Microfluidic detachment assay to probe the adhesion strength of diatoms

Abstract

Fouling release (FR) coatings are increasingly applied as an environmentally benign alternative for controlling marine biofouling. As the technology relies on removing fouling by water currents created by the motion of ships, weakening of adhesion of adherent organisms is the key design goal for improved coatings. In this paper, a microfluidic shear force assay is used to quantify how easily diatoms can be removed from surfaces. The experimental setup and the optimization of the experimental parameters to study the adhesion of the diatom Navicula perminuta are described. As examples of how varying the physico-chemical surface properties affects the ability of diatoms to bind to surfaces, a range of hydrophilic and hydrophobic self-assembled monolayers was compared. While the number of cells that attached (adhered) was barely affected by the coatings, the critical shear stress required for their removal from the surface varied significantly.

Anti-Biofilm Effect of Biodegradable Coatings Based on Hemibastadin Derivative in Marine Environment

“…The adhesion strength of diatoms is an important parameter in antifouling development [ 42 ]. Hence, the effect of DBHB on this parameter was evaluated ( Figure 5 ).…”

The effects of diatom pore-size on the structures and extensibilities of single mucilage molecules

“…Frustules are also ornamented with pores, the majority of which are typically between 3 and 50 nm in diameter [49], though pores below 10 nm long and 2e5 nm wide have also been reported in the literature [48]. Extracellular polymeric substances (EPS), or, mucilage, is secreted by the diatom, expressing itself through the pores, and this enables the diatoms a degree of initial motility [2] and/or initial settlement upon diverse substrates.…”

Surface sensing and stress-signalling inUlvaand fouling diatoms – potential targets for antifouling: a review

“…By studying removal microscopically it was possible to observe whether cells lying on their valve detached more easily than those on their girdle or vice versa. Again, more Navicula cells lay on their valve (therefore the raphe is in contact with the surface) on a hydrophobic surface compared to a hydrophilic one (43% on the hydrophobic DDT compared to 30% on the hydrophilic EG 6 OH), however there was no significant effect of cell orientation in the critical shear stress required to remove cells (Alles & Rosenhahn 2015), which may be due to the high degree of variability in adhesion strength seen.…”

“…These hydrophobic, low modulus coatings do not prevent colonisation by fouling organisms but are designed as ''fouling-release'' coatings; that is, they ''release'' adhered organisms by the hydrodynamic forces generated when a ship moves through the water. Paradoxically, and in contrast to macroalgae such as Ulva, diatoms adhere more strongly to hydrophobic coatings and, conversely, adhere more weakly to hydrophilic surfaces such as glass (Holland et al 2004;Krishnan et al 2006;Stanley & Callow 2007;Alles & Rosenhahn 2015). Diatom genera requiring the highest pressure for removal from foulrelease coatings are Achnanthes, Amphora, Cocconeis, Navicula and Synedra which are all benthic diatoms, centric diatoms do settle but are easily removed in dynamic conditions (Hunsucker & Swain 2016).…”

“…When cells were cultured under a shear stress of 1.3 Pa on AWG the biofilm did not persist, yet on PDMSe a biofilm was still present at 2.4 Pa containing tightly bound clumps and a greater proportion of cells lying on their valve (raphe side), which is thought to be hydrodynamically favourable. Alles & Rosenhahn (2015) tested the use of a microfluidic detachment assay commonly used in cell biological tests. The benefits of such a system are that it requires only a small number of cells, along with a small test surface area, with which a high variation in well-defined laminar flow conditions can be tested.…”