Superparamagnetic Fe3O4/PMMA composite nanospheres as a nanoplatform for multimodal protein separation

Fe3O4/PMMA composite nanospheres with diameters ranging from 10 to 90 nm and saturation magnetisation varying from 29 to 39 emu g(-1) have been successfully synthesized via a facile mini-emulsion polymerisation. Through simple surface modification, the nanospheres could be effectively used for fast protein adsorption, His-tagged protein separation and low concentration protein enrichment. The maximum adsorbed amount of lysozyme was as high as 478 mg g(-1) near its isoelectric point using the Fe3O4/PMMA composite nanospheres. After enrichment with the nanosphere removed surfactants, the S/N of cytochrome C (cyt C) at a concentration of 0.5 mg L-1 remarkably increased to 68. Additionally, the surface functionalized nanospheres showed highly selective separation of His-tagged glutathione S-transferase (GST) from cell lysate. The results indicate the Fe3O4/PMMA composite nanospheres could be used as a nanoplatform for multimodal protein separation.