A superoxide dismutase mimic nanocomposite for amperometric sensing of superoxide anions

A nanocomposite consisting of gold nanoparticles and the copper(II) complex of cysteine (GNP/Cu-Cys) is shown to represent a useful mimic for the enzyme superoxide dismutase (SOD). The relative activities of plain GNPs, Cu metal, Cys, Cu-Cys and GNP/Cu-Cys were determined and compared to those of native SOD. The value for half-maximal inhibitory concentration of the nanocomposite is 0.3 mu ga (TM) mLaEuro3/4(1) which is 3 times higher than that of the native enzyme. The GNPs/Cu-Cys nanocomposite was immobilized on a carbon paste electrode and used as a biomimetic sensor for the detection of superoxide anions. The resulting sensor has a linear range over the concentration range from 3.1 to 326 mu M, a detection limit of 2.8 mu M (at an S/N of 3), and a sensitivity of 0.018 mu Aa (TM)mu M.cm(-2). The selectivity for superoxide anions over potential interferents such as hydrogen peroxide, uric acid and citric acid is excellent.