Chemistry: analytical and immunological testing – Biological cellular material tested
Reexamination Certificate
2000-09-18
2004-06-08
Wallenhorst, Maureen M. (Department: 1743)
Chemistry: analytical and immunological testing
Biological cellular material tested
C422S082010, C209S003100, C209S003200, C209S004000, C209S571000, C209S127400
Reexamination Certificate
active
06746873
ABSTRACT:
I. TECHNICAL FIELD
This invention relates to a flow cytometry system and methods of operating both analytical and drop flow cytometers including apparatus and methods of unclogging or dislodging of media or gas from the inside of devices which may become clogged, Specifically, the invention focuses upon a device which may be used to unclog nozzles, dislocate gas, or clean exterior surfaces of flow cytometers used in the cytometry industry, which are subject to clogging, entrapping gas, or collecting adherents to exterior surfaces.
II. BACKGROUND
The desire to unclog, dislocate entrapped gas, and clean nozzles or a nozzle body has been known in some industries for many years. This desire has been quite acute for quite some time in the cytometry field. Cytometers are sometimes used to separate or sort particles from one another based upon the differences detected by shining a high intensity light upon each particle then discerning differences between the amount of light reflected from each particle. These particles may be quite variable based upon the application of the user. They may be biological cells of plant or animal matter or particles of other materials. All of these various particles will vary in size, shape, homogeneity, texture, and adhesion properties.
As shown in
FIG. 1
, the sheath fluid (
8
) is forced into the nozzle chamber (
11
) surrounding the sample tube or sample introduction element (
9
) at the same time that the sample is injected through the sample tube into the nozzle chamber. Both fluids travel down the chamber with the sample remaining in the center of the chamber. In an ideal sorting-type of setup the sample particles travel in line to the orifice where they exit a microscopic nozzle orifice or nozzle aperture (
13
) (typically 50-250 microns) into the free fall area within which droplets form and fall. Generally, at this point, the characteristics of the sample are determined at high speeds, sometimes as rapidly as 40,000 drops per second. In the typical application, the samples are then sorted at high speeds into containers based upon the detected characteristics. Thus, predictability and consistency are crucial to accurate detection and to accurate sorting of the samples. Unwelcome variations in the stream emanating from the nozzle, either in volume or in direction or both, may have significant effects on the ability of the user to provide accurate results.
In practice, particles and gas in the sheath fluid or nozzle aperture adherents or the sample particles injected into the nozzle chamber accumulate faster that they can exit the nozzle and can begin filling the nozzle chamber or occluding the nozzle aperture with sample particles or gas bubbles. This accumulation of particles or gas can cause partial or total clogs in the nozzle or nozzle aperture.
FIGS. 1
,
2
and
3
show a typical cytometer nozzle or exterior surface of a flow cytometer nozzle and area in which such clogging may occur. The problem of clogged nozzles also causes problems relating to the limited shelf life of samples which may be biological in nature and any delays relating to equipment malfunction may require completely starting an experiment from scratch.
Another source of nozzle clogs is related to homogeneity of the sample. The sample preparer, for some reason, may be unable to filter the sample prior to sorting it on the cytometer or the filtered samples may agglutinate. In this case, some of the particles may be larger than the nozzle orifice which will immediately cause clogs.
More specifically, significant advances on sorting sperm for a variety of purposes have been made in recent years. Yet, this type of sample is especially prone to clogging. At present, the only quantitative technique used to achieve the separation of X- and Y-chromosome bearing sperm has been that involving individual discrimination and separation of the sperm through the techniques of flow cytometry. This technique appeared possible as a result of advances and discoveries involving the quantitative dye absorption of X-and Y-chromosome bearing sperm. This was discussed early in U.S. Pat. No. 4,362,246 and significantly expanded upon through the techniques disclosed by Lawrence Johnson in U.S. Pat. No. 5,135,759. The Johnson technique of utilizing flow cytometry to separate X- and Y-chromosome bearing sperm has been so significant an advancement that it has for the first time made the commercial separation of such sperm feasible. While still experimental, separation has been significantly enhanced through the utilization of high speed flow cytometers such as the MoFlo® flow cytometer produced by Cytomation, Inc. and discussed in a variety of other patents including U.S. Pat. Nos. 5,150,313, 5,602,039, 5,602,349, and 5,643,796 as well as international PCT patent publication WO 96/12171. While the utilization of Cytomation's MoFlo® cytometers has permitted great increases in speed, and while these speed increases are particularly relevant given the high number of sperm often used, certain problems have still remained. In spite of the almost ten-fold advances in speed possible by the MoFlo® flow cytometer, shorter and shorter sorting times have been desired for several reasons. First, it has been discovered that as a practical matter, the sperm are time-critical cells. Their fertility decreases with increased delay time. Second, the collection, sorting, and insemination timings has made speed an item of high commercial importance. Thus, the time critical nature of the sperm cells and the process has made speed an essential element in achieving high efficacy and success rates. Naturally, clogging which greatly increases the time required for sorting of the sperm, can be debilitating to the entire success of the process.
Clogging can also occur from the particular sheath fluid used in cytometry operations. The sheath fluid typically used on a cytometer is that of a saline solution including other additives as needed. This saline may form salt crystals on the outside on the nozzle orifice and slowly restrict the exit orifice of the nozzle or otherwise disturb the natural spraying direction of the nozzle. This may result in a partial or complete clog of the nozzle, and can exacerbate problems caused by sample clumping.
Perhaps one of the most significant problems that those in some fields have faced is that of clearing the orifice of the nozzle without damaging it in some way. While this basic concept seems quite simple, implementation is not so straightforward. The operator or other user was faced with the decision to attempt unclogging in situ while it is attached to the cytometer and properly aligned or to remove the nozzle, clean it and then restart the very tedious and slow realignment steps which are necessary if the nozzle is removed before it can be used again for sorting.
One concept put forward for clearing a nozzle in situ involves inserting a thin wire or similar device into the orifice of the nozzle. While this may seem quite straightforward, the problem of finding the orifice of the nozzle which may be 50 to 250 microns in diameter is quite difficult. Further the small diameter of the wire would make it far too delicate to practically thread into the orifice. Another complication to this approach is the small and difficult-to-reach area where a cytometer nozzle is typically located on the instrument. Even if the aforementioned problems were overcome, the nozzle would likely become damaged as a result of the insertion.
Another concept which has been discussed involves the use of applying a vacuum from the outside of the nozzle orifice, which suffers from a clog or particle. This approach has practical limitations involving sealing around the exterior of the nozzle to allow a vacuum to develop. A vacuum source would need to be generated of sufficient magnitude to be of benefit to the nozzle. This approach is complicated by touching the nozzle in situ and thereby disturbing its sensitive alignment and flow path. Potentially, the vacuum source could make a nozzle clog worse by pulling
Buchanan Kristopher S.
Ferguson Douglas H.
Herickhoff Lisa
Malachowski George C.
Ottenberg Matthias J. G.
Santangelo Law Offices, P.C
Wallenhorst Maureen M.
XY, Inc.
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