Themed collection FOCUS: Recent progress on bioimaging technologies

In this review, the molecular design and stimuli-responsive approach of activatable NIR-II organic fluorophores are introduced. Their applications in biomedical fields, ranging from biosensing to bioimaging and theranostics, are also highlighted.

This review gives focused attention on in vivo anion imaging based on activatable organic photoacoustic probes, with emphasis on imaging mechanisms at the molecular level, to inspire innovative ideas for future theranostics of diseases.

This critical review summarises the recent biological applications of transition metal complexes as cellular probes, bioimaging reagents and phototherapeutics.

This review summarizes the progress of AIE polymers in sensing, imaging and theranostic applications in the recent 3 years, and the perspective and future development of AIE polymers are discussed briefly.

Schematic diagram of NIR J-aggregates of various organic dyes as effective bioimaging (fluorescence (FL) or photoacoustic (PA)) and therapeutic agents (PDT or PTT).

Herein, the latest progress of AIEgens for application in wash-free detection and bioimaging was reviewed.

Versatile synthesis for all rare earth oxysulfides (RE₂O₂S) and evaluation of the potential of ultrasmall Gd_0.8Nd_1.2O₂S as a multimodal contrast agent.

Schematic illustration of the amphiphilic BODIPY-based photosensitizers for multimodal imaging-guided phototherapy through J-aggregation.

This work demonstrated that the aggregation and de-aggregation strategy of AIEgens in nanomicelles is very attractive for constructing multifunctional theranostic probes.

This work provides a novel glutathione depletion-mediated in situ transformation strategy for enhanced tumor-specific imaging and photoimmunotherapy.

NaLuF₄:Eu³⁺ nanoscintillator with enhanced radioluminescence was boosted by the sensitization effect of Tb³⁺ on Eu³⁺ with an excellent X-ray scintillation performance, and further applied in X-ray imaging with high contrast for different samples.

We have synthesized Eu-doped NaBi(MoO₄)₂ nanoparticles functionalized with PAA whose properties make them excellent multimodal contrast agents for X-ray computed tomography and luminescent bioimaging, as illustrated using a C. Elegans animal model.

The search for efficient gas carriers for biomedical applications presents a challenging task due to the kinetics of gas adsorption/desorption. This article presents a novel approach utilizing Gd-LTL zeolite crystals for oxygen delivery combined with an MRI study.

Surface engineering of highly luminescent AuAg nanoclusters via triphenylphosphine conjugation enables targeted mitochondrial and in vivo brain imaging.

A broadband NIR phosphor covering the 750–1200 nm region with high luminescence efficiency and good thermal stability was realized by the energy transfer of Cr³⁺ → Yb³⁺.

The integration of second harmonic generation (SHG) microscopic imaging and aggregation-induced emission fluorescence imaging would greatly boost the imaging outcomes because of the combination of merits in each imaging modality.

A highly biocompatible long-lived fluorescence micelle nanoprobe AI-Cz-M was constructed for tracking the formation and dynamics of lipid droplets in living tumor cells and adipocytes in real-time and quantitatively.

Most fluorescent probes can only be used for targeted imaging of single organelles, we herein develop a photoactivatable probe for tandem imaging of different organelles and in situ monitoring of their interplay with simple operation.

This work represents the harnessing of water-soluble emissive materials for bioimaging application via biogenic amine-induced transient assembly and disassembly.

Boron-assisted highly symmetric rigid Ln macrocycles were designed and synthesized, showing high brightness and promising potential applications in bioimaging.

The one-step regulation of planarization and donor rotation provided a convenient method to design theranostic agents for elevating imaging and therapy simultaneously.

HA-RdB-EDS NPs possess excellent optical properties, anti-interference capability and lysosome-targeted ability. Significantly, HA-RdB-EDS NPs can turn on the fluorescence according to the lysosomal pH changes induced by Baf-A1 in HepG2 cells.

An in vivo and an in vitro investigation of the hydrophobic interaction between HPTS and the gadolinium(III)-complex of tetra-aza macrocyclic ligand HP-DO3A (Gd(HP-DO3A)) are reported.

An ultralong blue RTP effect with lifetime up to 1116.10 ms has been achieved by cycloalkyl modification of phenothiazine-5,5-dioxide.

A simple strategy is proposed to synthesize highly uniform garnet-based nanospheres that exhibit colloidal stability in physiological media, high biocompatibility and both green and NIR persistent luminescence.

TC3 cations loaded on hyaluronic acid were selectively taken up by cancer cells. The following incubation with A5 or A10 anions led to the bioorthogonal self-assembly of C3–A5/A10 in cancer cells with luminescence and singlet oxygen turn-on.

Antibody decorated nanoparticles with brightly red emissions are promising probes for targeted detection of cancer cells due to their excellent specificity, deep penetration depth, high photostability and low phototoxicity.

We successfully fabricated a pure phase 2D perovskite single crystal BA₂PbBr₄. We applied it as a wafer in the field of X-rays imaging and showed good imaging performance impressive environmental and temperature stability.

A series of PTT agents based on ‘D–π–A’-type chromophores with different electron-donating groups were constructed to optimize their photothermal performance at 808 nm after nanogel loading.

The synthesis of the AIE fluorescent supramolecular polymer TPE-B@Q[10] is reported. This system exhibits excellent blue emission properties, good biocompatibility and was successfully employed for cytoplasmic imaging of cells.

We report novel cucurbit[6]uril (Q[6])/carbon quantum dots (CQDs) prepared by solvothermal and nitrogen doped methods.

Cu(II) complexes formed with cross-bridged pentaazamacrocycle ligands exhibit high stability and appropriate inertness, as well as fast complex formation auguring a bright future for this ligand family in radiotheranostic applications.

This work provides a new type of nanoplatform of a metal–organic framework (MOF)-based hybrid material for fluorescence imaging-guided synergistic phototherapy.

A Zn^II responsive Mn^II-based MRI contrast agent, [Mn(PC2A-DPA)], has been synthesized, investigated and applied in imaging studies. It shows high stability and excellent inertness and can be used to visualize glucose triggered Zn^II release by MRI.

We report the first single AIEgen that has great potential for dual-imaging of mitochondria/LDs, detection of cell viability and simultaneously photodynamic ablation of cancer cells.

An NIR-emitting MgGeO₃:Mn²⁺,Yb³⁺ persistent phosphor chargeable with red light has been developed. The features of red-light charging and NIR persistent luminescence make this phosphor hold great potential for biomedical imaging and optical data storage.

A biodegradable gadolinium-doped mesoporous bismuth-based nanomaterial is used to diagnose kidneys with dysfunction accurately via magnetic resonance imaging in vivo.

Metal-free room temperature phosphorescence free of the constraint of a rigid environment was achieved by building selenium-based ICT systems. Hypoxia in cells and tumors can be imaged conveniently by molecules according to the proposed strategy.

A convenient rhenium-based multimodal mitochondrial-targeted probe compatible with Synchrotron Radiation X-ray Fluorescence nano-imaging.

Tumor microenvironment-triggered supramolecular nanosystems were fabricated, which showed excellent ability in cancer precision diagnosis and synergistic therapy.

A natural AIE-active PS (PaH) is utilized to bind into DNA-T for cancer theranostics. The constructed PaH@DNA-T exhibits highly boosted fluorescence intensity and ROS generation, as well as much higher cell uptake efficiency.

HD-Zn was constructed for reversible ratiometric PA Zn²⁺ imaging in vivo. Zn²⁺ titration experiments together with a theoretical study suggests that Zn²⁺ chelation-induced ICT alteration in HD-Zn is responsible for its ratiometric PA sensing ability.

Novel near-infrared lipid droplet-specific α-tetraphenyletheneBODIPY nanoprobes exhibited bright aggregated state quantum yields up to 0.81 in aqueous system and were applied for real-time bioimaging.

New “all-in-one” theranostic systems, combining a magnetic resonance imaging contrast agent with a biphotonic photodynamic therapy photosensitiser generating cytotoxic singlet oxygen, were successfully developed and characterized.

A versatile red/near-infrared AIE probe, TTPy-H₂O₂, was developed for the specific visualization of H₂O₂ with mitochondria targeting ability, meanwhile achieving efficient photodynamic therapy for cancer cells.

A near-infrared AIE probe was developed for super-resolution imaging and nuclear lipid droplets dynamic study with good biocompatibility and high photostability.

C6-BD equipped with AIE and ESIPT characteristics was used to visualize the cell membrane with high selectivity, stability, and wash-free operation. It also universal for imaging of bacteria and fungi with light-excited killing via ROS generation.

A facile synthesized AIE bioprobe was developed to detect peroxynitrite sensitively and specifically. This bioprobe can realize both in vitro ONOO⁻ detection and in vivo visualization of inflammation.

A nanoprobe responsive to specific biomarkers with aggregation-induced emission has been developed for locating and guiding resection of tumors via optoacoustic and fluorescence imaging.

A synergetic imaging platform was established to achieve LDs-specific imaging by STED nanoscopy and TPF microscopy. Benefiting from its high PLQYs, outstanding photo-stability, and high LDs specificity, a superior resolution in cells and a deep penetration depth in tissues were achieved.

Supramolecular nanoparticles with enhanced aggregation-induced emission are prepared by taking advantage of pillar[5]arene-based host–guest complexation, and are sophisticated nanocarriers for imaging-guided drug delivery.

A WO_3−x-based nanotheranostic has been successfully fabricated for photoacoustic imaging-guided synergistic tumor targeting therapy in the second near-infrared (NIR-II) biological window.

An effective strategy was constructed for the small-scale preparation of AIE-active Pdots, which displayed reversibly distinct dual-color fluorescence in cancer cells.

An organic small molecule T-BDP with D–A–D structure was designed and synthesized and could self-assemble into nanoparticles with significant AIE performance. Under 635 nm laser irradiation, T-BDP NPs ablate cancer cells through photodynamic/photothermal synergistic effects.