An Enzyme-Free Amperometric Sensor Based on Self-Assembling Ferrocene-Conjugated Oligopeptide for Specific Determination of L-Arginine

An enzyme-free amperometric sensor based on a heptadecapeptide possessing an electroactive ferrocene (Fc) linker as ferrocene-Gly-Gly-Gly-Gly-Phe-Gly-His-Ile-His-Glu-Gly-Tyr-Gly-Gly-Gly-Gly-Lys-(CH₂)₄-dithiocyclopentane self-assembled on gold substrate was designed and fabricated for specific determination of L-arginine (L-Arg). The detection mechanism is based on conformational change of surface-immobilized peptide induced by the target L-Arg, which was confirmed via SEM, TEM, AFM, XPS, and SPR studies. The binding affinity and the recognition feasibility of immobilized specific and non-specific peptides were also assessed using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and differential pulse voltammetry (DPV). The proposed method can serve as “signal-on” sensor for detection of L-Arg down to 31 pmol/L with broad linear range (0.0001 to 10 μmol/L). Furthermore, the Fc-conjugated specific peptide sensor was successfully applied to the determination of L-Arg in pig serums with a recovery rate of 97.5%—106.9%, and its test results are in good agreement with that of chromatographic instrument, evidencing that the oligopeptide-based sensor can be served as a simple and enzyme-free biosensing platform towards L-Arg for future application.