Detection of enzyme activity through catalytic signal amplification with functionalized gold nanoparticles

A cascade of two catalytic events was used to detect enzyme activity: When a peptide substrate acting as an inhibitor for a catalytic gold nanoparticle was hydrolyzed by an enzyme, the catalytic activity of the nanoparticle was restored, and a large amount of a yellow reporter molecule was produced (see picture; S=substrate, P=product). The assay can be made selective for a particular enzyme by changing the inhibitory peptide. (Chemical Equation Presented). © 2011 Wiley-VCH Verlag GmbH & Co. KGaA.