Polysaccharide coatings unlock high-performance TiO2 UV filters for sunscreen formulations

Designing mineral ultraviolet (UV) filters that combine strong UV absorption and photostability remains an open challenge. Conventional silica coatings only partially mitigate the photocatalytic activity of titanium dioxide (TiO2) and rely on energy-intensive synthesis. Here, we introduce a room-temperature, surfactant-free dissolution–precipitation strategy that yields α−1,3-glucan- and ethylcellulose-coated TiO2 core–shell particles. Spectroscopy and density functional theory indicate that these biopolymer shells improve nanoparticle dispersion and reduce interfacial charge transfer pathways that generate reactive oxygen species, while maintaining strong UV absorption. The resulting core-shell particles demonstrate up to ~2× higher UV absorbance, while the ethylcellulose and glucan shells enhance emulsion stability. The dissolution-precipitation strategy thus delivers UV protection, photocatalytic activity, and emulsion stability in one coating. Mineral UV filters with strong UV protection and photostability remain challenging. Here, the authors develop biopolymer‑coated titanium dioxide particles that doubled ultraviolet absorption while reducing reactive oxygen species formation and improving emulsion stability.