Hydrophobic DES Based on Menthol and Natural Organic Acids for Use in Antifouling Marine Coatings

Marine biofoulingnegatively impacts industries with off-shoreinfrastructures, such as naval, oil, and aquaculture. To date, thereare no ideal sustainable, economic, and environmentally benign solutionsto deal with this phenomenon. The advances achieved in green solvents,as well as its application in different industries, such as pharmaceuticaland biotechnology, have promoted the emergence of deep eutectic systems(DES). These eutectic systems have applications in various fieldsand can be revolutionary in the marine-based industrial sector. Inthis study, the main objective was to investigate the potential useof hydrophobic DES (HDES) based on menthol and natural organic acidsfor their use as marine antifouling coatings. Our strategy encompassedthe physicochemical characterization of different formulations, whichallowed us to identify the most appropriate molar ratio and intermolecularinteractions for HDES formations. The miscibility of the resultingHDES with the marine coating has been evaluated and proven to be successful.The Men/OL (1:1) system proved to be the most promising in terms ofcost-production and thus was the one used in subsequent antifoulingtests. The cytotoxicity of this HDES was evaluated using an in vitrocell model (HaCat cells) showing no significant toxicity. Furthermore,the application of this system incorporated into coatings that areused in marine structures was also studied using marine species (Mytilus edulis mussels and Patellavulgata limpets) to evaluate both their antifoulingand ecotoxicity effects. HDES Men/OL (1:1) incorporated in marinecoatings was promising in reducing marine macrofouling and also provedto be effective at the level of microfouling without viability impairmentof the tested marine species. It was revealed to be more efficientthan using copper oxide, metallic copper, or ivermectin as antifoulingagents. Biochemical assays performed on marine species showed thatthis HDES does not induce oxidative stress in the tested species.These results are a strong indication of the potential of this HDESto be sustainable and efficiently used in marine fouling control technologies. Marine biofouling negatively impactssubmerged infrastructures,and to date, there are no ideal sustainable, economic, and environmentallybenign solutions to deal with this phenomenon. The results describedherein provide compelling evidence that the use of deep eutectic systemsmay pave the way for alternative antifouling additive agents for marinecoatings. The work that has been reported here gives a clear indicationof the potential of HDES as efficient and sustainable marine foulingcontrol methods.