U.S. patent application number 11/190300 was filed with the patent office on 2007-02-01 for method and apparatus for syringe-based sample introduction within a flow cytometer.
This patent application is currently assigned to DakoCytomation Denmark A/S. Invention is credited to Angela L. Vandergaw.
Application Number | 20070025879 11/190300 |
Document ID | / |
Family ID | 37694493 |
Filed Date | 2007-02-01 |
United States Patent
Application |
20070025879 |
Kind Code |
A1 |
Vandergaw; Angela L. |
February 1, 2007 |
Method and apparatus for syringe-based sample introduction within a
flow cytometer
Abstract
An apparatus for introducing a specimen into a flow cytometer
comprises: a syringe having a hollow barrel containing the
specimen, a plunger partially within the barrel and a needle that
extends into a volume of a nozzle of the flow cytometer; a one-way
port in the nozzle forming a seal against the needle; a mounting
platform coupled to both the syringe and to the flow cytometer; and
a syringe pump coupled to the plunger, the syringe pump comprising
a motor, a drive mechanism coupled to the motor; and a clamping
mechanism coupled to the drive mechanism, wherein the motor
operates the drive mechanism so as to cause the clamping mechanism
to depress the plunger into the barrel.
Inventors: |
Vandergaw; Angela L.; (Fort
Collins, CO) |
Correspondence
Address: |
Thomas F. Cooney, Patent Admin.;DakoCytomation Colorado, Inc.
4850 Innovation Drive
Fort Collins
CO
80525
US
|
Assignee: |
DakoCytomation Denmark A/S
Glostrup
DK
DK-2600
|
Family ID: |
37694493 |
Appl. No.: |
11/190300 |
Filed: |
July 27, 2005 |
Current U.S.
Class: |
422/73 ;
422/400 |
Current CPC
Class: |
G01N 35/1095 20130101;
G01N 2015/1409 20130101 |
Class at
Publication: |
422/073 ;
422/100 |
International
Class: |
G01N 33/00 20060101
G01N033/00 |
Claims
1. An apparatus for introducing a specimen into a flow cytometer,
the apparatus comprising: a syringe having a hollow barrel
containing the specimen, a plunger partially within the barrel and
a needle that extends into a volume of a nozzle of the flow
cytometer; a one-way port in the nozzle forming a seal against the
needle; a mounting platform coupled to both the syringe and to the
flow cytometer; and a syringe pump coupled to the plunger and
comprising: a motor, a drive mechanism coupled to the motor; and a
clamping mechanism coupled to the drive mechanism and to an element
of the group consisting of the syringe barrel, the mounting
platform and the flow cytometer, wherein the motor operates the
drive mechanism so as to cause the clamping mechanism to depress
the plunger into the barrel.
2. The apparatus of claim 1, further comprising: a pressure sensor
coupled to a sheath fluid line of the flow cytometer; and a
controller module electronically coupled to the pressure sensor and
to the motor, wherein the pressure sensor transmits a signal based
upon sheath fluid pressure in the sheath fluid line to the
controller module.
3. The apparatus of claim 2, wherein the controller module operates
the motor in response to the signal to maintain a constant pressure
differential between the sheath fluid pressure and a pressure of
the specimen.
4. The apparatus of claim 2, wherein the controller module varies
the sheath fluid pressure in response to the signal to maintain a
constant pressure differential between the sheath fluid pressure
and a pressure of the specimen.
5. The apparatus of claim 1, wherein the drive mechanism comprises
a lead screw and the clamping mechanism comprises a plate engaged
to the plunger and another plate engaged to an element of the group
consisting of the syringe barrel, the mounting platform and the
flow cytometer.
6. An apparatus for introducing a specimen into a flow cytometer,
the apparatus comprising: a syringe having a hollow barrel
containing the specimen, a plunger partially within the barrel and
a needle that extends into a volume of a nozzle of the flow
cytometer; a hollow receptacle in the nozzle receiving and forming
a seal against the needle; a mounting platform coupled to both the
syringe and to the flow cytometer; and a syringe pump coupled to
the plunger and comprising: a motor, a drive mechanism coupled to
the motor; and a clamping mechanism coupled to the drive mechanism
and to an element of the group consisting of the barrel, the
mounting platform and the flow cytometer, wherein the motor
operates the drive mechanism so as to cause the clamping mechanism
to depress the plunger into the barrel.
7. The apparatus of claim 6, further comprising: a pressure sensor
coupled to a sheath fluid line of the flow cytometer; and a
controller module electronically coupled to the pressure sensor and
to the motor, wherein the pressure sensor transmits a signal based
upon sheath fluid pressure in the sheath fluid line to the
controller module.
8. The apparatus of claim 7, wherein the controller module operates
the motor in response to the signal to maintain a constant pressure
differential between the sheath fluid pressure and a pressure of
the specimen.
9. The apparatus of claim 7, wherein the controller module varies
the sheath fluid pressure in response to the signal to maintain a
constant pressure differential between the sheath fluid pressure
and a pressure of the specimen.
10. The apparatus of claim 6, wherein the drive mechanism comprises
a lead screw and the clamping mechanism comprises a plate engaged
to the plunger and another plate engaged to an element of the group
consisting of the syringe barrel, the mounting platform and the
flow cytometer.
11. An apparatus according to claim 1, wherein the volume of
specimen introduced into the nozzle is determined or calculated
from the distance by which the plunger is depressed into the
barrel.
12. An apparatus according to claim 1, wherein the rate of
introduction of specimen into the nozzle is determined or
calculated from the rate by which the plunger is depressed into the
barrel.
13. An apparatus according to claim 12, wherein a rate of particle
introduction into the nozzle is determined or calculated from a
particle density of the specimen.
14. A method for introducing a specimen into a flow cytometer
comprises the steps of: providing a syringe having a hollow barrel
containing the specimen, a plunger partially within the barrel and
a needle extending into a volume of a nozzle of the flow cytometer;
providing a one-way port in the nozzle container forming a seal
against the needle; providing a mounting platform coupled to both
the syringe and to the flow cytometer; providing a syringe pump
coupled to the plunger and comprising: a motor; a drive mechanism
coupled to the motor; and a clamping mechanism coupled to the drive
mechanism and to an element of the group consisting of the barrel,
the mounting platform and the flow cytometer; and operating the
motor so as to operate the drive mechanism so as to cause the
clamping mechanism to depress the plunger into the barrel.
15. The method of claim 14, further comprising the steps of:
providing a pressure sensor coupled to a sheath fluid line of the
flow cytometer; providing a controller module electronically
coupled to the pressure sensor and to the motor; determining
variations in sheath fluid pressure with the pressure sensor; and
transmiting a signal based upon sheath fluid pressure to the
controller module.
16. The method of claim 15, further comprising the step of using
the controller module to operate the motor in response to the
signal to maintain a constant pressure differential between the
sheath fluid pressure and a pressure of the specimen.
17. The method of claim 15, further comprising the step of using
the controller module to control the sheath fluid pressure in
response to the signal to maintain a constant pressure differential
between the sheath fluid pressure and a pressure of the
specimen.
18. The method of claim 14, further comprising the step of
determining or calculating the volume of specimen introduced into
the nozzle from the distance by which the plunger is depressed into
the barrel.
19. The method of claim 14, further comprising the step of
determining or calculating the rate of introduction of specimen
into the nozzle from the rate by which the plunger is depressed
into the barrel.
20. The method of claim 19, wherein a rate of particle introduction
into the nozzle is determined or calculated from a particle density
of the specimen.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to flow cytometers and flow
cytometry for analyzing and sorting individual particles. More
particularly, the present invention relates to sample introduction
apparatus for a flow cytometer, the sample introduction apparatus
including a syringe directly coupled to the flow cytometer.
BACKGROUND OF THE INVENTION
[0002] Flow cytometers have been in clinical and research use for
many years. Basically, the systems act to position small amounts of
a substance within a sheath fluid. This sheath fluid may either
form droplets or may exist in a stream for optical analysis.
Through hydrodynamic focusing and laminar flow, the sample is
forced into a single file of individual cells and the like and is
surrounded by a sheath fluid. In many applications, the sheath
fluid together with its entrained substance exits a nozzle in a jet
and either free falls or is channeled in an optically transparent
pathway for analysis. Analysis and possible sorting of the
particles as they traverse the optically transparent pathway have
been employed in the determination of the variety of
characteristics of individual particles. This analysis is most
useful in analyzing or determining characteristics of biological
cells for the collection of information which would be useful in
areas of research, hematology, immunology and the like. The
researcher, for example, may be interested in determining specific
characteristics of the individual cells so that such cells may be
classified, identified, quantified and perhaps sorted for further
investigations or analysis.
[0003] FIG. 1 is a schematic illustration of the operation of a
typical flow cytometer. The flow cytometer 1 shown in FIG. 1
includes a nozzle system 42 that acts to introduce a flow of a
substance within a sheath fluid. To accomplish this, the nozzle
system 42 includes nozzle container 2 which establishes nozzle
volume 3. The nozzle volume 3 has sheath fluid port 24 within it so
that a sheath fluid may be introduced to it from a sheath reservoir
5 via a sheath fluid line 4. In addition, a substance introduction
port 9 is included so that a substance may be introduced from
substance reservoir 8 into the sheath fluid. The sheath fluid and
its entrained substance are then hydrodynamically focused so that
single cells and the like may be emitted from a nozzle tip 6 into
free fall area 7 or an analysis area. By allowing the sheath fluid
to exit from the nozzle volume 3, a jet 12 is created. This jet
occurs within free fall area 7 or an analysis area where it may be
analyzed or further processed.
[0004] In a sorting flow cytometer, as shown in FIG. 1, a vibration
in jet 12 may be initiated by an oscillator 10. Oscillator 10 acts
to initiate variations within jet 12 so that its oscillations may
act to form droplets 13 from the sheath fluid at droplet separation
point 69 as those skilled in the art readily understand. Each of
the droplets 13 may be differentially analyzed in an analysis area
to assess whether they contain a particular item or substance such
as a cell or a cell fragment. For a sorting application, sorting
equipment may be included to differentially charge each droplet
which contains a cell or particle of interest and thus deflect them
electrostatically. Typically, the sorting equipment comprises an
electrical charging apparatus 16 including an electrode penetrating
volume 3 and one or more electrostatic deflection plates 26. If
oscillator 10 is not present or not operational, then the flow
cytometer produces a continuous jet flow. In this case, the jet may
simply be analyzed in an analysis area and collected in some
receptacle for eventual disposal.
[0005] Importantly, most flow cytometers act to sense a specific
property of the substance being analyzed. As shown in FIG. 1, this
occurs through the use of some type of substance property sensor
62. Substance property sensor 62 may be positioned so that it
senses light emissions occurring from the substance within jet 12.
The signals then sensed may be utilized by analysis equipment 15 in
a variety of different ways depending upon the particular substance
or application involved. The light emissions from the substance may
occur at one wavelength or frequency or may occur throughout a
substance wavelength band. In order to analyze the substance, it is
frequently common to cause the substance to fluoresce and then
analyze its emissions. This may be created naturally or by
stimulating the substance after it exits from nozzle container 2
through some type of substance stimulation source 65. Substance
stimulation source 65 should be directed towards the substance
possibly at location of jet 12. As those skilled in the art would
readily understand, substance stimulation source 65 may emit
electromagnetic radiation and thus serve as an electromagnetic
source such as a laser which causes the substance to fluoresce.
This fluorescence may occur within a fluorescence emission
band.
[0006] A known problem in the use of conventional flow cytometers
arises from cross contamination between successive sample
substances and contamination from non-sterile instrument parts. For
example, FIG. 2 illustrates a portion of the fluidics system of a
conventional flow cytometer. As illustrated in FIG. 2, the nozzle
container 2 receives a sheath fluid received from sheath fluid
lines 4 via sheath fluid ports 24 and receives a substance to be
analyzed from substance introduction port 9 via a substance
introduction port 9. Sheath fluid exits the nozzle container 2
through the nozzle tip 6. The reservoir 8 of the substance to be
analyzed is contained within a pressurized container 20. Gas
pressure is introduced into pressurized container 20 from gas line
18 and the pressure is controlled or shut off by gas pressure valve
19. The pressure in the container 20 forces the substance of the
reservoir 8 to be forced into the substance introduction port 9 and
the flow of the substance within the substance introduction port 9
is controlled or shut off by valve 17. Alternatively, instead of
using a pressurized vessel 20, the sample substance may be caused
to flow within the substance introduction port by means of a
mechanical pump, such as a syringe pump.
[0007] Within the conventional flow cytometer diagrammatically
illustrated in FIG. 2, to remove the reservoir comprising a first
substance so that a second substance may be analyzed in its place,
the valve 17 and the valve 19 are shut off so as to isolate the
container 20. The container 20 is then replaced with another
container having a reservoir of the second substance. Also, the
substance introduction port 9 and the valve 17 must be either
replaced or else thoroughly cleaned and sterilized. The non
replaceable elements of the nozzle container 2 must be thoroughly
flushed and sterilized. When replacing the various parts, such as
the container 20 or the sample introduction port, care must also be
exercised to ensure that the replacement parts are clean and
sterile.
[0008] The above-described precautions that must be undertaken to
prevent the contamination of an analyzed substance or to prevent
cross contamination between substances can decrease the overall
usage efficiency of a conventional flow cytometer. The exercise of
these contamination precautions can also delay the start of and
increase the costs of analyses obtained from the conventional flow
cytometer. Occasionally, within clinical or hospital settings,
important or even critical patient treatment decisions depend upon
the rapid completion of analyses of biological samples, such as
blood or other bodily fluids. Thus, inefficiencies in analytical
capabilities can have detrimental health consequences for patients.
Furthermore, these biological specimens are often withdrawn from a
patient using a syringe and then subsequently transferred to
holding vessels, such as the pressurized container 20 (FIG. 2) of a
conventional flow cytometer. Each such transfer creates new
opportunities for contamination or possible spoilage of the sample.
Both time and contamination problems could be reduced if the
specimen is transferred to the analytical instrument, such as a
flow cytometer, in the same syringe used to obtain the
specimen.
[0009] As a result of the above considerations, there is a need in
the art for a simplified sample introduction system for a flow
cytometer that eliminates many of the sample transfer lines,
vessels and valves, that can reduce the preparation time required
to initiate an analysis with the flow cytometer and that allows a
greater number of samples to be analyzed in a given time with
minimal contamination concerns. The present invention addresses
such a need.
SUMMARY OF THE INVENTION
[0010] In order to address the above-noted needs in the art of
sample introduction to flow cytometers, a method and apparatus for
improved sample introduction herein disclosed. The method and
apparatus of the instant invention include syringe-based sample
introduction to a flow cytometer.
[0011] A first object of the present invention is to provide a
sample introduction apparatus for a flow cytometer that has the
advantages of utilizing fewer components and occupying less space
than are required within a conventional flow cytometer sample
introduction apparatus. A second object of the present invention is
to provide a sample introduction apparatus for a flow cytometer
that has the advantage of reducing the opportunities for specimen
contamination relative to conventional flow cytometer sample
introduction apparatus. Another object of the present invention is
to provide a sample introduction apparatus for a flow cytometer
that has the advantages of increasing analytical efficiency and
reducing preparation or set up time in relation to conventional
flow cytometer sample introduction apparatus. Yet another object of
the present invention is to provide a flow cytometer having an
improved sample introduction apparatus that incorporates one or
more of the advantages described above. A still further object of
the present invention is to provide a method of sample introduction
to a flow cytometer that provides one or more of the advantages
described above.
[0012] The aforementioned objects and advantages are realized
through the disclosure, herein of a method and apparatus for a
syringe-based sample introduction system for a flow cytometer. A
preferred embodiment, in accordance with the present invention, of
a flow cytometer sample introduction apparatus comprises a syringe
having a barrel portion containing the specimen, a plunger portion
within the barrel portion and a needle portion that penetrates a
nozzle container and extends into a nozzle volume of a flow
cytometer; a one-way port in the nozzle container forming a seal
against the syringe needle; a mounting platform coupled to both the
syringe and to the flow cytometer; a syringe pump coupled to the
syringe plunger portion and comprising a motor, a clamping
mechanism and a drive mechanism; a pressure sensor coupled to a
sheath fluid line of the flow cytometer; and a controller module
electronically coupled to the pressure sensor and to the motor. The
clamping mechanism of the syringe pump may be coupled to either a
flange portion of the syringe barrel portion, to the mounting
platform or to the flow cytometer itself. The controller module
adjusts the force applied to the syringe plunger by the syringe
pump in response to variations in sheath fluid pressure relayed to
it by the pressure sensor, thereby maintaining a constant pressure
differential between the sheath fluid and the analyzed
substance.
[0013] A preferred embodiment, in accordance with the present
invention, of a method for sample introduction to a flow cytometer
comprises the steps of: providing a syringe having a barrel portion
containing the specimen, a plunger portion within the barrel
portion and a needle portion that penetrates a nozzle container and
extends into a nozzle volume of a flow cytometer; providing a
one-way port in the nozzle container forming a seal against the
syringe needle; providing a mounting platform coupled to both the
syringe and to the flow cytometer for holding the syringe in place
relative to the flow cytometer; providing a syringe pump coupled to
the syringe plunger portion and comprising a motor, a clamping
mechanism and a drive mechanism; providing a pressure sensor
coupled to a sheath fluid line of the flow cytometer; providing a
controller module electronically coupled to the pressure sensor and
to the motor; determining pressure variations in the sheath fluid
with the pressure sensor and relaying electronic signals determined
by the pressure variations to the controller module and
transmitting control signals from the controller module to the
motor so as to cause the syringe pump to depress the plunger at a
controlled rate so as to deliver the specimen into the nozzle at an
appropriate rate and a known volume.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a schematic illustration of the operation of a
conventional flow cytometer.
[0015] FIG. 2 is a schematic illustration of a conventional flow
cytometer.
[0016] FIG. 3 is a schematic illustration of a first preferred
embodiment of a sample introduction apparatus for a flow cytometer
in accordance with the present invention.
[0017] FIG. 4 is a schematic illustration of a second preferred
embodiment of a sample introduction apparatus for a flow cytometer
in accordance with the present invention.
[0018] FIG. 5 is a diagram of a conventional syringe, with the
various components labeled.
[0019] FIG. 6 is a schematic illustration of a third preferred
embodiment of a sample introduction apparatus for a flow cytometer
in accordance with the present invention.
DETAILED DESCRIPTION
[0020] The present invention relates to an improved method and
apparatus for sample introduction into a flow cytometer. The
following description is presented to enable one of ordinary skill
in the art to make and use the invention and is provided in the
context of a patent application and its requirements. Various
modifications to the preferred embodiments will be readily apparent
to those skilled in the art and the generic principles herein may
be applied to other embodiments. Thus, the present invention is not
intended to be limited to the embodiments shown but is to be
accorded the widest scope consistent with the principles and
features described herein. To more particularly appreciate the
features and advantages of the method and apparatus of the present
invention, the reader is referred to the appended FIGS. 3-6 in
conjunction with the following discussion.
[0021] FIG. 3 is a schematic drawing of a first preferred
embodiment of a sample introduction apparatus for a flow cytometer
in accordance with the present invention. The sample introduction
apparatus comprises a conventional syringe 102 having a needle
portion 410 that penetrates the nozzle container 2 and extends into
an interior nozzle volume (not shown) within the nozzle container 2
via a one-way port (not shown) in the nozzle container 2, wherein
the one-way port forms a seal against the needle portion 410. The
end of the syringe needle 410 is positioned above the nozzle tip of
the nozzle container 2 within the interior nozzle volume. The
interior of the barrel portion 402 of the syringe 102 is filled
with a sample substance, generally a suspension of particles in a
liquid, the liquid containing or comprising particles that are to
be analyzed in the flow cytometer. In the novel instant invention,
the syringe barrel portion 402 is the substance reservoir 8 (FIG.
1) and the syringe needle replaces the conventional substance
introduction port 9 (FIG. 1). The syringe 102 may be removed from
the sample introduction apparatus and, in general, each substance
to be analyzed will be introduced via its own respective syringe
102. In this fashion, cross contamination between different sample
substances is minimized.
[0022] For clarity in discussion, FIG. 5 provides a drawing of a
conventional syringe in isolation, with its various component parts
labeled. The syringe 102 illustrated in FIG. 5 has a cylindrical
barrel 402 with an outlet or nose 405 at its forward end and a
flange or ear 402a at its rear end. As is commonly known, the
syringe comprises a plunger 420, which is illustrated in greater
detail in inset box 422, that is partially contained within the
cylindrical barrel 402. A plunger gasket or pad 404 may be moved
through the hollow interior of the barrel 402 by applying force
upon plunger head 408 which drives plunger stem 406 and,
consequently, plunger gasket or pad 404. Typically, the nose 405
may be connected to an replaceable influx and dispensing accessory,
such as needle 410, or possibly a tubing (not shown) so that a
liquid held within the cylindrical barrel 402 of the syringe can
either be drawn into the syringe or dispensed out of the
syringe.
[0023] Discussing, once again, the apparatus shown in FIG. 3, it
may be observed that, in addition to the syringe, the novel sample
introduction apparatus comprises a mounting platform 202 coupled to
the flow cytometer for holding the syringe in place relative to the
nozzle container 2, a syringe pump 204 for controlling sample
introduction from the syringe 102 into the nozzle volume 3, a
pressure sensor 212 disposed within the sheath fluid line 4 and a
syringe pump controller 216 electronically coupled to the pressure
sensor 212 via electrical line 214. The syringe pump 204 shown in
FIG. 3 comprises a first plate 206 mechanically engaged to the
flange 402a (FIG. 5), a second plate 210 engaged to the syringe
plunger head 408 (FIG. 5), a conventional drive mechanism such as
mechanical lead screw 208 engaged to both the first plate 206 and
to the second plate 210 for applying a force that causes these two
plates to approach one another and a motor 220 mechanically coupled
to the drive mechanism 208. The motor 220 receives an electrical
control signal from the controller 216 through electrical line 218.
Preferably, the syringe pump 204 also comprises a force sensor,
such as a spring device (not shown) between the second plate and
the syringe plunger head, for monitoring the amount of force
applied to the syringe plunger head by the syringe pump. This
information on the applied force, together with the known cross
sectional area of the syringe plunger pad (which is the same as the
cross sectional area of the hollow internal portion of the syringe
barrel 402) enables the pressure of the substance within the
syringe to be calculated.
[0024] In a preferred method of operation of the instant sample
introduction apparatus (FIG. 3), the syringe pump 204 slowly
depresses the plunger 408 and, thereby, the plunger 404 of the
syringe 102, thus injecting sample substance into the nozzle volume
3. The dispense of the sample is fully controllable through the
operation of the controller 216 upon the motor 220, the controller
216 possibly being a computer that, through software, also controls
or monitors the operation of other aspects of the flow cytometer to
which the novel sample introduction apparatus is coupled. The
pressure sensor 212 in the sheath fluid line 4 allows the
controller to track the sheath fluid pressure and, consequently,
the sheath fluid flow rate introduced into the nozzle container 2.
In response to possible changing sheath flow rates, the controller
may vary the rate of depression of or the amount of force applied
to the syringe plunger, thus allowing the proper pressure
differential, between the sheath fluid and the sample, to be
maintained. Alternatively or additionally, the controller may vary
or adjust the sheath fluid pressure in the sheath fluid line by
conventional means such as regulating a pressure valve controlling
a mechanical pump supplying the sheath fluid, controlling a gas
pressure applied to a pressure vessel containing the sheath fluid
reservoir, etc. In general, the sample fluid pressure should be
approximately 0.1-0.3 pounds per square inch greater than the
sheath fluid pressure. Because, in general, the amount of sample
dispensed from the syringe 102 is precisely known for a known
linear movement of the plunger 404 with respect to the barrel 402
(FIG. 5), the rate of volumetric sample introduction into the
nozzle volume 3 may be precisely known or controlled. Further, if
the particle density within the sample is known, then the absolute
number of particle events-per-second through the nozzle of the flow
cytometer may be calculated from the rate of volumetric sample
introduction.
[0025] Because a new syringe is used for each respective sample,
the need for special sample introduction lines and associated
valves and reservoirs is eliminated and any cross-contamination
between samples or contamination from non-sterile parts is
minimized. To replace a first sample with a second sample, the user
performs a method comprising the following sequence of steps:
[0026] Step 1. Disengage top plate 210 from syringe plunger head;
[0027] Step 2. Extract first syringe 102, containing first sample,
from one-way port in nozzle container 2; [0028] Step 3. Insert new
syringe 2, containing second sample, into one-way port of nozzle
container 2; [0029] Step 4. Engage top plate with plunger head of
second syringe; [0030] Step 5. Optionally or as required,
re-calibrate new lead screw position in controller software.
[0031] FIG. 4 is a schematic drawing of a second preferred
embodiment of a sample introduction apparatus for a flow cytometer
in accordance with the present invention. The second preferred
embodiment shown in FIG. 4 differs from the first preferred
embodiment, already discussed with reference to FIG. 3, only in
regards to the manner in which the syringe pump components are
configured. In the preferred embodiment shown in FIG. 4, the motor
220 is engaged to the same mounting platform 202 that holds the
syringe 102 in position relative to the nozzle container. Thus, the
first plate 206 is eliminated and the drive mechanism passes
through the mounting platform 202 and the second plate 210. The
syringe pump mechanism illustrated in FIG. 4 also acts as a
clamping mechanism for maintaining the syringe 102 immobile
relative to the mounting platform 202.
[0032] FIG. 6 is a schematic illustration of a third preferred
embodiment of a sample introduction apparatus for a flow cytometer
in accordance with the present invention. The sample introduction
apparatus shown in FIG. 6 is identical to that shown in and already
discussed with reference to FIG. 4, except for the way in which the
syringe needle is introduced into the nozzle volume. In the
apparatus shown in FIG. 4, the syringe needle is directly
introduced into the nozzle volume and operates as the substance
introduction port 9 (FIG. 1). However, since there may be
variations between the sizes or tip shapes of different syringe
needles, it is not always possible to assure that the correct
hydrodynamic focusing of sheath fluid with entrained substance
particles will be consistently observed for all syringes. The
sample introduction apparatus illustrated in FIG. 6 overcomes this
problem through the use of a hollow receptacle 222 that resides
within the nozzle volume and within which the syringe needle 410
fits. Preferably, the receptacle 222 has an interior gasket into
which the syringe needle snugly fits and against which the needle
forms a seal. The end of the receptacle is of the correct size and
shape and at the correct location to assure proper hydrodynamic
focusing. Since biological particles of the substance to be
analyzed are introduced to the sheath fluid only from the end of
the receptacle, changing from a first syringe needle to a second
syringe needle does not affect the fluid flow properties as the jet
exits the needle.
[0033] An improved method and apparatus for sample introduction
into a flow cytometer have been disclosed and have been described
according to some preferred explanatory embodiments. Those skilled
in the art can now appreciate, from the foregoing description, that
the broad techniques of the embodiments of the present invention
can be implemented in a variety of forms. For instance, although
specific configurations of syringe pumps have been discussed in
regards to the preferred embodiments, it should be noted that a
syringe pump, as utilized in the present invention, is, in its most
basic form and need only be an adjustable clamping mechanism that
is engaged, at a first end, to the plunger and that is also
engaged, at a second end, to one of the syringe barrel, the
mounting platform, or the flow cytometer. Therefore, while the
embodiments of this invention have been described in connection
with particular examples thereof, the true scope of the embodiments
of the present invention should not be so limited since many
variations and equivalents of the method and the apparatus may be
carried out without departing from the scope of the invention as
specified in the accompanying claims.
* * * * *