Estimating Fluid Local Velocity within a Novel 3D Collagen Matrix Perfusion System

Traditional cell culture, performed on flat surfaces under static conditions, does not accurately represent physiologic conditions. As an alternative, groups have applied interstitial fluid flow (0.12.0 μm/s) through a 3D cell-embedded extracellular matrix (ECM). Cells sense the flow via mechanotransduction, a process by which cells sense mechanical forces and resultantly respond with biochemical signaling. Previous work demonstrates enhanced cell morphogenesis under interstitial flow conditions. However, fluid flow is poorly described within these systems, stressing the need for a well-characterized 3D interstitial flow system. Understanding fluid mechanics within a perfusion system will help elucidate cellular response to flowinduced mechanical forces. The objective of this study was to quantify the fluid flow velocity through a controlled ECM. The changes in the collagen concentration are directly related to the fibril density of the collagen (stiffness). A fluorescent Rhodamine solution was pumped at a constant flow rate through a collagen matrixcontaining chamber. The resulting flow front was visualized at the center of the chamber using a fluorescent microscope. A Matlab program was developed to track the light intensity between time points to provide measures of flow velocity.