Photo and Thermal Stable Lignin-Based Sunscreen Microcapsules

Lignin-based microcapsules exhibit promising potential among natural sunscreen agents. However, their applications are hindered by poor photostability and biocompatibility of core materials. Here, we optimize the core formulation of lignin microcapsules to improve their stability and biocompatibility. A novel core formulation including four chemical sunscreen actives is encapsulated in enzymatic hydrolysis lignin (EHL) via one-step ultrasonic cavitation. Optimal microcapsules with an average diameter of 383 nm are obtained, and the formulated creams with 10 wt % EHL microcapsules as the sole active ingredient achieve a sun protection factor (SPF) value of 147. Due to the excellent photo and thermal stability of the optimized core formulation, the SPF value of the microcapsule-based sunscreen decreases by only 14.7% after 10 h of UV irradiation, while it has little change under 50 °C. Due to the above advantages and good biocompatibility, the proposed EHL-based microcapsules have better potential in developing natural sunscreen.