Abstract:
A centrifuge syringe for separating components of a fluid sample having different sedimentation densities is disclosed. The centrifuge syringe allows for the withdrawal of a sample through a sterile needle into the syringe. The syringe contains a movable plunger containing a restriction and which may contain a density gradient separation solution. The plunger is connected to a handle which is detachable to allow centrifugation. After centrifugation, the handle is reattached to the plunger, and the specimen is removed from the syringe.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to the field of centrifugation in general, and more particularly to centrifuge tubes that also function as syringes. 
     The prior art contains numerous devices that provide for the extraction of fluid samples as well as their centrifugation. For example, U.S. Pat. No. 4,459,997 to Sarstedt discloses a blood extraction and centrifugation device that provides for the withdrawal of blood from a patient into a tube that can be used for centrifugation. The centrifugation tube is a simple straight-walled tube that does not contain a constricted region or provide for the use of density gradient material. 
     U.S. Pat. No. 4,020,831 to Adler discloses a syringe that can draw a specimen, and then allow disassembling of certain parts of the syringe so that the portion of the syringe holding the specimen can be placed in a centrifuge. The syringe also contains a plug of a specific density. During centrifugation, the specimen will separate so that lighter phases are above the plug, and heavier phases are below the plug. This device does not provide for easy removal of the separated phases, and does not provide for the use of a density gradient material. 
     In addition, U.S. Pat. No. 3,965,889 to Sachs discloses an apparatus for the sampling of blood and the separation of plasma. The syringe includes a thermosealable walled container with a medial restriction into which blood is drawn. After the blood is drawn into the container, the container is removed and placed in a carrier for centrifugation, after which the container can be sealed at the restriction to separate the phases of blood. This device requires the removal of the specimen container to a different carrier for centrifugation, thereby increasing the risk of contamination of the specimen. 
     There is thus a need in the art for a syringe that can be used to separate materials of different densities which is an integrated unit that does not require transfer of sample to a different container for centrifugation and therefore reduced risk of contamination. The present invention provides a sterile environment in which all required cell sorting manipulations can be carried out. 
     SUMMARY OF THE INVENTION 
     The present invention solves the above-stated needs by providing a centrifuge syringe that provides an integral syringe and centrifugation tube in one apparatus and further provides for the use of density gradient material to enhance the separation capabilities. The apparatus has a specimen container with one end having a fitting covering an orifice adapted for the sterile introduction or ejection of fluids, and the opposite end having a central orifice for the sealing engagement with a handle of a plunger. The handle is connected to a plunger at one end, which is located within the container. The opposite end of the handle remains outside the specimen container, and is used to move the plunger longitudinally within the container. 
     The present invention is specially adapted for use with a density gradient material for enhanced cell separation. The density gradient material is placed in the plunger of the container before the addition of the specimen to be centrifuged. The plunger has a bottom wall attached to the handle, and a top wall with a restriction, creating a fluid receiving area between the two walls. The use of a restriction in the top wall further aids in cell separation, and reduces the possibility that the separated phases will mix during collection of the phases after centrifugation. 
     The apparatus is also specially designed to allow the detachment of a needle or other sterile connecting device and the handle before centrifugation of the specimen. The handle may then be reattached to facilitate the removal of the specimen. Removal of the specimen can be easily accomplished by ejecting the low density phase, which reduces the possibility of contamination of the sample. Preferably the ejecting will be done with the syringe in an inverted position. 
     Further aspects of the invention include a closed system for centrifuge fluid analysis wherein the syringe according to the invention is used to draw a previously collected sample from a sterile container. Methods for separating cells utilizing the above describe syringe also form further aspects of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional view of a centrifuge syringe according to the invention before the extraction of a specimen; 
     FIG. 2 is a cross-sectional view of the centrifuge syringe of FIG. 1 upon introduction of the specimen; 
     FIG. 3 is a cross-sectional view of the centrifuge syringe of FIG. 1 after centrifugation; 
     FIG. 4 is a cross-sectional view of the centrifuge syringe of FIG. 1 upon removal of the specimen; 
     FIG. 5 is a cross-sectional view of an alternative embodiment of the centrifuge syringe according to the invention; 
     FIG. 6 is a perspective view of the plunger of the alternative embodiment of FIG. 5; 
     FIG. 7 is a cross-sectional view of the plunger through line 7--7 of FIG. 5; 
     FIG. 8 is a cross-sectional view of an alternative embodiment of the centrifuge syringe plunger having a valve; 
     FIGS. 9A-9E are examples of the shape of the opening of the constriction member in the centrifuge syringe; 
     FIGS. 10A-10F are cross-sectional views of alternative embodiments of the plunger of the centrifuge syringe; and 
     FIG. 11 is a cross-sectional view of an alternative embodiment of the centrifuge syringe of FIG. 5; and 
     FIG. 12 is diagrammatic illustration of a closed system for blood analysis according to the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     One embodiment of centrifuge syringe 10 according to the invention is illustrated in FIG. 1. The centrifuge syringe 10 includes a specimen container 14 with a central orifice surrounded by fitting 12 adapted for receiving a needle 13, a handle 16 and a plunger 18. Fitting 12 may be any type of locking tip adapted to hold a needle, for example, a Luer-Lock™ syringe tip. Alternatively, fitting 12 may be a sterile septum adapted for connection with sterile fluid bags and tubes, for example a SAFSITE™ small wire extension set with reflux valve and Spin-Lock™ adaptor available from Burron Medical Inc., Bethlehem, Pa. 
     Handle 16 further preferably comprises knob 22 and a removable connection 24 to plunger 18. As shown in FIGS. 1-4, plunger 18 is single piece, machined or molded from a plastic material. Known medical grade plastic materials may be used. The plunger as shown in FIG. 1 has a funnel-shaped bottom wall 26 that is removably connected to the handle at connection 24. Side wall 27 preferably closely matches the container wall to permit sliding movement but provide an essentially fluid-tight barrier therearound. A top wall is formed by constriction member 28, which defines central opening 29. Alternatively, the outer diameter of side wall 27 may be slightly undersized to facilitate sliding and an o-ring seal provided between side wall 27 and container 14. Removable connection 24 may take the form of, for example, a screw fitting or a snap-fit. Preferably, connection 24 also provides for reattachment of handle 16. If reattachment is not desired, connector 24 may be designed such that handle 16 can be broken off. A suitable connection can be selected by those of ordinary skill in the art. 
     The plunger 18 is filled with a density gradient material 20 before the introduction of a specimen. As is understood by persons of ordinary skill in the art, such materials have specifically defined densities which are selected based on the particular sample material being separated. Examples of density gradient materials include sucrose, albumin and Ficoll™. A preferred material is available from Pharmacia Fine Chemicals of Piscataway, N.J. and Uppsala, Sweden under the trademark PERCOLL™. Preferably, the density gradient material is filled to a level above the constriction member, or at least above the top of opening 29. For example, when using a standard 50 ml syringe, having an inner diameter of about 2.8 cm, the gradient material is preferably filled to a level about 1 mm or more above constriction member 28. This fill level will help to prevent the formation of an interface portion, as explained below, under constriction member 28. 
     Referring to FIG. 2, the introduction of the specimen into centrifuge syringe 10 is illustrated. Specimen 30 is drawn into the syringe through needle 13 secured to fitting 12, aided by the vacuum created by handle 16 and plunger 18 as the handle is pulled out of container 14, drawing the plunger away from fitting 12. The handle should be pulled with sufficiently low force and velocity to avoid mixing of the specimen with the density gradient material onto which the sample is layered. Preferably, when the handle is pulled at an appropriate force, the sample will form a stream which adheres to the side of the container as it is drawn in, as shown in FIG. 2. This will reduce unwanted mixing. Mixing of the two materials is also minimized by the fact that the density of the specimen is significantly lower than the density of the density gradient material. After specimen 30 is drawn into container 14, the container is maintained in an upright position and the sample lies on top of density gradient material 20. 
     Using needle 13, a sample such as peripheral blood may be drawn directly from a patient for analysis. The present invention thus ensures sterility of such a sample by completely eliminating direct handling of the sample prior to introduction into the centrifugation container. Alternatively, as illustrated in FIG. 12, using a sterile septum as fitting 12, blood previously collected by known techniques and stored, for example in a sterile bag 33, may be drawn into the centrifugation container through sterile tubing 35 or other known sterile connection means. The present invention thus ensures a sterile transfer of sample material on a larger scale in a completely closed system, again without direct handling of sample material. 
     Once the specimen has been completely drawn into the container 14, and the handle 16 has been pulled so that the removable connection 24 is located at the central orifice of the specimen container 14, the handle 16 can be removed for the centrifugation step. 
     FIG. 3 illustrates the centrifugation syringe after the centrifugation step has been performed. As shown, the handle 16 has been detached from the plunger 18, which is located at the bottom end of the container 14. Centrifugation of container 14 results in a pellet 32 being formed from the heavier portions of the specimen at the bottom of the plunger 18. Density gradient material 20 is located above pellet 32. An interface portion 34, which contains the cells of interest, is formed between specimen diluent 33 and density gradient material 20, and above constriction member 28. 
     Interface portion 34 may be removed from the centrifuge syringe 10 by inverting the centrifuge syringe and ejecting it off as indicated by arrow 37 in FIG. 4. Further removal of density gradient material 20 and the pellet 32 can be facilitated by reattaching handle 16 to plunger 18 at connection 24. The handle then can be pushed into the container to aid the removal of the material if necessary. 
     According to one theory, the presence of the constriction member with a restricted opening provides a support or nucleus for formation of an intermediate surface tension across the tube. This surface tension impedes the mixing of upper and lower regions (above and below the constriction member) of the tube when, for example, the contents of the upper region are ejected from the tube. Accordingly, the dimensions of the opening of the plunger are dictated by the ability to form a surface tension. A constriction member that is little more than a rim around the interior of the barrel may be sufficient to form the necessary surface tension. Hence, the cross-sectional area of the opening formed by the constriction member may be as little as about 5% or as great as about 95% of the horizontal cross-sectional surface area of the syringe. In an exemplary embodiment, where the syringe has an inside diameter of about 2.8 cm, an aperture having a diameter of about 0.5 cm is suitable. 
     In many applications, it will be desirable to collect only the supernatant fraction containing interface portion 34. In such cases, the pellet is discarded with the syringe. In other cases, the pellet can be removed by mechanical manipulation/disruption. For example, the syringe can be inverted and subjected to vortex mixing. Such mixing will disrupt the pellet into the adjacent liquid phase and will induce movement of this liquid phase and disrupted cells from the second or collection chamber of the syringe into the first chamber of the syringe. 
     An alternative embodiment of the present invention is shown in FIGS. 5-7. Centrifuge syringe 40 has a plunger 42 formed from separate pieces and without sidewalls. Plunger 42 has a flat bottom plate 44, which may be formed by a washer formed from medical grade plastic such as polycarbonate. Bottom plate 44 is preferably circumscribed by a silicone or rubber seal 46 for the creation of an fluid-tight seal between bottom plate 44 and the inside wall of the specimen container 48. Threaded or snap-fit connection 51 is provided in the bottom plate to removably attach handle 50. Plunger 42 has fittings 52, to connect bottom plate 44 to annular constriction member 54, which defines opening 55. Fittings 52 are preferably made of medical grade plastic, such as polycarbonate. Constriction member 54 is funnel-shaped, and preferably made of silicone or rubber. There are preferably three fittings 52, as shown, but there may be only two, or more than three if desired. The constriction member can be secured to the fittings by providing stepped recesses 56 in the constriction member, as shown in FIG. 7, for retaining mushroom like-heads 57 on the fittings. Fittings 52 may be glued to bottom plate 44 preferably with medical grade adhesive. Other means for connection may be devised by persons skilled in the art and the particular type of connection used is not critical so long as a secure connection between the parts is maintained. 
     An advantage of the present invention is that the low density material above the constriction member of the plunger is separated from material beneath by the simple act of, ejecting it with the aid of the plunger, as described above. If the opening at fitting 12 is large enough, the cells of interest may be poured off. This contrasts with many conventional methods of unloading gradient separations using standard straight-wall centrifuge tubes, where materials are separated by carefully pipetting out of the tube or, alternatively, by puncturing the bottom of the tube and allowing the contents of the tube to slowly drip out into collection vessels. Thus, the present invention provides a convenient, simple means for unloading differentially separated materials. In addition, unlike conventional straight-wall tubes, if the centrifuge syringe is dropped or accidentally inverted, the contents will not readily mix due to the presence of the constriction member. Moreover, once separation has taken place, the solution present above the constriction member can be mixed in the tube, without disturbing (or fear of contamination by) the contents of the syringe below the constriction member. Preferably this is done with the syringe in an inverted position as shown in FIG. 4. 
     The separation of materials may be further enhanced by the addition of valve 60 to the plunger, as shown in FIG. 8. The valve 60 is located at opening 62 in plunger 64. Valve 60 may be a one-way valve, or a valve that only opens upon application of a threshold centrifugal force. The valve can be formed by providing flaps of a softer material over hole 62. In a preferred embodiment, the force required to open valve 60 would be about 850 times the normal force of gravity. Valve 60 thus allows heavy cells to pass through during initial centrifugation, and then keeps those cells in place, allowing for further processing, such as washing or mixing, of the lighter cells of interest located above the valve. In this way complete and final manipulation of the cells can be performed in a single sterile container. 
     The shape of opening 29, 55 is not limited to a circular shape, though in general a funnel-shaped constriction member forming a roughly circular shape 29A will be preferred. As shown in FIGS. 9A-E, the opening may also be oval 29B, rectangular 29C, star-shaped 29D, covered by a grid or mesh 29E or any other shape that would create a restricted opening. 
     FIGS. 10A-F are illustrations of alternative shapes and designs for the plunger of the centrifuge syringe according to the invention. FIG. 10A shows a plunger 70 with a flat bottom wall. FIG. 10B shows a plunger 72 with a pointed bottom wall. Plunger 72 with the pointed bottom wall will allow the heavier cells to form a better pellet, which may be desired if the cells are to be collected. Alternatively, plunger 74 with a separate compartment 76 can be utilized to offer optimal collection of cells. FIG. 10D shows a plunger 70 that includes a cell trapping material 78, such as a sponge or gel. Material 78 may contain compounds that specifically bind certain cell types or toxins that kill specific cell types. Material 78 may also be made of a magnetic material if desired. FIGS. 10E and F show alternative embodiments of the plunger that facilitate movement within the container. FIG. 10E shows a plunger 80 with extending contact points 82. The plunger 80 will only contact the container at these points. Similarly, in FIG. 10F, a plunger 84 is shown with extending contact points 86. 
     FIG. 11 illustrates a further alternative embodiment of the centrifuge syringe of FIG. 5 with an additional constriction member. Dual constriction syringe 90 has a bottom plate 92 connected to a first constriction member 94 by fittings 96. Second constriction member 98 is located above first constriction member 94 to create more compartments to allow separation of cells of differing densities. Second fittings 97 may be used to secure second constriction member 98. Additional constriction members could also be added if a sample of several different densities is to be separated. 
     FIG. 11 also illustrates one embodiment of the removable and reattachable connection means between the handle 102 and the bottom plate 92. In this embodiment, an internal screw 100 is used, so that the handle 102 can be removed and then reattached after centrifugation. 
     Preferably, the centrifugation syringe according to the present invention would be provided as a sterilized complete unit with the density gradient material already in place to an appropriate level. In this way, sterility of the syringe is guaranteed and the user need only open the sterile packaging to use the invention. Alternatively, the syringe can be provided in kit form with the density gradient solution separately provided and the needle and handle disattached. The user would then fill the plunger of the syringe with density gradient material, and then assemble the needle and handle before use. 
     EXAMPLE 
     Method of isolating CD34 +  progenitor hematopoietic cells 
     The centrifuge syringe and the method of the invention can be used to isolate CD34 +  progenitor cells from patients treated with chemotherapy and granulocyte colony stimulating factor (G-CSF) as described below. These cells can then be used to repopulate the patient&#39;s lymphohematopoietic system. 
     Human peripheral blood mononuclear cells (PBMC) are obtained by apheresis of patients treated with daily injections of G-CSF (10 μg/kg/day). Samples are then processed according to standard methods understood by persons skilled in the art. 
     Cells are resuspended in 25 ml of calcium-free, magnesium-free PBS and then drawn into the syringe on top of 15 ml of PERCOLL™ solution in a 50 ml conical centrifuge syringe fitted with a plunger containing a constriction member, as illustrated in FIG. 1. This PERCOLL™ solution has a density of 1.062 g/ml (osmolality 280±5 mOsm/kg H 2  O; pH 7.4). The diameter of the opening in the construction member of the syringe preferably is about 0.5 cm. This volume of PERCOLL™ shall be sufficient volume to fill the container to a level higher than about 1 mm above the constriction member. After the sample is drawn in, the needle and plunger are detached. The centrifuge syringe is then centrifuged at about 850 g&#39;s for 30 minutes at room temperature. The upper fraction containing CD34 2  + cells is collected by ejecting the sample into a sterile container.