Solid lipid nanoparticles (SLN) stabilized with polyhydroxy surfactants: Preparation, characterization and physical stability investigation

Polyhydroxy surfactants are nonionic ethylene oxide free stabilizers known for their complimentary dermatological properties and favorable environmental profile. The aim of this study was to develop solid lipid nanoparticles (SLN) stabilized with polyhydroxy surfactants varying in the chemical structure and to investigate the influence of the surfactants on the characteristics of the particles. Particles were produced by hot high pressure homogenization and the physico-chemical properties, e.g. contact angle, particle size, size distribution, zeta potential and crystallinity were determined. Results showed that the chemical structure of the surfactants influences the contact angle, particle size and crystallinity. Furthermore, the low surfactants concentration used (1% (w/w)) allowed the formation of the particles with a mean size below 200 nm, polydispersity index lower than 0.1 and sufficient physical stability for at least 6 months. As postulated by the zeta potential analysis stabilization ability of the surfactants was attributed to the superposition of electrostatic and steric effect which complement each other. All SLN formulations consisted of the same lipid matrix, but were found to possess different crystallinity indices. These differences are obviously created by the differences in the chemical structure of the surfactants. Therefore, the polyhydroxy surfactants investigated in this study can be judged to be novel suitable stabilizers for the formulation of well-skin tolerable SLN. The use of specific chemical structures of the surfactants can be used for the production of “tailor-made” SLN in the future.