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Biomimetic antifouling coating


Biomimetic antifouling coatings are special coatings that prevent the accumulation of marine organisms on a surface. Typical antifouling coatings are not biomimetic but are based on synthetic chemical compounds that can have deleterious effects on the environment. Prime examples are tributyltin compounds, which are components in paints to prevent biofouling of ship hulls. Although highly effective at combatting the accumulation of barnacles and other problematic organisms, organotin-containing paints are damaging to many organisms and have been shown to interrupt marine food chains.

Most antifouling coatings are based upon chemical compounds that inhibit fouling. When incorporated into marine coatings, these biocides leech into the immediate surroundings and minimize fouling. The classic synthetic antifouling agent is TBT. Natural biocides typically show lower environmental impact but variable effectiveness.

Natural biocides are found in a variety of sources, including (sponges, algae, corals, sea urchins, bacteria, and sea-squirts), and include toxins, anaesthetics, and growth/attachment/metamorphosis-inhibiting molecules. As a group, marine microalgae alone produce over 3600 secondary metabolites that play complex ecological roles including defense from predators, as well as antifouling protection, increasing scientific interest in the screening of marine natural products as natural biocides. Natural biocides are typically divided into two categories: terpenes (often containing unsaturated ligand groups and electronegative oxygen functional groups) and nonterpenes.

Various tannins (nonterpene), naturally synthesized by a variety of plants, are effective biocides when combined with copper and zinc salts. The tannins are able to flocculate with a variety of cations, which then exhibit antiseptic properties. The most effective natural biocide is 3,4-dihydroxybufa-20,22 dienolide, or bufalin (a steroid of toad poison from Bufo vulgaris), which is over 100 times more effective than TBT at preventing biofouling. Bufalin is however expensive. A few natural compounds with simpler synthetic routes, such as nicotinamide or 2,5,6-tribromo-1-methylgramine (from Zoobotryon pellucidum), have been incorporated into patented antifouling paints.


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