Calcium phosphate-polymer hybrid microparticles having functionalized surfaces prepared by a coaxially electrospray technique

Abstract

Microparticles composed of calcium phosphate (CaP) and chitosan covered with 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer were prepared in a single step by coaxial electrospraying. An aqueous solution containing calcium chloride, chitosan and an MPC polymer ethanol solution were electrosprayed from coaxial double needles into a phosphate solution. CaP/chitosan microparticles were successfully formed and their surfaces were simultaneously covered with MPC polymer. The resulting microparticles had an average diameter of around 400μm. Investigation using fluorescently labeled MPC polymer revealed surface coverage of the CaP/chitosan microparticles with MPC polymer. The formation of CaP, mainly hydroxyapatite, was confirmed by X-ray diffraction measurement. A protein adsorption study revealed that bovine serum albumin (BSA) adsorption on the microparticles was effectively suppressed by the MPC polymer. Model substances (dextran and BSA) were successfully encapsulated within the microparticles, with high encapsulation efficiencies (more than 80%), in a single step by coaxial electrospraying. Finally, we succeeded in the selective immobilization of a target protein on the surface of the CaP/chitosan microparticles covered with MPC polymer.