Conventional emulsion‐based sunscreen formulations are limited by postapplication epicutaneous penetration that increases the risk of allergic dermatitis, cellular damage, and filter photodegradation upon ultraviolet radiation (UVR) exposure. Encapsulation of the UVB filter padimate O within bioadhesive biodegradable nanoparticles (BNPs) composed of poly(d,l‐lactic acid)‐hyperbranched polyglycerol was previously shown to enhance UVR protection while preventing skin absorption. Herein, we assess the capacity of BNP co‐incorporation of avobenzone and octocrylene to provide broad‐spectrum UVR protection. The ratio of UV filters within nanoparticles (NPs) was optimized for filter–filter stabilization upon UV irradiation and maximum drug loading. In vitro water‐resistance test showed significant particle retention at 85% over 3 hr. In a pilot clinical study, protection against UVR‐induced erythema of BNPs was found to be comparable to the FDA standard P2. Thus, sunscreen formulations utilizing BNP incorporation of a combination of organic filters may offer key safety and performance advantages.
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