Synthesis and sustainable applicability of triangular lignin nanoparticles in sunscreen formulations and UV shielding

Excessive exposure to ultraviolet radiation results in significant skin damage, necessitating the use of sunscreen. However, traditional UV filters face challenges related to photostability, toxicity, and environmental impact. Lignin, a natural polyphenolic biopolymer, presents a sustainable alternative due to its inherent UV absorption and antioxidant properties. This study introduces triangular lignin nanoparticles (TLNPs) in sunscreen formulations, addressing the limitations of spherical lignin nanoparticles by enhancing light scattering, UV protection, and colloidal stability. The synthesized TLNPs exhibit a distinct triangular morphology, superior UV absorption, high stability, and strong antioxidant activity. Moreover, cytotoxicity assessments confirm their safety for topical applications. Sunscreen formulations containing TLNPs demonstrated high sun protection factor (SPF) values reaching 81 ± 1.034 at 10 wt%, exceeding commercial standards while maintaining non-staining properties. Additionally, the prepared formulations exhibited broad-spectrum UV protection. These findings establish TLNPs as an excellent environmentally friendly substitute for synthetic UV filters, advancing sustainable photoprotection strategies.