Core–Shell Magnetic Mesoporous Silica Microspheres with Large Mesopores for Enzyme Immobilization in Biocatalysis

Magnetic mesoporous silica microspheres with core–shell structure and large pores are highly desired in macromolecules delivery and biocatalysis, biospeparation, and adsorption. In this work, a controllable solvent evaporation induced solution-phase interface co-assembly approach was developed to synthesize core–shell structural magnetic mesoporous silica microspheres with ultralarge mesopore size (denoted as LP-MMS). The synthesis was achieved by employing large-molecular-weight amphiphilic block copolymers poly(ethylene oxide)-block-poly(methyl methacrylate) (PEO-b-PMMA) and small surfactant cetyltrimethylammonium bromide as co-templates, which can co-assemble with silica source in tetrahydrofuran/water solutions. The obtained LP-MMS microspheres possess uniform rasberry-like morphology with a diameter of 600 nm, large primary spherical mesopores (ca. 36 nm), large specific surface area (348 m2/g), high specific pore volume (0.59 cm3/g), and fast magnetic responsivity with high magnetization (15.9 emu/g). The mesopore morphology can be transformed from spherical to cylindrical through introducing a shearing force during the interfacial co-assembly in the synthesis system. The designed LP-MMS microspheres turn out to be good carriers for enzyme (trypsin) immobilization with a high loading capacity of 80 μg/mg and demonstrate excellent biocatalysis efficiency up to 99.1% for protein digestion within 30 min and good recycling stability with negligible decay in digestion efficiency after reuse for five times.