Detection of enzymatic activity by means of a diffraction-based biosensor.

We demonstrate here, for the first time, the capability of a diffraction-based sensor to detect enzyme activity and provide a simple measure of enzyme kinetics. Patterned samples of mouse IgG were exposed to the enzyme trypsin and the progress of enzymatic degradation of IgG was followed by measuring the decrease in diffraction signal intensity as a function of time. The diffraction signal intensity decreased exponentially as a function of time over a range of trypsin concentrations from 2-100 microg mL(-1). Atomic-force microscope images of the samples before and after exposure to trypsin show that the thickness of patterned protein is greatly reduced by the enzyme action, providing useful insight into the mechanism of signal change for the diffraction sensor.