Synthesis of silica nanospheres with Ni2+-iminodiacetic acid for protein separation

Silica (SiO 2 ) nanospheres (NSs) with immobilized metal ligands have been prepared for the affinity separation of proteins. First, SiO 2 NSs were prepared by controlled hydrolysis of tetraethoxysilane in a basic aqueous-ethanol solution. Then through reaction of iminodiacetic acid (IDA) with 3-glycidoxypropyltrimethoxysilane and immobilization of them onto the surfaces of above SiO 2 NSs, novel affinity adsorbents with IDA chelating groups were obtained. After chelating Ni 2+ ions, the SiO 2 –IDA–Ni 2+ NSs were applied to separate his-tagged proteins directly from the mixture of lysed cells. The SiO 2 –IDA–Ni 2+ NSs present negligible nonspecific protein adsorption and high protein binding ability (28.3 mg/g).