Early biofilm and streamer formation is mediated by wall shear stress and surface wettability: A multifactorial microfluidic study

Abstract

Biofilms are intricate communities of microorganisms encapsulated within a selfproduced matrix of extra-polymeric substances (EPS), creating complex threedimensional structures allowing for liquid and nutrient transport through them.These aggregations offer constituent microorganisms enhanced protection from environmental stimuli-like fluid flow-and are also associated with higher resistance to antimicrobial compounds, providing a persistent cause of concern in numerous sectors like the marine (biofouling and aquaculture), medical (infections and antimicrobial resistance), dentistry (plaque on teeth), food safety, as well as causing energy loss and corrosion. Recent studies have demonstrated that biofilms interact with microplastics, often influencing their pathway to higher trophic levels. Previous research has shown that initial bacterial attachment is affected by surface properties.Using a microfluidic flow cell, we have investigated the relationship between both wall shear stress (τ w ) and surface properties (surface wettability) upon biofilm formation of two species (Cobetia marina and Pseudomonas aeruginosa). We investigated biofilm development on low-density polyethylene (LDPE) membranes, Permanox ® slides, and glass slides, using nucleic acid staining and end-point confocal laser scanning microscopy. The results show that flow conditions affect biomass, maximum thickness, and surface area of biofilms, with higher τ w (5.6 Pa) resulting in thinner biofilms than lower τ w (0.2 Pa). In addition, we observed differences in biofilm development across the surfaces tested, with LDPE typically demonstrating more overall biofilm in comparison to Permanox ® and glass. Moreover, we demonstrate the formation of biofilm streamers under laminar flow conditions within straight micro-channels.

Ultrasonic irrigation flows in root canals: effects of ultrasound power and file insertion depth

“…This is due to the reported maximum values occurring in regions very close to the tip of the file which cannot be resolved with the current optical flow diagnostics due to reflections. Shear stresses in the magnitude range reported in our work have been shown to effectively remove biofilms of different bacterial species present in the dental root canal 32 , 33 . Although higher power settings seem to be beneficial from a fluid dynamics point of view, the impact of such settings on damage or potential breakage of the file due to fatigue or impact with the wall of the root canal, should be considered.…”

Development of Antifouling Strategies for Marine Applications

“…In turn, higher shear stress increased the cohesion of the biofilms allowing them to grow thicker and produce more biomass [ 2 ]. Using a microfluidic flow cell, the impact of shear stress on Cobetia marina and Pseudomonas aeruginosa biofilm formation was also evaluated [ 3 ]. The results indicated that hydrodynamics affect the biomass, maximum thickness, and surface area of biofilms, with the higher shear stress (5.6 Pa) promoting thinner biofilms than the lower shear stress (0.2 Pa).…”

“…Marine biofilm development is a complex and dynamic process comprising several organisms and interactions, which can be affected by different factors, from surface properties to environmental parameters and microbial content [ 1 , 2 , 3 , 4 ]. Indeed, biofilms are a common feature on all aquatic submerged surfaces, contributing to marine biofouling, which is responsible for several detrimental impacts on shipping efficiency, aquaculture industries, equipment corrosion, and maintenance, as well as disturbances in ecosystems [ 5 , 6 , 7 ].…”

Interaction between microorganisms and dental material surfaces: general concepts and research progress

“…In contrast, there is no difference between hydrophobic and hydrophilic surfaces in the subgingival environment. This difference is attributed to the flow renewal rate on the gingiva and a higher rate of bacterial shedding from the hydrophobic surfaces due to the action of flow shear force [ 37 ].…”

“…Among all the surface properties, surface roughness has become the main topic in the research on dental biofilms. The higher surface roughness generally promotes bacterial adhesion because the contact area increases [ 48 ], while the shear force decreases [ 37 ]. Therefore, a smooth surface can reduce biofilm formation [ 49 ].…”