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

Real-Time Visualization of Protein Microenvironment Changes with High Spatial Resolution in Live Cells via Site-Specific Incorporation of Rotor-Based Fluorescent Noncanonical Amino Acids

Traditional methods, such as the use of fluorescent protein fusions and environment-sensitive fluorophores, have limitations when studying protein microenvironment changes at the finest spatial resolution. These techniques often rely on bulky proteins or tags restricted to the N- or C-terminus, which can disrupt the natural behavior of the target protein and dramatically limit the ability of their method to investigate noninvasively microenvironment effects. To overcome these challenges, we have developed an innovative strategy to visualize microenvironment changes of protein substructures in real-time by genetically incorporating environment-sensitive noncanonical amino acids (ncAAs) containing rotor-based fluorophores (RBFs) at specific positions within a protein of interest. Through computational redesign of aminoacyl-tRNA synthetase, we successfully incorporated these rotor-based ncAAs into various proteins in mammalian cells. By site-specifically placing these ncAAs in distinct regions of proteins, we detected microenvironmental changes of several different protein domains during events such as aggregation, clustering, aggregation disassembly, and cluster dissociation.

Jellyfish-Inspired Artificial Spider Silk for Luminous Surgical Sutures

The development of functional surgical sutures with excellent mechanical properties, good fluorescence, and high cytocompatibility is highly required in the field of medical surgeries. Achieving fibers that simultaneously exhibit high mechanical robustness, good spinnability, and durable fluorescence emission has remained challenging up to now. Taking inspiration from the spinning process of spider silk and the luminescence mechanism of jellyfish, this work reports a luminous artificial spider silk prepared with the aim of balancing the fiber spinnability and mechanical robustness. This is realized by employing highly hydrated segments with aggregation-induced luminescence for enhancing the fiber spinnability and polyhydroxyl segments for increasing the fiber mechanical robustness. Twist insertion during fiber spinning improves the fiber strength, toughness, and fluorescence emission. Furthermore, coating the fiber with an additional polymer layer results in a "sheath-core" architecture with improved mechanical properties and capacity to withstand water. This work provides a new design strategy for performing luminescent and robust surgical sutures.

Green Fluorescent Carbon Dots with Critically Controlled Surface States: Make Silk Shine via Feeding Silkworms

Feeding silkworms with functional materials as additives to produce naturally modified silk is a facile, diverse, controllable, and environmentally friendly method with a low cost of time and investment. Among various additives, carbon dots (CDs) show unique advantages due to their excellent biocompatibility and fluorescence stability. Here, a new type of green fluorescent carbon dots (G-CDs) is synthesized with a high oil-water partition ratio of 147, a low isoelectric point of 5.16, an absolute quantum yield of 71%, and critically controlled surface states. After feeding with G-CDs, the silkworms weave light yellow cocoons whose green fluorescence is visible to the naked eye under UV light. The luminous silk is sewn onto the cloth to create striking patterns with beautiful fluorescence. Such G-CDs have no adverse effect on the survival rate and the life cycle of silkworms and enable their whole bodies to glow under UV light. Based on the strong fluorescence, chemical stability, and biological safety, G-CDs are found in the digestive tracts, silk glands, feces, cocoons, and even moth bodies. G-CDs accumulate in the posterior silk glands where fibroin protein is secreted, indicating its stronger combination with fibroin than sericin, which meets the requirements for practical applications.

Bioconjugation and Reaction-Induced Tumor Therapy via Alkynamide-Based Thiol-Yne Click Reaction

Ferroptosis is associated with the occurrence and development of many diseases, which is the result of an imbalance in cellular metabolism and oxidation-reduction balance. Therefore, it is an effective therapeutic strategy that simultaneously regulating the intracellular oxidation-reduction system. Herein, a click reaction of alkynylamide with thiol groups in the presence of amine or in PBS (pH = 7.4) is developed, which can react efficiently with thiol substances, such as cysteine (Cys), glutathione (GSH), and bovine serum albumin (BSA). Notably, MBTB-PA, an aggregation-induced emission (AIE) photosensitizer with an alkynylamide unit, is synthesized and its intracellular behavior is visualized in situ by fluorescence imaging, demonstrating its excellent ability to target the endoplasmic reticulum. Furthermore, MBTB-PA reacted with proteins in tumor cells, consumed reducing substances, and triggered intracellular oxidative stress, resulting in cell death. Based on this reaction therapy strategy, click reaction is combined with photodynamic therapy to achieve effective killing of tumor cells by simultaneously raising the intracellular oxidative state and reducing the reductive state. This work not only develops an application of click reaction of alkynamide with thiol in bioconjugation and anti-tumor therapy, but also provides feasible ideas for organic reactions in the exploration of organisms.

Phosphine-Capped Effects Enable Full-Color Clusteroluminescence in Nonconjugated Polyesters

Full-color luminophores have advanced applications in materials and engineering, but constructing color-tunable clusteroluminescence (CL) from nonconjugated polymers based on through-space interactions remains a huge challenge. Herein, we develop phosphine-capped nonconjugated polyesters exhibiting blue-to-red CL (400-700 nm) based on phosphine-initiated copolymerization of epoxides and cyclic anhydrides, especially P1-0.5TPP, which exhibits red CL (610 nm) with a high quantum yield of 32%. Experiments and theoretical calculations disclose that the phosphine-capped effect in polyesters brings about conformational changes and induces phosphine-ester clusters by through-space (n,π*) interactions. Moreover, CL colors and efficiencies can be easily tailored by types of phosphines, compositions and structures of polyesters, and concentration. Significantly, the role of polymer motions (group, segmental, and chain motions) on CL originating from microregions inside polyesters is revealed. Further, phosphine-capped nonconjugated polyesters are demonstrated to be nonconjugated dyes and fluorescent fibers and are also used for multicolor light-emitting diodes including white light. This work not only provides an engineering strategy based on the end-group effect to prepare full-color clusteroluminogens but also broadens the prospects for material applications.

Efficient Conversion of Inert Nitriles to Multifunctional Poly(5-amino-1,2,3-triazole)s via Regioselective Click Polymerization with Azide Monomers under Ambient Conditions

Nitrile compounds are abundant, stable, cheap, and readily available natural and chemical industrial sources. However, the efficient conversion of nitrile monomers to functional polymers is mostly limited due to their inert reactivity, and developing efficient polymerizations based on nitrile monomers under very mild conditions is still a big challenge. In this work, a facile and powerful base-catalyzed acetonitrile-azide click polymerization was successfully established under ambient conditions. This polymerization also enjoys the merits of short reaction time (15 min), 100% atom economy, transition-metal-free catalyst system, and regioselectivity. A series of poly(5-amino-1,2,3-triazole)s (PATAs) with high weight-average molecular weights (Mw, up to 204,000) were produced in excellent yields (up to 99%). The PATAs containing tetraphenylethene (TPE) moieties exhibit unique aggregation-induced emission (AIE) characteristics, which could be used to sensitively detect Fe(III) ions with a low limit of detection (1.205 × 10-7 M) and to specifically image lysosomes of living cells. Notably, PATAs could be facilely post-modified due to their containing primary amino groups in the polymer chains even through a one-pot tandem reaction. Thus, this work not only establishes a new powerful click polymerization to convert stable nitriles but also generates a series of PATAs with versatile properties for diverse applications.

Dynamic Motions of Ligands around the Metal Centers Afford a Fidget Spinner-Type AIE Luminogen

A new type of aggregation-induced emission (AIE) luminogen containing a dimeric metal fragment and two or three phthalazine ligands is described, which shows dynamic motions of ligands around the metal centers in solution. Based on the variable-temperature and EXSY NMR spectroscopy data, X-ray crystallography structures, and computational results, three different pathways (i.e., reversible exchange with haptotropic shifts, circulation of ligands around the dimeric metal fragment, and walking on the spot of ligands on the metal centers) were considered for this dynamic behavior. Restriction of these dynamic processes in the aggregate forms of the compounds (in H2O/CH3CN solvent mixtures) contributes to their AIE. DFT calculations and NMR analysis showed that bright excited states for these molecules are not localized on isolated molecules, and the emission of them stemmed from π-dimers or π-oligomers. The morphologies and the mode of associations in the solvent mixtures were determined by using transmission electron microscopy (TEM) and concentration-dependent NMR spectroscopy. The computational results showed the presence of a conical intersection (CI) between the S0 and S1 excited state, which provides an accessible pathway for nonradiative decay in these systems.

Capturing Doublet Intermediate Emitters by Chemically Crosslinking Confinement towards Spatiotemporal Encryption

Photoluminescence is one of the most meticulous ways to manipulate light energy. Typical photoluminescent emitters are mostly stable substances with a pure photophysical process of spontaneous photon-emission from their excited states. Intermediate emitters are elusive attributing to their synchronous energy transfer process including photophysical and incomplete photochemical pathways. An intermediate emitter containing radicals is more difficult to be observed due to its inherent chemical reactivity. Here, these challenges are overcome by spontaneously formed space limitations in polymer crosslinking networks meanwhile chemically active intermediates are captured. These doublet intermediates exhibit unique long-wavelength emissions under chemically crosslinking confinement conditions, and their luminous mechanism provides a novel perspective for designing intermediate emitters with liquid-crystal character and photoresponsive features towards spatiotemporal encryption, promising for the detection of photochemical reactions and the development of fascinating luminescent systems.

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.

Chromene-based BioAIEgens: 'in-water' synthesis, regiostructure-dependent fluorescence and ER-specific imaging

Exploration of artificial aggregation-induced emission luminogens (AIEgens) has garnered extensive interest in the past two decades. In particular, AIEgens possessing natural characteristics (BioAIEgens) have received more attention recently due to the advantages of biocompatibility, sustainability and renewability. However, the extremely limited number of BioAIEgens extracted from natural sources have retarded their development. Herein, a new class of BioAIEgens based on the natural scaffold of chromene have been facilely synthesized via green reactions in a water system. These compounds show regiostructure-, polymorphism- and substituent-dependent fluorescence, which clearly illustrates the close relationship between the macroscopic properties and hierarchical structure of aggregates. Due to the superior biocompatibility of the natural scaffold, chromene-based BioAIEgens can specifically target the endoplasmic reticulum (ER) via the introduction of tosyl amide. This work has provided a new chromene scaffold for functional BioAIEgens on the basis of green and sustainable 'in-water' synthesis, applicable regiostructure-dependent fluorescence, and effective ER-specific imaging.

Towards bioresource-based aggregation-induced emission luminogens from lignin β-O-4 motifs as renewable resources

One-pot synthesis of heterocyclic aromatics with good optical properties from phenolic β-O-4 lignin segments is of high importance to meet high value added biorefinery demands. However, executing this process remains a huge challenge due to the incompatible reaction conditions of the depolymerization of lignin β-O-4 segments containing γ-OH functionalities and bioresource-based aggregation-induced emission luminogens (BioAIEgens) formation with the desired properties. In this work, benzannulation reactions starting from lignin β-O-4 moieties with 3-alkenylated indoles catalyzed by vanadium-based complexes have been successfully developed, affording a wide range of functionalized carbazoles with up to 92% yield. Experiments and density functional theory calculations suggest that the reaction pathway involves the selective cleavage of double C-O bonds/Diels-Alder cycloaddition/dehydrogenative aromatization. Photophysical investigations show that these carbazole products represent a class of BioAIEgens with twisted intramolecular charge transfer. Distinctions of emission behavior were revealed based on unique acceptor-donor-acceptor-type molecular conformations as well as molecular packings. This work features lignin β-O-4 motifs with γ-OH functionalities as renewable substrates, without the need to apply external oxidant/reductant systems. Here, we show a concise and sustainable route to functional carbazoles with AIE properties, building a bridge between lignin and BioAIE materials.

Activated alkyne-enabled turn-on click bioconjugation with cascade signal amplification for ultrafast and high-throughput antibiotic screening

Antimicrobial susceptibility testing plays a pivotal role in the discovery of new antibiotics. However, the development of simple, sensitive, and rapid assessment approaches remains challenging. Herein, we report an activated alkyne-based cascade signal amplification strategy for ultrafast and high-throughput antibiotic screening. First of all, a novel water-soluble aggregation-induced emission (AIE) luminogen is synthesized, which contains an activated alkyne group to enable fluorescence turn-on and metal-free click bioconjugation under physiological conditions. Taking advantage of the in-house established method for bacterial lysis, a number of clickable biological substances (i.e., bacterial solutes and debris) are released from the bacterial bodies, which remarkably increases the quantity of analytes. By means of the activated alkyne-mediated turn-on click bioconjugation, the system fluorescence signal is significantly amplified due to the increased labeling sites as well as the AIE effect. Such a cascade signal amplification strategy efficiently improves the detection sensitivity and thus enables ultrafast antimicrobial susceptibility assessment. By integration with a microplate reader, this approach is further applied to high-throughput antibiotic screening.

As Fiber Meets with AIE: Opening a Wonderland for Smart Flexible Materials

Aggregation-induced emission luminogens (AIEgens) have recently been developed at a tremendous pace in the area of organic luminescent materials by virtue of their superior properties. However, the practical applications of AIEgens still face the challenge of transforming AIEgens from molecules into materials. Till now, many AIEgens have been integrated into fiber, endowing the fiber with prominent fluorescence and/or photosensitizing capacities. AIEgens and fiber complement each other for making progress in flexible smart materials, in which the utilization of AIEgens creates new application possibilities for fiber, and the fiber provides an excellent carrier for AIEgens towards realizing the conversion from molecule to materials and an ideal platform to research the aggregate state of AIEgens in mesoscale and macroscale. This review begins with a brief summary of the recent advances related to some typical AIEgens with various functions and the technology for the fabrication of AIEgen-functionalized fiber. The most representative applications are then highlighted by focusing on energy conversion, personal protective equipment, biomedical, sensor, and fluorescence-related fields. Finally, the challenges, opportunities, and tendencies in future development are discussed in detail. This review hopes to inspire innovation in AIEgens and fiber from the view of mesoscale and macroscale.

Full-Color Emissive D-D-A Carbazole Luminophores: Red-to-NIR Mechano-fluorochromism, Aggregation-Induced Near-Infrared Emission, and Application in Photodynamic Therapy

The preparation of multifunctionalized luminophores with full-color emission based on an identical core skeleton is a significative but challenging research topic. In this work, eight donor-donor-acceptor (D-D-A)-type luminogens based on a central carbazole core bearing a C₆ hydrocarbon chain were designed by using different kinds of donor and acceptor units on the left and right, and synthesized in good yields. These D-D-A carbazole derivatives display deep-blue, sky-blue, cyan, green, yellow-green, yellow, orange and red fluorescence in the solid state, achieving full-color emission covering the whole visible light range under UV light illumination. Notably, the dicyano-functionalized triphenylamine-containing carbazole derivative exhibits rare aggregation-induced near-infrared emission and red-to-near-infrared mechano-fluorochromism with high contrast beyond 100 nm. Furthermore, the red-emissive luminogen can serve as a potential candidate for cell imaging and photodynamic therapy (PDT). This work not only provides reference for the construction of full-color emissive systems but also opens a new avenue to the preparation of multifunctionalized luminophores capable of simultaneous application in near-Infrared mechanical-force sensors and PDT fields.

Carbazole-based aggregation-induced phosphorescent emission-active gold(I) complexes with various phosphorescent mechanochromisms

A series of carbazole-containing gold(I) complexes modified with different substituents were successfully designed and synthesized, and their molecular structures were characterized by nuclear magnetic resonance spectroscopy and mass spectrometry. The aggregation-induced behaviors of these gold(I) complexes were studied by ultraviolet/visible and photoluminescence spectroscopy. Meanwhile, their mechanical force-responsive emissive properties were also investigated via solid-state photoluminescence spectroscopy. Interestingly, all these gold(I)-based luminogenic molecules were capable of exhibiting aggregation-induced phosphorescent emission phenomena. Furthermore, their solids of three gold(I) complexes displayed contrasting mechano-responsive phosphorescence features. More specifically, trifluoromethyl or methoxyl-substituted luminophores 1 and 3 demonstrated mechanochromic behaviors involving blue-shifted phosphorescence changes, and their mechanoluminochromic phenomena were reversible. However, the solid-state phosphorescence of phenyl-substituted luminophor 2 was not sensitive to external mechanical force.

Biological Synthesis and Process Monitoring of an Aggregation-Induced Emission Luminogen-Based Fluorescent Polymer

As the most abundant and renewable biopolymer on earth, cellulose can be functionalized for various advanced applications by chemical modification. In addition, fluorescent polymers with aggregation-induced emission (AIE) are generally prepared using chemical approaches, and the biosynthesis of AIE-active polymers are rarely investigated. Herein, fluorescent cellulose was successfully synthesized by bacterial fermentation, where glucosamine-modified AIE luminogen was incorporated into cellulose to achieve AIE-active biopolymers. Excitingly, real-time visualization of the synthetic process was realized, which is crucial for investigating the process of bacterial fermentation. The biosynthesized cellulose exhibited better performance with uniform fluorescence distribution and high stability, compared with that prepared by physical absorption. Additionally, fluorescent mats were fabricated by electrospinning of AIE-active cellulose, demonstrating its great potential applications in flexible display and tissue engineering.

Fibrous aggregates: Amplifying aggregation-induced emission to boost health protection

Environmental monitoring and personal protection are critical for preventing and for protecting human health during all infectious disease outbreaks (including COVID-19). Fluorescent probes combining sensing, imaging and therapy functions, could not only afford direct visualizing existence of biotargets and monitoring their dynamic information, but also provide therapeutic functions for killing various bacteria or viruses. Luminogens with aggregation-induced emission (AIE) could be well suited for above requirements because of their typical photophysical properties and therapeutic functions. Integration of these molecules with fibers or textiles is of great interest for developing flexible devices and wearable systems. In this review, we mainly focus on how fibers and AIEgens to be combined for health protection based on the latest advances in biosensing and bioprotection. We first discuss the construction of fibrous sensors for visualization of biomolecules. Next recent advances in therapeutic fabrics for individual protection are introduced. Finally, the current challenges and future opportunities for "AIE + Fiber" in sensing and therapeutic applications are presented.

Scalable Fabrication of Highly Breathable Cotton Textiles with Stable Fluorescent, Antibacterial, Hydrophobic, and UV-Blocking Performance

Multifunctional cotton textiles that are highly breathable are desirable in a broad range of applications. However, it is still a big challenge to scale up production of such multifunctional cotton textiles. Herein, we developed a simple, scalable, and benign strategy to fabricate highly breathable multifunctional cotton textiles via mild surface modification. The 1,4-dihydropyridine (DHP) ring and gentamycin sulfate (GS) molecules were firmly attached to the cellulose chains under room temperature via a one-pot method. The resulting modified cotton textile showed integrated performances with bright fluorescence, good antibacterial behavior, hydrophobic behavior (contact angle of 134°), and UV-blocking (UPF being up to 69.2), which are very stable toward washing and various solvents. There is no obvious change in the whiteness, thermal stability, and mechanical performance of cotton fabrics after the surface modification. What's more, the air permeability of the modified cotton fabric was up to 31.3 (cm3/cm2)/s. This study not only focuses on the materials design and large-scale fabrication but also provides stable and multifunctional cotton textiles with broad application prospects for many fields.

Aliphatic Polyesters with White-Light Clusteroluminescence

Single-molecule white-light emission (SMWLE) has many advantages in practical applications; however, the fabrication of SMWLE from nonconjugated luminescent polymers, namely, clusteroluminogens (CLgens), is still a big challenge. Herein, the first example of linear nonconjugated polyesters with SMWLE is reported. Twenty-four kinds of nonconjugated aliphatic polyesters with tunable clusteroluminescence (CL) colors and efficiency were synthesized by the copolymerization of six epoxides and four anhydrides. Experimental and calculation results prove that, at the primary structure level, the balance of structural flexibility and rigidity via adjusting the side-chain length significantly enhances the efficiency of CL without wavelength change. However, altering the chemical structures of the monomer from succinic anhydride to trans-maleic anhydride (MA), cis-MA, and citraconic anhydride (CA), secondary structures of these polyesters change from helix to straight and folding sheet accompanied by gradually red-shifted CL from 460 to 570 nm due to the increase in through-space n-π* interactions, as demonstrated by the computational and experimental results. Then, pure SMWLE with CIE coordination (0.30, 0.32) based on overlapped short-wavelength and long-wavelength CL is achieved in CA-based polyesters. This work not only provides further insights into the emission mechanism of CL but also provides a new strategy to manipulate the properties of CL by regulating the hierarchical structures of CLgens.

Near-Infrared-Emissive AIE Bioconjugates: Recent Advances and Perspectives

Near-infrared (NIR) fluorescence materials have exhibited formidable power in the field of biomedicine, benefiting from their merits of low autofluorescence background, reduced photon scattering, and deeper penetration depth. Fluorophores possessing planar conformation may confront the shortcomings of aggregation-caused quenching effects at the aggregate level. Fortunately, the concept of aggregation-induced emission (AIE) thoroughly reverses this dilemma. AIE bioconjugates referring to the combination of luminogens showing an AIE nature with biomolecules possessing specific functionalities are generated via the covalent conjugation between AIEgens and functional biological species, covering carbohydrates, peptides, proteins, DNA, and so on. This perfect integration breeds unique superiorities containing high brightness, good water solubility, versatile functionalities, and prominent biosafety. In this review, we summarize the recent progresses of NIR-emissive AIE bioconjugates focusing on their design principles and biomedical applications. Furthermore, a brief prospect of the challenges and opportunities of AIE bioconjugates for a wide range of biomedical applications is presented.

Mapping the Regioisomeric Space and Visible Color Range of Purely Organic Dual Emitters with Ultralong Phosphorescence Components: From Violet to Red Towards Pure White Light

We mapped the entire visible range of the electromagnetic spectrum and achieved white light emission (CIE: 0.31, 0.34) by combining the intrinsic ns-fluorescence with ultralong ms-phosphorescence from purely organic dual emitters. We realized small molecular materials showing high photoluminescence quantum yields (ΦL ) in the solid state at room temperature, achieved by active exploration of the regioisomeric substitution space. Chromophore stacking-supported stabilization of triplet excitons with assistance from enhanced intersystem crossing channels in the crystalline state played the primary role for the ultra-long phosphorescence. This strategy covers the entire visible spectrum, based on organic phosphorescent emitters with versatile regioisomeric substitution patterns, and provides a single molecular source of white light with long lifetime (up to 163.5 ms) for the phosphorescent component, and high overall photoluminescence quantum yields (up to ΦL =20 %).

Colorimetric and Fluorescent Dual-Signal Chemosensor for Lysine and Arginine and Its Application to Detect Amines in Solid-Phase Peptide Synthesis

Lysine (Lys) and arginine (Arg), as two of the most alkaline amino acids among 20 common amino acids, are closely involved in many vital biological processes and biomaterial synthesis. Abnormal levels of Lys and Arg can lead to various diseases. Although a limited number of fluorescent probes for Lys and Arg have been reported, many of them are not sensitive enough due to the moderate fluorescence signal and on-off mode. In addition, none of them were applied for detecting amine groups in solid-phase peptide synthesis. In this study, we designed and synthesized optical fluorescent probe 1 based on the benzoxadiazole fluorophore, which could undergo an accelerated hydrolysis reaction under basic conditions. Probe 1 revealed excellent selectivity toward alkaline Lys and Arg over other common amino acids with both fluorometric and colorimetric readouts. After treatment with Lys and Arg, probe 1 could emit a turn-on fluorescent response at 580 nm with a distinct color change from pink to yellow. The limit of detection for Lys and Arg was calculated to be 1.1 and 1.39 μM, respectively. We also successfully applied probe 1 for the visualization of Arg in living cells. Moreover, to the best of our knowledge, probe 1 provided the first fluorescent platform to detect -NH₂ groups in solid-phase synthesis of peptides with distinct fluorescent and colorimetric changes. We envision that the probe can provide an alternative method for the traditional Kaiser test.