Colloidla lipid suspensions are considered to be a promising drug delivery system, e.g., for parenteral, peroral and dermal applications. Aqueous suspensions of solid lipid nano-particles can be obtained by high pressure homogenization of melted lipids with adequate stabilizers followed by crystallization of the dispersed lipids. Triglyceride dispersions stabilized exclusively with phospholipids may, howeve,r form semi-solid gels during the cooling process after homogenization. This is an undesirable effect at least in formulations for parenteral administration, that can be avoided by adding co-surfactacnts (e.g., bile salts or poloxamers). Optimized gel compositions might, however, be considered as interesting warterrich semi-solid formulations for drug delviery purposes. It was supposed that the gel formation can be attributed to the recrystallization of the melt-homogenized triglycerides (1), but the mechanism of gel formation has not yet been investigated in detail. The temperature dependence of gel formation and the influence of different phospholipid qualities on gelation are the subject of the present study.
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