Magnetite Nanoparticles with High Affinity Toward Target Protein for Efficient and Facile Bio‐Separation

Abstract Magnetite nanoparticles (Fe 3 O 4 NPs) with molecular recognition capabilities offer significant potential for biomedical applications, yet existing surface protein imprinting methods often suffer from low efficiency. Herein, a surface enzyme‐mediated polymerization strategy is exploited for surface imprinting of bovine serum albumin (BSA) onto Fe 3 O 4 NPs. This method, compatible with all vinyl monomers and operable under mild conditions, enables imprinting at high monomer concentrations while preventing nanoparticle agglomeration. Notably, increasing the pre‐polymerization solution concentration enhances the pre‐assembly of functional monomers and template molecules, thereby improving imprinting efficiency. Furthermore, replacing conventional crosslinkers with a polyglutamic acid‐based peptide crosslinker introduces a pH‐responsive helix‐coil transition, allowing complete template removal under mild conditions and increasing the adsorption capacity and imprinting factor to 139.8 mg g⁻¹ and 10.36, respectively. The resulting BSA‐imprinted Fe₃O₄ NPs exhibits high selectivity, robustness, and rapid adsorption kinetics while maintaining strong magnetic responsiveness for easy separation. These features allows for the selective extraction of BSA from bovine fetal serum, demonstrating the potential of this approach for biomedical applications, particularly in bioseparations.