Preservative system development for argan oil-loaded nanostructured lipid carriers

Nanostructured lipid carriers (NLC) are used in many dermal cosmetic formulations. To prevent microbiological spoilage of NLC suspensions preservative systems must be used. Preservatives can impair the physical stability of NLC suspensions. Therefore, a systematic screening of preservative systems should be performed and the compatibility of these preservative systems with each NLC formulation has to be investigated. In this study three Argan oil-loaded NLC formulations were developed. Ethanol, propylene glycol and pentylene glycol were admixed to these formulations as preservative systems. The physical stability of the non-preserved and preserved formulations has been investigated. Upon admixing 20% w/w ethanol to the selected formulations, immediate particle aggregation could be detected using laser diffractometry and after 24 hours gelling occurred. This was accompanied with a lowering of Zeta potential value. Samples preserved with 10% w/w propylene glycol did not show any change in particle size or in Zeta potential, in comparison to the non-preserved formulation, when measured after one day and 120 days. Samples preserved with 5% pentylene glycol proved also to be stable after 120 days and did not show any change in particle size or Zeta potential.