Biomimetic Method for Production of Magnetic Hydroxyapatite Microcapsules for Enzyme Immobilization

Abstract

We fabricated hydroxyapatite microcapsules encapsulating γ-Fe₂O₃ particles by biomimetic method using Apatite Nucleus and SBF. In general, hydroxyapatite adsorbs many types of biomolecules like enzyme on its surface. In the present study, to examine enzyme immobilization property of the microcapsules, we immobilized seven types of enzymes with different isoelectric point in phosphate buffered saline (pH 7.40). From results of material analyses, we successfully fabricated hydroxyapatite microcapsules encapsulating γ-Fe₂O₃ with lower crystallinity than that of stoichiometric hydroxyapatite. In comparison with monoclinic hydroxyapatite, the microcapsules adsorbed more enzymes due to the larger specific surface area. As enzyme in the buffer was moderately charged, immobilization efficiency showed the highest value. It is suggested that immobilization efficiency was affected by pI of enzyme and that enzyme immobilization occurred by not only electrical double layer interaction but also ion interaction and other interactions.