Abstract:
Provided herein are improved multi-way cell sorter systems and methods. For example, provided are systems and methods for the collection of cells that are sorted in multiple directions. The systems and methods allow for the construction of a multi-way sorter (e.g., a ten-way sorter in the space that currently only allows four-way sorting). In addition the device may actively sense the arrival of drops (with cells of interest) at a sample tube, and trigger an alarm when the drops&#39; arrivals deviate from an expected pattern.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    Pursuant to 35 U.S.C. §119 (e) this application claims priority to the filing date of U.S. Provisional Patent Application Ser. No. 61/480,867 filed Apr. 29, 2011; the disclosure of which application is herein incorporated by reference. 
     
    
     INTRODUCTION 
       [0002]    The present invention relates to flow cytometers and instruments for high speed identification and sorting of particles, such as cells. 
         [0003]    Flow cytometry is a valuable method for the analysis and isolation of biological particles such as cells and constituent molecules. As such it has a wide range of diagnostic and therapeutic applications. The method utilizes a fluid stream to linearly segregate particles such that they can pass, single file, through a detection apparatus. Individual cells can be distinguished according to their location in the fluid stream and the presence of detectable markers. Thus, a flow cytometer can be used to produce a diagnostic profile of a population of biological particles. 
         [0004]    Isolation of biological particles has been achieved by adding a sorting or collection capability to flow cytometers. Particles in a segregated stream, detected as having one or more desired characteristics, are individually isolated from the sample stream by mechanical or electrical removal. A common flow sorting technique utilizes drop sorting in which a fluid stream containing linearly segregated particles is broken into drops and the drops containing particles of interest are electrically charged and deflected into a collection tube by passage through an electric field. 
         [0005]    Typically, the linearly segregated particles in the stream are characterized as they pass through an observation point situated just below the nozzle tip. Once a particle is identified as meeting one or more desired criteria, the time at which it will reach the drop break-off point and break from the stream in a drop can be predicted. Ideally, a brief charge is applied to the fluid stream just before the drop containing the selected particle breaks from the stream and then grounded immediately after the drop breaks off. The drop to be sorted maintains an electrical charge as it breaks off from the fluid stream, and all other drops are left uncharged. The charged drop is deflected sideways from the downward trajectory of the other drops by an electrical field and collected in a sample tube. The uncharged drops fall directly into a drain. 
         [0006]    Droplet sorters deflect drops that contain cells of interest by applying a charge (typically 50-150 volts) to the drops. The drops are deflected by an electrostatic field and, depending on the charge, follow different trajectories so that that arrive at a collection tube. The cells can be distributed over multiple groups by applying different charges, each discrete charge guiding a drop to a particular tube. Originally cell populations were divided in to two groups: a left and a right sort. lately the number of sort directions (groups) has been increased to  4  (most sorters) or even  6 . An example flow cytometer system having multiple collection tubes is provided in U.S. Pat. No. 5,483,469, which is incorporated herein by reference in its entirety. 
         [0007]    The number of sort directions is currently limited by the number of collection tubes that can be placed on the axis along which the drops are distributed. The typical drop spread in one direction is about 22 mm The tube centers are 14 mm apart so that with difficulty three groups can be sorted. 
         [0008]    The tube size is not the only factor in limiting the number of sort directions. It is also difficult to place sorted drops in close proximity because the drops carry a charge. As such, charged drops will repel each other. As the drops accumulate into a bigger volume the charge grows disproportionally faster. Due to the accumulation of charge, the sorted cell volume tends to want to break into smaller drops. These drops repel and push away each other causing drops to jump around erratically, sometimes even jumping into adjacent tubes with drops of opposite charge, thus severely affecting the purity of a sort. 
       SUMMARY 
       [0009]    Provided herein are improved multi-way cell sorter systems and methods. For example, provided are systems and methods for the collection of cells that are sorted in multiple directions. The systems and methods allow for the construction of a multi-way sorter (e.g., a ten-way sorter in the space that currently only allows four-way sorting). In addition the device may actively sense the arrival of drops (with cells of interest) at a sample tube, and trigger an alarm when the drops&#39; arrivals deviate from an expected pattern. Such a signal could be used to move the collection tubes into a safe position preventing contamination of the sorted samples. This device is desirable for clinical sorting. The device is also suitable as a disposable unit. 
         [0010]    The systems and methods presented provide a cure for the drop accumulation problem, and allow deflected drop streams to be placed in closer proximity without affecting stream stability. 
         [0011]    Exemplary systems and methods presented include a sorted drop receptacle (or carrier) that consists of a row of sort tubes (or deflection tubes) that are open at both sides. The deflected drops are accordingly aimed at the inside of a sort tube. Each sort tube is individually grounded so that the deflection charge on the drops is harmlessly deflected to ground. Thus the drops no longer carry a charge and can grow into larger drops that slide down the sort tube. Each sort tube is inserted in an opening of a sample collection tube. Since the sort tubes can be bent, the collection tubes no longer need to be placed along a line, but can be configured in a staggered pattern. As such, a collection area that once held three tubes in a straight line, can now accommodate five tubes in a staggered configuration. Since the sort tubes can be narrower than the collection tubes, the tops of the five sort tubes can be placed along a 20 mm line, with the bottom of the tubes leading to five staggered collection tubes place in a 20×30 mm area. 
         [0012]    In one embodiment, an arrangement of ten collection tubes with ten sort tubes can be fitted on the area of a standard microscope slide. A plastic carrier with the dimensions of a microscope slide may hold about ten thin walled stainless steel deflection tubes. The ten deflection tubes lead to ten plastic collection tubes that are attached to the bottom of the plastic carrier. The whole unit may be made available as one sterile and disposable unit. 
         [0013]    The top of the sort tubes may also be closed off when appropriate. For example, the system can monitor the arrival of drops in the sort fractions by measuring the charge that is deposited in the individual metal sort tubes. If the metal sort tubes are connected to ground via a current-to-voltage converter, with a variable integration time, the voltage measured at each sort tube reflects the number of drops that are deposited in each tube per-unit-time. A computer program can be configured to predict the expected voltage generated for each sort direction. If the measured voltage differs from the expected voltage, the computer can instruct a stepper motor to cover the sort tubes, or move the collection tray into a safe, covered (or otherwise deactivated) position, preventing contamination of the sorted fractions with unwanted cells. 
         [0014]    The carrier presented may be used as a multi-way (e.g. ten-way) sorter in all current influx sorters, without the need for any changes to the influx design. The possibility to continuously monitor the number of cells that are deposited in each tube also provides a safeguard that currently is not available on cell sorters. This control device should be very desirable for sorts that require a high degree of confidence in the purity of the cell fractions. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0015]    The accompanying drawings, which are incorporated herein, form part of the specification. Together with this written description, the drawings further serve to explain the principles of, and to enable a person skilled in the relevant art(s), to make and use systems and methods in accordance with the present invention. 
           [0016]      FIG. 1  is a perspective view of a portion of a multi-way cell sorter carrier, in accordance with one embodiment presented herein. 
           [0017]      FIG. 2  is a side view of a portion of the multi-way cell sorter carrier of  FIG. 1 . 
           [0018]      FIG. 3  is a front view of a portion of the multi-way cell sorter carrier of  FIG. 1 . 
           [0019]      FIG. 4  is a top view of a portion of the multi-way cell sorter carrier of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    The following detailed description of the figures refers to the accompanying drawings that illustrate an exemplary embodiment of a carrier for a cell sorter system. Other embodiments are possible. Modifications may be made to the embodiments described herein without departing from the spirit and scope of the present invention. Therefore, the following detailed description is not meant to be limiting. 
         [0021]      FIG. 1  is a perspective view of a portion of a multi-way cell sorter carrier  100 , in accordance with one embodiment presented herein.  FIG. 2  is a side view of a portion of multi-way cell sorter carrier  100 .  FIG. 3  is a front view of a portion of multi-way cell sorter carrier  100 .  FIG. 4  is a top view of a portion of multi-way cell sorter carrier  100 . Carrier  100  may be incorporated into a cell sorter system. An exemplary cell sorter system is provided in U.S. Pat. No. 5,483,469, which is incorporated herein by reference in its entirety. 
         [0022]    In the embodiment shown, carrier  100  includes a plurality of deflection (or sort) tubes  102  and corresponding collection tubes  104 . Each deflection tube  102  is hollow, with openings at both ends. Openings  106  of the deflection tubes  102  are aligned collinearly with one another, along an axis of the deflection. As such, when carrier  100  is incorporated into a cell sorter system, openings  106  of deflection tubes  102  receive deflected charged droplets. 
         [0023]    A second opening of each deflection tube  102  is positioned with respect to a corresponding opening in a collection tube  104 . As such, charged droplets received within deflection tubes  102  slide into collection tubes  104 . Collection tubes  104  are preferably positioned in a staggered arrangement in order to maximize the spacing and number of collection tubes used in carrier  100 . To facilitate positioning of deflection tubes  102  and collection tubes  104 , and/or to secure the connection between deflection tubes  102  and collection tubes  104 , a carrier plate  108  is used. As shown, only five deflection tubes  102  and five collection tubes  104  are presented. However, in one embodiment, up to ten or more deflection tubes and collection tubes may be used. 
         [0024]    In one embodiment, each deflection tube  102  is formed of an electrically conductive material (e.g., a metal, such as, stainless steel). Each collection tube  104  may be formed of a lightweight plastic material. Carrier plate  108  may be formed of a plastic material. 
         [0025]    In another embodiment, each the deflection tube  102  is further coupled to a current-to-voltage converter (CVC) (not shown), which is appropriately grounded. The grounding of the CVC allows for the removal of the charge of the drops received in the deflection tube  102 . Further, CVC allows for the measurement of current at deflection tube  102 , which is a function of the charged droplet arriving at deflection tube  102 . As such, the arrival of drops at carrier  100  can be monitored by measuring the charge that is deposited in the individual deflection tubes  102 . If the deflection tubes  102  are connected to ground via CVC, with a variable integration time, the voltage measured at each deflection tube reflects the number of drops that are deposited in each tube per-unit-time. A computer program can be configured to predict the expected voltage generated for each sort direction. If the measured voltage differs from the expected voltage, the computer can instruct a stepper motor to cover the carrier, or move the carrier into a safe, covered, and/or deactivated position, preventing contamination of the carrier with unwanted cells. 
         [0026]    In yet another embodiment, each deflection tube  102  may include two segmented pieces  102   a,    102   b.  The segmentation of the deflection tube may be formed by a “bend” in the tube. Since the deflection tubes can be bent, the collection tubes no longer need to be placed along a line, but can be configured in a staggered pattern. As such, a collection area that once held three tubes in a straight line, can now accommodate five tubes in a staggered configuration. Since the deflection tubes can be narrower than the collection tubes, the tops of the five deflection tubes can be placed along a 20 mm line, with the bottom of the tubes leading to five staggered collection tubes placed in a 20×30 mm area. 
         [0027]    In still another embodiment, there is provided a carrier for receiving cells sorted from a cell sorter system. The carrier includes a plurality of hollow deflection tubes and a plurality of corresponding collection tubes. Each deflection tube includes a first opening at a first end and a second opening at a second end. The first opening of each deflection tube is aligned with the first opening of an adjacent deflection tube such that the first openings are all collinear. The second openings of the plurality of deflection tubes are staggered with respect to one another. Each collection tube includes an opening positioned to receive a cell passed through and exiting a corresponding deflection tube. In one embodiment, each deflection tube and/or each collection tube is electrically insulated. In one embodiment, the carrier further includes a current detection circuit coupled to at least one deflection tube, or a current detection circuit coupled to each deflection tube. The current detection circuit may further include a current-to-voltage converter to detect the presence of a charged drop entering the deflection tube, and/or an integrator to detect a number of drops per-unit-time entering the deflection tube. Each deflection tube may be formed of a metallic material. Each collection tube may be formed of a plastic material. In one embodiment, the carrier includes ten or more deflection tubes and ten or more corresponding collection tubes. 
         [0028]    Further, there is provided a method for configuring a carrier for receiving cells sorted by a cell sorter system. The method includes aligning a plurality of hollow deflection tubes such that a first open end of each deflection tube is positioned collinearly with a first open end of an adjacent deflection tube. A second open end of each deflection tube is positioned staggered with respect to a second open end of an adjacent deflection tube. The method further includes positioning a plurality of corresponding collection tubes such that an opening for each collection tube is positioned to receive a cell passed through and exiting a corresponding deflection tube. Each deflection tube may be electrically insulated. Each collection tube may be electrically insulated. The method may further include coupling a current detection circuit to at least one deflection tube, or coupling a current detection circuit to each deflection tube. The current detection circuit may include: a current-to-voltage converter to detect the presence of a charged drop entering the deflection tube; and/or an integrator to detect a number of drops per-unit-time entering the deflection tube. Each deflection tube may be formed of a metallic material. Each collection tube may be formed of a plastic material. The carrier may be configured to include ten or more deflection tubes and ten or more corresponding collection tubes. 
       Conclusion 
       [0029]    The foregoing description of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Other modifications and variations may be possible in light of the above teachings. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, and to thereby enable others skilled in the art to best utilize the invention in various embodiments and various modifications as are suited to the particular use contemplated. It is intended that the appended claims be construed to include other alternative embodiments of the invention; including equivalent structures, components, methods, and means. 
         [0030]    It is to be appreciated that the Detailed Description section, and not the Summary and Abstract sections, is intended to be used to interpret the claims. The Summary and Abstract sections may set forth one or more, but not all exemplary embodiments of the present invention as contemplated by the inventor(s), and thus, are not intended to limit the present invention and the appended claims in any way. 
         [0031]    It is to be understood that this invention is not limited to particular embodiments described, as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting, since the scope of the present invention will be limited only by the appended claims. 
         [0032]    Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range, is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges and are also encompassed within the invention, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the invention. 
         [0033]    Certain ranges are presented herein with numerical values being preceded by the term “about.” The term “about” is used herein to provide literal support for the exact number that it precedes, as well as a number that is near to or approximately the number that the term precedes. In determining whether a number is near to or approximately a specifically recited number, the near or approximating unrecited number may be a number which, in the context in which it is presented, provides the substantial equivalent of the specifically recited number. 
         [0034]    Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present invention, representative illustrative methods and materials are now described. 
         [0035]    All publications and patents cited in this specification are herein incorporated by reference as if each individual publication or patent were specifically and individually indicated to be incorporated by reference and are incorporated herein by reference to disclose and describe the methods and/or materials in connection with which the publications are cited. The citation of any publication is for its disclosure prior to the filing date and should not be construed as an admission that the present invention is not entitled to antedate such publication by virtue of prior invention. Further, the dates of publication provided may be different from the actual publication dates which may need to be independently confirmed. 
         [0036]    It is noted that, as used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise. It is further noted that the claims may be drafted to exclude any optional element. As such, this statement is intended to serve as antecedent basis for use of such exclusive terminology as “solely,” “only” and the like in connection with the recitation of claim elements, or use of a “negative” limitation. 
         [0037]    It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination. All combinations of the embodiments are specifically embraced by the present invention and are disclosed herein just as if each and every combination was individually and explicitly disclosed, to the extent that such combinations embrace operable processes and/or devices/systems/kits. In addition, all sub-combinations listed in the embodiments describing such variables are also specifically embraced by the present invention and are disclosed herein just as if each and every such sub-combination of chemical groups was individually and explicitly disclosed herein. 
         [0038]    As will be apparent to those of skill in the art upon reading this disclosure, each of the individual embodiments described and illustrated herein has discrete components and features which may be readily separated from or combined with the features of any of the other several embodiments without departing from the scope or spirit of the present invention. Any recited method can be carried out in the order of events recited or in any other order which is logically possible.