Tunable underwater curcumin release through a three-layered film system to mitigate oxidative stress in corals

Coral bleaching, primarily driven by thermal stress and oxidative damage, threatens reef ecosystems worldwide. In this article, an eco-friendly, biocompatible, three-layered film system for controlled underwater delivery of curcumin directly to corals is proposed. This multilayered structure enables tunable, continuous, and directional drug release through a curcumin–β-cyclodextrin-complexed nanocarrier. Morphological, chemical, and mechanical analyses confirmed the system's structural integrity, water-absorption capacity, and hydrogel-like behavior, making it suitable for underwater applications. In vivo tests on Stylophora pistillata under a four-phase bleaching setup showed that, even without direct contact, the film may contribute to mitigating oxidative stress in corals, as evidenced by higher chlorophyll content, greater Symbiodiniaceae density, and reduced lipid peroxidation compared with untreated stressed corals. Overall, these results indicate a technology maturity corresponding to a technology readiness levels of 4–5 and demonstrate the potential of underwater drug delivery platforms for controlled and sustained release of antioxidants to mitigate oxidative stress in corals and, potentially, other marine species.