Multivariate Analysis of Attachment of Biofouling Organisms in Response to Xerogel Surface Properties and the Design of Environmentally Friendly Antifouling Xerogel Coatings
Montross, Caitlyn Marie
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Biofouling is the accumulation of organisms on submerged surfaces. This accumulation negatively impacts the performance of ships, submarines, and other objects that must move efficiently through the water. Due to increased environmental concern and new regulations, the need for environmentally friendly antifouling coatings has greatly increased. Positively charged halide species can act as negative settlement cues towards fouling organisms and though these species are naturally produced in seawater through oxidation by H 2 O 2 , the reaction is slow. Organo-selenium compounds have been shown in activate H 2 O 2 and increase the production of positively charged bromine species. Selenide and diselenide compounds were functionalized with silane moieties and incorporated into xerogel coatings through a siloxane bond. The compounds were analyzed to determine their durability and rate of positively charged bromine production. The antifouling effect of the robust diselenide catalyst was investigated through settlement assays with U. linza zoospores in the absence and presence of H 2 O 2 . While the diselenide catalyst produced positively charged bromine species at a rate over 40× greater than the reaction without a catalyst, the bromine production was not sufficient enough to deter the organisms from settling. Non-toxic non-fouling coatings offers another environmentally friendly alternative to antifouling paints. The ability to generate a surface capable of deterring organismal attachment based on surface chemistries is hindered by our lack of knowledge of the fouling organisms. To better understand what surface properties drive attachment across multiple fouling organisms, a library of xerogel coatings, spanning a wide range of surface properties, were prepared and attachment/adhesion of 5 fouling species was investigated. Results from the surface characterization and biological assays were analyzed separately and in combination using multivariate statistical methods. Canonical analysis of principal coordinates (CAP) was used to identify important materials properties governing attachment across all 5 species. The CAP pointed to surface energy, the dispersive component of surface energy, and surface charge as important surface properties influencing organismal attachment. The same library of xerogel coatings were also deployed in the field for 1, 3, and 5 days and the influence of surface properties on the attachment of fouling organisms was investigated. Over the course of the experiment, surface energy and the threshold of the dispersive component of surface energy appeared to become more influential and significantly influenced attachment at 3 and 5 days. Negatively charged surfaces were distinguishable from neutral surfaces during the course of the experiment, while positively charged surfaces were not as easily distinguishable from neutral surfaces. To better understand the sensory architecture of barnacle A. amphitrite, and in turn use the information for future coating designs, a small library of xerogel surfaces were utilized in attachment assays with maternal families of A. amphitrite cyprids. Initial results indicate the cyprids used one “hypothetical” sensory system to discriminate among all of the xerogel surfaces (with the exception of distinguishing the COE surface from the TFP surface), regardless of the surface chemistries present on the surface. Additionally, two different “hypothetical” sensory systems were used to distinguish xerogel surfaces from plain glass (with the exception of COE and Glass, where the same “hypothetical” sensory system was used). The results indicate there is a uniqueness to our xerogel surfaces, a property that has yet to be identified.