Electrochemical impedance spectroscopy study of proteolysis using unmodified gold nanoparticles

• Sensitive detection of proteolysis using gold nanoparticles is achieved.
• The peptide is designed as protease substrate and barrier of electrochemical species.
• Determination of trypsin in human serum and urine samples is studied.

Proteases are involved in numerous cell functions and abnormal proteolysis may lead to a diversity of serious diseases. Herein, a simple electrochemical method is developed to study proteolysis by employing unmodified gold nanoparticles (AuNPs). Substrate of a protease is modified on a gold disk electrode, forming a barrier for electrochemical species and reflecting a significant charge transfer resistance (Rct). After the proteolysis process, the substrate can be cleaved coupled with the decline of Rct. The electrical properties of the substrate residues on the electrode may also change, leading to the subsequent adsorption of AuNPs. Due to the excellent electrical conductivity of AuNPs, Rct can be further decreased, which can be used to reveal the proteolysis process. The proposed method allows the determination of the model protease, trypsin, with desirable sensitivity and specificity. It may also hold great potential use in the study of other proteolysis processes and some biomedical applications in the future.

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