Development of a soft-landing type multi-cell sorting system using an upward nozzle

In order to sort fragile cells such as plant protoplasts, a soft-landing-type cell sorter has been developed, and its basic characteristics have been studied. Using a nozzle with a 150 mu m diameter, liquid drops containing a single carrot protoplast are sprayed upward with 7 m/s velocity and collected with reduced incident velocity of about 0.2 to 0.4 m/s by a plate-plate electrode using an electrostatic force. More than 80% of the protoplasts could be recovered in this apparatus, whereas the recovery rate was less than 20% when the incident velocity was not reduced. It was experimentally confirmed that the fragile protoplasts could be sorted in this system with spray velocity of 7 to 10 m/s and droplet formation frequency of 8 to 12 kHz.<>