Microfluidic Liquid Filters for Leukocyte Isolation

A microfluidic device for efficient and gentle leukocyte separation from whole blood is presented. The device is realized by taking advantage of the high specificity of lysing solutions, the collection efficiency of an Aqueous Two Phase System (ATPS), and the laminar flow of microfluidics. A narrow stream of dextran (DEX) containing whole blood is flowed next to a stream of polyethylene glycol (PEG) containing a lysing solution. The lysing solution diffuses across the interface and lyses the erythrocytes. The leukocytes are held in place by the surface tension of the two phase system while the remnants of the lysed erythrocytes, other blood materials and the lysing solution are allowed to diffuse away and then diverted to another channel. The main advantages of this method are the minimization of exposure of leukocytes to the toxic lysing solution and the removal of non-leukocyte components of blood. These steps are critical to allow the device to be used as a preparatory step for accurate quantification of leukocytes and sensitive detection of rare leukocytes.