Apparatus and method for phase resolved fluorescence lifetimes of independent and varying amplitude pulses

• US 5,317,162 A
• Filed: 09/09/1992
• Issued: 05/31/1994
• Est. Priority Date: 05/23/1991
• Status: Expired due to Term

• Current Assignee: Becton, Dickinson & Co
• Original Assignee: Becton, Dickinson & Co
• Inventors: Hoffman, Robert A., Pinsky, Bertram G.
• Primary Examiner(s): Dzierzynski, Paul M.
• Assistant Examiner(s): HANIG, RICHARD E
• Application Number:
  US07/941,780
• Time in Patent Office: 629 Days
• Field of Search: 250/461.2, 250/458.1, 250/459.1, 356/318, 356/417, 436/172
• US Class Current: 250/461.2
• CPC Class Codes: G01N 15/04 Investigating sedimentation of particle suspensions
• CPC Class Codes: G01N 15/1459 the analysis being performed on a sample stream
• CPC Class Codes: G01N 2015/1477 Multiparameters
• CPC Class Codes: G01N 21/6408 with measurement of decay time, time resolved fluorescence
• CPC Class Codes: G01N 21/6428 Measuring fluorescence of fluorescent products of reactions or of fluorochrome labelled reactive substances, e.g. measuring quenching effects, using measuring "optrodes" in vivo A61B5/00; immunoassay G01N33/53

Abstract

A flow cytometer measures phase fluorescence lifetimes by the phase shift of a reference signal and an emission from a particle or cell in a flow chamber. An acoustic optic modulator modulates laser light with a sinusoidal wave of a predetermined frequency to excite particles or cells. Detectors respond to emissions of individual particles or cells in the form of an output signal pulse at the predetermined frequency. The output signal pulse is divided into equal pulses with each at the modulation frequency, the same amplitude and fidelity and amplitude. One part of the divided pulse is stripped of its envelope to pass the width thereof and out of band components are rejected. A variable amplifier passes a portion of the pulse above a present level. A delay line sets a central part of the signal at a predetermined point in time. A circuit limits the attenuated one part. A double balance mixer multiplies and the relates the limited signal with a reference signal to determine the phase shift. A method measures phase fluorescence lifetimes of cells or particles with fluorescent markers by passing individual cells or particles in a flow stream of a flow chamber in a flow cytometer.

Claims

1. An instrument to measure phase fluorescence lifetimes of signals representative of characteristics of subpopulations of particles by determining phase shift between a reference signal and emissions from the particles, the instrument comprising:

delivery means for moving particles through an interrogation window of the instrument;

a source of modulated light at a predetermined frequency, the source positioned to direct and focus the modulated light onto individual particles in the window;

detection means responsive to emissions from the individual particles illuminated by the source of modulated light, the detection means for generating an output signal;

means for filtering the output signal and producing a filtered signal thereby passing a frequency band centered at the modulation frequency;

an amplifier for setting the signal level above a preset level thereby producing a filtered, amplified signal;

a limiting circuit to limit the filtered, amplified signal thereby producing a limited signal;

a filter to remove from the limited signal, harmonics above the modulation frequency and an envelope below a preset frequency thereby producing a filtered limited signal, and

a mixer to mix the filtered limited signal with a reference signal thereby relating the reference signal and the filtered limited signal to determine the relative phase shift of the fluorescence emissions.

3. The flow cytometer of claim 1 further comprising an acoustic optic modulator to modulate the laser light from the source.

4. The flow cytometer of claim 3 further comprising a reference oscillator for driving the acoustic optic modulator to produce the reference signal used in the double balanced mixer.

5. The flow cytometer of claim 3 wherein the acoustic optic modulator has circuitry which produces an intensity modulated signal.

2. A flow cytometer operative to simultaneously measure phase fluorescence lifetimes of multiple particles by determining phase shift between a reference signal and emissions from the particles as the particles pass therethrough comprising:

delivery means for establishing a stream of particles of multiple populations to pass through a passage in a flow chamber of a flow cytometer;

a source of modulated light at a predetermined frequency, the source positioned to direct and focus the modulated light onto individual particles passing in the stream through the passage;

detection means responsive to emissions from the individual particles or cells illuminated by the source of modulated light, the detection means for generating an output signal pulse at the predetermined frequency;

means for dividing the output signal pulse into signal pulses, each divided signal pulse being modulated at the modulation frequency and having substantially the same amplitude and fidelity without any induced phase shift;

means for filtering the output signal pulse thereby passing a frequency band centered at the modulation frequency and with a band width approximately equal to the frequency band width of the envelope of the output signal pulse;

means responsive to a timing circuit for permitting the central part of the filtered signal to pass, the means responsive including a switch responsive to a low frequency portion of the other part of the equally divided signal;

a comparator for controlling the switch by comparing the portion of the low frequency signal and a reference;

a limiting circuit to receive and limit the second part of the divided signal;

a filter to receive the limited signal and remove harmonics above the modulation frequency and the envelope below a preset frequency, and

a double balanced mixer to multiply the limited signal with a reference signal and produce a multiple signal for relating the reference signal and the filtered limited signal and for determining the relative phase shift of the fluorescence emissions.

6. The flow cytometer of claim 2 wherein the comparator is connected to transmit only the central portion of the signal.

7. The flow cytometer of claim 6 wherein sorting means receive the cells or particles and segregate them on the basis of fluorescent lifetimes as determined by phase shift.

8. A method of measuring in a flow cytometer phase fluorescence lifetimes of particles having one or more fluorescent markers comprising:

passing individual particles in a flow stream through a flow chamber in a flow cytometer;

exciting each particle passing through the flow chamber with modulated light of a wavelength that stimulates at least one of the markers, the modulated light being at a predetermined modulation frequency;

detecting the stimulated fluorescent emissions from the flow chamber for each cell or particle;

producing an output signal representative of the detected stimulated emissions;

filtering and limiting the output signal to obtain a filtered limited signal;

mixing the filtered limited signal with a reference signal, and

relating the reference signal and the filtered limited signal to determine the relative phase shift of the fluorescence emissions.

9. The method of claim 8 with the additional step of obtaining the reference signal from a reference oscillator used to drive the modulator.

10. The method of claim 9 wherein the modulator generates sinusoidal modulation wave.

11. The method of claim 8 with the additional step of correlating the measured phase shift to a characteristic of the cells or particles in the stream passing through the flow chamber of the flow cytometer.

12. The method of claim 8 with the further step of sorting cells or particles on the basis of fluorescent lifetimes as determined by phase shift.

13. An instrument operative in a dynamic system to simultaneously measure phase fluorescence lifetimes of pulsing signals representative of characteristics of subpopulations of cells or particles by determining phase shift between a reference signal and emissions from particles or cells comprising:

delivery means for moving particles or cells of multiple populations to pass through an interrogation window of the instrument;

a source of intensity modulated laser light at a predetermined frequency, the source positioned to direct and focus the modulated laser light onto individual particles or cells in the window;

detection means responsive to emissions from the individual particles or cells illuminated by the source of intensity modulated laser light, the detection means for generating an output signal pulse at the predetermined frequency;

means for dividing the output signal pulse into equal signals, each equal signal being modulated at the modulation frequency and having the same amplitude and fidelity without any induced phase shift;

means for filtering one part of the equally divided signal thereby passing a frequency band centered at the modulation frequency and with a band width approximately equal to the frequency band width of the envelope of the one part signal pulse;

a variable amplifier for setting the signal level above a preset level;

a limiting circuit to limit the filtered amplified one part of the equally divided signal;

a filter to remove from the limited signal harmonics above the modulation frequency and an envelope below a preset frequency;

means to determine the amplitude and/or width of the other part of the equally divided signal; and

a double balance mixer to multiply the filtered limited signal with a reference signal and produce a multiple signal thereby relating the reference signal and the filtered limited signal to determine the relative phase shift of the fluorescence emissions.

14. A device for measuring phase fluorescence of a particle, the device comprising:

means for producing a light beam;

modulating means for modulating the light beam;

means for passing the particle through the light beam such that the particle emits fluorescence;

detection means for detecting the fluorescence emitted by the particle and for producing a signal in response to the fluorescence emitted by the particle;

means for producing a reference signal;

means for mixing the signal in response to the fluorescence and the reference signal to determine the difference in phase between the signal in response to the fluorescence and the reference signal.

15. The device of claim 14 wherein the modulating means generates a modulating wave at a modulating frequency.

16. The device of claim 15 wherein the modulating wave provides the reference signal.

17. The device of claim 14 wherein the means for determining the difference in phase comprises means for mixing the signal in response to the fluorescence emitted by the particle and the reference signal.

18. The device of claim 14 further comprising means for processing the signal in response to the fluorescence emitted by the particle, the means for processing comprising a band pass filter.

19. The device of claim 18 wherein the means for processing further comprises an attenuator.

20. The device of claim 15 wherein the modulating means comprises a frequency synthesizer and an opto-acoustic modulator driven by the frequency synthesizer.

21. The device of claim 17 wherein the means for determining the difference in phase comprises a double balanced mixer.