A superoxide anion electrochemical sensor based on the direct electrochemistry of superoxide dismutase assembled layer-by-layer at the L-cysteine modified gold electrode

A superoxide anion (O-2(center dot-)) biosensor has been developed based on layer-by-layer assembled poly-(diallyldimethylammonium) (PDDA) and superoxide dismutase (SOD) on the L-cysteine (Cys) modified gold (Au) electrode. In 25 mM phosphate buffer solution (pH 7.2), the {SOD/PDDA}(n)/Cys/Au electrode shows a pair of well-defined and nearly reversible peak at similar to 84 mV vs SCE, confirming the direct electrochemistry of SOD. Based on the bifunctional enzymatic catalytic activities of SOD to the oxidation and reduction of O-2(center dot-), the developed {SOD/PDDA}(5)/Cys/Au electrode exhibits good analytical characteristics in the detection of O-2(center dot-), such as low detection limit, good stability, reproducibility, selectivity and particularly a wide linear range (0.5 similar to 546 mu M).