Synchronously Sensitive Immunoassay and Efficient Inactivation of Living Zika Virus via DNAzyme Catalytic Amplification and In Situ Aggregation-Induced Emission Photosensitizer Generation.

Sensitive identification and effective inactivation of the virus are paramount for the early diagnosis and treatment of viral infections to prevent the risk of secondary transmission of viruses in the environment. Herein, we developed a novel two-step fluorescence immunoassay using antibody/streptavidin dual-labeled polystyrene nanobeads and biotin-labeled G-quadruplex/hemin DNAzymes with peroxidase-mimicking activity for sensitive quantitation and efficient inactivation of living Zika virus (ZIKV). The dual-labeled nanobeads can specifically bind ZIKV through E protein targeting and simultaneously accumulate DNAzymes, leading to the catalytic oxidation of Amplex Red indicators and generation of intensified aggregation-induced emission fluorescence signals, with a detection limit down to 66.3 PFU/mL and 100% accuracy. Furthermore, robust reactive oxygen species generated in situ by oxidized Amplex Red upon irradiation can completely kill the virus. This sensitive and efficient detection-inactivation integrated system will expand the viral diagnostic tools and reduce the risk of virus transmission in the environment.

Metal-free click and bioorthogonal reactions of aggregation-induced emission probes for lighting up living systems.

In 2002, two transformative research paradigms emerged: 'click chemistry' and 'aggregation-induced emission (AIE),' both leaving significant impacts on early 21st-century academia. Click chemistry, which describes the straightforward and reliable reactions for linking two building blocks, has simplified complex molecular syntheses and functionalization, propelling advancements in polymer, material, and life science. In particular, nontoxic, metal-free click reactions involving abiotic functional groups have matured into bioorthogonal reactions. These are organic ligations capable of selective and efficient operations even in congested living systems, therefore enabling in vitro to in vivo biomolecular labelling. Concurrently, AIE, a fluorogenic phenomenon of twisted π-conjugated compounds upon aggregation, has offered profound insight into solid-state photophysics and promoted the creation of aggregate materials. The inherent fluorogenicity and aggregate-emission properties of AIE luminogens have found extensive application in biological imaging, characterized by their high-contrast and photostable fluorescent signals. As such, the convergence of these two domains to yield efficient labelling with excellent fluorescence images is an anticipated progression in recent life science research. In this review, we intend to showcase the synergetic applications of AIE probes and metal-free click or bioorthogonal reactions, highlighting both the achievements and the unexplored avenues in this promising field.

Aggregation-Induced Emission-Based Chemiluminescence Systems in Biochemical Analysis and Disease Theranostics.

Chemiluminescence (CL) is of great significance in biochemical analysis and imaging due to its high sensitivity and lack of need for external excitation. In this review, we summarized the recent progress of AIE-based CL systems, including their working mechanisms and applications in biochemical analysis, bioimaging, and disease diagnosis and treatment. In ion and molecular detection, CL shows high selectivity and high sensitivity, especially in the detection of dynamic reactive oxygen species (ROS). Further, the integrated NIR-CL single-molecule system and nanostructural CL platform harnessing CL resonance energy transfer (CRET) have remarkable advantages in long-term imaging with superior capability in penetrating deep tissue depth and high signal-to-noise ratio, and are promising in the applications of in vivo imaging and image-guided disease therapy. Finally, we summarized the shortcomings of the existing AIE-CL system and provided our perspective on the possible ways to develop more powerful CL systems in the future. It can be highly expected that these promoted CL systems will play bigger roles in biochemical analysis and disease theranostics.

Co-aggregation as A Simple Strategy for Preparing Fluorogenic Tetrazine Probes with On-Demand Fluorogen Selection.

Life science has progressed with applications of fluorescent probes-fluorophores linked to functional units responding to biological events. To meet the varied demands across experiments, simple organic reactions to connect fluorophores and functional units have been developed, enabling the on-demand selection of fluorophore-functional unit combinations. However, organic synthesis requires professional equipment and skills, standing as a daunting task for life scientists. In this study, we present a simple, fast, and convenient strategy for probe preparation: co-aggregation of hydrophobic molecules. We focused on tetrazine-a difficult-to-prepare yet useful functional unit that provides effective bioorthogonal reactivity and strong fluorogenicity. Simply mixing the tetrazine molecules and aggregation-induced emission (AIE) luminogens in water, co-aggregation is induced, and the emission of AIE luminogens is quenched. Subsequent click reaction bioorthogonally turns on the emission, identifying these coaggregates as fluorogenic probes. Thanks to this bioorthogonal fluorogenicity, we established a new time-gated fluorescence bioimaging technique to distinguish overlapping emission signals, enabling multi-organelle imaging with two same-color fluorophores. Our study showcases the potential of this co-aggregation method for the on-demand preparation of fluorescent probes as well as protocols and molecular design principles in this approach, offering an effective solution to evolving needs in life science research.

Recent advances in aggregation-induced emission luminogens in photoacoustic imaging.

Photoacoustic imaging (PAI) is a rapidly emerging modality in biomedical research with the advantages of noncontact operation, high optical resolution, and deep penetration. Great efforts and progress in the development of PAI agents with improved imaging resolution and sensitivity have been made over the past 2 decades. Among them, organic agents are the most promising candidates for preclinical/clinical applications due to their outstanding in vivo properties and facile biofunctionalities. Motivated by the unique properties of aggregation-induced emission (AIE) luminogens (AIEgens), various optical probes have been developed for bioanalyte detection, multimodal bioimaging, photodynamic/photothermal therapy, and imaging-guided therapeutics. In particular, AIE-active contrast agents have been demonstrated in PAI applications with excellent performance in imaging resolution and tissue permeability in vivo. This paper presents a brief overview of recent progress in AIE-based agents in the field of photoacoustic imaging. In particular, we focus on the basic concepts, data sorting and comparison, developing trends, and perspectives of photoacoustic imaging. Through numerous typical examples, the way each system realizes the desired photoacoustic performance in various biomedical applications is clearly illustrated. We believe that AIE-based PAI agents would be promising multifunctional theranostic platforms in clinical fields and will facilitate significant advancements in this research topic.

Cinnamaldehyde Resist Salmonella Typhimurium Adhesion by Inhibiting Type I Fimbriae.

Salmonella Typhimurium (S. Typhimurium), a common foodborne pathogen, severely harms the public and food security. Type I fimbriae (T1F) of S. Typhimurium, plays a crucial role in the pathogenic processes; it mediates the adhesion of bacteria to the mannose receptor on the host cell, assists the bacteria to invade the host cell, and triggers an inflammatory response. Cinnamaldehyde is the main ingredient in cinnamon essential oil. In this study, cinnamaldehyde was demonstrated to inhibit the expression of T1F by hemagglutination inhibition test, transmission electron microscopy, and biofilms. The mechanism of cinnamaldehyde action was studied by proteomics technology, PCR and Western blotting. The results showed that cinnamaldehyde can inhibit T1F in S. typhimurium without the growth of bacteria, by regulating the level of expression and transcription of fimA, fimZ, fimY, fimH and fimW. Proteomics results showed that cinnamaldehyde downregulated the subunits and regulators of T1F. In addition, the invasion assays proved that cinnamaldehyde can indeed reduce the ability of S. typhimurium to adhere to cells. The results of animal experiments showed that the colonization in the intestinal tract and the expression levels of inflammatory cytokine were significantly decreased, and the intestinal mucosal immune factors MUC1 and MUC2 were increased under cinnamaldehyde treatment. Therefore, cinnamaldehyde may be a potential drug to target T1F to treat Salmonella infections.

Functionalization of Silk by AIEgens through Facile Bioconjugation: Full-Color Fluorescence and Long-Term Bioimaging.

Silkworm silk is a promising natural biopolymer for textile and biomedical applications for its remarkable flexibility, excellent biocompatibility and controllable biodegradability. The functionalization of silks makes them more versatile for flexible displays and visible bioscaffolds. However, fluorescent silks are normally fabricated through unstable physical absorption or complicated chemical reactions under harsh conditions. Herein, we developed a simple strategy for preparing fluorescent silks. Five aggregation-induced emission luminogens (AIEgens) with activated alkynes were synthesized by rational molecular design, and then reacted with silk fibers through facile metal-free click bioconjugation. The resulting conjugates show bright full-color emissions and high stability. A white light-emitting silk was fabricated by simultaneous bioconjugation with red-, green- and blue-emissive AIEgens. The red-emissive AIEgen-functionalized silks were successfully applied for long-term cell tracking and two-photon bioimaging, demonstrating great potential for tissue engineering and bioscaffold monitoring.

Multicolor Tunable Polymeric Nanoparticle from the Tetraphenylethylene Cage for Temperature Sensing in Living Cells.

It is meaningful but challenging to develop a fluorescent probe for temperature sensing in living cells because it should possess the features of good cytocompatibility, easy read out, and high resolution. Herein, we successfully synthesized emissive star-like cage-based organic temperature-sensitive polymers that can assemble into nanoparticles in aqueous solution. The obtained nanoparticle can be easily tuned to full-color emission (including white light emission) with a temperature resolution of at least 0.5 °C by encapsulating different doses of guest dyes ((4-dimethylamino-2'-butoxychalcone (DMBC) and Nile Red (NR)) through a cascade Förster resonance energy transfer (FRET) effect. Moreover, the white light emission polymeric hybrid nanoparticles exhibit reversible stimuli response toward temperature and can be used as probes for temperature sensing in live cells through their fluorescent color variation between white and orange emission with good cytocompatibility.

Phage-Guided Targeting, Discriminative Imaging, and Synergistic Killing of Bacteria by AIE Bioconjugates.

New agents with particular specificity toward targeted bacteria and superefficacy in antibacterial activity are urgently needed in facing the crisis of worldwide antibiotic resistance. Herein, a novel strategy by equipping bacteriophage (PAP) with photodynamic inactivation (PDI)-active AIEgens (luminogens with aggregation-induced emission property) was presented to generate a type of AIE-PAP bioconjugate with superior capability for both targeted imaging and synergistic killing of certain species of bacteria. The targeting ability inherited from the bacteriophage enabled the bioconjugates to specifically recognize the host bacteria with preserved infection activity of phage itself. Meanwhile, the AIE characteristic empowered them a monitoring functionality, and the real-time tracking of their interactions with targets was therefore realized via convenient fluorescence imaging. More importantly, the PDI-active AIEgens could serve as powerful in situ photosensitizers producing high-efficiency reactive oxygen species (ROS) under white light irradiation. As a result, selective targeting and synergistic killing of both antibiotic-sensitive and multi-drug-resistant (MDR) bacteria were successfully achieved in in vitro and in vivo antibacterial tests with excellent biocompatibility. This novel AIE-phage integrated strategy would diversify the existing pool of antibacterial agents and inspire the development of promising drug candidates in the future.

Transition-metal-free cascade benzannulations for synthesizing 2-hydroxybenzophenones.

A set of cascade benzannulations of readily accessible chromone-3-carboxaldehydes and γ-nitroaldehydes for synthesizing biologically relevant 2-hydroxybenzophenones has been developed. The cascade was found to provide a transition-metal-free strategy for synthesizing 2-hydroxybenzophenones in acceptable yields (up to 57%).

Direct Visualization and Quantification of Maternal Transfer of Silver Nanoparticles in Zooplankton.

The immense application of silver nanoparticles (AgNPs) in biomedical fields is likely to increase the exposure of humans. However, little is known about whether these nanoparticles can be maternally transferred, especially regarding their biodistribution in the younger generation, maternal transfer efficiency, and toxic effects. In the present study, maternal transfer of AgNPs in model zooplankton (Daphnia magna) was for the first time visualized and quantified. We found that AgNPs were transferred from mother to offspring and mainly accumulated in the lipids due to the strong colocalization with lipid droplets, which were the major energy sources of Daphnia embryos. In contrast, Ag+ was irregularly distributed in different sites, probably due to the mobility and reactivity of Ag+. The maternal transfer efficiency quantified by the radiolabeling methodology was 2.37 ± 0.25 and 6.05 ± 0.89% for 110mAgNPs and 110mAg, respectively. Furthermore, AgNPs and Ag+ significantly inhibited the reproduction capability of F0 and F1 generations, but such maternal toxic effect inhibition was only found within the first two broods of F0 and F1 generations. Our bioimaging findings demonstrated that AgNPs could be maternally transferred to the next generation; thus, it is critical to produce AgNPs with lower toxic effects, higher delivery efficacy, and more precise targeting.

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.

A Conjugated Polymeric Supramolecular Network with Aggregation-Induced Emission Enhancement: An Efficient Light-Harvesting System with an Ultrahigh Antenna Effect.

Superior artificial light-harvesting systems (ALHSs) require exceptional capacity in harvesting light and transferring energy. In this work, we report a novel strategy to build ALHSs with an unprecedented antenna effect (35.9 in solution and 90.4 in solid film). The ALHSs made use of a conjugated polymeric supramolecular network (CPSN), a crosslinked network obtained from the self-assembly of a pillar[5]arene-based conjugated polymeric host (CPH) and conjugated ditopic guests (Gs). The excellent performance of the CPSN could be attributed to the following factors: 1) The "molecular wire effect" of the conjugated polymeric structure, 2) aggregation-induced enhanced emission (AEE) moieties in the CPH backbone, and 3) high capacity of donor-acceptor energy transfer, and 4) crosslinked structures triggered by the host-guest binding between Gs and CPH. Moreover, the emission of the CPSN could be tuned by using different Gs or varying the host/guest ratio, thus reaching a 96 % sRGB area.

Multifunctional AuI -based AIEgens: Manipulating Molecular Structures and Boosting Specific Cancer Cell Imaging and Theranostics.

Gold(I) N-heterocyclic carbene (AuI -NHC) complexes have emerged as potential anticancer agents owing to their high cytotoxicity and stability. Integration of their above unique functions with customized aggregation-induced emission (AIE) luminogens to achieve specific bioimaging and efficient theranostics to cancer is highly desirable but is rarely studied. Now, a series of novel AuI -NHC compounds were developed with AIE characteristics. A complex with a PPh3 ligand was selected out as it could achieve both prominent specific imaging of various cancer cells and efficient inhibition of their growth with negligible toxic effects on normal cells due to the targeting binding and strong inhibition towards thioredoxin reductase. This complex could also act as a powerful radiosensitizer to boost the anticancer efficacy with performance superior to that of popularly used auranofin. It holds great potential as a specific and effective theranostic drug in cancer diagnosis and precise therapy.

Dual-Color Emissive AIEgen for Specific and Label-Free Double-Stranded DNA Recognition and Single-Nucleotide Polymorphisms Detection.

Simple, rapid, and sensitive assays of DNA sequence hold great importance in genetic analysis, clinical diagnosis, and molecular biology research. Most current methods for DNA detection, based on the complementary base pairing, require hybridization with intricately modified single-stranded DNA (ssDNA) probes or analytes. Herein, we have developed a powerful molecule with aggregation-induced emission (AIE) characteristic, namely, TPBT, which can specifically recognize double-stranded DNA (dsDNA) by emitting out a unique dual-color fluorescent signal of red (∼640 nm) and green (∼537 nm). The red-color emission at around 640 nm is observed when TPBT binds with dsDNA, ssDNA, proteins, and other polyanionic analytes. However, the green emission at around 537 nm is demonstrated to be the exclusive response of TPBT to dsDNA, which is closely related to the conformational change of TPBT upon groove binding. More strikingly, TPBT can distinguish single-nucleotide polymorphisms (SNPs) in a dsDNA sequence and detect the DNA damage suffered from UV light with ultrahigh sensitivity and specificity. This label-free, AIEgen-based dsDNA assay method is facile, robust, and universal, which will lead to major advances in genomic and disease diagnosis.

Three-Component Regio- and Stereoselective Polymerizations toward Functional Chalcogen-Rich Polymers with AIE-Activities.

Polymers containing rich chalcogen elements are rarely reported due to the lack of facile synthesis methods. Herein, a novel multicomponent polymerization route toward chalcogen-rich polymers was introduced. A series of poly(vinyl sulfones) (PVSs) were synthesized at room temperature using readily prepared monomers. PVSs were generated with high regio- and stereo-selectivity in high yields (up to 92.3%). Rich chalcogen elements endowed PVSs with distingctive multifunctionalities. The PVSs possessed good solubility and film-forming ability. Their thin films exhibited outstanding refractive indices up to 1.8062 at 550.0 nm together with good optical transparency in the visible region. Thin films of some polymers can also be fabricated into well-resolved fluorescent photopatterns by photolithography. Thanks to the unique redox properties of selenium, postmodification by oxidation reaction of P1a/2/3a successfully eliminates the caused heavy atom effect and endow resulting polymers with novel functionality as fluorescent bioprobes for cellular imaging.

Functionalized Acrylonitriles with Aggregation-Induced Emission: Structure Tuning by Simple Reaction-Condition Variation, Efficient Red Emission, and Two-Photon Bioimaging.

Acrylonitriles with aggregation-induced emission (AIE) characteristics have been found to show promising applications in two-photon biomedical imaging. Generally, elaborate synthetic efforts are required to achieve different acrylonitriles with distinct functionalities. In this work, we first reported the synthesis of two different group-functionalized AIE-active acrylonitriles (TPAT-AN-XF and 2TPAT-AN) obtained simply by mixing the same reactants at different temperatures using a facile and transition metal-free synthetic method. These two AIE luminogens (AIEgens) exhibit unique properties such as bright red emission in the solid state, large Stokes shift, and large two-photon absorption cross section. Water-soluble nanoparticles (NPs) of 2TPAT-AN were prepared by a nanoprecipitation method. In vitro imaging data show that 2TPAT-AN NPs can selectively stain lysosome in live cells. Besides one-photon imaging, remarkable two-photon imaging of live tumor tissues can be achieved with high resolution and deep tissue penetration. 2TPAT-AN NPs show high biocompatibility and are successfully utilized in in vivo long-term imaging of mouse tumors with a high signal-to-noise ratio. Thus, the present work is anticipated to shed light on the preparation of a library of AIE-active functionalized acrylonitriles with intriguing properties for biomedical applications.

An asymmetric iminium ion catalysis-enabled cascade cycloaddition reaction of chromone-oxindole synthons with enals: construction of a spirooxindole-hexahydroxanthone framework.

We report the first asymmetric iminium ion catalysis-enabled cascade cycloaddition reaction of bifunctional chromone-oxindole synthons and α,ß-unsaturated aldehydes. This allowed one quaternary and four tertiary contiguous stereogenic centers to be constructed in a single operation. A range of spirooxindole-hexahydroxanthone molecules are obtained with up to 62% yield, >20 : 1 dr and >99% ee. This reaction has not only provided a new approach for constructing hexahydroxanthone-fused scaffolds by utilizing asymmetric iminium ion catalysis, but also advanced the chemistry of diversity-oriented synthesis based on bifunctional chromone synthons.

Differentiating Silver Nanoparticles and Ions in Medaka Larvae by Coupling Two Aggregation-Induced Emission Fluorophores.

Although numerous studies have been conducted on the toxicity and biodistribution of AgNPs and corresponding ionic counterparts, it is still debatable whether the toxicity originates from the accumulation of particles within specific organs or is mediated by the dissolved Ag ions. To gain a better insight into the toxic mechanisms of AgNPs, two aggregation-induced emission fluorogens (AIEgens; AIEgens-coated AgNPs and a fluorogenic Ag+ sensor) were employed for the in situ visualization and quantitative analysis of distribution patterns of AIE-AgNPs and corresponding Ag ions in different organs of medaka larvae. The 96 h LC50 of AIEgens-coated AgNPs (AIE-AgNPs) was 10-20 mg/L, which was much higher than that of the citrate-coated AgNPs (Cit-AgNPs, 2.39-3.24 mg/L) and AgNO3 (0.23 mg/L), suggesting that the AIE-AgNPs were much more biocompability than Cit-AgNPs or AgNO3. The LC50 of AgNO3 was approximately 10% of the LC50 of Cit-AgNPs, which was comparable to the percentage of Ag+ released from Cit-AgNPs. The novel AIE method for the first time simultaneously analyzed the quantitative distribution patterns of AIE-AgNPs and corresponding Ag ions in different organs of medaka larvae. AIE-AgNPs and Ag ions showed distinct distribution patterns, in which AIE-AgNPs were concentrated in intestine and liver, accounting for 53.4% and 32.1% of the total AIE-AgNPs accumulated in medaka larvae, respectively. In contrast, Ag ions were accumulated mainly (92.5%) in the intestine of medaka larvae. The toxicity of AgNPs toward medaka larvae was attributed mainly to the released Ag ions which could potentially disrupt the absorptive capacity of the intestinal epithelium and induce digestive dysfunction. Our study provided a new technique for simultaneous monitoring of the AgNPs and corresponding Ag ions in the biological systems.

Multiple yet Controllable Photoswitching in a Single AIEgen System.

Seeking new methods to obtain elaborate artificial on-demand photoswitching with multiple functionalities remains challenging. Most of the systems reported so far possess only one specific function and their nonemissive nature in the aggregated state inevitably limit their applications. Herein, a tailored cyanostilbene-based molecule with aggregation-induced emission characteristic was synthesized and was found to exhibit efficient, multiple and controllable photoresponsive behaviors under different conditions. Specifically, three different reactions were involved: (i) reversible Z/E isomerization under room light and thermal treatment in CH3CN, (ii) UV-induced photocyclization with a concomitant dramatic fluorescence enhancement, and (iii) regio- and stereoselective photodimerization in aqueous medium with microcrystal formation. Experimental and theoretical analyses gave visible insights and detailed mechanisms of the photoreaction processes. Fluorescent 2D photopattern with enhanced signal-to-background ratio was fabricated based on the controllable "turn-on" and "turn-off" photobehaviors in different states. The present study thus paves an easy yet efficient way to construct smart multiphotochromes for unique applications.