Fabrication of Phospholipid Vesicle-Interacted Calcium Phosphate Films with Sterilization Stability

The development of a calcium phosphate (CP) coating technique,on tissue culture poly(styrene) (TCPS) is important in biomedical fields. In this study, the CP hybridized with L-a-phosphatidylcholine phospholipid vesicle (PV) was formed on TCPS as the film state for suggesting the unique 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 (SBF) and subsequently tasted on TCPS to form the films, and (ii) the CP was precipitated in SBF on the pre-prepared PV films on TCPS. These films were denoted as "CP/PV-Bef" and "CP/PV-Aft" films. The, stability of the CP/PV hybrid films against the sterilization processes (ethanol, UV/ozone, and autoclave treatments) and subsequent immersion process in a phosphate buffer saline (PBS) was also demonstrated. As a result, the CP/PV hybrid films were successfully coated on TCPS through the mediation by PV with preserving the vesicle structure. The morphologies and physicochemical properties of the films depended on the film formation process as well as the mineralizing time. It is presumed that two functional groups of cationic choline and negative phosphate in the phosphatidylcholine molecule can act as the CP nucleation sites in SBF and the subsequent CP crystal growth would occur along the PV surfaces. Furthermore, it was confirmed that amorphous calcium phosphate and calcium pyrophosphate dihydrate were mainly formed in the initial mineralization stage and were eventually converted to the hydroxyapatite phase. The conversion was accelerated by the autoclave treatment. Therefore, these CP/PV films have transparency, unique structures, and good stability against sterilization treatments, suggesting the application for cell culture plates.