Researchers at South China University of Technology have developed sunscreens using lignin from wood that achieve sun protection factors exceeding 180. These formulations also offer longer-lasting protection and reduced skin penetration compared to traditional products. The innovation addresses growing concerns about the safety of common sunscreen chemicals.
Concerns about the safety of conventional sunscreens have intensified following US Food and Drug Administration research indicating that several ingredients can enter the bloodstream. A recent survey revealed that 14 percent of young adults believe daily sunscreen application poses greater harm than direct sun exposure. Although long-term studies show no associated risks, regulators have urged further investigation. Additionally, these chemicals may harm marine ecosystems like coral reefs when washed off.
In response, scientists are exploring natural alternatives, with lignin—a substance that strengthens plant cell walls and shields them from ultraviolet radiation—emerging as a top candidate. Extracting lignin without harsh chemicals has been challenging, as traditional methods darken it, rendering it unsuitable for topical use.
Two teams at South China University of Technology overcame this hurdle. Jun Li's group produced pale yellow lignin from poplar wood through milling, sieving, and ultrasonic treatment. Yong Qian's team derived pale pink lignin from birch wood via a similar gentle process. Both converted the lignin into nanoparticles and blended them into creams, yielding broad-spectrum sunscreens with SPF values of 20 and 19, respectively. These protected against both UVA and UVB rays, blended smoothly with skin, and felt pleasant to apply.
To enhance efficacy, Qian's team encapsulated common ingredients avobenzone and octinoxate within lignin nanoparticles, boosting the SPF beyond 180. Note that products cannot be labeled above SPF 50+ due to the scale's limitations. This encapsulation also improved stability under sunlight and prevented skin absorption, potentially enhancing safety.
Qian reports that initial human testing shows the formulation is safe with strong performance. Other natural UV blockers under study include elements from seaweed, ferns, squid, and human hair.
