Dopamine coating as a general and facile route to biofunctionalization of superparamagnetic Fe₃O₄ nanoparticles for magnetic separation of proteins

A facile approach to prepare water-dispersible super-paramagnetic iron oxide nanoparticles (MNPs) is reported. The homogeneous MNPs prepared in organic phase are functionalized with an aqueous solution of dopamine at room temperature. The obtained dopamine modified MNPs (MNP-DA) exhibiting excellent super-paramagnetic property can bind various molecules, including NTA and proteins under mild conditions. To demonstrate the feasibility for biological application, the MNP-DA was used for rapid and efficient magnetic separation of bovine albumin (BSA) carrying fluorescent Au nanoclusters from fluorescein. Furthermore, the MNP-DA was functionalized with Nα,Nα-bis (carboxy methyl)-l-lysine hydrate (NTA) to reversibly immobilize and release histidine-tagged proteins. The present study demonstrates a general and facile route to the efficient modification of magnetic nanoparticles with various functional materials and paves the way for a wide range of biomedical applications of MNPs.