Label-free electrochemical immunosensor for the determination of fetoprotein based on core-shell-shell nanocomposite particles

A new approach toward the development of advanced immunosensors based on chemically functionalized core-shell-shell magnetic nanocomposite particles, and the preparation, characteristics, and measurement of relevant properties of the immunosensor useful for the detection of alpha-1-fetoprotein (AFP) in clinical immunoassays. The core-shell NiFe2O4/3-aminopropyltriethoxysilance (APTES) (NiFe2O4@APTES) was initially prepared by covalent conjugation, then gold nanoparticles were adsorbed onto the surface of NiFe2O4@APTES, and then anti-AFP molecules were conjugated on the gold nanoparticles. The core-shell-shell nanocomposite particles not only had the properties of magnetic nanoparticles, but also provided a good biocompatibility for the immobilization of biomolecules. The core-shell-shell nanostructure present good magnetic properties to facilitate and modulate the way it was integrated into a carbon paste. The analytical performance of the immunosensor was investigated by using an electrochemical method. Under optimal conditions, the resulting composite presents good electrochemical response for the detection of AFP, and exhibits wide linear range from 0.9 to 110 ng/mL AFP with a detection limit of 0.5 ng/mL. Moreover, the proposed immunosensors were used to analyze AFP in human serum specimens. Analytical results, obtained for the clinical serum specimen by the developed immunosensor, were in accordance with those assayed by the standard ELISA. Importantly, the proposed immunoassay system could be further developed for the immobilization of other antigens or biocompounds.