Trypsin Detection Using Electrochemical Reduction‐based Redox Cycling

Abstract

It is more difficult to obtain high signal‐to‐background ratios in biosensors using electrochemical reduction than using electrochemical oxidation. Here, we present a method for trypsin detection using electrochemical reduction‐based redox cycling. Electrochemical‐enzymatic (EN) redox cycling and electrochemical‐chemical (EC) redox cycling for trypsin detection were tested and compared. Trypsin cleaves a peptide bond in an electrochemically inactive p‐aminophenol (AP)‐conjugated oligopeptide, and this cleavage results in the release of electrochemically active AP, which is involved in EN and EC redox‐cycling reactions. Horseradish peroxidase and cytochrome c (Cyt c) were tested as redox enzymes for EN redox cycling involving a redox enzyme and H2O2. Cyt c was better than horseradish peroxidase, as its use resulted in lower background levels. The trypsin detection based on the EN redox cycling involving Cyt c and H2O2 (~50 ng/mL) exhibited lower detection limits than the detection based on EC redox cycling involving IO3− (~100 ng/mL), because of higher signal levels.