Fast surface immobilization of native proteins through catalyst-free amino-yne click bioconjugation

Surface immobilization provides a useful platform for biosensing, drug screening, tissue engineering and other chemical and biological applications. However, some of the used reactions are inefficient and/or complicated, limiting their applications in immobilization. Herein, we use a spontaneous and catalyst-free amino-yne click bioconjugation to generate activated ethynyl group functionalized surfaces for fast immobilization of native proteins and cells. Biomolecules, such as bovine serum albumin (BSA), human IgG and a peptide of C(RGDfK), could be covalently immobilized on the surfaces in as short as 30 min. Notably, the bioactivity of the anchored biomolecules remains intact, which is verified by efficiently capturing target antibodies and cells from the bulk solutions. This strategy represents an alternative for highly efficient surface biofunctionalization.

Fast surface immobilization of native bioconjugates through a spontaneous amino-yne click reaction is realized.     

Azide-alkyne click polymerization: An update

The great achievements of click chemistry have encouraged polymer scientists to use this reaction in their field.This review assembles an update of the advances of using azide-alkyne click polymerizati...     

Synthesis of PNIPAM polymer brushes on reduced graphene oxide based on click chemistry and RAFT polymerization

Preparation and characterization of poly(N‐isopropylacrylamide) (PNIPAM) polymer brushes on the surfaces of reduced graphene oxide (RGO) sheets based on click chemistry and reversible addition‐fragmentation chain transfer (RAFT) polymerization was reported. RGO sheets prepared by thermal reduction were modified by diazonium salt of propargyl p‐aminobenzoate, and alkyne‐functionalized RGO sheets were obtained. RAFT chain transfer agent (CTA) was grafted to the surfaces of RGO sheets by click reaction. PNIPAM on RGO sheets was prepared by RAFT polymerization. Fourier transform‐infrared spectroscopy, thermogravimetric analysis, X‐ray photoelectron spectroscopy, and transmission electron microscopy (TEM) results all demonstrated that RAFT CTA and PNIPAM were successfully produced on the surfaces of RGO sheets. Nanosized PNIPAM domains on RGO sheets were observed on TEM. Micro‐DSC result indicated that in aqueous solution PNIPAM on RGO sheets presented a lower critical solution temperature at 33.2 °C. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Recyclable Cu nanoparticle catalyzed azide-alkyne click polymerization

The Cu(I)-catalyzed alkyne-azide cycloaddition(CuAAC) has been developed into a powerful polymerization reaction for the synthesis of new polytriazoles with versatile properties. However, research on recyclable and reusable copper catalyst for click polymerization to meet the requirement of green chemistry was rarely reported. Copper nanoparticles were reported to be capable catalysts for CuAAC. Replacing conventional copper catalyst with copper nanoparticles may realize the recycle and reuse of the copper catalyst in click polymerization. In this paper, copper nanoparticles were prepared and used as an effective catalyst for click polymerization, and soluble polytriazoles with high molecular weights were obtained in excellent yields under optimized reaction conditions. Importantly, the copper nanoparticles can be recycled and reused for up to 11 times for the click polymerization. Moreover, introducing aggregation-induced emission(AIE)-active moiety of tetraphenylethylene into the monomers makes the resultant polymers retain the AIE feature. This work not only provides an efficient recyclable catalytic system for the azide-alkyne click polymerization, but also might inspire polymer chemists to use recyclable copper species to catalyze other polymerizations.     

Synthesis of an insulated molecular wire by click polymerization

We developed a new method for the synthesis of an organic-soluble insulated molecular wire (IMW) with permethylated cyclodextrin (PMCD); this method involves click polymerization of linked [2]rotaxane containing azide and alkynyl groups at both ends of a π-conjugated guest.     

Semiconducting polymer thin films by surface-confined stepwise click polymerization

Surface-confined stepwise click polymerization was used to prepare surface-attached thin films of semiconducting polymers. These highly uniform films showed extended UV/vis absorption characteristics and a remarkable degree of molecular organization with a unidirectional alignment of the polymer chains normal to the surface.     

Effective strategy for polymer synthesis: multicomponent reactions and click polymerization

The rational selection of organic reactions in polymer synthesis is an important research content of polymer science. In recent years, multicomponent reaction as an efficient and green synthesis method has attracted the wide attention of researchers, injecting new and powerful vitality into the field of polymer synthesis. In the study of multicomponent reaction, researchers found the intersection of multicomponent reaction and click chemistry and put forward the concept of Multicomponent Click Reaction (MCR-Click), which is a kind of Multicomponent Reaction with high activity, atomic economy, and some green chemical properties. The application of MCR in polymer chemistry is reviewed in this paper. It is expected that this reaction will arouse the attention of polymer chemists and play a new role in polymer science.     

Tadpole‐shaped amphiphilic copolymers prepared via RAFT polymerization and click reaction

The tadpole‐shaped amphiphilic copolymers with cyclic polystyrene as the head and a linear poly(N‐isopropylacrylamide) as the tail have been successfully synthesized by combination of reversible addition‐fragmentation chain transfer (RAFT) polymerization and “click” reaction. The synthesis involves two main steps: (1) preparation of a linear acetylene‐terminated PNIPAAM‐b‐PS with a side azido group anchored at the junction between two blocks; (2) intramolecular cyclization reaction to produce the cyclic PS block using “click” chemistry under high dilution. The structures, molecular weights, and molecular weight distributions of the resulted intermediates and the target polymers were characterized by their ¹H NMR, FTIR, and gel permeation chromatography. The difference of surface property between tadpole‐shaped polymer and its linear precursor was observed, and the water contact angles on the former surface are larger than that of the latter surface. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2390–2401, 2008     

Biotinylated thermoresponsive core cross-linked nanoparticles via RAFT polymerization and "click" chemistry

A straightforward approach to the synthesis of "clickable" thermoresponsive core cross-linked (CCL) nanoparticles was developed. This approach was based on reversible addition-fragmentation chain transfer (RAFT) radical cross-linking polymerization of styrene and divinylbenzene with azide-functionalized poly(N-isopropylacrylamide) (PNIPAM-N(3)) as macro chain transfer agent in a selective solvent. Spherical nanoparticles with a diameter of 12nm were obtained after 24h polymerization. When the lyophilized CCL nanoparticles were dispersed in THF, spherical nanoparticles were observed, confirming the stability of CCL nanoparticles. The transmission electron microscopy (TEM) studies demonstrated that spherical nanoparticles and wormlike structure coexisted in the aqueous solution. The CCL nanoparticles have a lower critical solution temperature (LCST) at about 29.6°C, a little lower than that of PNIPAM homopolymer. Biotin molecules were conjugated to the surface of CCL nanoparticles via "click" chemistry in aqueous media. After bioconjugation, the LCST shifted to 28.3°C. The bioavailability of biotin to protein avidin was evaluated by a 4'-hydroxyazobenzene-2-carboxylic acid/avidin (HABA/avidin) binding assay and TEM.     

Self-healing hyperbranched polytriazoles prepared by metal-free click polymerization of propiolate and azide monomers

The last decade has witnessed the quick develop of self-healing materials. As a newborn strategy, the alternative of irreversible covalent bond formation is, however, to be further developed. In this paper, self-healing hyperbranched poly(aroxycarbonyltriazole) based on such mechanism were prepared by our developed metal-free click polymerization of simplified dipropiolate and triazide. Thanks to their excellent processability and film-forming ability, high quality homogeneous films free from defects were obtained by casting. The cut films could be healed by stacking or pressing the halves together at room temperature and elevated temperature. Thus, this design concept for self-healing materials should be generally applicable to other hyperbranched polymers with reactive groups on their peripheries.     

Towards copper-free nanocapsules obtained by orthogonal interfacial "click" polymerization in miniemulsion

A facile method to produce nanocapsules by copper-free interfacial "click"-polymerization as orthogonal reaction for the encapsulation of functional molecules is successfully performed using stable miniemulsion droplets. Difunctional azides and alkynes have been used for polymerization around the miniemulsion droplets, leading to the formation of nanocapsules. The results were compared with copper-catalyzed systems.     

Cyclodextrin-centred star polymers synthesized via a combination of thiol-ene click and ring opening polymerization

The synthesis of cyclodextrin-centred star polymers via thiol-ene addition of per-6-thio-β-cyclodextrin (CD-(SH)(7)) with vinyl terminated polymers is described. The obtained thiol-ene product was employed as an initiator for ring opening polymerization (ROP) of ε-caprolactone (ε-CL).     

Versatile grafting approaches to star-shaped POSS-containing hybrid polymers using RAFT polymerization and click chemistry

An alkyne-bearing polyhedral oligomeric silsesquioxane (POSS) core was used to prepare POSS-containing polymer hybrids using 'grafting to' or 'grafting from' strategies in combination with reversible chain transfer and click chemistry.     

Combination of ring-opening polymerization and "click" chemistry towards functionalization of aliphatic polyesters

Azide pendent groups of aliphatic polyesters have been derivatized into tertiary amines, ammonium salts and poly(ethylene oxide) grafts. The experimental conditions have been optimized (organic solvent, 35 degrees C), such that the aliphatic polyesters are not degraded, including even poly(lactide) which is very sensitive to attack by weak nucleophiles.     

Preparation of novel beta-cyclodextrin chiral stationary phase based on click chemistry

A facile strategy based on click chemistry for preparation of the structurally well-defined native beta-cyclodextrin (beta-CD) based chiral stationary phase (CSP) was proposed. The beta-CD CSP was evaluated by enatioseparation of benzoin, trans-stilbene oxide, Troger's base, bendroflumethiazide, ketoprofen, chlorthalidone, three flavanone compounds and two beta-adrenergic blocking agents under reversed phase high performance liquid chromatography. The chromatographic results demonstrate the chiral separation ability of click beta-CD CSP and illustrate the usefulness of click chemistry in the preparation of beta-CD based CSP.     

A new azide staining reagent based on "click chemistry"

A new staining reagent was prepared and its ability to stain several azide-containing agents on TLC plates was determined.     

An ultra-sensitive electrochemical sensor for ascorbic acid based on click chemistry

A highly selective and sensitive electrochemical sensor for ascorbic acid (AA) assay has been prepared through Cu(I) catalyzed azide-alkyne cycloaddition reaction (CuAAC). The catalyst, Cu(I) species, is acquired from the reduction of Cu(II) by AA in situ. In the presence of Cu(I) catalyst, the azide modified Au electrode surface is shown to react quantitatively with terminal propargyl-functionalized ferrocene forming 1,2,3-triazoles. The electrochemical response of propargyl-functionalized ferrocene modified Au electrode surface can be monitored using differential pulse voltammetry (DPV) technique. Under optimal conditions, it is found that the current intensity has a linear relationship with the logarithm of AA concentration in the range of 5.0 × 10(-12) to 1.0 × 10(-9) M. Furthermore, the proposed electrochemical sensor shows a good stability (RSD 4.2%), high selectivity and low detection limit for AA detection. In addition, it also demonstrates that the proposed sensor can be applied to detect AA in real urine samples with satisfactory results.     

Synthesis of degradable molecular brushes via a combination of ring-opening polymerization and click chemistry

Acid-degradable molecular brushes with polycarbonate backbone and densely grafted side chains (∼1.9 SCs per backbone repeating unit) were synthesized for the first time using the grafting-onto method. Extremely efficient copper-catalyzed azide-alkyne cycloaddition click reactions between the polycarbonate backbone containing two pendant azido groups per backbone unit and alkynyl-terminated poly (methyl acrylate) (ay-PMA₇₂, average degree of polymerization DP = 72) SCs were demonstrated to finish in 10 min with a quantitative conversion of the azido groups. Similar grafting efficiencies were also achieved when using alkynyl-terminated polystyrene (ay-PS), poly(ethylene oxide) (ay-PEO), and poly (t-butyl acrylate)-b-polystyrene (ay-PtBA-b-PS) to successfully prepare molecular brushes with high grafting density (>1.8 SCs per backbone repeating unit). Under acidic condition, the polycarbonate backbones were completely degradable and the final degraded product of the molecular brushes was a linear polymer chain with molecular weight two times of the SCs. When a mixture of hydrophobic ay-PS and hydrophilic ay-PEO chains was used, amphiphilic heterobrushes PC-g-(PS-co-PEO) were synthesized, which could self-assemble into micelles or vesicles in selective solvents, depending on the ratio of the two SCs in the brush. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 239–248     

Proximity-induced amino-yne reaction for selective MDM4 conjugation via propargylated sulfonium

Whilst most bioorthogonal reactions focus on targeting binding-site cysteine residues, proximity-induced reactivity effect ensures that reaction also occurs at nucleophilic lysine residues. We report one example here that the propargylated-sulfonium center undergoes a nucleophilic reaction with lysine residue via proximity-induced conjugation. This propargylated-sulfonium tethered peptide resulting from a facile propargylation of thiolethers, enables amino-yne reaction at the selected lysine on MDM4 protein. This strategy represents a viable approach of lysine-targeted covalent inhibition in proximity.     

Retardation of spontaneous polymerization of formaldehyde by acidic substances

The stability of liquid formaldehyde produced by pyrolysis of α-polyoxymethylene was studied in connection with the presence of impurities in the monomer. Liquid monomer was divided into several fractions by means of the distillation. The stability of each fraction for polymerization is dependent on the order of fraction, that is, the monomer obtained in the early fractions of distillation was much more stable with regard to polymerization than later distillate. Analyses of the monomer fractions indicated that various impurities such as carbon dioxide, water, methanol, and methyl formate were present in the early monomer distillates. From the influence of these impurities on the stability of liquid formaldehyde, it was found that small amounts of carbon dioxide and hydrogen cyanide noticeably depressed the polymerization, and that with acetic acid and maleic anhydride the rate of polymerization decreased with small amounts of these compounds but increased with an excess of additive. On the other hand, the addition of these acidic substances did not affect the molecular weight of the polymer produced. From the fact that the acidic substance retards only the initiation of polymerization, it has been concluded that the spontaneous polymerization of formaldehyde in bulk or in toluene solution is initiated by an anionic species.