Influence of lipid microparticle encapsulation on in vitro efficacy, photostability and water resistance of the sunscreen agents, octyl methoxycinnamate and butyl methoxydibenzoylmethane

Abstract

Context: Essential requirements for the efficacy of sunscreen agents are optimal UV absorption, high photostability and resistance against water removal.Objective: Aim of this study was to investigate the effect of encapsulation in lipid microparticles (LMs) on the overall performance of the two most commonly used sunscreen agents, octyl methoxycinnamate (OMC) and butyl methoxydibenzoylmethane (BMDBM).Methods: LMs loaded with OMC and BMDBM were prepared by melt emulsification and characterized by optical microscopy, UV filter content and release studies. The LMs incorporating OMC and BMDBM or the nonencapsulated sunscreen agents were introduced into a model cream (oil-in-water emulsion).Results: No significant differences were observed between the sun protection factor (SPF) of the formulations containing the free (SPF, 9.4 ± 1.9) or microencapsulated (SPF, 9.6 ± 1.3) UV filters. Irradiation of the creams with a solar simulator demonstrated that the photodecomposition of OMC and BMDBM was significantly decreased by encapsulation in LMs from 55.7 ± 5.3% to 46.1 ± 5.1% and 36.3 ± 3.9% to 20.1 ± 4.7%, respectively. However, in vitro water-resistance studies showed that entrapment in the LMs significantly enhanced the sunscreen agent removal caused by watering (the losses for OMC and BMDBM were 45.1 ± 6.3% and 49.2 ± 8.4%, respectively), as compared to the formulation with the nonencapsulated sunscreen agents (the losses for OMC and BMDBM were 26.7 ± 6.1% and 28.0 ± 6.7%, respectively).Conclusion: Incorporation in LMs can have controversial effects on UV filter efficacy. In particular, the water-resistance properties of sun-care formulations containing sunscreens loaded in LMs should be verified to assure that the photoprotective activity is maintained during usage.