Functional graphene by thiol-ene click chemistry.
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ABSTRACT:
SUBMITTER: Luong ND
PROVIDER: S-EPMC6174942 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Functionalization of pristine graphene to achieve high water dispersibility remains as a key obstacle owing to the high hydrophobicity and absence of reactive functional groups on the graphene surface. Herein, a green and simple modification approach to prepare highly dispersible functionalized graphene via thermal thiol-ene click reaction was successfully demonstrated on pristine graphene. Specific chemical functionalities (-COO, -NH2 and -S) on the thiol precursor (L-cysteine ethyl ester) were clicked directly on the sp2 carbon of graphene framework with grafting density of 1 unit L-cysteine per 113 carbon atoms on graphene. This functionalized graphene was confirmed with high atomic content of S (4.79 at % S) as well as the presence of C-S-C and N-H species on the L-cysteine functionalized graphene (FG-CYS). Raman spectroscopy evidently corroborated the modification of graphene to FG-CYS with an increased intensity ratio of D and G band, ID/IG ratio (0.3 to 0.7), full-width at half-maximum of G band, FWHM [G] (20.3 to 35.5) and FWHM [2D] (64.8 to 90.1). The use of ethanol as the reaction solvent instead of common organic solvents minimizes the chemical hazards exposure to humans and the environment. This direct attachment of multifunctional groups on the surface of pristine graphene is highly demanded for graphene ink formulations, coatings, adsorbents, sensors and supercapacitor applications.
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Project description:A versatile and rapid synthetic strategy has been developed for the on-resin cyclization of peptides using thiol-ene photochemistry. This unique method exploits the thiol group of natural cysteine amino acids and allows for various alkenes to be incorporated orthogonal to the peptide backbone.
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Project description:Diacylglycerols (DAGs) are a subclass of neutral lipids actively involved in cell signaling and metabolism. Alteration in DAG metabolism has been associated with onset and progression of several human-related diseases. The structural diversity of DAGs and their low concentrations in biological samples call for the development of methods that are capable of sensitive identification and quantitation of each DAG species as well as rapid profiling when a biochemical pathway is perturbed. In this work, the thiol-ene click chemistry has been employed to introduce a charge-tag, namely, cysteamine (CA), at a carbon-carbon double bond (C═C) of unsaturated DAGs. This one-pot photochemical derivatization is fast (within 1 min), universal (monotagging) for DAGs varying in fatty acyl chain lengths and the number of C═Cs, and suitable for small sample volume (e.g., 1-50 μL plasma). Because of the presence of the amine group in CA, tagged DAGs showed at least 10 times increase in response to electrospray ionization as compared to conventional ammonium adduct formation. Low-energy collision-induced dissociation of CA tagged DAGs allowed confident assignment of fatty acyl composition. A neutral loss scan based on characteristic 95 Da loss (a combined loss of CA and H2O) of tagged DAGs has been established as a sensitive means for unsaturated DAG detection (limit of detection = 100 pM) and quantitation from mixtures. The analytical utility of CA tagging was demonstrated by shotgun analysis of unsaturated DAGs in human plasma, including samples from type 2 diabetes mellitus patients.
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Project description:Daylight-activated detoxifying nanofibrous membranes (LDNMs) are fabricated by grafting benzophenone-3,3',4,4'-tetracarboxylic dianhydride (BD) and biological thiols successively on poly(vinyl alcohol-co-ethylene) (EVOH) nanofibrous membrane. Taking the merits of photoactivity of BD, high-reactivity of biological thiols, and high specific surface area and porosity of the nanofibrous membrane, 1,3-dichloropropene (1,3-D) can be efficiently detoxified on the LDNMs under daylight irradiation via a thiol-ene click reaction. The detoxification function of the LDNMs is "switched on" by light irradiation and continues by following a cascade of chemical attacks of thiyl radicals formed during the photoexcitation process. The resultant LDNMs present rapid detoxification rate (i.e., t1/2 =~30 min) and massive detoxification amount (i.e., ~12 mg/g) against 1,3-D vapor under ambient conditions. More importantly, the LDNMs perform a detoxification tailing effect after moving the light-irradiated membrane to a dark environment, thus ensuring the protective function in the absence of sufficient light sources. The detoxification property of the LDNMs in an outdoor environment with sunlight irradiation shows comparable results to the lab-scale outcomes, enabling them to serve as innovative materials for personal protective equipment in practical applications. The successful fabrication of LDNMs may inspire new insights into the design of protective materials providing aggressive protection.
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Project description:Bioconjugation based on crosslinking primary amines to carboxylic acid groups has found broad applications in protein modification, drug development, and nanomaterial functionalization. However, proteins, which are made up of amino acids, typically give nonselective bioconjugation when using primary amine-based crosslinking. In order to control protein orientation and activity after conjugation, selective bioconjugation is desirable. We herein report an efficient and cysteine-selective thiol-ene click reaction-based bioconjugation strategy using colloidal nanoparticles. The resulting thiol-ene based aptamer and enzyme nanoconjugates demonstrated excellent target binding ability and enzymatic activity, respectively. Thus, thiol-ene click chemistry can provide a stable and robust crosslinker in a biocompatible manner for bioconjugation of any thiol-containing biomolecule with nanomaterials. This will open more opportunities for applications of thiol-ene reactions and functional colloidal nanoparticles in chemical biology.
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Project description:UV-nanoimprint lithography (UV-NIL) is a promising technique for direct fabrication of functional oxide nanostructures. Since it is mostly carried out in aerobic conditions, the free radical polymerization during imprinting is retarded due to the radical scavenging ability of oxygen. Therefore, it is highly desirable to have an oxygen-insensitive photo-curable resin that not only alleviates the requirement of inert conditions but also enables patterning without making substantial changes in the process. Here we demonstrate the formulation of metal-containing resins that employ oxygen-insensitive thiol-ene photo-click chemistry. Allyl acetoacetate (AAAc) has been used as a bifunctional monomer that, on one hand, chelates with the metal ion, and on the other hand, offers a reactive alkene group for polymerization. Pentaerythritol tetrakis(3-mercaptopropionate) (PETMP), a four-arm thiol derivative, is used as a crosslinker as well as an active component in the thiol-ene photo-click chemistry. The FT-IR analyses on the metal-free and metal-containing resin formulations revealed that the optimum ratio of alkene to thiol is 1 : 0.5 for an efficient photo-click chemistry. The thiol-ene photo-click chemistry has been successfully demonstrated for direct imprinting of oxides by employing TiO2 and Ta2O5 as candidate systems. The imprinted films of metal-containing resins were subjected to calcination to obtain the corresponding patterned metal oxides. This technique can potentially be expanded to other oxide systems as well.
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Project description:The photoinitiated radical reactions between thiols and alkenes/alkynes (thiol-ene and thiol-yne chemistry) have been applied to a functionalization methodology to produce carbohydrate-presenting surfaces for analyses of biomolecular interactions. Polymer-coated quartz surfaces were functionalized with alkenes or alkynes in a straightforward photochemical procedure utilizing perfluorophenylazide (PFPA) chemistry. The alkene/alkyne surfaces were subsequently allowed to react with carbohydrate thiols in water under UV-irradiation. The reaction can be carried out in a drop of water directly on the surface without photoinitiator, and any disulfide side products were easily washed away after the functionalization process. The resulting carbohydrate-presenting surfaces were evaluated in real-time studies of protein-carbohydrate interactions using a quartz crystal microbalance (QCM) flow-through system with recurring injections of selected lectins, with intermediate regeneration steps using low pH buffer. The resulting methodology proved fast, efficient and scalable to high-throughput analysis formats, and the produced surfaces showed significant protein binding with expected selectivities of the lectins used in the study.
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Project description:Dendritic materials possessing urethane linkage are surprisingly more stable than similar structures having functional groups such as ether, ester, amide, or carbosilane. This generates profound interest in dendritic polyurethanes. Construction of a well-defined polyurethane dendrimer is, however, challenging because of isocyanates' high reactivity. As a model of our ongoing dendrimer-research, herein, we report a protecting group-free one-pot multicomponent Curtius reaction to furnish a robust and versatile AB2-type dendron, which ensures late-stage modification of both the dendron and dendritic macromolecule yielding a surface functionalized polyurethane dendrimer. While 5-hydroxyisophthalic acid, 11-bromoundecanol, and 4-penten-1-ol were utilized in the construction of the dendron, thiol-ene click chemistry was employed for the late-stage modification. Novel dendrons and dendrimers synthesized were characterized by NMR (1D and 2D) and high-resolution MALDI-TOF analysis. This strategy allows an easy late-stage modification of dendritic macromolecules and is highly useful in the synthesis of both symmetrical and unsymmetrical dendrimers (Janus dendrimers).
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Project description:The assembly of microgel building blocks into 3D scaffolds is an emerging strategy for tissue engineering. A key advantage is that the inherent microporosity of these scaffolds provides cells with a more permissive environment than conventional nanoporous hydrogels. Here, norbornene-bearing poly(ethylene glycol) (PEG) based microgels are assembled into 3D cell-instructive scaffolds using a PEG-dithiol linker and thiol-ene click photopolymerization. The bulk modulus of these materials depends primarily on the crosslink density of the microgel building blocks. However, the linker and initiator concentrations used during assembly have significant effects on cell spreading and proliferation when human mesenchymal stem cells (hMSCs) are incorporated in the scaffolds. The cell response is also affected by the properties of the modular microgel building blocks, as hMSCs growing in scaffolds assembled from stiff but not soft microgels activate Yes-associated protein signaling. These results indicate that PEG microgel scaffolds assembled via thiol-ene click chemistry can be engineered to provide a cell-instructive 3D milieu, making them a promising 3D platform for tissue engineering.
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