Kinetics of dissolution of Concanavalin A/Dextran sols in response to glucose measured by surface plasmon resonance

Abstract

The dissolution of highly viscous dispersions composed of complexes of Concanavalin A (Con A) and high molecular-weight dextran (2000 kDa) in response to glucose was studied by using surface plasmon resonance (SPR). The viscous property of Con A/dextran sols is based on intermolecular affinity bonds between dextran and Con A. These receptor/ligand cross-linkages can be reversibly cleaved by the competing analyte glucose, resulting in a sol with a strongly reduced viscosity. We tested the concept of using the kinetics of sol dissolution as an analytical tool for glucose determination. Under this premise, a thin layer of the Con A/dextran dispersion was placed on the gold surface of a novel SPR-probe. The sol's dissolution, when placed in contact with bulk solutions of various glucose concentrations, was monitored by measuring the shift of resonance angle. An increased rate of sol dissolution at increasing levels of glucose concentration was found, presumably due to a decrease of the sol viscosity which led to a faster diffusion and mass transport of the sol components into the bulk solution. The thickness of the sol layer turned out to be the rate-limiting step of the dissolution kinetics. Other factors such as sugar specificity and temperature had a significant affect on the kinetics of sol dissolution also. However, matrix effects of the test solution effected the overall kinetics of the solution only to a minimal extent, rendering the method interesting for biosensing purposes.