**5. Conclusion**

220 Blood Cell – An Overview of Studies in Hematology

are retained at the start of the 10µm wide channels

**Figure 10.** (top) Schematic showing flow direction and channel structure for the Second generation device having varying channel gap widths (20, 15, 10, and 5m), cells separate based on size and deformability. Channel depths, constant over a single device are: 20 or 10m. (Bottom) Adult blood cells spiked with MDA231 cells. All cells flow freely through the device except for the MDA231 cells, which

A derivative of the same design was utilized to separate fetal cells from cord blood [91]. The device has four segments of successively narrower channels along the flow axis; these have 15, 10, 5, and 2.5 µm spacings. Each segment is 30 mm wide and 15 mm long and has 375 rows of channels of the same width. Therefore, the entire device is 30mm wide and 60mm long, giving rise to over 3.5 million channels. The channels are formed between pillars separated by gaps rather than a continuous structure. This design was favored to allow the cells to deform and resume their normal shape as they traverse the device; further, if the cell flow is locally slowed or if a channel becomes clogged, a cell is able to migrate around the affected area. Currently, a one-step centrifugation is required for sample preparation, and only the mononuclear layer is used in the device. This step not only separates most of the mature RBCs before sample loading, but it also enriches for fNRBCs since mononuclear cells and fNRBCs have similar densities. To identify fNRBCs, we stained the buffy coat with fluorescein isothiocyanate-labeled monoclonal antibody to HbF (green) and SYTO red. Thus, fNRBCs should fluoresce green and red. Double-stained samples were applied to the device. When the mononuclear layer was tested in the device, WBCs were retained consistently at the start of the 2.5 µm wide segment, while fNRBCs and mature RBCs migrated to the output reservoir. Cells were removed from the output reservoir, and the DNA was extracted with DNA purification kit and was tested for X and Y chromosomal sequence by PCR. We used cord blood from mothers who delivered male babies, so the X and Y chromosome could be used to demonstrate that the isolated cells In the last two decades, we witnessed many advances in microfluidic devices, and many of these devices are in advanced development stages or are commercially available. Microfluidic technology offers superior capability to precisely engineer and control the microenvironment to sort cells. Micro- and nano-fluidic technology will fulfill the sensitivity, specificity, and reproducibility requirements to bring cell sorting into clinical utility. The challenge remains to demonstrate that information acquired using microfluidic devices would change the way physicians diagnose, treat, and/or monitor diseases.
