Marine biofouling represents a global economic and ecological challenge and few eco-friendly antifouling agents are available. The aim of this work was to establish the proof of concept that a recently synthesized nature-inspired compound (gallic acid persulfate, GAP) can act as an eco-friendly and effective antifoulant when immobilized in coatings through a non-release strategy, promoting a long-lasting antifouling effect. The synthesis of GAP was optimized to provide quantitative yields. GAP water solubility was assessed, showing values higher than 1000 mg/mL. GAP was found to be stable in sterilized natural seawater with a half-life (DT50) of 7 months. GAP was immobilized into several commercial coatings, exhibiting high compatibility with different polymeric matrices. Leaching assays of polydimethylsiloxane and polyurethane-based marine coatings containing GAP confirmed that the chemical immobilization of GAP was successful, since releases up to fivefold lower than the conventional releasing systems of polyurethane-based marine coatings were observed. Furthermore, coatings containing immobilized GAP exhibited the most auspicious anti-settlement effect against Mytilus galloprovincialis larvae for the maximum exposure period (40 h) in laboratory trials. Overall, GAP promises to be an agent capable of improving the antifouling activity of several commercial marine coatings with desirable environmental properties.
The most effective strategies to control biofouling release
toxic
and persistent agents into the aquatic environment causing environmental
concerns and leading to the implementation of more strict international
legislation. This work presents recent progress on an innovative eco-friendly
antifouling approach based on the isocyanate-functionalized Econea
biocide allowing its chemical fixation in polymeric frameworks, namely,
in a foul-release marine coating. The antifouling potential of the
generated nonbiocide release coatings for both antimicrobial and long-term
marine anti-biofouling applications is reported here for the first
time. Inhibition growth effects against Methicillin-resistant Staphylococcus aureus bacterium obtained for Econea-based
coatings reveal a decrease in the number of colony forming units (CFUs)
up to 5 orders of magnitude in 6 h of exposure when compared to the
free bacteria. The growth and the viability profiles (CFU/mL) revealed
also bacteriostatic effects. The nonbiocide release coatings were
able to minimize considerably the biocide release, becoming 10-fold
lower than in a conventional releasing system and providing long-lasting
antifouling effects, more than two years, under real seawater conditions.
Both antifouling effects follow a nonbiocide release strategy leading
to a minimization of the environmental impact of the biocidal coatings
and the selective pressure on the microorganisms that evolve treatment
resistance.
Many studies have shown that natural marine compounds can prevent biofouling by a broad spectrum of organisms without toxic effects, encouraging their use in antifouling (AF) coatings. Studies over the past 25 years of the natural product zosteric acid (ZA) are systematically organized in this review. ZA is a sulfated phenolic acid produced by the seagrass Zostera marina that has very promising AF potential against several micro- and macrofouling organisms. ZA was shown to have appropriate environmental fate parameters such as high water solubility, a low log P, low bioaccumulation, and no ecotoxicity, which demonstrated the potential of ZA as a safe AF agent. This review also highlights that ZA has been successfully incorporated into several types of coatings. The synthesis of analogs is also considered in this review, and it has allowed a better understanding of ZA structure-AF activity relationships and clarified the mechanism of action of ZA.
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