A low-voltage droplet charging circuit with simulative cell-sorting function for flow cytometer-cell sorter

Background: Flow cytometer cell sorters have become important tools in many biological laboratories. Commercial electrically-deflect cell sorters that deflect wanted cells in electrically charged droplets need high-voltage am plifiers which are expensive and difficult to obtain. Effort was made to bu ild an alternative droplet charging circuit with low-voltage amplifiers tha t are much easier to get and have more reasonable price. Methods: A low-voltage charging circuit was designed. Every time a cell was to be separated, a pair of complementary charging pulses were produced: on e was positive and the other was negative with equal amplitude. These were enlarged by two low-voltage charging amplifiers to drive two charging elect rodes respectively. Results: Due to the effect of addition, the voltage between the two electro des was double as high as the output of either amplifier. The result of tes t experiment proved that the cell sorter with low-voltage amplifiers, which was cheaper and easier to obtain, could separate cells as efficiently as t he instrument with high-voltage ones that were more expensive and more diff icult to make. In addition, a simulative cell-sorting function was provided , Conclusions: This low-voltage, easily-built and low-price charging circuit for flow cytometer cell sorter is a good alternative to the commonly used h igh-voltage one, especially to researcher who hopes to build his own person al instrument. Cytometry 39:306-309, 2000. (C) 2000 Wiley-Liss, Inc.