Stability of marine lipid based-liposomes under Acid conditions. Influence of xanthan gum.

Liposomes are potential candidates in Human nutrition to supplement diets in essential lipo- and hydro-soluble nutriments. In this context, marine lipid based-vesicles, rich in polyunsaturated fatty acids, and containing vitamin B1 (thiamine) were prepared. Two methods were envisaged for vitamin trapping, passive encapsulation and active loading through the use of a transmembrane pH gradient. These methods were compared in terms of thiamine trapping efficiency. Influence of xanthan addition was also studied. Although, the active loading yielded to higher encapsulation ratios than the passive method, encapsulation efficiency was markedly increased, in both cases, as soon as the hydrocolloid was added after the lipid hydration phase. Liposome stability was assayed by microscopy observation and membrane permeability to thiamine in a medium that mimic that faced by the structures administrated by the oral route, i.e., an acid pH medium, as in the Human stomach. Low pH value led to an instantaneous vesicle aggregation. Thiamine was totally released from liposomes prepared without xanthan after 24 h storage in a neutral medium. This time was shortened to 1 h at pH 1.5. However, thiamine retention was significantly improved when liposomes were prepared in presence of the hydrocolloid, whatever the encapsulation method used. On the whole, these results were interpreted in terms of xanthan coating around the liposome surface that would result from lipid-hydrocolloid interactions occurring during the centrifugation steps of liposome preparation.