Eco-friendly active film and sealant for underwater drug delivery to diseased corals

<h2>Summary</h2> Coral disease outbreaks have become a persistent threat to reefs, being more frequent and destructive in affecting these natural ecosystems but also coral nurseries and the aquaria business. To prevent catastrophic scenarios, effective technologies to treat outbreaks must be promptly implemented. We developed an eco-friendly underwater drug-delivery system to efficiently treat bacterial infections in corals. This system, composed of a hydrophilic film with 1% (w/w) antibiotic and a hydrophobic bio-based sealant, can be easily applied to infected areas, swiftly healing diseased corals while preventing drug leakage into the environment. The design was optimized to ensure monodirectional drug release to the infected coral tissue within 1 week of treatment, addressing the infected coral tissue and preventing environmental release. This technology successfully inhibited <i>in vitro</i> growth of <i>Vibrio coralliilyticus</i> and halted the progression of tissue-necrosis-like symptoms in 90% of aquarium corals tested, serving as a milestone for future developments and applications.