The sunscreen agent, butyl methoxydibenzoylmethane (BMDBM), one of the most widely used UV-A filter, undergoes decomposition under sunlight exposure, which is a limiting factor on its overall performance. To reduce the sunscreen photodegradation, this study investigates the incorporation into solid lipid microparticles (SLMs) of BMDBM together with the photostabilizer, 4-methylbenzylidene camphor (MBC). The microparticles were produced by the melt dispersion technique using various lipid materials (tristearin, glyceryl behenate, and stearic acid) and hydrogenated phosphatidylcholine as the surfactant. The highest retention capacity for BMDBM and MBC was achieved with tristearin microparticles. These SLMs were characterized by scanning electron microscopy and powder X-ray diffraction analyses. The BMDBM and MBC loading was 10.4 and 10.1%, respectively. The efficacy of the SLMs was evaluated after their introduction in a conventional cream (oil-in-water emulsion). The light-induced decomposition of BMDBM was decreased by encapsulation into the SLMs (the extent of degradation was 33.8 ± 5.5% for unencapsulated BMDBM/MBC and 25.3 ± 4.2% for BMDBM-loaded microparticles in conjunction with free MBC). Moreover, the co-loading of the MBC stabilizer in the SLMs produced a further reduction of the photodegradation of the UV-A filter (the BMDBM loss was 16.9 ± 5.9%) compared with the microparticles containing BMDBM without MBC. Therefore, incorporation in lipid microparticles of BMDBM together with the MBC photostabilizer is more effective in enhancing the UV-A filter photostability than the SLMs loaded with BMDBM alone.
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