Green synthesis of lignin/DHHB sunscreen nanoparticles with enhanced stability and reduced skin permeability

Diethylamino hydroxybenzoyl hexyl benzoate (DHHB) is a high-performance UVA absorber widely used to protect skin from ultraviolet radiation. However, its application is hindered by several limitations with insufficient photostability, a narrow UV absorption range, and high skin permeability. To address these challenges, we prepared alkali lignin-encapsulated DHHB nanoparticles (AL/DHHB) by using an environmentally friendly ethanol/water system through a simple solvent-antisolvent method. The effects of ethanol/water ratio, dripping speed, and lignin/DHHB ratio on the structure and properties of the nanoparticles were systematically investigated. The sun protection performance, photostability, and permeability of AL/DHHB nanoparticles were explored. The resulting AL/DHHB nanoparticles demonstrated broad-spectrum ultraviolet protection, with initial sun protection factor of 38.5. Furthermore, it exhibited excellent photostability, maintaining functionality for up to 10.5 h under continuous ultraviolet radiation exposure, and significantly reduced the skin penetration risk of DHHB. This study provides a promising strategy and practical foundation for developing high-performance, safe, and eco-friendly bio-based sunscreen products.