Synergistic lignin-quercetin nano-architectures: Rational design of bio-based systems for multifunctional cosmetics

Developing sustainable, high-performance cosmetic formulations requires a paradigm shift toward multifunctional ingredients that combine efficacy with environmental responsibility. In this work, sustainable cream formulations were rationally designed through the synergistic integration of lignin and quercetin, employing a controlled solvent-exchange precipitation approach optimized via ζ-potential analysis and systematic selection of technical lignins. The resulting lignin-quercetin hybrid system were incorporated into topical formulations and evaluated for their photoprotective, antioxidant and antimicrobial performance. The developed systems exhibited outstanding broad-spectrum ultraviolet (UV) shielding, achieving transmittance profiles comparable to commercial Sun Protection Factor (SPF) 30 formulations, while also promoting safer energy dissipation pathways. In addition, a pronounced synergistic antioxidant effect was observed, preserving the high radical-scavenging activity achieved with 7 wt% free quercetin using only 1.4 wt% quercetin incorporated into the lignin-quercetin hybrid (80% reduction in quercetin content). Furthermore, some formulations showed antimicrobial activity against representative human pathogenic microorganisms with distinct cell wall features and exhibited a cellular viability above 70% in concentrations up to 100 μg·mL^-1 . Overall, these findings establish a robust platform for the development of lignin-based hybrid systems, positioning them as promising candidates for next-generation sustainable cosmetic applications.