Click chemistry is a flexible method featuring only the most feasible and efficient chemical reactions. The synthesis of 1,2,3-triazole from azides and terminal acetylenes using copper(I) as a catalyst is an extremely powerful reaction due to the extreme dependability, good selectivity, and biocompatibility of the starting materials. Triazole molecules are more than simple passive linkers; through hydrogen bonding and dipole interactions, they rapidly bind with biological targets. Its applications in drug development are expanding, ranging from target-oriented in situ chemistry and combinatorial mechanisms for lead generation to bioconjugation methods to study proteins and DNA. The click chemistry has frequently been used to speed up drug discovery and optimization processes in the past few years. The click chemistry reaction based on copper-catalyzed azide-alkyne cycloaddition (CuAAC) is a biochemical process with applications in medicinal chemistry and chemical biology. Thus, click reactions are an essential component of the toolkit for medicinal chemistry and help medicinal chemists overcome the barriers in chemical reactions, increase throughput, and improve the standards of compound libraries. The review highlights the recent advancements in the copper-catalyzed azide-alkyne cycloaddition (CuAAC) click chemistry approach for synthesizing biologically important triazole moieties with a greater emphasis on synthesis methodologies and pharmacological applications. Additionally, the triazole-based FDA-approved drugs are also discussed with their mode of action to highlight the importance of the click chemistry approach in synthesizing the bioactive triazole compounds.

The approach of metabolic chemical reporters (MCRs) for labeling proteins has been widely used in the past several decades. Nevertheless, artificial side reaction generated with fully protected MCRs, termed S-glyco-modification, occurs with cysteine residues through base-promoted β-elimination and Michael addition, leading to false positives in the proteomic identification. Therefore, next generation of MCRs, including partially protected strategy and modifications on the backbone of monosaccharides, have emerged to improve the labeling efficiency. In this paper, we prepared fifteen kinds of unnatural monosaccharides to investigate the relationships of structures and S-glyco-modification labeling. Our results demonstrated that Ac4GlcNAz and Ac4GalNAz exhibited the most remarkable labeling effects among the detected compounds. Of note, Ac4ManNAz, Ac46AzGlucose and Ac46AzGalactose containing similar structures but did not show similar robust signals as them. Moreover, other modifications on the 1-, 2-, 3-, 4- and 6-site indicated minimal side reactions of S-glyco-modification, raising a possibility that subtle modifications of monosaccharide substrate may alter its role in the process of biosynthesis, for example, by change of electronegativity or enhancement of steric hindrance effects. In conclusion, our discoveries provide a new avenue to choose appropriate probe for selective label proteins in vitro and in vivo without undesired S-glyco-modification.

Copper-catalyzed click chemistry offers creative strategies for activation of therapeutics without disrupting biological processes. Despite tremendous efforts, current copper catalysts face fundamental challenges in achieving high efficiency, atom economy, and tissue-specific selectivity. Herein, we develop a facile \"mix-and-match synthetic strategy\" to fabricate a biomimetic single-site copper-bipyridine-based cerium metal-organic framework (Cu/Ce-MOF@M) for efficient and tumor cell-specific bioorthogonal catalysis. This elegant methodology achieves isolated single-Cu-site within the MOF architecture, resulting in exceptionally high catalytic performance. Cu/Ce-MOF@M favors a 32.1-fold higher catalytic activity than the widely used MOF-supported copper nanoparticles at single-particle level, as first evidenced by single-molecule fluorescence microscopy. Furthermore, with cancer cell-membrane camouflage, Cu/Ce-MOF@M demonstrates preferential tropism for its parent cells. Simultaneously, the single-site CuII species within Cu/Ce-MOF@M are reduced by upregulated glutathione in cancerous cells to CuI for catalyzing the click reaction, enabling homotypic cancer cell-activated in situ drug synthesis. Additionally, Cu/Ce-MOF@M exhibits oxidase and peroxidase mimicking activities, further enhancing catalytic cancer therapy. This study guides the reasonable design of highly active heterogeneous transition-metal catalysts for targeted bioorthogonal reactions.

The microtubule-kinesin biomolecular motor system, which is vital for cellular function, holds significant promise for nanotechnological applications. In vitro gliding assays have demonstrated the ability to transport microcargo by propelling microtubules across kinesin-coated surfaces. However, the uncontrolled directional motion of microtubules has posed significant challenges, limiting the system\'s application for precise cargo delivery. Microfluidic devices provide a means to direct microtubule movement through their geometric features. Norland Optical Adhesive (NOA) is valued for its mold-free application in microfluidic device fabrication; however, microtubules often climb up channel walls, limiting controlled movement. In this study, a surface passivation method for NOA is introduced, using polyethylene glycol via a thiol-ene click reaction. This technique significantly improved the directional control and concentration of microtubules within NOA microchannels. This approach presents new possibilities for the precise application of biomolecular motors in nanotechnology, enabling advancements in the design of microfluidic systems for complex biomolecular manipulations.

Modifying cells with polymers on the surface can enable them to gain or enhance function with various applications, wherein the atom transfer radical polymerization (ATRP) has garnered significant potential due to its biocompatibility. However, specifically initiating ATRP from the cell surface for in-situ modification remains challenging. This study established a bacterial surface-initiated ATRP method and further applied it for enhanced Cr(VI) removal. The cell surface specificity was facilely achieved by cell surface labelling with azide substrates, following alkynyl ATRP initiator specifically anchoring with azide-alkyne click chemistry. Then, the ATRP polymerization was initiated from the cell surface, and different polymers were successfully applied to in-situ modification. Further analysis revealed that the modification of Shewanella oneidensis with poly (4-vinyl pyridine) and sodium polymethacrylate improved the heavy metal tolerance and enhanced the Cr(VI) removal rate of 2.6 times from 0.088 h-1 to 0.314 h-1. This work provided a novel idea for bacterial surface modification and would extend the application of ATRP in bioremediation.

Late-stage specific and selective diversifications of peptides and proteins performed at target residues under ambient conditions are recognized to be the most facile route to various and abundant conjugates. Herein, we report an orthogonal modification of cysteine residues using alkyl thianthreium salts, which proceeds with excellent chemoselectivity and compatibility under mild conditions, introducing a diverse array of functional structures. Crucially, multifaceted bioconjugation is achieved through clickable handles to incorporate structurally diverse functional molecules. This \"two steps, one pot\" bioconjugation method is successfully applied to label bovine serum albumin. Therefore, our technique is a versatile and powerful tool for late-stage orthogonal bioconjugation.

Current gold standard for the replacement of small-diameter blood vessel (ID < 4 mm) is still to utilize the autologous vessels of patients due to the limitations of small-diameter vascular grafts (SDVG) on weak endothelialization, intimal hyperplasia and low patency. Herein, we create the SDVG with the tailored endothelialization by applying the engineered endothelial cell vesicles to camouflaging vascular grafts for the enhancement of vascular remodeling. The engineered endothelial cell vesicles were modified with azide groups (ECVs-N3) through metabolic glycoengineering to precisely link the vascular graft made of PCL-DBCO via click chemistry, and thus fabricating ECVG (ECVs-N3 modified SDVG), which assists inhibition of platelet adhesion and activation, promotion of ECs adhesion and enhancement of anti-inflammation. Furthermore, In vivo single-cell transcriptome analysis revealed that the proportion of ECs in the cell composition of ECVG surpassed that of PCL, and the tailored endothelialization enabled to convert endothelial cells (ECs) into some specific ECs clusters. One of the specific cluster, Endo_C5 cluster, was only detected in ECVG. Consequently, our study integrates the engineered membrane vesicles of ECVs-N3 from native ECs for tailored endothelialization on SDVG by circumventing the limitations of living cells, and paves a new way to construct the alternative endothelialization in vessel remodeling following injury.

Sulfur fluoride exchange (SuFEx) and phosphorus fluoride exchange (PFEx) click chemistries are advancing research across multiple disciplines. By genetically incorporating latent bioreactive unnatural amino acids (Uaas), these chemistries have been integrated into proteins, enabling precise covalent linkages with biological macromolecules and paving the way for new applications. However, their suboptimal reaction rates in proteins limit effectiveness, and traditional catalytic methods for small molecules are often incompatible with biological systems or in vivo applications. We demonstrated that introducing an arginine adjacent to the latent bioreactive Uaa significantly boosts SuFEx and PFEx reaction rates between proteins. This method is effective across various Uaas, target residues, and protein environments. Notably, it also enables efficient SuFEx reactions in acidic conditions, common in certain cellular compartments and tumor microenvironments, which typically hinder SuFEx reactions. Furthermore, we developed the first covalent cell engager that substantially enhances natural killer cell activation through improved covalent interaction facilitated by arginine. These findings provide mechanistic insights and offer a biocompatible strategy to harness these robust chemistries for advancing biological research and developing new biotherapeutics.

A series of new 1,2,3-triazole fused chromene based glucose triazole conjugates were synthesized from chromene fused 1,2,3-triazolyl extended alkyne and 2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl azide in good to excellent yield by a copper catalyzed azide-alkyne cycloaddition (CuAAC) reaction. The major advantages include mild reaction conditions, high yield, good substrate scope, and shorter reaction time. The antibacterial efficacy of the compounds were assessed in vitro against human pathogenic Gram-negative E. coli and Gram-positive S. aureus bacteria. Compound 24j was found to be the most potent molecule with zone of inhibition (ZI) of 17 mm and minimum inhibitory concentration (MIC) of 25 μg mL-1 in E. coli and ZI of 16 mm and MIC of 25 μg mL-1 in S. aureus. Also, it significantly inhibited E. coli DNA-gyrase in silico with a binding affinity of -9.4 kcal/mol. Among all the synthesized compounds, 24i, 24d, 24e and 24f showed significant antibacterial activity against both strains and inhibited DNA-gyrase in silico with good binding affinities. Hence, these 1,2,3-triazole fused chromene based glucose triazole conjugates may evolve to be powerful antibacterial agents in recent future, according to structure-activity relationships based on strong antibacterial properties and molecular docking studies.

Modifying atomically precise nanocluster surfaces while maintaining the cluster core remains a key challenge. Herein, the synthesis, structure, and properties of two targeted Ag20 nanoclusters (NCs) with eight surface azide moieties, [CO3@Ag20(StBu)10(m-N3-C6H4COO)8(DMF)4] (1-m) and [CO3@Ag20(StBu)10(p-N3-C6H4COO)8(DMF)4] (1-p) are reported, where DMF is N,N-dimethylformamide. These AgNCs are designed to undergo cluster surface strain-promoted azide-alkyne cycloaddition (CS-SPAAC) reactions, introducing new functionality to the cluster surface. Reactivity is screened using model strained cyclooctynes. Reaction products and parent clusters are characterized by UV-vis, FT-IR, and NMR spectroscopies. The structure of the parent clusters and presence of surface azides is confirmed by single crystal X-ray diffraction (SCXRD) analysis. Clusters 1-m and 1-p are found to be amenable to CS-SPAAC reactions with retention of the NC frameworks, opening new routes for efficient modification of AgNC for applications.