Dipeptidyl peptidase-IV activity assay and inhibitor screening using a gold nanoparticle-modified gold electrode with an immobilized enzyme substrate

We report on an electrochemical biosensor for the determination of the activity of dipeptidyl peptidase-IV (DPP-IV), and on a method for screening the effect of its inhibitors. An enzyme substrate (Fc-peptide) was immobilized on the surface of a gold electrode, and double signal amplification was accomplished via an additional layer consisting of phenyl rings and gold nanoparticles. The activity of DPP-IV was determined at levels as low as 39 nU·mL −1 and over a linear detection range as wide as from 0.5 μU·mL −1 to 2.5 mU·mL −1 . The inhibitory effects of diprotin A and the His-Leu dipeptide on the activity of DPP-IV also were tested and gave IC 50 values of 93.5 and 95.5 μM, respectively. The assay is rapid, precise and selective. It may be extended to other peptidases and, possibly, proteases and their inhibitors. Graphical abstract An electrochemical biosensor for the determination of dipeptidyl peptidase-IV activity and the screening of its inhibitors was established. The substrate was immobilized on a gold electrode surface, and double signal amplification was accomplished via phenyl ring layer and gold nanoparticles.