Synthesis and characterization of core-shell Au Fe oxide nanocomposites and their application for detecting immunological interaction.

Gold (Au) Fe oxide core-shell nanostructure is a major class of nanoscale materials that has attracted considerable attention due to its biotechnological and biomedical applications and properties. Here we synthesized magnetite nanoparticles (MNPs), an average size of 10-12 nm in diameter, using the chemical co-precipitation of Fe2(+) and Fe3(+) in strong alkaline material. Then, an Au-coated Fe oxide core-shell nanocomposite with an average diameter of 18-20 nm was produced in the presence of sodium citrate as the reducing agent. The core-shell structure and the presence of the Fe and Au phases have been confirmed by transmission electron microscopy (TEM), x-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The Au-coated Fe oxide NPs can be used as a carrier in digoxin immunoassays. The concentration of anti-digoxin antibody (Ab) immobilized on the NPs was 30 μg/mg. In order to validate the quality of the Au-coated Fe oxide NPs as immunoassay carriers, an immunoassay system was developed. The relative amount of anti-digoxin Ab immobilized on the NPs was determined by enzyme linked immunosorbent assay (ELISA). Immobilization studies with Ab demonstrated that the Au Fe oxide core-shell nanostructure can be used to immobilize Ab, making them valuable for biomedical and biological applications.