Baqiyatallah University of Medical Sciences, Iran
We report results of the studies relating to fabrication of the sensing platform for development of label free electrochemical immunosensor based on graphene (Gr) and copper sulfide (CuS) composite and further poly p-phenylenediamine and graphene nanocomposite (PPD-GR). Graphite screen-printed electrodes (SPEs) modified with CuS-GR and PPD-GR nanocomposite and applied to advance label-free and non-enzymatice electrochemical immunosensor for quantitative determination of protein biomarker carbohydrate antigen 15-3 (CA15-3) and neuron-specific enolase (NSE), respectively. CuS-GR nanocomposite shows excellent electrocatalytic activity towards catechol as probe, which improve the sensitivity of the immunosensor. Also, It was found that the PPD-GR nanocomposite exhibits excellent electrocatalytic activity towards ascorbic acid (AA) oxidation as analytical signal based on EC′ mechanism. The CuS-GR based immunosensor exhibited a wide linear range of 1.0–150 U mL-1, with a low detection limit of 0.3 U mL-1 toward CA15-3. In the case of PPD-GR nanocomposite based immunosensor due to the excellent electrocatalytic activity of PPD-GR nanocomposite, determination of NSE antigen was based on its obstruction to the electrocatalytic oxidation of AA after binding to the surface of electrode through interaction with the anti-NSE. The proposed immunosensor exhibited a wide linear range of 1.0–1000 ng mL-1, with a low detection limit of 0.3 ng mL-1 toward NSE. These developed immunosensor showed good specificity, accuracy, stability and it was successfully applied for the determination of CA15-3 and NSE in real samples. The CuS-GR and PPD-GR nanocomposite materials-based immunoassay provides a promising sensitive biosensor approach for clinical applications.