Characterization of the phagocytic ability of white blood cells separated using a single curvature spiral microfluidic device

The present work describes a microfluidic device developed for separating white blood cells (WBCs) for the Nitroblue Tetrazolium (NBT) bioassay, which quantifies the phagocytic ability of cells. The NBT test requires a small number of phagocytic cells but is highly susceptible to the presence of red blood cells (RBCs). Our inertial microfluidic device can deliver a WBC sample by removing 99.99% of RBCs and subsequently reducing the ratio of RBC to WBC from 848:1 to 2:3. The microdevice operates on a relatively higher hematocrit concentration (1% Hct) of blood. Compared to conventional WBC separation methods, the microdevice’s passive, label-free nature preserves the cell properties of the original sample. A single-turn spiral microfluidic device with a rectangular cross-section is simple to fabricate, cost-effective, and easy to operate. The reported microfluidic device requires only a single drop of whole blood (⁓20 µl) obtained via the finger prick method for efficient phagocytic analysis. Also, the microdevice reported in this study achieves WBC separation in under 10 min, omitting the need for RBC lysis, density gradient centrifugation, or expensive antibodies.