Effect of gastrointestinal digestion on the stability and cytotoxicity of conventional and pegylated liposomes encapsulated with stigmasterol and its esters.

Conventional and PEGylated liposomes encapsulated with stigmasterol and its esters were prepared, and their stability and cytotoxicity during in vitro gastrointestinal digestion were determined. The release of stigmasterol and its oxidation products were analyzed using GC-FID. The cytotoxicity before and after digestion was assessed using human normal small intestinal HIEC-6 cells and colon mucosa CCD 841CoN cells. Both liposome PEGylation and the chemical structure of the encapsulated compounds affect the stability and cytotoxicity of the liposomes after gastrointestinal digestion. Esterification of stigmasterol had an effect on the encapsulation of stigmasterol in liposomes, especially PEGylated liposomes, but the level of fatty acid saturation had no significant influence. PEGylation of liposomes did not inhibit sterol oxidation, but in fact led to the formation of oxidation derivatives. Gastrointestinal digestion increased the cytotoxicity of liposomes with stigmasterol (L-St), but liposomes encapsulated with stigmasterol esters had lower cytotoxicity than did undigested liposomes. PEGylation of liposomes did not cause an increase in cytotoxicity to the small intestinal or colon mucosa cells. However, it should be highlighted that the cytotoxic effects of the digested PEGylated liposomes were considerable higher in colon CCD 841CoN cells than in small intestinal HIEC-6 cells.