Biomineralization: A new tool for developing eco-sustainable Ti-doped hydroxyapatite-based hybrid UV filters.

It is well known that the prolonged exposure to UV radiation from sunlight can compromise human health and isparticularly damaging to the skin, leading to sunburn, photo-aging and skin cancer. Sunscreen formulationscontaining UV-filters present a barrier against solar UV and help to mitigate the harmful effects however, concernabout their safety for both human and environmental health is still a much-debated topic. EC regulations classifyUV-filters depending on their chemical nature, particle size, and mechanism of action. Furthermore, it regulatestheir use in cosmetic products with specific limitations in terms of concentration (organic UV filters) and particlesize and surface modification to reduce their photo-activity (mineral UV filters). The regulations have promptedresearchers to identify new materials that show promise for use in sunscreens. In this work, biomimetic hybridmaterials composed of titanium-doped hydroxyapatite (TiHA) grown on two different organic templates, derivedfrom animal (gelatin - from pig skin) and vegetable (alginate - from algae) sources. These novel materials weredeveloped and characterized to obtain sustainable UV-filters as a safer alternative for both human and ecosystemhealth. This 'biomineralization' process yielded TiHA nanoparticles that demonstrated high UV reflectance, lowphotoactivity, good biocompatibility and an aggregate morphology which prevents dermal penetration. Thematerials are safe for topical application and for the marine environment; moreover, they can protect organicsunscreen components from photodegradation and yield long-lasting protection.