Dextran formation on hydroxyapatite by immobilized dextransucrase to control protein adsorption

Dextran was formed on the surface of hydroxyapatite by the enzymatic reaction of dextransucrase to control protein adsorption. The hydroxyapatite substrate was immersed in a dextransucrase solution (0.3 U/mL, pH 5.5) to immobilize dextransucrase to the hydroxyapatite surface at 6.0 U/mL. The dextransucrase-immobilized hydroxyapatite was then reacted with a sucrose substrate to generate dextran from the active sites of the immobilized dextransucrase. The amount of dextran produced changed with reaction time and substrate concentration, generating dextran at a maximum of 50 mg/g. When the proteins, bovine serum albumin and γ-globulin, were adsorbed to the surfaces of both hydroxyapatite and dextran-generated hydroxyapatite, the amount of protein adsorbed decreased with increasing amount of dextran produced, indicating that the protein did not reach the adsorption sites of hydroxyapatite as a result of steric exclusion by dextran. The protein adsorption performance revealed that the generated dextran on HAP can size-exclude proteins.