NFF-3 TFA, the peptide, is a selective MMP substrate. NFF-3 TFA selectively binds to MMP-3 and MMP-10 to be hydrolyzed. NFF-3 TFA is also cleaved by trypsin, hepatocyte growth factor activator, and factor Xa. Label NFF-3 TFA with a CyDye pair, Cy3/Cy5Q, can produce fluorescence in cell assays to detect cell activity.