Antibody-functionalized magnetic nanoparticles for the detection of carcinoembryonic antigen using a flow-injection electrochemical device

A magnetocontrolled immunosensing strategy based on flow-injection electrochemical impedance spectroscopy (EIS) was developed for the determination of carcinoembryonic antigen (CEA) in human serum. The immunosensor was fabricated by immobilizing anti-CEA on epoxysilane-modified core–shell magnetic Fe3O4/SiO2 nanoparticles. The detection principle is based on the difference between the resistances measured before and after the antigen–antibody interaction. The performance of the immunosensor and factors influencing this performance were also proposed. The resistance response depended linearly on the CEA concentration over the range 1.5–60 ng/ml, and the immunosensor gave a detection limit of 0.5 ng/ml (S/N = 3). Coefficients of variance (CVs) of <9.8% were obtained for the intra- and interassay precisions. The method was successfully applied to the analysis of CEA in human serum. The recoveries obtained by spiking CEA standards into normal serum were 87–113%. The performance of the immunosensor was compared with a commercially available CEA ELISA. Satisfactory results were obtained according to a paired t-test method (t value < t critical at the 95% confidence level). Importantly, the proposed immobilization protocol could be further developed to immobilize other antigens or biocompounds.