Facile synthesis of polyaniline-polythionine redox hydrogel: Conductive, antifouling and enzyme-linked material for ultrasensitive label-free amperometric immunosensor toward carcinoma antigen-125.

Sensitivity enhancement and proteins adsorption are the common challenges faced in protein immunoassays. In this work, an ultrasensitive and protein-resistant label-free amperometric immunosening platform for carcinoma antigen-125 (CA125) based on redox polyaniline-polythionine hydrogel (PANI-PThi gel) was developed. The as-prepared hydrogel, which was facilely synthesized by electropolymerization, exhibited good conductivity and strong hydrophilicity while the sensitivity and specificity of the immunosensor can be enhanced. Furthermore, the as-prepared AuNPs functionalized PANI-PThi gel exhibited strong current signal and HO electrocatalytic ability, which guaranteed a large current variable range. Based on these, the prepared immunosensor revealed a wide linear range from 0.0001 U mL to 1 kU mL, a limit of detection of 0.00125 U mL and its sensitivity was at least three-fold higher than previous works. More importantly, the prepared immunosensor exhibited excellent specificity, making it capable of assaying CA125 in human serum.