Use of Polyethyleneimine Coated Fe3O4 Nanoparticles as an Ion-Exchanger for Protein Separation

Nanoparticles of Fe3O4 were coated with PEI and were found to have zeta potential of +18.4 mV. When used as anion exchanger for separation of lipases, a significant fraction of the enzyme could not be eluted. Shielding chromatography described in the literature outlines the use of polymers like PVP to cut down the binding of the proteins due to nonspecific interactions. Shielding by 2% PVP resulted in improvement of elution of the lipases with 1 M NaCl. To give a specific example, elution of Mucor miehei lipase increased from 56.8% to 68.3%. Similar results were observed with Candida rugosa lipase and green fluorescent protein. SDS-PAGE showed significant level of purification in all the cases. The results are promising towards the development of nanosized magnetic ion exchangers for bioseparation of proteins.