Aggregation-induced Emission Fluorogen Research Articles

Preparation of AIEgen-based near-infrared afterglow luminescence nanoprobes for tumor imaging and image-guided tumor resection.

Fluorescence imaging represents a vital tool in modern biology, oncology and biomedical applications. Afterglow luminescence (AGL), which circumvents the light scattering and tissue autofluorescence interference associated with real-time excitation source, shows remarkably increased imaging sensitivity and depth. Here we present a protocol for the design and synthesis of AGL nanoprobes with an aggregation-induced emission (AIE) effect to simultaneously red shift and amplify the afterglow signal for tumor imaging and image-guided tumor resection. The nanoprobe (AGL AIE dot) is composed of an enol ether format of Schaap's agent and a near-infrared AIE fluorogen (AIEgen) (tetraphenylethylene-phenyl-dicyanomethylene-4H-chromene, TPE-Ph-DCM) to suppress the nonradiative dissipation pathway. Pre-irradiating AGL AIE dots with white light could generate singlet oxygen to convert Schaap's agent to its 1,2-dioxetane format, thus initializing the AGL process. With the aid of AIEgen, the AGL shows simultaneously red shifted emission maximum (from ~540 nm to ~625 nm) and enhanced intensity (by 3.2-fold), facilitating better signal-to-background ratio, imaging sensitivity and depth. Intriguingly, the activated AGL can last for over 10 days. Compared with conventional approaches, our method provides a new solution to concurrently red shift and amplify afterglow signals for better in vivo imaging outcomes. The preparation of AGL AIE dots takes ~2 days, the in vitro characterization takes ~10 days (less than 1 day if not involving afterglow kinetic profile study) and the tumor imaging and image-guided tumor resection takes ~7 days. These procedures can be easily reproduced and amended after standard laboratory training in chemical synthesis and animal handling.

AIE fluorescent nanozyme-based dual-mode biosensor for analysis of the bioactive component hypoxanthine in meat products

The development of facile, low-cost reliable, and precise onsite assays for the bioactive component hypoxanthine (Hx) in meat products is significant for safeguarding food safety and public health. Herein, we proposed a smartphone-assissted aggregation-induced emission (AIE) fluorogen tetraphenylethene (TPE)-incorporated amorphous Fe-doped phosphotungstates (Fe-Phos@TPE) nanozyme-based ratiometric fluorescence-colorimetric dual-mode biosensor for achieving the onsite visual detection of Hx. When the Hx existed, xanthine oxidase (XOD) catalyzed Hx into H2O2 to be further catalyzed into •OH by the prominent peroxidase activity of Fe-Phos@TPE at pH = 6.5, resulting in the oxidization of nonfluorescent o-phenylenediamine (OPD, naked-eye colorless) to be yellow fluorescent emissive 2,3-diaminophenazine (DAP, naked-eye dark yellow) at 550 nm as well as the intrinsic blue fluorescence of Fe-Phos@TPE at 440 nm to be decreased via inner-filter effect (IFE) action, thereby realizing a multi-enzyme cascade catalytic reaction at near-neutral pH to overcome the traditional acidity dependence-induced time-consuming and low sensitivity troublesome.

Design of synthetic peptide-based fluorescence probes for turn-on detection of hyaluronan

Herein, we designed and examined a series of fluorescent peptide-based probes for turn-on detection of hyaluronan (HA), a member of the glycosaminoglycan family. We utilized two kinds of synthetic HA-binding peptides as the binding unit for HA, and each peptide was coupled with three kinds of environment-sensitive fluorophores as the signaling unit. From the examination of the peptides, fluorophores, and the position and number of fluorophore modification, we found that X7 peptide (RYPISRPRKR) labelled with an aggregation-induced emission (AIE) fluorogen, tetraphenylethene (TPE), at the N-terminal (named TPE-X7) did function as a light-up probe for HA. The response of TPE-X7 was highly selective to higher molecular weight HA in comparison with lower ones, having the possible potential for the analysis of HA size. TPE-X7 was also applicable to the quantification of HA in synovial fluids.Graphical abstract

Advancements in molecular disassembly of optical probes: a paradigm shift in sensing, bioimaging, and therapeutics.

The majority of self-assembled fluorescent dyes suffer from aggregation-caused quenching (ACQ), which detrimentally affects their diagnostic and therapeutic effectiveness. While aggregation-induced emission (AIE) active dyes offer a promising solution to overcome this limitation, they may face significant challenges as the intracellular environment often prevents aggregation, leading to disassembly and posing challenges for AIE fluorogens. Recent progress in signal amplification through the disassembly of ACQ dyes has opened new avenues for creating ultrasensitive optical sensors and enhancing phototherapeutic outcomes. These advances are well-aligned with cutting-edge technologies such as single-molecule microscopy and targeted molecular therapies. This work explores the concept of disaggregation-induced emission (DIE), showcasing the revolutionary capabilities of DIE-based dyes from their design to their application in sensing, bioimaging, disease monitoring, and treatment in both cellular and animal models. Our objective is to provide an in-depth comparison of aggregation versus disaggregation mechanisms, aiming to stimulate further advancements in the design and utilization of ACQ fluorescent dyes through DIE technology. This initiative is poised to catalyze scientific progress across a broad spectrum of disciplines.

Fine-tuning bromide AIE probes for Hg2+ detection in mitochondria with wash-free staining

Mercury ions (Hg2+) primarily target mitochondria in the cells. Therefore, the development of novel probes that specifically target mitochondria in the presence of Hg2+ is of immense importance. Most previously reported probes that utilize the softness of S, Te, O, and/or N atoms for Hg2+ binding often face problems such as fluorescence quenching and off-target signals. In this study, bromide-hydrocarbon pyridinium salts were designed to target the mitochondria and chelate Hg2+ via Hg–Br coordination bonds. As a prototype, four aggregation-induced emission (AIE) fluorogens, namely TPP-Br, TPP-Cl, R1, and R2, with a similar D-π-A structure but slight differences in their halogen substituents, were designed. Among them, only TPP-Br achieved the highly selective and sensitive detection of Hg2+ by triggering its AIE properties, resulting in remarkable emission enhancement (80-fold), colorimetry, and the Tyndall effect. TPP-Br exhibited high selectivity and sensitivity to Hg2+ with a detection limit of 0.35 μM, rapid response time (<10 s), and large Stokes shift of 185 nm. Their interaction modes were studied using a combination of 1H nuclear magnetic resonance spectroscopy, scanning electron microscopy, fluorescent lifetime decay, and theoretical calculations. TPP-Br exhibited a low emission background in cells, whereas in the presence of Hg2+, mitochondria were lit up with wash-free staining. This study provides a powerful tool for accurately diagnosing mercury poisoning–related diseases in mitochondria.

Infiltration of freshwater food chain by nanoplastics: An examination of trophic transfer and biological impact

The contamination of freshwater by nanoplastics (NPs) poses a significant threat to various organisms. However, the influence of food factors on the NPs toxicity and the associated risks to water safety remains poorly understood. In this study, we employed highly fluorescent NPs incorporating aggregation-induced emission fluorogens to quantify and visualize the interactions of NPs with freshwater phytoplanktonic alga Chlamydomonas reinhardtii and zooplankton Daphnia magna, including the uptake of NPs by algae and daphnids, as well as gut environment responses through both waterborne and foodborne routes. NPs at environmentally relevant concentrations were capable of aggregating and internalizing in planktonic algae, thus permeating the food chain and potentially causing ecological risks. Notably, positively charged NPs exhibited greater infiltration than the negatively charged NPs. Our findings indicated that NPs had a greater tendency to accumulate in Daphnia via the food chain rather than through direct exposure to water. This was attributed to the loss of selectivity, suggesting a potential mechanism for NP accumulation in aquatic food chains. However, daphnids exposed to NPs through waterborne route exhibited more gut pH acidification, esterase activity, and gut inflammation compared to those exposed via the foodborne route. Moreover, chronic exposure to NPs through waterborne routes significantly disrupted the growth, molting, and reproduction of Daphnia compared to the foodborne group. These findings provided valuable insights into the complexities of plastic pollution on primary trophic levels in aquatic environments.

Metabolic pathways of methylmercury in rotifer Brachionus plicatilis

Methylmercury (MeHg) readily accumulates in aquatic organisms while transferring and amplifying in the aquatic food chains. This study firstly explores the in vivo accumulation sites and metabolic regulation of MeHg in the rotifer Brachionus plicatilis by aggregation-induced emission fluorogen (AIEgen) and metabolomics. Fluorescent image analysis by AIEgen showed that MeHg in B. plicatilis mainly occured in the ciliary corona, esophagus, mastax, stomach and intestine in the direct absorption group. In the other group, where B. plicatilis were indirectly supplied with MeHg via food intake, the accumulation of MeHg in the rotifer occurred in the ciliary corona, various digestive organs, and the pedal gland. However, the MeHg accumulated in the rotifer is difficult to metabolize outside the body. Metabolomics analysis showed that the significant enrichment of ABC transporters was induced by the direct exposure of rotifers to dissolved MeHg. In contrast, exposure of rotifers to MeHg via food intake appeared to influence carbon, galactose, alanine, aspartate and glutamate metabolisms. Besides, the disturbed biological pathways such as histidine metabolism, beta-alanine metabolism and pantothenate and CoA biosynthesis in rotifers may be associated with L-aspartic acid upregulation in the feeding group. The significant enrichment of ABC transporters and carbon metabolism in rotifers may be related to the accumulation of MeHg in the intestine of rotifers. In both pathways of MeHg exposure, the arginine biosynthesis and metabolism of rotifers were disturbed, which may support the hypothesis that rotifers produce more energy to resist MeHg toxicity. This study provides new insight into the accumulation and toxicity mechanisms of MeHg on marine invertebrates from the macro and micro perspectives.

Water soluble AIEgen-based thermosensitive and antibacterial hydroxypropyl chitin hydrogels for non-invasive visualization and wound healing

Antimicrobial hydrogels containing antibacterial agents have been extensively studied for postoperative infections, wound repair and tissue engineering. However, the abuse of antibiotics has led to the enhancement of bacterial resistance and traditional antibacterial agents are losing their effect. Therefore, fabricating novel and efficient antibacterial hydrogels with enhanced photodynamic antimicrobial activity, good biocompatibility, biodegradability and injectability are highly desirable for clinical application. Herein, a fluorescent and sunlight-triggered synergetic antibacterial thermosensitive hydrogel (red fluorescent hydroxypropyl chitin, redFHPCH) is constructed based on a new water-soluble AIEgen (aggregation-induced emission fluorogen) covalently introduced in hydroxypropyl chitin for non-invasive visualization and wound healing. The thermosensitive redFHPCH solution showing good injectability with fluidity at low temperature was completely transformed into hydrogel under body temperature. The in vitro and in vivo visualization and reactive oxygen species (ROS) generation of the redFHPCH hydrogel are demonstrated clearly because of its excellent AIE fluorescence imaging quality in the red/near-infrared region and superefficient ROS production by sunlight. Moreover, the redFHPCH hydrogel with positively charged quaternary ammonium groups displays a strong synergistic antibacterial effect for healing of infected wound under sunlight irradiation. We believe that this novel strategy can open a new door to explore diversified and multifunctional hydrogels for clinical application.

Stimuli-responsive aggregation-induced emission of molecular probes by electrostatic and hydrophobic interactions: Effect of organic solvent content and application for probing of alkaline phosphatase activity

We suggest that aggregation-induced emission (AIE) molecular probes with single charged/reactive group can exist in the formation of nanostructures but not monomers at extremely low organic solvent content. The nanoaggregates show good dispersivity and emit week emission. Stimuli-responsive assembly of nanoaggregates by electrostatic interactions can turn on the fluorescence, facilitating the design of biosensors with single-charged molecular probes as the AIE fluorogens. To prove the concept, tetraphenylethene-substituted pyridinium salt (TPE-Py) was used as the AIE fluorogen for probing of alkaline phosphatase (ALP) activity with pyrophosphate ion (PPi) as the enzyme substrate. The dynamic light scattering and transmission electron microscope experiments demonstrated that TPE-Py probes existed in aqueous solution at nanometer size and morphology. Stimuli such as the negatively charged PPi, citrate, ATP, ADP, NADP and DNA could trigger the aggregation of the positively charged TPE-Py nanoparticles, thus enhancing the fluorescence via AIE effect. ALP-enzymatic hydrolysis of PPi into two phosphate ions (Pi) limited the aggregation of TPE-Py nanoparticles. The strategy was used for the assay of ALP with a low detection limit (1 U/L) and wide linear range (1–200 U/L). We also investigated the effect of organic solvent content on the AIE process and found that high concentration of organic solvent can prevent the hydrophobic interaction between AIE molecules but show no essential influence on the electrostatic interaction-mediated assembly. The work should be evaluable for understanding AIE phenomenon and developing novel, simple and sensitive biosensors using a molecular probe with single charged/reactive group as the signal reporter.

Phase-Separating Peptides Recruiting Aggregation-Induced Emission Fluorogen for Rapid E. coli Detection.

Rationally designed biomolecular condensates have found applications primarily as drug-delivery systems, thanks to their ability to self-assemble under physico-chemical triggers (such as temperature, pH, or ionic strength) and to concomitantly trap client molecules with exceptionally high efficiency (>99%). However, their potential in (bio)sensing applications remains unexplored. Here, we describe a simple and rapid assay to detect E. coli by combining phase-separating peptide condensates containing a protease recognition site, within which an aggregation-induced emission (AIE)-fluorogen is recruited. The recruited AIE-fluorogen's fluorescence is easily detected with the naked eye when the samples are viewed under UV-A light. In the presence of E. coli, the bacteria's outer membrane protease (OmpT) cleaves the phase-separating peptides at the encoded protease recognition site, resulting in two shorter peptide fragments incapable of liquid-liquid phase separation. As a result, no condensates are formed and the fluorogen remains non-fluorescent. The assay feasibility was first tested with recombinant OmpT reconstituted in detergent micelles and subsequently confirmed with E. coli K-12. In its current format, the assay can detect E. coli K-12 (108 CFU) within 2 h in spiked water samples and 1-10 CFU/mL with the addition of a 6-7 h pre-culture step. In comparison, most commercially available E. coli detection kits can take anywhere from 8 to 24 h to report their results. Optimizing the peptides for OmpT's catalytic activity can significantly improve the detection limit and assay time. Besides detecting E. coli, the assay can be adapted to detect other Gram-negative bacteria as well as proteases having diagnostic relevance.

Selective ingestion and response by Daphnia magna to environmental challenges of microplastics

Our current understandings of the effects of microplastics and nanoplastics (MNPs) on aquatic animals are predominantly based on the single types of plastic particles. In the present study, we employed the highly fluorescent MNPs that incorporated aggregation-induced emission fluorogens and investigated the selective ingestion and response of Daphnia exposed to different types of plastics at environmentally relevant concentrations simultaneously. When daphnids were exposed to a single MNP, D. magna ingested them instantly in significant amounts. However, even low concentrations of algae had a significant negative impact on the MNP uptake. Specifically, algae caused the MPs to pass through the gut faster, reduced acidification and esterase activity, and changed the distribution of MPs in the gut. In addition, we also quantified the influences of size and surface charge on the selectivity of D. magna. The daphnids selectively ingested larger and positively charged plastics. MPs effectively reduced the uptake of NP and increased its gut passage time. Aggregation of positively and negatively charged MNPs also influenced the gut distribution and increased the gut passage time. The positively charged MPs accumulated in the middle and posterior gut, while aggregation of MNPs also increased acidification and esterase activity. These findings provided fundamental knowledge on the selectivity of MNPs and the microenvironmental responses of zooplankton guts.

Background-Quenched Aggregation-Induced Emission through Electrostatic Interactions for the Detection of Poly(ADP-ribose) Polymerase-1 Activity.

Poly(ADP-ribose) polymerase-1 (PARP1) is a potential biomarker and therapeutic target for cancers that can catalyze the poly-ADP-ribosylation of nicotinamide adenine dinucleotide (NAD+) onto the acceptor proteins to form long poly(ADP-ribose) (PAR) polymers. Through integration with aggregation-induced emission (AIE), a background-quenched strategy for the detection of PARP1 activity was designed. In the absence of PARP1, the background signal caused by the electrostatic interactions between quencher-labeled PARP1-specitic DNA and tetraphenylethene-substituted pyridinium salt (TPE-Py, a positively charged AIE fluorogen) was low due to the fluorescence resonance energy transfer effect. After poly-ADP-ribosylation, the TPE-Py fluorogens were recruited by the negatively charged PAR polymers to form larger aggregates through electrostatic interactions, thus enhancing the emission. The detection limit of this method for PARP1 detection was found to be 0.006 U with a linear range of 0.01~2 U. The strategy was used to evaluate the inhibition efficiency of inhibitors and the activity of PARP1 in breast cancer cells with satisfactory results, thus showing great potential for clinical diagnostic and therapeutic monitoring.

A dual “turn-on” biosensor based on AIE effect and FRET for in situ detection of miR-125b biomarker in early Alzheimer's disease

MicroRNA-125b (miR-125b) is highly associated with synaptic dysfunction and tau hyperphosphorylation in the early pathogenesis of Alzheimer's disease (AD), making it a promising biomarker for early AD diagnosis. Hence, there is an urgent need for a reliable sensing platform to assist in situ miR-125b detection. In this work, we report a dual “turn-on” fluorescence biosensor based on the nanocomposite of aggregation-induced emission fluorogen (AIEgen)-labeled oligonucleotide (TPET-DNA) probes immobilized on the surface of cationic dextran modified molybdenum disulfide (TPET-DNA@Dex-MoS2). In the presence of the target, TEPT-DNA can hybridize with miR-125b to form a DNA/RNA duplex, causing TPET-DNA to detach from the surface of Dex-MoS2 that simultaneously activates the dual fluorescence enhancement processes: (1) recovery of TPET-DNA signal and (2) strong fluorescent emission from AIEgen triggered by restriction of the intramolecular rotation. The sensing performance of TPET-DNA@Dex-MoS2 was demonstrated by detecting miR-125b in vitro with good sensitivity at the picomolar level and rapid response (≤1 h) without amplification procedures. Furthermore, our nanoprobes exhibited excellent imaging capabilities to aid real-time monitoring of the endogenous miR-125b in PC12 cells and brain tissues of mice AD model induced by local administration of okadaic acid (OA). The fluorescence signals of the nanoprobes indicated miR-125b was spatially associated with phosphorylated tau protein (p-tau) in vitro and in vivo. Therefore, TPET-DNA@Dex-MoS2 could be a promising tool for in situ and real-time monitoring of the AD-related microRNAs and also provide mechanistic insight into the early prognosis of AD.

The preparation of novel AIE fluorescent microspheres by dispersion polymerization

ABSTRACT An approach to prepare monodisperse polystyrene microspheres with aggregation-induced emission (AIE) characteristics has been developed which shows promising applications in fluorescence-encoding. The micron-sized, monodisperse polystyrene microspheres with AIE molecules were perfectly synthesized by two-stage dispersion polymerization. Fluorescent AIE monomer was synthesized by Suzuki reaction, confirmed by nuclear magnetic resonance (NMR). These AIE fluorogens (AIEgens) exhibited unique properties such as bright green emission in solid state and increased emission in tetrahydrofuran (THF) solution with the increase of water content. The influence of the AIE molecules concentration to microspheres synthesis was well investigated. The reaction conditions were optimized to obtain the functional polystyrene microspheres with a size distribution around 3%. The novel microspheres were characterized by scanning electron microscopy (SEM), confocal fluorescence microscope and flow cytometry. According to these results, two-stage dispersion polymerization was proved to be an efficient pathway for the preparation of AIE fluorescent and functionalized microspheres, which could be used in many biomedical industries.

Methylmercury bioaccumulation in water flea Daphnia carinata by AIEgen

Mercury ion (Hg2+) is a toxic heavy metal ion and Hg2+ is convertible to methylmercury (MeHg) by many aquatic microorganisms, leading to bioaccumulation and biomagnification in aquatic organisms, which can interfere with brain development and function in humans. This study employs a newly developed AIEgen (Aggregation-induced emission fluorogen) to quantify and visualise the process of MeHg bioaccumulation in vivo on the species of water flea Daphnia carinata. Two approaches to MeHg absorption were taken, either by direct incubation in a MeHg solution or by indirect consumption of algae contaminated with MeHg. We analysed the relationship between the ratio of photoluminescence (PL) intensities (I585/I480) and MeHg concentration (CMeHg) and generated a master curve for determining MeHg concentration based on the measurement of PL intensities. Fluorescent image analysis showed the occurrence of MeHg in D. carinata to be mainly in the compound eyes, optic nerve and carapace. This study indicates that MeHg absorption can be quantified and visualised in the body of zooplankton, and the MeHg transfer to zooplankton is more likely through direct exposure than via indirect food intake. The accumulation of MeHg in the eye and the nervous system could be the cause of the high mortality of D. carinata exposed to MeHg in water.

Solid-State Emission and Aggregate Emission of Aroyl- S,N-Ketene Acetals Are Controlled and Tuned by Their Substitution Pattern.

Aroyl-S,N-ketene acetals are a novel highly diverse class of aggregation-induced emission fluorogens (AIEgens) with a plethora of interesting properties. An expanded compound library of more than 110 dyes set the stage for the first qualitative control and tuneability of all aspects of their photophysical properties. The interplay of substituents not only allows tuning and prediction of the emission color, but also of the intensity, and quantum yields both in solids and in the aggregated state; these can be rationalized by scrutinizing intermolecular interactions in the crystalline solid state.

Recent advances in chiral aggregation-induced emission fluorogens

• Chiral AIEgens can identify chiral molecules visually based on color change and precipitation reaction, quantitatively analyze chiral molecules, demonstrating its high selectivity, sensitivity and accuracy in chiral identification. • The CPL asymmetry factor (glum) of chiral AIE fluorogens (AIEgens) can reach 1.42, which is very close to the theoretical value of 2. • The combination of chiral elements and luminescent groups promotes their adoption in the field of organic CPL materials. • We have summarized the recent advances of chiral AIEgens in both chiral molecule recognition and circularly polarized organic light-emitting diode. As a flourishing research field, we believe that a detailed and timely literature collection of this field is highly desirable for the chemistry and material community. Over the past decade, aggregation-induced emission (AIE) molecules have played a pivotal role in bioimaging, anti-microbial, and photodynamic therapy, and have been at the forefront of several disciplines worldwide. When combined with chiral moieties, they can easily collide with dazzling sparks and exhibit exceptional and unique advantages. In the application of chiral recognition and measurement of enantiomeric excess, it can identify chiral molecules visually based on color change and precipitation reaction, quantitatively analyze chiral molecules while determining the enantiomeric composition based on the fluorescence intensity change at different wavelengths, and obtain two parameters about chiral molecules from one measurement, thereby demonstrating its high selectivity, sensitivity and accuracy in chiral identification. In the field of organic circularly polarized luminescent (CPL) materials, the asymmetry (g lum ) of common organic light emitting elements is usually between 10 −5 and 10 −2 , whereas the CPL asymmetry factor (g lum ) of chiral AIE fluorogens (AIEgens) can reach 1.42, which is very close to the theoretical value of 2. Therefore, the combination of chiral elements and luminescent groups promotes their adoption in the field of organic CPL materials. Herein we have summarized the recent applications of chiral AIEgens in both chiral molecule recognition and circularly polarized organic light-emitting diode (CP-OLED) in order to provide future researchers with a more comprehensive and detailed understanding of chiral AIEgens and to encourage more scientists to contribute to the development of AIEgens.

Visualization of degradation of injectable thermosensitive hydroxypropyl chitin modified by aggregation-induced emission

The reversible thermosensitive hydroxypropyl chitin (HPCH) has been widely investigated for drug delivery, tissue engineering, wound repair and antibacterial hemostasis. To achieve non-invasive and real-time visualization of in vivo degradation of HPCH, aggregation-induced emission fluorogen (AIEgen) was introduced covalently in HPCH in water to obtain thermosensitive fluorescent hydroxypropyl chitin (FHPCH) avoiding using any organic solvent. The obtained fluorescent FHPCH hydrogel showed strong yellow-green fluorescence feature under UV irradiation, enabling visualization of the hydrogel with reversible thermosensitivity and reliable injectability. The in vitro enzymatic degradation study of FHPCH hydrogel showed that the attenuation of fluorescence intensity well matched with hydrogel weight loss. The injection through a 26-gauge needle for real-time fluorescence imaging in mice indeed indicated that AIE modified injectable thermosensitive FHPCH can be used for non-invasive, continuous and real-time visualization and quantitative analysis of in vivo degradation. This provides a new method for non-invasive real-time monitoring of similar implantable materials.

A versatile AIE fluorogen with selective reactivity to primary amines for monitoring amination, protein labeling, and mitochondrial staining

AbstractSpecific bioconjugation for native primary amines is highly valuable for both chemistry and biomedical research. Despite all the efforts, scientists lack a proper strategy to achieve high selectivity for primary amines, not to mention the requirement of fast response in real applications. Herein, we report a chromone‐based aggregation‐induced emission (AIE) fluorogen called CMVMN as a self‐reporting bioconjugation reagent for selective primary amine identification, and its applications for monitoring bioprocesses of amination and protein labeling. CMVMN is AIE‐active and capable of solid‐state sensing. Thus, its electrospun films are manufactured for visualization of amine diffusion and leakage process. CMVMN also shows good biocompatibility and potential mitochondria‐staining ability, which provides new insight for organelle‐staining probe design. Combined with its facile synthesis and good reversibility, CMVMN would not only show wide potential applications in biology, but also offer new possibilities for molecular engineering.

Size Optimization of Organic Nanoparticles with Aggregation-Induced Emission Characteristics for Improved ROS Generation and Photodynamic Cancer Cell Ablation.

Aggregation-induced emission (AIE) fluorogens provide new opportunities to promote efficient reactive oxygen species (ROS) production in aggregates, which represent the promising candidates to construct theranostic nanoparticles for photodynamic therapy (PDT), but the size effect has been rarely explored. Herein, a universal method to fabricate organic nanoparticles with controllable sizes is reported and it demonstrates that ≈45nm is the optimal size of AIE nanoparticles for PDT. Different from conventional Ce6 nanoparticles which show largely reduced fluorescence and ROS generation with increasing nanoparticle size, AIE nanoparticles show gradually enhanced brightness and ROS generation upon increasing the sizes from 6 to ≈45nm. Further increasing sizes could continue to intensify the nanoparticle's brightness at the expense of ROS production, with the optimal size for ROS generation being achieved at ≈45nm. Both 2D monolayer cell and 3D multicellular spheroid experiments confirm that 45nm AIE nanoparticles have the highest cellular uptake, the deepest penetration depth, and the best photodynamic killing effect. Such a study not only manifests the advantages of AIE photosensitizers, but also delivers the optimal size ranging for efficient PDT, which shall provide an attractive paradigm to guide the development of phototheranostic nanoparticles besides molecular design to further promote PDT applications.