Dual-responsive electrochemical immunosensor for prostate specific antigen detection based on Au-CoS/graphene and CeO2/ionic liquids doped with carboxymethyl chitosan complex

Combining dual-signal channels of differential pulse voltammetry (DPV) and amperometric i–t curve, we developed an amplified sandwich-type electrochemical immunosensor for ultrasensitive detection of prostate specific antigen (PSA). Due to the large specific surface area and good adsorption property, 3-aminopropyltriethox functionalized CeO 2 mesoporous nanoparticles (NH 2 -M-CeO 2 ) was used for supporting toluidine blue (TB) as the electron transfer mediator and anti-PSA as the signal response. To prevent the leak of TB and facilitate the electron transfer property of NH 2 -M-CeO 2 , ionic liquids doped carboxymethyl chitosan (CMC/ILs) were incorporated and TB/M-CeO 2 /CMC/ILs complex was gotten to act as the label of anti-PSA (Ab 2 ). Meanwhile, Au-CoS/graphene was as the matrix materials modifying the electrode to immobilize anti-PSA (Ab 1 ). Specifically, Au-CoS/graphene cannot produce electrochemical signals through DPV method but can provide an obviously electrochemical signal towards catalysis hydrogen peroxide (H 2 O 2 ) through amperometric i–t curve method. At the time of detection, with the increase of concentrations of PSA, the DPV signals from TB/M-CeO 2 /CMC/ILs were increased and the amperometric i–t curve signals from the Au-CoS/graphene were decreased. Under the optimum conditions, the immunosensor demonstrated remarkable analytical performance of a linear range of 0.5   pg/mL to 50   ng/mL with a detection limit of 0.16   pg/mL for quantitative detection of PSA (S/N=3).