Effect of light and temperature on zeta potential and physical stability in solid lipid nanoparticle (SLN™) dispersions

Aqueous dispersions of solid lipid nanoparticles (SLN(TM) are basically stable for up to 3 years, however some systems show particle growth followed by gelation. To assess the destabilizing factors, a poloxamer 188 stabilized Compritol SLN formulation was prepared. Its stability was investigated as a function of storage temperature, light exposure and packing material (untreated and siliconized vials of glass quality I). In general, introduction of energy to the system (temperature, light) led to particle growth and subsequent gelation. This process was accompanied by a decrease in zeta potential from approximately - 25 mV to - 15 mV. The effect of the packing material was less pronounced. However, siliconization of the vials almost eliminated particle growth. By optimization of the storage conditions (8 degrees C, in the dark, siliconized vials), a stability of the less stable aqueous Compritol SLN over 3 years was achieved. (C) 1998 Elsevier Science B.V. All rights reserved.