Effects of DPPC/Cholesterol liposomes on the properties of freshly precipitated calcium carbonate

DPPC/Cholesterol liposomes of average diameter below 100 nm were used as a matrix for calcium carbonate precipitation. Adsorption of calcium ions on the vesicles was determined via zeta potential measurement. It was found that with increasing calcium ions concentration the electrokinetic potential of the vesicles varied toward more positive values. The changes became smaller with the cholesterol content increase. Accumulation of calcium ions close to the vesicles membranes lead to attraction of CO32− ions and enhances nucleation and growth of small calcium carbonate crystals that aggregates within lipid vesicles forming porous balls aggregates. However, dipalmitoylphosphatidylcholine (DPPC) does not change the CaCO3 crystal forms and calcite is the only form obtained during precipitation. Moreover, the influence of the phospholipid on the calcium carbonate precipitation is enhanced by the induction of cholesterol to the lipid membranes.