Phospholipid determination in lipospheres for drug and cosmetic topical applications

Purpose: Assessment of alternative structure in liposphere production by means phospholipid determination.Methods: Lipospheres were prepared by the melt method using two different ratios between tristearin as the lipid phase and hydrogenated soybean phosphatidylcholine as the emulsifier. Three fractions were recovered by centrifugation and analysed for morphology and size and for phospholipid composition by enzymatic reaction, Energy Dispersive X-ray Analysis (EDS) and Differential Scanning Calorimetry (DSC).Results: Liposphere production, involving 4:1 and 2:1 tristearin/phospholipid ratios, led to samples having different properties. In order to evaluate the coexistence of additional structures phospholipid determinations were carried out by enzymatic-spectrophotometric assay, EDS and DSC. The particles obtained by using both tristearin/phospholipid ratios and recovered in the lower fraction were characterized by the smallest size (about 5% < 1 micron and about 80% < 5 m), by the highest concentration in phospholipid (about 20%, as the result of the enzymatic assay), by X-ray emission from phosphorus atoms, as the result of EDS analysis and by phospholipid transition peak, as the result of DSC analysis. These findings can indicate the presence of phospholipid aggregates such as liposomes.Conclusion: Melt technique involved in liposphere preparation can lead to the formation of alternative phospholipid structures. Their detection and removal has to be taken into account in order to obtain omogeneous samples having the desired properties.