Selective sensing of cysteine on manganese dioxide nanowires and chitosan modified glassy carbon electrodes

We report a simple approach for the selectively electrochemical sensing of cysteine (CySH) using β-MnO2 nanowires modified glassy carbon (GC) electrode via a direct and facile electrochemical co-deposition process with chitosan hydrogel. The electrode showed excellent electrocatalytic effect toward cysteine oxidation. A possible reaction mechanism related to the formation of surface complexes was proposed: the –SH group is the reacting group in the reaction between cysteine and MnO2, while the –NH2 group acts as an anchor to stabilize the surface complexes. The electrocatalytic behavior is further developed as a sensitive detection scheme for cysteine by amperometric measurement, which shows a large determination range of 0.5–630 μM and a low detection limit of 70 nM. Other nineteen amino acids in a 20-fold concentration do not interfere in the detection of cysteine. Furthermore, other biological species containing –SH group or SS bonds, such as glutathione, cystine, and bovine serum albumin (BSA), show no interferences because of steric hindrance and inactive SS bonds.