Nickel-Salen supported paramagnetic nanoparticles for 6-His-target recombinant protein affinity purification

In this research, a simple, efficient, inexpensive, rapid and high yield method for the purification of 6×histidine-tagged recombinant protein was developed. For this purpose, manganese ferrite magnetic nanoparticles (MNPs) were synthesized through a co-precipitation method and then they were conveniently surface-modified with tetraethyl orthosilicate (TEOS) in order to prevent oxidation and form high density of hydroxyl groups. Next, the salen ligand was prepared from condensation reaction of salicylaldehyde and 3-aminopropyl (trimethoxy) silane (APTMS) in 1:1 molar ratio; followed by complexation with Ni(OAc)₂.4H₂O. Finally, the prepared Ni(II)-salen complex conjugated to silica coated MNPs and MnFe₂O₄@SiO₂@Ni-Salen complex nanoparticles were obtained. The functionalized nanoparticles were spherical with an average diameter around 70nm. The obtained MNPs had a saturation magnetization about 54 emu/g and had super paramagnetic character. These MNPs were used efficiently to enrich recombinant histidine-tagged (His-tagged) protein-A from bacterial cell lysate. In about 45min, highly pure His-tagged recombinant protein was obtained, as judged by SDS-PAGE analysis and silver staining. The amount of target protein in flow through and washing fractions was minimal denoting the high efficiency of purification process. The average capacity of the matrix was found to be high and about 180±15mgg^-1 (protein/MnFe₂O₄@SiO₂@Ni-Salen complex). Collectively, purification process with MnFe₂O₄@SiO₂@Ni-Salen complex nanoparticles is rapid, efficient, selective and whole purification can be carried out in only a single tube without the need for expensive systems.