His-tagged protein immobilization on cationic ferrite magnetic nanoparticles

Magnetic nanoparticles have been applied in various fields because of their interesting magnetic properties. Immobilization on magnetic nanoparticles is a very important step in functionalizing them. We examined protein immobilization efficiency using interactions between his-tagged enhanced green fluorescence protein and affordable cationic ferrite magnetic nanoparticles for the first time. Four types of ferrite magnetic nanoparticles were verified: cobalt iron oxide, copper iron oxide, nickel iron oxide, and iron (III) oxide as negative controls. Among the four ferrite magnetic nanoparticles, copper ferrite magnetic nanoparticle was confirmed to have the highest immobilization efficiency at 3.0 mg proteins per gram ferrite magnetic nanoparticle and 78% of total enhanced green fluorescence protein. In addition, the maximum binding efficiency was determined for copper ferrite magnetic nanoparticle. Consequently, this newly verified his-tag-immobilizing capacity of copper ferrite magnetic nanoparticle could provide a facile, capable, and promising strategy for immobilizing his-tagged proteins or peptides with high purity for biosensors, magnetic separation, or diagnostics.