Fe₃O₄/PVIM-Ni²⁺ magnetic composite microspheres for highly specific separation of histidine-rich proteins

Integration of the advantages of immobilized metal-ion affinity chromatography (IMAC) and magnetic microspheres is considered as an ideal pathway for quick and convenient separation of his-tagged proteins, but rare reports concern the natural histidine-rich proteins. In this article, a novel route was presented to fabricate magnetic microspheres composed of a high-magnetic-response magnetic supraparticle (Fe3O4) core and a Ni(2+)-immobilized cross-linked polyvinyl imidazole (PVIM) shell via reflux-precipitation polymerization. The unique as-prepared Fe3O4/PVIM-Ni(2+) microspheres possessed uniform flower-like structure, high magnetic responsiveness, abundant binding sites, and very easy synthesis process. Taking advantage of the pure PVIM-Ni(2+) interface and high Ni(2+) loading amount, the microspheres exhibited remarkable selectivity, excellent sensitivity, large enrichment capacity, and high recyclability in immobilization and separation of his-tagged recombinant proteins. More interestingly, it was found that the Fe3O4/PVIM-Ni(2+) microspheres also showed excellent performance for removal of the natural histidine-rich bovine serum albumin (BSA) from the complex real sample of fetal bovine serum due to the exposed histidine residues. Considering their multiple merits, this new type of Fe3O4/PVIM-Ni(2+) nanomaterial displays great potential in enriching low-abundant his-tagged proteins or removing high-abundant histidine-rich natural proteins for proteomic analysis.