Simultaneous determination of dopamine and serotonin on gold nanocluster/overoxidized-polypyrrole composite modified glassy carbon electrode

A promising electrochemical biosensor was developed by electrodeposition of gold nanoclusters on insulating overoxidized-polypyrrole (PPyox) film modified glassy carbon electrode (GCE). The nano-Au/PPyox composite-coated GCE was used to determine dopamine (DA) and serotonin (5-HT), exhibiting stable and sensitive current responses toward DA and 5-HT oxidation. The sensor was also quite effective to simultaneously determine these species in a mixture and resolved the overlapping anodic peaks of 5-HT, DA and ascorbic acid (AA, 1000-fold) into three well-defined voltammetric peaks in differential pulse voltammetry (DPV) at 0.37, 0.20 and 0.01 V (versus SCE), respectively. The linear response was obtained in the range of 7.0 × 10−9 to 2.2 × 10−6 M with a detection limit of 1.0 × 10−9 M for 5-HT, and in the range of 7.5 × 10−8 to 2.0 × 10−5 M with a detection limit of 1.5 × 10−8 M for DA (s/n = 3), respectively. The oxidation of 5-HT and DA were controlled by the adsorption surface process, as well as the competitive adsorption between 5-HT and DA were investigated at the nano-Au/PPyox/GCE. The designed sensor had been successfully applied for the determination of 5-HT and DA in human blood serum and obtained satisfactory results.