Noradrenaline deters marine invertebrate biofouling when covalently bound in polymeric coatings Neeraj V. Gohad a,1 , Nihar M. Shah b,1,2 , Andrew T. Metters c , Andrew S. Mount a, ⁎ a Okeanos Research Group, Department of Biological Sciences, 132 Long Hall, Clemson University, Clemson, SC 29634, USA b Department of Bioengineering, 301 Rhodes Research Center, Clemson University Clemson, SC 29634, USA c Department of Chemical and Biomolecular Engineering, 127 Earle Hall, Clemson, SC 29634, USA abstract article info Article history: Received 25 May 2010 Received in revised form 19 July 2010 Accepted 20 July 2010 Keywords: Antifouling coatings Balanus amphitrite Crassostrea virginica Fouling deterrence Polymer coatings Marine biofouling is the unwanted accumulation of marine organisms on submerged structures and ships. Attempts to develop effective marine antifouling paints and coatings have had deleterious effects on marine and aquatic ecosystems. Current research efforts for designing an effective antifouling coating are focused on understanding the biology of the fouling organisms. Prior to settlement and metamorphosis, larvae of many marine invertebrates investigate surfaces using exploratory structures bearing an array of sensory cells. Interfering with these settlement and attachment mechanisms could be a promising alternative to existing antifouling strategies. Herein, we report the innovation of “fouling deterrence”, an antifouling strategy in which marine invertebrate larval exploratory behaviors are exploited to defeat biofouling. Our approach is predicated upon larval recognition of covalently bound ligands, such as the catecholamine, noradrenaline which presents ‘unfavorable’ cues to deter larval settlement. To test this concept, we developed noradrenaline conjugated poly-HEMA (hydroxyethylmethacrylate) and poly-MAA (methacrylic acid) polymer systems. The bioactivity of covalently conjugated noradrenaline molecules was assessed using oyster hemocyte cellular assays followed by larval settlement assays using pediveliger larvae of the Eastern Oyster, Crassostrea virginica and the cyprid larvae of the barnacle, Balanus amphitrite. Noradrenaline conjugated polymer surfaces induced apoptosis in oyster hemocytes and deterred larval settlement in both oysters and barnacles. Published by Elsevier B.V. 1. Introduction Marine biofouling is the unwanted accumulation of bacteria, algae, plants and marine animals on submerged structures including maritime vessels. It causes an increased drag on ships, incurring in cases of heavy calcareous fouling of up to 86% powering penalty at cruising speed (Schultz, 2007). If left unchecked, the growth of these fouling communities leads to structural disintegration, corrosion and ultimately failure of immersed structures. Biofouling has plagued mankind throughout its history, and is not limited to the marine environment. The unintentional introduction of non-native opportu- nistic calcareous macrofoulers such as the zebra mussel now threatens water intakes of power production facilities in freshwater environments throughout the American Midwest (Angarano et al., 2007). Unfortunately, man's attempts to develop effective marine antifouling paints and coatings have had deleterious effects on marine and aquatic ecosystems. In the 1950s triorganotin biocide such as tributyltin (TBT) based paints were introduced and are estimated to cover 70% of today's world fleet (Yebra et al., 2004). Leaching of TBT from these paints resulted in devastating effects on marine biota. TBT at concentrations as low as 1 ng/l causes imposex, such as the imposition of male genitalia in females of the dog-whelk, Nucella lapillus (Folsviksrk et al., 1999; Yebra et al., 2004). It also accumulates in the sediment resulting in long lasting impacts, causing shell deformities in the Pacific Oyster Crassostrea gigas at a concentration of 20 ng/l. In 2008, the United Nations Law of the Sea banned the use of TBT based antifouling paints on maritime vessels (Chambers et al., 2006; Yebra et al., 2004). Today, copper based ablative antifouling coatings have mostly replaced the TBT based paints. These paints incorporate cuprous oxide along with organometallic co-biocides (Yebra et al., 2004). Although copper is less toxic than TBT it also poses significant hazards to the marine environment. Typically, the commercial products release copper anywhere from 8 to 48 μg/cm 2 /day (Finnie, 2006; Valkirs et al., 2003). It has been estimated that upwards 3000 t of copper is released per year from ships at sea (Almeida et al., 2007). This amount poses a Journal of Experimental Marine Biology and Ecology 394 (2010) 63–73 ⁎ Corresponding author. Tel.: + 1 864 656 3597; fax: + 1 864 656 0435. E-mail address: mount@clemson.edu (A.S. Mount). 1 Authors contributed equally. 2 Present Address: Department of Surgical & Radiological Sciences, 1220 Tupper Hall, School of Veterinary Medicine University of California Davis, CA 95616, USA. 0022-0981/$ – see front matter. Published by Elsevier B.V. doi:10.1016/j.jembe.2010.07.014 Contents lists available at ScienceDirect Journal of Experimental Marine Biology and Ecology journal homepage: www.elsevier.com/locate/jembe