Stability of lipid excipients in solid lipid nanoparticles.

The paper is devoted to the investigation of chemical stability of lipids used as excipients in the production of Solid Lipid Nanoparticles (SLN). Different lipids and amounts of surfactants were considered. Most of the formulations were produced using identical binary surfactant mixtures and concentrations to analyze the effect of the chemical nature of the lipids on their stability in SLN. In some formulations, surfactants were exchanged or their concentration was increased to assess the contribution of surfactants on stability of lipids particles. Solid Lipid Nanoparticles were characterized by photon correlation spectroscopy, laser diffractometry, zeta potential determination and differential scanning calorimetry. Potential effects of lipid crystallinity and modifications were assessed. A gas chromatography (GC) analysis in combination with a method for lipid extraction from aqueous SLN dispersions was used to investigate the chemical stability of the lipid excipients forming the particle matrix. All formulations were produced by the hot homogenization technique. The production process of SLN itself did not affect the chemical stability of lipid excipient forming the particle matrix. The formulations where lipids consisted of trigylicerides showed a negligible decomposition of the structure during incubation at 25 degrees C. Dynasan 118 showed the highest chemical stability (loss<4%) within two years.