Electroanalytical determination of carcinoembryonic antigen at a silica nanoparticles/titania sol-gel composite membrane-modiried gold electrode

A highly hydrophilic and nontoxic colloidal silica nanoparticle/titania sol-gel composite membrane was prepared on a gold electrode via a chemical vapor deposition method. With carcinoembryonic antigen (CEA) as a model antigen and encapsulation of carcinoembryonic antibody (anti-CEA) in the composite architecture, this membrane could be used for reagentless electrochemical immunoassay. The presence of silica nanoparticles provided a congenial microenvironment for adsorbed biomolecules. The formation of immunoconjugate by a simple one-step immunoreaction between CEA in sample solution and the immobilized anti-CEA introduced the change in the potential. The modified procedure was further characterized by electrochemical impedance spectroscopy and cyclic voltammetry. Compared to the commonly applied methods, i.e., the TiO2 direct embedding procedure, this strategy could allow for antibodies immobilized with higher loading amount and better retained immunoactivity. The resulting immunosensor exhibited high sensitivity, good precision, acceptable stability, accuracy, reproducibility and wide linear range from 1.5 to 240 ng mL(-1) with a detection limit of 0.5 ng mL(-1) at 3 sigma. Analytical results of clinical samples show that the developed immunoassay is comparable with the enzyme-linked immunosorbent assays (ELISAs) method, implying a promising alternative approach for detecting CEA in the clinical diagnosis. Furthermore, this composite membrane could be used efficiently for the entrapment of other biomarkers and clinical applications.