Influence of encapsulation on the in vitro percutaneous absorption of octyl methoxycinnamate

The purpose of this study was to evaluate the in vitro transdermal permeation and skin accumulation of one ultraviolet (UV) absorber-octyl methoxycinnamate (OMC)-through pig skin and to determine the quantity of OMC in the skin surface and different pig skin layers (stratum corneum, viable epidermis, dermis, and receptor fluid). Four cases have been considered: the application of oil-in-water (O/W) and water-in-oil (W/O) emulsions containing the same filter free and encapsulated in nanocapsules (NC). The influence of the carrier on the percutaneous penetration was studied. Data showed that UV absorber exhibited increases in skin accumulation when is formulated in emulsions in free form. Skin accumulation of OMC-free in the emulsions was significantly (P < 0.05) greater than that of OMC-encapsulated for all formulations investigated. OMC-free skin accumulation ranged from 127.8 +/- 22.8 microg/cm(2) (O/W emulsion) to 172.1 +/- 12.9 microg/cm(2) (W/O emulsion). OMC-encapsulated skin accumulation ranged from 50.3 +/- 13.1 microg/cm(2) to 43.0 +/- 6.5 microg/cm(2) at NC-O/W and NC-W/O, respectively. No significant differences were found in the transdermal permeation of cinnamate for any of the formulations tested. The results of this study demonstrate that the inclusion of OMC-encapsulated in sunscreen formulations decreases the skin accumulation of the cinnamate since the in vitro release mechanism of OMC-nanocapsules is governed by hydrophobicity and crystallinity of the polymer and by the high lipophilicity of the drug. The crystallinity of the polymer have the ability of reflecting and scattering UV radiation on their own thus leading to photoprotection without the need for molecular sunscreens.