Abstract:
An automated blood separation method and apparatus is described that allows for the separation of multiple units of blood simultaneously. The method and apparatus reliably and quickly separates blood into its components. An auto-balancing feature within the apparatus automatically preferably compensates for the changing state of imbalance, thereby eliminating the need for additional balancing steps during the separation process. The apparatus has a rotor into which a plurality of cassettes can be inserted. The cassettes have a number of sections for the containment of the whole blood and for the separated blood components, which are contained in disposable bags. The rotor is placed into a centrifuge assembly, and the blood components are then separated and transferred to the bags in the individual sections of the cassettes. Means for including secondary separation devices such as filters is included. The manufacturing information regarding the lot identities used and the conditions under which each unit was processed is also included.

Description:
[0001]    The present application claims the benefit of U.S. provisional application number 60/212,865, filed on Jun. 20, 2000, incorporated herein by reference in its entirety. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to methods and apparatus for the separation of one or more cell fractions from their suspending fluid and/or the resuspension of cells in fresh suspending fluid media. More particularly, the invention relates to automated methods and apparatus that allow for the separation of multiple units of blood simultaneously where the red blood cells and platelet cells are separated from the plasma, the red blood cells are subsequently resuspended in a storage solution, and the platelets are suspended in a concentrating volume of plasma. The method and apparatus dramatically decrease the labor and time required to separate blood into its components and simplifies the data retention required to validate the processing parameters for each unit of blood as required by the evolving FDA regulations governing the safety of the nation&#39;s blood supply. Other embodiments of the invention include in-line filter elements that remove contaminating cells, called leukocytes, which are believed to be responsible for a variety of adverse reactions by the recipient of the blood components. Similarly, other types of filters and packed columns positioned in-line with the flow of these blood components can remove viruses, bacteria or other contaminants which further enhances the purity and safety of the blood components.  
         BACKGROUND OF THE INVENTION  
         [0003]    Approximately 12 million units of blood are collected annually in the United States. Another 8 million are collected in the rest of the world. Each donated unit of blood is referred to as “whole blood.” Whole blood contains red blood cells, white blood cells and platelets suspended in a proteinaceous fluid called plasma. Because patients often do not require all of the components of whole blood, most units of whole blood are separated into their multiple components. Individual components are then transfused to different individuals with different needs, a practice referred to as “blood component therapy”.  
           [0004]    Red blood cells carry oxygen and usually are used to treat patients with anemia. For example, patients with chronic anemia resulting from disorders such as kidney failure, malignancies, or gastrointestinal bleeding and those with acute blood loss resulting from trauma or surgery. White blood cells are responsible for protecting the body from invasion by foreign substances such as bacteria, fungi and viruses.  
           [0005]    Plasma contains albumin, fibrinogen, globulins and other clotting proteins. Albumin is a chief protein constituent, fibrinogen plays an important role in the clotting of blood and globulins include antibodies. Thus, plasma serves many functions, including maintenance of satisfactory blood pressures and volume, the control of bleeding by blood clotting, immunity and maintenance of a proper balance of vital minerals in the body. Plasma typically is transfused to control bleeding due to low levels of some clotting factors or it may be transfused to expand the volume of circulating blood. Plasma also may be further fractionated to derive its component proteins.  
           [0006]    Platelets help the clotting process by sticking to the lining of blood vessels. Platelets are generally used to improve wound healing and stop bleeding, for example, in patients with leukemia and other forms of cancer.  
           [0007]    Cryoprecipitated Antihemophilic Factor (AHF) is rich in certain clotting factors, including Factor VIII, fibrinogen, von Willebrand factor and Factor XIII. It is used to prevent or control bleeding in individuals with hemophilia and von Willebrand&#39;s disease, which are common, inherited major coagulation abnormalities.  
           [0008]    Whole blood will separate into its components if treated to prevent clotting and permitted to stand in a container. The red blood cells, weighing the most, will settle to the bottom, the plasma will stay on top, and the white blood cells and platelets will remain suspended between the plasma and the red blood cells. Typically, a centrifuge process is used to speed up this separation.  
           [0009]    A common centrifuge process is described in the AABB Technical Manual, methods 9.4 and 9.11 as follows: Typically, the bag of whole blood is carefully loaded into one of the buckets of a large swinging bucket centrifuge. The opposing buckets are weighed and balanced so that their weight is within a few grams. Then, the buckets are loaded into a rotor and the rotor spun at conditions called “light spin” by the blood banking community (2000 g for 3 min).  
           [0010]    After a considerable wait for the centrifuge to slowly decelerate to zero speed, each bucket is very carefully removed from the rotor so that the bags can be removed from the buckets. This delicate operation must be done in a way that does not disturb or in any way re-suspend the cells. The bag is placed between the two expressing plates of a plasma extractor which force the platelet-rich plasma (PRP) from the whole blood bag to the platelet storage bag. A bag of nutrient solution then is emptied into the packaged red cell bag which is, in turn, placed in storage. The platelet-rich plasma (PRP) can be used to prepare platelets and plasma or Cryoprecipitated AHF.  
           [0011]    To make platelets, the platelet-rich plasma (PRP) bags again are balanced and then placed back in the centrifuge for a “heavy spin” (5000 g for 5 minutes) causing the platelets to settle at the bottom of the bag. Plasma and platelets then are separated and made available for transfusion. A plasma extractor generally is used to remove all but 50 to 70 ml of plasma, which is required to maintain viability of the platelets. The plasma also may be pooled with plasma from other donors and further processed, or fractionated to provide purified plasma proteins such as albumin, immunoglobulin and clotting factors. Cryoprecipitated AHF may be made from fresh frozen plasma by freezing and then slowly thawing the plasma.  
           [0012]    In each case, the components must each be identified in inventory by a method that allows for the traceablilty of that component back to the test results for the original donor, the donated unit, the disposable set in which it was collected, the centrifuge in which it was processed, and, if applicable, the leuko-filter that was used. This traceability is required by law.  
           [0013]    Although the centrifuge process speeds up separation of the whole blood into its components, the process is labor intensive and prone to errors and even the most sophisticated inventory control system is subject to the possibility of error as hundreds of data entries are input manually for each unit.  
           [0014]    A method and apparatus for the separation of whole blood that is quick, easy and less prone to errors still is needed.  
         SUMMARY OF THE PRESENT INVENTION  
         [0015]    The present invention provides an improved method and apparatus for the separation of whole blood into its components. The method and apparatus automates the separation process, thereby dramatically reducing the labor involved in conventional separation of whole blood. Further, the method and apparatus allows for the separation of multiple units simultaneously, thereby dramatically reducing separation time.  
           [0016]    In a preferred embodiment of the present invention, the apparatus includes a centrifuge designed for holding, on a hollow central drive shaft, a plurality of circular cassettes stacked in a co-axial configuration. Each circular cassette has a plurality of caveties for holding a plurality of bags, e.g. a whole blood bag and blood component bags including, for example, a red blood cell bag, a platelet concentrate bag and a platelet poor plasma bag. The cassettes may include further caveties for holding additional components such as filters, other storage bags and an expressor chamber or expressor bag. The various bags are in fluid communication with each other by, for example, tubing or the like to allow transfer of components from one bag to the other. The co-axial configuration is advantageous in that it is self-balancing as the components move from one compartment to another.  
           [0017]    Preferably, the whole blood bag and blood component bags are fabricated of a material that allows them to expand and contract repeatedly to move fluids between the cavities, such as a flexible or an elastomeric material. The number of blood component bags, like the number of cavities, is not limited. The bags for holding the whole blood and blood components are sterile bags fabricated of materials that are of the kind generally approved and accepted for that purpose. Preferably, these bags are shaped to fit the shape of the cassette caveties into which they are placed. Valves and sensors are preferably included to detect and control the flow of the components into the appropriate blood component bag.  
           [0018]    In one embodiment, two different types of valves are used. First, an electronically driven solenoid valve can be used to stop the flow of plasma from being espressed from the whole blood bag as soon as red cells are optically detected in that stream, thereby signaling the end of the expression step. Both the optic detector and the solenoid valve can be controlled by a microprocessor-based logic controller, preferably co-located in the hollow central drive shaft. Power for the optic detector and the solenoid valve can be fed into the rotating housing through a set of concentric slip rings. There is a practical limit on the number of separate power and signal lines that can be fed into the cassette. Therefore, a second type of valve is preferably used that does not require either power or signal communication to the controllers outside the rotating field. This second type of valve could be a centrifugally actuated valve that would open and close based on the speed of the rotor.  
           [0019]    In a preferred embodiment, the stacked co-axial configuration operates as follows: a unit of whole blood is collected in a sterile whole blood bag. This whole blood bag is then connected to a sterile bag set via a sterile connection device. This bag set consists of the bags, tubing, and solutions necessary to separate the unit of whole blood into the desired components. These bags are then positioned in the cassettes in the appropriate cavities. The cassettes are closed and loaded into the centrifuge. Under centrifugal force, the red blood cells sediment radially outward in the whole blood bag. After complete sedimentation, expressor fluid or gas is pumped into the expressor chamber or bag, thereby expanding the flexible membrane or bag that contacts the whole blood bag, which compresses the whole blood bag and forces the supernatant fluid (platelet rich plasma) through the platelet concentrate bag and into the platelet poor plasma collection bag. The expressor fluid or gas can have a density higher than that of blood or lower, including air or other suitable gases. During the routing through the platelet concentrate bag, the platelets sediment to the outer surface of the bag and are collected. This expression continues until all of the supernatant has been expressed from the whole blood bag and an optical sensor detects the presence of red blood cells in the plasma stream. The valves are then closed and the expressor pump stopped. The centrifuge is then stopped and the cassette removed and opened. The bags can then be separated and placed in the appropriate storage containers.  
           [0020]    In alternate embodiments, filters or columns are positioned in-line between the product bags in a manner that allows for the removal of target cells as they move from one bag to another. These embodiments would preferably use an additional expression step. One example of an additional expression step includes expressing the packed red blood cell mass through a leukodepleting filter or column to a storage bag containing the appropriate storage solution. Another example includes expressing the storage solution in the red cell mass to dilute the cells before expressing the mixture through the leukodepleting filter. Yet another example includes using a column to collect CD-34 stem cells from the plasma stream as it is being expressed from the collect bag to the plasma bag. Another example includes passing the red cells through a column to remove residual processing chemicals, for example, glycerol which is used for cryopreservation. Although can be advantageous to include these secondary separation steps with the basic separation of the cells, it may result in unacceptably long processing times in some cases. Thus, in some embodiments, the secondary separation step takes place outside the centrifuge. Preferably, where the secondary separation step occurs outside the centrifuge, the device further includes a built-in refrigerated chamber for controlling the temperature of the cells during the filtering process.  
           [0021]    In some embodiments, other fluids, such as sucrose-based storage solutions that are commonly added to separated blood components, are included in the device through the addition of extra bags and cavities. These bags containing, for example, storage solutions, are in fluid communication with the appropriate blood component bag(s) such that, for example, after the blood components have been separated and collected in the appropriate blood component bag(s), the storage solution can be added to the appropriate blood component bag(s). The number of bags and cavities is limited only by the space available in the centrifuge and the space for flow streams within the cassette.  
           [0022]    In accordance with another embodiment of the present invention, a radial segment configuration is utilized. In this configuration, a large rotating drum (“rotor”) is divided into pie-shaped segments, each housing a removable cassette comprised of multiple sections. A bag containing the whole blood is placed in one section of the cassette. The remaining sections of the cassette are used for the containment of the separated blood components. For example, in one embodiment, the cassette consists of three segments wherein the inner segment contains a first expresser chamber, the middle segment contains both a second expressor chamber and a whole blood bag and the outer segment contains a platelet collection bag. A final plasma collection bag can be positioned on an inside surface of the inner segment. Preferably, a pumping device is used to assist in moving fluid and components from one bag to another.  
           [0023]    Preferably, an auto-balancing mechanism, which automatically compensates for the changing state of imbalance of the rotor, is connected to the rotor, thereby eliminating the need for additional balancing steps during the separation process.  
           [0024]    In yet another embodiment, the bag arrangements presented previously are shaped to fit into a large swinging-bucket rotor. Swinging-bucket rotors have become common in blood component labs and, thus, this configuration would appeal to the market because labs could use the existing installed base of centrifuges for the process and apparatus of the present invention. Of course, modifications would be required to both the rotor and the machine to allow for expressing fluid to enter the bucket and to position valves and optic detectors on the rotor.  
           [0025]    Both the radial configuration and the swinging bucket configuration are used in a manner similar to that described above relating to the stacked disk configuration. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]    [0026]FIG. 1 is a schematic illustration of the separation activities in accordance with one embodiment of the present invention.  
         [0027]    [0027]FIG. 2 is an artists rendering of one embodiment of the separation system in accordance with the present invention.  
         [0028]    [0028]FIG. 3 is rendering of a typical cassette for the stacked-disk configuration in accordance with one embodiment of the present invention.  
         [0029]    [0029]FIG. 4 is a sketch of the fluid management components housed inside the drive shaft in accordance with one embodiment of the present invention.  
         [0030]    [0030]FIG. 5 is a rendering of the optional processing packs that can be used in the stacked disk configuration in accordance with one embodiment of the present invention.  
         [0031]    [0031]FIG. 6 is the cassette of FIG. 3 including the mechanical components from FIG. 4.  
         [0032]    [0032]FIG. 7 is a rendering of the expressor chamber inside the drive shaft in accordance with one embodiment of the present invention.  
         [0033]    [0033]FIG. 8 is a rendering of the self balancing feature of the stacked disk in accordance with one embodiment of the present invention.  
         [0034]    [0034]FIG. 9 is a second embodiment of the stacked disk in accordance with the present invention.  
         [0035]    [0035]FIG. 10 is a third embodiment of the stacked disk in accordance with the present invention.  
         [0036]    [0036]FIG. 11 is a sketch of the alternative means for pumping fluids into the cassette in accordance with one embodiment of the present invention.  
         [0037]    [0037]FIG. 12 is a sketch of the radial configuration in accordance with one embodiment of the present invention.  
         [0038]    [0038]FIG. 13 is a sketch of the closed cassette for the radial configuration in accordance with one embodiment of the present invention.  
         [0039]    [0039]FIG. 14 is a sketch of the open cassette for the radial configuration in accordance with one embodiment of the present invention.  
         [0040]    [0040]FIG. 15 is a sketch of the bag set used in the radial configuration in accordance with one embodiment of the present invention.  
         [0041]    [0041]FIG. 16 is a sketch of the bag set from FIG. 15 positioned in the cassette of FIG. 14.  
         [0042]    [0042]FIG. 17 is a sketch of section  5 - 5  through the cassette in FIG. 16  
         [0043]    [0043]FIG. 18 is a sketch of the self-balancing mechanism for the radial configuration in accordance with one embodiment of the present invention.  
         [0044]    [0044]FIG. 19 is a sketch of the swinging bucket configuration in accordance with one embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0045]    Referring now to the various figures of the drawing, wherein like reference characters refer to like parts, there is shown various views of an automated blood fractionation device and methods of utilizing the automated blood fractionation device, in accordance with the invention. The automated blood fractionation device of the present invention separates whole blood into it three primary components, red blood cells, platelets, and plasma. These components are separated and transferred into various blood component bags through sealed lengths of tubing or a similar mechanism that interconnect the various blood bags.  
         [0046]    During use of the device, a volume of whole blood is collected and placed into the device. In general, for example, with reference to FIG. 1, the collected whole blood is fed into the whole blood bag  6 , which is then placed into the device. The device holding the whole blood bag  6  is then is spun at high speeds to separate the red cells from the plasma. Meanwhile, the spinning whole blood bag  6  is preferably compressed in a way that allows the plasma to move from the whole blood bag  6  to the platelet concentrate bag  8  through tubing that interconnects the whole blood bag  6  and the platelet concentrate bag  8 . After filling the platelet concentrate bag  8 , the plasma continues to move toward the platelet poor plasma bag  9 . The plasma contains a second cellular component, called platelets. As the platelet rich plasma flows through the platelet concentrate bag  8 , the platelets sediment radially and collect on the outermost wall, while the platelet poor plasma continues to and fills the plasma bag  9 . This continues until all of the platelet-rich-plasma in the whole blood bad  6  has been squeezed out, or “expressed”, from the whole blood bag  6 . When this occurs, red blood cells then begin to move out of the whole blood bag  6  until an optic detector  20  senses a color or turbidity shift (or both) and signals valve  21  to close and valve  22  to open. Then, as the expressing fluid or gas continues to squeeze the contents out of the whole blood bag  6 , which now contains only red blood cells, these red blood cells flow into the red blood cell bag  7  until all have been expressed from the whole blood bag  6 . In red blood cell bag  7 , the red blood cells are preferably mixed with a fixed amount of storage solution that is pre-charged into the red blood cell bag  7 . Alternatively, rather than adding storage solution to the red blood cell bag  7 , the storage solution may be added to the red blood cells in the whole blood bag  6 . By adding the storage solution to the whole blood bag  6 , the hematocrit, and, therefore, the viscosity of the packed red blood cells is reduced, thereby making pumping of the red blood cells from the whole blood bag  6  to the red blood cell bag  7  less difficult.  
         [0047]    The above-described process can also be carried out as an ongoing procedure while the whole blood is being pumped into the whole blood bag  6  from an external source through, for example, a set of rotating face seals of an Adams-type skip rope. Further, although described with reference to FIG. 1, which contains a whole blood bag  6 , red blood cell bag  7 , platelet concentrate bag  8  and platelet poor plasma bag  9 , not all of these bags are required for each process, multiple types of bags may be used, and additional, different bags than those described may be included.  
         [0048]    As shown in FIG. 2, an automated blood fractionation device in accord with one embodiment of the present invention has a stacked co-axial configuration. In this configuration, a plurality of circular cassettes  1  are stacked in a co-axial configuration and placed over a drive shaft  2  within a centrifuge  3 , which is designed to accommodate the cassettes  1 . This configuration is advantageous in that each cassette  1  is self-balancing irrespective of the difference in the displaced mass during the expression steps of several cassettes  1  simultaneously.  
         [0049]    In one embodiment, the circular cassettes  1  are constructed as shown in FIG. 3, so as to form a plurality of cavities that can be loaded with the whole blood bag  6  and the various blood component bags. For example, as shown in FIG. 3, the various blood component bags may include a red blood cell bag  7 , a platelet concentrate bag  8 , and plasma bag  9 . Other cavities, such as cavity  10 , may be included for yet undefined requirements, such as, for example, holding storage solution that is added to the packed red blood cells and, for example, for holding an expresser chamber or an expressor bag as described in further detail below. Yet other cavities may be positioned to hold filters  12  and  13  (e.g. leukodepleting filters) and separation columns. The cavities can be structured and configured such as those shown in the Figures or in any other manner to permit the various blood bags or other flexible containers to be placed into and removed from the cavities.  
         [0050]    As shown in FIGS. 3 and 6, the blood component bags are in fluid communication with eachother with interconnecting tubing  14 , or the like. The tubing  14  is preferably positioned in recesses formed (e.g. molded) into the cassette in order to route the tubing  14  between cavities and secure the tubing against the centrifugal force to prevent collapsing or crimping of the tubing walls. A vertical section  15  of the tubing, shown in FIGS. 3 and 6, is preferably positioned in the cassette  1  so that it is visible from outside the closed cassette  1 . Means for detecting when the fractionation process is complete and a means for closing the interconnection between blood component bags also can be located within the device. For example, as shown in FIGS. 4 and 6, an optic detector  20  can be used which senses the presence of red cells in the supernatant line of the tubing and signals a valve  21  to close and the pump (not shown) to stop. This will prevent contamination of the platelet and plasma in bags  9 ,  8  with red blood cells. Then, valve  22  can be opened and expression can resume to move the red blood cells from the whole blood bag  6  through the tubing  14  and into the red blood cell bag  7 .  
         [0051]    As shown in FIG. 3, the cassettes  1  preferably further include an expressor chamber  23 . The expresser chamber  23  is sealed off by a flexible membrane  11 . The expressor chamber  23  and flexible membrane are preferably positioned in the cassette  1  adjacent to the portion of the cassette  1  that holds the whole blood bag and blood component bags. For example, as shown in FIG. 3, the cassette  1  may be formed of two separable portions, one of which holds the various blood component bags and the other of which holds the expressor chamber  23 . In one embodiment, shown in FIGS. 3 and 6, a top portion  17  is attached to a bottom portion  18  with a fastening mechanism  19 , such as a hinge or threaded surfaces along the circumference of the top portion  17  and bottom portion  18 , such that the cassette  1  may be opened to expose the inside of the cassette  1 . When the cassette  1  is closed, and the device is used, expressing fluid or gas is pumped into the expressor chamber  23  for the purpose of expanding the flexible membrane  11 , which pressurizes one or more of the blood component bags. Preferably, when the cassette  1  is closed, the flexible membrane sealing the expressor chamber  23  is in wall-to-wall contact with one or more of the blood component bags. The expressor chamber  23  has a fixed volume such that, as expressing fluid (liquid or gas) is pumped into the expressor chamber  23 , the flexible membrane  11  expands against, for example, the whole blood bag  6 , thereby squeezing and reducing the volume of the bag  6  and forcing material out of the bag  6 . The expressor chamber  23  is supplied with expressor fluid or gas from an external source, preferably through inlet/outlet port  16 . Pumping means [not shown] can be located either within the cassette  1  or outside the cassette  1  to further aid in moving materials from one blood bag to another.  
         [0052]    In a particularly preferred embodiment, the expressor chamber  23  is positioned such that the flexible membrane  11  is in wall-to-wall contact with the whole blood bag  6 . As the centrifuge spins the cassettes  1  at high speeds, the red blood cells are separated from the plasma. Once the separation has occurred, expressor fluid or gas is fed into expresser chamber  23 , thereby causing the flexible membrane  11  to expand and compress the whole blood bag  6 . This forces the separated plasma to move from the whole blood bag  6  to the platelet concentrate bag  8  through tubing or a similar mechanism that interconnects the whole blood bag  6  and the platelet concentrate bag  8 . After filling the platelet concentrate bag  8 , the plasma continues to move toward the platelet poor plasma bag  9 . As the platelet rich plasma flows through the platelet concentrate bag  8 , the platelets sediment radially and collect on the outermost wall, while the platelet poor plasma continues to and fills the plasma bag  9 . Once all of the platelet-rich-plasma in the whole blood bag  6  has been squeezed out of the whole blood bag  6 , only red blood cells remain in the whole blood bag  6 . At this time, valve  21  is closed and valve  22  opens and the expressing fluid or gas continues to squeeze the red blood cells out of the whole blood bag  6  into the red blood cell bag  7 .  
         [0053]    Alternatively, rather than using an expresser chamber  23 , an expressor bag fabricated of a flexible, expandable material may be used.  
         [0054]    The number, types and positioning of the interconnected blood component bags may be designed to perform a particular separation activity. FIG. 5 illustrates the configuration of a few of these activities. For example, if only red blood cells and plasma are collected, then a double pack set shown in  5   a  can be used. If red blood cells, plasma and platelets are collected, then a triple pack set shown in  5   b  is used. If the packed red blood cells will require additional operations, such as adding chemicals to prepare the red blood cells for freezing, viral inactivation, enzymatic conversion, and the like, then a secondary pack set shown in  5   c  can be used where the packed red blood cells are temporarily stored in a bag  50  suitable for use in the centrifuge again. Leukodepleting filters  12 ,  13  that remove leukocytes from the packed red blood cells and platelet-rich-plasma, respectively, can be interconnected in the pack tubing arrangement. In all cases, it is preferable to collect the whole blood into a single whole blood bag  6  without regard for the ultimate activity for which the blood is being drawn. Then, just before processing, the appropriate pack set  5   a,    5   b,    5   c  is connected to the whole blood bad  6  by means of a sterile interlocking connector which consists of a female portion  36  sealed into the whole blood bag  6  and a male portion  37  sealed into the pack&#39;s connecting tube.  
         [0055]    The method of using the stacked coaxial configuration is as follows: units of whole blood are collected in sterile whole blood bags  6 . The whole blood bags  6  are then connected, while maintaining sterility, to the appropriate pack set  5   a,    5   b,    5   c,  as described above, and the various blood component bags are positioned in the appropriate cavities within the open cassettes 1  as described above. The cassettes  1  are then closed and loaded into the centrifuge  3 .  
         [0056]    The centrifuge  3  sediments the red blood cells at high speed to the outer portion of the whole blood bag  6 . Upon sedimentation of the red blood cells, expresser fluid or gas is pumped into the expressor chamber  23 , thereby causing the flexible membrane  11  to expand against the whole blood bag  6 . This causes the plasma to flow from whole blood bag  6 , past the optic detector  20 , through open valve  21 , through the platelet concentrate bag  8  to the platelet poor plasma bag  9 . As the plasma passes through the platelet concentrate bag  8 , platelets are sedimented and collected. The cavity that holds the platelet concentrate bag  8  is preferably sized to limit the amount of liquid held by the platelet concentrate bag  8  to a fixed volume (for example, 50 ml). The expression continues until the optic detector  20  detects the presence of red blood cells exiting the whole blood bag  6 . At that time, valve  21  closes and valve  22  opens to prevent red blood cells from passing into platelet concentrate bag  8  and the platelet poor plasma bag  9 . Additional valves may be located upstream, for example, valve  22 , which may open at this time. Expression then resumes to move the remaining red blood cells from the whole blood bag  6  into red blood cell bag  7 . The red blood cell bag may, if desired, be pre-charged with nutrient storage solution for extended storage of the red blood cells.  
         [0057]    In one embodiment, secondary separation devices, such as filters  12 ,  13  (e.g. leukodepleting filters) or columns (not shown), are positioned within with the device in-line between the various blood component bags. These secondary separation devices provide for the removal of target cells as they move from one bag to another. For example as the platelet rich plasma is expressed from the whole blood bag  6 , it can be forced through leukodepleting filter  13  at a precise rate to optimize the filter&#39;s performance. Similarly a leukodepleting filter  12  may also be placed inline with the inlet to the red blood cell bag  7 . If necessary, the inlet and outlet axis of either or both filters  12 ,  13  may be positioned radially rather than tangentially as shown if FIG. 6, so that the centrifugal force does not cause the fluid flow to be biased towards the radially most outboard position within the filter housing. In another embodiment, a column designed for the collection of CD-34 stem cells is positioned between the whole blood bag  6  and the plasma bag  9  such that the column collects CD-34 stem cells from the plasma stream as it is being expressed from the whole blood bag  6  to the plasma bag  9 . In another embodiment, a column may be positioned in line with the red blood cells such that the red blood cells are passed through the column to remove residual processing chemicals (e.g. glycerol, which is used for cryopreservation).  
         [0058]    Alternatively, these secondary separation steps may take place outside the centrifuge. Preferably, where the secondary separation steps occurs outside the centrifuge, a built-in refrigerated chamber (not shown) is included for controlling the temperature of the cells during the filtering process.  
         [0059]    The expresser fluid or gas, as shown in FIG. 7, may be transferred to the expressor chamber  23  from an external source through the inlet or port  60  which, in turn, is in fluid communication with a common supply header,  40 , positioned within the drive shaft  2 . Cassettes  1  are preferably positioned onto the drive shaft  2  in pairs so that one is 180° from the other as shown in FIG. 8. In this configuration, the plasma  71  that is expressed to the side of one cassette is mechanically balanced with the plasma  72  moving to the opposite side of the adjacent cassette. Similarly, the red blood cells  73  that are expressed to one side of one cassette are mechanically balanced by the red blood cells  74  moving to the opposite side of the adjacent cassette.  
         [0060]    The configuration of the cassettes  1  is not limited. For example, FIG. 9 shows a configuration where the cassettes is comprised of three segments: top segment  81  holds the whole blood bag  6 , middle segment  82  holds the expressor chamber  23 , flexible membrane  11  and filters  12 ,  13 , and bottom segment  83  holds the platelet concentrate bag  8 , the platelet poor plasma bag  9 , and the red blood cell bag  7 . This is advantageous in that the cassette  1  can be made more compact and can be used in a small, portable centrifuge where the diameter of the cassette  1  can be as small as 5-6 inches. Alternatively, the three segment cassette can made larger, for example 12 inches in diameter, in which case the cassette  1  could carry over three liters of fluids in addition to the volume of the cells. This may be useful if a secondary processing of the packed red blood cells requires large amounts or processing fluids. As an example, the deglycerolization of frozen red cells requires that approximately two liters of solutions be used to wash the cells before transfusion; hypertonic 12% NaCl, 1.6% NaCl, and resuspend in 0.9% saline with dextrose (Method 9.6 of the AABB Technical Manual 12 th  Edition). In this case, the three solutions can be carried “on board” to sequentially wash the red cells, loaded into the bags  7 ,  8 , and  9  in FIG. 9. Two expresser chambers  23  would be used to move the cells into and out of the red blood cell bag  7 , and an additional valve would be added. Preferably, a common centrifuge would be used to process a multiplicity of cassette styles, each performing a different blood processing activity in the blood center. Other examples include the washing or rejuvination of red cell cells (Method 9.5 of the AABB Technical Manual 12 th  Edition) that requires 2 liters of unbuffered 0.9% saline, virally inactivated cells (approximately 2 liters), enzymatic conversion of red cells (approximately 3 liters), and others.  
         [0061]    Another variation of the radial configuration cassette is shown in FIGS. 10. This configuration contains a top portion  17  and a bottom portion  18 . In this configuration, in the bottom portion  18 , the red blood cell bag  7  and platelet poor plasma bag  9  are positioned to be coaxial with each other and the whole blood bag  6 . The blood is collected and subsequently connected, while maintaining sterility, to a processing bag set, e.g. FIG. 5, in the same manner as described above with the exception that as the bag set is positioned into cassette  1 , the placement of the bags varies. In the bottom portion  18 , the whole blood bag  6  and expressor chamber  23  are placed into a cavity of the cassette. This chamber is in fluid communication with a supply of expressing fluid  39 , the pressure of which is controlled by a pumping means outside of the cassette. The top portion  17  of the cassette is placed over the bottom portion  18  to enclose the whole blood bag  6 . The top portion  17  contains cavities for the red blood cell bag  7 , platelet poor plasma bag  9 , and the platelet concentrate bag  8 . Cavities can also be provided for one or more filters. As shown in FIG. 10, for example, a platelet rich plasma filter  42  and a red blood cell leukofilter  41  are positioned in the cassette  1  as shown. Channels are preferably provided to fix the routing of the interconnecting tubing  14  so that sensors (such as optic and pressure sensors) and valves  21  can reliably contact the tubing  14 . These sensors and valves can be positioned within the cassette  1 , or, preferably outside the cassette  1  as part of the centrifuge drive mechanism.  
         [0062]    Another embodiment of the invention pumps the whole blood (or other cell mass) into the cassettes  1  while the separation is taking place. For example, in FIG. 11, multiple lumens (tubes)  34  are connected to the separation chambers of one or more cassettes  1  housed in a centrifuge  3  preferably through either of two means: a multichannel face seal or an Adams-type skip rope. The separation proceeds as described above, except that the additional blood that is continuously being pumped into the device displaces and forces the platelet-rich plasma out of the whole blood bag  6 . Then, as described above, when only red blood cells remain in the whole blood bag  6 , expressor fluid or gas can be pumped into the whole blood bag  6  through rotating seals  52  and feed tube  54  located in at the bottom of the centrifuge  3 . Similarly, if the expressor fluid or gas is removed from the whole blood bag  6 , then additional fluids can be added to the cell mass in the whole blood bag  6  via the rotating seal  52  or multiple lumens (tubes)  34  and removed with the expressor fluid or gas as it is again pumped into the whole blood bag  6 . In this configuration, the liquid that is expressed after the components have been separated can be expressed out of the whole blood bag  6  through any one the multiple lumens (tubes)  34  and into a waste bag. The number of cassettes is limited only by the strength of the closing mechanism that secures the cassettes  1  in the closed position during separation and the size of the centrifuge. If a small device is required, as few as one cassette can be used. If high throughput is required, a plurality of cassettes can be used.  
         [0063]    Shown in FIG. 11 is an alternate method for positioning the optics to detect the red blood cell interface during expression. In this case, the optic sensor  20  is fixed to the non-rotating containment wall of the centrifuge  3 . The optic sensor  20  monitors the tubing  14  in the cassette  1  through a hole  56  in the cassette  1  that allows visualization of the length of tubing  14  that carries the plasma and red blood cells from the whole blood bag  6  to the platelet concentrate bag  8 . The sampling rate of the optic sensor  20  is such that it emits and receives an optic signal in less time than that which is required for the hole  20  to rotate past its field of view.  
         [0064]    As shown in FIGS.  12 - 14 , an automated blood fractionation device in accord with another embodiment of the present invention has a radial segment configuration. In this configuration, a large rotating drum or a rotor  1 , is divided into pie-shaped segments  102 . Into each segment  102 , a cassette  103  having a shape conforming to the radial segment configuration of the rotor can be inserted. The cassette  103  is comprised of a plurality of sections  104 , and each section can contain one or more cavities  105  for the containment of the fluids necessary to effect the fractionation process. Cavities  105  can be structured and configured such as those shown or in any other manner to permit whole blood bags and various blood component bags or other flexible containers to be placed into and removed from the cavities  105 .  
         [0065]    The bags set, including the whole blood bags  6 , are then loaded into the cavities  105  in the cassette  103  (FIG. 12). The number of sections  104  and cavities  105  required depends on the number of bags used in a given process. Once the bags are loaded into the cassette  103 , the cassette  103  is closed. A lid (not shown) of the cassette  103  can be attached, for example, on one side of the cassette with hinges or other fastening means (not shown) so that the cassette can be opened to expose all cavities and shut quickly. As shown in FIGS. 13 and 14, the sections  104  can be connected with hinges or other fastening means  109  that allows the sections  104  to be separated from each other to expose the cavities  105 .  
         [0066]    In one preferred embodiment shown in FIG. 16, the cassette  103  consists of three sections: an inner section  110 , a middle section  111  and an outer section  112 . The inner section  110  typically contains a first expresser reservoir  113  into which an expresser bag  7  can be placed. The middle segment  111  contains both a second expressor reservoir  114 , into which an expressor bag can be placed and, adjacent to the expressor reservoir, a whole blood cavity  115  into which a whole blood bag  6  can be placed. The outer segment  112  contains a cavity for a platelet concentrate bag  8 . A final plasma bag  9  is positioned on the inside surface of the inner segment  110 , as shown in FIG. 16. The bags are interconnected by tubes  14  that allow fluid to flow from one bag to another. A pumping means  119  can further be located within the device to aid in moving fluid and components from one bag to another. A means for detecting when the fractionation process is complete and a means for closing the interconnection between bags also can be located within the cassette. For example, an optic detector  20  can be used, which senses the presence of red cells in the supernatant line and signals a valve  21  to close and the pump  119  to stop. This will prevent contamination between the contents of the various bags.  
         [0067]    Various configurations of conventional valve designs can be used. For example, two individual valves can be used that are either electronically powered or centrifugally actuated. A single, electronic two-way valve can be used in place of two separate valves to take up less space and add fewer power leads. The valves that are centrifugally actuated are preferred where it is desirable to eliminate the need for power connections  
         [0068]    The expressor bags that are used within the cassette  103  are preferably fabricated of a material that allows them to expand and contract repeatedly to move fluids between the bags. Preferably, the expressor bags are fabricated of an elastomeric material such as, for example, silicone or natural rubber. The expressor bags can be permanently installed in the cassette or, preferably, are removable.  
         [0069]    The whole blood bags  6  are sterile bags into which whole blood is drawn and processed. The whole blood bags  6  are fabricated of any type of material generally accepted and approved for that purpose. Preferably, the whole blood bags  6  are sized and shaped to fit readily into the appropriate cavity. However, any shape may be used provided the whole blood bag  6  fits within the appropriate cavity of the cassette  103 .  
         [0070]    The number of cassettes  103 , sections  104  and cavities  105  can vary depending on design choice. For example, fewer or more cassettes  103 , sections  104  and cavities  105  can be used depending, for example, on the number of whole blood bags being fractionated and the number of components into which the whole blood is to be separated.  
         [0071]    The method of using the radial segment configuration is as follows: units of whole blood are collected in sterile whole blood bags  6 . The whole blood bags  6  are then positioned in the appropriate cavities  105  within the cassettes  103  as described above. The cassettes  103  are closed and loaded into the segments  102  in the centrifuge  3 . Under centrifugal force, the red blood cells sediment radially outward in the whole blood bag  6 . After complete sedimentation, expressor fluid or gas is pumped from the first reservoir  113  to the second reservoir  114 , which compresses the whole blood bag  6  and forces the supernatant fluid (platelet rich plasma) through the platelet concentrate bag  8  and into the plasma bag  9 . During the routing through the platelet concentrate bag  8 , the platelets sediment to the outer surface and are collected in the platelet concentrate bag  8 . This expression continues until all of the supernatant has been expressed from the whole blood bag  6 . When this occurs, an optic detector  20  senses the presence of red cells in the supernatant line and signals a valve  21  to close and the expresser pump  119  to stop. This prevents any red cells from contaminating the downstream bags. The centrifuge can then be stopped and the cassettes  103  removed and opened. The bags are then separated and placed in the appropriate storage containers.  
         [0072]    In a preferred embodiment, filters or packed columns or other secondary separation devices are positioned such that when the blood component bags are removed from the device, they have attached to them the secondary separation device and a receiving/storage bag. This allows the product bag to be hung in a temperature-controlled environment and the product slowly gravity drained through the secondary separation device into the final receiving/storage bag, which might contain nutrient solutions for long-term storage. In this configuration, the centrifugal forces would not interfere with the function of the filter or column and the secondary separation step, which is relatively slow, does not tie up the centrifuge, thereby increasing throughput. In some cases, it is preferable to perform the secondary separations in line within the cassette without the double handling mentioned above. In such embodiments, the secondary separation devices are positioned in line such that separation would occur as the fluids are expressed from one blood component bag to another as set out above. For example, filters or columns can be positioned between the blood component bags, as set out above, to provide for the removal of target cells as they move from one blood component bag to another.  
         [0073]    In other embodiments, other fluids, such as sucrose-based storage solutions, can be included through the addition of extra bags and cavities. The number of bags and cavities is limited only by the space available in the rotor segment and the safety of flow streams within the cassette. Thus, any number of bags, sections  102 , cassettes  103 , segments  104  and cavities  105  is within the scope of the invention.  
         [0074]    The present invention preferably has an auto-balancing mechanism  142 , shown in FIG. 18, connected to the centrifuge  3 . Thus, manual balancing of loads, which is typically required when using conventional devices, would not be required. During fractionation, it is unlikely that the mass center of each cassette  103  will be in balance with the other segments  102 . It is further unlikely that the fraction of supernatant that is moved from one location to another will be equal in both the volume and the rate that would be necessary to keep the segments  102  in balance after the start of the expression step. Thus, an auto-balancing mechanism  142  continuously compensates for the changing imbalance.  
         [0075]    It is common to fix accelerometers to centrifuge assemblies to define the magnitude and the angle of the resulting imbalance vector for a rotating body such as that described herein. Similar accelerometers can be fixed to the centrifuge frame that supports the centrifuge  3  of the present invention. These accelerometers are positioned to capture readings only in the single plane of the bottom surface of the centrifuge  3 . A software algorithm then can be used to interpret this data, calculate the magnitude and angle of the imbalance, and signal a set of three linear actuator motors, as shown in FIG. 18, to move to a calculated position that results in an opposing force equal and opposite to that experienced from the imbalance. This effectively cancels out the imbalance effects and assures smooth running and reliable separation of the cells from the suspending plasma. Other mass distribution methods for canceling the imbalance also can be employed, such as pumping compensating fluid volumes to specific centrifuge locations.  
         [0076]    In another embodiment, the set of blood component bags is configured to fit into an existing piece of equipment that is already in the blood separations laboratory. FIG. 19A shows the layout of a multiple bucket set, while FIG. 19B illustrates a typical way to apply the aforementioned inventions to this swinging bucket. This embodiment operates to separate the blood components in a manner similar to the embodiments set out above.  
         [0077]    Although the present invention has been described in detail including the preferred embodiments thereof, such description is for illustrative purposes only, and it is to be understood that changes and variations may be made without departing from the spirit or scope of the following claims.