Changes in stiffness of yeast cells during cell cycle by passability through micromachined channel arrays

Possibility of cell sorting by cellular deformability was examined using yeast cells (Saccharomyces cerevisiae) and previously described microchannel arrays (width 6 mu m, length 20 mu m or width 8 mu m, length 40 mu m, depth 4.5 mu m, and number 2600 or 4704 in parallel). Cells harvested at every an hour during incubation (YPD broth, 32 degrees C, after preincubation for 24 hours) were washed and suspended in sorbitol (0.6 M) solution (pH 7.5) at a concentration of O.D. 0.3 (560 nm). An aliquot of each suspension was caused to now through the microchannel arrays by applying 20 cmH(2)O suction. Cells at two hours of incubation could not enter into the microchannels, while cells at 4-5 hours of incubation could enter into the microchannels despite their larger size due to budding than the preceding ones and some few cells were observed to pass through 8 mu m width microchannels. The number of cells that could enter into the microchannels decreased at 7-8 hours and reincreased at 9-10 hours, but the synchronism in this second cycle appeared to decrease. Protoplasts prepared by treatment with zymolyase from cells at 4-5 hours of incubation showed no appreciable resistance to the microchannel passage.