Studies of Cells in a Flow

Sometimes, cellular analysis was performed with cells in a flow stream, which is also termed flow cytometry or FACS in the field of cell biology. For instance, human blood cell (WBC, RBC) rheology was studied in channels fabricated on the Si-Pyrex substrates. The channels were either uncoated or coated with albumin [825]. 

Mouse sperm cells were allowed to swim through a meander channel in a glass chip (Pyrex or soda lime glass) to fertilize an egg for in vitro fertilization (IVF) [876]. Later, sperm studies were carried out in PMMA chips [877]. 

In another report, a PDMS chip was constmcted with a main flow channel for sorting of motile human sperms ( 60 J,m in length). A side channel allowed motile sperms (moving at 20 um/s at 25°C) to divert from the main liquid flow and to be collected at the side channel. In contrast, non-motile sperm diffused slowly (D = 1.5 X 10-13 m2/s), i.e., they diffused for 10 pm in 690 s [878]. 

FIGURE 8.31 Photomicrographs showing yeast cell transport in a glass chip. White arrows show the direction of buffer flow. The scale bar is 40 im. (a) Cell loading vertically downwards, (b) Cell selection to the right [879], Reprinted with permission from the American Chemical Society. 

FIGURE 8.32 (a) A bright field epi-fluorescence image of two polymorphonuclear white cells (probably neutrophils), (b) The same cells shown in (a) imaged via the Hoechst stain. Note the differences in conformation between the two nuclei. The cell on the top is stuck at the entrance to a channel, and the cell at the bottom is being deformed into a channel. The channels are coated with polyurethane to reduce cell adhesion and to enhance white cell penetration [1175], Reprinted with permission from Springer Science and Business Media. 

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