Preparation and Characterization of Microcapsules Encapsulating Octyl Methoxycinnamate by Complex Coacervation

The aim of this study was to entrap the lipophilic ultraviolet absorber, octyl methoxycinnamate in microcapsuels to enhance its application. A complex coacervation method was established. Through the appearance of encapsulated glass beads prepared with different wall materials, gelatin and sodium polyphosphate were selected as wall materials because of dense structure and less adhesion. The effects of three variables, core/ (core+wall) ratio, pH at complex coacervation, and amount of cross-linking agent, on encapsulation efficiency were studied. Response surface methodology was employed to optimize the technology, and a polynomial regression model equation was generated. The optimization method enabled to predict the response variable value within the experimental range with good agreement between the predicted and experimental values. The microcapsules under the optimized conditions appeared spherical in shape with smooth nonporous surface and no tendency to aggregation. The photodegradation percentage of octyl methoxycinnamate after exposing to ultraviolet irradiation was determined and the transdermal permeation pattern of octyl methoxycinnamate and its photodegradation product from various formulations was estimated in vitro. From the results obtained, the microcapsules had achieved decreasing transdermal permeation of octyl methoxycinnamate and its photodegradation product, enhancing the accumulation of the sunscreen at the administration site, and then increasing the protection effect and safety. This study revealed the potential of sunscreen microcapsules as new skin drug delivery systems.