Synergistic Effects of Hydroxyapatite Derived from Fish Bone and Tinosorb® S on the UV Protection Performance of Sunscreen

Sunscreens are essential for photoprotection, but conventional inorganic UV filters raise concerns regarding marine toxicity. This study investigated hydroxyapatite (HAp) derived from skipjack, tongol, and salmon bone waste as a potential synergistic booster for Tinosorb® S (TS). HAp powders were prepared via alkaline treatment and calcination at 900 °C. XRD and XRF results confirmed highly crystalline HAp as the dominant phase. While 10% HAp alone provided negligible UV protection, a pronounced synergistic effect was observed in 1:1 hybrid formulations (5% HAp:5% TS), significantly enhancing Sun Protection Factor (SPF) and Ultraviolet A Protection Factor (UVAPF). Notably, particle-size refinement of salmon-derived HAp (SM–HAp) yielded an SPF of approximately 35, comparable to a commercial HAp counterpart. This improvement was suggested to be associated with enhanced dispersion, film uniformity, and particle–matrix interactions, which might contribute to achieving PA++++ protection. All formulations complied with microbiological and heavy metal safety standards. These results indicated that fish bone-derived HAp could potentially serve as a viable and sustainable functional additive derived from marine biowaste for the development of high-performance hybrid sunscreens, promoting biomaterial valorization in the cosmetic industry.