Biosensor based on enzyme-catalysed degradation of thin polymer films

Abstract

A biosensor based on the enzyme-catalysed dissolution of biodegradable polymer films has been developed. Three polymer–enzyme systems were investigated for use in the sensor: a poly(ester amide), which is degraded by the proteolytic enzyme α-chymotrypsin; a dextran hydrogel, which is degraded by dextranase; and poly(trimethylene) succinate, which is degraded by a lipase. Dissolution of the polymer films was monitored by Surface Plasmon Resonance (SPR). The rate of degradation was directly related to enzyme concentration for each polymer/enzyme couple. The poly(ester amide)/α-chymotrypsin couple proved to be the most sensitive over a concentration range from 4×10 −11 to 4×10 −7 mol l −1 of enzyme. The rate of degradation was shown to be independent of the thickness of the poly(ester amide) films. The dextran hydrogel/dextranase couple was less sensitive than the poly(ester amide)/α-chymotrypsin couple but showed greater degradation rates at low enzyme concentrations. Enzyme concentrations as low as 2×10 −11 mol l −1 were detected in less than 20 min. Potential fields of application of such a sensor system are the detection of enzyme concentrations and the construction of disposable enzyme based immunosensors, which employ the polymer-degrading enzyme as an enzyme label.