Enzyme@silica hybrid nanoflowers shielding in polydopamine layer for the improvement of enzyme stability

In this study, a novel kind of flower-like monodisperse silica nanoparticles (silica nanoflowers) were successfully synthesized based on the microemulsion phase composed of water-surfactant-oil ternary systems. The obtained silica nanoflowers were used to immobilize penicillin G acylase (PGA). The maximum adsorption capacity of immobilized PGA (PGA@nanoflowers) was 207.3 mg/support and the specific activity was 539.1 U/support. In addition, based on the mussel-inspired chemistry, we demonstrated a simple and highly effective strategy to stabilize the enzymes that immobilized on silica nanoflowers by the poly(dopamine) (PDA) coating through in situ polymerization. The effects of pH and temperature on the activity of free PGA, PGA@nanoflowers and immobilized PGA with PDA coating (PDA-coated PGA@nanoflowers) were investigated. The operational stability, storage stability and kinetic properties of the different preparation of PGA were also tested. Compared to free PGA and PGA@nanoflowers, the stabilities of PDA-coated PGA@nanoflowers were all improved significantly. This work demonstrated that the PDA coating presented a new way for surface modification of immobilized enzyme to improve the properties of enzyme. The approach of enzyme@silica hybrid nanoflowers shielding in PDA layer would have great potential in various enzyme immobilization.