Enhanced performance of label-free electrochemical immunosensor for carbohydrate antigen 15-3 based on catalytic activity of cobalt sulfide/graphene nanocomposite

[Display omitted] •An immunosensor based on Cobalt sulfides/graphene nanocomposites was developed.•The fabrication of immunosensor for enzyme-free determination of CA15-3 biomarker.•The immunosensor can be utilized as a simple tool to detect of CA15-3 in real sample. In the present study, an electrochemical sensing platform based on CoS2-GR and AuNPs composites (CoS2-GR-AuNPs) was developed for electrochemical immunosensor. In the proposed immunosensor, AuNPs act as the immobilization site for binding of antibodies. CoS2-GR nanocomposite shows excellent electrocatalytic activity toward the oxidation of catechol and also yielded large surface area, which improve the amount of immobilized CA15-3 antibody. Graphite screen-printed electrodes modified with CoS2-GR-AuNPs and applied to development of the enzyme-free and label-free electrochemical immunosensor for detection of protein biomarker carbohydrate antigen 15-3 (CA15-3). Due to the electrocatalytic activity of CoS2-GR nanocomposite toward the oxidation of catechol as probe, determination of CA15-3 antigen was based on its obstruction to the electrocatalytic oxidation of probe by modified screen-printed electrodes after binding to the surface of electrode through interaction with the CA15-3 antibody. The fabricated immunosensor exhibited a wide linear range of 0.1–150UmL−1 and a low detection limit of 0.03UmL−1. The immunosensor showed good accuracy, stability, specificity and it was successfully applied for CA15-3 detection in serum samples. The proposed immunosensor provides a promising sensitive method for clinical applications.