Interaction of wheat germ agglutinin with an N-acetylglucosamine-carrying telomer brush accumulated on a colloidal gold monolayer

Interactions of N-acetyl-D-glucosamine-conjugated silk fibroin with lectins, cytoskeletal proteins and cardiomyocytes

We have reported that cytoskeletal proteins such as desmin and vimentin are expressed on the surface of muscle, mesenchymal and cancer cells, and possess N-acetyl-β-D-glucosamine (β-GlcNAc) residue-binding properties. As cell-recognizable β-GlcNAc residue-bearing biopolymer, we prepared glycoconjugates (SF-GlcNAc) composed of silk fibroin (SF) and monosaccharide N-acetyl-D-glucosamine (GlcNAc) by chemical modification using cyanuric chloride. The covalent immobilization of GlcNAc into SF was assessed by ¹H-NMR measurements. The ¹H-NMR spectrum of SF-GlcNAc conjugates showed new peaks attributed to the methyl protons of the N-acetyl group in GlcNAc, and the integration of these peaks revealed that the GlcNAc content in the conjugates was 9 wt%. The existence of β-GlcNAc residues in SF-GlcNAc was examined by the criteria using lectins such as wheat germ agglutinin (WGA). Addition of WGA to SF-GlcNAc solution caused an increase in the turbidity of the solution due to lectin-mediated aggregation. Solid-phase lectin binding assay based on the biotin-avidin interaction showed that biotinylated succinylated WGA bound more strongly onto SF-GlcNAc conjugate-coated wells compared to SF-coated well. Following the establishment of the existence of β-GlcNAc residues in SF-GlcNAc, the interaction of SF-GlcNAc with desmin was examined by enzyme-linked immunosorbent assay using anti-desmin antibody. The stronger binding of desmin was observed for SF-GlcNAc conjugate-coated wells compared to SF-coated wells. The use of SF-GlcNAc conjugates as a substrate for culturing desmin-expressing human cardiac myocytes demonstrated an increase in the numbers of attached cells and proliferating cells on the conjugate-coated wells compared to SF-coated wells. These results suggest that the immobilization of monosaccharide GlcNAc is a useful method for the versatile functionalization of SF as an application in tissue engineering.

Purification of synthetic oligonucleotides via catching by polymerization

This unit describes the purification of synthetic oligodeoxyribonucleotides (ODN) using a catching-by-polymerization approach. In a crude ODN, the major impurity is the failure sequences generated in the coupling step of each synthetic cycle. They are difficult to remove due to the similarity of their physical properties to the full-length sequences. Two non-chromatographic methods are described in the unit to solve the problem. In the first one, during automated synthesis, the failure sequences are tagged with a methacrylamide group, which is polymerizable and can participate in acrylamide radical polymerization reactions; the full-length sequences are not tagged. After synthesis, the crude mixture is subjected to polymerization. The failure sequences are incorporated into an insoluble polymer; the full-length sequences are extracted with water. In the second method, the full-length sequences are tagged with a methacrylamide group via a cleavable linker; the failure sequences are not tagged. After synthesis, the full-length sequences are incorporated into a polymer; the failure sequences are washed away with water. Pure full-length sequences are cleaved from the polymer. The two methods are complementary. .

End-linked, amphiphilic, degradable polymer conetworks: synthesis by sequential atom transfer radical polymerization using a bifunctional, cleavable initiator

End-linked amphiphilic conetworks prepared using an ATRP bifunctional, bis(hemiacetal ester) initiator were hydrolyzed by HCl, yielding novel amphiphilic star copolymers.

Anti-biofouling properties of a telomer brush with pendent glucosylurea groups

A thiol-group-carrying telomer with pendent D-glucosylurea groups [poly(glucosylureaethyl methacrylate)-SH (PolyGUMA-SH)] was obtained by reversible addition-fragmentation chain-transfer (RAFT) polymerization of GUMA in the presence of 4,4'-azobis(4-cyanopentanoic acid) (initiator) and 4-cyanopentanoic acid dithiobenzoate (chain-transfer agent) and subsequent reduction with NaBH4. The thiol-carrying telomer was accumulated on both a gold electrode and a colloidal gold-immobilized glass substrate as proven by cyclic voltammetry using hydroquinone as a probe, and the increase in absorbance at 550 nm was ascribable to localized surface plasmon resonance (LSPR), respectively. The adsorption of various proteins to the surface of the telomer brush was examined by the LSPR method, too. The PolyGUMA brush showed a significant resistance against nonspecific adsorption of proteins, such as lysozyme, bovine serum albumin, immunoglobulin G, and fibrinogen. Furthermore, sugar-binding proteins, concanavalin A (Con A, with an affinity for mannose and glucose) and wheat germ agglutinin (WGA, with an affinity for N-acetylglucosamine), were not adsorbed to the GUMA-carrying brush, which is in contrast with the prompt and distinct binding of these proteins to the telomer brushes composed of 2-methacryloyloxyethyl D-glucopyranoside (Con A) and 1-O-(6'-methacrylamido)hexyl-2-N-acetoamido-2-deoxy-D-glucopyranoside residues (WGA). The glucosylurea-group-carrying telomer brush prepared here might be quite useful to provide a "bio-inert (anti-biofouling)" surface in biomedical fields.