Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
  • B01D69/12—Composite membranes; Ultra-thin membranes
  • B01D69/1216—Three or more layers
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
  • A61M1/00—Suction or pumping devices for medical purposes; Devices for carrying-off, for treatment of, or for carrying-over, body-liquids; Drainage systems
  • A61M1/36—Other treatment of blood in a by-pass of the natural circulatory system, e.g. temperature adaptation, irradiation ; Extra-corporeal blood circuits
  • A61M1/3621—Extra-corporeal blood circuits
  • A61M1/3627—Degassing devices; Buffer reservoirs; Drip chambers; Blood filters
  • A61M1/3633—Blood component filters, e.g. leukocyte filters
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
  • B01D61/14—Ultrafiltration; Microfiltration
  • B01D61/18—Apparatus therefor
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D63/00—Apparatus in general for separation processes using semi-permeable membranes
  • B01D63/08—Flat membrane modules
  • B01D63/081—Manufacturing thereof
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D63/00—Apparatus in general for separation processes using semi-permeable membranes
  • B01D63/08—Flat membrane modules
  • B01D63/089—Modules where the membrane is in the form of a bag, membrane cushion or pad
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
  • A61M2202/00—Special media to be introduced, removed or treated
  • A61M2202/04—Liquids
  • A61M2202/0413—Blood
  • A61M2202/0415—Plasma
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
  • A61M2202/00—Special media to be introduced, removed or treated
  • A61M2202/04—Liquids
  • A61M2202/0413—Blood
  • A61M2202/0439—White blood cells; Leucocytes

Definitions

• the present invention pertains to a method for purifying blood plasma of white blood cells (leukocytes) and undesirable contaminants, particularly viral contaminants, and to an apparatus suitable for this use.
• white blood cells leukocytes
• undesirable contaminants particularly viral contaminants
• the albumin fraction of human plasma contains prealbumin and albumin, with molecular weights in the 60,000 to 70,000 range, while fibrinogen, and various immunoglobulins have molecular weights in the range of 300,000 to lxlO 6 .
• the ⁇ -lipoproteins important in the transport of fats and lipids, have molecular weights in the range of 3xl0 6 to 20xl0 6 .
• the pore size necessary to completely remove these agents, particularly retroviruses, is such that the filter becomes rapidly clogged, thus requiring large filter area or repeated filter replacement. Clogging is particularly important with respect to the small but finite amount of leukocytes present in conventionally prepared plasma. Leukocytes are deformable, and may clog fine pores even though the leukocytes are physically larger than the pore. Further, and as indicated previously, a small pore size may also filter out desirable macromolecules contained in the plasma.
• Leukocytes which are positively charged, have been separated from plasma by membranes having charged sites.
• the ability to separate leukocytes in this fashion allows membranes with larger pore sizes to be used, as the removal is due to electrostatic attraction rather than physical separation.
• the larger pore size enhances the useful flow rate.
• the charged membranes have a finite number of charged sites which limit their capacity.
• a given leucocyte may pass through the filter without encountering a charged site to bind it to the filtration medium. Random "pass through” cannot be tolerated in view of the danger of infection by agents such as hepatitis and HIV.
• the subject invention pertains to a process for purifying blood plasma which has been subjected to centrifugation or filtration to remove erythrocytes and a substantial quantity of leukocytes, wherein all or substantially all the remainder of the residual leukocytes are removed through the use of a sterilizable multicomponent filter stack.
• the filter stack consists of a prefilter, a leukocyte retaining, intermediate hydrophilic membrane filter ("intermediate membrane”) and a final, leukocyte retaining safety hydrophilic membrane filter (“final membrane”) .
• the subject invention further pertains to a steam sterilizable multi-element filter assembly
• a housing preferably of sterilizable polymer having inlet and outlet portions, the inlet portion including an inlet port and the outlet portion including an outlet port, the inlet and outlet portions defining a flow channel between the inlet and outlet ports; one or more prefilter (s) retained within the housing fully extending across the flow channel, the prefilter (s) disposed closer to the inlet port than the outlet port; two or more hydrophilic microporous membrane (s) retained within and preferably hermetically sealed to the housing and extending across the flow channel, an intermediate hydrophilic microporous membrane adjacent to the prefilter and disposed closer to the outlet port than the inlet port and at least a final hydrophilic microporous membrane adjacent the intermediate membrane; such that plasma to be purified must pass in order through the prefilter (s) , the intermediate hydrophilic microporous membrane, and then the final hydrophilic microporous membrane.
• the purified plasma produced in accordance with the invention is
• FIGURE 1 illustrates a side view of an assembled filter of one embodiment of the subject invention
• FIGURE 2a illustrates a side view of the inlet portion of one embodiment of a filter device prior to assembly
• FIGURE 2b illustrates a view in plan of the inlet portion of one embodiment of a filter device according to the present invention, from the direction of the sealing surfaces;
• FIGURE 3a illustrates a side view of the outlet portion of one embodiment of a filter device prior to assembly
• FIGURE 3b illustrates a view in plan of one embodiment of a filter device according to the present invention, from the direction of the sealing surfaces;
• the flow channel of the device comprises the enclosed volume including inlet flow channel 10 and outlet flow channel 6, respectively.
• the ramps formed by the rising outermost surfaces are terminated by substantially vertical walls 31 and 32 on which inlet 9 and outlet 17 are located.
• Figure 2a illustrates a side view of the inlet portion 2 of one embodiment of the subject filter device across section 2a of Figure 2b.
• At 9 is the inlet through which plasma to be treated flows into inlet flow channel 10.
• At 11 is a raised annular portion which forms a seal, for example a compression seal, against the filter (s) when the device is assembled.
• At 13 is a raised annular rib of generally triangular cross-section, which is used to seal the inlet portion 2 of the device to outlet portion 4 ( Figures 1, 3a, 3b, 4) .
• Shown at 15 is an optional vent hole which will be plugged or covered by a microporous hydrophobic membrane to allow air to escape the device but not liquid.
• the perimeter of the inlet portion of the device is substantially planar and is surrounded by a raised annular portion 11 which serves to compress and/or seal the periphery of the prefilter (s) .
• a raised annular rib 13 Spaced apart from the raised 5 annular portion 11 is a raised annular rib 13 which serves as a pressure concentrating structure when pressed against the corresponding raised annular mating surface 23 ( Figures 3a, 3b, 4) of the outlet portion of the device.
• Other sealing arrangements will readily suggest themselves to one skilled in
• Figure 5 illustrates the placement of the final microporous hydrophilic membrane 25b, intermediate microporous hydrophilic membrane 25a, prefilter 29, and the relative geometries of the various annular surfaces when the device is assembled.
• the hydrophilic microporous membranes 25a and 25b are sealed, preferably heat sealed, to sealing surface 27, and supported across outlet channel 6 by ribs 21.
• the prefilter 29 is trapped between the portion of the intermediate hydrophilic microporous membrane atop sealing surface 27 and annular raised portion 11.
• Raised annular rib 13 has been deformed in the heat sealing process to form a unitary structure with raised annular mating surface 23.
• the plasma flow is through the inlet 9 into inlet channel 10, through prefilter 29, intermediate membrane 25a, and final membrane 25b into outlet channel 6 and from there to outlet 17 ( Figure 1) .
• the inlet 9 is connected to a plasma supply source, which may supply plasma by gravity flow or under pressure, e.g., through use of a peristaltic-type or plunger- type pump. Air is displaced through optional vent 15 and the plasma passes through the prefilter 29 and then through the hydrophilic microporous membranes 25a and 25b.
• the prefilter is a "depth-type" prefilter, and thus the majority of macrocytes and granulocytes and any other large particulates may be trapped by the prefilter without significantly decreasing its flow rate.
• the maximum pore size of the final membrane is selected so as to be considerably smaller than the minimum leucocyte diameter. It is most desirable to remove leukocytes such that their concentration in the plasma is reduced by a factor of at least about 10 3 , preferably about
• the final leukocyte concentration is 0.
• the prefilter performs the function of removing large particulates and gelatinous substances so as to prevent clogging of the intermediate filter.
• the prefilter also may remove a substantial portion of large leukocytes, i.e. macrocytes and granulocytes .
• the intermediate membrane removes the most substantial portion of smaller leukocytes such that plasma exiting the intermediate membrane has had preferably greater than about 90% of leukocytes removed.
• the final membrane has smaller pores than the intermediate membrane, and ensures that virtually no leukocytes remain in the completely filtered plasma.
• the pore size and type must be selected with the function of the particular filter element in mind.
• a relatively large pore size is selected for rapid filtration yet which will retain substantially all large particulates.
• the preferred pore size is from about 3 ⁇ m to about 10 ⁇ m . This relatively large pore size is necessary since the pore size range of membrane filters is ordinarily well controlled.
• the prefilter comprise a non- woven depth-type filter.
• Such filters are available from numerous sources, and may consist, for example, of fiberglass, spun bonded or melt blown polypropylene, polyester, and the like, and may have a nominal, or "average" pore size of from about 0.5 ⁇ m to about 5 ⁇ m .
• the smaller average pore size is a reflection of the relatively wide pore size range of such materials and the alternative fluid flow paths which depth- type filters present.
• the most preferable prefilter is a non- woven fiberglass prefilter available from Hollingsworth & Vose as HB-5341 glass filter medium.
• the intermediate membrane filter is a hydrophilic membrane filter which has a pore size range sufficiently small that in combination with the prefilter, greater than about 80% of the leukocytes, more preferably greater than about 90% of the leukocytes, and most preferably in excess of about 95% of the leukocytes, are retained by the combination of prefilter and intermediate membrane.
• the intermediate membrane will pass no more than about 20% of the leukocytes, preferably no more than about 10%, and most preferably no more than about 5% of the leukocytes. It is yet more preferable that not more than about 1% of leukocytes pass through the intermediate membrane.
• the pore size of the membrane may vary somewhat, but is preferably in the range of about 0.9 to about 2.0 ⁇ m, more preferably in the range of about 0.9 to about 1.5 ⁇ m .
• the composition of the intermediate membrane is not overly critical, so long as the membrane is hydrophilic.
• intrinsically hydrophobic membranes which have been treated to render their surface hydrophilic are suitable, as are also intrinsically hydrophilic membranes.
• Membranes may be made of, for example, polyacrylates, nylon, polyvinylidene fluoride, polypropylene, polysulfone, polyethersulfone, cellulose acetate, or nitrocellulose. Charged membranes are suitable as well.
• Nylon membranes are well suited for use herein.
• a particularly preferred membrane is SUPOR ® 1200, a polyethersulfone microporous membrane with a nominal pore size of 1.2 ⁇ m available from Pall Gelman Sciences, Inc., Ann Arbor, Michigan.
• the final filter is selected so as to provide a pore size small enough to ensure substantially complete leukocyte removal. Since the vast majority of leukocytes and larger particulates and gels have been removed by the prefilter and the intermediate membrane filter, the small pore size of the final membrane will not overly slow the filtration rate.
• the final membrane is hydrophilic, and may be a charged membrane as well.
• the pore size range of the final membrane is from about 0.3 to about 1.5 ⁇ m, and preferably is of a smaller or equal pore size than the intermediate membrane.
• a pore size range of about 0.4 ⁇ m to about 1.0 ⁇ m is suitable, and a range of about 0.7 ⁇ m to about 1.0 ⁇ m is preferred.
• Particularly suitable is a SUPOR ® polyethersulfone microporous membrane with a nominal pore size of 0.8 ⁇ m.
• the surface area, or effective filtration area (EFA) of the filter may be adjusted according to the volume of plasma to be filtered and the desired flow rate.
• EFA effective filtration area
• the subject device has been illustrated with reference to a planar, substantially rectangular filter capsule.
• other shapes are useful as well, including pleated cylindrical filters, spiral wound cylindrical filters, and the like, provided the subject filter stack is used.
• the internal volume should be minimized so that retention of plasma by the filter itself is as small as possible.
• a minimum flow rate of about 1 to about 10 ml/min/cm 2 at 1 psi or thereabouts is desired, more preferably a minimum flow rate of about 2-3 ml/min/cm 2 . Higher flow rates are, of course, desired.
• the filter should preferably be capable of filtering a minimum of about 300 ml of human plasma before the flow rate decreases to such an extent that the filter may be considered to be "plugged" .
• the filtration efficiency should be such that a 10 4 reduction of leukocytes from conventionally prepared plasma containing a normal leukocyte concentration is possible. In the most preferable case, no leukocytes will be present in the filtrate.
• suitable filter areas are not particularly limited.
• cartridge filters with pleated or spiral elements may be designed for large volume filtration, while small units may be provided for filtration of single plasma units. In the latter case, for example, a suitable filter size has an EFA of from about 15 to about 20 cm 2 . However, units with EFAs of from 0.1 m 2 to several m 2 or larger are also feasible.
• the prefilter material should meet USP requirements for particle shedding and Class VI toxicity requirements. Preferably, the material further meets European community toxicity requirements as well.
• hydrophilic microporous membranes are Supor ® microporous membranes available from Pall Gelman Sciences.
• the housing for the multicomponent filter assembly of the subject invention are preferably prepared from injection molded polymer.
• the polymer may be a thermoplastic or thermosetting polymer, and should be sterilizable. Moreover, the polymer must not elute toxic metals, oligomers, monomers, or catalysts in the presence of aqueous solutions.
• heat-sealable or solvent-bondable thermoplastics may be used, it is preferable that the polymer be capable of being sealed by ultrasonic or RF welding techniques.
• the suitable polymers are the amorphous polyamides, high temperature polyacrylics and polyesters, and most preferably, the polycarbonates .
• a preferred polycarbonate is MAKROLON 2658-1112 Natural, available from Miles, Inc.
• Leukocyte-removal filter devices were composed of glass fiber/Supor ® 1200/Supor ® 800 membranes, with an effective filtration area (EFA) of 17 cm 2 .
• EFA effective filtration area
• Plasma from four individual units (ranging in volume from 255 mL to 410 L) was pooled together in a 3-L sterile collapsible admixture bag, after which testing was performed as soon as possible (less than 30 minutes) .
• Plasma was delivered from the collapsible bag, at 28 inch head height, through a Medical Specialties 103 inch vented administration set.
• the average cumulative volume of human plasma delivered through the leukocyte-removal filter devices was 258.4 mL.
• the average volume of human plasma delivered per time per unit of EFA (mL/min/cm 2 ), based on the results of this experiment, was 2.31 mL/min/cm 2 . This number represents average value at 48.3% flow decay, following delivery of 100-mL plasma after two minutes of flow.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Health & Medical Sciences (AREA)
• Water Supply & Treatment (AREA)
• Vascular Medicine (AREA)
• Heart & Thoracic Surgery (AREA)
• Anesthesiology (AREA)
• Life Sciences & Earth Sciences (AREA)
• Animal Behavior & Ethology (AREA)
• General Health & Medical Sciences (AREA)
• Public Health (AREA)
• Veterinary Medicine (AREA)
• Manufacturing & Machinery (AREA)
• Hematology (AREA)
• Biomedical Technology (AREA)
• Cardiology (AREA)
• External Artificial Organs (AREA)
• Separation Using Semi-Permeable Membranes (AREA)
• Medicines Containing Material From Animals Or Micro-Organisms (AREA)

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Citations (13)

• 1997
  • 1997-11-05 CA CA002270413A patent/CA2270413A1/en not_active Abandoned
  • 1997-11-05 AU AU50059/97A patent/AU722640B2/en not_active Ceased
  • 1997-11-05 CN CN97181290A patent/CN1122536C/zh not_active Expired - Fee Related
  • 1997-11-05 WO PCT/US1997/019908 patent/WO1998019722A1/en not_active Application Discontinuation
  • 1997-11-05 EP EP97913002A patent/EP0938351A1/en not_active Withdrawn
  • 1997-11-05 JP JP52163498A patent/JP2001503656A/ja active Pending
• 1999
  • 1999-05-04 NO NO992162A patent/NO992162L/no not_active Application Discontinuation

Patent Citations (14)

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