Determining blood cell size using microfluidic hydrodynamics

Microfluidic flow cytometers currently analyze far fewer parameters than conventional flow cytometry or fluorescence activated cell sorting (FACS) in order to minimize cost and complexity. There is a need for microfluidic devices that analyze more and or new cell parameters with compact and minimal means. Here we show a new and explicitly microfluidic parameter, “hydrodynamic” cell size, and compare it to forward scatter in conventional flow cytometry. The hydrodynamic size of cells is determined by the degree of lateral displacement experienced while traveling through a 1.2-mm-wide non-clogging array of micro-fabricated obstacles. We show comparable size resolution between the microfluidic device and forward scatter in conventional flow cytometry and without the need to lyse red blood cells. We use the device to differentiate healthy lymphocytes from malignant lymphocytes by size alone and we use the device to detect increased numbers of activated lymphocytes in blood as a result of exposure to staphylococcal enterotoxin B (SEB), a potential bioterror agent. Together the results demonstrate a microfluidic device that performs some of the measurement and separation tasks of a flow cytometer but at a potentially lower cost and complexity.6 page(s

Microfluidic device for label-free measurement of platelet activation

In this work we demonstrate a new microfluidic method for the rapid assessment of platelet size and morphology in whole blood. The device continuously fractionates particles according to size by displacing them perpendicularly to the fluid flow direction in a micro-fabricated post array. Whole blood, labeled with the fluorescent, platelet specific, antibody PE-anti-CD41, was run through the device and the positions of fluorescent objects noted as they exited the array. From this, histograms of platelet size were created which show marked increases in size after exposure to thrombin or a temperature of 4 ◦C. We infer that the well known morphological changes that occur during activation are causing the observed increase in size.7 page(s