Hypoxia-tropic nanozymes as oxygen generators for tumor-favoring theranostics

Oxygen deficiency is the main obstacle of hypoxia-related theranostics, thus this is a considerable amount of research focusing on the development of methods to supply oxygen by taking advantage of hypoxia-responsive properties of nanoparticles. However, strategies to properly penetrate hypoxic regions by the nanoparticles remains an unmet challenge. In this work, a biomimetic nanozyme capable of possessing catalase-like activity and the efficient direct penetration of hypoxic areas in tumor tissues was developed to supply oxygen based on catalytic tumor microenvironment-responsive reaction, providing substantial tumor hypoxia relief with nearly 3-fold reduction compared to untreated tumor tissues. To demonstrate the advantages of the nanozymes in overcoming hypoxia, a theranostic nanosystem model composed of the core/shell nanozymes and aggregation-induced emission (AIE) molecules was designed. The nanosystem was able to present multi-modal imaging of tumors and modulated the tumor microenvironment for improved photodynamic therapy (PDT) by cascade reactions of therapeutic effector molecules, thereby providing significantly enhanced therapeutic benefits in inhibiting tumor growth and lung metastasis of orthotopic breast cancer. This conceptual study showed the multifaceted features of biomimetic nanozymes as tumor therapeutics and demonstrated the encouraging potential for modulating hypoxia as an application for tumor theranostics.

AIE Featured Inorganic-Organic Core@Shell Nanoparticles for High-Efficiency siRNA Delivery and Real-Time Monitoring

RNA interference (RNAi) is demonstrated as one of the most powerful technologies for sequence-specific suppression of genes in disease therapeutics. Exploration of novel vehicles for small interfering RNA (siRNA) delivery with high efficiency, low cytotoxicity, and self-monitoring functionality is persistently pursued. Herein, by taking advantage of aggregation-induced emission luminogen (AIEgen), we developed a novel class of Ag@AIE core@shell nanocarriers with regulable and uniform morphology. It presented excellent efficiencies in siRNA delivery, target gene knockdown, and cancer cell inhibition in vitro. What's more, an anticancer efficacy up to 75% was achieved in small animal experiments without obvious toxicity. Attributing to the unique AIE properties, real-time intracellular tracking of siRNA delivery and long-term tumor tissue imaging were successfully realized. Compared to the commercial transfection reagents, significant improvements were obtained in biocompatibility, delivery efficiency, and reproducibility, representing a promising future of this nanocarrier in RNAi-related cancer therapeutics.

Incorporating spin-orbit coupling promoted functional group into an enhanced electron D-A system: A useful designing concept for fabricating efficient photosensitizer and imaging-guided photodynamic therapy

Intersystem crossing (ISC) is of great significance in photochemistry, and has a decisive influence on the properties of photosensitizers (PSs) for use in photodynamic therapy (PDT). However, the rationally design PSs with efficient ISC processes to implement superb reactive oxygen species (ROS) production is still a very challenging work. In this contribution, we described how a series of high-performance PSs were constructed through electron acceptor and donor engineering by integrating the smaller singlet-triplet energy gap (ΔE_ST) and larger spin-orbit coupling (SOC)-beneficial functional groups into the PS frameworks. Among the yielded various PSs, TaTIC was confirmed as the best candidate for application in PDT, which was due to its most outstanding ROS generation capability, bright near-infrared (NIR) fluorescence with peak over 840 nm, as well as desired aggregation-induced emission (AIE) features. Importantly, the ROS generation efficiency of TaTIC was even superior to that of some popularly used PSs, including the most reputable PS of Rose Bengal. In order to further extend therapeutic applications, TaTIC was encapsulated with biocompatible amphiphilic matrix and formulated into water-dispersed nanoparticles (NPs). More excitedly, the as-prepared TaTIC NPs gave wonderful PDT performance on tumor-bearing mouse model, actualizing complete tumor elimination outcomes. Coupled with excellent biosecurity, TaTIC NPs would be a promising theranostic agent for practical clinical application.

Chemo-photodynamic therapy with light-triggered disassembly of theranostic nanoplatform in combination with checkpoint blockade for immunotherapy of hepatocellular carcinoma

Background

Hepatocellular carcinoma (HCC) is a common malignant tumor with high rate of metastasis and recurrence. Although immune checkpoint blockade (ICB) has emerged as a promising type of immunotherapy in advanced HCC, treatment with ICB alone achieves an objective remission rate less than 20%. Thus, combination therapy strategies is needed to improve the treatment response rate and therapeutic effect.

Methods

 A light-triggered disassembly of nanoplatform (TB/PTX@RTK) co-loaded an aggregation induced emission (AIE) photosensitizer (TB) and paclitaxel (PTX) was prepared for on-command drug release and synergistic chemo-photodynamic therapy (chemo-PDT). Nano-micelles were characterized for drug loading content, hydrodynamic size, absorption and emission spectra, reactive oxygen species production, and PTX release from micelles. The targeted fluorescence imaging of TB/PTX@RTK micelles and the synergistic anti-tumor efficacy of TB/PTX@RTK micelles-mediated chemo-PDT combined with anti-PD-L1 were assessed both in vitro and in vivo.

Results

The TB/PTX@RTK micelles could specifically accumulate at the tumor site through cRGD-mediated active target and facilitate image-guided PDT for tumor ablation. Once irradiated by light, the AIE photosensitizer of TB could produce ROS for PDT, and the thioketal linker could be cleaved by ROS to precise release of PTX in tumor cells. Chemo-PDT could not only synergistically inhibit tumor growth, but also induce immunogenic cell death and elicit anti-tumor immune response. Meanwhile, chemo-PDT significantly upregulated the expression of PD-L1 on tumor cell surface which could efficiently synergize with anti-PD-L1 monoclonal antibodies to induce an abscopal effect, and establish long-term immunological memory to inhibit tumor relapse and metastasis.

Conclusion

Our results suggest that the combination of TB/PTX@RTK micelle-mediated chemo-PDT with anti-PD-L1 monoclonal antibodies can synergistically enhance systemic anti-tumor effects, and provide a novel insight into the development of new nanomedicine with precise controlled release and multimodal therapy to enhance the therapeutic efficacy of HCC.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-01101-1.

Single-probe multistate detection of DNA via aggregation-induced emission on a graphene oxide platform

Graphene and graphene oxides (GO), or their reduced forms, have been introduced in a variety of biosensing platforms and have exhibited enhanced performance levels in these forms. We herein report a DNA sensing platform consisting of aggregation-induced emission (AIE) molecules and complementary DNA (comDNA) adsorbed on GO. We experimentally turned the AIE molecule on and off by adjusting its distance, which correlates with DNA structures as shown in our computational results, from the GO sheet, which quenches depending on its distance from the graphene plane. The changes in florescence are reproducible, which demonstrates the probe's ability to identify the binding state of the DNA. Our molecular dynamics simulation results reveal strong π-π interactions between single-strand DNA (ssDNA) and GO, which enable the ssDNA molecule to move closer to the graphene oxide. This reduces the center of mass and binding free energies in the simulation. When hybridized with comDNA, the increased distance, evidenced by the reduced interaction, eliminates the quenching effect and turns on the AIE molecule. Our protocol use of the AIE molecule as a probe thus avoids the complicated steps involved in covalent functionalization and allows the rapid and label-free detection of DNA molecules.

STATEMENT OF SIGNIFICANCE

A simple, rapid method of fluorescent measurement of DNA hybridization in the presence of graphene (oxide) is presented. Conventional fluorescent dyes offer high performance in biosensors. However, labeling procedures are synthetically demanding in time and resources making it less cost-effective. Molecules with aggregation-induced-emission (AIE) property have advantages over traditional fluorescent molecules because of their intrinsic preference for detection as a turn-on probe and their single-molecule detection ability. Previous work has shown AIE dyes act as excellent "label-free" bioprobes with high sensitivity but with limited selectivity. Graphene oxide (GO) with its unique optical properties and affinity to different kinds of biomolecules can be used as an auxiliary to enhance selectivity of AIE dyes. In this work, we report a label-free strategy to detect DNA of particular sequence by water-soluble AIE probes with the aid of GO, supported by the computational explanations for this phenomenon.

AIE-active polymeric micelles based on modified chitosan for bioimaging-guided targeted delivery and controlled release of paclitaxel

In this study, a novel polymer based on aggregation-induced emission (AIE) fluorogen, biotin and disulfide bonds modified chitosan (TPE-bi(SS-CS-Bio)) was designed and synthesized. The polymer could self-assemble into micelles in aqueous media and encapsulate paclitaxel (PTX) into the core with high drug loading. Fluorescence study indicated that the micelles exhibited excellent AIE feature with intense blue fluorescence emitted. In vitro drug release study indicated that the micelles could disassemble rapidly in the presence of high level of glutathione. The modification by biotin could enhance the cellular uptake of the micelles. The drug-loaded micelles possessed remarkable cytotoxicity against MCF-7 cells, and their distribution in the cells could be traced due to the excellent AIE feature. In vivo antitumor efficacy study demonstrated the superior antitumor activity of the PTX-loaded TPE-bi(SS-CS-Bio) micelles. These results indicated that TPE-bi(SS-CS-Bio) has the ability of biological imaging and can be used as a potential carrier for PTX.

Sulfuric-acid-mediated synthesis strategy for multi-colour aggregation-induced emission fluorescent carbon dots: Application in anti-counterfeiting, information encryption, and rapid cytoplasmic imaging

Aggregation-induced emission fluorescent carbon dots (AIE-CDs) have applications in the fields of multi-colour anti-counterfeiting, information encryption, and imaging. In this study, four AIE-CDs (B-AIE-CDs, G-AIE-CDs, Y-AIE-CDs, and O-AIE-CDs) with blue, green, yellow, and orange fluorescence at high concentrations were fabricated using crystal violet as a precursor, solutions with different sulfuric acid concentrations as solvents under different temperatures and reaction times for the first time. The structural properties and fluorescence behaviour of the AIE-CDs were investigated. The results revealed that the sulfuric acid concentration had a significant effect on the fluorescence colour of the AIE-CDs because sulfuric acid can affect the degree of carbonisation, the type and content of nitrogen. Moreover, the reaction temperature and time affected the surface-defect state and the degree of carbonisation of the AIE-CDs, which affected the emission wavelength and quantum yield (QY) of the AIE-CDs. Furthermore, to exploit the unique characteristics (polychromatic aggregation fluorescence and acid-sensitive properties) of the obtained-AIE-CDs, anti-counterfeiting and information encryption methodologies (i.e., acid-stimuli-response producing multi-colour fluorescence) were preliminarily developed. Finally, B-AIE-CDs with a high QY of 43.5% were successfully used for rapid cytoplasmic imaging, demonstrating their applicability in biological fields.

A TICT + AIE based fluorescent probe for ultrafast response of hypochlorite in living cells and mouse

Hypochlorite (HClO/ClO^-), an important reactive oxygen species (ROS), plays a significant role in the human immune system. Thus, developing a fast and efficient method for detecting ClO^- is quite necessary. Herein, we designed and synthesized a fluorescent probe TPB-CN based on twisted intramolecular charge transfer (TICT) and aggregation-induced emission (AIE) characteristics. The probe could respond to ClO^- with an ultrafast response velocity (<2 s). The detection limit was calculated to be 6.198 nM. In addition, probe TPB-CN was successfully applied for detecting ClO^- in living cells and mouse.

Design and fabrication of chitosan-based AIE active micelles for bioimaging and intelligent delivery of paclitaxel

In this study, cetyl 4-formylbenzoate alkyl and 4-(2-hydroxyethoxy) benzophenonesalicylaldazide modified biotinylated chitosan (CS-BT-HBS-CB) featured with aggregation-induced emission (AIE) characteristic, active tumor-targeting ability and pH-responsive drug release property was designed and synthesized. The polymer was fabricated by introducing hydrophobic segment, tumor targeting ligand, acid-sensitive bond and AIE fluorophore to the backbone of chitosan. Due to its amphiphilicity, the polymer could self-assemble into micelles and encapsulate paclitaxel (PTX) to form PTX-loaded CS-BT-HBS-CB micelles. The mean size of the micelles was 167 nm, which was beneficial to the EPR effect. Moreover, with the help of above functional groups, the micelles exhibited excellent AIE effect, triggered drug release behavior by acidic condition, selective internalization by MCF-7 cells and excellent cellular imaging capability. In vivo studies revealed that the PTX-loaded CS-BT-HBS-CB micelles could enhance the antitumor efficacy with low systemic toxicity. This micellar system would be a potential candidate for cancer therapy and bioimaging.

A multifunctional AIE gold cluster-based theranostic system: tumor-targeted imaging and Fenton reaction-assisted enhanced radiotherapy

BACKGROUND

As cancer is one of the main leading causes of mortality, a series of monotherapies such as chemotherapy, gene therapy and radiotherapy have been developed to overcome this thorny problem. However, a single treatment approach could not achieve satisfactory effect in many experimental explorations.

RESULTS

In this study, we report the fabrication of cyclic RGD peptide (cRGD) modified Au₄-iron oxide nanoparticle (Au₄-IO NP-cRGD) based on aggregation-induced emission (AIE) as a multifunctional theranostic system. Besides Au₄ cluster-based fluorescence imaging and enhanced radiotherapy, iron oxide (IO) nanocluster could realize magnetic resonance (MR) imaging and Fenton reaction-based chemotherapy. Abundant toxic reactive oxygen species generated from X-ray irradiation and in situ tumor-specific Fenton reaction under acidic microenvironment leads to the apoptotic and necrotic death of cancer cells. In vivo studies demonstrated good biocompatibility of Au₄-IO NP-cRGD and a high tumor suppression rate of 81.1% in the synergistic therapy group.

CONCLUSIONS

The successful dual-modal imaging and combined tumor therapy demonstrated AIE as a promising strategy for constructing multifunctional cancer theranostic platform.

AIEgen-based nanoprobe for the ATP sensing and imaging in cancer cells and embryonic stem cells

A turn-on fluorescent nanoprobe (named AAP-1), based on an aggregation-induced emission luminogen (AIEgen), is disclosed for the detection of adenosine triphosphate (ATP), which is an essential element in the biological system. Organic fluorophore (named TPE-TA) consists of tetraphenylethylene (TPE, sensing and signaling moiety) and mono-triamine (TA, sensing moiety), and it forms an aggregated form in aqueous media as a nanoprobe AAP-1. The nanoprobe AAP-1 has multiple electrostatic interactions as well as hydrophobic interactions with ATP, and it displays superior selectivity toward ATP, reliable sensitivity, with a detection limit around 0.275 ppb, and fast responsive (signal within 10 s). Such a fluorescent probe to monitor ATP has been actively pursued throughout fundamental and translational research areas. In vitro assay and a successful cellular ATP imaging application was demonstrated in cancer cells and embryonic stem cells. We expect that our work warrants further ATP-related studies throughout a variety of fields.

A novel fluorescent probe with ACQ-AIE conversion by alkyl chain engineering for simultaneous visualization of lipid droplets and lysosomes

The AIE bio-probes have attracted extensive attention because of their good brightness, long-term in situ retention ability, photostability and low cytotoxicity. Recently, the transformation of ACQ to AIE has become very popular, which is very important for the further development of AIE probes. Herein, a series of novel dyes (NR-Lyso-Ⅰ, NR-Lyso-Ⅱ, NR-Lyso-III, NR-Lyso-IV) were designed and synthesized. It was found that alkylation of 4-aminonaphthalimide could achieve the transformation of the dye from ACQ to AIE effect due to the growth of carbon chain. Moreover, the AIE probe NR-Lyso-IV exhibited dual-state emission (DSE) and large Stokes shift (＞100 nm), excellent selectivity, photostability, and low cytotoxicity, which was able to simultaneous visualize the lipid droplets (LDs) and lysosomes of HeLa cells and zebrafish.

AIEgens Barcodes Combined with AIEgens Nanobeads for High-sensitivity Multiplexed Detection

Suspension arrays based on optical encoded microspheres have attracted great attention for multiplexed detection in gene analysis, protein profiling, early disease diagnosis, treatment monitoring and so on. However, the fluorescence stability of barcodes and detection sensitivity require further improvement to meet the increasing demands of “precision diagnosis”. Methods: This work reports a novel suspension array platform based on extremely stable AIEgens (AIE33 and AIE NIR800) microbeads as barcodes and AIEgens (1,1,2,3,4,5-Hexaphenyl-1H-silole, HPS) nanobeads as fluorescent signal reporter coupled with flow cytometry for multiplexed detection. Results: Due to the excellent fluorescent signal amplification effect of the HPS nanobeads, our multiplex assay showed enhanced detection sensitivity, compared to multiplex assay using QDs nanobeads (up to 3-fold improvement) and commercial organic dye of phycoerythrin (up to 5-fold improvement) as the fluorescent signal reporters. Conclusion: Furthermore, validating experiments showed similar detection performance to the clinical gold-standard method of ImmunoCAP for allergen detection in patient serum samples, demonstrating the suspension array platform based on AIEgens microbeads with excellent fluorescence stability and AIEgens nanobeads with strong signal amplification ability is promising for high-sensitivity multiplexed bioassay applications.

A water-soluble molecular probe with aggregation-induced emission for discriminative detection of Al3+ and Pb2+ and imaging in seedling root of Arabidopsis

Luminogens with aggregation-induced emission (AIE) have been used to develop a new type of molecular probes based on analyte-triggered aggregation, but it still remains a challenge to design water-soluble AIE-active probe for specific detection of metal ions. Herein, we designed and synthesized a water-soluble molecular probe with AIE property for discriminative detection of aluminum ion and lead ion. Four carboxylic acid groups were incorporated into a tetraphenylethylene unit to enhance the coordination affinity and increase water-solubility in aqueous solution. The designed probe can be selectively lighted up by aluminum ion and lead ion via coordination-triggered AIE process. Discrimination of aluminum ion and lead ions based on the probe can be achieved in quantitative manner with the assistance of suitable masking reagents. This probe was further used to image aluminum ions in living cells of seedling roots of Arabidopsis, and the results showed that this probe is capable of imaging aluminum ions in living cells avoiding the interference of lead ions, and is suited for long-term imaging due to its excellent photostability. This work expands the application scope of AIE-active probes in discriminative detection of metal ions, and provides a design direction for water-soluble AIE probes to avoid the false signals from self-precipitation under physiological conditions.

FRET processes of bi-fluorophoric sensor material containing tetraphenylethylene donor and optical-switchable merocyanine acceptor for lead ion (Pb2+) detection in semi-aqueous media

A novel aggregation-induced emission (AIE) structure containing a tetraphenylethene (TPE) unit covalently linked with a merocyanine (MC) unit was synthesized and investigated in semi-aqueous solutions with 90% water fraction. The open-form structure of red-emissive MC unit combined with TPE unit was utilized as a bi-fluorophoric sensor to detect lead(II) ion, which could be transformed from the close-form structure of non-emissive SP unit upon UV exposure. Moreover, the TPE unit as an energy donor with the blue-green photoluminescence (PL) emission at 480 nm was combined with the MC unit as an energy acceptor with the red PL emission at 635 nm. Due to the Förster resonance energy transfer (FRET) processes, the bi-fluorophoric sensor produced more efficient ratiometric PL behavior to induce a stronger red PL emission than that of the mono-fluorophoric MC unit. Hence, the PL sensor responses of the AIE bi-fluorophoric structure toward lead(II) ion could be further amplified via the FRET-OFF processes to turn off red PL emission of the coordinated MC acceptor and to recover blue-green PL emission of the TPE donor. Accordingly, the best LOD value for the AIE sensor detection toward Pb2+ was 0.27 μM. The highest red MC emission with the optimum FRET process of AIE sensor could be utilized in cell viability tests to prove the non-toxic and remarkable bio-marker of AIE sensor to detect lead(II) ion in live cells. The developed FRET-OFF processes with ratiometric PL behavior of the bi-fluorophoric AIE sensor can be utilized for future chemo- and bio-sensor applications.

Applications of smartphone-based near-infrared (NIR) imaging, measurement, and spectroscopy technologies to point-of-care (POC) diagnostics

The role of point-of-care (POC) diagnostics is important in public health. With the support of smartphones, POC diagnostic technologies can be greatly improved. This opportunity has arisen from not only the large number and fast spread of cell-phones across the world but also their improved imaging/diagnostic functions. As a tool, the smartphone is regarded as part of a compact, portable, and low-cost system for real-time POC, even in areas with few resources. By combining near-infrared (NIR) imaging, measurement, and spectroscopy techniques, pathogens can be detected with high sensitivity. The whole process is rapid, accurate, and low-cost, and will set the future trend for POC diagnostics. In this review, the development of smartphone-based NIR fluorescent imaging technology was described, and the quality and potential of POC applications were discussed.

Poly(amino acid)s-based star AIEgens for cell uptake with pH-response and chiral difference

Chiral aggregation-induced emission luminogens (AIEgens) are the new-generation chiral sensors that regulate chiral signals from the molecular level to the macroscopic assembly. Expanding applications of chiral AIEgens and in-depth understanding of their chiral recognition in biological systems are meaningful. Herein, two star chiral AIEgens, consisting of tetraphenylethene (TPE) as core and poly(N-acryloyl-L(D) valine) (PLV or PDV) as arms, were precisely synthesized via atom transfer radical polymerization (ATRP) technique and named TPE-PLV and TPE-PDV. They possessed typical AIE characteristics and exhibited an increase in concentration-dependent fluorescence intensity. The two AIEgens were pH-responsive and had strong AIE-related emission in acidic solution. Importantly, AIEgens can enter the living cells by ATP dependent endocytosis, then light them up. The interactions between the AIEgens and living human hepatocarcinoma (HepG2) cells revealed that the internalization process of TPE-PLV and TPE-PDV was both chiral-dependent and pH-responsive. This novel strategy for synthesizing poly(amino acid)s functionalized AIEgens could inspire the development of promising fluorescent materials with chirality.

Ce3+-induced Fluorescence Amplification of Copper Nanoclusters Based on Aggregation-induced Emission for Specific Sensing 2,6-pyridine Dicarboxylic Acid

A straightforward, cost-effective and biocompatible reduction approach was applied to fabricate soluble but non-luminous glutathione-stabilized copper nanocluster (GSH-CuNCs). Surprisingly, as high as 1 × 10³ times fluorescence enhancement was acquired when Ce³⁺ was injected at an extremely low concentration of only 18 µM. Ce³⁺ outperformed other rare-earth metal ions in terms of inducing fluorescence amplification of the non-luminous GSH-CuNCs. Furthermore, Ce³⁺ was employed as inducer for aggregation-induce emission (AIE) effect as well as reactant to coordinate with target of 2,6-pyridine dicarboxylic acid (DPA) due to the stronger coordination ability between Ce³⁺ and DPA than that of Ce³⁺ and GSH. As a result, the Ce³⁺/GSH-CuNCs ensemble was developed as a novel sensor to detect DPA in the "on-off" mode. When DPA was introduced into the sensor, Ce³⁺ failed to interact with GSH and detached from the surface of GSH-CuNCs, leading to fluorescence quenching. In addition, static quenching process and internal filtration effect (IFE) between Ce³⁺/GSH-CuNCs and DPA were also responsible for fluorescence quenching effect. A good linear relationship was obtained from 0.3 µM to 18 µM, with a limit of detection (LOD) of 0.19 µM. The as-proposed probe displayed high specificity to DPA and provided a simple, fast rapid and cheap method for construction this type of ensemble sensors to detect other targets.

Ce4+/Ce3+ as the switch of AIE-copper nanoclusters for highly selective detection of ascorbic acid in soft drinks

An ultrasimple "turn-on" sensor for indirectly detecting ascorbic acid (AA) was prepared using N-acetyl-L-cysteine stabilized copper nanoclusters (NAC-CuNCs) via the AIE (aggregation-induced emission) effect controlled by Ce4+/Ce3+ redox reaction. This sensor fully utilizes the different properties of Ce4+ and Ce3+. Non-emissive NAC-CuNCs were synthesized by a facile reduction method. NAC-CuNCs easily aggregate in the presence of Ce3+ due to AIE, resulting in fluorescence enhancement. However, this phenomenon cannot be observed in the presence of Ce4+. Ce4+ possesses strong oxidizing ability and produces Ce3+ by reacting with AA via a redox reaction, followed by switching on the luminescence of NAC-CuNCs. Moreover, the fluorescence intensity (FI) of NAC-CuNCs increases with the concentration of AA in the range of 4-60 µM, with the limit of detection (LOD) as low as 0.26 µM. This probe with excellent sensitivity and selectivity was successfully used in the determination of AA in soft drinks.

Aggregation-induced emission fluorescent probes for lipid droplets-specific bioimaging of cells and atherosclerosis plaques

Visualizing lipid droplets (LDs) using fluorescence imaging is highly desirable for the diagnosis and treatment of atherosclerotic heart diseases. However, the imaging performance of the current commercial lipid probes is unsatisfactory. In this study, we prepared two probes (TTM and MeO-TTM) with aggregation-induced emission (AIE) properties for LD imaging with efficiency. Interestingly, TTM and MeO-TTM showed low emissions in H₂O but their emissions were significantly increased in oil. Moreover, TTM and MeO-TTM showed great biocompatibility and intracellular LDs would be specifically illuminated by these probes with good resistance to photobleaching. In addition, TTM and MeO-TTM also exhibited great imaging performance in studying the spatial distribution of LDs in mouse atherosclerotic plaques. This work not only provides a simple tool for studying atherosclerosis but also hopes to enhance the development of fluorescent probes for LDs-specific imaging applications.

Preparation and dynamic color-changing study of fluorescent polymer nanoparticles for individualized and customized anti-counterfeiting application

Preparing new fluorescent materials for individualized and customized anti-counterfeiting applications to meet needs from the rapid development of e-commerce is of great significance. This paper reports the preparation of dynamic color-changing fluorescent polymer nanoparticles (PNPs) by constructing a fluorescence resonance energy transfer (FRET) pair between aggregation-induced emission (AIE) structures and photochromic structures. At first, methyl methacrylate (MMA) was used as the main monomer and tetraphenylethylene (TPE, a typical AIE structure) modified methacrylate (TPE-MA) and photochromic spiropyran (SP) modified methacrylate (SP-MA) as minor monomers were copolymerized to obtain the ternary copolymer PMMA-TPE-SP. Then, two types of PNPs based on this terpolymer was prepared via the reprecipitation method, with and without the addition of an amphiphilic polymer as the surfactant. The photophysical study shows that the fluorescence color of PNPs dynamically changes from blue to light violet and finally to red under UV light irradiation, a process that can be reversed under visible light. The PNPs were alternately irradiated with UV light and visible light for 10 cycles, which proved their good photoswitching reproducibility. The PNPs prepared with addition of surfactant were found to have stronger fluorescence and better stability. Finally, the photochromic fluorescent inks were prepared based on these PNPs. Several anti-counterfeiting scenarios and modes were designed, exhibiting excellent photochromic behavior on cellulose paper, even after 120 days of long-term storage. With simple equipment, desirable anti-counterfeiting effects with dynamic fluorescence color changing was achieved. This study demonstrated a promising hard-to-imitate anti-counterfeiting encryption strategy, which can achieve multiple outputs with simple operation and can be personalized and customized as needed.

Construction of nanohybrid Tb@CDs/GSH-CuNCs as a ratiometric probe to detect phosphate anion based on aggregation-induced emission and FRET mechanism

The simple preparation of a nanohybrid of terbium-doped carbon dots/glutathione-capped copper nanoclusters (Tb@CDs/GSH-CuNCs) was for the first time developed for ratiometric detection of phosphate anion (Pi). Blue-emission of Tb@CDs can trigger non-luminescence of GSH-CuNCs for aggregation-induced emission (AIE) performance due to the strong reserved coordination capacity of Tb3+. Thus, Tb@CDs/GSH-CuNCs rapidly generated dual-emission signals at 630 nm and 545 nm by directly mixing the two individual materials via the AIE effect, alongside fluorescence resonance energy transfer (FRET) process. However, by the introduction of Pi, both AIE and FRET processes were blocked because of the stronger binding affinity of Tb3+ and Pi than that of Tb3+ and -COOH on Tb@CDs, thus realizing successful ratiometric detection of Pi. The linear concentration range was 0-16 μM, with the limit of detection (LOD) of 0.32 μM. The proposed method provided new ideas for designing nanohybrid of CDs and nanoclusters (MNCs) as ratiometric fluorescent probes for analytical applications.

Tailoring near-infrared amyloid-β probes with high-affinity and low background based on CN and amphipathic regulatory strategies and in vivo imaging of AD mice

Amyloid-β (Aβ) species (Aβ fibrils and Aβ plaques), as one of the typical pathological markers of Alzheimer's disease (AD), plays a crucial role in AD diagnosis. Currently, some near-infrared I (NIR I) Aβ probes have been reported in AD diagnosis. However, they still face challenges such as strong background interference and the lack of effective probe design. In this study, we propose molecular design strategy that incorporates CN group and amphiphilic modulation to synthesize a series of amphiphilic NIR I Aβ probes, surpassing the commercial probe ThT and ThS. Theoretical calculations indicate that these probes exhibit stronger interaction with amino acid residues in the cavities of Aβ. Notably, the probes containing CN group display the ability of binding two distinct sites of Aβ, which dramatically enhanced the affinity to Aβ species. Furthermore, these probes exhibit minimal fluorescence in aqueous solution and offer ultra-high signal-to-noise ratio (SNR) for in vitro labeling, even in wash-free samples. Finally, the optimal probe DM-V2CN-PYC3 was utilized for in vivo imaging of AD mice, demonstrating its rapid penetration through the blood-brain barrier and labelling to Aβ species. Moreover, it enabled long-term monitoring for a duration of 120 min. These results highlight the enhanced affinity and superior performance of the designed NIR I Aβ probe for AD diagnosis. The molecular design strategy of CN and amphiphilic modulation presents a promising avenue for the development Aβ probes with low background in vivo/in vitro imaging for Aβ species.

AIEgen-biomacromolecule conjugates: Visualized delivery and light-controlled theranostic platforms

Biomacromolecules play a critical role in advancing disease diagnosis and treatment. Traditional carriers often lack real-time tracking capabilities, controlled drug release, and may induce adverse effects for delivering biomacromolecules. Aggregation-induced emission luminogens (AIEgens) provide significant advantages in biomacromolecule delivery, enabling real-time fluorescence imaging and reactive oxygen species generation for photodynamic therapy (PDT). This dual functionality allows for the visualization of the biomacromolecule delivery process, providing valuable insights into biodistribution, cellular uptake, and drug-cell interactions. Additionally, the light-responsive nature of AIEgens enables precise spatial-temporal control over cargo release and imaging-guided PDT with minimal side effects. In this perspective, we summarize recent advancements in the use of AIEgens for visualized delivery and light-controlled theranostic applications of biomacromolecules, highlighting their potential to overcome challenges in targeted imaging and precision treatments. Key topics covered include covalent linkage strategies and the biomedical applications of AIEgen-functionalized biomacromolecules, including nucleic acids, proteins, polysaccharides, and lipids. We further highlight AIEgen-functionalized gene therapy and PDT for cancer, peptide transport for disease diagnosis, as well as polysaccharides and lipids delivery in antimicrobial treatments. This perspective concludes by addressing future challenges and opportunities, emphasizing the potential of AIEgen-functionalized biomacromolecules to advance precision theranostics.

Biotin-conjugated Ru(II) complexes with AIE characteristics as mitochondria-targeted photosensitizers for enhancing photodynamic therapy by disrupting cellular redox balance

The potential use of Ru(II) complexes as photosensitizers (PSs) in photodynamic therapy (PDT) has gained significant attention. In comparison with fluorophores with aggregation-caused quenching (ACQ), fluorophores with aggregation-induced emission (AIE) characteristics exhibit sustained fluorescence and dispersibility in aqueous solutions. PSs with AIE characteristics have received much attention in recent years. Herein, we reported two novel biotin-conjugated Ru(II) polypyridyl complexes (Ru1 and Ru2) with AIE characteristics. When exposed to 460 nm (10 mW cm-2) light, Ru1 and Ru2 exhibited outstanding photostability and photocatalytic activity. Ru1 and Ru2 could efficiently generate singlet oxygen and induce pUC19 DNA photolysis when exposed to 460 nm light. Interestingly, both Ru1 and Ru2 also functioned as catalysts for NADH oxidation when exposed to 460 nm light. The presence of biotin fragments in Ru1 and Ru2 enhanced the specific uptake of these complexes by tumor cells. Both complexes showed minimal toxicity to selected cells in the dark. Nevertheless, the phototoxicity of both complexes significantly increased upon 460 nm light irradiation for 15 min. Further experiments revealed that Ru2 primarily accumulated in mitochondria and might bind to mitochondrial DNA. Under 460 nm light irradiation, Ru2 induced the generation of reactive oxygen species (ROS) and NADH depletion disrupting intracellular redox homeostasis in A549 cells, activating the mitochondrial apoptosis pathway resulting in up-regulation of apoptotic marker caspase-3, effectively damaged A549 cell DNA and arrested A549 cell cycle in the S phase. In vivo anti-tumor experiments were conducted to assess the effects of Ru2 on tumor growth in A549 tumor-bearing mice. The results showed that Ru2 effectively inhibited tumor growth under 460 nm light irradiation conditions. These findings indicate that Ru2 has great potential as a targeted photosensitizer for mitochondrial targeting imaging and photodynamic therapy of tumors.