An Overview of Recent Advances in Biomedical Applications of Click Chemistry

A Click-generated chalcone allied triazole sensor for Co (II) with INHIBIT logic gate construction and its antioxidant properties

This article presents the synthesis of chalcone allied 1,2,3-triazole via an aldol-click reaction. The newly synthesized compound chalcogenyl based 1,2,3-triazole (7) selectively detects Co (II) ion over other metal cations by UV-visible photophysical study with the limit of detection value of 1.24 × 10-8 M. Job's plot confirms that compound (7) and the Co (II) metal ion have 1:1 binding stoichiometry. The binding mechanism between Co (II) and sensor was confirmed by using 1H NMR spectroscopy, mass spectrometry and DFT studies. The reversible behaviour of 7 towards Co (II) was used to construct a molecular logic gate. The compound (7) demonstrated good antioxidant activity with an IC50 value of 3.04 µM in comparison to 1.31 µM of DPPḢ. Further, to explore the antioxidant effect of ligand 7, the molecular docking analysis was performed with xanthine oxidase protein and the obtained binding energy was -11.08 kcal/mol.

Click and shift: the effect of triazole on solvatochromic dyes

Solvatochromic dyes are prime candidates for exploring complex polarity-dependent biological processes. The design of novel dyes for these applications typically presents long synthetic routines. Herein, we report a concise synthesis of azido-functionalised push-pull fluorenes, belonging to the most potent groups of fluorosolvatochromic compounds. These fluorenes can be attached to multiple alkynes via the highly versatile copper-catalysed azide-alkyne cycloaddition (CuAAC). Our study focuses on the beneficial effect of the triazole, formed by CuAAC, comparing the simple push-pull fluorene FR1 with the novel model compound FR1TP. While the triazole in FR1TP is not conjugated to the π-system of the dye, the heterocycle surprisingly produces a bathochromic emission shift of around 50 nm. This effect, caused by triazole-induced LUMO stabilisation, was also observed for two other model compounds: FR2TP and FR1TM. All compounds display photophysical properties that are highly desired for in vivo imaging dyes, including remarkable two-photon absorption properties. The experimental results are supported by theoretical calculations. We anticipate that our findings will enable synthesis of new high-performance fluorosolvatochromic dyes for diverse applications.

Reaction development: a student's checklist

So you've discovered a reaction. But how do you turn this new discovery into a fully-fledged program that maximises the potential of your novel transformation? Herein, we provide a student's checklist to serve as a helpful guide for synthesis development, allowing you to thoroughly investigate the chemistry in question while ensuring that no key aspect of the project is overlooked. A wide variety of the most illuminating synthetic and spectroscopic techniques will be summarised, in conjunction with literature examples and our own insights, to provide sound justifications for their implementation towards the goal of developing new reactions.

Safirinium Fluorescent "Click" Molecular Probes: Synthesis, CuAAC Reactions, and Microscopic Imaging

Fluorescent labeling utilizing Cu(I)-catalyzed azide-alkyne cycloaddition reactions (CuAAC) is among the leading applications of the "click" chemistry strategy. Fluorescent probes for this approach can be constructed by linking an azide or alkyne group to a fluorophore, such as the recently developed Safirinium derivatives. These compounds are water-soluble, highly fluorescent heterocycles based on 1,2,4-triazolium, with significant potential for various labeling applications, although they have not yet been converted to azide or alkyne probes. Herein, we report the synthesis of Safirinium-based azide and alkyne functionalized molecular probes for "click" chemistry labeling. We also describe their CuAAC reactions with model compounds, including a lipid mimetic long-chain azide, an azido sugar derivative, and azidothymidine, as well as two model alkynes. We demonstrate that the Safirinium-based probes and their derivatives are chemically stable, suitable for fluorescent microscopy observations, and safe to use. Most of these probes show no toxic effects on CHO-K1 and NIH-3T3 cells.

High-Throughput Combinatorial Metal Complex Synthesis

High-throughput combinatorial metal complex synthesis has emerged as a powerful tool for rapidly generating and screening diverse libraries of metal complexes, enabling accelerated discovery in fields such as catalysis, medicinal chemistry, and materials science. By systematically combining building blocks under mild and efficient conditions, researchers can explore broad chemical spaces, increasing the likelihood of identifying complexes with desired properties. This method streamlines hit identification and optimisation, especially when integrated with high-throughput screening and data-driven approaches like machine learning. Despite challenges such as scalability and purity control, recent advancements in automation and predictive modelling are enhancing the efficiency of combinatorial synthesis, opening new avenues for the development of metal-based catalysts, therapeutic agents, and functional materials.

Facets of click-mediated triazoles in decorating amino acids and peptides

Decorating biomolecular building blocks, such as amino acids, to afford desired and tuneable photophysical/biophysical properties would allow chemical biologists to use them for several biotechnological and biosensing applications. While many synthetic methodologies have been explored in this direction, advantages provided by click-derived triazole moieties are second to none. However, since their discovery, click-mediated triazoles have been majorly utilised as linkers for conjugating biomolecules, creating materials with novel properties, such as polymers or drug conjugates. Despite exploring their profound role as linkers, click-mediated triazoles as an integral part of biomolecular building blocks have not been addressed. 1,2,3-Triazole, a transamide mimic, exhibits high aromatic stacking propensity, high associability with biomolecules through H-bonding, and high stability against enzymatic hydrolysis. Furthermore, triazoles can be considered donors useable for installation/modulation of the photophysics of a fluorophore. Therefore, triazole with a chromophoric unit may rightly be utilised as an integral part of biomolecular building blocks to install microenvironment-sensitive solvofluorochromic properties suitable for biological sensing, studying inter-biomolecular interactions and introducing novel physicochemical properties in a biomolecule. This review mainly focuses on the facets of click-derived triazole in designing novel fluorescent amino acids and peptides with a particular emphasis on those wherein triazole acts as an integral part of amino acids, i.e. the side chain, generating a new class of fluorescent unnatural triazolyl amino acids. Thus, fluorescent triazolyl unnatural amino acids, peptidomimetics with such amino acids and aliphatic/aromatic triazolyl amino acids as scaffolds for peptidomimetics are the central part. However, to start with, a brief history, followed by a discussion on various other relevant facets of triazoles as linkers in various fields ranging from therapeutics, materials science, diagnostics, and bioconjugation to peptidomimetics, is cited. Additionally, the possible roles of CuAAC-mediated triazoles in shaping the future of bioorganic chemistry, medicinal chemistry, diagnostics, nucleoside chemistry and protein engineering are briefly discussed.

A Sonochemical and Mechanochemical One-Pot Multicomponent/Click Coupling Strategy for the Sustainable Synthesis of Bis-Heterocyclic Drug Scaffolds

Bis-heterocycles were synthesized via a consecutive one-pot process by a Groebke-Blackburn-Bienaymé reaction (GBB-3CR) followed by Copper-catalyzed Alkyne-Azide Cycloaddition (CuAAC) assisted by alternative sustainable energies (ASE) such as ultrasonic and mechanical. These efficient and convergent strategies allowed the in situ generation of complex azides functionalized with imidazo[1,2-a]pyridines (IMPs), which was used as a synthetic platform. The target molecules contain two privileged scaffolds in medicinal chemistry: IMPs and the heterocyclic bioisostere of trans-amide bond, the 1,4-disubstituted 1H-1,2,3-triazoles (1,4-DS-1,2,3-Ts).

Insight into Protein Engineering: From In silico Modelling to In vitro Synthesis

Protein engineering alters the polypeptide chain to obtain a novel protein with improved functional properties. This field constantly evolves with advanced in silico tools and techniques to design novel proteins and peptides. Rational incorporating mutations, unnatural amino acids, and post-translational modifications increases the applications of engineered proteins and peptides. It aids in developing drugs with maximum efficacy and minimum side effects. Currently, the engineering of peptides is gaining attention due to their high stability, binding specificity, less immunogenic, and reduced toxicity properties. Engineered peptides are potent candidates for drug development due to their high specificity and low cost of production compared with other biologics, including proteins and antibodies. Therefore, understanding the current perception of designing and engineering peptides with the help of currently available in silico tools is crucial. This review extensively studies various in silico tools available for protein engineering in the prospect of designing peptides as therapeutics, followed by in vitro aspects. Moreover, a discussion on the chemical synthesis and purification of peptides, a case study, and challenges are also incorporated.

The cyclization of human salivary Histatin 1 via click chemistry for skin wound healing

Acute skin injuries can result in the breakdown of the skin barrier, heightening the risk of infections and complications. Histatin 1 (Hst1) promotes the adhesion, spreading, and migration of various skin-related cells, thus encouraging wound healing. However, Hst1 is extensively degraded upon exposure to wound exudates. Cyclized hst1 (Cyclic-hst1) has a much higher resistance to protease degradation than Hst1, thus increasing its stability and half-life. Herein, we synthesized Cyclic-hst1 via a click reaction and explored its efficacy in wound healing via cellular and animal experiments. Cyclic-hst1, at a 100-fold lower concentration than Hst1, effectively promoted acute skin wound healing. In addition, Cyclic-hst1 had a superior effect to Hst1 in terms of its anti-inflammatory, re-epithelialization, collagen deposition, and angiogenic effects, thus significantly promoting skin wound healing. Consequently, Cyclic-hst1 could represent a favorable treatment to manage acute skin wound healing, providing a promising experimental basis for clinical transformation and application.

Click Chemistry as an Efficient Toolbox for Coupling Sterically Hindered Molecular Systems to Obtain Advanced Materials for Nanomedicine

Since its conceptualization, click chemistry in all its variants has proven to be a superior synthesis protocol, compared to conventional methods, for forming new covalent bonds under mild conditions, orthogonally, and with high yields. If a term like reactive resilience could be established, click reactions would be good examples, as they perform better under increasingly challenging conditions. Particularly, highly hindered couplings that perform poorly with conventional chemistry protocols-such as those used to conjugate biomacromolecules (e.g., proteins and aptamers) or multiple drugs onto macromolecular platforms-can be more easily achieved using click chemistry principles, while also promoting high stereoselectivity in the products. In this review, three molecular platforms relevant in the field of nanomedicine are considered: polymers/copolymers, cyclodextrins, and fullerenes, whose functionalization poses a challenge due to steric hindrance, either from the intrinsic bulk behavior (as in polymers) or from the proximity of confined reactive sites, as seen in cyclodextrins and fullerenes. Their functionalization with biologically active groups (drugs or biomolecules), primarily through copper-catalyzed azide-alkyne cycloaddition (CuAAC), strain-promoted azide-alkyne cycloaddition (SPAAC), inverse electron-demand Diels-Alder (IEDDA) and thiol-ene click reactions, has led to the development of increasingly sophisticated systems with enhanced specificity, multifunctionality, bioavailability, delayed clearance, multi-targeting, selective cytotoxicity, and tracking capabilities-all essential in the field of nanomedicine.

Click chemistry-based dual nanosystem for microRNA-122 detection with single-base specificity from tumour cells

MicroRNAs (miRNAs) have been recognised as potential biomarkers due to their specific expression patterns in different biological tissues and their changes in expression under pathological conditions. MicroRNA-122 (miR-122) is a vertebrate-specific miRNA that is predominantly expressed in the liver and plays an important role in liver metabolism and development. Dysregulation of miR-122 expression is associated with several liver-related diseases, including hepatocellular carcinoma and drug-induced liver injury (DILI). Given the potential of miR-122 as a biomarker, its effective detection is important for accurate diagnosis. However, miRNA detection methods still face challenges, particularly in terms of accurately identifying miRNA isoforms that may differ by only a single base. Here, with the aim of advancing accessible methods for the detection of miRNAs with single-base specificity, we have developed a robust dual nanosystem that leverages the simplicity of click chemistry reactions. Using the dual nanosystem, we successfully detected miR-122 at single-base resolution using flow cytometry and analysed its expression in various tumour cell lines with high specificity and strong correlation with TaqMan assay results. We also detected miR-122 in serum and identified four single nucleotide variations in its sequence. The chemistry employed in this dual nanosystem is highly versatile and offers a promising opportunity to develop nanoparticle-based strategies that incorporate click chemistry and bioorthogonal chemistry for the detection of miRNAs and their isoforms.

Metal-Free Synthesis of Benzisoxazolones Utilizing ortho-Ester and ortho-Cyano-Functionalized Diaryliodonium Salts with Protected Hydroxylamines

Herein, we report the development of metal-free one/two-pot procedures for the synthesis of benzo[c]isoxazol-3(1H)-one (benzisoxazolone) heterocycles by designing diaryliodonium salts featuring ortho-ester or nitrile functional groups. These react smoothly with protected hydroxylamines under mild conditions to produce N-arylhydroxylamine intermediates, which readily cyclize to give benzisoxazolone derivatives under acidic conditions. This metal-free process maintains the weak N-O bond, tolerates a wide range of diaryliodonium salts and protected hydroxylamines with diverse functional/protecting groups, thereby overcoming the challenges associated with previous transformations. The protocol expands the reaction scope and broadens the chemical space of the fused isoxazolone backbones to include unprecedented five-membered heteroaryl-fused isoxazolones in high yields. This method is also applicable to gram-scale synthesis, and the resulting benzisoxazolones can be effectively derivatized at the N-position to afford valuable compounds.

HFIP-Mediated Synthesis of 4-Aryl-NH-1,2,3-Triazoles and 1,5-Disubstituted 1,2,3-Triazolyl Glycoconjugates

We herein report a multicomponent reaction for the synthesis of N-unsubstituted-1,2,3-triazoles and N-substituted-1,2,3 triazoles from the reaction of aldehydes, nitroalkanes, and sodium azides/glycosyl azides in the presence of 1,1,1,3,3,3-hexafluoroisopropanol, a hydrogen bond-donating reaction medium. This three-component reaction provides a metal-free strategy for sequentially forming one C-C and two C-N bonds in a one-pot fashion. One-pot mild reaction condition, operational simplicity, wide substrate scope, good functional group tolerance, easy purification, high reaction yields, and altogether excellent regioselectivity are the notable advantages of this 1,2,3-triazole-forming protocol. Moreover, this protocol provides practical access to the gram-scale synthesis of potent inhibitors of indoleamine 2,3-dioxygenase 1.

Linker Chemistry and Connectivity Fine-Tune the Immune Response and Kinetic Solubility of Conjugated NOD2/TLR7 Agonists

There is a growing interest in developing novel immune potentiators capable of eliciting a cellular immune response. We tackle this challenge by harnessing the synergistic cross-activation between two innate immune receptors─the nucleotide-binding oligomerization domain-containing protein 2 (NOD2) and Toll-like receptor 7 (TLR7). Herein, we investigate the structure-activity relationship of a series of novel conjugated NOD2/TLR7 agonists incorporating a variety of flexible aliphatic, poly(ethylene glycol)-based and triazole-featuring linkers. Our findings reveal potent immune-enhancing properties of conjugates in human primary peripheral blood mononuclear cells, characterized by a Th1/Th17 polarized cytokine response. Importantly, we demonstrate that both the chemistry of the linker and the site of linkage affect the immune fingerprint and the kinetic solubility of these conjugated agonists. These results shed further light on the immunostimulatory potential of NOD2/TLR7 cross-activation and provide insights for designing innovative immune potentiators.

Capsules for Automated Azide-Alkyne Click Reactions

The development of an automated and reproducible process for copper-mediated click reactions of alkynes and azides into 1,4-disubstituted 1,2,3-triazole products is described. This method utilizes prepacked capsules that contain all necessary reagents and materials for the reaction and purification processes. The reaction and product isolation steps are fully automated with no further user involvement, resulting in the triazole products in high purity. The effectiveness of capsule-based automated organic synthesis was further demonstrated by sequencing the automated synthesis of organic azides, followed by a second capsule for CuAAC with no intermediate purification.

Alginate-based hydrogels mediated biomedical applications: A review

With the development in the field of biomaterials, research on alternative biocompatible materials has been initiated, and alginate in polysaccharides has become one of the research hotspots due to its advantages of biocompatibility, biodegradability and low cost. In recent years, with the further understanding of microscopic molecular structure and properties of alginate, various physicochemical methods of cross-linking strategies, as well as organic and inorganic materials, have led to the development of different properties of alginate hydrogels for greatly expanded applications. In view of the potential application prospects of alginate-based hydrogels, this paper reviews the properties and preparation of alginate-based hydrogels and their major achievements in delivery carrier, dressings, tissue engineering and other applications are also summarized. In addition, the combination of alginate-based hydrogel and new technology such as 3D printing are also involved, which will contribute to further research and exploration.

Click Chemistry for the Generation of Combination of Triazole Core and Thioether Donor Site in Organosulfur Ligands: Applications of Metal Complexes in Catalysis

During the last two decades, organosulfur compounds have been used in the field of transition metal catalysis. Some of such compounds are known for their ability to withstand their exposure to air and moisture. These compounds are very important ligands. They may be obtained using simple and smooth modular synthetic protocols which include nucleophilic substitution reactions. The development of click chemistry represents a new era of innovation. It is a lighthouse of reliable and efficient reactions. In recent past, click chemistry has also been applied for the synthesis of such organosulfur ligands specifically suited for the dynamic field of transition metal catalysis. In order to synthesize novel compounds containing sulfur and triazole ring, click chemistry is an advantageous methodology over other approaches. This article covers the general features and uses of this methodology for the development of catalytically active organosulfur compounds. The significant advances in the design of transition metal catalytic systems utilizing such ligands, their use in the catalysis of many chemical transformations are also covered in this article. Effort has also been made to present a comparative overview of the performances of such catalysts vis-à-vis the catalysts designed commonly used ligands. Catalytic performances have been discussed thoroughly in order to identify the impact of ligand architecture on efficacy of the catalyst. Effect of reaction conditions (such as time, temperature etc.) and mechanistic aspects have also been rationalized.

Photo-Clickable Triazine-Trione Thermosets as Promising 3D Scaffolds for Tissue Engineering Applications

There is an overwhelming demand for new scaffolding materials for tissue engineering (TE) purposes. Polymeric scaffolds have been explored as TE materials; however, their high glass transition state (Tg) limits their applicability. In this study, a novel materials platform for fabricating TE scaffolds is proposed based on solvent-free two-component heterocyclic triazine-trione (TATO) formulations, which cure at room temperature via thiol-ene/yne photochemistry. Three ester-containing thermosets, TATO-1, TATO-2, and TATO-3, are used for the fabrication of TE scaffolds including rigid discs, elastic films, microporous sponges, and 3D printed objects. After 14 days' incubation the materials covered a wide range of properties, from the soft TATO-2 having a compression modulus of 19.3 MPa and a Tg of 30.4 °C to the hard TATO-3 having a compression modulus of 411 MPa and a Tg of 62.5 °C. All materials exhibit micro- and nano-surface morphologies suited for bone tissue engineering, and in vitro studies found them all to be cytocompatible, supporting fast cell proliferation while minimizing cell apoptosis and necrosis. Moreover, bone marrow-derived mesenchymal stem cells on the surface of the materials are successfully differentiated into osteoblasts, adipocytes, and neuronal cells, underlining the broad potential for the biofabrication of TATO materials for TE clinical applications.

Metal-Free Synthesis of Polysubstituted Triazoloquinoxalines Using Alkynols as the Key Building Blocks

o-Phenylenediamines, o-nitroanilines, and Boc-o-phenylenediamines were converted to N-Ts/Ns-o-phenylenediamines, followed by Mitsunobu alkylation with prop-2-yn-1-ols. After one-pot azidation, the resulting intermediates underwent Huisgen cycloaddition, which yielded Ts/Ns-dihydrotriazoloquinoxalines. Cleavage of the arylsulfonyl moiety provided (dihydro)triazoloquinoxalines with the possibility of modifying the N 5 position. The application of but-3-yn-1-ols and pent-4-yn-1-ols allowed the preparation of benzotriazolodiazepines and benzotriazolodiazocines. The developed protocols enable the preparation of diversely substituted products from readily available starting materials under mild and metal-free conditions.

New Antibacterial and Antioxidant Chitin Derivatives: Ultrasonic Preparation and Biological Effects

This work focuses on the first use of ultrasonic phenol-ene coupling as a polymer analogous transformation. The ultrasonic reaction was introduced into chitin chemistry, resulting in the fast and convenient preparation of new water-soluble cationic chitin derivatives. Since water-soluble derivatives of fully deacetylated chitin are poorly described in the literature, the synthesis of each new type of these derivatives is a significant event in polysaccharide chemistry. Polycations, or cationic polymers, are of particular interest as antibacterial agents. Consequently, the resulting polymers were tested for their antibacterial activity and toxicity. We found that the highly substituted polymer of medium molecular weight exhibited the most pronounced in vitro antibacterial effect. We prepared nanoparticles using the ionic gelation technique. The most effective in vitro antibacterial chitin-based systems were tested in vivo in rats. These tests demonstrated outstanding antibacterial effects combined with an absence of toxicity. Additionally, we found that the resulting polymers, unlike their nanoparticle counterparts, also exhibited strong antioxidant effects. In summary, we demonstrated the effectiveness of ultrasound in polymer chemistry and highlighted the importance of the sonochemical approach in the chemical modification of polysaccharides. This approach enables the synthesis of derivatives with improved physicochemical and biological properties.

Unveiling a new strategy for PDIA1 inhibition: Integration of activity-based probes profiling and targeted degradation

The overexpression of PDIA1 in cancer has spurred the quest for effective inhibitors. However, existing inhibitors often bind to only one active site, limiting their efficacy. In our study, we developed a PROTAC-mimetic probe dPA by combining PACMA31 (PA) analogs with cereblon-directed pomalidomide. Through protein profiling and analysis, we confirmed dPA's specific interaction with PDIA1's active site cysteines. We further synthesized PROTAC variants with a thiophene ring and various linkers to enhance degradation efficiency. Notably, H4, featuring a PEG linker, induced significant PDIA1 degradation and inhibited cancer cell proliferation similarly to PA. The biosafety profile of H4 is comparable to that of PA, highlighting its potential for further development in cancer therapy. Our findings highlight a novel strategy for PDIA1 inhibition via targeted degradation, offering promising prospects in cancer therapeutics. This approach may overcome limitations of conventional inhibitors, presenting new avenues for advancing anti-cancer interventions.

Aggregable gold nanoparticles for cancer photothermal therapy

Photothermal therapy (PTT) is an important non-invasive cancer treatment method. Enhancing the photothermal conversion efficiency (PCE) of photothermal agents (PTAs) and prolonging their tumor accumulation and retention are effective strategies to enhance the efficiency of cancer PTT. Recently, tremendous progress has been made in developing stimuli-responsive aggregable gold nanoparticles as effective PTAs for PTT. In this review, we discuss the chemical principles underlying gold nanoparticle aggregation and highlight the progress in gold nanoparticle aggregation triggered by different stimuli, especially tumor microenvironment-related factors, for cancer PTT. Covalent condensation reactions, click cycloaddition reactions, chelation reactions, and Au-S bonding, as well as non-covalent electrostatic interactions, hydrophobic interactions, hydrogen bonding, and van der Waals forces play key roles in the aggregation of gold nanoparticles. Enzymes, pH, reactive oxygen species, small molecules, salts, and light drive the occurrence of gold nanoparticle aggregation. Targeted aggregation of gold nanoparticles prolongs tumor accumulation and retention of PTAs and improves PCE, resulting in enhanced tumor PTT. Moreover, the major challenges of aggregable gold nanoparticles as PTAs are pointed out and the promising applications are also prospected at the end. With the deepening of research, we expect aggregable gold nanoparticles to become essential PTAs for tumor therapy.

Electroresponsive Thiol-Yne Click-Hydrogels for Insulin Smart Delivery: Tackling Sustained Release and Leakage Control

Diabetes is a metabolic disorder caused by the body's inability to produce or use insulin. Considering the figures projected by the World Health Organization, research on insulin therapy is crucial. Hence, we present a soft biointerface based on a thiol-yne poly(ethylene glycol) (PEG) click-hydrogel as an advanced treatment option to administrate insulin. Most importantly, the device is rendered electroactive by incorporating biocompatible poly(3,4-ethylenedioxythiophene) nanoparticles (PEDOT NPs) as conductive moieties to precisely control the release of insulin over an extended period through electrochemical stimulation (ES). The device has been carefully optimized on account of: (i) the main interactions established between PEDOT- and PEG-based moieties, which have been studied by density functional theory calculations, and reveal the choice of 4-arm PEG precursors as most suitable cross-linkers; and (ii) the concentration of PEDOT NPs in the device, which has been determined considering minimal interference with the gelation process, as well as the resulting morphological, mechanical, electrochemical, and cytocompatible properties of the PEG-based click-hydrogels. Finally, the management over insulin delivery through ES is verified in vitro, with released insulin being detected by high-performance liquid chromatography. Overall, our hydrogel-based device establishes a method for controlled insulin delivery with the potential for translation to other relevant bioelectronic applications.

Stapling Cysteine[2,4] Disulfide Bond of α-Conotoxin LsIA and Its Potential in Target Delivery

α-Conotoxins, as selective nAChR antagonists, can be valuable tools for targeted drug delivery and fluorescent labeling, while conotoxin-drug or conotoxin-fluorescent conjugates through the disulfide bond are rarely reported. Herein, we demonstrate the [2,4] disulfide bond of α-conotoxin as a feasible new chemical modification site. In this study, analogs of the α-conotoxin LsIA cysteine[2,4] were synthesized by stapling with five linkers, and their inhibitory activities against human α7 and rat α3β2 nAChRs were maintained. To further apply this method in targeted delivery, the alkynylbenzyl bromide linker was synthesized and conjugated with Coumarin 120 (AMC) and Camptothecin (CPT) by copper-catalyzed click chemistry, and then stapled between cysteine[2,4] of the LsIA to construct a fluorescent probe and two peptide-drug conjugates. The maximum emission wavelength of the LsIA fluorescent probe was 402.2 nm, which was essentially unchanged compared with AMC. The cytotoxic activity of the LsIA peptide-drug conjugates on human A549 was maintained in vitro. The results demonstrate that the stapling of cysteine[2,4] with alkynylbenzyl bromide is a simple and feasible strategy for the exploitation and utilization of the α-conotoxin LsIA.

DNA/BSA interaction, anticancer, antimicrobial and catalytic applications of synthesis of nitro substituted pyrimidine-based Schiff base ligand capped nickel nanoparticles

The objective of this research was to create stable nickel nanoparticles using nickel chloride salt and a Schiff base ligand called DPMN. The synthesis process involved a two-step phase transfer procedure. Spectroscopic techniques such as UV-Visible and FT-IR were used to confirm the formation of ligand-stabilized nickel nanoparticles (DPMN-NiNPs). To analyze the size, surface morphology, and quality of DPMN-NiNPs, SEM and TEM techniques were utilized. In vitro studies were performed to investigate the potential anticancer activity of the synthesized compounds against three different cancer cell lines and one normal cell line, and the results were compared to those of cis-platin. The researchers also conducted tests to determine the ability of DPMN-NiNPs to bind to CT-DNA using various techniques such as electronic absorption, fluorescence, viscometric, and cyclic voltammetric. The results showed that the synthesized DPMN-NiNPs exhibited good DNA binding ability, which was further validated by denaturation of DNA using thermal and sonochemical methods. The researchers also investigated the antimicrobial and antioxidant activities of DPMN-NiNPs, which demonstrated better biological activities than DPMN alone. Furthermore, the synthesized nano compounds were found to selectively damage cancer cell lines without harming normal cell lines. Finally, the researchers examined the potential of DPMN-NiNPs as a catalyst in dye degradation by testing its ability to decompose methyl red dye using UV-Visible spectroscopy.Communicated by Ramaswamy H. Sarma.

Click Chemistry: Reaction Rates and Their Suitability for Biomedical Applications

Click chemistry has become a commonly used synthetic method due to the simplicity, efficiency, and high selectivity of this class of chemical reactions. Since their initial discovery, further click chemistry methods have been identified and added to the toolbox of click chemistry reactions for biomedical applications. However, selecting the most suitable reaction for a specific application is often challenging, as multiple factors must be considered, including selectivity, reactivity, biocompatibility, and stability. Thus, this review provides an overview of the benefits and limitations of well-established click chemistry reactions with a particular focus on the importance of considering reaction rates, an often overlooked criterion with little available guidance. The importance of understanding each click chemistry reaction beyond simply the reaction speed is discussed comprehensively with reference to recent biomedical research which utilized click chemistry. This review aims to provide a practical resource for researchers to guide the selection of click chemistry classes for different biomedical applications.

Click Chemistry in Polymersome Technology

Polymersomes, self-assembled nanoparticles composed of amphiphilic block copolymers, have emerged as promising versatile nanovesicles with various applications, such as drug delivery, medical imaging, and diagnostics. The integration of click chemistry reactions, specifically the copper [I]-catalysed azide-alkyne cycloaddition (CuAAC), has greatly expanded the functionalisation and bioconjugation capabilities of polymersomes and new drugs, being this synergistic combination explored in this review. It also provides up-to-date examples of previous incorporations of click-compatible moieties (azide and alkyne functional groups) into polymer building blocks, enabling the "click" attachment of various functional groups and ligands, delving into the diverse range of click reactions that have been reported and employed for polymersome copolymer synthesis and the modification of polymersome surfaces, including ligand conjugation and surface modification. Overall, this review explores the current state-of-the-art of the combinatory usage, in recent years, of polymersomes with the click chemistry reaction, highlighting examples of studies of their synthesis and functionalisation strategies.

Synthesis of Unsymmetrically Condensed Benzo- and Thienotriazologermoles

Germoles and siloles unsymmetrically condensed with heteroaromatic units are attracting much interest. In this study, compounds containing a triazologermole core unit condensed with a benzene or thiophene ring were prepared. Thienotriazologermole was subjected to bromination to obtain the bromide, which underwent transformation via the palladium-catalyzed Stille coupling reaction to form triphenylamine-substituted thienotriazolegermole, with an effective extension of conjugation. The electronic states and properties of these triazologermole derivatives are discussed on the basis of optical and electrochemical measurements and density functional theory calculations. Triphenylamine-substituted thienotriazolegermole showed clear solvatochromic properties in photoluminescence measurements, suggesting that intramolecular charge transfer occurs at the photo-excited state. This clearly indicates that the triazologermole unit is useful as an acceptor of donor-acceptor compounds. The potential application of triphenylamine-substituted thienotriazolegermole as a sensing material was also explored.

Poly(2-(dimethylamino)ethyl methacrylate)-Grafted Amphiphilic Block Copolymer Micelles Co-Loaded with Quercetin and DNA

The synergistic effect of drug and gene delivery is expected to significantly improve cancer therapy. However, it is still challenging to design suitable nanocarriers that are able to load simultaneously anticancer drugs and nucleic acids due to their different physico-chemical properties. In the present work, an amphiphilic block copolymer comprising a biocompatible poly(ethylene glycol) (PEG) block and a multi-alkyne-functional biodegradable polycarbonate (PC) block was modified with a number of poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) side chains applying the highly efficient azide-alkyne "click" chemistry reaction. The resulting cationic amphiphilic copolymer with block and graft architecture (MPEG-b-(PC-g-PDMAEMA)) self-associated in aqueous media into nanosized micelles which were loaded with the antioxidant, anti-inflammatory, and anticancer drug quercetin. The drug-loaded nanoparticles were further used to form micelleplexes in aqueous media through electrostatic interactions with DNA. The obtained nanoaggregates-empty and drug-loaded micelles as well as the micelleplexes intended for simultaneous DNA and drug codelivery-were physico-chemically characterized. Additionally, initial in vitro evaluations were performed, indicating the potential application of the novel polymer nanocarriers as drug delivery systems.

Preparation, Biological Evaluation, and First-in-Human Single-Photon Emission Computed Tomography (SPECT) Study of 99mTc-Labeled Prostate-Specific Membrane Antigen (PSMA)-Targeted Radiotracers Containing Triazole with Reduced Kidneys Accumulation

Prostate-specific membrane antigen (PSMA), a well-established biological marker for prostate cancer (PCa) imaging and therapy, is overexpressed on the surface of prostate cancer lesions. In this study, a triazole ring was introduced into the linker by click chemistry to generate a HYNIC-derived ligand (T), which exhibited good PSMA affinity (Ki = 2.23 nM). Eight stable 99mTc-labeled complexes, [99mTc]Tc-T-Mn (n = 1-8), with hydrophilic properties were synthesized by incorporating different coligands at high radiochemical yields and purities without purification. The radioligands were concentrated in the kidneys of healthy Kunming male mice and were significantly blocked by the PSMA inhibitor ZJ-43. The uptake of the optimized complex [99mTc]Tc-T-M2 was correlated with PSMA, and it had good PSMA affinity (Kd = 5.42 nM). [99mTc]Tc-T-M2 accumulated on LNCaP (PSMA++) tumors and was significantly blocked by ZJ-43 at 2 h p.i., indicating high PSMA specificity. Relatively suitable kidney uptake was beneficial for reducing kidneys exposure in patients. SPECT/CT imaging of [99mTc]Tc-T-M2 in LNCaP (PSMA++) or 22Rv1 (PSMA+) tumor-bearing mice revealed high tumor uptake, low background uptake (especially low kidney uptake (49.06 ± 9.20 %ID/g) at 2 h p.i.), and obvious inhibition by ZJ-43, whereas PC-3 (PSMA-) tumors were undetectable. A freeze-dried [99mTc]Tc-T-M2 kit was successfully developed (T-M2 kit). Preliminary clinical trials showed that [99mTc]Tc-T-M2 clearly identified small prostate cancer lesions and has potential for clinical application.

Poly-pharmacology of existing drugs: How to crack the code?

Drug development in oncology is highly challenging, with less than 5% success rate in clinical trials. This alarming figure points out the need to study in more details the multiple biological effects of drugs in specific contexts. Indeed, the comprehensive assessment of drug poly-pharmacology can provide insights into their therapeutic and adverse effects, to optimize their utilization and maximize the success rate of clinical trials. Recent technological advances have made possible in-depth investigation of drug poly-pharmacology. This review first highlights high-throughput methodologies that have been used to unveil new mechanisms of action of existing drugs. Then, we discuss how emerging chemo-proteomics strategies allow effectively dissecting the poly-pharmacology of drugs in an unsupervised manner.

Expedient Azide-Alkyne Huisgen Cycloaddition Catalyzed by a Combination of VOSO4 with Cu(0) in Aqueous Media

A series of vanadium(III), vanadyl(IV/V) species, inorganic metal oxides, and transition-metal oxides was examined as cocatalysts with Cu(0) powder for copper(I)-catalyzed azide-alkyne cycloaddition. Among them, vanadyl(IV) species bearing acetylacetonate, acetate, and sulfate, vanadyl(V) isopropoxide, and vanadate were suitable for the click reactions of per-acetyl and per-benzyl β-azido glycosides with three different terminal alkynes in CH3CN. Water-soluble vanadyl(IV) sulfate was further selected for efficient click reactions for unprotected β-glycosyl azides and even compatible with a thiol-containing substrate in aqueous media at ambient temperature.

Chitosan-based hydrogels: From preparation to applications, a review

Chitosan, derived from the deacetylation of chitin, is an abundant natural biopolymer on earth. Chitosan and its derivatives have become promising biological materials because of their unique molecular structure and excellent biological activities. The reactive functional groups of chitosan such as the amino and hydroxyl groups play a crucial role in facilitating the synthesis of three-dimensional hydrogel. Chitosan-based hydrogels have been widely used in medical, pharmaceutical, and environmental fields for years. Nowadays, chitosan-based hydrogels have been found in a wide range of applications in the food industry such as food sensors, dye adsorbents and nutrient carriers. In this review, recently developed methods for the preparation of chitosan-based hydrogels were given, and the biological activities of chitosan-based hydrogels were systematically introduced. Additionally, the recent progress in food sensors, packaging, dye adsorbents, and nutrient carriers was discussed. Finally, the challenges and prospects for the future development of chitosan-based hydrogels were discussed.

Temperature-Sensitive Materials for Oil and Gas Drilling Applications

With the vigorous development of the petroleum industry, improving the efficiency of oil and gas exploitation has become an important issue. Temperature-sensitive materials show great potential for application in the development and production of oil and gas fields due to their unique temperature-responsive properties. This paper reviews the application of temperature-sensitive materials in oil and gas drilling and introduces the characteristics of three types of temperature-sensitive materials: N-substituted acrylamide polymers, amphiphilic block copolymers, and peptides. Because these materials can change their physical state at specific temperatures, this paper discusses in detail the role of various temperature-sensitive materials as plugging agent, thickener, oil displacing agent, flocculant, and tackifier in oil and gas field operations, as well as the mechanism of action and performance of temperature-sensitive materials in practical oil and gas drilling operations. As we have not yet seen relevant similar literature, this paper aims to discuss the innovative application of temperature-sensitive materials in the oil and gas drilling process, and at the same time points out the problems in the current research and applications as well as future development directions. Through analysis and comparison, we provide an efficient and environmentally friendly materials selection option for the petroleum industry in order to promote the progress and sustainable development of oil and gas extraction processes.

"Clickable" graphene nanoribbons for biosensor interfaces

We report on the synthesis of "clickable" graphene nanoribbons (GNRs) and their application as a versatile interface for electrochemical biosensors. GNRs are successfully deposited on gold-coated working electrodes and serve as a platform for the covalent anchoring of a bioreceptor (i.e., a DNA aptamer), enabling selective and sensitive detection of Interleukin 6 (IL6). Moreover, when applied as the intermediate linker on reduced graphene oxide (rGO)-based field-effect transistors (FETs), the GNRs provide improved robustness compared to conventional aromatic bi-functional linker molecules. GNRs enable an orthogonal and covalent attachment of a recognition unit with a considerably higher probe density than previously established methods. Interestingly, we demonstrate that GNRs introduce photoluminescence (PL) when applied to rGO-based FETs, paving the way toward the simultaneous optical and electronic probing of the attached biointerface.

Fibronectin Connecting Cell Sheet Based on Click Chemistry for Wound Repair

As a living repair material, cell sheet exhibits significant potential in wound repair. Nonetheless, wound healing is a complicated and protracted process that necessitates specific repair functions at each stage, including hemostasis and antibacterial activity. In this work, on the basis of harvesting the cell sheet via a photothermal response strategy, a fibronectin attached cell sheet (FACS) is prepared to enhance its wound repair capability. For this purpose, the azide group (N3 ) is initially tagged onto the cell surface through metabolic glycoengineering of unnatural sugars, and then the conjugate (DBCO-fibronectin) comprises of the dibenzocyclooctyne (DBCO) and fibronectin with multiple wound repair functions is linked to N3 using click chemistry. Biological evaluations following this demonstrates that the FACS preparation exhibits excellent biocompatibility, and the fibronectin modification enhances the capacity for cell proliferation and migration. Moreover, in vivo wound healing experiment confirms the reparative efficacy of FACS. It not only has a wound closure rate 1.46 times that of a conventional cell sheet but also reduces inflammatory cell infiltration, promotes hair follicle and blood vessel regeneration, and encourages collagen deposition. This strategy holds enormous clinical potential and paves the way for advanced functional modifications of cell sheets.

Clicking in harmony: exploring the bio-orthogonal overlap in click chemistry

In the quest to scrutinize and modify biological systems, the global research community has continued to explore bio-orthogonal click reactions, a set of reactions exclusively targeting non-native molecules within biological systems. These methodologies have brought about a paradigm shift, demonstrating the feasibility of artificial chemical reactions occurring on cellular surfaces, in the cell cytosol, or within the body - an accomplishment challenging to achieve with the majority of conventional chemical reactions. This review delves into the principles of bio-orthogonal click chemistry, contrasting metal-catalyzed and metal-free reactions of bio-orthogonal nature. It comprehensively explores mechanistic details and applications, highlighting the versatility and potential of this methodology in diverse scientific contexts, from cell labelling to biosensing and polymer synthesis. Researchers globally continue to advance this powerful tool for precise and selective manipulation of biomolecules in complex biological systems.

Rational Design of L-RNA Aptamer-Peptide Conjugate for Efficient Cell Uptake and G-quadruplex-Mediated Gene Control

RNA G-quadruplexes (D-rG4s) are prevalent in the transcriptome and play crucial regulatory roles in various biological processes. Recently, L-RNA aptamers have been reported to recognize functional rG4s with a strong binding affinity and specificity. However, owing to the poor cell penetration capacity of L-RNA aptamers, their biological applications are currently limited. Herein, we rationally design an L-RNA aptamer-peptide conjugate, Tamra_Ahx_R8_L-Apt.4-1c, which can efficiently translocate into the cytosol and target the rG4 of interest. Notably, we demonstrate diverse regulatory roles of Tamra_Ahx_R8_L-Apt.4-1c on rG4 motif present in different regions of mRNAs and further expand the application in different cell lines. Our novel and biocompatible conjugate enhances the cellular uptake of the L-RNA aptamer, and our robust strategy enables non-canonical RNA structures to be targeted by L-RNA aptamers for gene control in cells.

Click chemistry-aided drug discovery: A retrospective and prospective outlook

Click chemistry has emerged as a valuable tool for rapid compound synthesis, presenting notable advantages and convenience in the exploration of potential drug candidates. In particular, in situ click chemistry capitalizes on enzymes as reaction templates, leveraging their favorable conformation to selectively link individual building blocks and generate novel hits. This review comprehensively outlines and introduces the extensive use of click chemistry in compound library construction, and hit and lead discovery, supported by specific research examples. Additionally, it discusses the limitations and precautions associated with the application of click chemistry in drug discovery. Our intention for this review is to contribute to the development of a modular synthetic approach for the rapid identification of drug candidates.

Green Approach Toward Triazole Forming Reactions for Developing Anticancer Drugs

Compounds containing triazole have many significant applications in the dye and ink industry, corrosion inhibitors, polymers, and pharmaceutical industries. These compounds possess many antimicrobial, antioxidant, anticancer, antiviral, anti-HIV, antitubercular, and anticancer activities. Several synthetic methods have been reported for reducing time, minimizing synthetic steps, and utilizing less hazardous and toxic solvents and reagents to improve the yield of triazoles and their analogues synthesis. Among the improvement in methods, green approaches towards triazole forming biologically active compounds, especially anticancer compounds, would be very important for pharmaceutical industries as well as global research community. In this article, we have reviewed the last five years of green chemistry approaches on click reaction between alkyl azide and alkynes to install 1,2,3-triazole moiety in natural products and synthetic drug-like molecules, such as in colchicine, flavanone cardanol, bisphosphonates, thiabendazoles, piperazine, prostanoid, flavonoid, quinoxalines, C-azanucleoside, dibenzylamine, and aryl-azotriazole. The cytotoxicity of triazole hybrid analogues was evaluated against a panel of cancer cell lines, including multidrug-resistant cell lines.

1-Butyl-3-methylimidazolium tetrafluoroborate as suitable solvent for BF3: the case of alkyne hydration. Chemistry vs electrochemistry

In order to replace the expensive metal/ligand catalysts and classic toxic and volatile solvents, commonly used for the hydration of alkynes, the hydration reaction of alkynes was studied in the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate (BMIm-BF4) adding boron trifluoride diethyl etherate (BF3·Et2O) as catalyst. Different ionic liquids were used, varying the cation or the anion, in order to identify the best one, in terms of both efficiency and reduced costs. The developed method was efficaciously applied to different alkynes, achieving the desired hydration products with good yields. The results obtained using a conventional approach (i.e., adding BF3·Et2O) were compared with those achieved using BF3 electrogenerated in BMIm-BF4, demonstrating the possibility of obtaining the products of alkyne hydration with analogous or improved yields, using less hazardous precursors to generate the reactive species in situ. In particular, for terminal arylalkynes, the electrochemical route proved to be advantageous, yielding preferentially the hydration products vs the aldol condensation products. Importantly, the ability to recycle the ionic liquid in subsequent reactions was successfully demonstrated.

γ-Functional Iminiumthiolactones for the Single and Double Modification of Peptides

Thiolactones (TL) can be readily incorporated into polymeric materials and have been extensively used as a ligation strategy despite their limited reactivity toward amine-containing substrates. Comparatively, iminiumthiolactones (ITL) are much more reactive, yet to this day, only the nonsubstituted ITL known as Traut's reagent is commercially available and used. In this work, we advance current TL/ITL chemistry by introducing reactive side groups to the ITL heterocycle in the γ-position, which can be orthogonally modified without affecting the ITL heterocycle itself. To study the reactivity of γ-functional ITLs, we subject one of our derivatives (γ-allyl-functional ITL 3b) to model reactions with several peptides and a chosen protein (lysozyme C). Using mild reaction conditions, we successfully demonstrate that the γ-functional ITL exhibits orthogonal and enhanced reactivity in a single or double modification while introducing a new functional handle to the biological substrate. We believe that γ-functional ITLs will advance the original Traut chemistry and open promising opportunities for the bioconjugation of biological building blocks to existing functional molecules, polymers, and materials.

Glutathione Mediates Control of Dual Differential Bio-orthogonal Labelling of Biomolecules

Traditional approaches to bio-orthogonal reaction discovery have focused on developing reagent pairs that react with each other faster than they are metabolically degraded. Glutathione (GSH) is typically responsible for the deactivation of most bio-orthogonal reagents. Here we demonstrate that GSH promotes a Cu-catalysed (3+2) cycloaddition reaction between an ynamine and an azide. We show that GSH acts as a redox modulator to control the Cu oxidation state in these cycloadditions. Rate enhancement of this reaction is specific for ynamine substrates and is tuneable by the Cu:GSH ratio. This unique GSH-mediated reactivity gradient is then utilised in the dual sequential bio-orthogonal labelling of peptides and oligonucleotides via two distinct chemoselective (3+2) cycloadditions.

Glutathione Mediates Control of Dual Differential Bio-orthogonal Labelling of Biomolecules

Traditional approaches to bio-orthogonal reaction discovery have focused on developing reagent pairs that react with each other faster than they are metabolically degraded. Glutathione (GSH) is typically responsible for the deactivation of most bio-orthogonal reagents. Here we demonstrate that GSH promotes a Cu-catalysed (3+2) cycloaddition reaction between an ynamine and an azide. We show that GSH acts as a redox modulator to control the Cu oxidation state in these cycloadditions. Rate enhancement of this reaction is specific for ynamine substrates and is tuneable by the Cu:GSH ratio. This unique GSH-mediated reactivity gradient is then utilised in the dual sequential bio-orthogonal labelling of peptides and oligonucleotides via two distinct chemoselective (3+2) cycloadditions.

Podophyllotoxin: Recent Advances in the Development of Hybridization Strategies to Enhance Its Antitumoral Profile

Podophyllotoxin is a naturally occurring cyclolignan isolated from rhizomes of Podophyllum sp. In the clinic, it is used mainly as an antiviral; however, its antitumor activity is even more interesting. While podophyllotoxin possesses severe side effects that limit its development as an anticancer agent, nevertheless, it has become a good lead compound for the synthesis of derivatives with fewer side effects and better selectivity. Several examples, such as etoposide, highlight the potential of this natural product for chemomodulation in the search for new antitumor agents. This review focuses on the recent chemical modifications (2017-mid-2023) of the podophyllotoxin skeleton performed mainly at the C-ring (but also at the lactone D-ring and at the trimethoxyphenyl E-ring) together with their biological properties. Special emphasis is placed on hybrids or conjugates with other natural products (either primary or secondary metabolites) and other molecules (heterocycles, benzoheterocycles, synthetic drugs, and other moieties) that contribute to improved podophyllotoxin bioactivity. In fact, hybridization has been a good strategy to design podophyllotoxin derivatives with enhanced bioactivity. The way in which the two components are joined (directly or through spacers) was also considered for the organization of this review. This comprehensive perspective is presented with the aim of guiding the medicinal chemistry community in the design of new podophyllotoxin-based drugs with improved anticancer properties.

An Integrative Bioorthogonal Nanoengineering Strategy for Dynamically Constructing Heterogenous Tumor Spheroids

Although tumor models have revolutionized perspectives on cancer aetiology and treatment, current cell culture methods remain challenges in constructing organotypic tumor with in vivo-like complexity, especially native characteristics, leading to unpredictable results for in vivo responses. Herein, the bioorthogonal nanoengineering strategy (BONE) for building photothermal dynamic tumor spheroids is developed. In this process, biosynthetic machinery incorporated bioorthogonal azide reporters into cell surface glycoconjugates, followed by reacting with multivalent click ligand (ClickRod) that is composed of hyaluronic acid-functionalized gold nanorod carrying dibenzocyclooctyne moieties, resulting in rapid construction of tumor spheroids. BONE can effectively assemble different cancer cells and immune cells together to construct heterogenous tumor spheroids is identified. Particularly, ClickRod exhibited favorable photothermal activity, which precisely promoted cell activity and shaped physiological microenvironment, leading to formation of dynamic features of original tumor, such as heterogeneous cell population and pluripotency, different maturation levels, and physiological gradients. Importantly, BONE not only offered a promising platform for investigating tumorigenesis and therapeutic response, but also improved establishment of subcutaneous xenograft model under mild photo-stimulation, thereby significantly advancing cancer research. Therefore, the first bioorthogonal nanoengineering strategy for developing dynamic tumor models, which have the potential for bridging gaps between in vitro and in vivo research is presented.

"Click Chemistry": An Emerging Tool for Developing a New Class of Structural Motifs against Various Neurodegenerative Disorders

Click chemistry is a set of easy, atom-economical reactions that are often utilized to combine two desired chemical entities. Click chemistry accelerates lead identification and optimization, reduces the complexity of chemical synthesis, and delivers extremely high yields without undesirable byproducts. The most well-known click chemistry reaction is the 1,3-dipolar cycloaddition of azides and alkynes to form 1,2,3-triazoles. The resulting 1,2,3-triazoles can serve as both bioisosteres and linkers, leading to an increase in their use in the field of drug discovery. The current Review focuses on the use of click chemistry to identify new molecules for treating neurodegenerative diseases and in other areas such as peptide targeting and the quantification of biomolecules.

Click Chemistry and Radiochemistry: An Update

The term "click chemistry" describes a class of organic transformations that were developed to make chemical synthesis simpler and easier, in essence allowing chemists to combine molecular subunits as if they were puzzle pieces. Over the last 25 years, the click chemistry toolbox has swelled from the canonical copper-catalyzed azide-alkyne cycloaddition to encompass an array of ligations, including bioorthogonal variants, such as the strain-promoted azide-alkyne cycloaddition and the inverse electron-demand Diels-Alder reaction. Without question, the rise of click chemistry has impacted all areas of chemical and biological science. Yet the unique traits of radiopharmaceutical chemistry have made it particularly fertile ground for this technology. In this update, we seek to provide a comprehensive guide to recent developments at the intersection of click chemistry and radiopharmaceutical chemistry and to illuminate several exciting trends in the field, including the use of emergent click transformations in radiosynthesis, the clinical translation of novel probes synthesized using click chemistry, and the advent of click-based in vivo pretargeting.

Molecular Hybridization of Alkaloids Using 1,2,3-Triazole-Based Click Chemistry

Alkaloids found in multiple species, known as 'driver species', are more likely to be included in early-stage drug development due to their high biodiversity compared to rare alkaloids. Many synthetic approaches have been employed to hybridize the natural alkaloids in drug development. Click chemistry is a highly efficient and versatile reaction targeting specific areas, making it a valuable tool for creating complex natural products and diverse molecular structures. It has been used to create hybrid alkaloids that address their limitations and serve as potential drugs that mimic natural products. In this review, we highlight the recent advancements made in modifying alkaloids using click chemistry and their potential medicinal applications. We discuss the significance, current trends, and prospects of click chemistry in natural product-based medicine. Furthermore, we have employed computational methods to evaluate the ADMET properties and drug-like qualities of hybrid molecules.

α-Aminobisphosphonate Copolymers Based on Poly(ε-caprolactone)s and Poly(ethylene glycol): A New Opportunity for Actinide Complexation

Original α-aminobisphosphonate-based copolymers were synthesized and successfully used for actinide complexation. For this purpose, poly(α-chloro-ε-caprolactone-co-ε-caprolactone)-b-poly(ethylene glycol)-b-poly(α-chloro-ε-caprolactone-co-ε-caprolactone) copolymers were first prepared by ring-opening copolymerization of ε-caprolactone (εCL) and α-chloro-ε-caprolactone using poly(ethylene glycol) (PEG) as a macro-initiator and tin(II) octanoate as a catalyst. The chloride functions were then converted to azide moieties by chemical modification, and finally α-aminobisphosphonate alkyne ligand (TzBP) was grafted using click chemistry, to afford well-defined poly(αTzBPεCL-co-εCL)-b-PEG-b-poly(αTzBPεCL-co-εCL) copolymers. Three copolymers, showing different α-aminobisphosphonate group ratios, were prepared (7, 18, and 38%), namely, CP8, CP9, and CP10, respectively. They were characterized by 1H and 31P NMR and size exclusion chromatography. Sorption properties of these copolymers were evaluated by isothermal titration calorimetry (ITC) with neodymium [Nd(III)] and cerium [Ce(III)] cations, used as surrogates of actinides, especially uranium and plutonium, respectively. ITC enabled the determination of the full thermodynamic profile and the calculation of the complete set of thermodynamic parameter (ΔH, TΔS, and ΔG), with the Ka constant and the n stoichiometry. The results showed that the number of cations sorbed by the functional copolymers logically increased with the number of bisphosphonate functions borne by the macromolecular chain, independently of the complexed cation. Additionally, CP9 and CP10 copolymers showed higher sorption capacities [21.4 and 34.0 mg·g-1 for Nd(III) and 9.6 and 14.3 mg·g-1 for Ce(III), respectively] than most of the systems previously described in the literature. CP9 also showed a highest binding constant (7000 M-1). These copolymers, based on non-toxic and biocompatible poly(ε-caprolactone) and PEG, are of great interest for external body decontamination of actinides as they combine high number of complexing groups, thus leading to great decontamination efficiency, and limited diffusion through the skin due to their high-molecular weight, thus avoiding additional possible internal contamination.