Investigating the Effects of Fluid Shear Forces on Cellular Responses to Profiled Surfaces in-Vitro: A Computational and Experimental Investigation

Abstract

The flow conditions in a parallel plate "bioreactor" have been modeled using Computational Fluid Dynamics (CFD) and characterized experimentally using a computer controlled flow regulation apparatus and associated flow visualization techniques. The conditions required to induce flow characteristics appropriate for standard in-vitro cell processes on flat substrates have been identified from a consideration of data from previous studies. The effects of changing the surface topography of the substrate on which the cells are grown has been investigated by forming specific micrometer scale features via hot embossing on polymeric plates. The effect that various features have on the flow that occurs at the boundary layer adjacent to the surface in the parallel plate chamber has been determined. The results for studies undertaken in a parallel plate chamber operating under computer control are presented here. Flow characteristics have been determined using feedback from the sensors within the system and validated by direct flow visualization using fluorescent beads and modeled using a CFD routine. The system exhibits well developed laminar flow and is capable of delivering surface shear stresses up to 2.4 Pa on a planar surface. As such, it is suitable for evaluating in-vitro cell processes. The effects that the features produced by hot embossing of a Poly Methyl Methacrylate (PMMA) surface have been tested in the flow chamber and their influence on shear stress observed.

Flow dynamics in bioreactors containing tissue engineering scaffolds

“…To better understand the effect of fluid flow during tissue regeneration, a number of studies using computational fluid dynamics (CFD) have been performed (Brown and Meenan, 2007;Cioffi et al, 2006;Hutmacher and Singh, 2008;Porter et al, 2005;Sander and Nauman, 2003;Williams et al, 2002). The majority of these studies assess the flow patterns and shear stresses either within the bioreactor or around the porous construct (Bilgen and Barabino, 2007;Williams et al, 2002).…”

Modeling of shear stress experienced by endothelial cells cultured on microstructured polymer substrates in a parallel plate flow chamber

“…Confluent cell monolayers were subjected to 1 h of LSS in a parallel plate flow chamber. The flow chamber was designed and fabricated in‐house, the details of which have been presented elsewhere (Brown and Meenan, 2007). Shear stress tests were conducted at 5.5 mL/min, based on a nominal shear stress of 1 Pa, and 4 mL/min, based on a nominal shear stress of 0.7 Pa. At least two samples of each surface type were exposed to each flow rate.…”

Bi-Modular Flow Characterization in Tissue Engineering Scaffolds Using Computational Fluid Dynamics and Particle Imaging Velocimetry

“…[15][16][17][18] The quantification of the nutrient supply and of the mechanical stimuli, both directly related to the medium fluid flow, is a key factor for the generation of bone tissue. To achieve this goal a number of studies have been performed using computational fluid dynamics (CFD) [19][20][21][22][23][24][25][26] or flow measurements techniques. 21,27 Different porous, macroscale, and microscale CFD models have been implemented to determine the shear stress distribution and the oxygen distribution inside TE constructs.…”