A Silica-Based Molecularly Imprinted Polymer for the Specific Purification of Nattokinase

To address the low separation selectivity of nattokinase (NK) in complex biological matrices, a surface molecularly imprinted polymer (MIP) is synthesized for its highly efficient purification. Using vinyl-modified silica microspheres as substrates, a dual-functional monomer system comprising itaconic acid (IA) and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) is constructed to enhance specific recognition via synergistic hydrogen bonding and electrostatic interactions. Key preparation conditions, including the monomer ratio and the crosslinking degree, were systematically optimized, and the effects of pH and ionic strength on adsorption performance were investigated. The results indicated that under the optimal conditions of a 3:1 IA:AMPS molar ratio and a 40% crosslinking degree, the MIP exhibits a uniform core-shell structure with an average diameter of approximately 2.3 μm. The material achieves a saturated adsorption capacity of 82.58 mg g −1 and an imprinting factor (IF) of 2.35. Adsorption is primarily driven by electrostatic interactions, peaking at pH 7.0. The process follows pseudo-second-order kinetics (reaching equilibrium in ~100 min) and the Langmuir isotherm model, indicating monolayer specific adsorption. Furthermore, the MIP demonstrates preferential adsorption toward NK under the tested conditions and maintains over 90% of its capacity after five reuse cycles, highlighting its preliminary potential for adsorption-based NK enrichment and separation.