Polyamide Nanocapsules and Nano-emulsions Containing Parsol® MCX and Parsol® 1789: In Vitro Release, Ex Vivo Skin Penetration and Photo-Stability Studies

To prepare polyamide nanocapsules for skin photo-protection, encapsulating alpha-tocopherol, ParsolA (R) MCX (ethylhexyl methoxycinnamate) and/or ParsolA (R) 1789 (butyl methoxydibenzoylmethane). Nanocapsules were obtained by combining spontaneous emulsification and interfacial polycondensation reaction between sebacoyl chloride and diethylenetriamine. Nano-emulsions used as control were obtained by the same process without monomers. The influence of carrier on release rate was studied in vitro with a membrane-free model. Epidermal penetration of encapsulated sunscreens was ex vivo evaluated using Franz diffusion cells. Ability of encapsulated sunscreens to improve photo-stability was verified by comparing percentage of degradation after UV radiation exposure. Sunscreen-containing nanocapsules (260-400 nm) were successfully prepared; yield of encapsulation was > 98%. ParsolA (R) MCX and ParsolA (R) 1789 encapsulation led to decreased release rate by up to 60% in comparison with nano-emulsion and allowed minimum penetration through pig ear epidermis. Presence of polyamide shell protected encapsulated sunscreen filters from photo-degradation without affecting their activity. Encapsulation of ParsolA (R) MCX and ParsolA (R) 1789 into oil-core of polyamide nanocapsules allowed protection from photo-degradation, controlled release from nanocapsules, and limited penetration through pig ear epidermis.