When scientists study biochemical reactions they spend a good deal of time changing concentrations of reagents. Because of that, it helps to have a tool that can create a chemical gradient of various solution strengths. National Institute of Standards and Technology scientists have now created a device called a “microfluidic palette,” that uses diffusion to produce chemical gradients in a volume the size of a pinhead. The goal is to be able to study how wounds heal, cancers metastasize, and other colloidal processes occur.
The unique aspect of this work is that chemical gradients are generated by diffusion, without convection, and can either be held constant over long periods, or modified dynamically. We characterized a representative device with a 1.5 mm circular chamber where diffusion takes place, and three access-ports for the delivery and removal of solutes. The gradient stabilizes in 15 min for small molecules and can be maintained constant indefinitely. We demonstrate overlapping gradients with different spatial location and a controlled rotation of a diffusive gradient around its centre [sic]. Finally, we demonstrate the applicability of this tool to study the chemotactic response of the bacteria P. aeruginosa to glucose.
NIST press release: ‘Microfluidic Palette’ May Paint Clearer Picture of Biological Processes…
Abstract in Lab on a Chip: The microfluidic palette: A diffusive gradient generator with spatio-temporal control
Image: (Top) The NIST microfluidic palette. The mixing area is the pin-sized chamber bordered by three holes in the center of the top layer. (Side) For each of the three dyes injected into the NIST microfluidic palette, an independent gradient forms that remains constant as long as flow into the system does not change. Overlapping the three gradients results in a blend of dye concentrations, but the combination of colors in any single location is distinctly different from all others location.