Comparison of Velocity Profiles for Different Flow Chamber Designs Used in Studies of Microbial Adhesion to Surfaces

Abstract

Flow chambers are commonly used to study microbial adhesion to surfaces under environmentally relevant hydrodynamic conditions. The parallel plate flow chamber (PPFC) is the most common design, and mass transport occurs through slow convective diffusion. In this study, we analyzed four different PPFCs to determine whether the expected hydrodynamic conditions, which control both mass transport and detachment forces, are actually achieved. Furthermore, the different PPFCs were critically evaluated based on the size of the area where the velocity profile was established and constant with a range of flow rates, indicating that valid observations could be made. Velocity profiles in the different chambers were calculated by using a numerical simulation model based on the finite element method and were found to coincide with the profiles measured by particle image velocimetry. Environmentally relevant shear rates between 0 and 10,000 s ؊1 could be measured over a sizeable proportion of the substratum surface for only two of the four PPFCs. Two models appeared to be flawed in the design of their inlets and outlets and allowed development of a stable velocity profile only for shear rates up to 0.5 and 500 s ؊1 . For these PPFCs the inlet and outlet were curved, and the modeled shear rates deviated from the calculated shear rates by up to 75%. We concluded that PPFCs used for studies of microbial adhesion to surfaces should be designed so that their inlets and outlets are in line with the flow channel. Alternatively, the channel length should be increased to allow a greater length for the establishment of the desired hydrodynamic conditions.

The effects of surface properties on Escherichia coli adhesion are modulated by shear stress

“…Under a higher flow velocity, the number of cells arriving to the surface is higher and cellular appendages may contribute to a higher productivity in adhesion [42,44]. However, since a stronger shear stress is promoted under this hydrodynamic condition and a lower contact time between the cells and the surface is expected, the gliding motion along the surface, which can happen during reversible adhesion, may be hampered [42,45]. Thus, the adhesion step must be quicker in order to overcome this effect.…”

“…This theory considers that bacterial adhesion will increase with increasing flow velocities, due to the increased cell transport to the surface. However, the model does not account for the fact that a higher flow rate promotes higher shear stresses that may prevent cellular attachment [42]. This hindrance may be overcome by the bacterial appendages used in adhesion [43].…”

Cell cultures as models of cardiac mechanoelectric feedback

“…Uniform and steady shear stress across a cultured cell monolayer can be generated experimentally in a parallel plate flow chamber (Bakker et al, 2003). To generate laminar flow on top of the cell monolayer, the height of the chamber should be much less than the overall chamber width, and the entrance and exit width should be much smaller than the chamber length.…”

Parallel-plate Flow Chamber and Continuous Flow Circuit to Evaluate Endothelial Progenitor Cells under Laminar Flow Shear Stress

“…Of note, other flow chambers that have been described to be autoclavable appear impractical because they require special microscopic lenses 22,23 . The GlycoTech system utilizes silicon rubber gaskets interposed between top and bottom plates, which will change in thickness with repeated use and therefore change chamber height over time (the manufacturer recommends purchasing new ones after every ten uses).…”