Functionalized polyaniline based on protonic acid doping as a direct electron mediator to amplify sensor signals

A “label-free” electrochemical immunosensor was developed to detect α-fetoprotein (AFP) sensitively. HCS@PANI (High carbonized nanospheres@Polyaniline) is used as an electrochemical sensing platform to improve conductivity and enhanche the amount of AFP antibody (anti-AFP) immobilized on the electrode surface. PANI, which is involved by protonic acid, exhibits excellent electrochemical activity and can be used as a direct electron mediator to further amplify electrochemical signals. Under optimal conditions, the electrochemical immunosensor has a linear range of 0.001–80 ng/mL and a minimum detection limit of 0.33 pg/mL. The immunosensor is expected to be used in clinical laboratories to detect AFP and other tumor markers in human plasma for precancerous screening or cancer surveillance.