A one health nanotechnology approach to address antimicrobial resistance: state-of-the-art and strategic outlook

Abstract

Antimicrobial resistance (AMR) has emerged as a critical global health threat, driven by the rapid evolution and dissemination of resistance mechanisms among pathogens, and exacerbated by the interconnectedness of human, animal, and environmental health sectors. This review provides a comprehensive synthesis of the mechanisms underlying AMR including membrane permeability modification, efflux pumps, enzymatic inactivation, and target site modification while framing the crisis within the One Health perspective that emphasizes cross-sectoral collaboration and holistic strategies. The article systematically evaluates current approaches to combating AMR, such as novel drug discovery, combination therapies, bacteriophage-based interventions, antimicrobial adjuvants, and antimicrobial peptides, highlighting their respective strengths and limitations. The core of the review focuses on the advances in nanotechnology-based strategies, detailing the antimicrobial potential of diverse nanomaterials including chitosan, poly(lactic-co-glycolic acid) (PLGA) nanoparticles, liposomes, solid lipid nanoparticles, metal and metal ion nanoparticles (e.g., zinc oxide, silver, copper, gold, titanium, magnetic, cobalt), carbon dots, dendrimers, and hydrogels. Special attention is given to their mechanisms of action, efficacy against multidrug-resistant organisms, and applicability across human, veterinary, and environmental contexts. Moreover, the review addresses the limitations of nanotechnology-based approaches, such as nanoparticle cytotoxicity, the potential for nanoparticle-induced resistance, and the toxicological and ecological risks posed to One Health ecosystems. By critically appraising these challenges, the review identifies key research gaps and regulatory hurdles that must be overcome to enable the safe and effective clinical translation of nano-antimicrobials. The article concludes by outlining future prospects for the field, advocating for interdisciplinary research, responsible stewardship, and innovative policy frameworks to sustain the fight against AMR and protect global health.

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Ansh Desai

Ansh Desai is an undergraduate student pursuing a Bachelor of Technology in Biotechnology at the Department of Biotechnology, NIT Warangal. He worked on this review as part of the Student Research Internship Program at the IIT Gandhinagar. His academic interests include molecular biology, genetics, and bioinformatics.

Subhojit Ghosh

Subhojit Ghosh obtained his bachelor's degree in Molecular Biology and Biotechnology from the University of Kalyani, West Bengal, India. He obtained his master's degree in Agricultural Biotechnology from Ramakrishna Mission Vivekananda Educational and Research Institute, India, in 2021. Following this, he worked as a Junior Research fellow at ICAR-Central Research Institute for Jute and Allied Fibres, India. He joined the Indian Institute of Technology as a PhD research scholar in 2022.

Subramanian Sankaranarayanan

Dr. Subramanian Sankaranarayanan did his bachelor's degree in Agriculture and got a Master in Biotechnology from Tamil Nadu Agriculture University, India, in 2009. He obtained his PhD in plant developmental biology from the University of Calgary in Canada in the year 2015. Following this, he worked as a post-doctoral scientist in several leading institutes like ITbM, Nagoya University, Cold Spring Harbor Laboratory and Purdue University for over six years. He took up a position as a faculty at the Indian Institute of Technology Gandhinagar in 2022. He has published more than 30 research papers in reputed international journals.

Dhiraj Bhatia

Dr. Dhiraj Bhatia obtained his PhD from NCBS-TIFR, Bangalore, India, in DNA nanotechnology. Post-PhD, he went to Curie Institute in Paris to join the team of Ludger Johannes initially as a Curie fellow and later as an HFSP long-term fellow where he learnt the cellular and biological applications of DNA nanodevices. In 2018, he moved to India to start his own laboratory at the Indian Institute of Technology Gandhinagar where he is an Associate Professor and was a Ramanujan fellow till 2023. His lab focuses on translational aspects of DNA nanotechnology to develop tools to program biological systems for biomedical applications.

Amit K. Yadav

Amit K. Yadav is currently working as an Early Career Fellow at the Department of Biological Sciences and Engineering, Indian Institute of Technology Gandhinagar (IITGN), Gujarat, India. He obtained his PhD degree in Science from Jawaharlal Nehru University, New Delhi, India, in 2024. He is the recipient of the prestigious Prime Minister Research Fellowship Award from the Ministry of Education, Government of India. He also received the Outstanding PhD Thesis Award 2024 for his PhD work. His research focuses on the design and application of cutting-edge nanotechnology and nanoscience-based electrochemical biosensors, with a particular interest in diagnostics. He focuses on “Point-of-Care” diagnostic devices, aiming to tackle public health challenges by providing rapid and cost-effective medical care solutions.

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1. Introduction

Antimicrobials encompass a broad category of compounds that either inhibit or kill pathogenic microorganisms such as bacteria, fungi, protozoa, and viruses. These compounds include both organic and synthetic varieties. Antibiotics were first studied in the early 20th century, with notable discoveries like Salvarsan and penicillin,¹ and their use was popularised during the following decades. The introduction of antimicrobials into medical practices has reduced the mortality rate of multiple potentially lethal conditions, such as pneumonia² and sepsis.^3,4 They are also utilised for complex treatments, including organ transplants and surgeries.⁵ Based on their mechanisms of action, antibiotic agents are classified into two categories: bactericidal agents, which kill bacterial cells, and bacteriostatic agents, which inhibit bacterial growth without directly causing cell death.⁶ However, over time, new strains of bacteria have emerged that maintain their viability even when exposed to high antibiotic concentrations. Similar patterns have been observed in non-bacterial pathogens like Plasmodium falciparum, the causative pathogen of malaria.⁷ This capability of a microorganism to resist the activity of antimicrobial agents at concentrations that would typically be inhibitory is termed antimicrobial resistance (AMR).⁸ AMR has been associated with the overprescription and improper usage of antibiotics, as prolonged exposure to antimicrobials stimulates the development of resistance against them.⁹ However, research suggests that AMR is not just a modern phenomenon, with resistance genes found in permafrost samples ranging from 3000 to 3 000 000 years old.^10,11 This suggests that resistance arises through intrinsic evolutionary processes in the bacteria. In 2017, the World Health Organization (WHO) classified numerous antibiotic-resistant bacteria as “priority pathogens”, posing a severe risk to modern healthcare.¹² Developing new treatments for these infections has become a primary concern, as conventional methods are unable to combat them effectively.¹³ Nanomaterials are emerging as a potential solution due to their ability to overcome resistance mechanisms.

As stated, a significant factor contributing to the development of AMR is the inappropriate utilisation of antibiotics during medical treatment. During the administration of antibiotic drugs, it is necessary to ensure that appropriate dosage concentrations are used. However, studies have shown that less than 50% of patients receive adequate or appropriate dosages of antibiotics during treatment.^14,15 Furthermore, it has been found that antibiotics are sometimes prescribed for non-bacterial infections as well. For instance, a meta-analysis of COVID-19 infections found that despite a low apparent rate of bacterial co-infection (6.9%), antibiotics had been prescribed for 71% of infections.¹⁶ In many developing countries, antibiotics do not require prescriptions and are often readily available over the counter.¹⁷ Such incidences create conditions in which bacteria exist in antibiotic concentrations well below the minimum inhibitory concentration (MIC). Even at non-inhibitory concentrations, antibiotics still exert external stress on bacteria, prompting adaptation processes. This stress can lead to the development of antimicrobial-resistant genes through mutations. Bacteria possessing these genes may proliferate more rapidly than their non-resistant counterparts, gaining favour through natural selection. Moreover, these resistance genes can be transferred to other non-resistant bacteria via horizontal gene transfer (HGT), facilitating the spread of resistance to new species.¹⁸

The rise of AMR is not solely attributable to medical treatments. Many farmers routinely administer antimicrobials to livestock in pursuit of better health and increased yields. This practice remains widespread in numerous low- and middle-income nations with minimal regulatory oversight.¹⁹ However, due to varying antibiotic dosages in livestock, environments with low antibiotic concentrations are frequently created, providing ample opportunities for resistance to develop. Several studies have identified the existence of antimicrobial-resistant bacteria among farmers and those in close proximity, suggesting transmission from livestock.²⁰ Other studies show that over 90% of antimicrobials administered to livestock are excreted into the environmental microbiome, where resistance can again develop.²¹ Collectively, these factors significantly contribute to the global escalation of AMR. In 2014, the WHO released a report describing AMR as “a problem so serious that it threatens the achievements of modern medicine”.²² Antibiotics form a substantial part of healthcare, but the rise in resistance has contributed to a spike in severe infections globally. According to the US Centers for Disease Control, approximately 2.8 million infections involving antibiotic-resistant pathogens occurred in 2019, resulting in 35 000 deaths.²³ Another study indicated that globally, around 4.95 million deaths may be linked to antimicrobial-resistant infections.²⁴ This issue also poses substantial economic risks. Prolonged hospital stays, ineffective treatments, and the escalating costs of less commonly used antibiotics are driving up treatment expenses rapidly. A 2023 report by the Organization for Economic Co-operation and Development (OECD) estimated that AMR costs its member nations $28.9 billion.²⁵ In the absence of effective, permanent measures to combat this issue, it is feared that such costs will continue to increase drastically.

In this review, we explore the ongoing fight against AMR, an escalating global threat. While traditional methods are becoming less effective, a new weapon is emerging on the horizon: nanotechnology. Furthermore, this review will explore the emerging role of nanoparticles (NPs) as a promising strategy to combat AMR pathogens, highlighting their various types, formulations, and proposed mechanisms of antimicrobial action. We will also elaborate on the synergistic effects observed when NPs are combined with conventional antibiotics, emphasising how such combinations enhance targeted delivery and promote effective bacterial cell disruption. This field holds immense potential to combat AMR through various strategies, offering hope for the future of medicine. Moreover, this review highlights recent advances in the design and application of NPs and nanocomposites (NCs) aimed at tackling antibiotic-resistant and biofilm-producing bacteria. As a rapidly evolving interdisciplinary field, it merges insights from materials science, microbiology, nanotechnology, and AMR, with a particular focus on microbial biofilm dynamics. We also discuss cutting-edge nano formulation strategies for conventional antimicrobial agents that enhance their therapeutic performance. This comprehensive overview is intended to support a broad audience of researchers working in biomaterials, biomedical nanotechnology, infection control, and the development of improved therapies for managing persistent and chronic wound infections. Prior literature has largely concentrated on a limited range of nanoparticle materials. This work provides a comprehensive analysis of developments in nanoparticle technologies encompassing a wider array of materials and offers a comparative perspective with conventional methodologies, an approach not addressed in earlier work. Moreover, this review uniquely adopts a one health framework, emphasizing the interconnectedness of human, animal, and environmental health in the context of AMR. This multidisciplinary perspective is often lacking in existing reviews, which tend to focus on either clinical or material science aspects in isolation. By bridging the gaps between public health, microbiology, and nanoscience, we aim to provide a holistic understanding of how nanotechnologies can be strategically leveraged across sectors to combat AMR.

1.1 Development of AMR

Some bacteria inherently possess resistance to antibiotics²⁶ due to altered membrane structure without any mutation. These modifications prevent antibiotics from interacting with or penetrating the membrane, rendering them ineffective. Gram-negative bacteria, in particular, exhibit higher resistance compared to Gram-positive bacteria due to their outer membrane^27,28 which restricts the penetration of large antibiotics through its small pores. Another form of intrinsic resistance arises when bacteria lack specific membrane ligands, preventing antibiotics from attaching to and deactivating the bacteria.²⁹ However, bacteria can also acquire resistant traits through two other mechanisms: chromosomal mutations or gene transfer. Chromosomal mutation involves irreversible changes in the bacterial genome. When exposed to antibiotics, bacteria undergo evolutionary adaptation due to environmental pressures. Mutations that confer resistance traits are positively selected within bacterial populations and passed vertically to subsequent generations.³⁰ Over time, these mutations accumulate, providing robust resistance or even immunity against antibiotics. Certain species may develop resistance more rapidly based on their genomic mutation rates.³¹ Moreover, if two antibiotics share similar structures or mechanisms of action, a mutation conferring resistance to one antibiotic can confer resistance to the other as well¹³ leading to the simultaneous development of multiple antibiotic resistances.

AMR can also spread through HGT. When two different strains of bacteria coexist in the same microenvironment, genetic elements from one strain can be passed to the other independent of reproduction.¹⁸ Transferable genetic elements include plasmids, phages and transposons.³² Research has found that, unlike vertical inheritance, HGT does not require positively selecting environments and can occur in the absence of antibiotics.³³ HGT occurs through three pathways: transformation, transduction and conjugation. In 1928, it was demonstrated that certain bacteria possess the ability to uptake and express extracellular fragments of DNA.³⁴ This process, called transformation, allows the indirect exchange of genes between bacteria. The fragments involved are chromosomal and are not part of any transferable genetic elements. This ability has been observed in approximately 1% of bacterial species.³⁵ On the other hand, transduction and conjugation occur exclusively through transferable genetic elements.¹³ Transduction occurs when an infecting bacteriophage accidentally uptakes bacterial plasmid or chromosomal DNA alongside the phage DNA. Upon infecting a new cell, the bacteriophage transfers the bacterial genes it has picked up to the host.³⁶ Several studies have shown that genes conferring resistance against antibiotics can be spread through transduction.^37,38

Conjugation facilitates the transfer of genes between bacteria through direct cell-to-cell contact via surface pili. Genes are transferred in the form of plasmids, which are collections of functional genes capable of self-replication organized into stable structures. Conjugative plasmids contain a distinct DNA segment known as the origin of transfer (oriT), which allows for the transfer of plasmids.³⁹ Once inside the recipient bacterium, these plasmids are expressed, allowing new traits to be inherited. Many genes responsible for antibiotic resistance have been identified on plasmids, facilitating their spread through conjugation.⁴⁰

1.2 Mechanism of AMR

1.2.1 Modification of membrane permeability. Antibiotics like β-lactams exert their effects by penetrating bacterial cells through the outer membrane. A common resistance mechanism involves reducing the permeability of this outer membrane. Antibiotics typically enter by utilising the porin family of proteins, which are embedded in the outer membrane. Numerous studies have shown that these proteins are often downregulated or modified with increased selectivity in resistant bacteria.^41,42 In contrast, bacteria like Pseudomonas aeruginosa form aggregates within self-produced matrices called biofilms. These biofilms consist of lipids, polysaccharides, and proteins, providing robust resistance against multiple antimicrobial agents.⁴³

1.2.2 Efflux pumps. Efflux pumps are naturally occurring structures in bacteria that are responsible for the excretion of toxic compounds from within the cells. Through mutations, these pumps can adapt to specifically target antimicrobial molecules, enabling the rapid removal of these substances and thwarting their effects effectively.⁴⁴ Efflux pumps can target numerous antimicrobial agents, and mutated efflux pump genes can spread to other bacterial species via gene transfer mechanisms.

1.2.3 Enzymatic inactivation. In addition to preventing antibiotic molecules from entering the cell, bacteria can develop resistance by directly modifying the antibiotics themselves, a process known as enzymatic inactivation. Several enzymes, including carbapenemases, β-lactamases and others, can hydrolyse various classes of antibiotic molecules, rendering them inactive.²⁶ A more common form of modification is the addition of functional groups to the antibiotics, which inhibit binding via steric hindrance. These enzymes, such as acyltransferases and phosphotransferases, form the largest family of resistance enzymes, collectively called group transferases.⁴⁵

1.2.4 Target site modification. Antibiotics exhibit high specificity for their target sites, and any changes to these targets can hinder effective binding (Fig. 1). Such modifications can take place in a multitude of ways. For example, rifampin is an antibiotic that binds to the β subunit of RNA polymerase enzymes. A single point mutation in the rpoB gene, which encodes RNA polymerase β, can alter the amino acid sequence, preventing rifampin from binding effectively and thus blocking its action.⁴⁶ Alterations can also occur through post-transcriptional modification of target proteins. Erythromycin ribosome methylase (erm) genes encode a family of enzymes that methylate a single nucleotide of the 23S rRNA in the 50S subunit of bacterial ribosomes. This modification confers resistance to macrolide and lincosamide antibiotics, which bind to the 23S rRNA.⁴⁷

Fig. 1 Schematic representation of common antibiotic targets and the corresponding bacterial resistance mechanisms. The left panel illustrates key cellular targets of antibiotics within bacterial cells, including the cell wall (targeted by β-lactams and vancomycin), cell membrane (targeted by daptomycin), DNA gyrase (inhibited by aminocoumarins and fluoroquinolones), RNA polymerase (targeted by rifamycin and ansamycin), folate synthesis pathway (inhibited by sulfonamides), and protein synthesis machinery (targeted by agents like streptomycin and tetracycline). The right panel depicts major resistance strategies employed by bacteria to evade antibiotic effects, such as enzymatic inactivation of drugs, enhanced efflux pump expression to expel antibiotics, target site modification, reduced membrane permeability preventing drug entry, and accumulation of targeted genetic mutations. Together, these elements highlight the interplay between therapeutic intervention and microbial adaptation, underscoring the challenges in combating AMR.

2. AMR from a one health perspective

AMR represents one of the most pressing challenges in global health, and it is a prime example of why a one health approach is urgently needed.⁴⁸ The one health concept is a multidisciplinary and collaborative framework that recognizes the intricate link between human health, animal health, and the environment, aiming to develop integrated strategies to address complex health threats. The rise and spread of AMR are deeply rooted in interconnected sectors ranging from human healthcare and veterinary medicine to agriculture and environmental contamination.^49,50 Inappropriate and excessive use of antibiotics across these domains such as prophylactic use in livestock, overprescription in human medicine, and antibiotic pollution in soil and water systems has collectively accelerated the development of resistant microbial strains.⁵¹

Historically, the roots of the one health approach can be traced back to the 19th century, when Rudolf Virchow introduced the term zoonosis, highlighting the relationship between animal and human diseases. This foundation was later strengthened by Calvin Schwabe's concept of “one medicine”, emphasizing the integration of veterinary and human health disciplines. The modern one health agenda gained momentum following the 2004 Wildlife Conservation Society's Manhattan Principles, which called for cross-sectoral efforts to address emerging infectious diseases and ecosystem health.⁵²

In the context of AMR, the one health approach brings much-needed clarity to how resistance genes and resistant organisms circulate among humans, animals, and the environment. For instance, antibiotic use in livestock for growth enhancement and disease control can lead to the emergence of resistant bacteria in animals, which may then be transferred to humans through direct contact or the food chain. Likewise, misuse in clinical settings such as incorrect prescriptions, incomplete treatment courses, and patient non-compliance can promote the survival and spread of resistant strains.⁵³ Moreover, environmental reservoirs, particularly water bodies contaminated by pharmaceutical effluents, agricultural runoffs, and untreated sewage, serve as breeding grounds for resistance genes. These genes can be horizontally transferred among bacteria via mobile genetic elements, increasing the pool of resistant organisms across ecosystems. This microbial gene exchange can occur across species and habitats, creating a global AMR network that transcends geographical and biological boundaries.

The cumulative effect of these interactions has made the prevention and treatment of bacterial infections increasingly difficult. Addressing this multifaceted threat requires coordinated action involving healthcare providers, veterinarians, environmental scientists, researchers, policymakers, and public health authorities. This review emphasizes that AMR cannot be tackled in isolation within any single sector. Instead, it must be approached through integrated, cross-disciplinary efforts that reflect the one health ethos where collaboration between human, animal, and environmental health sectors becomes the foundation for sustainable and effective AMR mitigation strategies. Fig. 2 highlights the complex exchange of resistant pathogens and resistance genes among humans, animals, farming systems, water sources, environmental reservoirs, and vectors. Key routes include hospital and community waste contributing to environmental contamination, sewage affecting water supplies, and the potential for transmission through food consumption, animal waste, irrigation, and direct contact with contaminated vectors. This multi-directional flow emphasizes the necessity for integrated surveillance and cross-sectoral collaboration to mitigate AMR emergence and spread.⁵⁴

Fig. 2 Schematic illustration of the interconnected transmission pathways of AMR within the one health framework (reproduced with permission from ref. 54, @ 2018, Springer Nature).

3. Current approaches to combating AMR

The increasing prevalence of AMR is a pressing concern for governmental and international bodies. Heightened awareness of this issue has spurred significant efforts to develop methods aimed at preserving the effectiveness of antimicrobials. This section will explore several conventional approaches currently under study as potential solutions, discussing their advantages and limitations.

3.1 Novel drug discovery

Following the discovery of penicillin, a wide array of antimicrobial agents were swiftly developed and integrated into medical practice, marking the ‘golden age of antibiotics’ that persisted until the 1960s. Progress slowed considerably thereafter, with few new antibiotic classes identified until the introduction of oxazolidinones and lipopeptides in the early 2000.⁵⁵ Presently, most newly developed antibiotics either belong to existing classes (e.g., dalbavancin, ceftaroline) or are combinations of established molecules.⁵⁶

Identifying novel antibiotic classes has become increasingly challenging, and the creation of entirely new antibiotic molecules has markedly declined. A report by the Infectious Diseases Society of America noted a 75% reduction in antibiotic approvals by the US Food and Drug Administration from 1983 to 2007.⁵⁷ This has been linked to several reasons, of which economic cost is a primary concern. The cost for research on new antibiotic classes is significant and has the potential for failure, due to which investing in such research carries a high risk for pharmaceutical industries. Consequently, many are focusing instead on strategies to enhance the efficacy of existing antibiotics, and some of these approaches show promising results.

3.2 Combination drug therapy

Combination drug therapy (CDT) involves simultaneously using multiple distinct antimicrobial drugs to treat a single infection. Research indicates that using antibiotic agents in combination enhances efficiency, reducing the likelihood of bacteria developing resistance mechanisms.^58,59 CDT has several other advantages over traditional single-antibiotic monotherapy. By combining drugs, a broader spectrum of species can be targeted, which is advantageous when the infectious agent is unidentified. Moreover, lower concentrations of each drug are needed, decreasing the risk of side effects and toxicity.⁶⁰ The selection of drugs plays a critical role in the effectiveness of CDT. If the antibiotics employed share identical or similar mechanisms, resistance developed against one could confer resistance to others. Hence, the antibiotics used in CDT must target distinct targets across different pathways, different aspects within a single pathway, or unique facets of a common target molecule.^42,61 However, this technique comes with a few drawbacks. Antibiotic molecules can interact unpredictably, causing unforeseen side effects and complications during treatment. Moreover, a meta-analysis of randomized controlled trials comparing β-lactam monotherapy and combination therapy found that while combination therapy had a lower treatment failure rate, it was also associated with higher mortality and fungal superinfection rates.⁶²

3.3 Bacteriophage-based therapy

Bacteriophages are viruses that specifically infect bacteria and are bactericidal in nature. These phages inject their genetic material into the host bacterium, where it replicates to form new phages. Upon maturation, these phages release lytic proteins that rupture the bacterial cell. Bacteriophages were first discovered in 1917⁶³ and were quickly recognized as potential therapeutic agents. Subsequent trials began to assess the feasibility of using phages in clinical settings. Unlike traditional antibiotics, which have a broad spectrum of activity, bacteriophages bind exclusively to specific receptors on bacterial cells, unique to each bacterial species. This highly host-specific action preserves beneficial bacteria in the gut and other microbiomes, which are often disrupted by antibiotic treatments.⁶⁴ Due to their self-replicating nature, even lower concentrations of phages are sufficient for the treatment. This allows the usage of smaller dosages, which reduces the risk of immunogenic responses.⁶¹ Furthermore, since a single bacteriophage can lyse a single bacterial cell, there is no MIC for the treatment to be effective. Nevertheless, bacteria can still evolve resistance to bacteriophages, similar to antibiotics, by inhibiting different life stages of the virus.⁶⁵

The incorporation of bacteriophages into clinical treatment is hindered by their narrow host range. Identification of the infecting bacterial strain is necessary before phage therapy can be administered, unlike traditional antimicrobial agents that can be applied more broadly. Moreover, bacteriophages are specific to individual bacterial species, necessitating a mixture of phage species for the treatment of multiple bacterial infections. Currently, the use of bacteriophages in clinical settings is subject to numerous government regulations, due to which the scope for research on phage therapy is limited.⁶⁶

3.4 Antimicrobial adjuvants

Adjuvants are compounds that enhance the efficiency of antibiotics by increasing the susceptibility of target cells. Typically, adjuvants are devoid of antimicrobial activity themselves; instead they suppress bacterial resistance mechanisms.⁶⁷ Given the declining rate of new antimicrobial drug discoveries, there is growing interest in exploring adjuvants to augment the effectiveness of existing antibiotics. Adjuvants function by reversing or neutralizing the effects of resistance genes, thereby allowing antibiotics to act unhindered. Compounds like clavulanic acid and quercetin inhibit resistance enzymes such as β-lactamases and aminoglycoside phosphotransferases.^68,69 Certain D-amino acids can disrupt biofilm formation and dismantle existing biofilms.⁷⁰ Other observed methods of action include enhancing cellular uptake of antibiotics, inhibiting efflux pumps, and inducing oxidative stress in bacteria.⁶¹

Despite promising outcomes, discovering new adjuvant molecules remains challenging. Identifying compounds that effectively target specific resistance mechanisms is both time-consuming and costly. Moreover, like combination drug therapy, interactions between adjuvants and antibiotics can lead to adverse side effects.⁷¹ Therefore, intermolecular interactions must be thoroughly studied prior to clinical application. These challenges currently limit the widespread use of antimicrobial adjuvants.

3.5 Antimicrobial peptides

Antimicrobial peptides (AMPs) encompass a diverse group of natural peptide chains and proteins that exhibit antimicrobial properties. AMPs are found in virtually all organisms, and are integral components of the innate immune system, with bactericidal action against foreign pathogens. In addition to their antimicrobial capabilities, these proteins can bolster host immune responses against infections.⁷² The discovery of AMPs dates back to 1939 with the isolation of gramicidin from Bacillus bacteria, which was shown to effectively prevent pneumococcal infections in mice.⁷³ AMPs are typically short (<50 amino acids), highly hydrophobic, and carry net positive charges; hence, they are also referred to as cationic host defense peptides (CHDP).⁷⁴ Most AMPs have a broad range of action, targeting most microorganisms, including bacteria, viruses and fungi.

Bacterial cell membranes, characterized by a negative charge from lipopolysaccharides and lipoteichoic acids, attract cationic antimicrobial peptides through electrostatic interactions. Once attached, the peptides penetrate the membrane due to their hydrophobic nature, increasing membrane permeability and leading to cell lysis.⁷⁵ AMPs may also disrupt the cytoplasmic membrane using similar mechanisms. Studies indicate that certain AMPs interfere with internal bacterial processes such as cell wall synthesis.⁷⁶ AMPs have also been shown to have antiviral properties, by inhibiting viral entry to cells or disruption of viral envelope and membranes.⁷⁵ Furthermore, AMPs can stimulate the host immune system through various mechanisms. For instance, AMPs like cathelicidin act as a chemoattractant, recruiting immune cells such as leukocytes and neutrophils.⁷⁷ Cathelicidin and hepcidin also promote the production of chemokines, which enhance the neutrophil response.^78,79 Wuerth et al. reported the ability of the peptide IDR-1002 to regulate P. aeruginosa lung infections and related inflammations.⁸⁰ Other AMPs have been found to influence cytokine-mediated pathways through inhibition of pro-inflammatory cytokines, enhance phagocytosis activity in macrophages, and indirectly facilitate recruitment of leukocytes.⁷⁴

Research indicates that the development of AMP resistance mechanisms is rare, as they act on multiple targets fundamental to the cell structure.⁷⁵ Experiments performed on multidrug-resistant bacteria by Veldhuizen et al. found that when AMP resistance does develop, it is temporary and not retained by subsequent generations in the absence of AMPs, suggesting that the development of major resistance is improbable.⁸¹ Furthermore, while resistance between different AMPs has been reported, studies indicate that the emergence of cross-resistance between antibiotics and AMPs is unlikely to occur.⁸² Despite these advantages observed in vitro, only a few antimicrobial peptides have gained clinical approval from the US Food and Drug Administration (FDA).⁸³ This is mainly due to the proteins' low stability and their limited tolerance for salts and other human physiological compounds, which inhibit their efficacy in vivo.⁸⁴ Consequently, there is considerable interest in developing synthetic AMPs with enhanced stability. Studies have also highlighted the potential of AMPs to act as adjuvants alongside antibiotics.⁸⁵ Fig. 3 provides a comprehensive chronological overview of the development of antibiotics, emergence of resistance, and the introduction of alternative therapies. The timeline begins with the early discovery of penicillin in 1928 and tracks the “golden age of antibiotics” between the 1940s and 1960s, characterized by the introduction of broad-spectrum antibiotics such as streptomycin, tetracycline, and vancomycin. However, following this prolific period, there was a notable decline in the discovery of new antibiotic classes, coinciding with the increasing emergence of resistant bacterial strains such as methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE). Fig. 3 also highlights the parallel evolution of alternative therapeutic strategies, including phage therapy, antimicrobial peptides, NPs, and monoclonal antibodies, which align with the growing urgency to combat AMR. The rise of extensively drug-resistant pathogens in the early 2000s further reinforces the pressing need for novel interventions. Recent advances, such as the development of NPs for antimicrobial drug delivery and successful personalized phage therapies, exemplify the integration of nanotechnology into the broader one health strategy against AMR.

Fig. 3 Timeline illustrating the evolution of antibiotic discovery, emergence of AMR, and the development of alternative therapeutic strategies. The upper panel highlights four distinct phases in antibiotic development: (i) early discoveries including the use of mold for wound healing and the discovery of penicillin in 1928, (ii) the “golden age of antibiotics” (1935–1960) characterized by the introduction of multiple broad-spectrum antibiotics such as sulfonamides, tetracyclines, and rifampicin, (iii) a decline in new antibiotic development from the 1970s to the 1990s despite the emergence of drugs like gentamycin and ciprofloxacin, and (iv) a modern phase (2000 onward) marked by the rise of AMR and the approval of last-resort or combination antibiotics like linezolid, tigecycline, and ceftazidime/avibactam. The lower panel tracks the parallel rise of resistance, such as penicillin-resistant Staphylococcus in 1940, methicillin-resistant strains in the 1960s, and vancomycin-resistant Enterococcus by 1988. It also presents alternative AMR combating strategies, including the advent of phage therapy (1921), antimicrobial peptides (1939), NPs (1985), monoclonal antibodies (1998), and antibiotic–antibody conjugates (1994). Recent advancements include successful personalized phage therapy (2017) and nanoparticle-based drug delivery systems (2015), underlining innovative responses to the escalating AMR crisis. This figure underscores the urgent need for integrated strategies in the face of stagnating antibiotic discovery and growing resistance. Referenced from.^73,86–92

4. Nanotechnology-based approaches to AMR

Nanotechnology involves the study and synthesis of materials whose dimensions range between 1 nm and 100 nm, known as NPs. Within this size range, materials exhibit unique biological and chemical properties that can be harnessed for various applications.⁹³ NPs offer several advantageous properties that position them as promising alternatives to conventional antibiotics. Their physicochemical characteristics, such as size, shape, surface charge, and composition, significantly influence their interactions with both microbial pathogens and host tissues.^94–96 Notably, NPs with smaller dimensions exhibit a higher surface area-to-volume ratio, enhancing their ability to interact with bacterial membranes and penetrate host tissues, thereby improving antimicrobial efficacy and targeted delivery. The shape of NPs also plays a critical role; for instance, rod-shaped particles often demonstrate superior cellular penetration compared to spherical ones. Surface charge further dictates biological interactions – positively charged NPs are more likely to bind to negatively charged bacterial membranes, leading to membrane disruption and cell death. Additionally, surface charge can affect cellular uptake by host cells. The material composition of NPs, whether metallic or organic, along with surface modifications such as conjugation with antibodies, peptides, or other functional groups, can modulate their antimicrobial performance, enhance biocompatibility, and reduce cytotoxicity. Nanotechnology is increasingly being applied in medicine to address the growing challenge of drug resistance, particularly through the targeted delivery of therapeutic agents. Notably, NPs composed of metals such as gold, silver, and zinc oxide (ZnO) have demonstrated significant efficacy against antibiotic-resistant bacteria, including strains like MRSA, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Escherichia coli. The use of NPs for antimicrobial delivery offers several key benefits: enhanced bioavailability at the site of infection, reduced systemic toxicity, and the ability to maintain therapeutic concentrations even at lower doses, thereby minimizing side effects and slowing resistance development. Certain NPs, such as silver, selenium, and engineered carbon dots, demonstrate antimicrobial properties.⁹⁷ This antimicrobial activity includes a wide range of targets, including inhibition of biofilm formation,⁹⁸ release of reactive oxygen species (ROS), inhibition of mRNA transcription and disruption of cell membranes (Fig. 4).⁹⁹ Moreover, NPs serve as effective carriers for antibiotics due to several advantageous characteristics. They are resistant to AMR mechanisms, thus shielding the drug from inhibitory processes. Their small size facilitates easy uptake by bacteria through phagocytosis, ensuring rapid action. Furthermore, targeting NPs to specific receptors allows for localized antibiotic delivery, minimizing potential side effects.¹⁰⁰ Studies have shown enhanced antibiotic efficacy when combined with various types of NPs.¹⁰¹ Ongoing research explores NPs as a promising strategy to combat AMR. This section will discuss notable types of NPs currently under investigation for this purpose. Table 1 contains detailed information about the antimicrobial activity of some well-known nanomaterials.

Fig. 4 Schematic representation highlighting the various types of nanomaterials and their antimicrobial modes of action against resistant pathogens. The upper semicircle illustrates diverse nanomaterial platforms including metallic NPs, liposomes, quantum dots, hydrogels, dendrimers, mesoporous silica NPs, polymeric NPs, and others, each possessing unique physicochemical properties that contribute to antimicrobial activity. The lower semicircle summarizes the primary mechanisms by which these nanomaterials exert antimicrobial effects. These include (i) destabilization of microbial membranes, (ii) inhibition of essential enzymes, (iii) interaction with and binding to cellular components, (iv) interference with bacterial efflux pump systems, (v) disruption of the electron transport chain (ETC), and (vi) generation of ROS, leading to oxidative stress and DNA damage. Collectively, these multifaceted mechanisms enable nanomaterials to combat drug-resistant microorganisms effectively, offering promising alternatives to conventional antibiotics in the fight against AMR.

Table 1 Summary of antimicrobial activity mechanisms of various nanoparticle materials against target pathogens

Nanomaterial category	Nanomaterial	Target pathogen	Mechanism of action	Ref.
Polymeric NPs	CS	Propionibacterium acnes	Inhibition of cytokine IL-12p40 in human monocytes and IL-6 in keratinocytes	102
		Gram-negative bacteria	Disruption of the integrity of the outer membrane under acidic conditions	103
		Aspergillus flavus and A. parasiticus	Suppression of aflatoxin production	263
		Bacteriophages	Inactivation of mature phage particles and inhibition of phage reproduction	264
Metal ion NPs	ZnO	S. aureus	Production of reactive oxygen species and disruption of cellular membranes	265
		Klebsiella pneumoniae	Rupturing of the cell membrane and suppression of metabolic activity by binding to intracellular material	266
		E. coli	Damage to the membrane wall	267
		Salmonella typhimurium	Lysis of the cell membrane	160
		A. pleuropneumonia, Salmonella typhimurium and Haemophilus parasuis	Weak inhibition of bacterial growth and prevention of biofilm formation	268
	Ag	E. coli	Formation of pits in the membrane, inhibition of DNA replication, and denaturation of proteins	171
		E. coli and S. aureus	Generation of free radical species	97
		Pseudomonas aeruginosa	Disruption of biofilms and inhibition of biofilm formation	97
	Cu	Gram-negative bacteria	Formation of pits in the cellular wall, generation of reactive oxygen species, degradation of DNA, oxidation of metabolic proteins	184 and 269
		E. coli	Disruption of the cell wall, leading to degradation of the cytoplasm	183
	Au	S. aureus, K. pneumoniae, E. coli and B. subtilis	Inhibition of ATP synthetase, degradation of sulphur-containing proteins and blocking of tRNA binding sites	191 and 192
	Titanium	Gram-negative and Gram-positive bacteria	Increased permeability of the membrane, causing leakage of cellular components	200
		E. coli, P. aeruginosa, S. aureus, and M. luteus	Disruption of the cell membrane and plasmolysis	200
	Magnetic	S. aureus, A. viridians, and E. columbae	Inhibition of biofilm formation	270
		E. coli and S. aureus	Inhibition of protein synthesis and disruption of metabolic processes, including respiration	205 and 206
	Cobalt	S. aureus	Disruption of the cell membrane, interruption of DNA replication, and inhibition of proteins	214 and 271
		E. coli	Generation of reactive oxygen species	272
	Selenium	E. coli and S. aureus	Penetration of the outer membrane, modification of biosynthetic enzymes	218
		Candida albicans	Inhibition of preformed biofilms	219
	Cadmium oxide	S. aureus, K. pneumoniae, A. baumannii, E. coli, B. subtilis and P. aeruginosa	Increased permeability of the membrane, generation of reactive oxygen species, degradation of essential proteins and DNA	223 and 225
Other nanomaterials	Carbon dots	Gram-negative bacteria	Blocking the generation of pro-inflammatory cytokines	235
		E. coli and S. aureus	Increased permeability of the cell and decreased integrity of the plasma membrane	273
		S. aureus, Bacillus sp., and E. coli	Disruption of secondary structures of DNA and RNA	274
		Multi-drug-resistant Enterococcus faecium, E. faecalis, and S. aureus (MRSA)	Generation of reactive oxygen species and degradation of the bacterial cell wall	243 and 244
	Dendrimers	P. aeruginosa	Formation of holes in the lipid bilayer	249 and 250
		Multi-drug-resistant S. aureus, E. faecium and A. baumannii	Disruption of the cell membrane and leakage of cellular contents	250 and 251

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4.1 Chitosan

Chitosan (CS) is a natural biopolymer composed of a linear polysaccharide chain, which can disrupt bacterial cell membranes. It is obtained by the alkaline or enzymatic deacetylation of chitin, a biopolymer found in crustacean exoskeletons. The deacetylation process creates C₂ amino acids, which are positively charged under acidic conditions (below pH 6.5).¹⁰² These positively charged groups interact with the negatively charged lipopolysaccharides and lipoteichoic acids present in bacterial membranes, increasing their permeability and causing leakage of cellular contents.¹⁰³ The increased permeability allows CS to penetrate the cell membrane, where it binds to microbial DNA and inhibits protein synthesis by blocking mRNA transcription.¹⁰⁴ Experiments conducted by Y. Ma et al. suggest that CS also inhibits the action of metalloproteins by chelation of metal ion cofactors, which are necessary for microbial growth and proliferation.¹⁰⁵ At lower concentrations, CS demonstrates bacteriostatic activity rather than bactericidal effects. As the negative charge of the cell membrane is highly conserved in both Gram-positive and Gram-negative bacteria, the development of resistance against CS is considered improbable.⁹⁹ However, this antibiotic activity of CS is reliant on numerous factors, including solubility and pH, and is unreliable under variable conditions.¹⁰⁵

Numerous studies have demonstrated the antiviral and antifungal properties of CS as well.¹⁰² In the NP scale, CS has a high surface charge-to-volume ratio. This increases its affinity for bacterial membranes, resulting in higher penetration. Yadav et al. reported a sensitive, non-invasive, and label-free strategy for detecting trace amounts of norfloxacin (NF) in human urine using a nanocomposite composed of nanostructured yttrium oxide (nY₂O₃) and CS. The composite material was synthesized via a low-temperature, single-step hydrothermal method, offering a straightforward and cost-effective approach for fabricating the sensor platform.¹⁰⁶ CS NPs were shown to have more antimicrobial activity than normal CS and certain antibiotics, including doxycycline.¹⁰⁷ CS's polymeric nature allows it to be shaped into nanostructures as desired to improve the delivery mechanism. In addition, augmenting polymeric NPs with antibiotic molecules or other NPs allows them to be released in a controlled, targeted manner.¹⁰⁸ These composite structures also show a greater inhibitory effect on microbes than their components. Ibrahim et al. demonstrated that CS NPs loaded with gentamycin sulphate, ciprofloxacin HCl, and tetrachlorocycline increased the zone of inhibition of the antibiotics against E. coli and S. aureus by 16.5 mm, 15.5 mm and 7–10 mm, respectively.¹⁰⁹ In addition, Sobhani et al. found that ciprofloxacin-loaded NPs have a 50% lower MIC than regular ciprofloxacin (CPX)-HCl molecules.¹¹⁰ Another study showed that the addition of CS to silver molecules increased the diameter of the inhibition zone against bacteria by approximately 15 mm, saturating at 70% CS content.¹⁰⁵ Fayed et al. conducted an experiment demonstrating that amoxicillin, when encapsulated within CS NPs, exhibited a biphasic release profile, with approximately 33% of the drug released within the first 2 hours and an additional 33% released over the subsequent 70 hours¹¹¹ [Fig. 5(2)]. Recently, CS has also been reported to enhance the antimicrobial activity of cloxacillin,¹¹² dihydroartemisinin¹¹³ [Fig. 5(1)], and ampicillin¹¹⁴ against methicillin-resistant S. aureus strains. CS also acts as a carrier and stabilizer for copper-containing NPs and nitric oxide-releasing NPs.¹¹⁵ Among all polymeric NPs being studied, CS has demonstrated the greatest potential for use against AMR. CS NPs were found to increase the efficacy of β-lactam antibiotics and β-lactamase inhibitors against β-lactam resistant pathogens.¹¹⁶ Polymeric CS is already used in a variety of medical, agricultural and pharmaceutical fields; however, CS NPs are yet to be approved for clinical use.¹¹⁷

Fig. 5 (1) Schematic illustration of the synthesis and antibacterial mechanism of DHA-CS NPs against MRSA biofilms. (A) Dihydroartemisinin (DHA) and CS are combined using ionic-gelation methods to synthesize DHA-loaded CS NPs (DHA-CS NPs). (B) Biofilm formation stages of MRSA include motility, adhesion, microcolony formation, and maturation. DHA-CS NPs interact with MRSA, penetrating the cells and downregulating key biofilm-associated genes (icdA, agrA, cidA, sarA) (reproduced with permission from ref. 113, @ 2025, Elsevier]. (2) Flow cytometry analysis of time-dependent internalization of Cur-CS NPs by Helicobacter pylori. Representative flow cytometry plots illustrate the nanoparticle uptake by H. pylori after incubation for 4 hours (A), 8 hours (B), and 24 hours (C). Untreated H. pylori cells under identical conditions served as the negative control. Signal detection was performed using the FL2 channel (green fluorescence), with linear amplification (FL2-A) and doublet discrimination applied to ensure the analysis of single-cell events (reproduced with permission from ref. 111, @ 2023, Elsevier].

4.2 PLGA NPs

PLGA (poly[lactic-co-glycolic] acid) is a synthetic polymer frequently used for synthesizing NPs. When hydrolyzed, PLGA degrades into lactic acid and glycolic acid, which can be metabolized by human bodies. Hence, it is considered to be biodegradable and biocompatible as well.¹¹⁸ Studies have shown that PLGA NPs are not cytotoxic to macrophages and other immune cells^119,120 [Fig. 6(1)]. Due to these properties, PLGA is frequently used for drug delivery in clinical trials, particularly for targeting intracellular infections. Alsa’d et al. successfully utilized PLGA NPs to deliver ciprofloxacin and ceftazidime to macrophages infected with Staphylococcus aureus and Klebsiella pneumoniae.¹²¹ Sabaeifard et al. demonstrated that amikacin-loaded PLGA NPs provide sustained release for up to 9 hours after incubation in vitro, effectively delivering the drug in a controlled manner without a significant reduction in activity.¹¹⁹ PLGA NPs have also been successful in targeting and delivering gentamicin, which typically has poor cell penetration, to organs affected by brucellosis¹²² and in treating K. pneumoniae infections¹²³ [Fig. 6(2)]. Other antibiotics demonstrating enhanced antimicrobial activity when delivered using PLGA include CPX¹²⁴ [Fig. 7(1)], rifampicin¹²⁵ [Fig. 7(2)], azithromycin^126,127 [Fig. 6(4)], nafcillin and sparfloxacin.¹¹⁸ Furthermore, PLGA NPs can be functionalized to improve the specificity of delivery and disassemble biofilm obstructions. Baelo et al. showed that ciprofloxacin-loaded PLGA NPs functionalized with the enzyme DNase I were able to eradicate up to 95% of established P. aeruginosa biofilms, and repeated administration eradicated up to 98%¹²⁸ [Fig. 6(3)]. PLGA NPs have demonstrated stability under varying pH and temperature conditions; however, long-term stability studies are still ongoing.¹²⁹ Numerous studies have found that antibiotics delivered using PLGA NPs are protected from bacterial resistance mechanisms.^120,130,131 The US Food and Drug Administration and the European Medicine Agency have approved the use of PLGA NPs for parenteral administration of antibiotics.¹³⁰

Fig. 6 (1) Characterization and antibacterial efficacy of AZI-loaded PLGA NPs against resistant bacterial strains (reproduced with permission from ref. 120, @ 2022, MDPI). (2) Schematic representation of evaluation of gentamicin-loaded NPs for enhanced antibacterial efficacy against Klebsiella pneumoniae (reproduced with permission from ref. 123, @ 2018, Elsevier). (3) Physicochemical characterization and drug release profile of nanoparticle formulations. (A) SEM images depicting the surface morphology of different nanoparticle systems: PLGA–CPX, PLGA coated with polydopamine and loaded with ciprofloxacin (PLGA–PL–CPX), and PLGA–PL–CPX further functionalized with DNase I. (B) Comparative release profiles of CPX from the respective nanoparticle formulations, illustrating variations in drug release kinetics based on surface modification and enzyme conjugation (reproduced with permission from ref. 128, @ 2015, Elsevier). (4) Representative images demonstrating the selective localization of labeled NPs inside cellular inclusions associated with persistent infection, indicating effective cellular uptake and homing capability of the nanoparticle system toward infected compartments (reproduced with permission from ref. 126, @ 2011, Elsevier).

Fig. 7 (1) Schematic representation of the synthesis of ciprofloxacin-loaded PEG–PLGA NPs using the solid-in-oil-in-water (S/O/W) ion-pairing technique. (A) In the initial solid-in-oil (S/O) step, ciprofloxacin (CIP) is dispersed in a PEG–PLGA polymer solution prepared in acetone, followed by the addition of dextran sulfate to facilitate ion pairing. (B) The resulting mixture is then introduced into distilled water, leading to spontaneous nanoparticle formation through a self-assembly process (reproduced with permission from ref. 124, @ 2023, Springer Nature). (2) Schematic of rifampicin-loaded polymeric NPs for targeted delivery to mycobacteria-infected macrophages (reproduced with permission from ref. 125, @ 2017, Elsevier).

4.3 Liposomes

Liposomes are vesicles consisting of one or more types of lipid bilayers enclosing a spherical aqueous cavity. They are one of the most extensively studied NPs for drug delivery. By adjusting the concentration of different lipids in the liposome, properties such as surface charge, size, membrane fluidity and stability can be tailored as desired, offering significant flexibility in optimizing the delivery mechanism.¹³² The outer surface can be positively, negatively or neutrally charged. Positively charged liposomes show the highest affinity for the negatively charged bacterial membranes. Additionally, liposomes can also be modified by incorporating proteins, oligosaccharide chains, antibodies or immunoglobulins to target particular ligands.^133,134 This modification enhances specificity, ensuring that non-target microbes remain unaffected. Furthermore, the composition of the liposomal formulation can significantly influence its antimicrobial efficacy. Natsaridis et al. reported that increasing the cholesterol content within the liposomal membrane enhanced the activity of moxifloxacin against Staphylococcus epidermidis biofilms.¹³⁵

Liposomes can effectively deliver both hydrophobic and hydrophilic molecules. They are not targeted by microbial resistance mechanisms and hence protect antimicrobial molecules until delivery.¹³⁶ Research has demonstrated that liposomes enhance the persistence of antibiotics, significantly extending their stability and controlling the rate of diffusion from the vesicle. For instance, ciprofloxacin-loaded liposomes were found to be active up to 48 hours after initial injection.¹³⁷ Additionally, liposomes exhibit low toxicity and reduce the cytotoxic effects of antibiotic agents.¹³⁶ Studies indicate that liposomes enhance the efficacy of antimicrobial agents against resistant bacterial strains, particularly those that modify their cell surfaces, such as P. aeruginosa. For example, lipomycin encapsulated tobramycin has shown an increased bactericidal effect even at sub-MIC concentrations,¹³⁸ and was able to disrupt existing biofilm structures of P. aruginosa.¹³⁹ Other antibiotics, including ofloxacin,¹⁴⁰ polymyxin B,¹⁴¹ and aminoglycosides,¹⁴² have also retained antibacterial activity at sub-MIC concentrations when delivered via liposomes. In the context of antimicrobial-resistant pathogens, liposomal delivery of rifabutin has been shown to significantly reduce the MIC against methicillin-resistant S. aureus.¹⁴³ However, the use of liposomes for drug delivery has some limitations, including low drug loading capacity, potential antibiotic leakage and physicochemical instability.¹³⁶ In addition, the development and production of new liposomes can be prohibitively expensive. Despite these constraints, numerous liposome-based products are available for clinical use.

4.4 Solid lipid NPs

Solid lipid NPs (SLNPs) were developed as an alternative to liposomes, aiming to enhance stability, minimize drug leakage, and improve biodegradability.¹⁴⁴ The biocompatibility of these NPs is significantly greater than that of many other nanocarriers currently under investigation.¹⁴⁵ In addition, SLNPs face fewer regulatory constraints and can be scaled up easily. These NPs consist of colloidal forms of high-melting-stable lipids produced through emulsion or ultrasound dispersion in water or a solvent with similar properties.¹³⁶ Due to their small size, they can bypass cell membranes and enter the cell via endocytosis, allowing direct delivery of the antimicrobial molecule.¹³² SLNs have a higher entrapment efficiency than liposomes and are better suited for long-term storage. Studies have shown that the entrapment efficiency of drugs like tetracaine and etomidate in SLNs ranges from 85 to 99%.¹⁴⁶ Furthermore, ciprofloxacin-incorporating SLNs remained stable for up to 9 months at both 4 °C and 25 °C.¹⁴⁷ Research indicates that drug molecules can undergo either a burst release (as seen with tetracaine and etomidate¹⁴⁴) or a sustained release (as seen with CPX¹⁴⁸), depending on the composition of the SLNPs and the nature of the antibiotic. Taheri et al. demonstrated that although free vancomycin, ampicillin, and CPX exhibited greater inhibitory effects during the initial 24 hours, their solid lipid nanoparticle (SLNP)-encapsulated counterparts achieved superior overall inhibition over a 72 hour period.¹⁴⁹ Notably, SLNs improve the activity of antibiotics such as rifampin against biofilm-producing resistant bacterial strains, potentially by inhibiting efflux pumps and protecting drugs from modifying enzymes.¹⁵⁰ Despite their advantages over liposomes, SLNPs still face limitations, particularly concerning low loading capacity. To address this issue, nanostructured lipid carriers (NLCs) are being explored as a potential solution.¹⁵¹ NLCs are composed of an unstructured matrix polymer that contains either amorphous or imperfect cavities, which allows for improved loading capacity and reduced risk of drug leakage. Additionally, they can be rigidified during storage without compromising entrapment efficiency.¹⁵² However, some studies have reported cytotoxic effects associated with NLCs, indicating the need for further investigation into their biocompatibility.¹⁴⁵ In a pioneering effort, Yadav et al. engineered a label-free electrochemical immunosensor utilizing molybdenum disulfide NPs (nMoS₂ NPs) immobilized on an indium tin oxide (ITO) coated glass surface for the selective detection of ampicillin.¹⁵³ Building on this work, the same group later designed a sensitive immunosensing platform for gentamicin detection by integrating multiwalled carbon nanotubes (MWCNTs) with MoS₂ into a nanocomposite matrix. This nanocomposite was electrophoretically deposited onto an ITO substrate, enhancing both the conductivity and surface area of the sensor for improved analytical performance.¹⁵⁴

4.5 Metal and metal ion NPs

Metal ion NPs form one of the largest categories of NPs currently under investigation, as they possess considerable antibacterial activity, typically bactericidal in nature. Due to their positive charge, they can interact with and disrupt the outer membrane and cell wall of bacteria. In addition, metal ion NPs have been found to promote metal ion release, reactive oxygen species generation,¹³⁶ and denaturation of nucleic acids¹⁵⁵ in bacterial cells. The size of these NPs allows them to penetrate the cells via endocytosis and membrane pores.¹³⁶ Multiple studies have reported the development of resistance against metal NPs.^156,157 However, these resistances were found to be the result of multiple cooperating mutations, whose simultaneous occurrence is unlikely. Furthermore, metal ion NPs serve as effective carriers for antibiotics. When coupled with these NPs, antibiotics demonstrate enhanced antimicrobial activity, reduced MIC, and improved specificity.¹⁰¹

4.5.1 ZnO NPs. ZnO NPs are of significant interest in medical and pharmaceutical fields due to their anti-inflammatory and antimicrobial properties, and they have also been researched for potential use in cancer therapy as well.¹³ These NPs exhibit low MIC against S. aureus and S. typhimurium, but they are notably less effective against P. aeruginosa.¹⁵⁸ A 2022 study demonstrated that ZnO NPs exhibited potent activity against several β-lactam-resistant bacterial strains, including Escherichia coli and Salmonella typhi, primarily through ion-induced oxidation of metabolic components and the β-lactamase enzyme. Notably, a bactericidal effect was observed only at concentrations exceeding 0.24 mg mL⁻¹.¹⁵⁹ Research indicates that ZnO may be less effective against Gram-negative bacteria, possibly due to the presence of thick outer memberanes.¹⁶⁰ Additionally, ZnO NPs have been shown to disrupt the biofilm formation in regular strains and methicillin-resistant strains of S. aureus.^161,162

A 2010 study by Thati et al. investigated the interaction of ZnO NPs with 25 different antibiotics, measuring their efficacy against S. aureus. Most antibiotics tested, including β-lactams, cephalosporins, aminoglycosides, and tetracyclines, showed increased inhibition zones during disk diffusion, with penicillin, amoxiclav, and amikacin demonstrating the most significant improvements. In contrast, norfloxacin and clarithromycin exhibited minimal increases in efficacy.¹⁶³ However, the same year, Banoee et al. reported that amoxicillin and penicillin G displayed decreased activity against S. aureus, while ciprofloxacin showed a 27% increase in its inhibition zone.¹⁶⁴ Experiments by Ghasemi and Jalal found that ZnO NPs significantly increased the zone of inhibition of ceftazidime against A. baumannii to 33 nm, in contrast to 0 nm for the free antibiotic molecule.¹⁶⁵ Shokrollahi et al. similarly demonstrated improved efficacy for cefotaxime, with the highest inhibition occurring at a concentration of 32 μg mL⁻¹.¹⁶⁶ This could be attributed to ZnO NPs disrupting the function of NorA proteins, which are essential components of efflux pumps in S. aureus.¹⁶⁷ Meropenem delivered via ZnO NPs was shown to completely inhibit biofilm formation by P. aeruginosa, accompanied by a significant downregulation of biofilm-associated gene expression. In vivo administration of this formulation effectively cured P. aeruginosa-induced keratitis in rat models.¹⁶⁸ ZnO NPs have been classified as “generally regarded as safe” by the US Food and Drug Administration for use in food and agricultural industries, owing to their low toxicity and high biocompatibility.

4.5.2 Silver (Ag) NPs. Historically, Ag has been used as an antimicrobial agent since at least 1000 BC. A study in 1869 revealed that Ag could exert antimicrobial effects at very low concentrations.¹⁶⁹ Since then, the use of Ag ions and Ag salts has become widespread in pharmaceutical and agricultural fields. Ag NPs also demonstrate strong bactericidal properties and are increasingly used in medicine, electronics and sanitation as antimicrobial agents.¹⁷⁰ Although the precise mechanism behind the antibacterial activity of Ag NPs is not yet fully understood, several theories have been proposed. Similar to other metal ions, Ag NPs can interact with and penetrate bacterial cell membranes, altering their structure and increasing permeability. Analysis of Ag NPs’ action on E. coli revealed the formation of ‘pits’ in the cell wall, in which NPs accumulated.¹⁷¹ These enhance the uptake of Ag ions into the cell, where generation of reactive oxygen species,⁹⁷ denaturation of ribosomes, and alteration of DNA have been observed.^172,173 Ag NPs exhibit strong inhibitory effects against yeast (MIC 6.6 nM–3.2 nM) and E. coli (MIC 3.3 nM–6.6 nM), while showing only mild inhibition towards S. aureus (MIC 33 nM). The rate of growth inhibition is dependent on the concentration of Ag.⁹⁷ Furthermore, Ag NPs have demonstrated antimicrobial activity against resistant bacterial strains, including methicillin-resistant S. aureus and methicillin-resistant Staphylococcus epidermidis.¹⁷⁴ Studies combining Ag NPs with antimicrobial peptides have demonstrated a synergistic effect, resulting in enhanced antimicrobial activity of both components against methicillin-resistant S. aureus.¹⁷⁵ These NPs can also serve as carriers for antibiotic drugs. For instance, when amoxicillin was delivered using nano Ag, its MIC decreased from 0.525 mg ml⁻¹ to 0.150 mg ml⁻¹.¹⁷⁶ Ag NPs loaded with ciprofloxacin showed reduced MIC and a decrease in resistance-generating mutations in P. aeruginosa, with effects enhanced by adjuvants such as CS and betamethasone.¹⁷⁷ Ciprofloxacin-loaded Ag NPs also exhibited enhanced antibacterial efficacy against Acinetobacter baumannii and Serratia marcescens, producing inhibition zones of 36 mm and 40 mm, respectively.¹⁷⁸ Additionally, vancomycin, erythromycin, and penicillin G also showed increased antibacterial activity against S. aureus.¹⁷⁹ Cytotoxicity assessments conducted on a range of in vitro and in vivo models, including human macrophages, HeLa cells, and mouse stem cells, revealed no cytotoxic effects at bactericidal concentrations of Ag NPs. However, higher concentrations were found to reduce cell viability.¹⁸⁰ Further, Zheng and colleagues developed a nanocomposite consisting of lanthanum hydroxide integrated with graphene oxide (La@GO), which demonstrated a potent synergistic antibacterial effect against multiple resistant bacterial strains.¹⁶⁸ Notably, prolonged exposure of antimicrobial-resistant E. coli to sub-inhibitory concentrations of La@GO did not induce any measurable development of secondary resistance. In contrast, repeated treatment with conventional antibiotics or Ag NPs resulted in a significant increase in bacterial tolerance, ranging from 16- to 64-fold [Fig. 8].

Fig. 8 Engineered lanthanum hydroxide and graphene oxide NCs (La@GO/R2) inhibit the evolution of AMR. (A) Confocal microscopy images showing the peptidoglycan layer of multidrug-resistant (MDR) E. coli labelled in situ with a fluorescent D-amino acid after treatment with La@GO, Ag NPs, and norfloxacin; (B) nano-CT scans of E. coli treated with La@GO; (C) transmission electron microscopy (TEM) images of antimicrobial-resistant E. coli treated with La@GO; (D) the trajectory of AMR evolution in MDR E. coli was tracked by exposing the bacteria to La@GO, Ag NPs, and Nor for 30 days at MIC; (E) development of resistance on exposure to La@GO, AgNPs and Nor; and (F) evaluation of cross-resistance development in E. coli after 30 days of exposure (reproduced with permission from ref. 181, @ 2019, American Chemical Society).

4.5.3 Copper (Cu) NPs. Due to the wide availability of Cu, Cu NPs are being researched as another alternative for combating AMR. However, their usage is limited as they oxidize rapidly in the presence of air or aqueous media, which significantly decreases their stability and antimicrobial ability.¹⁸² Similar to other metal NPs, Cu NPs also form ‘pits’ in the bacterial cell wall, which allows them to accumulate and penetrate the cell, while destabilizing the stability of the bacterial membranes.¹⁸³ A 2013 study revealed the presence of reactive oxygen species and degraded DNA molecules in E. coli cells treated with Cu NPs. It was suggested that oxidation of cupric ions promotes the generation of reactive oxygen species, which subsequently causes DNA degradation and protein oxidation.¹⁸⁴ Cu NPs have demonstrated efficacy against antimicrobial-resistant pathogens, with Wang et al. reporting activity against methicillin- and vancomycin-resistant Staphylococcus aureus strains¹⁸⁵ [Fig. 9(2)]. They also contribute to biofilm disruption, inhibiting 49% and 59% biofilm formation in Klebsiella oxytoca and E. coli bacterial strains, respectively.¹⁸⁶

Fig. 9 (1) Illustration of synergistic antibacterial activity of Cu sulfate (CuSO₄) and colloidal Ag NPs (cAg) against Escherichia coli K12 (reproduced with permission from ref. 188, @ 2023, Springer Nature); (2) schematic representation of the fabrication and evaluation of PAN-Cu nanoparticle-based nanofibers and their antibacterial performance through in vitro microbiological assays to determine their potential against bacterial pathogens (reproduced with permission from ref. 185, @ 2022, MDPI); (3) schematic overview of the synthesis and characterization of β-cyclodextrin-stabilized Au NPs (β-c-AuNPs) and their antimicrobial evaluation against Staphylococcus aureus and Candida albicans, demonstrating their broad-spectrum antimicrobial potential (reproduced with permission from ref. 197, @ 2023, MDPI); and (4) UV-vis absorption spectra of NPs synthesized using P (a), M (b), and PMC (c), indicating successful formation and distinct optical properties of each formulation. The antimicrobial efficacy of PMC-NPs was further validated through agar diffusion assays, showing clear inhibition zones against Escherichia coli and Staphylococcus aureus (i), in comparison to a standard positive control (ii) (reproduced with permission from ref. 206, @ 2019, Elsevier).

Cu NPs have a synergistic effect with antibiotics, and the efficiency of both is found to increase in combination. A study exploring the action of different antibiotics in the presence of Cu NPs found that the antibacterial activity of ampicillin, amoxicillin and ciprofloxacin was increased against multiple Gram-positive and Gram-negative species, including E. coli, M. luteus, and S. typhi. In the same study, gentamycin showed only a mild increase in activity.¹⁸⁷ Cu NPs also benefit when co-delivered with other metallic NPs. A 2023 study demonstrated that the combined administration of Cu and Ag NPs significantly improves the performance of both¹⁸⁸ [Fig. 9(1)]. A growing concern about the use of Cu NPs is their cytotoxicity. NPs can easily penetrate organs through their membranes due to their size. While data are limited, a study reported that accumulation of Cu NPs in mice caused damage to multiple organs, including the liver, kidney and spleen.¹⁸⁹ Similarly, another study focusing on nasal administration of NPs to mice found that repeated exposure caused inflammation of lung tissues and degradation of nasal epithelial cells.¹⁹⁰

4.5.4 Gold (Au) NPs. The antimicrobial effects of Au NPs are multi-faceted and target numerous aspects of the cell. By interacting with the cell wall and cell membrane, these NPs increase the membrane permeability and cause leakage of cellular contents. Proteins such as adenosine triphosphate synthetases and nicotinamide adenine dinucleotide dehydrogenases are inhibited, leading to a disruption of metabolic activities and death of the bacterial cell. Furthermore, they prevent the binding of ribosomes to tRNA, blocking the membrane synthesis mechanism. Au NPs also enhanced chemotaxis and attacked phosphorus-containing sites in DNA molecules.¹⁹¹ A 2016 study examined the effects of Au NPs on the growth of various bacterial species, reporting a growth reduction of 53.19% in S. aureus, 68.1% in E. coli, 49.4% in B. subtilis, and 13.8% in K. pneuomoniae.¹⁹² When conjugated with Au NPs, the antibiotics streptomycin and kanamycin demonstrated a significant decrease in MIC against E. coli, M. luteus, and S. aureus, while amoxicillin showed only a slight decrease.¹⁹³ Additionally, ampicillin-coated Au NPs exhibited enhanced antimicrobial activity against methicillin-resistant S. aureus and drug-resistant strains of P. aeruginosa and E. aerogenes.¹⁹⁴ Delafloxacin, a fluoroquinolone antibiotic, exhibited enhanced antibacterial activity when delivered via Au NPs, with MIC reduced by 12.77 μg mL⁻¹ against Escherichia coli, 13.51 μg mL⁻¹ against Pseudomonas aeruginosa, 22.52 μg mL⁻¹ against Staphylococcus aureus, and 33.21 μg mL⁻¹ against Bacillus subtilis.¹⁹⁵ Vancomycin, too, experienced up to a 1.8-fold increase in efficacy against E. coli, K. oxytoca, and P. aeruginosa.¹⁹⁶ Khan et al. reported that β-caryophyllene-functionalized Au NPs effectively disrupted a mixed biofilm formed by fungal C. albicans and bacterial S. aureus species, in a concentration dependent manner¹⁹⁷ [Fig. 9(3)]. These NPs can also be functionalized with polymers, such as CS. Oligosaccharide-capped Au NPs were demonstrated to inhibit biofilm development and disrupt existing biofilm structures in P. aeruginosa.¹⁹⁸ One key advantage of Au over other metal ion NPs is the absence of reactive oxygen species generation, which reduces the toxicity towards mammalian cells while retaining bactericidal abilities.¹⁹¹ The chemical inertness of Au further enhances its biocompatibility, allowing for easy functionalization with different ligands to improve specificity.¹³ However, there is insufficient data regarding interactions and kinetics of Au NPs in vivo, largely due to a lack of clinical trials.¹⁹⁹

4.5.5 Titanium NPs. Titanium NPs possess great potential as antimicrobial agents due to their high stability and low risk of corrosion.¹³⁶ These NPs act by progressively increasing the permeability of the cell membrane, causing a significant leakage of intracellular components such as potassium ions, RNA and proteins. Microscopic analysis showed additional degradation of the cell wall and outer membrane. Reactive oxygen species are also produced through oxidative stress under stimulation by UV light. These properties target DNA molecules and proteins involved in metabolic processes, causing bactericidal effects.²⁰⁰ Titanium oxide NPs were found to inhibit biofilm synthesis in methicillin-resistant Staphylococcus aureus and disrupt existing biofilm structures.¹⁶¹ The conjugation of titanium NPs with ZnO NPs enhances the antimicrobial activity of both against Gram-negative E. coli and P. aeruginosa, as well as Gram-positive S. aureus and B. subtilis.²⁰¹ A study investigating the effect of titanium NPs on 23 antibiotic molecules found that the zone of inhibition increased for all antibiotics tested, including penicillin, amikacin, ampicillin, and gentamycin, except for nalidixic acid, which showed minimal improvement.²⁰²

Research suggests that titanium may have potential cytotoxicity at the nanoparticle scale. A 2010 report from the International Agency for Research on Cancer classified titanium dioxide (TiO₂) as a potential carcinogen, noting sufficient evidence of carcinogenicity in animals but insufficient data in humans.²⁰³ Further analysis of titanium's cytotoxicity is necessary before it can be considered for clinical trials.

4.5.6 Magnetic NPs. Magnetic NPs are a distinct group characterized by similar physicochemical properties, primarily composed of iron oxides, iron-metal oxides or their derivatives. These NPs are particularly intriguing due to their superparamagnetic properties, which enable controlled delivery through magnetic fields.²⁰⁴ Studies involving E. coli in the presence of iron NPs have reported increased oxidative stress and the generation of reactive oxygen species via the Fenton reaction. This causes the disruption of metabolic processes and inhibition of protein synthesis, leading to cell death.²⁰⁵ Iron NPs exhibit bactericidal effects against multiple bacterial species, including S. aureus, E. coli, P. aeruginosa, S. typhi and P. multocida, often with MICs lower than that of most antibiotics. Notably, they show greater efficacy against Gram-positive as compared to Gram-negative bacteria²⁰⁶ [Fig. 9(4)].

Research on the delivery of streptomycin using CS-coated magnetic NPs demonstrated enhanced activity against Gram-negative E. coli and P. aeruginosa.²⁰⁴ Functionalized iron oxide NPs were found to be effective at disrupting biofilm formation of E. coli and S. aureus.²⁰⁷ Additionally, NPs composed of cobalt ferrite (CoFe₂O₄) and barium ferrite (BaFe₁₂O₁₉) exhibited antimicrobial activity against both E. coli and S. aureus, as well as fungal pathogens like C. albicans and F. oxysporum.²⁰⁸ Vancomycin-conjugated magnetic NPs significantly reduced the MIC from 250–4000 μg mL⁻¹ for standard vancomycin molecules to 13–28 μg mL⁻¹ for the conjugated form, with membrane permeabilization observed within 2 hours, which was not detected for non-conjugated vancomycin.²⁰⁹ Research on mouse fibroblast cells indicates that at low concentrations, magnetic NPs do not show cytotoxicity.²¹⁰ The US FDA has approved the use of a few magnetic NPs for applications in MRI imaging and cancer therapy;²¹¹ however, further research is needed to explore their potential as antimicrobial agents.

4.5.7 Cobalt NPs. The use of cobalt NPs for antimicrobial treatment has gained significant interest over the past decade following the discovery of their antimicrobial properties.²¹² Cobalt, similar to most metallic ions, is bactericidal, and exerts its biological effects primarily through the disruption of cellular membranes, generation of reactive oxygen species, and interference with protein synthesis and transcription.²¹³ However, the available data are still limited and insufficient for advancing clinical trials. Dogra et al. showed that cobalt-containing oxide and hydroxide NPs dramatically reduced the number of colony-forming units (CFUs) of S. aureus by 72%–98% in overnight culture.²¹⁴ When tested against various Gram-positive and Gram-negative bacteria, cobalt oxide NPs exhibited a low MIC of 31.25 μg ml⁻¹ against E. coli and S. aureus, while the MIC against P. aeruginosa was higher at 250 μg ml⁻¹. In contrast, the antibiotic gentamicin outperformed all samples, with a MIC of 10 μg ml⁻¹. Additionally, UV illumination significantly enhanced the antibacterial activity of cobalt NPs across all tested instances.²¹⁵ Interestingly, another study indicated that cobalt NPs surpassed gentamicin, cefotaxime, ciprofloxacin, and amoxicillin in effectiveness against multidrug-resistant E. coli, and were only outperformed by ciprofloxacin in multidrug-resistant S. aureus.²¹⁶ Moreover, in vitro tests of cobalt NPs demonstrated low cytotoxicity, with peripheral blood mononuclear cells showing over 80% cell viability up to 300 μg mL⁻¹ concentrations, and thus cobalt NPs are considered safe for non-cancerous human cells.²¹⁷ Nevertheless, further research on biocompatibility and in vivo kinetics is essential before initiating clinical trials for cobalt nanoparticle-based drugs.

4.5.8 Other metallic NPs. Numerous other metal ion NPs have been studied for potential use as antimicrobial agents. However, research on these NPs is limited. Selenium NPs, for instance, inhibited the growth of S. aureus (63% inhibition) and E. coli (46% inhibition) after 24 hours of incubation, with maximum inhibition at 50 ppm concentration. The study also conducted cytotoxicity assays on the NPs, reporting that after increasing the concentration to 50 ppm, 70% of human cells remained viable.²¹⁸ Lara et al. demonstrated the ability of CS-coated selenium NPs to disrupt pre-formed biofilms in the fungus C. albicans, reducing the IC₅₀ from 21.7 ppm (naked NPs) to 3.5 ppm.²¹⁹ Ridha et al. showed that selenium NPs conjugated with levofloxacin and amikacin exhibited MICs 10–20 times lower than those of the free antibiotics against S. aureus, E. faecalis, P. aeruginosa, and E. coli, indicating enhanced antibacterial efficacy and efficient drug delivery.²²⁰ Geoffrion et al. found that methicillin-resistant S. aureus and multidrug-resistant E. coli showed dose-dependent inhibition in response to naked selenium NPs, with MIC values of 14.26 and 2.35 ppm, respectively. This indicates potential bacteriostatic and bactericidal effects that can be applied against drug-resistant bacteria. However, in vitro cytotoxicity assays were conducted only up to 1 ppm concentration, and the toxicity of MIC concentrations was not determined.²²¹ Huang and colleagues developed a rapid, one-step synthesis method to produce Se NPs functionalized with the antimicrobial peptide ε-poly-L-lysine (ε-PL). These engineered NPs exhibited a strong positive surface charge, which contributed to their potent antimicrobial activity. The ε-PL-Se NPs were highly effective against a broad spectrum of microbial pathogens, including both Gram-positive and Gram-negative bacteria such as E. coli, S. aureus, E. faecalis, and P. aeruginosa as well as their drug-resistant strains and the fungal species C. albicans. The minimum fungicidal concentration (MFC) of 10PL-Se NPs over C. albicans was 26 ± 10 μg mL⁻¹ (ref. 222) [Fig. 10].

Fig. 10 In a study, polylysine-coated NPs showed bactericidal activity against numerous Gram-negative and Gram-positive bacteria including E. coli, S. aureus, E. faecalis, and P. aeruginosa. Here, 5PL-Se NPs and 10PL-Se NPs denote 5 mg ml⁻¹ and 10 mg ml⁻¹ polylysine-coated selenium NPs, whereas ε-PL denotes antimicrobial peptide–poly-L-lysine stabilized Se NPs (reproduced with permission from ref. 222, @ 2024, American Chemical Society).

Cadmium oxide NPs have been shown to have a significant inhibitory effect on S. aureus, K. pneumoniae, A. baumannii and P. aeruginosa bacteria grown in nutrient agar media. This effect was reported to be greater than that of Cu NPs.²²³ A similar study with cadmium sulfide NPs demonstrated concentration-dependent inhibition of E. coli and S. aureus colonies; however the zone of inhibition was smaller than that of regular tetracycline molecules.²²⁴ While cadmium ferrite NPs were reported to have no notable activity on Gram-negative bacteria, calcium cadmium ferrite NPs inhibited the growth of both Gram-positive and Gram-negative bacterial species.²²⁵

Silica NPs do not possess antibacterial properties; rather, they serve as carriers for antibiotics or work synergistically with other metals. For example, penicillin loaded into Ag-silica NPs reduced the MIC against methicillin-resistant S. aureus from 335 μg ml⁻¹ to 130 μg m⁻¹.²²⁶ Additionally, the delivery of vancomycin and polymixin B via mesoporous silica NPs enhanced the antibacterial activity and lowered the MIC against five species of bacteria: E. coli, S. aureus, K. oxytoca, A. baumannii, and P. aeruginosa.²²⁷ Ciprofloxacin-loaded silica NPs inhibited biofilm formation of Salmonella typhimurium by 50% and reduced the MIC to 0.03125 mg L⁻¹.²²⁸

Chaudhary et al. developed a highly sensitive and selective electrochemical immunosensor utilizing lanthanum oxide NPs (nLa₂O₃ NPs) for the detection of trace levels of the antibiotic ciprofloxacin (CPX).²²⁹ In a subsequent study, the group introduced an advanced biosensing platform incorporating a nanocomposite of nLa₂O₃ NPs anchored onto reduced graphene oxide (nLa₂O₃ NPs@rGO). This label-free sensor exhibited enhanced performance for the efficient electrochemical detection of CPX, benefiting from the synergistic properties of the nanomaterials used.²³⁰ Cadmium, silica, selenium and lanthanum NPs are the most prominent among the numerous metal ions under investigation for antimicrobial activity. However, data regarding in vivo activity, cytotoxicity, long-term effects, and potential side effects are limited. Until further studies are conducted, clinical trials for the treatment of infections cannot be performed.¹³⁶

4.6 Carbon dots

Carbon dots (CDs) are carbon NPs that are characterized by their fluorescence properties and surface functionalization. They are small (less than 10 nm in diameter) and are used in a variety of fields, including cell imaging and drug delivery.²³¹ They were first discovered in 2004²³² and quickly generated interest due to the presence of numerous surface groups, which allowed conjugation with a wide range of ligands and molecules. These NPs also possessed high stability and low toxicity, making them perfect for use in medical fields.²³³ A simple and eco-friendly one-step hydrothermal approach was employed to synthesize blue-fluorescent carbon dots using the pulp extract of Ziziphus mauritiana as a natural carbon source. These biogenic CDs were utilized as an optical probe for the sensitive detection of the antibiotic ciprofloxacin.²³⁴ It has been demonstrated that carbon dots reduce inflammation by preventing the generation of pro-inflammatory cytokines. One study reported that the anti-inflammatory effect of aspirin-conjugated carbon dots was higher than that of aspirin molecules alone.²³⁵ The antibacterial effects of carbon dots were first reported in 2016,²³⁶ and are primarily bactericidal. They interact with the cellular barrier of bacteria and fungi through electrostatic interactions, causing damage to the cellular membranes. In addition, they promote the generation of reactive oxygen species, which further destabilizes the cell wall and causes cellular leakage. Carbon dots were also found to inhibit protein synthesis mechanisms, disrupt electron transport in the membrane,²³⁷ and bind with DNA molecules and destroy their secondary structures.²³⁸

The antimicrobial activity of carbon dots was displayed against E. coli and S. aureus, with greater inhibition observed for E. coli.²³⁹ Carbon dots loaded with levofloxacin, an antibiotic to which pathogens typically develop rapid resistance, demonstrated enhanced activity against multiple species of Staphylococcus bacteria, including methicillin-resistant S. aureus.²⁴⁰ The conjugation of ciprofloxacin with carbon dots resulted in a significant enhancement of the antibiotic's effectiveness, achieving a loading capacity of 90%.²⁴¹ Additionally, amine-terminating carbon dots functionalized with ampicillin increased antibacterial activity by generating additional reactive oxygen species. The presence of the target E. coli cells was detectable through UV-stimulated fluorescence of the carbon dots.²⁴² Carbon dots have also shown promise against antimicrobial-resistant infections. A 2020 study revealed their ability to inhibit multiple drug-resistant Enterococcus bacteria.²⁴³ Furthermore, another study demonstrated that penicillin-conjugated carbon dots exhibited antibacterial activity against methicillin-resistant S. aureus and multidrug-resistant E. coli, with no associated cytotoxicity.²⁴⁴ However, certain limitations remain in the research on carbon dots. Most of the studies show that carbon dots exhibit lower efficacy compared to conventional antibiotics, limiting their potential as effective replacements. Furthermore, the risk of AMR induced by exposure to carbon dots has not yet been sufficiently analysed.²⁴⁵

4.7 Dendrimers

Dendrimers are synthetic polymers consisting of multiple monomers branching from a central core. This greatly increases the number of ligand binding sites available, allowing for functionalization with multiple copies of a drug. The distribution and in vivo properties of dendrimers can be controlled by modifying the size and structure of the polymer.²⁴⁶ Due to their dendritic structures, these NPs exhibit a high degree of resistance to enzymatic hydrolysis and proteolytic degradation, which can otherwise degrade their monomeric constituents. This structural advantage contributes to their enhanced stability in vivo, thereby improving their potential for biomedical applications.²⁴⁷ Dendrimers act through the depolarization and lysis of the membranes of bacterial cells. The positively charged functional groups of dendrimers interact with negatively charged components of the membranes, and on contact, the dendrimers are fragmented. The fragments are inserted into the membrane, where disruption occurs. In addition, the dendrimers interfere with metabolic processes, including glycolysis, by inhibiting the synthesis of key proteins.²⁴⁸ Depending on the design, structure and functional groups used, dendrimers can show both bactericidal and bacteriostatic activity.

Amine-terminating poly(amidoamine) dendrimers inhibited the growth of P. aeruginosa at very low concentrations (MIC 1.5 μg mL⁻¹) and S. aureus at higher concentrations (MIC 20.8 μg mL⁻¹). These dendrimers were reported to be toxic to human corneal epithelial cells; however coating them with PEG significantly reduced the toxicity.²⁴⁹ A study of peptide dendrimers functionalised with fatty acids showed that dendrimers had increased activity against multiple-drug-resistant E. coli, P. aeruginosa, A. baumannii and methicillin-resistant S. aureus. Cytotoxicity assays of these dendrimers showed compatibility with multiple mammalian and human cell lines.²⁵⁰ Another study of organometallic dendrimers reported the antimicrobial activity of these dendrimers against methicillin-resistant S. aureus, S. warnerii, and vancomycin-resistant E. faecium, but they did not have any activity against C. albicans, P. aeruginosa and P. vulgaris.²⁵¹ Dendrimers are also used as drug delivery vehicles. Sulfamethoxazole delivered using poly(amidoamine) dendrimers was found to have greater solubility, a slight improvement of activity against E. coli, and sustained release over a longer time period.²⁵² The use of poly(amidoamine) dendrimers for erythromycin and tobramycin showed improved solubility but no significant increase in antimicrobial activity against multiple bacterial strains, including S. aureus, P. aeruginosa and E. coli.²⁵³ Several studies have also demonstrated that dendrimers possess the ability to inhibit and disrupt biofilms formed by a range of bacterial and fungal species, including S. aureus and P. aeruginosa.²⁵⁴

Cytotoxicity assays of different dendrimers show high variation in the level of toxicity towards various human cell lines. Multiple studies have reported hemolysis, neurological toxicity, and toxicity against renal and digestive organs. In addition, the consistency of dendrimer synthesis is difficult to achieve. Due to this, the current applications of dendrimers in medical fields are limited.²⁵⁵

4.8 Hydrogels

Hydrogels are three-dimensional hydrophilic polymers that typically contain or can absorb large quantities of water.²⁵⁶ Hydrogel NPs are advantageous as antibiotic carriers as they are biocompatible and biodegradable, making them less prone to cytotoxicity. Most hydrogels release drugs through passive diffusion and hence sustain the antibiotic presence in the body. The rate of diffusion can be controlled by the proportion of cross-linkage of the NPs. Hydrogels can also be modified to release the drugs only in response to specific stimuli, including temperature, light, sound, electromagnetic fields and pressure.²⁵⁷

Lee et al. developed antimicrobial hydrogels by combining an ABA-type triblock copolymer – PEG flanked by vitamin E-functionalized polycarbonate blocks – with a biocidal cationic polycarbonate also containing vitamin E. Both components were synthesized via ring-opening polymerization of functionalized cyclic carbonate monomers. Hydrogel formation relies on hydrophobic interactions between vitamin E moieties, enabling broad-spectrum antimicrobial activity and effective biofilm dispersion. The hydrogels demonstrated over 99.9% killing efficiency against S. aureus, E. coli, and C. albicans upon contact, showcasing potent broad-spectrum antimicrobial activity (Fig. 11).²⁵⁸ Ciprofloxacin-loaded hydrogels were demonstrated to have sustained release of antibiotics against methicillin-resistant S. aureus, with a notable increase in antimicrobial activity as well.²⁵⁹ Amikacin delivered using an alginate-derived hydrogel possessed significantly increased activity against E. coli, S. epidermidis, S. aureus, and P. aeruginosa at only 1.43% amikacin content, with a notable decrease in MIC. Assays of these hydrogels performed in mice also showed no cytotoxicity.²⁶⁰ Antibiotics can also be released by hydrogel degradation, which results in a burst release. This reduces the persistence of the antibiotic. To avoid this, studies suggest using a two-step release mechanism, where the antibiotic is conjugated with another nanoparticle before loading, which restores the persistence of the drug.²⁶¹ Despite the low toxicity, multiple studies have reported the generation of immune responses against hydrogels, particularly those synthesized from biomaterials or functionalized with PEG. Hydrogels are also subject to high batch variation during synthesis, due to which they are considered unreliable for commercial production.²⁶² Table 1 presents a comprehensive overview of the antimicrobial mechanisms exhibited by different types of nanoparticle materials against various pathogenic microorganisms. The table highlights the diversity of nanomaterials, such as metal-based, metal oxide, carbon-based, and polymeric NPs, along with their mode of action, including ROS generation, membrane disruption, ion release, biofilm inhibition, and intracellular targeting. These mechanisms collectively contribute to the broad-spectrum efficacy of nanomaterials and underline their potential as alternative or complementary agents to conventional antibiotics in combating AMR.

Fig. 11 (A) Synthesis of ‘(MTC-VE)_n–PEG–(MTC-VE)_n’ and vitamin E-based cationic polymers, along with a schematic representation of their incorporation into the hydrogel system and (B) SEM images of biofilms exposed to polycation-loaded (MTC-VE)_1.25–PEG(20k)–(MTC-VE)_1.25 hydrogels (reproduced with permission from ref. 258, @ 2012, Elsevier).

Further, Table 2 provides a comparative summary of the bacteriostatic and bactericidal effects exhibited by various nanomaterials commonly explored for antimicrobial applications. Several nanomaterials, such as CS, AgNPs, ZnO NPs, and dendrimers, demonstrate both bacteriostatic (inhibition of bacterial growth) and bactericidal (bacterial killing) properties, depending on their physicochemical characteristics, concentration, and the type of microorganism targeted. In contrast, materials like AuNPs and carbon dots primarily exhibit bacteriostatic behavior, often requiring functionalization or combination with other agents to achieve bactericidal action. This distinction is critical for selecting appropriate nanomaterials for specific clinical or environmental applications, especially when considering the severity of infection, pathogen type, and potential resistance mechanisms.

Table 2 Bacteriostatic and bactericidal effects of nanomaterials

Nanomaterial type	Effect
CS	Bacteriostatic	Bactericidal
Ag NPs	Bacteriostatic	Bactericidal
Au NPs	Bacteriostatic	—
ZnO NPs	Bacteriostatic	Bactericidal
Dendrimers	Bacteriostatic	Bactericidal
Carbon dots	Bacteriostatic	—

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5. Limitations of nanotechnology-based approaches

Despite the promising potential of nanotechnology in addressing AMR, several limitations hinder its clinical translation and widespread application. One major concern is the toxicity and biocompatibility of certain NPs, especially those composed of heavy metals such as Ag, Cu, or ZnO. These materials, while effective against microbes, may induce oxidative stress, inflammation, or cytotoxic effects in host tissues. Additionally, long-term safety data are often lacking, raising concerns about bioaccumulation and unintended ecological impacts following environmental release. Another challenge lies in the scalability and reproducibility of nanoparticle synthesis, which can result in batch-to-batch variations affecting consistency in therapeutic outcomes.²⁷⁵ The complexity of regulatory approval processes for nanomaterials also slows down clinical implementation, as existing frameworks may not fully accommodate the unique properties of nanomedicines. Moreover, bacteria may eventually develop resistance mechanisms even against nanoscale antimicrobials, particularly if these systems are overused or misapplied. Finally, cost-effectiveness and integration into existing healthcare systems remain significant hurdles, especially in low-resource settings where AMR is most prevalent. Addressing these limitations through rigorous toxicological studies, standardization of nanoparticle synthesis, and multidisciplinary regulatory efforts will be essential for realizing the full potential of nanotechnology in AMR mitigation.

5.1 Nanoparticle cytotoxicity

A significant limitation of many cytotoxicity assays is that they are conducted in vitro, using cultured cell lines. While this approach provides insights into nanoparticle effects on individual cells, it fails to account for the interactions between different cell types within organs, which are crucial for accurately reflecting in vivo effects on the host system. Despite this limitation, in vitro toxicity assays remain essential for assessing the potential risks of NPs.²⁷⁶ The toxicity of NPs is influenced by various characteristics, including size, shape, and charge, all of which depend heavily on the synthesis process, where consistency is often not guaranteed.²⁷⁷ Due to their small size, NPs can easily penetrate host cells and organs, demonstrating the ability to infiltrate the liver, spleen, and even the blood–brain barrier. When accumulated in high concentrations, they can generate reactive oxygen species that may cause significant damage to these organs.²⁷⁸ Additionally, NPs have been associated with hemolysis and thrombogenicity in blood cells.²⁷⁹ Most nanoparticle therapies are delivered to their site of action through bloodstream. The liver, functioning as a filter for blood impurities, often becomes a common site for nanoparticle accumulation. While studies have shown that Kupffer cells and sinusoidal epithelial cells can remove these particles, this process is relatively slow. Prolonged exposure to NPs can negatively affect the metabolic pathways of liver cells, with consequences that may last for several months. Furthermore, the neutralization of NPs by Kupffer cells can trigger the synthesis of pro-inflammatory cytokines, leading to liver inflammation.²⁸⁰

Another important concern is immunotoxicity. NPs are frequently functionalized with biomolecules such as proteins, oligosaccharides, and immunoglobulins to enhance drug delivery specificity. However, these ligands can provoke an immunogenic response in the host. Additionally, opsonization of the NPs by plasma proteins may activate the immune system, resulting in further inflammation of body tissues.²⁸¹

5.2 Nanoparticle resistance

As research on AMR progresses, a growing concern is the potential development of resistance to the alternative treatment methods currently under investigation. NPs, particularly metal ion NPs, typically exhibit antimicrobial activity by disrupting various aspects of bacterial cells, including cell membranes, protein synthesis, electron transport, and DNA transcription. Consequently, the emergence of resistance to NPs requires multiple mutations within the bacterial cell, making it less likely than traditional AMR. Furthermore, the diverse targeting mechanisms of NPs diminish the risk of simultaneous resistance to multiple nanoparticle types.²⁸² Despite this, several studies have reported the development of resistance to NPs.²⁸³ For instance, genomic analysis of E. coli exposed to Ag NPs revealed that three mutations conferring resistance spread throughout the population within 200 generations.²⁸⁴ Common mechanisms of resistance include mutations that alter membrane permeability and changes in biofilm composition.²⁸³ Additionally, adjustments in efflux pumps to expel metal ion NPs have been observed.²⁸² Notably, these resistance adaptations can be transferred between bacterial cells through horizontal gene transfer.

Nanotechnology holds significant promise in addressing AMR, with numerous studies highlighting its potential in combating resistant pathogens. However, translating laboratory successes into clinically viable systemic treatments requires substantial further research and investment. One of the primary challenges in the in vivo application of NPs is their complex interaction with the human body. When administered intravenously, NPs must overcome biological barriers, including clearance by phagocytic immune cells. NPs smaller than approximately 10 nm are rapidly filtered out by the kidneys, whereas those larger than 200 nm are prone to activating the complement system, potentially triggering undesirable immune responses. To improve their pharmacokinetic properties, polyethylene glycol (PEG) is frequently used to modify NPs, a process known as PEGylation. This “stealth” coating enhances solubility, extends circulation time, and reduces recognition by the immune system. However, pre-existing anti-PEG antibodies, possibly acquired through environmental or non-medical exposure, may compromise the effectiveness of PEGylated formulations. Additionally, the stability of NPs in the bloodstream is influenced by their composition. Lipid- and polymer-based NPs, for example, are more prone to aggregation and colloidal instability. To address this, surface modifications such as cross-linking with polymers and PEGylation are commonly employed to enhance stability and improve therapeutic performance. Research into nanoparticle resistance is still ongoing, and the conditions leading to its development are not yet fully understood. Identifying the factors that contribute to this resistance and exploring potential strategies to mitigate it are crucial for preserving the efficacy of NPs as antimicrobial agents. Fig. 12 outlines key limitations of nanomaterial-based strategies, including cytotoxic effects on host cells, ecological impact, suboptimal encapsulation efficiency, high costs of synthesis and characterization, and the emergence of resistance to nanomaterials. Additional concerns involve nanoparticle aggregation and bioaccumulation, batch-to-batch variability in formulation, and the lack of comprehensive long-term safety data. These factors hinder the widespread and sustainable application of nanotechnology in clinical and environmental settings.

Fig. 12 Limitations of nanotechnology-based approaches for drug delivery against antimicrobial resistant pathogens.

5.3 Toxicological and ecological risks within a one health framework

The use of NPs to combat AMR within a one health framework holds significant promise but also raises critical concerns regarding their toxicological impacts and ecological risks across human, animal, and environmental domains.

5.3.1 Potential toxicological impacts. Certain NPs, such as AgNPs, have been shown to induce adverse biological effects in mammalian systems. For example, AgNPs can impair cellular antioxidants, leading to increased ROS accumulation, mitochondrial and DNA damage, lipid peroxidation, apoptosis, and ultimately, impaired reproductive functions such as reduced sperm quality and hormone production. These effects are especially concerning given the widespread use and environmental release of AgNPs, which can result in unintended human exposure through water, food, or direct contact.

NPs like TiO₂ and ZnO exhibit pronounced toxicity in aquatic organisms. For instance, nanosized TiO₂ can adhere to the surface of aquatic invertebrates such as Daphnia magna, disrupting physiological processes like molting and leading to high mortality rates. This surface coating effect, combined with the persistent presence of NPs in water, can have widespread negative impacts on aquatic health and biodiversity. Similarly, ZnO NPs can undergo transformation in sewage treatment environments, forming new nanoparticle species (e.g., ZnS NPs) with altered stability and dissolution rates, potentially increasing their toxicity and persistence in aquatic ecosystems. Environmental factors such as pH, ionic strength, and the presence of other chemicals can alter the form, stability, and toxicity of NPs. These transformations may enhance their bioavailability and facilitate bioaccumulation in food webs, posing risks not only to aquatic organisms but also to higher trophic levels, including humans.

5.3.2 Ecological risks in one health ecosystems. The accumulation and persistence of NPs in the environment can degrade ecosystem services such as water quality, fisheries, and biodiversity. For example, NPs can disrupt the reproductive, developmental, and immune functions of aquatic species, leading to population declines and altered ecosystem dynamics. Further, NPs released into the environment can be transported across air, water, and soil, leading to exposure to animals and humans far from the original point of release. This mobility increases the risk of cross-species contamination and highlights the interconnectedness emphasized by the one health approach.

Despite increasing evidence of toxicity, there is still a lack of comprehensive data on the long-term fate, transport, and chronic effects of NPs in complex real-world ecosystems. Existing toxicity assessments often rely on short-term laboratory tests, which may not capture the full spectrum of ecological risks. While nanotechnologies offer innovative solutions for AMR, their deployment must be accompanied by rigorous assessment of toxicological and ecological risks. This includes understanding nanoparticle transformations, potential for bioaccumulation, and impacts on ecosystem health, as well as developing regulatory frameworks that reflect the interconnected realities of one health ecosystems.

5.4 Scalability and commercialization potential of nanotechnology-based approaches for AMR management

The scalability and commercialization potential of nanotechnology-based approaches for AMR management are promising yet complex, reflecting both remarkable advancements and persistent challenges. Nanomaterials such as metal and metal oxide NPs, liposomes, dendrimers, and polymeric carriers offer unique physicochemical properties that enable targeted antimicrobial delivery, enhanced efficacy, and the ability to bypass traditional resistance mechanisms. These attributes have attracted significant interest from both academic and industrial sectors toward developing nano-enabled therapeutics, diagnostics, and antimicrobial coatings for clinical, veterinary, and environmental applications. However, translating laboratory-scale innovations into commercially viable products requires overcoming several critical hurdles. First, the reproducible large-scale synthesis of nanomaterials with consistent quality and functionality remains a major bottleneck. Variability in nanoparticle size, shape, surface chemistry, and batch-to-batch consistency can impact both efficacy and safety, complicating industrial production and regulatory approval processes. Moreover, the cost-effectiveness of manufacturing and the scalability of green or sustainable synthesis methods such as plant-derived or biogenic NPs are under active investigation, as these approaches may reduce environmental impact and facilitate broader adoption.

Commercialization also hinges on robust toxicological and biocompatibility assessments, which are essential for gaining regulatory approval and market acceptance. Current regulatory frameworks for nanomedicines and nano-antimicrobials are still evolving, with a lack of harmonized guidelines across jurisdictions. This regulatory uncertainty can delay product development and increase commercialization risks. Additionally, concerns about long-term safety, environmental persistence, and potential ecological risks of NP release must be addressed through comprehensive risk assessments and lifecycle analyses. Despite these challenges, several nano-enabled antimicrobial products such as wound dressings, coatings for medical devices, and food packaging have reached the market, demonstrating the feasibility of commercial translation in specific sectors. Ongoing interdisciplinary collaboration among researchers, industry stakeholders, and policymakers is critical to optimize production processes, standardize safety evaluations, and establish clear regulatory pathways. With continued investment in scalable manufacturing technologies and regulatory science, nanotechnology-based solutions hold substantial potential to transform AMR management across the one health spectrum.

6. Summary and future prospects

The rise of AMR is a concerning trend that threatens to undermine the progress made by antimicrobial agents in the biomedical field. Among various strategies proposed to address this issue, research on nanotechnology-based approaches has shown significant advancement in recent decades. NPs have been shown to significantly enhance the efficacy of antimicrobial drugs by enabling controlled, sustained release and circumventing conventional resistance mechanisms. Through surface modification with functional groups and ligands, they can be engineered for increased specificity, minimizing the risk of side effects. Furthermore, many NPs possess intrinsic antimicrobial activity that is unaffected by traditional resistance mechanisms, broadening their therapeutic applications. Materials such as CS, PLGA, Au, and ZnO have demonstrated favorable biocompatibility through extensive studies and trials. In contrast, materials such as Cu and titanium oxide have exhibited potential cytotoxic effects, and some, including silicon and cadmium, require further evaluation due to insufficient data. Clinical adoption of nanoparticle-based therapeutics is already underway, with several PLGA NPs and liposome-based NPs receiving approval for specific clinical applications. Additionally, certain NPs, such as CS and iron oxide, have been successfully employed in other biomedical domains, including magnetic resonance imaging. The antimicrobial functionality and enhanced drug delivery capabilities make NPs a potent tool in combating the reappearing threat of microbial infections.

Increasing concerns regarding the cytotoxicity of NPs have prompted extensive research into strategies to mitigate associated risks. One prominent approach involves surface modification through the application of polymeric coatings. This significantly reduces the rate of ion release, allowing for less aggressive delivery. Several coating materials have demonstrated potential, particularly organic polymers such as CS, saccharides, and polyphenols.²⁸⁵ Among these, PEG has emerged as particularly effective, with numerous studies reporting its ability to significantly reduce protein adsorption on nanoparticle surfaces.²⁸⁶ As a result, PEGylated NPs are commonly employed in clinically approved drug formulations. Similarly, functionalization of nanoparticle surfaces with specific ligands can be performed to optimize interactions with the biological environment. This approach enhances delivery specificity and minimizes off-target interactions with non-targeted cells. Such modifications can significantly reduce cytotoxic effects on critical organs, including the lungs, liver, and kidneys.²⁸⁷ Another emerging strategy is green synthesis, which utilizes biological processes, such as those involving plant extracts, bacteria, or fungi, for nanoparticle production. NPs generated through this approach are typically surface-functionalized and exhibit high biocompatibility. However, a major limitation lies in the difficulty of obtaining homogeneous biological materials, which poses challenges in achieving reproducible and uniform nanoparticle synthesis.²⁸⁵

Although clinical trials involving NPs have begun to show promise, regulations governing their use in medicine remain inadequate. The US Food and Drug Administration, the European Medicines Agency, and other government organizations have introduced restrictions on research and trials related to NPs, but these regulations are limited to national contexts. There is currently no international consensus on what constitutes a nanomaterial-based drug, with most agencies operating with different definitions. Similarly, the criteria for manufacture, handling, biocompatibility and cytotoxicity remain undefined.²⁸⁸ This regulatory void hinders progress in the field, deterring investors and pharmaceutical companies from pursuing research in this area.¹³² Additionally, the lack of clarity slows the approval of nanoparticle-based drugs; since 2016, only 13 drugs have been approved by the FDA, most of which are liposomal formulations.²⁸⁹ This underscores the urgent need for international agreements and regulations concerning the study and clinical use of NPs, as without them, the field's growth will stagnate. Table 3 summarizes a selection of FDA-approved nanoparticle-based formulations currently used in clinical medicine, along with the developmental status of emerging nanoparticle therapeutics specifically targeting AMR. This includes liposomes, polymeric NPs, and metallic nanocarriers approved for drug delivery, cancer therapy, and infectious disease treatment. The table also outlines ongoing research and clinical trials exploring nanoparticle-enabled strategies to combat multidrug-resistant pathogens, showcasing their potential to overcome the limitations of conventional antibiotics through enhanced delivery, stability, and targeted action.

Table 3 Summary of various FDA-approved NPs for medical purposes, and the developmental status of nanoparticle drugs for AMR^290,291

Disease	FDA-approved nanoparticle materials
Acromegaly	Polymeric NPs (PEG)
Amyloidosis	Lipid NPs
Anemia	Polymeric NPs (PEG)
Arthritis	PLGA hydrogel, polymeric NPs (PEG)
Carcinoma	Metallic oxide NPs
Chronic kidney disease	Iron-based NPs
COVID-19	Liposomal NPs
Fungal infections	Liposomal NPs
Glioblastoma	Iron oxide NPs
Hemophilia	Polymeric NPs
Hepatitis	Polymeric NPs (PEG)
Leukemia	Liposomal NPs, polymeric NPs (PEG)
MAC lung disease	Liposomal NPs
Meningitis	Liposomal NPs
Multiple sclerosis	Polymeric NPs (PEG)
Opioid use disorder	PLGA NPs
Pancreatic cancer	Liposomal NPs
Prostate cancer	Polymeric NPs (PLGH)
Sarcoma	Liposomal NPs
Severe combined immunodeficiency disease	Polymeric NPs (PEG)
Shingles	Liposomal NPs

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Nanoparticle drugs for AMR (sourced from https://clinicaltrials.gov)
Nanoparticle drug	Developmental status
PLGA-hydrogel NPs for E. faecalis	Completed clinical trials
Ciprofloxacin-loaded PLGA-chitosan NPs for E. faecalis	Completed clinical trials
TiO2 NPs for C. albicans	Completed clinical trials
Miconazole-loaded CS NPs for C. albicans	Completed clinical trials
Ag NPs for antifungal activity	Clinical trials
ZnO for antifungal activity	Completed clinical trials

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A further challenge regarding the use of NPs in medicine is their mass production for commercial use. As previously mentioned, the conditions under which NPs are synthesized significantly influence their physicochemical characteristics, such as surface charge and size, which in turn affect their antimicrobial activity.²⁷⁷ Standardization of manufacturing processes is essential for the proper commercialization of nanoparticle-based drugs. Furthermore, before NPs can be integrated into clinical practice, their cytotoxicity must be thoroughly evaluated in vitro, particularly under varying environmental conditions. While several studies have reported the cytotoxicity of various NPs, especially metal ion NPs, a comprehensive understanding of the mechanisms of toxicity and the cytotoxic concentrations is needed. Additionally, the interactions of NPs with other antimicrobial agents, the potential effects of these interactions, and the consequences of nanoparticle biodegradation require further investigation.

Ongoing research is also exploring a range of nanoparticle-based technologies aimed at improving antimicrobial drug delivery. One such innovation involves the development of nanozymes, which are nanomaterials that mimic the structure and catalytic functions of natural enzymes.²⁹² Several natural enzymes, such as lysozymes, oxidases, and peroxidases, possess antimicrobial properties through catalyzing the hydrolysis of key structural and metabolic components of pathogenic cells. By replicating these enzymes, nanozymes have demonstrated promising antibacterial activity. In addition, nanozymes have enhanced stability and prolonged functionality under physiological conditions, giving an advantage over their natural counterparts.²⁹³ Another technology currently under investigation is the use of stimuli-responsive nanocarriers. These are engineered NPs designed to release the loaded molecule only in response to specific stimuli, allowing for site-specific and highly targeted drug delivery. A wide range of stimuli have been explored, including light, heat, magnetic fields, ultrasound, and the presence of ions. This approach not only minimizes off-target effects but also facilitates precise control over drug dosage and release kinetics.²⁹⁴ These technologies hold significant promise for advancing the clinical management of microbial infections through improved efficacy, specificity, and safety profiles. In conclusion, while nanotechnology offers promising solutions to combat AMR, the development of robust regulations, standardization of manufacturing processes, and comprehensive toxicity assessments are essential to ensure the safe and effective integration of NPs into clinical practice.

7. Conclusion

AMR stands as one of the most urgent global health challenges of the 21st century, threatening the efficacy of modern medicine and the sustainability of ecosystems. This review has highlighted the multifactorial nature of AMR, emphasizing the interconnectedness of human, animal, and environmental health, an approach central to the one health paradigm. By synthesizing current knowledge on the mechanisms of resistance, traditional and emerging therapeutic strategies, and the unique contributions of nanotechnology, this review underscores both the promise and complexity of tackling AMR in a holistic manner. Nanotechnology based interventions have emerged as a transformative frontier in the fight against drug-resistant pathogens. Diverse platforms ranging from CS and PLGA NPs to metallic NPs, dendrimers, and hydrogels demonstrate potent antimicrobial activity, often through mechanisms distinct from those of conventional antibiotics. These include membrane disruption, ROS generation, and targeted delivery, offering new hope for overcoming established resistance pathways and enhancing the efficacy of existing antimicrobials. However, the translation of nanotechnologies from bench to bedside and into broader one health applications is not without significant challenges. This review has critically examined the limitations associated with nanoparticle use, including cytotoxicity, the potential for nanoparticle-induced resistance, and the still-underexplored toxicological and ecological risks. The persistence and bioaccumulation of NPs in the environment, their effects on non-target organisms, and the long-term consequences for ecosystem health remain areas of active concern and ongoing research.

Furthermore, issues related to scalability, reproducibility, biocompatibility, and regulatory oversight present formidable barriers to clinical and field deployment. The absence of harmonized guidelines and robust long-term safety data underscores the need for interdisciplinary collaboration among scientists, clinicians, regulatory bodies, and policymakers. Looking forward, the integration of emerging nanotechnology platforms such as stimuli-responsive systems, hybrid nanosystems, and bioengineered nanozymes offers exciting avenues for innovation. Yet, their successful implementation will depend on addressing current knowledge gaps, particularly in clinical validation, environmental safety, and regulatory clarity. In conclusion, a one health nanotechnology approach provides a strategic and integrative framework for addressing AMR. By embracing the complexity of AMR transmission across human, animal, and environmental domains, and by fostering responsible innovation in nanotechnology, the global community can move closer to sustainable, effective solutions. Continued research, cross-sectoral collaboration, and proactive risk assessment will be essential to realize the full potential of nanotechnologies in safeguarding public health and ecosystem integrity against the escalating threat of AMR.

Conflicts of interest

The authors declare no competing financial interests or personal relationships that could have influenced the work presented in this manuscript.

Data availability

Data shall be made available upon genuine request to the authors.

Acknowledgements

AD thanks NIT Warangal and IITGN-SRIP for the Research Internship. SG thanks IITGN-MoE for the PhD fellowship. SS thanks IITGN startup grants. DB thanks SERB-DST, Gujcost, GSBTM, and STARS-MoES for research grants. AKY gratefully acknowledges the Indian Institute of Technology Gandhinagar (IITGN) for financial support through the Early Career Fellowship Award.

References

1. R. I. Aminov, A Brief History of the Antibiotic Era: Lessons Learned and Challenges for the Future, Front. Microbiol., 2010, 1, 134.
2. A. Tomasz, Antibiotic resistance in Streptococcus pneumoniae, Clin. Infect. Dis., 1997, 24(Suppl 1), S85–S88.
3. R. Ferrer, et al., Empiric Antibiotic Treatment Reduces Mortality in Severe Sepsis and Septic Shock From the First Hour: Results From a Guideline-Based Performance Improvement Program*, Crit. Care Med., 2014, 42, 1749.
4. V. X. Liu, et al., The Timing of Early Antibiotics and Hospital Mortality in Sepsis, Am. J. Respir. Crit. Care Med., 2017, 196, 856–863.
5. C. Classen David, et al., The Timing of Prophylactic Administration of Antibiotics and the Risk of Surgical-Wound Infection, N. Engl. J. Med., 1992, 326, 281–286.
6. J. Nemeth, G. Oesch and S. P. Kuster, Bacteriostatic versus bactericidal antibiotics for patients with serious bacterial infections: systematic review and meta-analysis, J. Antimicrob. Chemother., 2015, 70, 382–395.
7. S. Sinha, B. Medhi and R. Sehgal, Challenges of drug-resistant malaria, Parasite, 2014, 21, 61.
8. J. Acar and B. Rostel, Antimicrobial resistance: An overview, Rev. Sci. Tech. L’OIE, 2001, 20, 797–810.
9. M. Lipsitch, C. T. Bergstrom and B. R. Levin, The epidemiology of antibiotic resistance in hospitals: Paradoxes and prescriptions, Proc. Natl. Acad. Sci. U. S. A., 2000, 97, 1938–1943.
10. V. M. D’Costa, et al., Antibiotic resistance is ancient, Nature, 2011, 477, 457–461.
11. S. Z. Mindlin, V. S. Soina, M. A. Petrova and Zh. M. Gorlenko, Isolation of antibiotic resistance bacterial strains from Eastern Siberia permafrost sediments, Russ. J. Genet., 2008, 44, 27–34.
12. WHO publishes list of bacteria for which new antibiotics are urgently needed. https://www.who.int/news/item/27-02-2017-who-publishes-list-of-bacteria-for-which-new-antibiotics-are-urgently-needed.
13. A.-S. Balderrama-González, et al., Antimicrobial Resistance and Inorganic Nanoparticles, Int. J. Mol. Sci., 2021, 22, 12890.
14. J. A. Roberts, et al., DALI: Defining Antibiotic Levels in Intensive Care Unit Patients: Are Current β-Lactam Antibiotic Doses Sufficient for Critically Ill Patients?, Clin. Infect. Dis., 2014, 58, 1072–1083.
15. C.-E. Luyt, N. Bréchot, J.-L. Trouillet and J. Chastre, Antibiotic stewardship in the intensive care unit, Crit. Care, 2014, 18, 480.
16. B. J. Langford, et al., Bacterial co-infection and secondary infection in patients with COVID-19: a living rapid review and meta-analysis, Clin. Microbiol. Infect., 2020, 26, 1622–1629.
17. M. H. F. Sakeena, A. A. Bennett and A. J. McLachlan, Non-prescription sales of antimicrobial agents at community pharmacies in developing countries: a systematic review, Int. J. Antimicrob. Agents, 2018, 52, 771–782.
18. C. J. H. von Wintersdorff, et al., Dissemination of Antimicrobial Resistance in Microbial Ecosystems through Horizontal Gene Transfer, Front. Microbiol., 2016, 7, 173.
19. M. Nadimpalli, et al., Combating Global Antibiotic Resistance: Emerging One Health Concerns in Lower- and Middle-Income Countries, Clin. Infect. Dis., 2018, 66, 963–969.
20. B. M. Marshall and S. B. Levy, Food Animals and Antimicrobials: Impacts on Human Health, Clin. Microbiol. Rev., 2011, 24, 718–733.
21. J. G. Bartlett, D. N. Gilbert and B. Spellberg, Seven Ways to Preserve the Miracle of Antibiotics, Clin. Infect. Dis., 2013, 56, 1445–1450.
22. Antimicrobial resistance: global report on surveillance. https://www.who.int/publications/i/item/9789241564748.
23. Centers for Disease Control and Prevention (U.S.). Antibiotic Resistance Threats in the United States, 2019, 2019, https://stacks.cdc.gov/view/cdc/82532 DOI:10.15620/cdc:82532.
24. C. J. L. Murray, et al., Global burden of bacterial antimicrobial resistance in 2019: a systematic analysis, Lancet, 2022, 399, 629–655.
25. OECD. Embracing a One Health Framework to Fight Antimicrobial Resistance, (OECD, 2023) DOI:10.1787/ce44c755-en.
26. G. Kapoor, S. Saigal and A. Elongavan, Action and resistance mechanisms of antibiotics: A guide for clinicians, J. Anaesthesiol., Clin. Pharmacol., 2017, 33, 300.
27. H. I. Zgurskaya, C. A. Löpez and S. Gnanakaran, Permeability Barrier of Gram-negative Cell Envelopes and Approaches To Bypass It, ACS Infect. Dis., 2015, 1, 512–522.
28. M. Arzanlou, W. C. Chai and H. Venter, Intrinsic, adaptive and acquired antimicrobial resistance in Gram-negative bacteria, Essays Biochem., 2017, 61, 49–59.
29. L. B. Rice, Mechanisms of Resistance and Clinical Relevance of Resistance to β-Lactams, Glycopeptides, and Fluoroquinolones, Mayo Clin. Proc., 2012, 87, 198–208.
30. B. Li, Y. Qiu, Y. Song, H. Lin and H. Yin, Dissecting horizontal and vertical gene transfer of antibiotic resistance plasmid in bacterial community using microfluidics, Environ. Int., 2019, 131, 105007.
31. J. L. Martinez and F. Baquero, Mutation Frequencies and Antibiotic Resistance, Antimicrob. Agents Chemother., 2000, 44, 1771–1777.
32. L. S. Frost, R. Leplae, A. O. Summers and A. Toussaint, Mobile genetic elements: the agents of open source evolution, Nat. Rev. Microbiol., 2005, 3, 722–732.
33. C. Stevenson, J. P. J. Hall, E. Harrison, A. J. Wood and M. A. Brockhurst, Gene mobility promotes the spread of resistance in bacterial populations, ISME J., 2017, 11, 1930–1932.
34. F. Griffith, The Significance of Pneumococcal Types, Epidemiol. Infect., 1928, 27, 113–159.
35. C. M. Thomas and K. M. Nielsen, Mechanisms of, and Barriers to, Horizontal Gene Transfer between Bacteria, Nat. Rev. Microbiol., 2005, 3, 711–721.
36. H. Ochman, J. G. Lawrence and E. A. Groisman, Lateral gene transfer and the nature of bacterial innovation, Nature, 2000, 405, 299–304.
37. R. Mazaheri Nezhad Fard, M. D. Barton and M. W. Heuzenroeder, Bacteriophage-mediated transduction of antibiotic resistance in enterococci, Lett. Appl. Microbiol., 2011, 52, 559–564.
38. T. Billard-Pomares, et al., Characterization of a P1-Like Bacteriophage Carrying an SHV-2 Extended-Spectrum β-Lactamase from an Escherichia coli Strain, Antimicrob. Agents Chemother., 2014, 58, 6550–6557.
39. C. Smillie, M. P. Garcillán-Barcia, M. V. Francia, E. P. C. Rocha and F. de la Cruz, Mobility of Plasmids, Microbiol. Mol. Biol. Rev., 2010, 74, 434–452.
40. D. R. Evans, et al., Systematic detection of horizontal gene transfer across genera among multidrug-resistant bacteria in a single hospital, eLife, 2020, 9, e53886.
41. E. Dé, et al., A new mechanism of antibiotic resistance in Enterobacteriaceae induced by a structural modification of the major porin, Mol. Microbiol., 2001, 41, 189–198.
42. C.-L. Moo, et al., Mechanisms of Antimicrobial Resistance (AMR) and Alternative Approaches to Overcome AMR, Curr. Drug Discovery Technol., 2020, 17, 430–447.
43. C. W. Hall and T.-F. Mah, Molecular mechanisms of biofilm-based antibiotic resistance and tolerance in pathogenic bacteria, FEMS Microbiol. Rev., 2017, 41, 276–301.
44. J. M. Munita and C. A. Arias, Mechanisms of Antibiotic Resistance, Virulence Mechanisms of Bacterial Pathogens, 5th edn, 2016, pp. 481–511 DOI:10.1128/9781555819286.ch17.
45. G. D. Wright, Bacterial resistance to antibiotics: Enzymatic degradation and modification, Adv. Drug Delivery Rev., 2005, 57, 1451–1470.
46. E. A. Campbell, et al., Structural Mechanism for Rifampicin Inhibition of Bacterial RNA Polymerase, Cell, 2001, 104, 901–912.
47. R. Leclercq, Mechanisms of Resistance to Macrolides and Lincosamides: Nature of the Resistance Elements and Their Clinical Implications, Clin. Infect. Dis., 2002, 34, 482–492.
48. A. MacGowan and E. Macnaughton, Antibiotic resistance, Medicine, 2017, 45, 622–628.
49. D. G. J. Larsson and C.-F. Flach, Antibiotic resistance in the environment, Nat. Rev. Microbiol., 2022, 20, 257–269.
50. J. S. Mackenzie and M. Jeggo, The One Health Approach—Why Is It So Important?, Trop. Med. Infect. Dis., 2019, 4, 88.
51. T. U. Berendonk, et al., Tackling antibiotic resistance: the environmental framework, Nat. Rev. Microbiol., 2015, 13, 310–317.
52. The Manhattan Principles. https://oneworldonehealth.wcs.org/about-us/mission/the-manhattan-principles.aspx.
53. V. Rollet, Shaping European Union's global health initiatives. What role for the European Parliament?, J. Contemp. Eur. Stud., 2022, 30, 662–681.
54. T. R. Walsh, A one-health approach to antimicrobial resistance, Nat. Microbiol., 2018, 3, 854–855.
55. J. H. Powers, Antimicrobial drug development – the past, the present, and the future, Clin. Microbiol. Infect., 2004, 10, 23–31.
56. G. A. Durand, D. Raoult and G. Dubourg, Antibiotic discovery: history, methods and perspectives, Int. J. Antimicrob. Agents, 2019, 53, 371–382.
57. H. W. Boucher, et al., Bad Bugs, No Drugs: No ESKAPE! An Update from the Infectious Diseases Society of America, Clin. Infect. Dis., 2009, 48, 1–12.
58. X. Xu, et al., Synergistic combination of two antimicrobial agents closing each other's mutant selection windows to prevent antimicrobial resistance, Sci. Rep., 2018, 8, 7237.
59. C. A. Kerantzas and W. R. Jacobs, Origins of Combination Therapy for Tuberculosis: Lessons for Future Antimicrobial Development and Application, mBio, 2017, 8, e01586–16.
60. A. R. M. Coates, Y. Hu, J. Holt and P. Yeh, Antibiotic combination therapy against resistant bacterial infections: synergy, rejuvenation and resistance reduction, Expert Rev. Anti-Infect. Ther., 2020, 18, 5–15.
61. I. Kaur, Novel Strategies to Combat Antimicrobial Resistance, J. Infect. Dis. Ther., 2016, 4, 1.
62. M. Paul, Y. Dickstein, A. Schlesinger, S. G. Glasberg, K. S. Weiser and L. Leibovici, Beta-lactam versus beta-lactam-aminoglycoside combination therapy in cancer patients with neutropenia, Cochrane Database Syst. Rev., 2013,(6), 1465–1858.
63. F. D’Herelle, An invisible microbe antagonistic toward dysenteric bacilli, C. R. Acad. Sci., 1917, 165, 373–375.
64. E. C. Keen, Phage Therapy: Concept to Cure, Front. Microbiol., 2012, 3, 238.
65. S. J. Labrie, J. E. Samson and S. Moineau, Bacteriophage resistance mechanisms, Nat. Rev. Microbiol., 2010, 8, 317–327.
66. Q. Yang, S. Le, T. Zhu and N. Wu, Regulations of phage therapy across the world, Front. Microbiol., 2023, 14, 1250848.
67. Y. Liu, R. Li, X. Xiao and Z. Wang, Antibiotic adjuvants: an alternative approach to overcome multi-drug resistant Gram-negative bacteria, Crit. Rev. Microbiol., 2019, 45, 301–314.
68. L. Kalan and G. D. Wright, Antibiotic adjuvants: multicomponent anti-infective strategies, Expert Rev. Mol. Med., 2011, 13, e5.
69. T. Shakya, et al., A small molecule discrimination map of the antibiotic resistance kinome, Chem. Biol., 2011, 18, 1591–1601.
70. I. Kolodkin-Gal, et al., d-Amino Acids Trigger Biofilm Disassembly, Science, 2010, 328, 627–629.
71. R. J. Melander and C. Melander, The Challenge of Overcoming Antibiotic Resistance: An Adjuvant Approach?, ACS Infect. Dis., 2017, 3, 559–563.
72. M. Mahlapuu, C. Björn and J. Ekblom, Antimicrobial peptides as therapeutic agents: opportunities and challenges, Crit. Rev. Biotechnol., 2020, 40, 978–992.
73. R. J. Dubos, STUDIES ON A BACTERICIDAL AGENT EXTRACTED FROM A SOIL BACILLUS, J. Exp. Med., 1939, 70, 11–17.
74. N. Mookherjee, M. A. Anderson, H. P. Haagsman and D. J. Davidson, Antimicrobial host defence peptides: functions and clinical potential, Nat. Rev. Drug Discovery, 2020, 19, 311–332.
75. H. Jenssen, P. Hamill and R. E. W. Hancock, Peptide Antimicrobial Agents, Clin. Microbiol. Rev., 2006, 19, 491–511.
76. K. A. Brogden, Antimicrobial peptides: pore formers or metabolic inhibitors in bacteria?, Nat. Rev. Microbiol., 2005, 3, 238–250.
77. G. S. Tjabringa, D. K. Ninaber, J. W. Drijfhout, K. F. Rabe and P. S. Hiemstra, Human cathelicidin LL-37 is a chemoattractant for eosinophils and neutrophils that acts via formyl-peptide receptors, Int. Arch. Allergy Immunol., 2006, 140, 103–112.
78. Y. Zheng, et al., Cathelicidin LL-37 induces the generation of reactive oxygen species and release of human alpha-defensins from neutrophils, Br. J. Dermatol., 2007, 157, 1124–1131.
79. M. Malerba, et al., Epidermal hepcidin is required for neutrophil response to bacterial infection, J. Clin. Invest., 2020, 130, 329–334.
80. K. C. Wuerth, R. Falsafi and R. E. W. Hancock, Synthetic host defense peptide IDR-1002 reduces inflammation in Pseudomonas aeruginosa lung infection, PLoS One, 2017, 12, e0187565.
81. E. J. A. Veldhuizen, E. C. Brouwer, V. A. F. Schneider and A. C. Fluit, Chicken Cathelicidins Display Antimicrobial Activity against Multiresistant Bacteria without Inducing Strong Resistance, PLoS One, 2013, 8, e61964.
82. A. Lewies, L. H. Du Plessis and J. F. Wentzel, Antimicrobial Peptides: the Achilles’ Heel of Antibiotic Resistance?, Probiotics Antimicrob. Proteins, 2019, 11, 370–381.
83. C. H. Chen and T. K. Lu, Development and Challenges of Antimicrobial Peptides for Therapeutic Applications, Antibiotics, 2020, 9, 24.
84. H. Alaoui Mdarhri, et al., Alternatives Therapeutic Approaches to Conventional Antibiotics: Advantages, Limitations and Potential Application in Medicine, Antibiotics, 2022, 11, 1826.
85. B. Mishra, S. Reiling, D. Zarena and G. Wang, Host defense antimicrobial peptides as antibiotics: design and application strategies, Curr. Opin. Chem. Biol., 2017, 38, 87–96.
86. N. Chanishvili, Phage Therapy—History from Twort and d’Herelle Through Soviet Experience to Current Approaches, in Advances in Virus Research, ed. M. Łobocka and W. Szybalski, Academic Press, 2012, ch. 1, vol. 83, pp. 3–40.
87. L. Fan, et al., The Antimicrobial Activity and Resistance Evolution of Nanomaterials: A Review, ACS Mater. Lett., 2025, 7, 1085–1111.
88. A New Era of Antibiotics: The Clinical Potential of Antimicrobial Peptides. https://www.mdpi.com/1422-0067/21/19/7047.
89. A. Darbandi, et al., Antibody–Antibiotic Conjugates: A Comprehensive Review on Their Therapeutic Potentials Against BacterialInfections, J. Clin. Lab. Anal., 2024, 38, e25071.
90. Q. Chen, Development of plant-made monoclonal antibodies against viral infections, Curr. Opin. Virol., 2022, 52, 148–160.
91. R. T. Schooley, et al., Development and Use of Personalized Bacteriophage-Based Therapeutic Cocktails To Treat a Patient with a Disseminated Resistant Acinetobacter baumannii Infection, Antimicrob. Agents Chemother., 2017, 61(10), e00954–17.
92. H. Tahmasebi, et al., From Cure to Crisis: Understanding the Evolution of Antibiotic-Resistant Bacteria in Human Microbiota, Biomolecules, 2025, 15, 93.
93. About Nanotechnology | National Nanotechnology Initiative. https://www.nano.gov/about-nanotechnology.
94. Molecularly imprinted polymer-based nanodiagnostics for clinically pertinent bacteria and virus detection for future pandemics – ScienceDirect. https://www.sciencedirect.com/science/article/pii/S2590137022001509?via%3Dihub.
95. D. Chauhan, A. K. Yadav, D. Bhatia and P. R. Solanki, Global impact of vitamin D deficiency and innovative biosensing technologies, Chem. Eng. J., 2025, 506, 159790.
96. D. Verma, A. K. Yadav, K. K. Gupta and P. R. Solanki, Sustainable synthesis of a PtNPs@rGO nanohybrid for detection of toxic fluoride ions using hand-made screen-printed electrodes in aqueous medium, J. Mater. Chem. B, 2025, 13, 5070–5084.
97. J. S. Kim, et al., Antimicrobial effects of silver nanoparticles, Nanomedicine, 2007, 3, 95–101.
98. D. L. Slomberg, et al., Role of Size and Shape on Biofilm Eradication for Nitric Oxide-Releasing Silica Nanoparticles, ACS Appl. Mater. Interfaces, 2013, 5, 9322–9329.
99. R. Y. Pelgrift and A. J. Friedman, Nanotechnology as a therapeutic tool to combat microbial resistance, Adv. Drug Delivery Rev., 2013, 65, 1803–1815.
100. L. Wang, C. Hu and L. Shao, The antimicrobial activity of nanoparticles: present situation and prospects for the future, Int. J. Nanomed., 2017, 12, 1227–1249.
101. A. M. Allahverdiyev, K. V. Kon, E. S. Abamor, M. Bagirova and M. Rafailovich, Coping with antibiotic resistance: combining nanoparticles with antibiotics and other antimicrobial agents, Expert Rev. Anti-Infect. Ther., 2011, 9, 1035–1052.
102. A. J. Friedman, et al., Antimicrobial and Anti-Inflammatory Activity of Chitosan–Alginate Nanoparticles: A Targeted Therapy for Cutaneous Pathogens, J. Invest. Dermatol., 2013, 133, 1231–1239.
103. I. M. Helander, E.-L. Nurmiaho-Lassila, R. Ahvenainen, J. Rhoades and S. Roller, Chitosan disrupts the barrier properties of the outer membrane of Gram-negative bacteria, Int. J. Food Microbiol., 2001, 71, 235–244.
104. E. I. Rabea, M. E.-T. Badawy, C. V. Stevens, G. Smagghe and W. Steurbaut, Chitosan as Antimicrobial Agent: Applications and Mode of Action, Biomacromolecules, 2003, 4, 1457–1465.
105. Y. Ma, T. Zhou and C. Zhao, Preparation of chitosan–nylon-6 blended membranes containing silver ions as antibacterial materials, Carbohydr. Res., 2008, 343, 230–237.
106. A. K. Yadav, T. K. Dhiman, G. B. V. S. Lakshmi, A. N. Berlina and P. R. Solanki, A highly sensitive label-free amperometric biosensor for norfloxacin detection based on chitosan-yttria nanocomposite, Int. J. Biol. Macromol., 2020, 151, 566–575.
107. L. Qi, Z. Xu, X. Jiang, C. Hu and X. Zou, Preparation and antibacterial activity of chitosan nanoparticles, Carbohydr. Res., 2004, 339, 2693–2700.
108. A. Kumari, S. K. Yadav and S. C. Yadav, Biodegradable polymeric nanoparticles based drug delivery systems, Colloids Surf., B, 2010, 75, 1–18.
109. H. Ibrahim, M. El-Bisi, G. Taha and E. El-Alfy, Chitosan nanoparticles loaded antibiotics as drug delivery biomaterial, J. Appl. Pharm. Sci., 2015, 085–090,  DOI:10.7324/JAPS.2015.501015.
110. Z. Sobhani, S. Mohammadi Samani, H. Montaseri and E. Khezri, Nanoparticles of Chitosan Loaded Ciprofloxacin: Fabrication and Antimicrobial Activity, Adv. Pharm. Bull., 2017, 7, 427–432.
111. B. Fayed, et al., Co-administration of amoxicillin-loaded chitosan nanoparticles and inulin: A novel strategy for mitigating antibiotic resistance and preserving microbiota balance in Helicobacter pylori treatment, Int. J. Biol. Macromol., 2023, 253, 126706.
112. M. Eskandari, Z. Abdolmaleki, F. Moosakhani and M. A. Eslampour, Antimicrobial Efficacy of Cloxacillin-Loaded Chitosan Nanoparticles Against Staphylococcus aureus Biofilms in Subclinical Mastitis, Curr. Microbiol., 2025, 82, 65.
113. P. Wang, et al., Antimicrobial and anti-biofilm effects of dihydroartemisinin-loaded chitosan nanoparticles against methicillin-resistant Staphylococcus aureus, Microb. Pathog., 2025, 199, 107208.
114. V. N. Nguyen, et al., Enhancing the antibacterial activity of ampicillin loaded into chitosan/starch nanocomposites against AMR Staphylococcus aureus, Carbohydr. Res., 2024, 545, 109274.
115. K. Blecher, A. Nasir and A. Friedman, The growing role of nanotechnology in combating infectious disease, Virulence, 2011, 2, 395–401.
116. P. Fan, et al., A novel combination therapy for multidrug resistant pathogens using chitosan nanoparticles loaded with β-lactam antibiotics and β-lactamase inhibitors, Int. J. Biol. Macromol., 2022, 195, 506–514.
117. N. Morin-Crini, E. Lichtfouse, G. Torri and G. Crini, Applications of chitosan in food, pharmaceuticals, medicine, cosmetics, agriculture, textiles, pulp and paper, biotechnology, and environmental chemistry, Environ. Chem. Lett., 2019, 17, 1667–1692.
118. F. Danhier, et al., PLGA-based nanoparticles: An overview of biomedical applications, J. Controlled Release, 2012, 161, 505–522.
119. P. Sabaeifard, A. Abdi-Ali, M. R. Soudi, C. Gamazo and J. M. Irache, Amikacin loaded PLGA nanoparticles against Pseudomonas aeruginosa, Eur. J. Pharm. Sci., 2016, 93, 392–398.
120. Y. Abo-zeid, A. Amer, M. R. Bakkar, B. El-Houssieny and W. Sakran, Antimicrobial Activity of Azithromycin Encapsulated into PLGA NPs: A Potential Strategy to Overcome Efflux Resistance, Antibiotics, 2022, 11, 1623.
121. A. A. Alsa’d, et al., Optimising intracellular delivery of antibiotic loaded PLGA nanoparticles to macrophages, Int. J. Pharm., 2024, 664, 124567.
122. C. Lecaroz, C. Gamazo and M. J. Blanco-Prieto, Nanocarriers with Gentamicin to Treat Intracellular Pathogens, J. Nanosci. Nanotechnol., 2006, 6, 3296–3302.
123. L. Jiang, et al., Clearance of intracellular Klebsiella pneumoniae infection using gentamicin-loaded nanoparticles, J. Controlled Release, 2018, 279, 316–325.
124. N. Watcharadulyarat, M. Rattanatayarom, N. Ruangsawasdi and N. Patikarnmonthon, PEG–PLGA nanoparticles for encapsulating ciprofloxacin, Sci. Rep., 2023, 13, 266.
125. J. Trousil, et al., System with embedded drug release and nanoparticle degradation sensor showing efficient rifampicin delivery into macrophages, Nanomedicine, 2017, 13, 307–315.
126. U. S. Toti, et al., Targeted delivery of antibiotics to intracellular chlamydial infections using PLGA nanoparticles, Biomaterials, 2011, 32, 6606–6613.
127. Y. Abo-zeid, A. Amer, M. R. Bakkar, B. El-Houssieny and W. Sakran, Antimicrobial Activity of Azithromycin Encapsulated into PLGA NPs: A Potential Strategy to Overcome Efflux Resistance, Antibiotics, 2022, 11, 1623.
128. A. Baelo, et al., Disassembling bacterial extracellular matrix with DNase-coated nanoparticles to enhance antibiotic delivery in biofilm infections, J. Controlled Release, 2015, 209, 150–158.
129. N. Forna, et al., Nano-Architectonics of Antibiotic-Loaded Polymer Particles as Vehicles for Active Molecules, Appl. Sci., 2022, 12, 1998.
130. A. K. Shakya, et al., Review on PLGA Polymer Based Nanoparticles with Antimicrobial Properties and Their Application in Various Medical Conditions or Infections, Polymers, 2023, 15, 3597.
131. A. Shariati, Z. Chegini, E. Ghaznavi-Rad, E. N. Zare and S. M. Hosseini, PLGA-Based Nanoplatforms in Drug Delivery for Inhibition and Destruction of Microbial Biofilm, Front. Cell. Infect. Microbiol., 2022, 12, 926363.
132. A. T. Yayehrad, G. B. Wondie and T. Marew, Different Nanotechnology Approaches for Ciprofloxacin Delivery Against Multidrug-Resistant Microbes, Infect. Drug Resist., 2022, 15, 413–426.
133. Z. Drulis-Kawa and A. Dorotkiewicz-Jach, Liposomes as delivery systems for antibiotics, Int. J. Pharm., 2010, 387, 187–198.
134. R. Ghosh and M. De, Liposome-Based Antibacterial Delivery: An Emergent Approach to Combat Bacterial Infections, ACS Omega, 2023, 8, 35442–35451.
135. E. Natsaridis, et al., Cholesterol-Rich Antibiotic-Loaded Liposomes as Efficient Antimicrobial Therapeutics, Int. J. Nanomed., 2025, 20, 4943–4965.
136. N. E. Eleraky, A. Allam, S. B. Hassan and M. M. Omar, Nanomedicine Fight against Antibacterial Resistance: An Overview of the Recent Pharmaceutical Innovations, Pharmaceutics, 2020, 12, 142.
137. M. Magallanes, J. Dijkstra and J. Fierer, Liposome-incorporated ciprofloxacin in treatment of murine salmonellosis, Antimicrob. Agents Chemother., 1993, 37, 2293–2297.
138. C. Beaulac, S. Sachetelli and J. Lagace, In-vitro bactericidal efficacy of sub-MIC concentrations of liposome-encapsulated antibiotic against Gram-negative and Gram-positive bacteria, J. Antimicrob. Chemother., 1998, 41, 35–41.
139. N. M. Alzahrani, et al., Liposome-Encapsulated Tobramycin and IDR-1018 Peptide Mediated Biofilm Disruption and Enhanced Antimicrobial Activity against Pseudomonas aeruginosa, Pharmaceutics, 2022, 14, 960.
140. P. M. Furneri, M. Fresta, G. Puglisi and G. Tempera, Ofloxacin-Loaded Liposomes: In Vitro Activity and Drug Accumulation in Bacteria, Antimicrob. Agents Chemother., 2000, 44, 2458–2464.
141. M. Alipour, M. Halwani, A. Omri and Z. E. Suntres, Antimicrobial effectiveness of liposomal polymyxin B against resistant Gram-negative bacterial strains, Int. J. Pharm., 2008, 355, 293–298.
142. C. Mugabe, M. Halwani, A. O. Azghani, R. M. Lafrenie and A. Omri, Mechanism of Enhanced Activity of Liposome-Entrapped Aminoglycosides against Resistant Strains of Pseudomonas aeruginosa, Antimicrob. Agents Chemother., 2006, 50, 2016–2022.
143. J. O. Pinho, et al., Liposomal Rifabutin—A Promising Antibiotic Repurposing Strategy against Methicillin-Resistant Staphylococcus aureus Infections, Pharmaceuticals, 2024, 17, 470.
144. K. Manjunath, J. S. Reddy and V. Venkateswarlu, Solid lipid nanoparticles as drug delivery systems, Methods Find. Exp. Clin. Pharmacol., 2005, 27, 127.
145. O. A. Madkhali, Perspectives and Prospective on Solid Lipid Nanoparticles as Drug Delivery Systems, Molecules, 2022, 27, 1543.
146. A. zur Mühlen, C. Schwarz and W. Mehnert, Solid lipid nanoparticles (SLN) for controlled drug delivery – Drug release and release mechanism, Eur. J. Pharm. Biopharm., 1998, 45, 149–155.
147. R. Pignatello, et al., A Method for Efficient Loading of Ciprofloxacin Hydrochloride in Cationic Solid Lipid Nanoparticles: Formulation and Microbiological Evaluation, Nanomaterials, 2018, 8, 304.
148. S. Ghaffari, et al., Ciprofloxacin Loaded Alginate/Chitosan and Solid Lipid Nanoparticles, Preparation, and Characterization, J. Dispersion Sci. Technol., 2012, 33, 685–689.
149. M. Taheri, et al., Antibiotics-encapsulated nanoparticles as an antimicrobial agent in the treatment of wound infection, Front. Immunol., 2024, 15, 1435151.
150. L. Arana, L. Gallego and I. Alkorta, Incorporation of Antibiotics into Solid Lipid Nanoparticles: A Promising Approach to Reduce Antibiotic Resistance Emergence, Nanomaterials, 2021, 11, 1251.
151. S. Mukherjee, S. Ray and R. S. Thakur, Solid Lipid Nanoparticles: A Modern Formulation Approach in Drug Delivery System, Indian J. Pharm. Sci., 2009, 71, 349–358.
152. V. R. Salvi and P. Pawar, Nanostructured lipid carriers (NLC) system: A novel drug targeting carrier, J. Drug Delivery Sci. Technol., 2019, 51, 255–267.
153. A. K. Yadav, D. Verma, G. B. V. S. Lakshmi, S. Eremin and P. R. Solanki, Fabrication of label-free and ultrasensitive electrochemical immunosensor based on molybdenum disulfide nanoparticles modified disposable ITO: An analytical platform for antibiotic detection in food samples, Food Chem., 2021, 363, 130245.
154. A. K. Yadav, D. Verma and P. R. Solanki, Electrophoretically deposited L-cysteine functionalized MoS2@MWCNT nanocomposite platform: a smart approach toward highly sensitive and label-free detection of gentamicin, Mater. Today Chem., 2021, 22, 100567.
155. Q. Ye, et al., Iron and zinc ions, potent weapons against multidrug-resistant bacteria, Appl. Microbiol. Biotechnol., 2020, 104, 5213–5227.
156. M. Mühling, A. Bradford, J. W. Readman, P. J. Somerfield and R. D. Handy, An investigation into the effects of silver nanoparticles on antibiotic resistance of naturally occurring bacteria in an estuarine sediment, Mar. Environ. Res., 2009, 68, 278–283.
157. I. Chopra, The increasing use of silver-based products as antimicrobial agents: a useful development or a cause for concern?, J. Antimicrob. Chemother., 2007, 59, 587–590.
158. R. Souza, L. Haberbeck, H. Riella, D. Ribeiro and B. Carciofi, Antibacterial Activity of Zinc Oxide Nanoparticles Synthesized by Solochemical Process, Braz. J. Chem. Eng., 2019, 36, 885–893.
159. R. Krishnamoorthy, et al., Antibacterial Mechanisms of Zinc Oxide Nanoparticle against Bacterial Food Pathogens Resistant to Beta-Lactam Antibiotics, Molecules, 2022, 27, 2489.
160. A. A. Tayel, et al., Antibacterial Action of Zinc Oxide Nanoparticles Against Foodborne Pathogens, J. Food Saf., 2011, 31, 211–218.
161. A. Jesline, N. P. John, P. M. Narayanan, C. Vani and S. Murugan, Antimicrobial activity of zinc and titanium dioxide nanoparticles against biofilm-producing methicillin-resistant Staphylococcus aureus, Appl. Nanosci., 2015, 5, 157–162.
162. A. Abdelghafar, N. Yousef and M. Askoura, Zinc oxide nanoparticles reduce biofilm formation, synergize antibiotics action and attenuate Staphylococcus aureus virulence in host; an important message to clinicians, BMC Microbiol., 2022, 22, 244.
163. V. Thati, A. S. Roy, M. V. N. A. Prasad, C. T. Shivannavar and S. M. Gaddad, Nanostructured zinc oxide enhances the activity of antibiotics against Staphylococcus aureus, J. Biosci. Technol., 2010, 1, 64.
164. M. Banoee, et al., ZnO nanoparticles enhanced antibacterial activity of ciprofloxacin against Staphylococcus aureus and Escherichia coli, J. Biomed. Mater. Res., Part B, 2010, 93B, 557–561.
165. F. Ghasemi and R. Jalal, Antimicrobial action of zinc oxide nanoparticles in combination with ciprofloxacin and ceftazidime against multidrug-resistant Acinetobacter baumannii, J. Global Antimicrob. Resist., 2016, 6, 118–122.
166. B. Shokrollahi, A. Tabatabaee and T. Saleh, Effect of Zinc Oxide Nanoparticles on Loaded Antibiotics Against Multidrug-Resistant Acinetobacter spp, Avicenna J. Clin. Microbiol. Infect., 2021, 8, 51–56.
167. B. Lallo da Silva, et al., Relationship Between Structure And Antimicrobial Activity Of Zinc Oxide Nanoparticles: An Overview, Int. J. Nanomed., 2019, 14, 9395–9410.
168. M. El-Telbany, et al., Combination of Meropenem and Zinc Oxide Nanoparticles; Antimicrobial Synergism, Exaggerated Antibiofilm Activity, and Efficient Therapeutic Strategy against Bacterial Keratitis, Antibiotics, 2022, 11, 1374.
169. A. D. Russell and W. B. Hugo, 7 Antimicrobial Activity and Action of Silver, in Progress in Medicinal Chemistry, ed. G. P. Ellis and D. K. Luscombe, Elsevier, 1994, vol. 31, pp. 351–370.
170. S. Prabhu and E. K. Poulose, Silver nanoparticles: mechanism of antimicrobial action, synthesis, medical applications, and toxicity effects, Int. Nano Lett., 2012, 2, 32.
171. I. Sondi and B. Salopek-Sondi, Silver nanoparticles as antimicrobial agent: a case study on E. coli as a model for Gram-negative bacteria, J. Colloid Interface Sci., 2004, 275, 177–182.
172. I. X. Yin, et al., The Antibacterial Mechanism of Silver Nanoparticles and Its Application in Dentistry, Int. J. Nanomed., 2020, 15, 2555–2562.
173. M. Alavi and M. R. Hamblin, Antibacterial silver nanoparticles: effects on bacterial nucleic acids, Cell. Mol. Biomed. Rep., 2023, 3, 35–40.
174. A. Nanda and M. Saravanan, Biosynthesis of silver nanoparticles from Staphylococcus aureus and its antimicrobial activity against MRSA and MRSE, Nanomedicine, 2009, 5, 452–456.
175. M. A. A. Masimen, N. A. Harun, M. Maulidiani and W. I. W. Ismail, Overcoming Methicillin-Resistance Staphylococcus aureus (MRSA) Using Antimicrobial Peptides-Silver Nanoparticles, Antibiotics, 2022, 11, 951.
176. P. Li, J. Li, C. Wu, Q. Wu and J. Li, Synergistic antibacterial effects of β-lactam antibiotic combined with silver nanoparticles, Nanotechnology, 2005, 16, 1912.
177. M. Zavarshani, M. Ahmadi, H. Dastmalchi Saei, A. A. Tehrani and B. Dalir Naghadeh, Comparison Therapeutic Effects of Ciprofloxacin, Silver Nanoparticles and Their Combination in the Treatment of Pseudomonas keratitis in Rabbit: An Experimental Study, Iran. J. Pharm. Res., 2019, 18, 320–327.
178. D. R. Ibraheem, et al., Ciprofloxacin-Loaded Silver Nanoparticles as Potent Nano-Antibiotics against Resistant Pathogenic Bacteria, Nanomaterials, 2022, 12, 2808.
179. A. R. Shahverdi, A. Fakhimi, H. R. Shahverdi and S. Minaian, Synthesis and effect of silver nanoparticles on the antibacterial activity of different antibiotics against Staphylococcus aureus and Escherichia coli, Nanomedicine, 2007, 3, 168–171.
180. A. S. Dove, et al., Silver nanoparticles enhance the efficacy of aminoglycosides against antibiotic-resistant bacteria, Front. Microbiol., 2023, 13, 1064095.
181. Engineered Graphene Oxide Nanocomposite Capable of Preventing the Evolution of Antimicrobial Resistance | ACS Nano, https://pubs.acs.org/doi/10.1021/acsnano.9b04970.
182. M. C. Crisan, M. Teodora and M. Lucian, Copper Nanoparticles: Synthesis and Characterization, Physiology, Toxicity and Antimicrobial Applications, Appl. Sci., 2022, 12, 141.
183. M. Raffi, et al., Investigations into the antibacterial behavior of copper nanoparticles against Escherichia coli, Ann. Microbiol., 2010, 60, 75–80.
184. A. K. Chatterjee, R. Chakraborty and T. Basu, Mechanism of antibacterial activity of copper nanoparticles, Nanotechnology, 2014, 25, 135101.
185. W. B. Wang and J. C. Clapper, Antibacterial Activity of Electrospun Polyacrylonitrile Copper Nanoparticle Nanofibers on Antibiotic Resistant Pathogens and Methicillin Resistant Staphylococcus aureus (MRSA), Nanomaterials, 2022, 12, 2139.
186. A. M. Shehabeldine, et al., Potential Antimicrobial and Antibiofilm Properties of Copper Oxide Nanoparticles: Time-Kill Kinetic Essay and Ultrastructure of Pathogenic Bacterial Cells, Appl. Biochem. Biotechnol., 2023, 195, 467–485.
187. K. Mandava, et al., Green Synthesis of Stable Copper Nanoparticles and Synergistic Activity with Antibiotics, Indian J. Pharm. Sci., 2017, 79, 695–700.
188. G. Vasiliev, et al., Synergistic antibacterial effect of copper and silver nanoparticles and their mechanism of action, Sci. Rep., 2023, 13, 9202.
189. Z. Chen, et al., Acute toxicological effects of copper nanoparticles in vivo, Toxicol. Lett., 2006, 163, 109–120.
190. I. Gosens, et al., Organ burden and pulmonary toxicity of nano-sized copper (II) oxide particles after short-term inhalation exposure, Nanotoxicology, 2016, 10, 1084–1095.
191. Y. Cui, et al., The molecular mechanism of action of bactericidal gold nanoparticles on Escherichia coli, Biomaterials, 2012, 33, 2327–2333.
192. S. Shamaila, et al., Gold Nanoparticles: An Efficient Antimicrobial Agent against Enteric Bacterial Human Pathogen, Nanomaterials, 2016, 6, 71.
193. B. Saha, et al., In Vitro Structural and Functional Evaluation of Gold Nanoparticles Conjugated Antibiotics, Nanoscale Res. Lett., 2007, 2, 614.
194. A. N. Brown, et al., Nanoparticles Functionalized with Ampicillin Destroy Multiple-Antibiotic-Resistant Isolates of Pseudomonas aeruginosa and Enterobacter aerogenes and Methicillin-Resistant Staphylococcus aureus, Appl. Environ. Microbiol., 2012, 78, 2768–2774.
195. A. S. Abu Lila, et al., Delafloxacin-Capped Gold Nanoparticles (DFX-AuNPs): An Effective Antibacterial Nano-Formulation of Fluoroquinolone Antibiotic, Materials, 2022, 15, 5709.
196. T. A. Hagbani, et al., Enhancement of Vancomycin Potential against Pathogenic Bacterial Strains via Gold Nano-Formulations: A Nano-Antibiotic Approach, Materials, 2022, 15, 1108.
197. F. Khan, N. Tabassum, G.-J. Jeong, W.-K. Jung and Y.-M. Kim, Inhibition of Mixed Biofilms of Candida albicans and Staphylococcus aureus by β-Caryophyllene-Gold Nanoparticles, Antibiotics, 2023, 12, 726.
198. F. Khan, et al., Synthesis and characterization of chitosan oligosaccharide-capped gold nanoparticles as an effective antibiofilm drug against the Pseudomonas aeruginosa PAO1, Microb. Pathog., 2019, 135, 103623.
199. A. A. Vodyashkin, M. G. H. Rizk, P. Kezimana, A. A. Kirichuk and Y. M. Stanishevskiy, Application of Gold Nanoparticle-Based Materials in Cancer Therapy and Diagnostics, ChemEngineering, 2021, 5, 69.
200. H. A. Foster, I. B. Ditta, S. Varghese and A. Steele, Photocatalytic disinfection using titanium dioxide: spectrum and mechanism of antimicrobial activity, Appl. Microbiol. Biotechnol., 2011, 90, 1847–1868.
201. A. A. Menazea and N. S. Awwad, Antibacterial activity of TiO2 doped ZnO composite synthesized via laser ablation route for antimicrobial application, J. Mater. Res. Technol., 2020, 9, 9434–9441.
202. A. S. Roy, A. Parveen, A. R. Koppalkar and M. V. N. A. Prasad, Effect of Nano – Titanium Dioxide with Different Antibiotics against Methicillin-Resistant Staphylococcus Aureus, J. Biomater. Nanobiotechnol., 2010, 01, 37–41.
203. IARC Working Group on the Evaluation of Carcinogenic Risks to Humans, Carbon black, titanium dioxide, and talc, IARC Monogr. Eval. Carcinog. Risks Hum., 2010, 93, 1–413 , https://pubmed.ncbi.nlm.nih.gov/21449489/.
204. M. E. El Zowalaty, et al., The ability of streptomycin-loaded chitosan-coated magnetic nanocomposites to possess antimicrobial and antituberculosis activities, Int. J. Nanomed., 2015, 10, 3269–3274.
205. D. Touati, Iron and Oxidative Stress in Bacteria, Arch. Biochem. Biophys., 2000, 373, 1–6.
206. N. Madubuonu, et al., Biosynthesis of iron oxide nanoparticles via a composite of Psidium guavaja-Moringa oleifera and their antibacterial and photocatalytic study, J. Photochem. Photobiol., B, 2019, 199, 111601.
207. P. Velusamy, et al., Surface engineered iron oxide nanoparticles as efficient materials for antibiofilm application, Biotechnol. Appl. Biochem., 2022, 69, 714–725.
208. A. M. Davarpanah, A. Rahdar, M. A. Dastnae, O. Zeybek and H. Beyzaei, (1-x)BaFe12O19/ xCoFe2O4 hard/soft magnetic nanocomposites: Synthesis, physical characterization, and antibacterial activities study, J. Mol. Struct., 2019, 1175, 445–449.
209. M. M. Hassan, A. Ranzoni, W. Phetsang, M. A. T. Blaskovich and M. A. Cooper, Surface Ligand Density of Antibiotic-Nanoparticle Conjugates Enhances Target Avidity and Membrane Permeabilization of Vancomycin-Resistant Bacteria, Bioconjugate Chem., 2017, 28, 353–361.
210. M. Mahmoudi, et al., Multiphysics Flow Modeling and in Vitro Toxicity of Iron Oxide Nanoparticles Coated with Poly(vinyl alcohol), J. Phys. Chem. C, 2009, 113, 2322–2331.
211. Y. Huang, J. C. Hsu, H. Koo and D. P. Cormode, Repurposing ferumoxytol: Diagnostic and therapeutic applications of an FDA-approved nanoparticle, Theranostics, 2022, 12, 796–816.
212. S. J. Hoseyni, M. Manoochehri and M. D. Asli, Synthesis of Cobalt nanoparticles by Complex Demolition Method Using the Reaction between Organic Ligand Schiff base and Cobalt Chloride by Ultrasonication, Bull. Soc. R. Sci. Liege, 2017, 86, 325–331.
213. M. Summer, et al., Mode of Action of Biogenic Silver, Zinc, Copper, Titanium and Cobalt Nanoparticles Against Antibiotics Resistant Pathogens, J. Inorg. Organomet. Polym. Mater., 2024, 34, 1417–1451.
214. V. Dogra, et al., Bactericidal effects of metallosurfactants based cobalt oxide/hydroxide nanoparticles against Staphylococcus aureus, Sci. Total Environ, 2019, 681, 350–364.
215. A. T. Khalil, et al., Physical properties, biological applications and biocompatibility studies on biosynthesized single phase cobalt oxide (Co3O4) nanoparticles via Sageretia thea (Osbeck.), Arabian J. Chem., 2020, 13, 606–619.
216. A. A. Abass, W. A. M. Abdulridha, W. K. Alaarage, N. H. Abdulrudha and J. Haider, Evaluating the antibacterial effect of cobalt nanoparticles against multi-drug resistant pathogens, J. Med. Life, 2021, 14, 823–833.
217. S. M. Ansari, et al., Cobalt nanoparticles for biomedical applications: Facile synthesis, physiochemical characterization, cytotoxicity behavior and biocompatibility, Appl. Surf. Sci., 2017, 414, 171–187.
218. G. Guisbiers, et al., Inhibition of E. coli and S. aureus with selenium nanoparticles synthesized by pulsed laser ablation in deionized water, Int. J. Nanomed., 2016, 11, 3731–3736.
219. H. H. Lara, et al., Synergistic antifungal effect of chitosan-stabilized selenium nanoparticles synthesized by pulsed laser ablation in liquids against Candida albicans biofilms, Int. J. Nanomed., 2018, 13, 2697–2708.
220. D. M. Ridha, et al., Antibacterial and antibiofilm activities of selenium nanoparticles-antibiotic conjugates against anti-multidrug-resistant bacteria, Int. J. Pharm., 2024, 658, 124214.
221. L. D. Geoffrion, et al., Naked Selenium Nanoparticles for Antibacterial and Anticancer Treatments, ACS Omega, 2020, 5, 2660–2669.
222. T. Huang, et al., One-Step Synthesis of Antimicrobial Polypeptide-Selenium Nanoparticles Exhibiting Broad-Spectrum Efficacy against Bacteria and Fungi with Superior Resistance Prevention, ACS Appl. Mater. Interfaces, 2024, 16, 68996–69010.
223. A. N. Abd, M. F. Al and Z. A. Kadham, Antibacterial Activity Of Cadmium Oxide Nanoparticles Synthesized By Chemical, 3, 2016.
224. A. Regmi, Y. Basnet, S. Bhattarai and S. K. Gautam, Cadmium Sulfide Nanoparticles: Synthesis, Characterization, and Antimicrobial Study, J. Nanomater., 2023, 2023, 8187000.
225. A. Hashemi, M. Naseri, S. Ghiyasvand, E. Naderi and S. Vafai, Evaluation of physical properties, cytotoxicity, and antibacterial activities of calcium–cadmium ferrite nanoparticles, Appl. Phys. A: Mater. Sci. Process., 2022, 128, 236.
226. M. Malekzadeh, K. L. Yeung, M. Halali and Q. Chang, Preparation and antibacterial behaviour of nanostructured Ag@SiO2–penicillin with silver nanoplates, New J. Chem., 2019, 43, 16612–16620.
227. Z. Gounani, et al., Mesoporous silica nanoparticles carrying multiple antibiotics provide enhanced synergistic effect and improved biocompatibility, Colloids Surf., B, 2019, 175, 498–508.
228. M. N. Alandiyjany, et al., Novel In Vivo Assessment of Antimicrobial Efficacy of Ciprofloxacin Loaded Mesoporous Silica Nanoparticles against Salmonella typhimurium Infection, Pharmaceuticals, 2022, 15, 357.
229. N. Chaudhary, A. K. Yadav, J. G. Sharma and P. R. Solanki, Designing and characterization of a highly sensitive and selective biosensing platform for ciprofloxacin detection utilizing lanthanum oxide nanoparticles, J. Environ. Chem. Eng., 2021, 9, 106771.
230. N. Chaudhary, A. K. Yadav, D. Verma, J. G. Sharma and P. R. Solanki, An electrochemical immunosensor based on a nanostructured lanthanum oxide-substituted reduced graphene oxide interface for ultralow ciprofloxacin detection in milk samples, Mater. Adv., 2024, 5, 1597–1613.
231. J. Qi, et al., Carbon Dots as Advanced Drug-Delivery Nanoplatforms for Antiinflammatory, Antibacterial, and Anticancer Applications: A Review, ACS Appl. Nano Mater., 2023, 6, 9071–9084.
232. X. Xu, et al., Electrophoretic Analysis and Purification of Fluorescent Single-Walled Carbon Nanotube Fragments, ACS Publications, 2004, https://pubs.acs.org/doi/full/10.1021/ja040082h DOI:10.1021/ja040082h.
233. K. Wang, et al., Systematic safety evaluation on photoluminescent carbon dots, Nanoscale Res. Lett., 2013, 8, 122.
234. N. Chaudhary, D. Verma, A. K. Yadav, J. G. Sharma and P. R. Solanki, Rational hydrothermal-assisted green synthesis of blueish emitting carbon dots as an optical sensing platform for antibiotic detection in the milk sample, Talanta Open, 2023, 8, 100259.
235. X. Xu, et al., Aspirin-Based Carbon Dots, a Good Biocompatibility of Material Applied for Bioimaging and Anti-Inflammation, ACS Appl. Mater. Interfaces, 2016, 8, 32706–32716.
236. M. J. Meziani, et al., Visible-Light-Activated Bactericidal Functions of Carbon “Quantum” Dots, ACS Appl. Mater. Interfaces, 2016, 8, 10761–10766.
237. B. Guo, G. Liu, C. Hu, B. Lei and Y. Liu, The structural characteristics and mechanisms of antimicrobial carbon dots: a mini review, Mater. Adv., 2022, 3, 7726–7741.
238. P. Li, et al., Recent advances of carbon dots as new antimicrobial agents, SmartMat, 2022, 3, 226–248.
239. S. Walia, A. K. Shukla, C. Sharma and A. Acharya, Engineered Bright Blue- and Red-Emitting Carbon Dots Facilitate Synchronous Imaging and Inhibition of Bacterial and Cancer Cell Progression via 1O2-Mediated DNA Damage under Photoirradiation, ACS Biomater. Sci. Eng., 2019, 5, 1987–2000.
240. L.-N. Wu, et al., Levofloxacin-based carbon dots to enhance antibacterial activities and combat antibiotic resistance, Carbon, 2022, 186, 452–464.
241. M. Thakur, et al., Antibiotic Conjugated Fluorescent Carbon Dots as a Theranostic Agent for Controlled Drug Release, Bioimaging, and Enhanced Antimicrobial Activity, J. Drug Delivery, 2014, 2014, 282193.
242. R. Jijie, et al., Enhanced antibacterial activity of carbon dots functionalized with ampicillin combined with visible light triggered photodynamic effects, Colloids Surf., B, 2018, 170, 347–354.
243. D. I. Abu Rabe, et al., Carbon dots for highly effective photodynamic inactivation of multidrug-resistant bacteria, Mater. Adv., 2020, 1, 321–325.
244. J. S. Sidhu, S. Mayank, T. Pandiyan, N. Kaur and N. Singh, The Photochemical Degradation of Bacterial Cell Wall Using Penicillin-Based Carbon Dots: Weapons Against Multi-Drug Resistant (MDR) Strains, ChemistrySelect, 2017, 2, 9277–9283.
245. W.-B. Zhao, et al., Antibacterial Carbon Dots: Mechanisms, Design, and Applications, Adv. Healthcare Mater., 2023, 12, 2300324.
246. C. C. Lee, J. A. MacKay, J. M. J. Fréchet and F. C. Szoka, Designing dendrimers for biological applications, Nat. Biotechnol., 2005, 23, 1517–1526.
247. C. Galanakou, D. Dhumal and L. Peng, Amphiphilic dendrimers against antibiotic resistance: light at the end of the tunnel?, Biomater. Sci., 2023, 11, 3379–3393.
248. C. Galanakou, D. Dhumal and L. Peng, Amphiphilic dendrimers against antibiotic resistance: light at the end of the tunnel?, Biomater. Sci., 2023, 11, 3379–3393.
249. M. K. Calabretta, A. Kumar, A. M. McDermott and C. Cai, Antibacterial Activities of Poly(amidoamine) Dendrimers Terminated with Amino and Poly(ethylene glycol) Groups, Biomacromolecules, 2007, 8, 1807–1811.
250. T. N. Siriwardena, et al., Lipidated Peptide Dendrimers Killing Multidrug-Resistant Bacteria, J. Am. Chem. Soc., 2018, 140, 423–432.
251. A. S. Abd-El-Aziz, et al., Antimicrobial Organometallic Dendrimers with Tunable Activity against Multidrug-Resistant Bacteria, Biomacromolecules, 2015, 16, 3694–3703.
252. M. Ma, et al., Evaluation of polyamidoamine (PAMAM) dendrimers as drug carriers of anti-bacterial drugs using sulfamethoxazole (SMZ) as a model drug, Eur. J. Med. Chem., 2007, 42, 93–98.
253. K. Winnicka, M. Wroblewska, P. Wieczorek, P. T. Sacha and E. A. Tryniszewska, The Effect of PAMAM Dendrimers on the Antibacterial Activity of Antibiotics with Different Water Solubility, Molecules, 2013, 18, 8607–8617.
254. S. Alfei and D. Caviglia, Prevention and Eradication of Biofilm by Dendrimers: A Possibility Still Little Explored, Pharmaceutics, 2022, 14, 2016.
255. A. A. Chis, et al., Applications and Limitations of Dendrimers in Biomedicine, Molecules, 2020, 25, 3982.
256. K. Yue, et al., Synthesis, properties, and biomedical applications of gelatin methacryloyl (GelMA) hydrogels, Biomaterials, 2015, 73, 254–271.
257. M. Hamidi, A. Azadi and P. Rafiei, Hydrogel nanoparticles in drug delivery, Adv. Drug Delivery Rev., 2008, 60, 1638–1649.
258. A. L. Z. Lee, V. W. L. Ng, W. Wang, J. L. Hedrick and Y. Y. Yang, Block copolymer mixtures as antimicrobial hydrogels for biofilm eradication, Biomaterials, 2013, 34, 10278–10286.
259. E. De Giglio, et al., Ciprofloxacin-modified electrosynthesized hydrogel coatings to prevent titanium-implant-associated infections, Acta Biomater., 2011, 7, 882–891.
260. T. Dai, et al., A Nanocomposite Hydrogel with Potent and Broad-Spectrum Antibacterial Activity, ACS Appl. Mater. Interfaces, 2018, 10, 15163–15173.
261. J. Hu, et al., A smart aminoglycoside hydrogel with tunable gel degradation, on-demand drug release, and high antibacterial activity, J. Controlled Release, 2017, 247, 145–152.
262. R. Carpa, A. Remizovschi, C. A. Culda and A. L. Butiuc-Keul, Inherent and Composite Hydrogels as Promising Materials to Limit Antimicrobial Resistance, Gels, 2022, 8, 70.
263. R. G. Cuero, G. Osuji and A. Washington, N-carboxymethylchitosan inhibition of aflatoxin production: Role of zinc, Biotechnol. Lett., 1991, 13, 441–444.
264. S. N. Chirkov, The Antiviral Activity of Chitosan (Review), Appl. Biochem. Microbiol., 2002, 38, 1–8.
265. K. R. Raghupathi, R. T. Koodali and A. C. Manna, Size-Dependent Bacterial Growth Inhibition and Mechanism of Antibacterial Activity of Zinc Oxide Nanoparticles, Langmuir, 2011, 27, 4020–4028.
266. L. S. Reddy, M. M. Nisha, M. Joice and P. N. Shilpa, Antimicrobial activity of zinc oxide (ZnO) nanoparticle against Klebsiella pneumoniae, Pharm. Biol., 2014, 52, 1388–1397.
267. L. Zhang, Y. Jiang, Y. Ding, M. Povey and D. York, Investigation into the antibacterial behaviour of suspensions of ZnO nanoparticles (ZnO nanofluids), J. Nanopart. Res., 2007, 9, 479–489.
268. C. Wu, et al., Zinc as an agent for the prevention of biofilm formation by pathogenic bacteria, J. Appl. Microbiol., 2013, 115, 30–40.
269. T. Bjarnsholt, et al., Silver against Pseudomonas aeruginosa biofilms, Acta Pathol., Microbiol. Immunol. Scand., 2007, 115, 921–928.
270. M. I. A. A. Maksoud, et al., Antibacterial, antibiofilm, and photocatalytic activities of metals-substituted spinel cobalt ferrite nanoparticles, Microb. Pathog., 2019, 127, 144–158.
271. J. S. Ajarem, S. N. Maodaa, A. A. Allam, M. M. Taher and M. Khalaf, Benign Synthesis of Cobalt Oxide Nanoparticles Containing Red Algae Extract: Antioxidant, Antimicrobial, Anticancer, and Anticoagulant Activity, J. Cluster Sci., 2022, 33, 717–728.
272. T. Kavitha, S. Haider, T. Kamal and M. Ul-Islam, Thermal decomposition of metal complex precursor as route to the synthesis of Co3O4 nanoparticles: Antibacterial activity and mechanism, J. Alloys Compd., 2017, 704, 296–302.
273. B. Sun, et al., Insight into the effect of particle size distribution differences on the antibacterial activity of carbon dots, J. Colloid Interface Sci., 2021, 584, 505–519.
274. H. Li, et al., Degradable Carbon Dots with Broad-Spectrum Antibacterial Activity, ACS Appl. Mater. Interfaces, 2018, 10, 26936–26946.
275. A. K. Yadav, D. Verma, S. Tabassum and P. R. Solanki, Functionalized Graphitic Carbon Nitride Based Aptasensing Platform for Electrochemical Detection of Helicobacter Pylori, IEEE Sens. Lett., 2023, 7, 1–4.
276. M. Nikzamir, A. Akbarzadeh and Y. Panahi, An overview on nanoparticles used in biomedicine and their cytotoxicity, J. Drug Delivery Sci. Technol., 2021, 61, 102316.
277. S. Z. Alshawwa, A. A. Kassem, R. M. Farid, S. K. Mostafa and G. S. Labib, Nanocarrier Drug Delivery Systems: Characterization, Limitations, Future Perspectives and Implementation of Artificial Intelligence, Pharmaceutics, 2022, 14, 883.
278. P. Ganguly, A. Breen and S. C. Pillai, Toxicity of Nanomaterials: Exposure, Pathways, Assessment, and Recent Advances, ACS Biomater. Sci. Eng., 2018, 4, 2237–2275.
279. M. A. Dobrovolskaia, P. Aggarwal, J. B. Hall and S. E. McNeil, Preclinical Studies To Understand Nanoparticle Interaction with the Immune System and Its Potential Effects on Nanoparticle Biodistribution, Mol. Pharm., 2008, 5, 487–495.
280. Y.-N. Zhang, W. Poon, A. J. Tavares, I. D. McGilvray and W. C. W. Chan, Nanoparticle–liver interactions: Cellular uptake and hepatobiliary elimination, J. Controlled Release, 2016, 240, 332–348.
281. N. Desai, Challenges in Development of Nanoparticle-Based Therapeutics, AAPS J., 2012, 14, 282–295.
282. N. Niño-Martínez, M. F. Salas Orozco, G.-A. Martínez-Castañón, F. Torres Méndez and F. Ruiz, Molecular Mechanisms of Bacterial Resistance to Metal and Metal Oxide Nanoparticles, Int. J. Mol. Sci., 2019, 20, 2808.
283. M. Salas-Orozco, et al., Mechanisms of Resistance to Silver Nanoparticles in Endodontic Bacteria: A Literature Review, J. Nanomater., 2019, 2019, 7630316.
284. J. L. Graves, et al., Rapid evolution of silver nanoparticle resistance in Escherichia coli, Front. Genet., 2015, 6, 42.
285. O. Długosz, K. Szostak, A. Staroń, J. Pulit-Prociak and M. Banach, Methods for Reducing the Toxicity of Metal and Metal Oxide NPs as Biomedicine, Materials, 2020, 13, 279.
286. B. Kong, J. H. Seog, L. M. Graham and S. B. Lee, Experimental considerations on the cytotoxicity of nanoparticles, Nanomedicine, 2011, 6, 929–941.
287. H. E. Thu, M. Haider, S. Khan, M. Sohail and Z. Hussain, Nanotoxicity induced by nanomaterials: A review of factors affecting nanotoxicity and possible adaptations, OpenNano, 2023, 14, 100190.
288. R. Foulkes, et al., The regulation of nanomaterials and nanomedicines for clinical application: current and future perspectives, Biomater. Sci., 2020, 8, 4653–4664.
289. E. D. Namiot, A. V. Sokolov, V. N. Chubarev, V. V. Tarasov and H. B. Schiöth, Nanoparticles in Clinical Trials: Analysis of Clinical Trials, FDA Approvals and Use for COVID-19 Vaccines, Int. J. Mol. Sci., 2023, 24, 787.
290. J. K. Patra, et al., Nano based drug delivery systems: recent developments and future prospects, J. Nanobiotechnol., 2018, 16, 1–33.
291. E. D. Namiot, A. V. Sokolov, V. N. Chubarev, V. V. Tarasov and H. B. Schiöth, Nanoparticles in Clinical Trials: Analysis of Clinical Trials, FDA Approvals and Use for COVID-19 Vaccines, Int. J. Mol. Sci., 2023, 24, 787.
292. F. Cao, et al., Defect-Rich Adhesive Nanozymes as Efficient Antibiotics for Enhanced Bacterial Inhibition, Angew. Chem., Int. Ed., 2019, 58, 16236–16242.
293. C. Zhou, Q. Wang, J. Jiang and L. Gao, Nanozybiotics: Nanozyme-Based Antibacterials against Bacterial Resistance, Antibiotics, 2022, 11, 390.
294. J. K. Patra, et al., Nano based drug delivery systems: recent developments and future prospects, J. Nanobiotechnol., 2018, 16, 71.

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Footnote

† These authors contributed equally.

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