Engineered antifouling microtopographies: kinetic analysis of the attachment of zoospores of the green alga Ulva to silicone elastomers.

Microtopography has been demonstrated as an effective deterrent to biofouling. The majority of published studies are fixed-time assays that raise questions regarding the kinetics of the attachment process. This study investigated the time-dependent attachment density of zoospores of Ulva, in a laboratory assay, on a micropatterned and smooth silicone elastomer. The attachment density of zoospores was reduced on average 70-80% by the microtopography relative to smooth surfaces over a 4 h exposure. Mapping the zoospore locations on the topography revealed that they settled preferentially in specific, recessed areas of the pattern. The kinetic data fit, with high correlation (r(2) > 0.9), models commonly used to describe the adhesion of bacteria to surfaces. The grouping of spores on the microtopography indicated that the pattern inhibited the ability of attached spores to recruit neighbors. This study demonstrates that the antifouling mechanism of topographies may involve disruption of the cooperative effects exhibited by fouling organisms such as Ulva.

Engineered antifouling microtopographies: the role of Reynolds number in a model that predicts attachment of zoospores of Ulva and cells of Cobetia marina.

A correlation between the attachment density of cells from two phylogenetic groups (prokaryotic Bacteria and eukaryotic Plantae), with surface roughness is reported for the first time. The results represent a paradigm shift in the understanding of cell attachment, which is a critical step in the biofouling process. The model predicts that the attachment densities of zoospores of the green alga, Ulva, and cells of the marine bacterium, Cobetia marina, scale inversely with surface roughness. The size and motility of the bacterial cells and algal spores were incorporated into the attachment model by multiplying the engineered roughness index (ERI(II)), which is a representation of surface energy, by the Reynolds number (Re) of the cells. The results showed a negative linear correlation of normalized, transformed attachment density for both organisms with ERI(II) x Re (R(2) = 0.77). These studies demonstrate for the first time that organisms respond in a uniform manner to a model, which incorporates surface energy and the Reynolds number of the organism.