A microfabricated platform for establishing oxygen gradients in 3-D constructs

Abstract

Oxygen gradients are increasingly implicated in a number of biological processes, including stem cell differentiation and cancer metastasis. Unfortunately, the current in vitro tools designed to mimic conditions found in vivo lack application flexibility, simplicity in operation, and precise spatial control that most researchers require for widespread dissemination. The novel microfluidic-based device presented here addresses all the above concerns, offering a simple platform for enhanced control over the oxygen microenvironment exposed to three-dimensional cell-seeded constructs. The device utilizes an oxygen diffusion membrane approach to establish a gradient across a construct sandwiched between two continually perfused microfluidic networks. The device is capable of forming steady-state gradients at both the conditions tested - 0% to 5% O2 and 0% to 21% O2 - but a wide variety of profiles within the construct are possible. Cell viability with two model cell lines was also tested, with no adverse effects relative to the control.

A paper-based invasion assay: Assessing chemotaxis of cancer cells in gradients of oxygen

“…Furthermore, hypoxia chambers do not generating gradients of oxygen to study chemotaxis. A well-defined gradient of oxygen can be formed in a microfluidic device containing cells, but these devices are predominantly used to study cellular viability, proliferation, and differentiation (7,8,(24)(25)(26)(27)(28). To our knowledge, in vitro studies of chemotaxis in the presence of a gradient of oxygen-particularly one generated by cellular metabolismhave yet to be performed for mammalian cells.…”

“…This lack of experimental data is due largely to the difficulty in controlling and measuring gradients of oxygen in living tissue, and to the difficulty associated with analyzing the migratory response of cells in conventional model systems (both in vivo and in vitro) (7)(8)(9)(10)(11). These mathematical models predict that asymmetric gradients of oxygen and other small molecules such as glucose can cause differential rates of proliferation of cells in a tumor, and these gradients ultimately contribute to the formation of primary tumors with irregular shapes (5).…”

“…The concentration gradient of small molecules can be controlled temporally and spatially (at length scales of tens of microns, which is the scale of a single cell) in a microfluidic device (7,8,(24)(25)(26)(27)(28). These devices are often fabricated in optically transparent materials and make it possible to visualize cell migration in real time (19).…”

“…While a variety of microfluidic devices have been developed to control precise gradients of concentration of oxygen (7,8,(24)(25)(26)(27)(28)(29), only recently has a device been used to investigate the migration of cells in such gradients (29). Tung et al demonstrated that oxygen acts as a chemorepellant for A549 cells and these cells migrate toward lower concentrations of oxygen in the presence and absence of an overlapping concentration gradient of stromal cell-derived factor 1 (SDF-1); the gradient of SDF-1 was perpendicular to the concentration gradient of oxygen (29).…”

Soluble compound screening using microfluidic gradients for regenerative medicine research

“…It has the advantage of being gas-permeable, and therefore cells grown in PDMS based systems can be cultured using conventional laboratory incubators. [244][245][246] Furthermore, PDMS is relatively inexpensive and its fabrication is straightforward. 247 The use of PDMS is, however, also associated with important drawbacks, such as limited fluidic control due to the porous nature of the material, and unpredictable and unstable surface chemistry.…”