concanavalin-a and benzeneboronic-acid

Functional multilayer thin films have been prepared by layer-by-layer (LbL) deposition for the development of sensors, separators, and drug delivery systems. In particular, glucose-sensitive LbL films have been widely studied for use as glucose sensors and in glucose-triggered drug delivery systems. In this work, I report on glucose-sensitive LbL films that consist of concanavalin A (ConA), phenylboronic acid (PBA), and glucose oxidase (GOx). ConA/glycogen LbL films were prepared by LbL deposition of ConA and glycogen through a lectin-sugar interaction. Similarly, PBA-modified poly(amidoamine) dendrimer/poly(vinyl alcohol) (PVA) LbL films were prepared through cyclic boronate ester bonds. Both types of films decomposed in the presence of glucose, by the competitive binding of glucose, although these LbL films did not show a satisfactory response to millimolar concentrations of glucose under physiological conditions. PBA-modified poly(allylamine hydrochloride) and PVA films were prepared on a GOx-modified quartz slide. The LbL film was stable over a wide pH range, from 3.0 to 9.0, in the absence of glucose. In contrast, the film decomposed upon exposure to 0.1-10 mM glucose solutions for 60 min at pH 7.4. The glucose-induced decomposition of the film can be explained by the scission of the carbon-boron bond of the PBA residues by hydrogen peroxide, which was produced through the GOx-catalyzed oxidation of glucose. These results suggest this multilayer film may be useful for the development of glucose-sensitive drug delivery systems.

Topics: Boronic Acids; Capsules; Concanavalin A; Glucose; Nanocomposites; Technology, Pharmaceutical

A dithiolated random copolymer with pendent phenylboronic acid residues (Cys-Poly(3-acrylamidophenylboronic acid-co-2-dimethylaminopropyl methacrylamide), Cys-Poly(APBA-co-DMAPMA)) obtained by photo-iniferter method was accumulated as a polymer brush on a cap-shaped gold particles deposited on a vacuum-evaporated gold film, and the usefulness of the polymer brush as a sensing element for glycoprotein, ovalbumin (OVA), was examined by using UV-vis spectroscopy with a help of surface plasmon resonance. A similar system was constructed with a dithiolated mannose-carrying polymer, dithiolated-poly(2-methacryloyloxyethyl-D-mannopyranoside) (DT-PMEMan), prepared by the atom transfer radical polymerization (ATRP). The brush composed of this polymer was examined as a sensing element for lectin, concanavalin A (Con A). The sensor cells modified with Cys-Poly(APBA-co-DMAPMA) and DT-PMEMan showed a concentration-dependent binding of OVA and Con A, respectively, with a comparable detection limit to those with a monolayer of polymer brush-coated gold particle deposited on a glass substrate. Using this system, it can be expected to open a new perspective to various functional polymer brushes fixed to the cap-shaped gold particle on a solid substrate.

Topics: Acrylamides; Adsorption; Biosensing Techniques; Boronic Acids; Calcium; Carbohydrates; Concanavalin A; Gold; Lectins; Manganese; Microspheres; Ovalbumin; Polymers; Spectrophotometry, Ultraviolet; Surface Plasmon Resonance; Surface Properties

An artificial receptor and a signal transducer have been engineered on a lectin (saccharide-binding protein) surface by a post-photoaffinity labeling modification method. Saccharide binding can be directly and selectively read out by the fluorescence changes of the fluorophore via photoinduced electron transfer (PET) mode. Fluorescence titration with various saccharides reveals that molecular recognition by the artificial receptor is successfully coupled to the native binding site of the lectin, producing a novel fluorescent saccharide biosensor showing modulated specificity and enhanced affinity. Designed cooperativity between artificial and native molecular recognition modules was quantitatively demonstrated by the comparison of the binding affinities, and it represents a new strategy in molecular recognition. By using appropriate artificial receptors and various native lectins, this approach may provide many new semisynthetic biosensors for saccharide derivatives such as glycolipids and glycopeptides/proteins. An extended library of lectin-based biosensors is envisioned to be useful for glycome research, a newly emerging field of the post-genomic era.

Topics: Binding Sites; Biosensing Techniques; Boronic Acids; Concanavalin A; Fluorescent Dyes; Lectins; Models, Molecular; Monosaccharides; Naphthalenesulfonates; Polysaccharides; Spectrometry, Fluorescence

Nonporous, microparticulate, monodisperse silicas with particle diameters between 0.7 and 2.1 microns are introduced as stationary phases in high-performance affinity chromatography. The immobilization of m-aminophenylboronic acid, p-aminobenzamidine, tri-L-alanine, and concanavalin A onto these silicas was successfully achieved using 3-isothiocyanatopropyl-triethoxysilane as an activation reagent. Immobilized phenylboronic acid was applied to the isolation of nucleosides, nucleotides, and glycoprotein hormones such as bovine follicotropin and human chorionic gonadotropin, while immobilized benzamidine was employed for the isolation of the serine proteases thrombin and trypsin, immobilized tri-L-alanine for the separation of pig pancreatic elastase and human leukocyte elastase, and immobilized concanavalin A for the isolation of horseradish peroxidase. In all affinity chromatographic systems studied, the nonporous monodisperse silicas showed improved chromatographic performance compared to results obtained with porous silica supports using identical activation and immobilization procedures. Furthermore, frontal analysis was used as a method to evaluate the influence of experimental parameters on biological activity and accessible ligand densities. Only minor changes in bioactivity were found with the nonporous affinity supports, where accessibilities were typically higher than ca. 60%. The immobilization of affinity ligands onto porous supports as used in this and associated papers thus represents a successful general procedure for the preparation of stable matrices with fast kinetics for use in high-performance affinity chromatography.

Topics: Alanine; Amidines; Benzamidines; Boronic Acids; Chromatography, High Pressure Liquid; Concanavalin A; Electrophoresis, Polyacrylamide Gel; Indicators and Reagents; Isothiocyanates; Kallikreins; Ligands; Microspheres; Plasminogen; Silanes; Silicon; Silicon Dioxide; Thrombin