A Schematic of the fabrication and assembly of a BLOCC, where: 1 - individual acrylic and silicone components were laser cut with predetermined patterns needed to support the prolonged culture of cells in an oxygen gradient. 2 - Components F and G were compressed together by hand, and the cell-containing regions loaded with a cell-free hydrogel. 3 - After the cell-free hydrogel has gelated, a cell-laden hydrogel was added. 4 - Components B–G were stacked, compressed together by hand, and 1 mL of culture medium added to the reservoir. 5 - Component A was added to the top, and the entire device was enclosed with 10 screw assemblies. Oxygen gradients were formed by flowing oxygenated and deoxygenated gas mixtures along the cell-containing regions. B Photographs of each component of the BLOCC as well as an assembled device. Scale bar = 15 mm.

Oxygen Tension

Oxygen is a transcriptional regulator responsible for tissue homeostasis and maintenance. Studies relating cellular phenotype with oxygen tension often use hypoxia chambers, which expose cells to a single, static oxygen tension. Despite their ease of use, these chambers are unable to replicate the oxygen gradients found in healthy and diseased tissues.

Microfabricated devices capable of imposing an oxygen gradient across tissue-like structures are a promising tool for these studies, as they can provide a high density of information in a single experimental setup.

Researchers in the Lockett Group, published in Analytical Methods, describe the fabrication and characterization of a modular device, which leverages the gas-permeability of silicone to impose gradients of oxygen across cell-containing regions, assembled by layering sheets of laser cut acrylic and silicone rubber. The silicone also acts as a barrier, separating the flowing gases from the cell culture medium, preventing evaporation or bubble formation in experiments that require prolonged periods of incubation. The acrylic components provide a rigid framework to provide a sterile culture environment.

The incorporation of an oxygen-sensing film and an eGFP-based reporter assay allowed the scientists to map the oxygen gradient and cellular responses simultaneously and in real-time. These data suggest that cellular responses to hypoxia are proportional to oxygen stress. The stratification of these datasets provided further insight into this relationship, narrowing down the oxygen ranges for future studies. BLOCCs will support these investigations, mapping temporal and spatial responses of HIF stabilization in defined oxygen gradients.