Metal-Organic Frameworks-Derived FeCoZn-NC-1.5-800 as Dual-Enzyme Mimics for L-Cysteine Detection

A trimetallic (Fe, Co, Zn) nanozyme embedded within a N-doped carbon matrix (FeCoZn-NC-1.5-800) was engineered via coordination-controlled pyrolysis of Fe ions doped core-shell ZIF-8@ZIF-67 (ZIF-8@ZIF-67-Fe-1.5) precursor, which exhibited dual oxidase/peroxidase-mimicking activities. The bifunctional catalyst oxidized 3,3',5,5'-tetramethylbenzidine (TMB) to form a blue product of oxidized TMB (oxTMB) without exogenous H2O2. However, the addition of L-cysteine (L-Cys) acted as a potent inhibitor, quenching oxTMB formation via thiol-mediated electron transfer, leading to a significant decrease in absorbance and the fading of the blue colour to colourless. Consequently, an H2O2-independent colormetric biosensor was developed with a wide linear range (5-50 μM), a low detection limit (0.569 μM, 3σ), good selectivity and anti-interference ability. This work establishes a paradigm for transition metal nanozyme design, offering clinical translation potential in point-of-care thiol monitoring and biocatalytic system development.