Abstract
A purified solution of human plasma, MNCs and platelets isolated from whole blood, bone marrow, or stromal vascular fraction cells separated from adipose tissue wherein said purified solution comprises at least 90% by number of the MNCs in said whole blood, bone marrow, or stromal vascular fraction cells separated from adipose tissue, said purified solution comprises at most 10% by number of the red blood cells and granulocytes in said whole blood, bone marrow, or stromal vascular fraction cells separated from adipose tissue, and said purified solution is isolated and separated from said whole blood, bone marrow, or stromal vascular fraction cells separated from adipose tissue during a single centrifugation run.
Claims
1. A process for isolating a purified solution of mononuclear cells (MNCs) from a sample of whole blood, bone marrow, or stromal vascular fraction cells separated from adipose tissue comprising the steps of: a. providing a centrifuge having an axis of rotation; b. providing a compartment within the centrifuge; c. placing the sample of whole blood, bone marrow, or stromal vascular fraction cells into the compartment; d. centrifuging the compartment; f. isolating a purified solution comprising at least 90% by number of the MNCs and at most 10% by number of the red blood cells contained in said whole blood, bone marrow, or stromal vascular fraction cells separated from adipose tissue.
2. The process of claim 1 wherein said purified solution comprises at least 95% by number of the MNCs in said whole blood, bone marrow, or stromal vascular fraction cells separated from adipose tissue.
3. The process of claim 1 wherein said purified solution comprises at most 5% by number of the red blood cells in said whole blood, bone marrow, or stromal vascular fraction cells separated from adipose tissue.
4. The process of claim 1 wherein said purified solution is isolated using a single disposable cartridge.
5. The process of claim 1 wherein said purified solution comprises at most 10% by number of the granulocytes in said whole blood, bone marrow, or stromal vascular fraction cells separated from adipose tissue.
6. A process for isolating a purified solution of MNCs comprising at least 90% MNCs by weight comprising the steps of: a. providing a centrifuge having an axis of rotation; b. providing a disposable cartridge having a funnel shaped compartment; c. placing a sample of whole blood, bone marrow, or stromal vascular fraction cells separated from adipose tissue into said funnel shaped compartment; d. loading said disposable cartridge into said centrifuge; e. centrifuging said disposable cartridge such that said sample being subjected to high G force and urged toward said open end away from the axis of rotation; f. depleting at least 90% of Red Blood Cells (RBCs) from said sample by diverting RBCs into a first storage compartment by a valve system; and g. harvesting at least 90% mononuclear cells (MNCs) from said sample by directing MNCs into said second rigid storage compartment by said valve system.
7. The process of claim 6 comprising at least 95% MNCs by weight.
8. The process of claim 6 wherein at least 95% of said RBCs are depleted from said sample.
Description
BRIEF DESCRIPTION OF THE FIGURES
[0063] The foregoing aspects and many of the attendant advantages of the invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the attached charts and figures, wherein:
[0064] FIG. 1 is a plot of the density and average diameter of various cell types found in human blood;
[0065] FIG. 2 is a plot showing the different densities of various cell types found in human blood;
[0066] FIG. 3 is a table of the proportionate volume of cell populations after centrifugation;
[0067] FIG. 4 is a table of the volume of cells in various volumes of anti-coagulated blood;
[0068] FIG. 5 is a plot of the volume of anti-coagulated blood versus the volume of centrifuged cell populations;
[0069] FIG. 6 is a diagram showing the layers into which human blood separates during centrifugation in a standard test tube;
[0070] FIG. 7 is a diagram showing the layers into which a mixture of human blood and a Ficoll additive separate after centrifugation;
[0071] FIG. 8 is a diagram showing how human blood separates when centrifuged with blood separation discs in a standard test tube;
[0072] FIG. 9 is a table of ESR values of average men and women of different ages.
[0073] FIG. 10 is a drawing illustrates the relative cost of processing four blood samples with several prior art systems and with the current system;
[0074] FIG. 11 is a drawing showing the relative complexity of the disposable component of prior art blood separation systems and the current invention;
[0075] FIG. 12 is a perspective drawing of the disposable cartridge and control module of the present invention;
[0076] FIG. 13 is a diagram providing an overview of the process of the current invention;
[0077] FIG. 14 is a cross-sectional view of several embodiments of the funnel tip of the current invention;
[0078] FIG. 15 is a partial wireframe perspective view of the disposable cartridge, control module, and various features of the control module and the cartridge of the present invention;
[0079] FIG. 16 is an exploded view of the disposable cartridge, control module, and an exemplary centrifuge cup of the present invention;
[0080] FIG. 17 is a perspective view of the control module of the current invention.
[0081] FIG. 18a is a wireframe side view of the disposable cartridge with cut line A-A marked;
[0082] FIG. 18b is a perspective view of the disposable cartridge cut along line A-A.
[0083] FIG. 19 is a perspective cross-sectional view of a disposable cartridge with the narrow bottom of the funnel shown;
[0084] FIG. 20 is a cross-sectional view of a preferred embodiment of the present invention before centrifugation;
[0085] FIG. 21 is a cross-sectional view of a preferred embodiment of the present invention during centrifugation;
[0086] FIG. 22 is a cross-sectional view of the valve system portion of a preferred embodiment of the present invention during centrifugation;
[0087] FIG. 23 is a detail view of the cantilever valve system of an alternative embodiment of the current invention;
[0088] FIG. 24 is a detail perspective view of the cam portion of a preferred embodiment of the present invention;
[0089] FIG. 25 is a cross-sectional view of the flexible conduit of a preferred embodiment of the present invention, showing the relative size of various cells present in human blood and the flexible conduit;
[0090] FIG. 26 is a cross-sectional view of a preferred embodiment of the present invention after ten minutes of centrifugation;
[0091] FIG. 27 is a detail cross-sectional view of the optical sensing portion of a preferred embodiment of the present invention;
[0092] FIG. 28 is a detail cross-sectional view of the valve system, standpipe, RBC collection chamber, and SC collection chamber of a preferred embodiment of the present invention during depletion of RBCs;
[0093] FIG. 29 is a detail cross-sectional view of the valve system, standpipe, RBC collection chamber, and SC collection chamber of a preferred embodiment of the present invention during depletion of RBCs and GRNs;
[0094] FIG. 30 is a detail cross-sectional view of the valve system, standpipe, RBC collection chamber, and SC collection chamber of a preferred embodiment of the present invention after depletion of RBCs and GRNs;
[0095] FIG. 31 is a plot of the values measured by a 1.sup.st position emitter/receive pair of a preferred embodiment of the present invention during depletion of MNCs;
[0096] FIG. 32 is a detail cross-sectional view of the valve system, standpipe, RBC collection chamber, and SC collection chamber of a preferred embodiment of the present invention during depletion of MNCs and top-up with plasma;
[0097] FIG. 33 is a detail cross-sectional view of the funnel, valve system, standpipe, RBC collection chamber, and SC collection chamber of an alternative embodiment wherein centrifugation is stopped after depletion of the RBCs and GRNs;
[0098] FIG. 34 is a detail cross-sectional view of the funnel, valve system, standpipe, RBC collection chamber, and SC collection chamber of an alternative embodiment wherein centrifugation is stopped after depletion of the RBCs and GRNs and the entire cartridge is shaken so as to mix the remaining plasma, MNCs, and PLTs;
[0099] FIG. 35 is a detail cross-sectional view of the funnel, valve system, standpipe, RBC collection chamber, and SC collection chamber of an alternative embodiment wherein the cartridge is centrifuged a second time at lower G force and for less time so as to collect substantially all the MNCs but only a small portion of the PLTs;
[0100] FIG. 36 is a detail cross-sectional view of the funnel, valve system, standpipe, RBC collection chamber, and SC collection chamber of an alternative embodiment after centrifugation is stopped and MNCs, plasma, and a small portion of PLTs are collected in the SC harvest compartment;
[0101] FIG. 37 is a detail cross-sectional view of the funnel, valve system, standpipe, RBC collection chamber, and SC collection chamber of an alternative embodiment in which GRNs are desired in the SC harvest compartment; and
[0102] FIG. 38 is a perspective view of the cartridge of a preferred embodiment of the current invention showing the SC harvest tube and the RBC/GRN harvest tube.
DETAILED DESCRIPTION OF THE INVENTION
[0103] The following description is presented to enable a person of ordinary skill in the art to make and use various aspects and examples of the present invention. Descriptions of specific materials, techniques, and applications are provided only as examples. Various modifications to the examples described herein will be readily apparent to those of ordinary skill in the art, and the general principles defined herein may be applied to other examples and applications without departing from the spirit and scope of the invention. Thus, the present invention is not intended to be limited to the examples described and shown, but is to be accorded the scope consistent with the appended claims.
[0104] The applicant discloses a method and device for depleting RBCs from a blood sample and, in some circumstances, depleting a particular GRN, and, in other circumstances, PLTs. The preferred embodiment of the present invention accomplishes this substantial depletion through centrifugation so as to optimally isolate and then harvest WBCs including substantially all the SPCs.
[0105] Turning first to FIG. 15, the applicant's method and device 1 in a preferred embodiment comprises a rigid disposable cartridge 10, which may hold up to 250 mL of liquid, is cylindrical, single-use, and constructed preferably of hard plastic, and more preferably optically clear polycarbonate. The control module 40 in which the disposable cartridge 10 is seated is a battery operated, electro-mechanical device with optical and gravitational sensing. The preferred embodiment also comprises a membrane switch 41, a seven segment digital read out 42 and three light emitting diodes 43 to inform and assist the user. Shown on the left in FIG. 15 is a universal battery sign 44 that alerts the user to the charge condition of the battery. Shown in the center is an on-off switch 45 for the control module and an LED, and on the right is a digital read out 42 and an LED that indicates whether the cell harvest run was performed as designed and, if not, which error in operation may have occurred.
[0106] Turning to FIG. 16, an exploded view of the disposable cartridge 10 and the control module 40, as well as a standard 750 ml centrifuge cup 70 is shown according to the preferred embodiment of the invention. In operation the disposable cartridge 10 and the control module 40 are releasably locked together. The disposable cartridge comprises multiple compartments, one of which is the funnel or rigid chamber 11. Preferably, the centrifuge cup 70 houses the control module 40, which is intended for repeated use with and in connection with the sterile disposable cartridge 10 above it. The control module 40 and cartridge 10, in combination, preferably weigh approximately 450 grams. Among other components to be described later, the cartridge includes an inlet 12 at the top that serves as access for incoming fluid. This access may be connected to tubing which may proceed to a phlebotomy needle or a spike for connecting to a cell solution and may also be coupled to an inline filter that removes any clots that would otherwise jam other system components during the remaining processing steps. The top of the disposable cartridge may also contain a 0.2-micron filter 13 to provide passage for displaced air from within the funnel when blood or bone marrow is introduced into the funnel. The top of the cartridge may also comprise a means of sterile filtering (not shown) of the blood, bone marrow, or other fluids such as diluents, as they are introduced into funnel.
[0107] Turning to FIG. 17, the motor circuit board electronics 47, located within the lower control module 40 is shown. The electromechanical portion of the device preferably uses a rechargeable battery system to power a control module that monitors and controls gravitational and optical sensing equipment and directs activity in the disposable cartridge. The means for determining a G force may be any commonly known in the art, such as calculating said force through a measurement of centrifuge RPM, or through direct measurement of acceleration or force.
[0108] FIG. 18a shows a diagrammatic side view of the disposable cartridge 10 with labeled cross section A-A. FIG. 18b shows a perspective view of the disposable cartridge 10 cut along cross section A-A. As described in the process below, a biological fluid containing cells, such as normal blood, cord blood or bone marrow, is delivered to the large funnel-shaped compartment having an open end that is initially closed by a valve means (not shown). The cartridge comprises a large first rigid storage compartment or RBC depletion compartment 14 and the smaller second rigid storage compartment or SC compartment 15 into which the WBCs and substantially all the SPCs are transferred. The RBC depletion compartment 14 is significantly larger than the SC harvest compartment 15, as the volume of RBCs depleted from a blood sample is always much greater that the volume of WBCs collected. All compartments are distinct from one another, but contiguous with respect to airflow. The RBC depletion compartment 14 and the SC harvest compartment 15 are connected by small chimneys 29 to the original chamber so as to allow displacement of air as cell solutions move from the original chamber into the compartments.
[0109] Turning to FIG. 19, a perspective cross-sectional view of a disposable cartridge 10 with a narrow bottom of the funnel 11 is shown. The larger RBC depletion compartment 14 is seen in cross section on the left side of the funnel. As will be described in detail below, in operation, the RB Cs initially migrate towards the bottom of the funnel shaped primary compartment, moving radially outward away from the axis of rotation of the centrifuge until reaching the valve system 16 at the bottom of the device. Here, the pressure head of fluid above the valve system urges the fluid into one of two compartments. Which compartment the fluid is directed into is dependent upon the status (open, closed) of valves to those compartments. In either case, after passing through the valve system 16 at the bottom of the cartridge 10, the fluid flows generally toward the axis of rotation, urged by pressure from the of fluid (mostly plasma) remaining in the primary compartment. The fluid that has passed through the valve system is then retained in either the RBC depletion compartment 14 or the SC harvest compartment 15. Through minute adjustments of the valves, unwanted cell solutions may be depleted and desired cell solutions may be harvested.
[0110] Turning to FIG. 20, a preferred embodiment of the present invention is shown in use. As shown, 100 ml of cord blood is placed inside the main funnel shaped compartment 11. The operator then attached the cartridge 10 to the control module 40 (as shown in FIG. 21), and then loads the cartridge into a centrifuge, preferably a swinging bucket centrifuge, such as a Thermo Fisher Sorvall ST-40 tabletop centrifuge configured to accept four 750 ml cylindrical buckets. Alternative centrifuges may be used that provide for more or less than four cartridges to be centrifuged at once.
[0111] Turning to FIG. 21, a representation of what occurs when the cartridge 10 is subjected to high G forces is shown. Here, under an exemplary 2000 G centrifugation the RBCs begin to migrate down and the WBCs begin to migrate up from the bottom of the funnel and down from the top volume of the fluid to a position above the RBCs. Above the RBCs then, a very thin layer of WBCs and PLTs begins to stratify and above that a volume of plasma stratifies, the plasma is yellow in color. Under high G forces, the RBCs are increasingly squeezed together near the bottom of the processing funnel 11 with the heaviest of the RBCs lower and the lighter RBCs near the top of the RBC volume. It is noted that because during centrifugation the cartridge depicted in the figure is rotating about an axis perpendicular to and located above the cartridge as shown, the G force experienced by the cartridge increases proportionally to the distance from the axis of rotation and is roughly twice as high at the bottom of the centrifuge cup (2000 Gs) as at the top (1000 Gs).
[0112] Turning to FIG. 22, a detailed cut away side view of a preferred embodiment is shown. In this preferred embodiment the funnel 11 is kept separated from the RBC depletion compartment 14 and SC harvest compartment 15 by valve system 16. While many means of valve control are contemplated, in a preferred embodiment a pinch valve system is used, wherein eccentric cams 17 control tube pinchers 18 that ultimately direct flow of liquid from the bottom of the funnel to the cell depletion compartment 14 and to the cell harvest compartment 15. Here, the pinch valves comprise two opposing clamps having pinching surfaces approximately 0.088 inches wide, and require approximately 1.6 pounds of pinching force to block all fluid passage through a urethane tube with an inner diameter of 0.062 inches and an exterior diameter of 0.088 inches when the hydraulic pressure in the tube is at 325 PSI. Pinching forces in excess of 1.6 pounds may be required at greater pressures, and reduced pinching forces may be sufficient at lower pressures.
[0113] Turning to FIG. 23, a cantilever system to achieve these required pinching pressures is shown. The cantilever system 19 may open and close the valves (pinch and release the tubing) as needed. The springs 20 for each cantilever 21 are preferably located at the extreme end of the cantilever. The actuator overcomes the resistance of the springs to move the lever. Once the actuator stops applying force, the bias of the springs urges the lever back to its first position.
[0114] Turning to FIG. 24, a detailed view of the cam portion of the tube pinching or valve closing mechanism is shown. The cam converts rotational motion of a valve motor into a linear motion, which is used to close or pinch the tube. As disclosed above, a cantilever system may be employed in conjunction with the cam. As the cam 22 rotates approximately 90 degrees clockwise, the larger portion of the cam exerts a continuing clockwise torsional force on the rotor and motor due to the high gravitational field exerting a generally downward force across the entire device. The cam is specially designed to operate within an extremely high gravitational field. The cutout 23 shown and the counterweight 24 located on the opposite side of the cam allow the small motor to provide enough force to rotate the cam counterclockwise 90 degrees to its start position. The cam is thus specifically designed to not only reduce the amount of material off-axis and subjected to potentially immobilizing gravitational forces, but also to counter the weight of the remainder of the cam in light of such forces. That is, as the camshaft rotates about its central axis, this design assures there is no addition or subtraction of torque as a result of G forces acting on the cam.
[0115] FIG. 25 shows the relative size of the various cells relative to the connecting tubing or flexible conduit (the large outer circle) of an exemplary embodiment, which is located between the primary compartment 11 and either the RBC depletion compartment 14 or the SC harvest compartment 15. The tubing inner diameter in an exemplary embodiment is 0.062 inch (1.575 mm). Tubing of other inner and outer diameter may be employed, so long as complete cutoff of all cells and liquid is possible via a valve means. In an exemplary embodiment these flexible conduits have a ratio of length to diameter not exceeding 20.
[0116] Returning to the description of the exemplary process, FIG. 26 shows an exemplary cartridge after approximately 10 minutes of centrifugation at 2000 Gs. The buffy coat 2 stratifies at the interface between RBCs and plasma. The cells at the very bottom of the funnel 11 may reach an HCT (hematocrit, the proportion of blood volume occupied by red blood cells) approaching 90, but towards the top of the RBC layer the HCT may be only 60-70, due to the lower centrifugation force at that distance from the axis of rotation and the wide area of the funnel at that location.
[0117] Turning to FIG. 27, a detailed view of the narrow region of the funnel 11 is shown. When the disposable cartridge 10 is attached to the control module 40, in this narrow region of the primary compartment are at least one but preferably two or more optical or other sensors 48 that detect the type of cells flowing through that portion of the processing funnel. In this narrow region of the primary compartment are also at least one but preferably two or more optical or other emitters 49. In an exemplary embodiment shown four infrared emitters/detector pairs are arranged vertically. In a preferred embodiment infrared sensors are located directly across from paired infrared emitters. In second preferred embodiment, transmitters that provide wavelengths that are preferentially absorbed by red cells are located directly across from paired sensors sensitive to that frequency. In a third preferred embodiment sensors are utilized that identify cells that have absorbed fluorescent dyes. In the first preferred embodiment, the presence of cells interferes with the emitted infrared light and the infrared light detector quantifies the amplitude of the signal penetrating the fluid. In a preferred embodiment the sensors may assign the level of transmission a value from 0-1000. Pure plasma, which similar to water blocks none of the infrared light, will register a value of roughly 1000. As compacted RBCs pass, essentially all infrared light is blocked and the detector registers a value of 0.
[0118] Turning to FIG. 28, the next step in the process is shown. After a sample has been centrifuged for a set amount of time (20 minutes in an exemplary embodiment), the centrifuge may slow to a speed that creates 100 Gs at the bottom of the centrifuge bucket (that is, farthest from the axis of rotation). An on-board accelerometer may track the G-force throughout the process. Once the accelerometer detects that the centrifuge has arrived at 100 Gs, the device waits a set amount of time (in order to ensure the centrifuge has settled at 100 Gs and is not passing through to some lower G-force, such if the machine had malfunctioned or lost partial power), and then a first valve 25 connecting the primary compartment 11 with the RBC depletion compartment 14 opens, allowing passage of highly concentrated RBCs and some plasma. RBCs can be seen entering the depletion compartment 14 by initially filling the standpipe 26 (which preferably has a volume of 1 mL, as will be described below). During use, the RBCs will continue to flow to depletion compartment 14 until the standpipe 26 is full, at which time the RBCs will overflow and fill the larger section of the depletion compartment 14.
[0119] FIG. 29 shows the standpipe 26 overflowing and the RBCs filling the larger depletion chamber. The interface between RBCs and plasma, delineated by the buffy coat 2, is now readily apparent. As the funnel 11 narrows, the same volume of cells must occupy less horizontal space. As a consequence, the vertical space occupied increases and it becomes easier to distinguish each stratified layer of cell types.
[0120] Turning to FIG. 30, the WBCs entering the narrow portion of the funnel 11 is shown. As the WBCs enter this narrower portion, their stratification continues, with the GRNs on the bottom (not labeled), MNCs 3 in the middle, and PLTs 4 resting on top of the MNCs. The bulk of the plasma 5 in is shown above the PLTs.
[0121] The emitter/detector pairs, as shown in FIG. 27, monitor the passage of the cells through the narrow region of the primary compartment. FIG. 31 shows the infrared optical counts of blood cell populations during the 100 G transit from the 1.sup.st position (topmost) emitter/detector pair. The horizontal line represents the optical count observed in cell-free plasma. Lower optical counts signify that WBCs and PTLs are still present in the sample being observed by the emitted/detector pair. The initial rise from 0 at the bottom left of the graph indicates when the buffy coat layer disposed above the RBCs passes the 1.sup.st position emitter/detector pair. The rising value indicates the solution passing between the emitter/detector pairs is becoming clearer, meaning it comprises fewer RBCs. As the clearer layers approach, the value increases, for instance to 50, then 100, 200 and so on.
[0122] Under some circumstances the optical count values that are shown in FIG. 31 as rising while cells are depleted, may, when the depletion is halted, begin to fall, indicating that more cells are entering the sensing area. The reasons for this are complex. First, the optical measurements are being taken through a fluid which experiences turbulence and eddies as particles of varying densities are reorganized as they are evacuated through the bottom of a funnel of decreasing radius. RBCs and WBCs fall at differing rates due to their differing sizes. Consequently, if the rate of evacuation of the RBCs is greater than the sedimentation rate for certain particles (such as the PLTs, small in size relative to the others), then those particles will lag behind other particles having faster sedimentation rates. The carefully stratified mixture becomes partially mixed during the evacuation process. Not only do the RBCs fall at one rate while the WBCs fall at a different rate, but also the motion of the WBCs may be inhibited by the motion of the vastly more numerous RBCs. Further, the density of RBCs changes throughout their lifecycle. Consequently, the lighter RBCs will rise with the displaced plasma as the more dense RBCs pack into the bottom of the funnel. Thus the WBCs that began at the bottom of the funnel and which rose towards the RBC/plasma interface are accompanied by the much more numerous lighter RBCs. These ascending cells maneuver around the descending dense RBCs due to the fact that all cells possess a slightly negative charge and so tend to repel one another.
[0123] To counter this mixing that inevitably occurs during depletion, the an exemplary embodiment of the system, after evacuating for a set time closes the tubing through which the cells are passing and allows the descending cells to re-compact and re-stratify. Upon reopening the tubing, mixing begins to occur again within the funnel. The present invention is thus able to employ a start-stop approach that periodically halts the evacuation process, should this mixing not be suitable for a given application.
[0124] Turning to FIG. 32, a latter point in the process is shown. At a certain point in the process the tube to the RBC depletion compartment 14 is closed, and the tube to the SC harvesting compartment 15 is opened. FIG. 32 depicts a later time in the process wherein the pathway to the SC harvest compartment 15 has been opened and the pathway to the RBC depletion compartment pinched shut. Because the RBC depletion compartment standpipe 26 holds the final 1 mL of RBCs to enter the RBC depletion compartment 15, the standpipe 26 contains the least dense of the RBCs, and hence a greater concentration of GRNs and NRBCs than does the RBC depletion compartment 15 as a whole. A technician may later recover the contents of the standpipe 26 and thus obtain GRNs and NRBCs for HLA typing without sacrificing the recovery of SPCs from the smaller SC compartment 15. As centrifugation continues, cells of greater density continue to be urged away from the axis of rotation. The plasma 5 remaining in the primary compartment continues to exert pressure on the fluid and cells beneath it, and drives the MNCs 3, and PLTs 4 up the tube leading to the SC harvest compartment 15. As shown, even after the MNCs and PLTs are largely removed from the primary compartment, plasma 5 is allowed to then flow into the SC harvest compartment 15, washing the connecting tube in the process and assuring that all SPCs are collected in the harvest compartment 15.
[0125] The timing for controlling the valve system 16 so fluid (and cells) are directed to the SC harvest compartment 15 as opposed to the RBC depletion compartment 14 is critical. If the valves are switched too early, RBCs may enter the SC harvest compartment 15, raising the HCT and decreasing the purity of the sample collected. If the valves are switched too late, some of the MNCs may move to the RBC depletion compartment 14, thereby reducing the recovery of the MNCs and SPCs harvested.
[0126] One difficulty present in the prior art that is overcome by an exemplary embodiment of the present invention is the challenge of collecting a predetermined final volume of liquid transferred during centrifugation. This is important for example because various other types of equipment in which it is anticipated blood samples from the current invention will be used are configured to accept a predetermined volume of liquid, such as 20 mL. Although detecting when a certain volume of fluid has been collected during centrifugation is possible with specialized scales measuring the weight of the fluid collected, for reliability purposes a solid-state solution is preferred. To determine the volume of liquid passing through to the SC harvest compartment certain assumptions are required. First, it is known that the fluid above the cells passing through the sensor region of the main compartment is creating downward pressure on those cells and prompting their evacuation through the bottom of the funnel. As the liquid continues to be evacuated under constant acceleration, the rate of evacuation slows because there is less pressure on those cells due to the decreasing volume of plasma above them. It is also known that although cell viscosity may vary from hematocrit to hematocrit and person to person, plasma is adequately consistent with regard to viscosity. Consequently, once all the target cells have passed and only plasma remains to be transferred through the tubing to the SC compartment it will flow at a predictable rate proportionate to the dynamic head of plasma above it.
[0127] In the present invention, the above facts are coupled with a method that employs the multiple emitter/detector pairs passed by the evacuated cells. For instance, as the buffy coat approaches the top sensor, the optical count detected by the top, or 1.sup.st position emitter/detector pair, will begin to rise, as described above. An arbitrary optical count value (in this case 4) is predetermined and a timestamp is initiated when the 1.sup.st position emitter/detector pair detects that arbitrary value. As evacuation continues, a second timestamp is set when the 2.sup.nd position emitter/detector pair (that is, the pair just under the topmost pair) reads that same arbitrary value. Through calculations that take into account the distance between the 1.sup.st position and 2.sup.nd position emitter/detector pairs, and the time taken for the arbitrary value to reach the 2.sup.nd position, the velocity of blood component flow between the two pairs of sensors may be determined. The same process may be employed to determine the amount of time it takes any arbitrary value to pass from one sensor to any other sensor located beneath it.
[0128] With a further understanding of the volume of blood between sensors, a rate of volume depletion may be calculated. For instance, it is known that in one embodiment of the present invention the volume in the bottom tip of the funnel below the 1.sup.st position sensor is 6 mL, while the volume below the second position sensor is 4 mL. The rate of flow can thus be calculated based on the understanding that between the first time stamp and the second time stamp, 2 mL of blood is evacuated. The rate may be further refined by detecting when the 3.sup.rd position and 4.sup.th position (lowest) emitted/detector pair read that same arbitrary value. Importantly, during this process, the aforementioned start-stop technique is taking place and the effect of full valve closure on the rate of evacuation is noted. In conclusion, through extrapolation based on an observed rate of flow through stacked emitter/detector pairs, a limit can be set on the time that the valve to the SC harvest compartment is open as the solution of WBCs including the SPCs is topped up with plasma to a desired volume. The limit varies dependent on the rate of flow, which ultimately is predominately dependent on the pressure caused by the head of liquid above the evacuation point and, to some extent by the viscosity of the plasma that is used to top up the stem cell solution to a predetermined final volume.
[0129] In alternative embodiments of the invention RBCs may be collected at higher or lower accelerations then the currently chosen 100 G, for instance in a gravitational field of 50 to 200 Gs.
[0130] An alternative embodiment of the invention comprises a method to significantly reduce the number of PLTs 4 which are collected with the MNCs 5.
[0131] As is shown in FIG. 33, during the centrifugation process the MNCs 3 and platelets 4 concentrate at the bottom narrow portion of the primary compartment 11. At this point in the process, if the pinch valve to the SC harvest compartment 15 were opened, then the MNCs would be urged by the mass of plasma in a direction first perpendicular to the axis of rotation and then up the right side tube towards the axis of rotation and into the SC harvest compartment 15. Without additional steps taken, the plasma would subsequently force the PLTs into the SC harvest compartment until they were depleted at which time the flow of plasma would top up the SC harvest compartment.
[0132] To reduce the number of PLTs that enter the SC harvest compartment 15, the technician may program the control module to pause the harvest process at the end of the RBC/GRN depletion cycle (by closing the RBC valve and not opening the MNC valve) and allow the centrifuge to come to a stop. In this method, the technician then removes the cartridge from the centrifuge bucket and gently rocks the cartridge in order to redistribute MNCs 3 and PLTs 4 throughout the plasma 5 in the funnel, dispersing them as depicted in FIG. 34.
[0133] As shown in FIG. 35, the cartridge is then centrifuged for a smaller amount of time and at a lower acceleration. The smaller amount of time and lower acceleration is sufficient to cause the denser and faster moving MNCs 3 to reconcentrate at the bottom of the funnel, but not enough to cause the PLTs to do the same. The PLTs are of lower density and size, and thus require more time to migrate to the bottom of the funnel. By not providing that time, the majority of the MNCs can be separated from the majority of the PLTs as shown.
[0134] Turning to FIG. 36, when the pinch valve to the SC harvest compartment 15 is then opened, the MNCs 3 flow first, followed by plasma 5 and a small fraction of PLTs 4 and then the SC harvest tubing is pinched closed. While some PLTs still make it into the SC harvest compartment, the fraction is proportional to the volume of plasma that was transferred into the SC harvest compartment compared to the total volume of plasma in the disposable cartridge. For example a 100 ml volume of blood would typically contain about 55 ml of plasma. If 5 ml of plasma were transferred to the SC harvest compartment, leaving 50 ml of plasma behind in the primary compartment, then the proportion of PLTs with the MNCs would be about 10% of the total PLTsconstituting a roughly 90% reduction of PLTs in the MNC harvest.
[0135] Turning to FIG. 37, another alternative embodiment is illustrated. In this alternative embodiment of the invention, GRNs 6 may be desired in the SC harvest compartment 15. For instance, in the collection of cord blood, the total WBC count often determines which of two cord blood units equally matched to the patient is chosen. Therefore it may be desired to include the majority of GRNs with the MNCs. To obtain this result, the technician may program the control module to open the valve to the SC harvest compartment earlier than in the other (above disclosed) embodiments, thereby allowing the top layer of RBCs (comprising many of the GRNs) into the harvest compartment. It should be readily apparent that through adjustments in timing, varying amounts of GRNs may be allowed into the SC harvest compartment. The sample collected in the harvest compartment is subsequently topped off with plasma so that the sample retains a relatively low (approximately 2-10% hematocrit).
[0136] Turning to FIG. 38, in any of the above embodiments, mechanisms are in place for removing the contents of the SC harvest compartment as well as the standpipe which contains the last 1 mL of RBCs transferred to the RBC compartment. FIG. 38 shows the disposable cartridge with both the SC harvest tube 27 and the RBC/GRN harvest tube 28 deployed for collection. The RBC/GRN harvest tube connects to the exterior of the cartridge by any means known in the art, and creates a fluid connection with the bottom of the standpipe, thereby providing a simple means to retrieve NRBCs and GRNs from the last 1 mL of the cell solution for sampling, such as obtaining human leukocyte antigen (HLA) typing, and then the remainder of the RBC/GRNs can also be removed, as required.
[0137] In any embodiment of the present invention, it is to be understood that antibody beads, either bouyant in plasma or approximately as dense as RBCs, may be introduced to the sample prior to harvesting to bind to cells known to not be useful for a specific research or clinical purpose.
[0138] In any embodiment of the present invention, it should be readily understood that fluorescent material absorbable by certain cell populations may be introduced to the sample prior to harvesting to allow tracking of said cell populations through the harvesting process and thereafter.
[0139] Although the invention has been shown and described with respect to certain embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of the specification. In particular, with regard to the various functions performed by the above-described components, the terms (including any reference to a means) used to describe such components are intended to correspond, unless otherwise indicated, to any component which performs the specified function of the described component (e.g., that is functionally equivalent) even though not structurally equivalent to the disclosed component which performs the functions in the herein exemplary embodiments of the invention. In addition, while a particular feature of the invention may have been disclosed with respect to only one embodiment, such feature may be combined with one or more other features of other embodiments as may be desired or advantageous for any given or particular application.
