Protein adsorption on citrate modified magnetic nanoparticles.

Magnetic iron oxide nanoparticles were prepared by chemical co-precipitation method and then modified with sodium citrate. These iron oxide nanoparticles were characterized by transmission electron microscopy (TEM), X-ray diffractometer (XRD), and vibrating sample magnetometer (VSM). BSA was adsorbed on these citrate modified nanoparticles using two types of buffers (acetate buffer, pH 4.0, 4.7 and phosphate buffer, pH 7.4). The results showed that the maximum adsorption of BSA was 83 mg/g at its isoelectric point (pH 4.7). Fourier-transform infrared spectroscopy (FTIR) was used to confirm the attachment of citrate groups and BSA on the prepared magnetic nanoparticles. BSA was desorbed from nanoparticles under alkaline conditions, which was confirmed by SDS-PAGE electrophoresis, UV-vis and fluorescence spectra. The desorbed BSA showed small changes in its structure. The adsorption results indicated that BSA adsorption on citrate modified iron oxide nanoparticles occurred mainly by electrostatic mechanism.