Lignin nanoparticles as sustainable photoprotective carriers for sunscreen filters

Sunscreen filters may be degraded after prolonged UV exposure with loss of their shielding property and generation of harmful radical species. They are contained in cosmetic formulations in high concentrations, so the improvement of photostability is of relevance for safety concerns. We report here that lignin nanoparticles are sustainable carriers and photostabilizers of two common UV chemical filters, namely, avobenzone and octyl methoxycinnamate. These compounds have been encapsulated by nanoprecipitation into kraft lignin nanoparticles using eco-certified dimethyl isosorbide as a primary solvent and deionized water as an antisolvent. After the encapsulation, both compounds significantly prolonged the half-life stability against UV irradiation. The stabilizing properties of lignin nanoparticles were further improved by coencapsulation of avobenzone and octyl methoxycinnamate with hydroxytyrosol, a natural phenol with antioxidant activity recovered from olive oil wastes and characterized by skin regenerative properties.