Antibiofouling potential of 1-alkyl-3-methylimidazolium ionic liquids: Studies against biofouling barnacle larvae

Abstract

Development of novel and environmental-friendly antifouling compounds is desirable due to the ban on use of tributyltin and concerns on copper and co-biocides. In the current study, antimacrofouling effects of alkylimidazolium ionic liquids on Amphibalanus (=Balanus) reticulatus, a dominant fouling barnacle were assessed. The effect of three alkylimidazolium ionic liquids ([CnMIM]+[X]−, n = 4, 12 and 16) on survival, metamorphosis and settlement of barnacle larvae (nauplii and cypris) was determined in laboratory bioassays. Among the tested ionic liquids, [C12MIM][I] exhibited superior antibiofouling activity with a cypris mortality (LC50) and settlement inhibition (EC50) concentrations of 0.35 μM and 0.39 nM, respectively. [C16MIM][Cl] showed moderate activity with LC50 and EC50 values of 0.63 μM and 1.56 nM, respectively. However, [C4MIM][Cl] exhibited lowest activity on survival and settlement with LC50 and EC50 values of 2.28 μM and 80.2 nM, respectively. The anion (Cl− or I−) did not contribute to the biological activity of ionic liquids. Antifouling activity of the tested ionic liquids on larvae decreased in the following order: [C12MIM][I] > [C16MIM][Cl] > [C4MIM][Cl]. Therapeutic ratios (TR = LC50/EC50) of the tested compounds at >28 to 900 were found to be much higher than the reference value (>15) qualifying them as promising non-toxic or environmentally benign antifoulants. Tested ionic liquids exhibited activity in the similar order ([C12MIM][I] > [C16MIM][Cl] > [C4MIM][Cl]) on survival and metamorphosis of nauplius larvae. EC50 and LC50 concentrations of all the three compounds had no lethal effect on non-target organism, Artemia salina. These data presents possibilities for designing effective and environmental friendly antifouling strategies.