A label-free immunosensor based on graphene nanocomposites for simultaneous multiplexed electrochemical determination of tumor markers

• The label-free immunosensor with good electrochemical performance simplified the operation.
• The immunosensor avoided the cross-talk between the different analytes.
• This method performed very well on the detection of clinical serum specimens.
• The method could be modified and extended to the detection of other multiple targets.

Here we prepared a label-free electrochemical immunosensor employing indium tin oxide (ITO) sheets as working electrodes and graphene nanocomposites as supporting matrix for simultaneous determination of carcinoembryonic antigen (CEA) and α-fetoprotein (AFP). Reduced graphene oxide/thionine/gold nanoparticles nanocomposites were synthesized and coated on ITO for the immobilization of anti-CEA while reduced graphene oxide/Prussian Blue/gold nanoparticles were used to immobilize anti-AFP. The immunosensor determination was based on the fact that due to the formation of antibody–antigen immunocomplex, the decreased response currents of thionine and Prussian Blue were directly proportional to the concentrations of corresponding antigens. Experimental results revealed that the multiplexed immunoassay enabled the simultaneous determination of CEA and AFP with linear working ranges of 0.01–300 ng mL−1. The limit of detections for CEA is 0.650 pg mL−1 and for AFP is 0.885 pg mL−1. In addition, the methodology was evaluated for the analysis of clinical serum samples and received a good correlation with the enzyme linked immunosorbent assay.