among regulatory frameworks. Despite these challenges, the multifunctionality and adaptability of CDs place them at the frontier of next generation nanotherapeutics for AD. Focused efforts are required to generate comprehensive mechanistic and translational data to realize the full potential of CDs in addressing the unmet clinical need of neurodegenerative disease treatment.

Conflicts of interest

There are no conflicts to declare.

Data availability

No primary research results, software or code have been included and no new data were generated or analysed as part of this review.

Acknowledgements

The authors would like to acknowledge BioRender for the graphical abstract and Fig. 1–3. Figures were created using BioRender under an academic publication license. The CSIR-CDRI communication number for this manuscript is 11086.

References

1. X. Xu, R. Ray, Y. Gu, H. J. Ploehn, L. Gearheart, K. Raker and W. A. Scrivens, Electrophoretic analysis and purification of fluorescent single-walled carbon nanotube fragments, J. Am. Chem. Soc., 2004, 126, 12736–12737,  DOI:10.1021/ja040082h.
2. Y. P. Sun, B. Zhou, Y. Lin, W. Wang, K. A. S. Fernando, P. Pathak, M. J. Meziani, B. A. Harruff, X. Wang, H. Wang, P. G. Luo, H. Yang, M. E. Kose, B. Chen, L. M. Veca and S. Y. Xie, Quantum-sized carbon dots for bright and colorful photoluminescence, J. Am. Chem. Soc., 2006, 128, 7756–7757,  DOI:10.1021/ja062677d.
3. L. Zuo, B. T. Hemmelgarn, C. C. Chuang and T. M. Best, The Role of Oxidative Stress-Induced Epigenetic Alterations in Amyloid-β Production in Alzheimer's Disease, Oxid. Med. Cell. Longevity, 2015, 604658,  DOI:10.1155/2015/604658.
4. K. J. Mintz, M. Bartoli, M. Rovere, Y. Zhou, S. D. Hettiarachchi, S. Paudyal, J. Chen, J. B. Domena, P. Y. Liyanage, R. Sampson, D. Khadka, R. R. Pandey, S. Huang, C. C. Chusuei, A. Tagliaferro and R. M. Leblanc, A deep investigation into the structure of carbon dots, Carbon, 2021, 173, 433–447,  DOI:10.1016/j.carbon.2020.11.017.
5. A. Tomskaya, I. P. Asanov, I. Yushina, M. I. Rakhmanova and S. Smagulova, Optical properties of tricarboxylic acid-derived carbon dots, ACS Omega, 2022, 7, 44093–44102,  DOI:10.1021/acsomega.2c05503.
6. Y. Wang and A. Hu, Carbon quantum dots: Synthesis, properties and applications, J. Mater. Chem. C, 2014, 2, 6921–6939,  10.1039/c4tc00988f.
7. S. Elkun, Green synthesis of fluorescent N-doped carbon quantum dots from castor seeds and their applications in cell imaging and pH sensing, Sci. Rep., 2024, 1–24.
8. J. Qi, R. Zhang, X. Liu, Y. Liu, Q. Zhang, H. Cheng, R. Li, L. Wang, X. Wu and B. Li, Carbon Dots as Advanced Drug-Delivery Nanoplatforms for Antiinflammatory, Antibacterial, and Anticancer Applications: A Review, ACS Appl. Nano Mater., 2023, 6, 9071–9084,  DOI:10.1021/acsanm.3c01207.
9. F. Kazeminava, S. Javanbakht, Z. Latifi, M. Rasoulzadehzali, M. Abbaszadeh, B. Alimohammadzadeh, M. Mahdipour, A. Fattahi, H. Hamishehkar, Z. Adibag and M. Nouri, Ultrasound-assisted encapsulating folic acid-based carbon quantum dots within breast cancer cell-derived exosomes as a co-receptors-mediated anticancer nanocarrier for enhanced breast cancer therapy, Sci. Rep., 2024, 14, 1–12,  DOI:10.1038/s41598-024-67934-6.
10. H. Kaurav, D. Verma, A. Bansal, D. N. Kapoor and S. Sheth, Progress in drug delivery and diagnostic applications of carbon dots: a systematic review, Front. Chem., 2023, 11, 1–22,  DOI:10.3389/fchem.2023.1227843.
11. S. Lu, S. Guo, P. Xu, X. Li, Y. Zhao, W. Gu and M. Xue, Hydrothermal synthesis of nitrogen-doped carbon dots with real-time live-cell imaging and blood-brain barrier penetration capabilities, Int. J. Nanomed., 2016, 11, 6325–6336,  DOI:10.2147/IJN.S119252.
12. D. M. Wilson, M. R. Cookson, L. Van Den Bosch, H. Zetterberg, D. M. Holtzman and I. Dewachter, Hallmarks of neurodegenerative diseases, Cell, 2023, 186, 693–714,  DOI:10.1016/j.cell.2022.12.032.
13. R. Rana, S. Tripathi, K. Mishra, P. K. Yadav, P. N. Yadav and M. K. Chourasia, Neuronal Membrane-Coated Mesoporous Ceria Nanoparticles for Blood−Brain Barrier Crossing and Mitigation of Neurodegeneration, ACS Appl. Nano Mater., 2025, 8, 9686–9701,  DOI:10.1021/acsanm.5c00545.
14. WHO, A blueprint for dementia research, 2022. https://www.who.int/publications/i/item/9789240058248.
15. C. A. Lane, J. Hardy and J. M. Schott, Alzheimer's disease, Eur. J. Neurol., 2018, 25, 59–70,  DOI:10.1111/ene.13439.
16. S. Tripathi, U. Gupta, R. R. Ujjwal and A. K. Yadav, Nano-lipidic formulation and therapeutic strategies for Alzheimer's disease via intranasal route, J. Microencapsulation, 2021, 38, 572–593,  DOI:10.1080/02652048.2021.1986585.
17. C. Abdelnour, F. Agosta, M. Bozzali, B. Fougère, A. Iwata, R. Nilforooshan, L. T. Takada, F. Viñuela and M. Traber, Perspectives and challenges in patient stratification in Alzheimer's disease, Alzheimer's Res. Ther., 2022, 14, 112,  DOI:10.1186/s13195-022-01055-y.
18. J. Cummings, New approaches to symptomatic treatments for Alzheimer's disease, Mol. Neurodegener., 2021, 16, 2,  DOI:10.1186/s13024-021-00424-9.
19. A. Atri, The Alzheimer's Disease Clinical Spectrum: Diagnosis and Management, Med. Clin. North Am., 2019, 103, 263–293,  DOI:10.1016/j.mcna.2018.10.009.
20. N. Falgàs, C. M. Walsh, T. C. Neylan and L. T. Grinberg, Deepen into sleep and wake patterns across Alzheimer's disease phenotypes, Alzheimer's Dementia, 2021, 17, 1403–1406,  DOI:10.1002/alz.12304.
21. J. Graff-Radford, K. X. X. Yong, L. G. Apostolova, F. H. Bouwman, M. Carrillo, B. C. Dickerson, G. D. Rabinovici, J. M. Schott, D. T. Jones and M. E. Murray, New insights into atypical Alzheimer's disease in the era of biomarkers, Lancet Neurol., 2021, 20, 222–234,  DOI:10.1016/S1474-4422(20)30440-3.
22. T. Song, X. Song, C. Zhu, R. Patrick, M. Skurla, I. Santangelo, M. Green, D. Harper, B. Ren, B. P. Forester, D. Öngür and F. Du, Mitochondrial dysfunction, oxidative stress, neuroinflammation, and metabolic alterations in the progression of Alzheimer's disease: A meta-analysis of in vivo magnetic resonance spectroscopy studies, Ageing Res. Rev., 2021, 72, 101503,  DOI:10.1016/j.arr.2021.101503.
23. S. Gunes, Y. Aizawa, T. Sugashi, M. Sugimoto and P. P. Rodrigues, Biomarkers for Alzheimer's Disease in the Current State: A Narrative Review, Int. J. Mol. Sci, 2022, 23, 4962,  DOI:10.3390/ijms23094962.
24. A. P. Porsteinsson, R. S. Isaacson, S. Knox, M. N. Sabbagh and I. Rubino, Diagnosis of Early Alzheimer's Disease: Clinical Practice in 2021, J. Prev. Alzheimer's Dis., 2021, 8, 371–386,  DOI:10.14283/jpad.2021.23.
25. A. Lloret, D. Esteve, M.-A. Lloret, A. Cervera-Ferri, B. Lopez, M. Nepomuceno and P. Monllor, When Does Alzheimer's Disease Really Start? The Role of Biomarkers, Focus, 2021, 19, 355–364,  DOI:10.1176/appi.focus.19305.
26. T. Nedelec, B. Couvy-Duchesne, F. Monnet, T. Daly, M. Ansart, L. Gantzer, B. Lekens, S. Epelbaum, C. Dufouil and S. Durrleman, Identifying health conditions associated with Alzheimer's disease up to 15 years before diagnosis: an agnostic study of French and British health records, Lancet Digital Health, 2022, 4, e169–e178,  DOI:10.1016/S2589-7500(21)00275-2.
27. D. Wu, Q. Chen, X. Chen, F. Han, Z. Chen and Y. Wang, The blood–brain barrier: structure, regulation, and drug delivery, Signal Transduction Targeted Ther., 2023, 8, 217,  DOI:10.1038/s41392-023-01481-w.
28. J. Wu, H. Wu, F. Zhou, Y. Wang, C. Wang and J. Ji, Blood-brain barrier alterations as an initiator of brain metastasis from lung cancer: a new take on an old story, Cancer Gene Ther., 2025, 1–8,  DOI:10.1038/s41417-025-00916-6.
29. W. M. Pardridge, The blood-brain barrier: Bottleneck in brain drug development, NeuroRx, 2005, 2, 3–14,  DOI:10.1602/neurorx.2.1.3.
30. E. G. Knox, M. R. Aburto, G. Clarke, J. F. Cryan and C. M. O’Driscoll, The blood-brain barrier in aging and neurodegeneration, Mol. Psychiatry, 2022, 27, 2659–2673,  DOI:10.1038/s41380-022-01511-z.
31. A. S. Hanafy, D. Dietrich, G. Fricker and A. Lamprecht, Blood-brain barrier models: Rationale for selection, Adv. Drug Delivery Rev., 2021, 176, 113859,  DOI:10.1016/j.addr.2021.113859.
32. J. Schaffenrath, T. Wyss, L. He, E. J. Rushing, M. Delorenzi, F. Vasella, L. Regli, M. C. Neidert and A. Keller, Blood-brain barrier alterations in human brain tumors revealed by genome-wide transcriptomic profiling, Neuro-Oncology, 2021, 23, 2095–2106,  DOI:10.1093/neuonc/noab022.
33. X. Jiang, A. V. Andjelkovic, L. Zhu, T. Yang, M. V. L. Bennett, J. Chen, R. F. Keep and Y. Shi, Blood-brain barrier dysfunction and recovery after ischemic stroke, Prog. Neurobiol., 2018, 163–164, 144–171,  DOI:10.1016/j.pneurobio.2017.10.001.
34. J. F. Deeken and W. Löscher, The blood-brain barrier and cancer: Transporters, treatment, and trojan horses, Clin. Cancer Res., 2007, 13, 1663–1674,  DOI:10.1158/1078-0432.CCR-06-2854.
35. Y. Zhou, Z. Peng, E. S. Seven and R. M. Leblanc, Crossing the blood-brain barrier with nanoparticles, J. Control. Release, 2018, 270, 290–303,  DOI:10.1016/j.jconrel.2017.12.015.
36. D. Elsori, G. Rashid, N. A. Khan, P. Sachdeva, R. Jindal, F. Kayenat, B. Sachdeva, M. A. Kamal, A. M. Babker and S. A. Fahmy, Nanotube breakthroughs: unveiling the potential of carbon nanotubes as a dual therapeutic arsenal for Alzheimer's disease and brain tumors, Front. Oncol., 2023, 13, 1–13,  DOI:10.3389/fonc.2023.1265347.
37. V. Ceña and P. Játiva, Nanoparticle crossing of blood-brain barrier: A road to new therapeutic approaches to central nervous system diseases, Nanomedicine, 2018, 13, 1513–1516,  DOI:10.2217/nnm-2018-0139.
38. E. S. Seven, Y. B. Seven, Y. Zhou, S. Poudel-Sharma, J. J. Diaz-Rucco, E. Kirbas Cilingir, G. S. Mitchell, J. D. Van Dyken and R. M. Leblanc, Crossing the blood–brain barrier with carbon dots: uptake mechanism and in vivo cargo delivery, Nanoscale Adv., 2021, 3, 3942–3953,  10.1039/d1na00145k.
39. S. Li, Z. Peng, J. Dallman, J. Baker, A. M. Othman, P. L. Blackwelder and R. M. Leblanc, Crossing the blood-brain-barrier with transferrin conjugated carbon dots: A zebrafish model study, Colloids Surf., B, 2016, 145, 251–256,  DOI:10.1016/j.colsurfb.2016.05.007.
40. S. Tajik, Z. Dourandish, K. Zhang, H. Beitollahi, Q. Van Le, H. W. Jang and M. Shokouhimehr, Carbon and graphene quantum dots: A review on syntheses, characterization, biological and sensing applications for neurotransmitter determination, RSC Adv., 2020, 10, 15406–15429,  10.1039/d0ra00799d.
41. C. O. Kappe, Controlled microwave heating in modern organic synthesis, Angew. Chem., Int. Ed. ( 2004) DOI:10.1002/anie.200400655.
42. F. Guo, Q. Li, X. Zhang, Y. Liu, J. Jiang, S. Cheng, S. Yu, X. Zhang, F. Liu, Y. Li, G. Rose and H. Zhang, Applications of Carbon Dots for the Treatment of Alzheimer's Disease, Int. J. Nanomed., 2022, 17, 6621–6638,  DOI:10.2147/IJN.S388030.
43. R. Howard, R. McShane, J. Lindesay, C. Ritchie, A. Baldwin, R. Barber, A. Burns, T. Dening, D. Findlay, C. Holmes, R. Jones, R. Jones, I. McKeith, A. Macharouthu, J. O’Brien, B. Sheehan, E. Juszczak, C. Katona, R. Hills, M. Knapp, C. Ballard, R. G. Brown, S. Banerjee, J. Adams, T. Johnson, P. Bentham and P. P. J. Phillips, Nursing home placement in the Donepezil and Memantine in Moderate to Severe Alzheimer's Disease (DOMINO-AD) trial: Secondary and post-hoc analyses, Lancet Neurol., 2015, 366, 893–903,  DOI:10.1016/S1474-4422(15)00258-6.
44. K. Theofilatos, N. Pavlopoulou, C. Papasavvas, S. Likothanassis, C. Dimitrakopoulos, E. Georgopoulos, C. Moschopoulos and S. Mavroudi, Predicting protein complexes from weighted protein-protein interaction graphs with a novel unsupervised methodology: Evolutionary enhanced Markov clustering, Artif. Intell. Med., 2015, 63, 181–189,  DOI:10.1016/j.artmed.2014.12.012.
45. M. W. Bondi, E. C. Edmonds and D. P. Salmon, Alzheimer's disease: Past, present, and future, J. Int. Neuropsychol. Soc, 2017, 23, 818–831,  DOI:10.1017/S135561771700100X.
46. B.S. Makin, Dementia treatment strives for new heights, (n.d.).
47. C. H. van Dyck, C. J. Swanson, P. Aisen, R. J. Bateman, C. Chen, M. Gee, M. Kanekiyo, D. Li, L. Reyderman, S. Cohen, L. Froelich, S. Katayama, M. Sabbagh, B. Vellas, D. Watson, S. Dhadda, M. Irizarry, L. D. Kramer and T. Iwatsubo, Lecanemab in early alzheimer’s disease. supplementary data, N. Engl. J. Med., 2022, 388, 9–21.
48. J. R. Sims, J. A. Zimmer, C. D. Evans, M. Lu, P. Ardayfio, J. D. Sparks, A. M. Wessels, S. Shcherbinin, H. Wang, E. S. Monkul Nery, E. C. Collins, P. Solomon, S. Salloway, L. G. Apostolova, O. Hansson, C. Ritchie, D. A. Brooks, M. Mintun and D. M. Skovronsky, Donanemab in Early Symptomatic Alzheimer Disease: The TRAILBLAZER-ALZ 2 Randomized Clinical Trial, JAMA, 2023, 330, 512–527,  DOI:10.1001/jama.2023.13239.
49. J. Zhang, Y. Zhang, J. Wang, Y. Xia, J. Zhang and L. Chen, Recent advances in Alzheimer's disease: Mechanisms, clinical trials and new drug development strategies, Signal Transduct. Target. Ther., 2024, 9, 211,  DOI:10.1038/s41392-024-01911-3.
50. M. A. Busche and B. T. Hyman, Synergy between amyloid-β and tau in Alzheimer's disease, Nat. Neurosci., 2020, 23, 1183–1193,  DOI:10.1038/s41593-020-0687-6.
51. N. Liu, X. Liang, Y. Chen and L. Xie, Recent trends in treatment strategies for Alzheimer's disease and the challenges: A topical advancement, Ageing Res. Rev., 2024, 94, 102199,  DOI:10.1016/j.arr.2024.102199.
52. R. Daneman, L. Zhou, D. Agalliu, J. D. Cahoy, A. Kaushal and B. A. Barres, The mouse blood-brain barrier transcriptome: A new resource for understanding the development and function of brain endothelial cells, PLoS One, 2010, 5, e13741,  DOI:10.1371/journal.pone.0013741.
53. A. Singh and S. C. Vellapandian, Structure of the Blood Brain Barrier and its Role in the Transporters for the Movement of Substrates across the Barriers, Curr. Drug Metab., 2023, 24, 250–269,  DOI:10.2174/1389200224666230608110349.
54. J. Correale and A. Villa, Cellular elements of the blood-brain barrier, Neurochem. Res., 2009, 34, 2067–2077,  DOI:10.1007/s11064-009-0081-y.
55. Z. Cai, P. F. Qiao, C. Q. Wan, M. Cai, N. K. Zhou and Q. Li, Role of Blood-Brain Barrier in Alzheimer's Disease, J. Alzheimer's Dis, 2018, 63, 1223–1234,  DOI:10.3233/JAD-180098.
56. E. M. Rhea and W. A. Banks, Role of the Blood-Brain Barrier in Central Nervous System Insulin Resistance, Front. Neurosci., 2019, 13, 521,  DOI:10.3389/fnins.2019.00521.
57. C. Toader, C. P. Tataru, O. Munteanu, M. Serban, R. A. Covache-Busuioc, A. V. Ciurea and M. Enyedi, Decoding Neurodegeneration: A Review of Molecular Mechanisms and Therapeutic Advances in Alzheimer's, Parkinson's, and ALS, Int. J. Mol. Sci., 2024, 25, 1–63,  DOI:10.3390/ijms252312613.
58. R. Dhariwal, M. Jain, Y. R. Mir, A. Singh, B. Jain, P. Kumar, M. Tariq, D. Verma, K. Deshmukh, V. K. Yadav and T. Malik, Targeted drug delivery in neurodegenerative diseases: the role of nanotechnology, Front. Med., 2025, 12, 1–19,  DOI:10.3389/fmed.2025.1522223.
59. V. A. Sundaram, Nanoparticles for overcoming blood-brain barrier challenges in neurodegenerative illness, 4 ( 2025) DOI:10.53388/BMEC2025022.Executive.
60. C. Sharma, H. Woo and S. R. Kim, Addressing Blood–Brain Barrier Impairment in Alzheimer's Disease, Biomedicines, 2022, 10, 742,  DOI:10.3390/biomedicines10040742.
61. A. E. Alkhalifa, N. F. Al-Ghraiybah, J. Odum, J. G. Shunnarah, N. Austin and A. Kaddoumi, Blood–Brain Barrier Breakdown in Alzheimer's Disease: Mechanisms and Targeted Strategies, Int. J. Mol. Sci., 2023, 24, 16288,  DOI:10.3390/ijms242216288.
62. S. Yu, X. Chen, T. Yang, J. Cheng, E. Liu, L. Jiang, M. Song, H. Shu and Y. Ma, Revealing the mechanisms of blood-brain barrier in chronic neurodegenerative disease: An opportunity for therapeutic intervention, Rev. Neurosci., 2024, 35, 895–916,  DOI:10.1515/revneuro-2024-0040.
63. Z. Huang, L. W. Wong, Y. Su, X. Huang, N. Wang, H. Chen and C. Yi, Blood-brain barrier integrity in the pathogenesis of Alzheimer's disease, Front. Neuroendocrinol., 2020, 59, 100857,  DOI:10.1016/j.yfrne.2020.100857.
64. A. R. Rezai, P. F. D’Haese, V. Finomore, J. Carpenter, M. Ranjan, K. Wilhelmsen, R. I. Mehta, P. Wang, U. Najib, C. Vieira Ligo Teixeira, T. Arsiwala, A. Tarabishy, P. Tirumalai, D. O. Claassen, S. Hodder and M. W. Haut, Ultrasound Blood–Brain Barrier Opening and Aducanumab in Alzheimer's Disease, N. Engl. J. Med., 2024, 390, 55–62,  DOI:10.1056/nejmoa2308719.
65. X. Yao, Improving brain penetration using elacridara P-glycoprotein and BCRP inhibitor, Theory Nat. Sci., 2024, 29, 50–62,  DOI:10.54254/2753-8818/29/20240729.
66. R. P. Dash, R. Jayachandra Babu and N. R. Srinivas, Therapeutic Potential and Utility of Elacridar with Respect to P-glycoprotein Inhibition: An Insight from the Published In Vitro, Preclinical and Clinical Studies, Eur. J. Drug Metab. Pharmacokinet., 2017, 42, 915–933,  DOI:10.1007/s13318-017-0411-4.
67. R. Kallem, C. P. Kulkarni, D. Patel, M. Thakur, M. Sinz, S. P. Singh, S. Shahe Mahammad and S. Mandlekar, A Simplified Protocol Employing Elacridar in Rodents: A Screening Model in Drug Discovery to Assess P-gp Mediated Efflux at the Blood Brain Barrier, Drug Metab. Lett., 2015, 6, 134–144,  DOI:10.2174/1872312811206020134.
68. R. I. Mehta, J. S. Carpenter, R. I. Mehta, M. W. Haut, P. Wang, M. Ranjan, U. Najib, P. F. D’Haese and A. R. Rezai, Ultrasound-mediated blood–brain barrier opening uncovers an intracerebral perivenous fluid network in persons with Alzheimer's disease, Fluids Barriers CNS, 2023, 20, 46,  DOI:10.1186/s12987-023-00447-y.
69. S. N. El-Helaly, A. A. Elbary, M. A. Kassem and M. A. El-Nabarawi, Electrosteric stealth rivastigmine loaded liposomes for brain targeting: Preparation, characterization, ex vivo, bio-distribution and in vivo pharmacokinetic studies, Drug Delivery, 2017, 24, 692–700,  DOI:10.1080/10717544.2017.1309476.
70. C. S. Musaeus, H. S. Gleerup, P. Høgh, G. Waldemar, S. G. Hasselbalch and A. H. Simonsen, Cerebrospinal Fluid/Plasma Albumin Ratio as a Biomarker for Blood-Brain Barrier Impairment Across Neurodegenerative Dementias, J. Alzheimer's Dis., 2020, 75, 429–436,  DOI:10.3233/JAD-200168.
71. S. E. J. Paton, J. L. Solano, F. Coulombe-Rozon, M. Lebel and C. Menard, Barrier–environment interactions along the gut–brain axis and their influence on cognition and behaviour throughout the lifespan, J. Psychiatry Neurosci., 2023, 48, E190–E208,  DOI:10.1503/jpn.220218.
72. S. Liebner, M. Corada, T. Bangsow, J. Babbage, A. Taddei, C. J. Czupalla, M. Reis, A. Felici, H. Wolburg, M. Fruttiger, M. M. Taketo, H. Von Melchner, K. H. Plate, H. Gerhardt and E. Dejana, Wnt/β-catenin signaling controls development of the blood - brain barrier, J. Cell Biol., 2008, 183, 409–417,  DOI:10.1083/jcb.200806024.
73. Y. Yan, J. Gong, J. Chen, Z. Zeng, W. Huang, K. Pu, J. Liu and P. Chen, Recent Advances on Graphene Quantum Dots: From Chemistry and Physics to Applications, Adv. Mater., 2019, 31, e1808283,  DOI:10.1002/adma.201808283.
74. C. Hu, M. Li, J. Qiu and Y. P. Sun, Design and fabrication of carbon dots for energy conversion and storage, Chem. Soc. Rev., 2019, 48, 2315–2337,  10.1039/c8cs00750k.
75. M. L. Liu, B. Bin Chen, C. M. Li and C. Z. Huang, Carbon dots: Synthesis, formation mechanism, fluorescence origin and sensing applications, Green Chem., 2019, 21, 449–471,  10.1039/c8gc02736f.
76. F. Yuan, Y. K. Wang, G. Sharma, Y. Dong, X. Zheng, P. Li, A. Johnston, G. Bappi, J. Z. Fan, H. Kung, B. Chen, M. I. Saidaminov, K. Singh, O. Voznyy, O. M. Bakr, Z. H. Lu and E. H. Sargent, Bright high-colour-purity deep-blue carbon dot light-emitting diodes via efficient edge amination, Nat. Photonics, 2020, 14, 171–176,  DOI:10.1038/s41566-019-0557-5.
77. A. B. Bourlinos, A. Stassinopoulos, D. Anglos, R. Zboril, M. Karakassides and E. P. Giannelis, Surface functionalized carbogenic quantum dots, Small, 2008, 4, 455–458,  DOI:10.1002/smll.200700578.
78. S. Zhu, Y. Song, J. Shao, X. Zhao and B. Yang, Non-conjugated polymer dots with crosslink-enhanced emission in the absence of fluorophore units, Angew. Chem., Int. Ed., 2015, 54, 14626–14637,  DOI:10.1002/anie.201504951.
79. S. Zhu, J. Zhang, C. Qiao, S. Tang, Y. Li, W. Yuan, B. Li, L. Tian, F. Liu, R. Hu, H. Gao, H. Wei, H. Zhang, H. Sun and B. Yang, Strongly green-photoluminescent graphene quantum dots for bioimaging applications, Chem. Commun., 2011, 47, 6858–6860,  10.1039/c1cc11122a.
80. L. Li, G. Wu, G. Yang, J. Peng, J. Zhao and J. J. Zhu, Focusing on luminescent graphene quantum dots: Current status and future perspectives, Nanoscale, 2013, 5, 4015–4039,  10.1039/c3nr33849e.
81. D. Pan, J. Zhang, Z. Li and M. Wu, Hydrothermal route for cutting graphene sheets into blue-luminescent graphene quantum dots, Adv. Mater., 2010, 22, 734–738,  DOI:10.1002/adma.200902825.
82. J. Peng, W. Gao, B. K. Gupta, Z. Liu, R. Romero-Aburto, L. Ge, L. Song, L. B. Alemany, X. Zhan, G. Gao, S. A. Vithayathil, B. A. Kaipparettu, A. A. Marti, T. Hayashi, J. J. Zhu and P. M. Ajayan, Graphene quantum dots derived from carbon fibers, Nano Lett., 2012, 12, 844–849,  DOI:10.1021/nl2038979.
83. S. Tao, S. Lu, Y. Geng, S. Zhu, S. A. T. Redfern, Y. Song, T. Feng, W. Xu and B. Yang, Design of Metal-Free Polymer Carbon Dots: A New Class of Room-Temperature Phosphorescent Materials, Angew. Chem., Int. Ed., 2018, 57, 2393–2398,  DOI:10.1002/anie.201712662.
84. C. Xia, S. Tao, S. Zhu, Y. Song, T. Feng, Q. Zeng, J. Liu and B. Yang, Hydrothermal addition polymerization for ultrahigh-yield carbonized polymer dots with room temperature phosphorescence via nanocomposite, Chem. – A Eur. J., 2018, 24, 11303–11308,  DOI:10.1002/chem.201802712.
85. X. Tong, S. Shi, C. Tong, A. Iftikhar, R. Long and Y. Zhu, Quantum/carbon dots-based fluorescent assays for enzyme activity, TrAC, Trends Anal. Chem., 2020, 131, 116008,  DOI:10.1016/j.trac.2020.116008.
86. A. Prakash, S. Yadav, P. S. Saxena and A. Srivastava, Development of folate-conjugated polypyrrole nanoparticles incorporated with nitrogen-doped carbon quantum dots for targeted bioimaging and photothermal therapy, Talanta, 2024, 278, 126528,  DOI:10.1016/j.talanta.2024.126528.
87. L. Ren, L. Wang, M. Rehberg, T. Stoeger, J. Zhang and S. Chen, Applications and Immunological Effects of Quantum Dots on Respiratory System, Front. Immunol., 2022, 12, 795232,  DOI:10.3389/fimmu.2021.795232.
88. S. Wang, C. Li, Y. Xia, S. Chen, J. Robert, X. Banquy, R. Huang, W. Qi, Z. He and R. Su, Nontoxic Black Phosphorus Quantum Dots Inhibit Insulin Amyloid Fibrillation at an Ultralow Concentration, IScience, 2020, 23, 101044,  DOI:10.1016/j.isci.2020.101044.
89. P. Jana and A. Dev, Carbon quantum dots: A promising nanocarrier for bioimaging and drug delivery in cancer, Mater. Today Commun., 2022, 32, 104068,  DOI:10.1016/j.mtcomm.2022.104068.
90. H. L. Yang, L. F. Bai, Z. R. Geng, H. Chen, L. T. Xu, Y. C. Xie, D. J. Wang, H. W. Gu and X. M. Wang, Carbon quantum dots: Preparation, optical properties, and biomedical applications, Mater. Today Adv., 2023, 18, 100376,  DOI:10.1016/j.mtadv.2023.100376.
91. R. de Boëver, J. R. Town, X. Li and J. P. Claverie, Carbon Dots for Carbon Dummies: The Quantum and The Molecular Questions Among Some Others, Chem. – A Eur. J., 2022, 28, e202200748,  DOI:10.1002/chem.202200748.
92. Y. Liu, H. Huang, W. Cao, B. Mao, Y. Liu and Z. Kang, Advances in carbon dots: From the perspective of traditional quantum dots, Mater. Chem. Front., 2020, 4, 1586–1613,  10.1039/d0qm00090f.
93. S. N. Baker and G. A. Baker, Luminescent carbon nanodots: Emergent nanolights, Angew. Chem., Int. Ed., 2010, 49, 6726–6744,  DOI:10.1002/anie.200906623.
94. L. Dordevic, F. Arcudi, M. Cacioppo and M. Prato, A multifunctional chemical toolbox to engineer carbon dots for biomedical and energy applications, Nat. Nanotechnol., 2022, 17, 112–130,  DOI:10.1038/s41565-021-01051-7.
95. J. Liu, R. Li and B. Yang, Carbon Dots: A New Type of Carbon-Based Nanomaterial with Wide Applications, ACS Cent. Sci., 2020, 6, 2179–2195,  DOI:10.1021/acscentsci.0c01306.
96. J. Li, S. Yang, Y. Deng, P. Chai, Y. Yang, X. He, X. Xie, Z. Kang, G. Ding, H. Zhou and X. Fan, Emancipating Target-Functionalized Carbon Dots from Autophagy Vesicles for a Novel Visualized Tumor Therapy, Adv. Funct. Mater., 2018, 28, 1800881,  DOI:10.1002/adfm.201800881.
97. S. Y. Sung, Y. L. Su, W. Cheng, P. F. Hu, C. S. Chiang, W. T. Chen and S. H. Hu, Graphene Quantum Dots-Mediated Theranostic Penetrative Delivery of Drug and Photolytics in Deep Tumors by Targeted Biomimetic Nanosponges, Nano Lett., 2019, 19, 69–81,  DOI:10.1021/acs.nanolett.8b03249.
98. S. Li, W. Su, H. Wu, T. Yuan, C. Yuan, J. Liu, G. Deng, X. Gao, Z. Chen, Y. Bao, F. Yuan, S. Zhou, H. Tan, Y. Li, X. Li, L. Fan, J. Zhu, A. T. Chen, F. Liu, Y. Zhou, M. Li, X. Zhai and J. Zhou, Targeted tumour theranostics in mice via carbon quantum dots structurally mimicking large amino acids, Nat. Biomed. Eng., 2020, 4, 704–716,  DOI:10.1038/s41551-020-0540-y.
99. P. Gao, S. Liu, Y. Su, M. Zheng and Z. Xie, Fluorine-Doped Carbon Dots with Intrinsic Nucleus-Targeting Ability for Drug and Dye Delivery, Bioconjugate Chem., 2020, 31, 646–655,  DOI:10.1021/acs.bioconjchem.9b00801.
100. C. Scialabba, A. Sciortino, F. Messina, G. Buscarino, M. Cannas, G. Roscigno, G. Condorelli, G. Cavallaro, G. Giammona and N. Mauro, Highly Homogeneous Biotinylated Carbon Nanodots: Red-Emitting Nanoheaters as Theranostic Agents toward Precision Cancer Medicine, ACS Appl. Mater. Interfaces, 2019, 11, 19854–19866,  DOI:10.1021/acsami.9b04925.
101. J. Han and K. Na, Transfection of the TRAIL gene into human mesenchymal stem cells using biocompatible polyethyleneimine carbon dots for cancer gene therapy, J. Ind. Eng. Chem., 2019, 80, 722–728,  DOI:10.1016/j.jiec.2019.02.015.
102. S. Ghosh, K. Ghosal, S. A. Mohammad and K. Sarkar, Dendrimer functionalized carbon quantum dot for selective detection of breast cancer and gene therapy, Chem. Eng. J., 2019, 373, 468–484,  DOI:10.1016/j.cej.2019.05.023.
103. M. Zheng, S. Ruan, S. Liu, T. Sun, D. Qu, H. Zhao, Z. Xie, H. Gao, X. Jing and Z. Sun, Self-Targeting Fluorescent Carbon Dots for Diagnosis of Brain Cancer Cells, ACS Nano, 2015, 9, 11455–11461,  DOI:10.1021/acsnano.5b05575.
104. S. Li, Z. Peng, J. Dallman, J. Baker, A. M. Othman, P. L. Blackwelder and R. M. Leblanc, Crossing the blood-brain-barrier with transferrin conjugated carbon dots: A zebrafish model study, Colloids Surf., B, 2016, 145, 251–256,  DOI:10.1016/j.colsurfb.2016.05.007.
105. Z. Peng, S. Li, X. Han, A. O. Al-Youbi, A. S. Bashammakh, M. S. El-Shahawi and R. M. Leblanc, Determination of the composition, encapsulation efficiency and loading capacity in protein drug delivery systems using circular dichroism spectroscopy, Anal. Chim. Acta, 2016, 937, 113–118,  DOI:10.1016/j.aca.2016.08.014.
106. M. Zheng, S. Liu, J. Li, D. Qu, H. Zhao, X. Guan, X. Hu, Z. Xie, X. Jing and Z. Sun, Integrating oxaliplatin with highly luminescent carbon dots: An unprecedented theranostic agent for personalized medicine, Adv. Mater., 2014, 26, 3554–3560,  DOI:10.1002/adma.201306192.
107. P. Su, W. Pei, X. Wang, Y. Ma, Q. Jiang, J. Liang, S. Zhou, J. Zhao, J. Liu and G. Q. Lu, Exceptional Electrochemical HER Performance with Enhanced Electron Transfer between Ru Nanoparticles and Single Atoms Dispersed on a Carbon Substrate, Angew. Chem., Int. Ed., 2021, 60, 16044–16050,  DOI:10.1002/anie.202103557.
108. S. Y. Lim, W. Shen and Z. Gao, Carbon quantum dots and their applications, Chem. Soc. Rev., 2015, 44, 362–381,  10.1039/c4cs00269e.
109. K. J. Mintz, Y. Zhou and R. M. Leblanc, Recent development of carbon quantum dots regarding their optical properties, photoluminescence mechanism, and core structure, Nanoscale, 2019, 11, 4634–4652,  10.1039/c8nr10059d.
110. J. L. Lim, C. J. Lin, C. C. Huang and L. C. Chang, Curcumin-derived carbon quantum dots: Dual actions in mitigating tau hyperphosphorylation and amyloid beta aggregation, Colloids Surf., B, 2024, 234, 113676,  DOI:10.1016/j.colsurfb.2023.113676.
111. X. Han, Z. Jing, W. Wu, B. Zou, Z. Peng, P. Ren, A. Wikramanayake, Z. Lu and R. M. Leblanc, Biocompatible and blood-brain barrier permeable carbon dots for inhibition of Aβ fibrillation and toxicity, and BACE1 activity, Nanoscale, 2017, 9, 12862–12866,  10.1039/c7nr04352j.
112. A. Karagianni, N. G. Tsierkezos, M. Prato, M. Terrones and K. V. Kordatos, Application of carbon-based quantum dots in photodynamic therapy, Carbon, 2023, 203, 273–310,  DOI:10.1016/j.carbon.2022.11.026.
113. K. J. Mintz, G. Mercado, Y. Zhou, Y. Ji, S. D. Hettiarachchi, P. Y. Liyanage, R. R. Pandey, C. C. Chusuei, J. Dallman and R. M. Leblanc, Tryptophan carbon dots and their ability to cross the blood-brain barrier, Colloids Surf., B, 2019, 176, 488–493,  DOI:10.1016/j.colsurfb.2019.01.031.
114. Y. Zhou, P. Y. Liyanage, D. Devadoss, L. R. Rios Guevara, L. Cheng, R. M. Graham, H. S. Chand, A. O. Al-Youbi, A. S. Bashammakh, M. S. El-Shahawi and R. M. Leblanc, Nontoxic amphiphilic carbon dots as promising drug nanocarriers across the blood-brain barrier and inhibitors of β-amyloid, Nanoscale, 2019, 46, 22387–22397,  10.1039/c9nr08194a.
115. C. Araújo, R. O. Rodrigues, M. Bañobre-López, A. M. T. Silva and R. S. Ribeiro, Carbon Dots as a Fluorescent Nanosystem for Crossing the Blood-Brain Barrier with Plausible Application in Neurological Diseases, Pharmaceutics, 2025, 17, 477,  DOI:10.3390/pharmaceutics17040477.
116. S. Lu, S. Guo, P. Xu, X. Li, Y. Zhao, W. Gu and M. Xue, Hydrothermal synthesis of nitrogen-doped carbon dots with real-time live-cell imaging and blood-brain barrier penetration capabilities, Int. J. Nanomed., 2016, 11, 6325–6326,  DOI:10.2147/IJN.S119252.
117. I. J. Gómez, P. Křížková, A. Dolečková, L. Cardo, C. Wetzl, N. Pizúrová, M. Prato, J. Medalová and L. Zajíčková, Multifunctional graphene quantum dots: A therapeutic strategy for neurodegenerative diseases by regulating calcium influx, crossing the blood-brain barrier and inhibiting Aβ-protein aggregation, Appl. Mater. Today, 2024, 36, 102072,  DOI:10.1016/j.apmt.2024.102072.
118. S. Yang, Z. Chen, P. Zhou, J. Xia, T. Deng and C. Yu, Carbon dots based on endogenous nutrients with visible and NIR fluorescence to penetrate blood-brain barrier, Carbon, 2023, 202, 130–140,  DOI:10.1016/j.carbon.2022.10.067.
119. R. van der Kant, L. S. B. Goldstein and R. Ossenkoppele, Amyloid-β-independent regulators of tau pathology in Alzheimer disease, Nat. Rev. Neurosci., 2020, 21, 21–35,  DOI:10.1038/s41583-019-0240-3.
120. Y. Xie, Q. Liu, L. Zheng, B. T. Wang, X. Qu, J. Ni, Y. Zhang and X. Du, Se-Methylselenocysteine Ameliorates Neuropathology and Cognitive Deficits by Attenuating Oxidative Stress and Metal Dyshomeostasis in Alzheimer Model Mice, Mol. Nutr. Food Res., 2018, 62, e1800107,  DOI:10.1002/mnfr.201800107.
121. G. Son, B. Il Lee, Y. J. Chung and C. B. Park, Light-triggered dissociation of self-assembled β-amyloid aggregates into small, nontoxic fragments by ruthenium (II) complex, Acta Biomater., 2018, 67, 147–155,  DOI:10.1016/j.actbio.2017.11.048.
122. E. Asimakidou, J. K. S. Tan, J. Zeng and C. H. Lo, Blood–Brain Barrier-Targeting Nanoparticles: Biomaterial Properties and Biomedical Applications in Translational Neuroscience, Pharmaceuticals, 2024, 17, 612,  DOI:10.3390/ph17050612.
123. Z. Wei, X. Dong and Y. Sun, Quercetin-derived red emission carbon dots: A multifunctional theranostic nano-agent against Alzheimer's β-amyloid fibrillogenesis, Colloids Surf., B, 2024, 238, 113907,  DOI:10.1016/j.colsurfb.2024.113907.
124. W. Gao, W. Wang, X. Dong and Y. Sun, Nitrogen-Doped Carbonized Polymer Dots: A Potent Scavenger and Detector Targeting Alzheimer's β-Amyloid Plaques, Small, 2020, 16, e2002804,  DOI:10.1002/smll.202002804.
125. Y. J. Chung, B. Il Lee and C. B. Park, Multifunctional carbon dots as a therapeutic nanoagent for modulating Cu(ii)-mediated β-amyloid aggregation, Nanoscale, 2019, 11, 6297–6306,  10.1039/c9nr00473d.
126. K. Yan, C. Li, X. Zhu, Y. Zhang, G. Xiao and M. Xu, Modulating surface functional groups in carbon dots for enhanced inhibition of β -amyloid aggregation, ChemistrySelect, 2024, 202304300,  DOI:10.1002/slct.202304300.
127. X. Yin, H. Zhou, M. Zhang, J. Su, X. Wang, S. Li, Z. Yang, Z. Kang and R. Zhou, C3N nanodots inhibits Aβ peptides aggregation pathogenic path in Alzheimer's disease, Nat. Commun., 2023, 14, 5718,  DOI:10.1038/s41467-023-41489-y.
128. J. Min, H. Sarlus, S. Oasa and R. A. Harris, Thioflavin-T: application as a neuronal body and nucleolar stain and the blue light photo enhancement effect, Sci. Rep., 2024, 1–17.
129. N. J. Greenfield, Using circular dichroism spectra to estimate protein secondary structure, Nat. Protoc., 2007, 1, 2876–2890,  DOI:10.1038/nprot.2006.202.
130. F. C. Herrmann, Easy ultrastructural insight into the internal morphology of biological specimens by Atomic Force Microscopy, Sci. Rep., 2021, 1–12,  DOI:10.1038/s41598-021-89633-2.
131. X. Wang, Y. Li, L. Wei and L. Xiao, Direct visualization of β -amyloid fibrils with a self-powered imaging strategy through the generation of fluorescent tags with Pt nanozymes, Chem. Eng. J., 2023, 471, 144513,  DOI:10.1016/j.cej.2023.144513.
132. V. Upadhyay, A. Lucas, C. Patrick and K. M. G. Mallela, Isothermal titration calorimetry and surface plasmon resonance methods to probe protein – protein interactions, Methods, 2024, 225, 52–61,  DOI:10.1016/j.ymeth.2024.03.007.
133. W. Wang, Z. Liu, H. Cheng, M. Xu, Z. Du, W. Liu and C. Zhang, Cerium-doped carbon dots as dual-target agents against Alzheimer's β-amyloid fibrillogenesis and reactive oxygen species, Colloids Surf., B, 2025, 252, 114655,  DOI:10.1016/j.colsurfb.2025.114655.
134. P. Ye, L. Li, X. Qi, M. Chi, J. Liu and M. Xie, Macrophage membrane-encapsulated nitrogen-doped carbon quantum dot nanosystem for targeted treatment of Alzheimer's disease: Regulating metal ion homeostasis and photothermal removal of β-amyloid, J. Colloid Interface Sci., 2023, 650, 1749–1761,  DOI:10.1016/j.jcis.2023.07.132.
135. D. Pisa, R. Alonso, A. Juarranz, A. Rábano and L. Carrasco, Direct visualization of fungal infection in brains from patients with Alzheimer's disease, J. Alzheimer's Dis., 2015, 43, 613–624,  DOI:10.3233/JAD-141386.
136. S. S. Dominy, C. Lynch, F. Ermini, M. Benedyk, A. Marczyk, A. Konradi, M. Nguyen, U. Haditsch, D. Raha, C. Griffin, L. J. Holsinger, S. Arastu-Kapur, S. Kaba, A. Lee, M. I. Ryder, B. Potempa, P. Mydel, A. Hellvard, K. Adamowicz, H. Hasturk, G. D. Walker, E. C. Reynolds, R. L. M. Faull, M. A. Curtis, M. Dragunow and J. Potempa, Porphyromonas gingivalis in Alzheimer's disease brains: Evidence for disease causation and treatment with small-molecule inhibitors, Sci. Adv., 2019, 5, eaau3333,  DOI:10.1126/sciadv.aau3333.
137. Y. Wu, S. Du, J. L. Johnson, H. Y. Tung, C. T. Landers, Y. Liu, B. G. Seman, R. T. Wheeler, M. Costa-Mattioli, F. Kheradmand, H. Zheng and D. B. Corry, Microglia and amyloid precursor protein coordinate control of transient Candida cerebritis with memory deficits, Nat. Commun., 2019, 10, 58,  DOI:10.1038/s41467-018-07991-4.
138. C. Yan, C. Wang, X. Shao, Q. Shu, X. Hu, P. Guan, Y. Teng and Y. Cheng, Dual-targeted carbon-dot-drugs nanoassemblies for modulating Alzheimer's related amyloid-β aggregation and inhibiting fungal infection, Mater. Today Bio, 2021, 12, 100167,  DOI:10.1016/j.mtbio.2021.100167.
139. Y. Wang, C. Yan, Y. Qi, R. Zhao, Y. Wan, Z. Lyu, Y. Li, Z. Wang, C. Li, Y. Lin, Q. Chen, S. Ding and J. Shi, Harnessing multi-target nanosweepers inhibiting β-amyloid aggregation, scavenging reactive oxygen species and overcoming the blood brain barrier for rescuing Alzheimer's disease, Chem. Eng. J., 2025, 508, 161138,  DOI:10.1016/j.cej.2025.161138.
140. S. Tripathi, R. Rana, J. V. U. S. Chakradhar, K. Mishra, S. Jaiswal, M. Sethi, A. K. Tiwari and M. K. Chourasia, Simultaneous estimation of donepezil and quercetin using ultra high performance liquid chromatography: pharmaceutical and pharmacokinetic applications in Alzheimer's disease, Bioanalysis, 2025, 00, 1–11,  DOI:10.1080/17576180.2025.2518044.
141. X. Shao, T. Fan, C. Yan, X. Cao, C. Wang, X. Wang, P. Guan, L. Fan and X. Hu, Multifunctional selenium-doped carbon dots for modulating Alzheimer's disease related toxic ions, inhibiting amyloid aggregation and scavenging reactive oxygen species, Int. J. Biol. Macromol., 2025, 293, 139333,  DOI:10.1016/j.ijbiomac.2024.139333.
142. C. Wang, T. Hou, X. Shao, C. Wang, X. Wang, P. Guan, Y. Wu and X. Hu, Functionalized carbon dots with guanidine salt ionic liquid regulate oxidative damage and amyloid aggregation, Int. J. Biol. Macromol., 2025, 306, 141531,  DOI:10.1016/j.ijbiomac.2025.141531.
143. C. Yan, Y. Wang, Y. Ma, H. Liu, S. Tang, Y. Li, J. Shi, S. Ding and Z. Lyu, A multifunctional carbon quantum dot overcoming the BBB for modulating amyloid aggregation and scavenging reactive oxygen species, Mater. Today Chem., 2024, 40, 102222,  DOI:10.1016/j.mtchem.2024.102222.
144. H. Li, Y. Zhang, J. Ding, T. Wu, S. Cai, W. Zhang, R. Cai, C. Chen and R. Yang, Synthesis of carbon quantum dots for application of alleviating amyloid-β mediated neurotoxicity, Colloids Surf., B, 2022, 212, 112373,  DOI:10.1016/j.colsurfb.2022.112373.
145. J. Zhang, X. Yang, S. Wang, J. Dong, M. Zhang, M. Zhang and L. Chen, Metformin carbon dots enhance neurogenesis and neuroprotection in Alzheimer's disease: A potential nanomedicine approach, Mater. Today Bio, 2024, 29, 101347,  DOI:10.1016/j.mtbio.2024.101347.
146. D. Li, X. Wang, S. Wang, X. Song, L. Fang, Y. Zhang, X. Ba and S. Wang, Multifunctional carbon dots inhibit the amyloid fibrillation and scavenge free radicals, J. Mol. Struct., 2025, 1326, 141134,  DOI:10.1016/j.molstruc.2024.141134.
147. E. M. Mosalam, H. M. Abdel-Bar, A. I. Elberri, M. S. Abdallah, A. A. A. Zidan, H. A. Batakoushy and H. E. Abo Mansour, Enhanced neuroprotective effect of verapamil-loaded hyaluronic acid modified carbon quantum dots in an in-vitro model of amyloid-induced Alzheimer's disease, Int. J. Biol. Macromol., 2024, 275, 133742,  DOI:10.1016/j.ijbiomac.2024.133742.
148. Y. Pan, G. Hou, X. Wang, X. Ran, P. Liu and L. Guo, N, F-doped graphene quantum dots effectively inhibit the fibrillization of amyloid-beta peptide (1–42), Mater. Chem. Phys., 2023, 299, 127522,  DOI:10.1016/j.matchemphys.2023.127522.
149. X. Shao, M. Li, C. Yan, C. Wang, X. Wang, P. Guan, X. Hu and L. Fan, Photocatalytic, photothermal, and blood-brain barrier-permeable carbon nanodots: A potent multifunctional scavenger for β-amyloid plaque, Colloids Surf., B, 2025, 246, 114380,  DOI:10.1016/j.colsurfb.2024.114380.
150. Y. J. Chung, C. H. Lee, J. Lim, J. Jang, H. Kang and C. B. Park, Photomodulating Carbon Dots for Spatiotemporal Suppression of Alzheimer's β-Amyloid Aggregation, ACS Nano, 2020, 14, 16973–16983,  DOI:10.1021/acsnano.0c06078.
151. Y. Zhang, Y. Hong, F. Yang, Y. Yan, R. Zhao and M. Xie, TGN peptide and erythrocyte membrane dual-modified selenium-doped carbon quantum dots for multifaceted treatment of Alzheimer's disease, Chem. Eng. J., 2025, 514, 163340,  DOI:10.1016/j.cej.2025.163340.
152. T. Hou, Q. Yang, M. Ding, X. Wang, K. Mei, P. Guan, C. Wang and X. Hu, Blood-brain barrier permeable carbon nano-assemblies for amyloid-β clearance and neurotoxic attenuation, Colloids Surf., B, 2024, 244, 114182,  DOI:10.1016/j.colsurfb.2024.114182.
153. X. Lin, H. Zhang, W. Liu, X. Dong and Y. Sun, Methylene Blue-Doped Carbonized Polymer Dots: A Potent Photooxygenation Scavenger Targeting Alzheimer's β-Amyloid, ACS Appl. Mater. Interfaces, 2023, 15, 44062–44074,  DOI:10.1021/acsami.3c06948.
154. W. Zhang, N. Kandel, Y. Zhou, N. Smith, B. C. L. B. Ferreira, M. Perez, M. L. Claure, K. J. Mintz, C. Wang and R. M. Leblanc, Drug delivery of memantine with carbon dots for Alzheimer's disease: blood–brain barrier penetration and inhibition of tau aggregation, J. Colloid Interface Sci., 2022, 617, 20–31,  DOI:10.1016/j.jcis.2022.02.124.
155. Y. Zhou, N. Kandel, M. Bartoli, L. F. Serafim, A. E. ElMetwally, S. M. Falkenberg, X. E. Paredes, C. J. Nelson, N. Smith, E. Padovano, W. Zhang, K. J. Mintz, B. C. L. B. Ferreira, E. K. Cilingir, J. Chen, S. K. Shah, R. Prabhakar, A. Tagliaferro, C. Wang and R. M. Leblanc, Structure-activity relationship of carbon nitride dots in inhibiting Tau aggregation, Carbon, 2022, 193, 1–16,  DOI:10.1016/j.carbon.2022.03.021.
156. W. Zhang, N. Smith, Y. Zhou, C. M. McGee, M. Bartoli, S. Fu, J. Chen, J. B. Domena, A. Joji, H. Burr, G. Lv, E. K. Cilingir, S. Bedendo, M. L. Claure, A. Tagliaferro, D. Eliezer, E. A. Veliz, F. Zhang, C. Wang and R. M. Leblanc, Carbon dots as dual inhibitors of tau and amyloid-beta aggregation for the treatment of Alzheimer's disease, Acta Biomater., 2024, 183, 341–355,  DOI:10.1016/j.actbio.2024.06.001.
157. L. Bao, W. Luo, Q. Li, Y. Zhang, Z. Zhang, X. Li, L. Wang, J. Zhang, K. Huang, X. Yu and L. Xu, Chiral carbon dots based on ternary carbon sources: A multifunctional therapeutic agent for Cu2+-induced Alzheimer's disease, Carbon, 2024, 228, 119333,  DOI:10.1016/j.carbon.2024.119333.
158. W. Wang, X. Lin, X. Dong and Y. Sun, A multi-target theranostic nano-composite against Alzheimer's disease fabricated by conjugating carbon dots and triple-functionalized human serum albumin, Acta Biomater., 2022, 148, 298–309,  DOI:10.1016/j.actbio.2022.06.029.
159. J. Liu, M. Chi, L. Li, Y. Zhang and M. Xie, Erythrocyte membrane coated with nitrogen-doped quantum dots and polydopamine composite nano-system combined with photothermal treatment of Alzheimer's disease, J. Colloid Interface Sci., 2024, 663, 856–868,  DOI:10.1016/j.jcis.2024.02.219.
160. S. M. ElMorsy, D. A. Gutierrez, S. Valdez, J. Kumar, R. J. Aguilera, M. Noufal, H. Sarma, S. Chinnam and M. Narayan, Graphene acid quantum dots: A highly active multifunctional carbon nano material that intervene in the trajectory towards neurodegeneration, J. Colloid Interface Sci., 2024, 670, 357–363,  DOI:10.1016/j.jcis.2024.05.072.
161. M. Tabish, I. Malik, A. M. Alshahrani and M. Afzal, Detection of an oxidative stress metabolite associated with neurodegenerative diseases: effect of heteroatom doped antioxidant carbon dots, RSC Adv., 2025, 15, 8354–8366,  10.1039/d5ra00274e.
162. Q. Y. Li, X. Yu, X. Li, L. N. Bao, Y. Zhang, M. J. Xie, M. Jiang, Y. Q. Wang, K. Huang and L. Xu, Silicon−Carbon Dots-Loaded Mesoporous Silica Nanocomposites (mSiO2@SiCDs): An Efficient Dual Inhibitor of Cu2+-Mediated Oxidative Stress and Aβ Aggregation for Alzheimer's Disease, ACS Appl. Mater. Interfaces, 2023, 15, 54221–54233,  DOI:10.1021/ACSAMI.3C10053.
163. F. Guo, Q. Li, X. Zhang, Y. Liu, J. Jiang, S. Cheng, S. Yu, X. Zhang, F. Liu, Y. Li, G. Rose and H. Zhang, Applications of Carbon Dots for the Treatment of Alzheimer's Disease, Int. J. Nanomed., 2022, 17, 6621–6638,  DOI:10.2147/IJN.S388030.
164. Y. Hu, J. Cui, J. Sun, X. Liu, S. Gao, X. Mei, C. Wu and H. Tian, A novel biomimetic nanovesicle containing caffeic acid-coupled carbon quantum dots for the the treatment of Alzheimer's disease via nasal administration, J. Nanobiotechnol., 2024, 22, 642,  DOI:10.1186/s12951-024-02912-8.
165. A. Truskewycz, H. Yin, N. Halberg, D. T. H. Lai, A. S. Ball, V. K. Truong, A. M. Rybicka and I. Cole, Carbon Dot Therapeutic Platforms: Administration, Distribution, Metabolism, Excretion, Toxicity, and Therapeutic Potential, Small, 2022, 18, 2106342,  DOI:10.1002/smll.202106342.
166. J. Chen, D. Sun, H. Cui, C. Rao, L. Li, S. Guo, S. Yang, Y. Zhang and X. Cao, Toxic effects of carbon quantum dots on the gut-liver axis and gut microbiota in the common carp Cyprinus carpio, Environ. Sci.: Nano, 2022, 9, 173–188,  10.1039/d1en00651g.
167. H. Kuznietsova, A. Géloën, N. Dziubenko, A. Zaderko, S. Alekseev, V. Lysenko and V. Skryshevsky, In vitro and in vivo toxicity of carbon dots with different chemical compositions, Discovery Nano, 2023, 18, 111,  DOI:10.1186/s11671-023-03891-9.
168. N. Nimi, A. Saraswathy, S. S. Nazeer, N. Francis, S. J. Shenoy and R. S. Jayasree, Multifunctional hybrid nanoconstruct of zerovalent iron and carbon dots for magnetic resonance angiography and optical imaging: An In vivo study, Biomaterials, 2018, 171, 46–56,  DOI:10.1016/j.biomaterials.2018.04.012.
169. H. Wang, J. Shen, Y. Li, Z. Wei, G. Cao, Z. Gai, K. Hong, P. Banerjee and S. Zhou, Magnetic iron oxide-fluorescent carbon dots integrated nanoparticles for dual-modal imaging, near-infrared light-responsive drug carrier and photothermal therapy, Biomater. Sci., 2014, 2, 915–923,  10.1039/c3bm60297d.
170. Z. Zhang, C. Wu, J. Hu, C. Li, Y. Liu, B. Lei and M. Zheng, Recent Advances of Carbon Dots: Synthesis, Plants Applications, Prospects, and Challenges, ACS Appl. Bio Mater., 2025, 8, 935–961,  DOI:10.1021/acsabm.4c01785.
171. Y. Wang, H. Wu, Y. Guo, F. Li and H. Zhang, Carbon Dot-Based Nanoparticles: A Promising Therapeutic Approach for Glioblastoma, Int. J. Nanomed., 2025, 20, 7061–7092,  DOI:10.2147/IJN.S519733.
172. N. A. Pechnikova, K. Domvri, K. Porpodis, M. S. Istomina, A. V. Iaremenko and A. V. Yaremenko, Carbon Quantum Dots in Biomedical Applications: Advances, Challenges, and Future Prospects, Aggregate, 2024, 6, e707,  DOI:10.1002/agt2.707.
173. D. H. H. Nguyen, H. El-Ramady and J. Prokisch, Food safety aspects of carbon dots: a review, Environ. Chem. Lett., 2024, 23, 337–360,  DOI:10.1007/s10311-024-01779-3.
174. J. Allan, S. Belz, A. Hoeveler, M. Hugas, H. Okuda, A. Patri, H. Rauscher, P. Silva, W. Slikker, B. Sokull-Kluettgen, W. Tong and E. Anklam, Regulatory landscape of nanotechnology and nanoplastics from a global perspective, Regul. Toxicol. Pharmacol., 2021, 122, 104885,  DOI:10.1016/j.yrtph.2021.104885.
175. M. Tavan, Z. Yousefian, Z. Bakhtiar, M. Rahmandoust and M. H. Mirjalili, Carbon quantum dots: Multifunctional fluorescent nanomaterials for sustainable advances in biomedicine and agriculture, Ind. Crops Prod., 2025, 231, 121207,  DOI:10.1016/j.indcrop.2025.121207.
176. J. Liao, Y. Yao, C. H. Lee, Y. Wu and P. Li, In vivo biodistribution, clearance, and biocompatibility of multiple carbon dots containing nanoparticles for biomedical application, Pharmaceutics, 2021, 13, 1872,  DOI:10.3390/pharmaceutics13111872.
177. C. Li, J. Huang, L. Yuan, W. Xie, Y. Ying, C. Li, Y. Yu, Y. Pan, W. Qu, H. Hao, S. A. Algharib, D. Chen and S. Xie, Recent progress of emitting long-wavelength carbon dots and their merits for visualization tracking, target delivery and theranostics, Theranostics, 2023, 13, 2165–2182,  DOI:10.7150/thno.80579.
178. G. F. Makhaeva, N. V. Kovaleva, N. P. Boltneva, S. V. Lushchekina, T. Y. Astakhova, E. V. Rudakova, A. N. Proshin, I. V. Serkov, E. V. Radchenko, V. A. Palyulin, S. O. Bachurin and R. J. Richardson, New Hybrids of 4-Amino-2,3-polymethylene-quinoline and p-Tolylsulfonamide as Dual Inhibitors of Acetyl- And Butyrylcholinesterase and Potential Multifunctional Agents for Alzheimer's Disease Treatment, Molecules, 2020, 25, 3915,  DOI:10.3390/molecules25173915.
179. A. Gazzi, L. Fusco, M. Orecchioni, S. Ferrari, G. Franzoni, J. S. Yan, M. Rieckher, G. Peng, M. A. Lucherelli, I. A. Vacchi, N. Do Quyen Chau, A. Criado, A. Istif, D. Mancino, A. Dominguez, H. Eckert, E. Vázquez, T. Da Ros, P. Nicolussi, V. Palermo, B. Schumacher, G. Cuniberti, Y. Mai, C. Clementi, M. Pasquali, X. Feng, K. Kostarelos, A. Yilmazer, D. Bedognetti, B. Fadeel, M. Prato, A. Bianco and L. G. Delogu, Graphene, other carbon nanomaterials and the immune system: Toward nanoimmunity-by-design, J. Phys Mater., 2020, 3, 034005,  DOI:10.1088/2515-7639/ab9317.
180. J. Paradise, Regulating nanomedicine at the food and drug administration, AMA J. Ethics, 2019, 21, E347–E355,  DOI:10.1001/amajethics.2019.347.
181. D. A. Dri, F. Rinaldi, M. Carafa and C. Marianecci, Nanomedicines and nanocarriers in clinical trials: surfing through regulatory requirements and physico-chemical critical quality attributes, Drug Delivery Transl. Res., 2023, 13, 757–769,  DOI:10.1007/s13346-022-01262-y.
182. J. A. Hutt, B. T. Assaf, B. Bolon, J. Cavagnaro, E. Galbreath, B. Grubor, L. M. Kattenhorn, A. Romeike and L. O. Whiteley, Scientific and Regulatory Policy Committee Points to Consider: Nonclinical Research and Development of In Vivo Gene Therapy Products, Emphasizing Adeno-Associated Virus Vectors, Toxicol. Pathol., 2022, 50, 118–146,  DOI:10.1177/01926233211041962.
183. X. Lin and T. Chen, A Review of in vivo Toxicity of Quantum Dots in Animal Models, Int. J. Nanomed., 2023, 18, 8143–8168,  DOI:10.2147/IJN.S434842.
184. B. D. Mansuriya and Z. Altintas, Carbon dots: Classification, properties, synthesis, characterization, and applications in health care-an updated review (2018–2021), Nanomaterials, 2021, 11, 2525,  DOI:10.3390/nano11102525.
185. Y. Hu, O. Seivert, Y. Tang, H. E. Karahan and A. Bianco, Carbon Dot Synthesis and Purification: Trends, Challenges and Recommendations, Angew. Chem., Int. Ed., 2024, 63, e202412341,  DOI:10.1002/anie.202412341.
186. R. Maheshwari, D. Kapoor, S. Polaka, S. Bhattacharya and B. Prajapati, Roadmap for Commercial Nanomedicine Development: Integrating Quality by Design Principles with Pharmaceutical Nanotechnology, Mol. Pharm., 2025, 22, 4337–4372,  DOI:10.1021/acs.molpharmaceut.5c00056.
187. M. Rawal, A. Singh and M. M. Amiji, Quality-by-Design Concepts to Improve Nanotechnology-Based Drug Development, Pharm. Res., 2019, 36, 153,  DOI:10.1007/s11095-019-2692-6.
188. R. M. Pallares, F. Kiessling and T. Lammers, Clinical translation of quantum dots, Nanomedicine, 2024, 19, 2433–2435,  DOI:10.1080/17435889.2024.2405458.
189. B. Fadeel, L. Farcal, B. Hardy, S. Vázquez-Campos, D. Hristozov, A. Marcomini, I. Lynch, E. Valsami-Jones, H. Alenius and K. Savolainen, Advanced tools for the safety assessment of nanomaterials, Nat. Nanotechnol, 2018, 15, 551–560,  DOI:10.1038/s41565-018-0185-0.
190. S. Banerjee, S. Mandal, S. Singh, A. Sen and P. Das, Machine learning-guided fabrication of carbon dot-pepsin nano-conjugates for enhanced bioimaging, synergistic drug delivery, and visible light-induced photosensitization, Nanoscale, 2025, 14233–14247,  10.1039/d5nr00752f.
191. O. for C. Rights (OCR), HIPAA for Professionals, HHS.Gov 2003 (2015) 2004–2006. https://www.hhs.gov/hipaa/for-professionals/index.html%0Ahttps://www.hhs.gov/hipaa/for-professionals/index.html%0Ahttps://www.hhs.gov/hipaa/for-professionals/index.html%0Ainternal-pdf://903/index.html.
192. B. Ghiasi, G. Mehdipour, N. Safari, H. Behboudi, M. Hashemi, M. Omidi, Y. Sefidbakht, A. Yadegari and M. R. Hamblin, Theranostic applications of stimulus-responsive systems based on carbon dots, Int. J. Polym. Mater. Polym. Biomater., 2021, 17, 117–130,  DOI:10.1080/00914037.2019.1695207.
193. H. F. Etefa and F. B. Dejene, Applications of Green Carbon Dots in Personalized Diagnostics for Precision Medicine, Int. J. Mol. Sci., 2025, 26, 2846,  DOI:10.3390/ijms26072846.
194. V. Mohan, Recent Advances of Carbon dots for Treatment of Alzheimer's and Parkinson's Diseases, Int. J. Adv. Nano Comput. Anal., 2023, 2, 240,  DOI:10.61797/ijanca.v2i1.240.
195. H. Ding, T. Xiao, F. Ren, Y. Qiu, Z. Shen, X. Chen, E. Mijowska and H. Chen, Carbon-based nanodots for biomedical applications and clinical transformation prospects, BMEMat, 2024, 1–19,  DOI:10.1002/bmm2.12085.
196. W. Chou and A. Canchola, Machine Learning and Artificial Intelligence in Nanomedicine, Wiley Interdiscip. Rev.:Nanomed. Nanobiotechnol., 2025, 1–17,  DOI:10.1002/wnan.70027.
197. L. Liu, M. Bi, Y. Wang, J. Liu, X. Jiang, Z. Xu and X. Zhang, Artificial intelligence-powered microfluidics for nanomedicine and materials synthesis, Nanoscale, 2021, 19352–19366,  10.1039/d1nr06195j.
198. C. Han, X. Dong, W. Zhang, X. Huang and L. Gong, Intelligent Systems for Inorganic Nanomaterial Synthesis, Nanomaterials, 2025, 1–29.
199. A. S. Jalilov, Mater. Adv., 2024, 7097–7112,  10.1039/d4ma00505h.
200. S. Dighe, S. Jog, M. Momin, S. Sawarkar and A. Omri, Intranasal Drug Delivery by Nanotechnology: Advances in and Challenges for Alzheimer's Disease Management, Pharmaceutics, 2024, 16, 58,  DOI:10.3390/pharmaceutics16010058.

---