Engineered Nanoforce Gradients for Inhibition of Settlement (Attachment) of Swimming Algal Spores

Abstract

Current antifouling strategies are focused on the development of environmentally friendly coatings that protect submerged surfaces from the accumulation of colonizing organisms (i.e., biofouling). One ecofriendly approach is the manipulation of the surface topography on nontoxic materials to deter settlement of the dispersal stages of fouling organisms. The identification of effective antifouling topographies typically occurs through trial-and-error rather than predictive models. We present a model and design methodology for the identification of nontoxic, antifouling surface topographies for use in the marine environment by the creation of engineered nanoforce gradients. The design and fabrication of these gradients incorporate discrete micrometer-sized features that are associated with the species-specific surface design technique of engineered topography and the concepts of mechanotransduction. The effectiveness of designed nanoforce gradients for antifouling applications was tested by evaluating the settlement behavior of zoospores of the alga Ulva linza. The surfaces with nanoforce gradients ranging from 125 to 374 nN all significantly reduced spore settlement relative to a smooth substrate, with the highest reduction, 53%, measured on the 374 nN gradient surface. These results confirm that the designed nanoforce gradients may be an effective tool and predictive model for the design of unique nontoxic, nonfouling surfaces for marine applications as well as biomedical surfaces in the physiological environment.

Microtopography of the eye surface of the crab Carcinus maenas : an atomic force microscope study suggesting a possible antifouling potential

“…Three key elements prevent biofouling attachment to surfaces: (i) cells/organisms must remain above topographical features and not be able to settle between them; (ii) they must not be able to contact and settle their entire structure on a single feature; and (iii) if they bridge two features, then they must not be able to contact the intervening floor [25]. Crab eye morphology shows deep narrow channels (approx.…”

Progress of marine biofouling and antifouling technologies

“…Many other phenomena observed during microorganism settlement on self-assembled monolayers [121,144] can be partly explained by electrostatic interactions [145,146]. Discharge treatment can be used to create carboxylic acid groups on polymer surfaces [147], which can also be discussed in terms of the repulsive electrostatic interactions [148].…”

Reduced bacterial adhesion on titanium surfaces micro-structured by ultra-short pulsed laser ablation

“…reduction of structural dimensions can increase the antiadhesive effect, because bacterial cells will experience intracellular stress gradients proposed by Schumacher et al [15]. This question will be clarified in further studies.…”

“…Afterwards, their effectiveness was also proven for bacterial attachment [8][9][10][11][12]. The mechanism proposed to explain inhibition of algal spore attachment -the increasing of intracellular stress gradients due to cell contact with two geometrically different features [15] -cannot be used for explanation of reduced bacterial attachment. The dimension of a single bacterial cell (e.g.…”

“…The exact mechanism of the Sharklet™ effect has not yet been completely understood. It is hypothesized that particular arrangement of topographical features with appropriate dimensions create a stress gradient within the cell membrane during initial contact resulting in lower attachment rates [15]. Therefore, in addition to Sharklet™, groove and grid structures, which have similar dimensions, were examined.…”