Film Formation by Precipitating Calcium Phosphate on Phospholipid Vesicle in Simulated Body Fluid Containing Trometamol

The development of calcium phosphate (CP) coating techniques on tissue culture poly(styrene) (TCPS) plates is very important in biomedical fields. In this study, CP/L-alpha-phosphatidylcholine phospholipid vesicle (PV) hybrids were formed on TCPSs, suggesting the unique physicochemical properties of CP/PV hybrid films. The film formation was conducted by the following two different processes; (i) the CP deposited on PV was prepared in a simulated body fluid containing abundant trometamol (TSBF) and subsequently tasted on TCPSs to form the films ("CP/PV-Ber'), and (ii) the CP was precipitated in TSBF on the pre-prepared PV films on TCPSs ("CP/PV-Aft"). In both processes, the CP/PV hybrid films were successfully coated on TCPSs through the mediation by PV. The morphologies and physicochemical properties of the films depended on the film formation process as well as the mineralizing time. It is presumed that the two functional groups of the phosphatidylcholine molecule, cationic choline and negative phosphate, can act as the CP nucleation sites in TSBF and the subsequent CP crystal growth would occur along the PV surfaces. It was confirmed that the mixed phases of octacalcium phosphate and hydroxyapatite (HAp) were mainly formed and were eventually converted to hydroxyapatite. The conversion was accelerated by the sterilization processes. The CP/PV-Bef films had plate-like morphologies with the particle sizes of several micrometers and poorly covered the TCPSs, whereas the CP/PV-Aft films were transparent and had the submicron-sized particulate morphologies to completely covered TCPSs. Furhtermore, the CP/PV-Aft films are stable enough to survive the sterilization processes and subsequent immersion process in a phosphate buffer saline, suggesting their application for cell culture plates.