Gold nanodome SERS platform for label-free detection of protease activity

Surface-enhanced Raman scattering provides a promising technology for sensitive and selective detection of protease activity by monitoring peptide cleavage. Not only are peptides and plasmonic hotspots similarly sized, Raman fingerprints also hold large potential for spectral multiplexing. Here, we use a gold-nanodome platform for real-time detection of trypsin activity on a CALNNYGGGGVRGNF substrate peptide. First, we investigate the spectral changes upon cleavage through the SERS signal of liquid-chromatography separated products. Next, we show that similar patterns are detected upon digesting surface-bound peptides. We demonstrate that the relative intensity of the fingerprints from aromatic amino acids before and after the cleavage site provides a robust figure of merit for the turnover rate. The presented method offers a generic approach for measuring protease activity, which is illustrated by developing an analogous substrate for endoproteinase Glu-C.