Selective removal of IgG from the urine of patients with proteinuria using a polymer coated core–shell magnetic nanoparticle

Abstract

Selective removal of highly abundant proteins prior to analysis is an important issue in proteomics. In this study, a core–shell structured magnetic nanocomposite of Fe₃O₄@SiO₂@MAsp-HEMA was found to be an effective and selective adsorbent to remove highly abundant IgG from the urine of patients with proteinuria. This novel magnetic adsorbent was prepared by coating a poly(N-methacryloyl-L-aspartic acid-hydroxyethyl methacrylate) shell on Fe₃O₄@SiO₂ nanoparticles via a coupling agent of KH-570 using the mini-emulsion polymerization method. The as-synthesized nanoparticle was characterized by X-ray diffraction, elemental analysis, thermal gravimetric analysis, infrared spectroscopy, magnetic hysteresis loop curves, scanning electronic microscopy and transmission electron microscopy. A kinetic adsorption experiment was performed to investigate the speed of adsorption and the time to reach the adsorption balance. 1D SDS-PAGE analysis and capillary electrophoresis were used to validate its selective adsorption ability. The resulting Fe₃O₄@SiO₂@MAsp-HEMA showed a uniform spherical shape at nanoscale dimensions of about 200–300 nm, removing efficiency above 80%, and maximum adsorption capacity of 18.08 μg mg⁻¹ at 15 ± 0.5 °C. The binding between IgG and the ligand was confirmed by isothermal titration calorimetry. The hydrogen bonding force was demonstrated as one of the major interactions between the functional groups of the as-synthesized magnetic nanoparticles and IgG by a molecular docking experiment.