Chemical stability of lipid excipients in SLN-production of test formulations, characterisation and short-term stability.
The study investigates the chemical stability of lipids used as excipients in the production of solid lipid nanoparticles (SLN). A total of 17 SLN formulations was produced using different lipids. Most of the formulations were produced using identical binary surfactant mixtures and concentrations to study the effect of the chemical nature of the lipid on its stability in SLN. In some formulations surfactants were exchanged to study the contribution of the surfactant. The particles were characterised by photon correlation spectroscopy, laser diffractometry, zeta potential determination and differential scanning calorimetry, the latter to assess potential effects of lipid crystallinity and modifications on lipid stability. Lipid analysis was performed by gas chromatography using a sampling preparation and analysis procedure especially developed for SLN. This short-term study provides primarily information about the stability of the lipid under production conditions, that means high pressure homogenisation (cavitation) at high temperature. No degradation products couldbe detected for all lipids, the production process itself did not impair excipient stability.