Biophysical aspects of lipid interaction with mineral: liposome model studies

The present paper reviews the use of liposomes as synthetic models for studying various biophysical aspects of matrix vesicle calcification, especially the involvement of acidic phospholipids in the nucleation and growth processes which occur during the initial stages of mineral formation in and around these membrane-bound structures. Recent results showed that acidic phospholipids incorporated into phosphatidylcholine-rich anionic liposome membranes were ineffective in initiating extraliposomal calcium phosphate precipitation from metastable solutions at physiological pH. On the contrary, certain acidic phospholipids such as phosphatidic acid and phosphatidylserine retarded the development of such precipitation when the latter was endogenously induced. The extent of inhibition correlated with the strength of the electrostatic interaction between the polar head group of the acidic phospholipid and the surface of the mineral phase. The results suggest that acidic phospholipids may play an important role in controlling the rate of early mineral development in matrix vesicle calcification.