Hollow Double-Layered Mesoporous Silica as an Enzyme Immobilization Platform: Enhancing Biocatalytic Efficiency in Docosahexaenoic Acid Phosphatidylcholine

This study reports the synthesis of bifunctional hollow double-layered mesoporous silica (HdlMS) nanoparticles as an effective support for enzyme catalysis. Using a self-template method combined with sol-gel processing, selective etching, and surface modification with alkyl groups and nitrogenous fatty amine groups, we successfully prepared the NH₂/C₈-HdlMS carrier. Phospholipase A1 was then immobilized onto this carrier to construct PLA1@NH₂/C₈-HdlMS, which was subsequently applied to the synthesis of docosahexaenoic-acid-enriched phosphatidylcholine. The results demonstrated a docosahexaenoic acid incorporation rate of 67% within 8 h, and a catalytic efficiency (CE) of 18.84 mmol·g^-1·h^-1, the highest value reported to date. The biocatalyst retained approximately 81% of its initial activity after nine consecutive cycles, demonstrating excellent stability and reusability. The HdlMS structure, with its large internal surface area and optimized substrate transport, combined with surface modifications that enhance enzyme-support interactions, contributed to the high CE value, as confirmed by the detailed controlled experiments. This study not only offers novel design principles for high-performance enzyme immobilization carriers but also advances the development of structurally tailored phospholipids for industrial applications.