We have developed a sensitive electrochemical immunosensor for the detection of prostate-specific antigen (PSA), based on covalently immobilizing of anti-PSA and redox mediator (thionine) onto gold nanoparticles–incorporated polyamidoamine dendrimer (AuNPs–PAMAM) and multiwalled carbon nanotubes/ ionic liquid/chitosan nanocomposite (MWCNTs/IL/Chit) as the support platform. The MWCNTs/IL/ Chit nanocomposite and synthesized AuNPs were characterized using SEM and TEM microscopy techniques. Greatly amplified immunoassay was established by sandwiching the antigen between anti- PSA immobilized on the MWCNTs/IL/Chit/AuNPs–PAMAM interface and anti-PSA labeled with horseradish peroxidase (HRP-labeled anti-PSA) as secondary antibody. Phtaloyl chloride (Ph) was used as linking agent for the subsequent immobilization of AuNPs–PAMAM onto platform and anti-PSA antibody and thionine onto AuNPs–PAMAM dendrimer. The increased electrocatalytic reduction of H2O2 by HRP was monitored by differential pulse voltammetry technique. Under optimized condition the calibration curve for PSA concentration was linear up to 80 ng ml1 with detection limit (signal-to-noise ratio of 3) of 1 pgml1. AuNPs–PAMAM dendrimer as platform not only increased the amount of thionine and PSA antibody but also the electron transfer process accelerated by encapsulated AuNPs. Moreover, the proposed PSA immunosensor exhibited excellent stability and reproducibility. Accurate detection of PSA in human serum samples was demonstrated by comparison to standard ELISA assays. In addition, impedance technique was used as simple, rapid, low cost label free analytical method for PSA measurement with detection limit of 0.5 ng ml1 at concentration range up to 25 ng ml1. The results indicate that the present protocol is quite promising in developing other electrochemical immunosensors.
