A cascade reaction signal-amplified amperometric immunosensor platform for ultrasensitive detection of tumour marker

A new strategy for signal amplification was introduced in a label-free amperometric immunoassay platform. Improvements in the signal occurred following the oxidation of glucose by glucose oxidase and catalysis by polythionine of the produced H 2 O 2 from the previous oxidation reaction. In addition, a multifunctional conductive hydrogel, polypyrrole-polythionine-gold with glucose oxidase , was synthesised with a one-pot method using pyrrole and thionine as monomers, ammonium persulfate and HAuCl 4 as co-oxidant agents, and glucose oxidase as the doping agent. Combined with the hydrogel, a label-free amperometric immunoassay for the tumour marker neuron-specific enolase (NSE) was obtained. If operated at 0   V (vs. Ag/AgCl), the sensor exhibited a wide liner range from 100   ng   mL −1 to 1   pg   mL −1 and ultralow detection limit of 0.65   pg   mL −1 (S/N   =   3). The presented method was further used for the analysis of human serum samples and showed good consistency with detection results from an electrochemiluminescence immunoassay.