Polymer–inorganic microcapsules fabricated by combining biomimetic adhesion and bioinspired mineralization and their use for catalase immobilization

•A combined bioinspired approach to an enzyme bioreactor was developed.•Enzyme bioreactors were constructed upon polymer–inorganic hybrid microcapsules.•Polydopamine/polyethyleneimine/titania hybrid microcapsules were prepared.•The chemical/topological structure of the microcapsules can be facilely tuned.•Enhanced enzyme catalytic activity and desirable stability were obtained.

Herein, a novel enzyme bioreactor based upon polymer–inorganic hybrid microcapsules was prepared through combining biomimetic adhesion and bioinspired mineralization. Briefly, polydopamine (PDA) as the adhesive layer was formed on the surface of CaCO3 particles through self-polymerization of dopamine. Then, polyethyleneimine (PEI) was anchored on the adhesive layer through Michael addition reaction or Schiff base reaction. Subsequently, titania (Ti) as the mineral layer was generated and deposited on the surface of PDA/PEI-coated particles through the bioinspired mineralization process induced by the free amine groups of PEI. Finally, PDA/PEI/Ti hybrid microcapsules were obtained after removing the CaCO3 templates via EDTA treatment. Notably, during the preparation process, PEI could be considered as a “bridge” molecule to connect the adhesive layer and the mineral layer. The chemical/topological structure of the hybrid microcapsules could be facilely tuned by manipulating the molecular weight of PEI. Once utilized for constructing an enzyme bioreactor, the structural evolution of the hybrid microcapsules caused a varied enzyme catalytic activity (42–73 U mg−1). This structure–performance relationship might be due to the alterable diffusion resistance resulting from the mineral layer. Besides, the enzymes encapsulated in PDA/PEI/Ti hybrid microcapsules also exhibited desirable thermal, pH, storage and recycling stabilities.

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