Design of multifunctional nanostructured lipid carriers enriched with α-tocopherol using vegetable oils

Vegetable oils are commonly used as components in many cosmetic products intended for daily care due to their high beneficial and multifunctional effect on skin. The general objective of this study was to develop new nanostructured lipid carrier (NLC) formulations containing vegetable oils and enrich them with alpha-tocopherol (TOC) in order to explore their potential as effective and safe advanced biocosmetic prototypes. The influence of lipids composition and physical state on the production and physicochemical properties of vegetable oil NLCs and enriched nanoparticles with TOC (TOC-NLCs), as a model bioactive antioxidant compound, was studied. Sunflower, sweet almond, olive and coconut oils were successfully used in the development of free and loaded NLCs. The formulations of free lipid nanoparticles with each vegetable oil presented an appropriate nanoscale size from approximately 120-350 nm and good physical stability with zeta potential values ranging between - 45.6 to -65.9 mV. Likewise, the TOC-NLCs demonstrated suitable particle sizes from approximately 240-315 nm and zeta potential values raging between -45.6 to -55.1 my, being then verified that these parameters were affected by differences on the lipids core composition. TOC-NLCs presented a high entrapment efficiency with values above 79.4% and also assured a controlled release of TOC, independently of the percentage of incorporated active compound. Differential scanning calorimetry results showed that the incorporation of TOC and the increase of its concentration on NLCs lipids matrix caused a decrease on the onset and melting temperatures, indicating a reduced crystallinity of the obtained vegetable oil TOC-NLCs. These lipid nanoparticles and free NLCs presented good antioxidant activity with scavenging activity values above 56.7%, which was improved by the encapsulation of TOC (scavenging activity values above 64.3%) and demonstrated the ability to be incorporated in long-term stable cosmetic products based on stability studies performed during 8 months.