Electrolyte- and pH-stabilities of aqueous solid lipid nanoparticle (SLN) dispersions in artificial gastrointestinal media.

The influence of artificial gastrointestinal (GI) media on the physical stability of solid lipid nanoparticle (SLN) formulations consisting of different lipids and various surfactants/stabilizers has been investigated in vitro, with respect to ionic strength and pH. Laser diffractometry and zeta potential measurements were the techniques applied. Some SLN formulations already showed aggregation/particle growth in the presence of electrolytes at neutral pH. Other lipid nanodispersions remained physically stable with respect to the influence of electrolytes, but were pH-sensitive. It was possible to produce SLN that were GIT (gastrointestinal tract) stable by an optimized stabilizer composition. There is no optimal surfactant mixture for stabilization of any lipid, e.g. SLN consisting of the lipid Cutina CP showed GIT stability in combination with the stabilizer sugar ester S1670, whereas the stabilization with the surfactant mixture Tween 80/Span 85 was not effective. Vice versa, the emulsifier Pluronic F68 stabilized the lipid Compritol ATO 888 but not the lipid Imwitor 900 sufficiently to avoid aggregation of the SLN dispersion in artificial GI media. The stabilizing properties depend obviously on the specific interactions of the lipid matrix with the emulsifier, e.g. anchoring of the stabilizer on the lipid surface and density on the surface.