MICROFLUIDICS

The recruitment of leukocytes to the wall of blood vessels occurs under the fluid shear stress of blood flow. In conjunction with the Jeon lab at UC Irvine, we developed a microfluidic flow chamber capable of interfacing with a living monolayer of cells unlike most microfluidic devices currently in use. These vascular mimetic microfluidic chambers (VMMC) were originally fabricated at a width of 200 microns and a height of 100 microns by a photolithographic process. This pattern, which mimics the geometry of small blood vessels, was etched into a layer of photoresist on a silicon wafer, and replicated by overlaying Polydimethyl Sulfoxide (PDMS, a thermosetting plastic).

The above image is a 3-D representation of a microfluidic flow chamber

The VMMCs consume much less sample volume than conventional parallel plate flow chambers which have been extensively used to probe leukocyte recruitment under shear stress. Because multiple sets of flow channels are etched into each device, multiple experiments can be conducted on a single monolayer grown using conventional culture techniques. Furthermore, by introducing leukocytes into the chamber from a reservoir built directly into the device, we have reduced dead volume to less than 2 microliters. The combination of these features has allowed us to conduct an extensive study of relatively scarce blood monocytes adhering to inflamed arterial endothelial cells (see Atherosclerosis). Our microfluidic technique is also used heavily in conjunction with real time fluorescent imaging to study the dynamics of neutrophil signaling during recruitment to endothelium.

We continue to work on improving the design of our microfluidic devices. We have developed microfluidic chambers that expose endothelium to a gradient of shear stress in order to investigate the affect of fluidic forces on monocyte recruitment to atherosclerotic plaques.