Multimode spectral-like electrochemical fingerprinting of cysteine via biomimetic electrocatalytic interface

A breakthrough multimode spectral-like electrochemical profiling platform for cysteine (Cys) detection and discrimination, enabled by a rationally designed enzyme-mimetic interface that mimics the reversible Cys/cystine conversion cycle is presented. The sensing architecture was constructed through synergistic integration of vitamin B12 comodification with electrochemical activation involving sequential oxidation and reduction treatments on a glassy carbon electrode (GCE). Detailed characterization techniques, including electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy, systematically elucidated the formation mechanism of the bioinspired catalytic interface. The engineered interface achieves ultralow potential oxidation of Cys with simultaneous reversible reduction of oxidation products. In addition to low potential (0 V) and highly sensitive current-time (i-t) amperometric detection (with a linear range of 1 µM-1.8 mM and a detection limit of 0.1 µM), this unique interface enables multimode spectral-like discrimination via negative differential pulse voltammetric (DPV) fingerprinting (with a linear range of 1 μM-10 mM and a detection limit of 0.5 μM), effectively resolving Cys from structurally similar thiols. The superhydrophilic surface morphology endows the sensor with exceptional antibiofouling properties. This work not only establishes a novel paradigm for electrochemical thiol determination but also provides fundamental insights into biomimetic interface engineering, with direct applicability to clinical diagnostics and point-of-care monitoring.