Electrochemical immunosensor for simultaneous detection of multiplex cancer biomarkers based on graphene nanocomposites

In this work, a sandwich-format electrochemical immunosensor for simultaneous determination of carcinoembryonic antigen (CEA) and alpha-fetoprotein (AFP) was fabricated using biofunctional carboxyl graphene nanosheets (CGS) as immunosensing probes, which were fabricated by means of immobilization of toluidine blue (TB) and labeled anti-CEA (Ab(2,1)), Prussian blue (PB) and anti-AFP (Ab(2,2)) successively on CGS. The capture anti-CEA (Ab(1,1)) and anti-AFP (Ab(1,2)) were immobilized onto the chitosan-Au nanoparticles (CHIT-AuNPs) modified electrode through 1-(3-dimethylaminopropy1)-3-ethylcarbodiimide hydrochloride and N-hydroxy succinimide (EDC/NHS). Experimental results revealed that this sandwich-type immunoassay enabled simultaneous detection of CEA and AFP with linear range of 0.5-60 ng mL(-1) for both analytes. The detection limit was 0.1 ng mL(-1) for CEA and 0.05 ng mL(-)1 for AFP (S/N=3). The assay results of serum samples with the proposed method were in a good agreement with the reference values from the standard ELISA method. And the negligible cross-reactivity between the two analytes allows it to possess potential promise in clinical diagnosis. (C) 2013 Elsevier B.V. All rights reserved.