A transducer based on enzyme-induced degradation of thin polymer films monitored by surface plasmon resonance

A novel transducer based on the dissolution of biodegradable polymer films as a direct result of enzymatic reaction has been developed. Three polymers were investigated for use in the transducer: a poly(ester amide), which is degraded by the proteolytic enzyme alpha-chymotrypsin; a dextran hydrogel, which is degraded by dextranase; and poly(trimethylene) succinate, which is degraded by a lipase. Degradation of the polymer films was monitored by surface plasmon resonance (SPR) and impedance measurements. SPR was shown to be suitable for a greater variety of materials, since it does not require the polymer film to be electrically insulating. Rate of degradation was shown to be directly related to enzyme concentration for each polymer/enzyme couple. The poly(ester amide)/alpha-chymotrypsin couple proved to be the most sensitive. Degradation of the films was complete in less than 20 min for enzyme concentrations greater than 9 x 10(-9) mol dm-3. Enzyme concentrations as low as 4 x 10(-11) mol dm-3 were detected in less than 30 min. The transducer has great potential for the detection of enzyme concentrations as well as for use in immunosensing where the enzyme degrading the polymer would be the enzyme label.