System for high-speed measurement and sorting of particles

#This invention relates to a system for investigating particles, and in particular to such a system wherein a plurality of detection signals from a particle or cell having pre-determined parameters can be characterized at very high signal processing rates.

#The concentration and biological activity of cells can be investigated by observing a spectrum of light modulated by the cells. In one method of spectral analysis of cells, substances can be investigated which show characteristic peaks, or maxima, of absorption when the light absorption is plotted as a function of light wavelength. In another method, fluorescence is used to investigate cells. In this method, cells are analyzed by their capacity to absorb light at a given wavelength and emit at a longer wavelength, a property which is known as fluorescence.

#Systems for sorting cells which automate the abovedescribed methods may be referred to as flow cytometer sorting systems. These systems are used in the medical research and diagnostic fields for the rapid analysis and processing of biological cells. Systems for sorting particles suspended in a liquid according to certain characteristics are discussed in U.S. Pat. No. 3,393,606, 4,063,284 and 4,487,320. Specifically, in these prior art systems optical measurements of characteristics of each particle of a group of particles are made while the particles are suspended in a liquid. In one such system, a flow cytometer cell sorter analyzes cells or particles in suspension which are stained with a fluorescent dye and are carried single file in a fast-moving liquid stream sequentially through a tightly focused laser beams whose wavelength is adjusted to excite the fluorescent dye. The fluorescence and/or light scatter produced during the laser beam crossing is collected by an optical system and projected through spectral filters onto photodetectors. These detectors convert the fluorescence and/or scattered light to electrical pulses whose amplitudes depend on the total light reaching the detectors. Particles having predetermined characteristics are recognized by their distinctive fluorescence and/or scattered light intensities. After measurements of the characteristics, each particle flows in a liquid jet stream until the particle reaches a point where the jet breaks into discrete droplets. At this point, an electric charge is induced on each droplet containing a particle to be sorted and the charged and uncharged droplets are then sorted electrostatically.

#FIG. 1 is a block diagram of an embodiment of the invention particle sorting system, working with a prior art flow cytometer/cell sorter system.

#FIG. 2 is a block diagram of a particle sorting system according to an embodiment of the invention.

#FIGS. 3A and 3B are logic diagrams of electrical circuitry for a particle sorting according to an embodiment of the invention.

#FIG. 1 illustrates a particle characterization system 12 in accordance with the present invention, used with a prior art flow cytometer cell sorter 10. System 12 receives input signals from photodetectors and preamplifiers 10a, processes these signals by analog and digital hardware and passes the processed data to a prior art data acquisition system 10b.

#FIGS. 2, 3A and 3B illustrate a preferred embodiment of a system constructed in accordance with the present invention. The system receives detection signals from particle detectors 10a, such as total signals, rare signals or other input signals. The incoming detected analog signals from the detectors are in the range of from about noise level to about 1.0 volt. For example, one of these signals might represent perpendicular light scatter (PLS), and the others represent one or more colors of fluorescence (RARE1, RARE2, RARE3). The total signal (TOTAL) represents a signal generated when any cell passes through the system. In this embodiment, input buffers, such as operational amplifiers 12a, are provided to receive the detection signals and to properly condition or amplify the incoming detection signals.

#The signals issuing from input buffers 12a go to respective comparators 12b each of Which determines if the received signal has crossed a threshold reference voltage. The threshold voltages come from respective threshold sources 12c whose voltage levels are setable by the user of the system.