New functional amorphous calcium phosphate nanocomposites by enzyme-assisted biomineralization

In the present study, we report on enzyme-assisted formation of biomineralized amorphous calcium phosphate nanocomposites (ACP-NCs). About 100-200 nm sizes of the spherical porous enzyme-assisted ACP-NCs were successfully synthesized via double reverse microemulsion, but no ACP-NCs formed without the enzyme. It is believed that the enzyme was used as an organic template or additive that could regulate the biomineralization process. The enzyme-assisted ACP-NCs were well characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, dynamic light scattering, and Brunauer-Emmett-Teller (BET) criteria. The BET surface area, total pore volume, pore size from adsorption, and pore size from desorption of the ACP-NCs were 163 m² g^-1 or 0.37 cm³ g ^-1, 8.87 nm, and 7.48 nm, respectively. The enzyme-assisted ACP-NCs retained about 43% of the catalytic activity of free carboxyl esterase. Furthermore, they preserved their bioactivity even after the 10th reuse and were stable over 10 days even under a stringent shaking conditions. The reported method paves the way for novel biomineralization via enzyme molecules to form functional enzymes containing nanocomposites.