A biomimetic method for extracting leukocytes from blood in microfluidic devices

The extraction of leukocytes from blood to be processed by micro-assay systems must be performed using methods which can be executed using minimal sample sizes and few preparatory steps. This demonstration proposes a biomimetic approach to performing this function using the adhesive rolling that is mediated by the interaction between a special class of proteins and ligands expressed by leukocytes but not red cells. The surfaces of microstructured flow channels made using standard microfabrication techniques can be coated with one or more of these adhesive proteins. These proteins facilitate the capture of leukocytes from blood samples sent through these channels. Captured cells are not immobilized but are restricted to slow rolling while blood passes rapidly through the channels. Eventually leukocytes become enriched and isolated as the rest of the blood is eluted through the channel. This study demonstrates the capture of HL-60 cells on E-selectin coated surfaces and quantities their transit through two prospective designs for microstructured flow channels. Results show that white cells can be enriched greatly over initial density and that flow geometry strongly influences the transit of the captured cells.