Development of a Soft-Landing Type Multi Cell Sorting System

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Cell sorter is system that sort cells electrically by deflecting dropler which contains single cell. The uniform sized liquid droplets can be generated by a nozzle with a piezoelectric transducer. The cell is analyzed using a laser beam at the outlet of the nozzle, and the droplet containing the cell is charged and deflected by an electric field.In orderf to sort fragile cells such as protoplasts, a soft-landing type cell sorter using an upward nozzle was constructed, and its basic characteristics have been studied. Using a nozzle with 150 micrometer diameter, liquid droplets containing cells are sprayed upward with 7 to 10 m/s velocity, and are collected with reduced incident velocity of about 0.2 to 0.4 m/s by a wet plate electrode using an electrostatic force. Uniform sized liquid droplets can be formed wwhen frequency of the piezoelectric transducer, fp = 4 to 10 kHz at v = 7 m/s, and fp = 6 to 18 kHz at v = 10 m/s. Velocity and position of deflected charged droplets are monitored to stabilize the droplet trajectory by adjusting the flow rate of the liquid and the phase difference of the charging pulse to the piezo- electric transducer pulse. Protoplasts of carrot were used as the test sample. With conventional type cell sorter utilizing a downward nozzle, about 90 % of the protoplasts were destroyed at v = 10 m/s, and about 75 % at v = 7 m/s. This destruction rate can be lowered to 60 to 75 % at v = 10 m/s, and to 25 % at v = 7 m/s in the novel type cell sorter utilizing the upward nozzle. The protoplasts could be sorted with the droplet formation rate of 10 kHz at v = 7 m/s.