Prediction the Stress and Strain Field Acting on the Surface of Engineered Cells Seeded in the 3D Bioreactor

Abstract

Media perfusion bioreactor systems have been developed to culture tissue cells throughout 3D tissue engineered scaffold in vitro, which enhance the exchange of nutrients and wastes and deliver flow-mediated shear stresses to cells. Stress and strain field acting on the engineered cells is the outcome of several factors, such as characterization of the scaffold, medium flow rate and the interaction of hydrodynamic flow and the scaffold wall. We develop a nonlinear fluid and solid interaction (FSI) model of the flow of culture medium through a 3D scaffold of homogeneous geometry, with the aim of predicting the stress and strain field acting on the surface of engineered cells. We built three groups of models corresponding to three pore sizes: 50, 100 and 150μ m. Each group is made of four models corresponding to 61%, 65%,77% and 84% porosity. FORTRAN and C languages are used to solve this nonlinear FSI problem. A circular scaffold of 15.5mm diameter scaffold is perfused by a flow rate of 0.5ml/min. The simulation shows that the method without regards to the effect of solid deformation to flow field is not reasonable. The high shear stress areas decrease with the increase of pore size but the shear stress looks independent of the porosity on the wall. With the increase of pore size and porosity, the maximum and average values of equivalent normal strain and equivalent shear strain become lower. More larger of porosity and pore size, more forced distribution and smaller range for equivalent normal strain field and shear strain field. This modeling approach provides a quantitative assessment of the relationship between micro mechanics environment and tissue growth in vitro.