JP2015150349A - Method for preparing cleaned platelet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for preparing cleaned platelets by which a membrane of a hollow fiber membrane module is less clogged with platelets, and a protein removal rate and a platelet recovery rate can be increased.SOLUTION: A method for preparing cleaned platelets includes: (a) a diluting process for diluting a platelet suspension; (b) a filtration process for filtering by a total amount filtration method by introducing the diluted platelet suspension diluted in the diluting process (a) in an inflow side space of a hollow fiber membrane module and for removing protein molecules in the platelet suspension by making the protein molecules pass into a filtration side space; (c) a cleaning process for introducing a cleaning liquid into the inflow side space to remove the protein molecules remaining in the inflow side space; and (d) a recovery process for introducing a preservation liquid in the inflow side space to recover platelets existing in the inflow side space. The diluting process (a) includes the dilution to obtain the platelet suspension with a protein concentration of 55 mg/mL or less. In addition, a value of a maximum flow rate/water permeability in the filtration process is 0.15 kPa or less.

Description

  The present invention relates to a method for producing washed platelets by washing and removing protein molecules in a platelet suspension using a hollow fiber membrane module.

  Platelet preparations are manufactured by collecting platelets from blood by centrifuging blood components collected from donated blood donors to obtain a platelet suspension in which platelets are suspended in plasma. However, since normal platelet preparations contain contaminants such as protein molecules in the plasma, non-hemolytic transfusion side effects occur when blood platelets are transfused due to plasma proteins. There is a case. In order to reduce the frequency of occurrence of these non-hemolytic transfusion side effects, it is recommended to use washed platelets from which proteins have been removed by washing operations.

  Washed platelets are produced by physically separating and removing contaminants such as protein molecules from the platelet suspension. Methods for separating and removing contaminants such as protein molecules from blood components include a centrifugal separation method and a membrane filtration method.

  Conventionally, centrifugal methods are used to produce washed platelets. Centrifugation is a method in which a platelet suspension as a raw material is centrifuged to remove a supernatant containing protein molecules, and then a preservation solution is added to the concentrated platelets.

  On the other hand, the membrane filtration method is a method of removing protein molecules by filtering a platelet suspension using a membrane. Patent Document 1 discloses a method for removing protein molecules in blood by a membrane filtration method using a plasma separation membrane module. Patent Document 2 discloses a method of removing protein molecules from a platelet suspension by cross-flow filtration, and Patent Document 3 discloses a method of filtering the entire amount of platelet suspension with a membrane. .

Japanese Patent Laid-Open No. 1-171566 JP 2012-143554 A JP 2012-176081 A

  However, the conventional centrifugal separation method used for the production of washed platelets has a large damage to the platelets due to the centrifugal separation, and there are problems such as platelet activation and the generation of aggregates. In addition, since it is difficult to completely remove the supernatant, it is necessary to centrifuge a plurality of times in order to sufficiently reduce the total protein amount, and the operation is complicated, the processing time is long, and the platelet recovery rate is high. There is a problem that it is low.

  The membrane filtration method by crossflow filtration described in Patent Documents 1 and 2 removes protein molecules by crossflow filtration in which a flow parallel to the membrane and a flow that filters the membrane are flowed at an arbitrary ratio. However, protein molecules are not removed from the parallel flow. Therefore, in order to sufficiently reduce the total protein amount, it is necessary to perform separation several times, and there are problems that the operation is complicated, the processing time is long, platelet activation is increased, and the platelet recovery rate is low.

  Furthermore, the method of filtering the whole amount of the platelet suspension described in Patent Document 3 with a membrane is a method with a high protein removal rate, but the platelets are easily clogged and the clogged platelets are not recovered. There is a problem that the platelet recovery rate is lowered. Patent Document 3 describes that the clogged blood components are peeled off, but the filtration amount of the membrane is reduced to 20% or less, and the clogging suppression effect is not sufficient. Not mentioned.

  Thus, in order to remove contaminants such as proteins from the platelet suspension and wash the platelets to produce washed platelets, it is necessary that the protein removal rate and the platelet recovery rate be high. There was no method with both high protein removal rate and platelet recovery rate.

  Accordingly, the present invention provides a method for producing washed platelets that can reduce the clogging of platelets in the membrane and increase the protein removal rate and the platelet recovery rate in the production of washed platelets by filtration using a hollow fiber membrane module. The purpose was to provide.

  As a result of intensive studies to solve the above problems, the inventors of the present application have conducted filtration treatment by a total amount filtration method under specific conditions in the production of washed platelets by a filtration method using a hollow fiber membrane module. Thus, the inventors have found that impurities such as protein molecules can be removed at a high rate without reducing the platelet recovery rate, and the present invention has been completed.

That is, the present invention provides the following methods for producing washed platelets (1) to (6).
(1) (a) Dilution step of diluting the platelet suspension; (b) The inflow side space through which the liquid that does not permeate the hollow fiber membrane and the filtration side space through which the liquid that has permeated the hollow fiber membrane flow are hollow fibers. Introducing the platelet suspension diluted in the dilution step (a) into the inflow side space of the hollow fiber membrane module separated by the membrane, filtering the whole amount using a filtration method, and allowing protein molecules to permeate the filtration side space (C) a washing step of introducing a washing solution into the inflow side space to remove protein molecules remaining in the inflow side space; and (d) an inflow side space. In the method for producing washed platelets, comprising a collection step of introducing a preservative solution into the inflow side space and collecting the platelets present in the inflow side space, wherein the dilution step (a) comprises a protein concentration in the platelet suspension of 55 mg / including dilution to less than mL In the filtration step (b), the maximum flow rate / water permeability performance value of the hollow fiber membrane module is 0.15 kPa or less.
(2) The method according to (1), wherein the platelet concentration ratio in the filtration step (b) is 1.1 times or more and 6 times or less.
(3) The method according to (1) or (2), wherein the total platelet count / membrane area subjected to filtration in the filtration step (b) is 6 × 10 ¹¹ cells / m ² or less.
(4) The method according to any one of (1) to (3), wherein a linear velocity at an inlet of the hollow fiber membrane module in the filtration step (b) is 2 cm / min or more and 150 cm / min or less.
(5) The method according to any one of (1) to (4), wherein the filtration step (b) is performed by internal pressure filtration.
(6) The method according to any one of (1) to (5), wherein a maximum filtration pressure in the filtration step (b) is 30 kPa or less.

  According to the present invention, washed platelets having a low total protein content and a high total platelet count can be obtained by removing contaminants such as protein molecules at a high rate from the platelet suspension without reducing the platelet recovery rate. Can be manufactured.

It is longitudinal direction sectional drawing of the hollow fiber membrane module for internal pressure type used for the manufacturing method of this invention. It is sectional drawing perpendicular | vertical with respect to the longitudinal direction of the hollow fiber membrane module for internal pressures used for the manufacturing method of this invention. It is longitudinal direction sectional drawing of the hollow fiber membrane module for external pressures used for the manufacturing method of this invention. It is sectional drawing perpendicular | vertical with respect to the longitudinal direction of the hollow fiber membrane module for external pressures used for the manufacturing method of this invention. It is the schematic of the device for platelet suspension washing | cleaning using the hollow fiber membrane module for internal pressure type used for the manufacturing method of this invention. It is the schematic of the device for platelet suspension washing | cleaning using the hollow fiber membrane module for external pressure type used for the manufacturing method of this invention.

The method for producing washed platelets of the present invention comprises:
(A) a dilution step for diluting the platelet suspension;
(B) In the inflow side space of the hollow fiber membrane module in which the inflow side space in which the liquid that does not permeate the hollow fiber membrane flows and the filtration side space in which the liquid that has permeated the hollow fiber membrane flow are separated by the hollow fiber membrane, A filtration step of removing the protein molecules in the platelet suspension by introducing the platelet suspension diluted in the dilution step (a), filtering the whole amount by a filtration method, and allowing the protein molecules to pass through the filtration side space;
(C) a washing step of introducing a washing solution into the inflow side space and removing protein molecules remaining in the inflow side space; and (d) introducing a preservation solution into the inflow side space and presenting platelets in the inflow side space. The dilution step (a) includes diluting the protein concentration in the platelet suspension to 55 mg / mL or less, and the maximum flow rate / hollow fiber in the filtration step (b). The membrane module has a water permeability value of 0.15 kPa or less.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings, but the present invention is not limited to these aspects. Further, the ratios of the drawings do not necessarily match those described.

  An internal pressure type hollow fiber membrane module, which is a first embodiment of the hollow fiber membrane module used in the production method of the present invention, will be described with reference to FIGS. FIG. 1 is a longitudinal sectional view of a hollow fiber membrane module 1 for internal pressure, and FIG. 2 is a sectional view perpendicular to the longitudinal direction of the hollow fiber membrane module 1 for internal pressure. In the case of the hollow fiber membrane module for internal pressure type, the platelet suspension is passed through the hollow part of the hollow fiber membrane for filtration.

  The hollow fiber membrane module 1 for internal pressure type has a tubular member 2 and headers 3 and 4 that are liquid-tightly connected and fixed to both ends of the tubular member 2, and a bundle of hollow fiber membranes 5 is contained therein. It is the structure to hold. At the top of the header 3, a platelet suspension inlet 6 for introducing the platelet suspension into the hollow fiber membrane module protrudes, and the top of the header 4 is filtered by the bundle 5 of hollow fiber membranes. A washed platelet outlet 7 for discharging a liquid containing washed platelets obtained in this manner is formed to protrude. Further, a filtrate outlet 8 for discharging unnecessary filtrate is formed on the side of the tubular member 2 on the header 4 side.

  The bundle of hollow fiber membranes 5 is arranged over the entire length in the long axis direction in the cylindrical member 2, and both ends of the hollow fiber membranes 5 are the hollow fiber membrane hollow portions 13 that are the lumens of the hollow fiber membranes 5. The opening is not blocked, and is fixed to the inner peripheral surface of the cylindrical member 2 by a partition wall 9 on the header 3 side and a partition wall 10 on the header 4 side formed by a hardened potting agent. Although not particularly limited, in the case of producing washed platelets using a platelet suspension containing about 10 units of platelets and having a liquid volume of about 160 mL to 240 mL as a raw material, the number of hollow fiber membranes held in the module is usually about several thousand.

  When the platelet suspension is introduced from the platelet suspension inlet 6, the platelet suspension flows into the inflow side space 11. This inflow side space 11 is a space in which the platelet suspension before filtration (that is, the platelet suspension before passing through the pores of the hollow fiber membrane) exists. The inflow side space can also be referred to as the platelet side space. In the hollow fiber membrane module 1 for internal pressure type, the inflow side space 11 includes a space surrounded by the header 3 and the partition wall 9, a space surrounded by the header 4 and the partition wall 10, and a space inside the hollow fiber membrane hollow portion 13. It refers to the gathered space. The inflow side space 11 communicates with the platelet suspension inlet 6 and the washed platelet outlet 7.

  The platelet suspension flowing in the inflow side space 11 is filtered by passing through the membrane through the pores existing in the hollow fiber membrane 5, and the substance that has permeated the membrane flows into the filtration side space 12. The filtration side space 12 is a space into which a substance that has passed through the membrane flows through the pores of the hollow fiber membrane. In the hollow fiber membrane module 1 for internal pressure type, the filtration side space 12 is a space excluding the hollow fiber membrane 5 and the hollow fiber membrane hollow portion 13 among the spaces sandwiched between the tubular member 2 and the partition walls 9 and 10. Point to. Further, the filtration side space 12 communicates with the filtrate discharge port 8.

  The bundle of hollow fiber membranes 5 is arranged over the entire length in the long axis direction in the cylindrical member 2, and both ends of the hollow fiber membranes 5 are the hollow fiber membrane hollow portions 13 that are the lumens of the hollow fiber membranes 5. The opening is not blocked, and is fixed inside the cylindrical member 2 by a partition wall 9 on the header 3 side and a partition wall 10 on the header 4 side formed by a hardened potting agent.

  An external pressure type hollow fiber membrane module, which is a second embodiment of the hollow fiber membrane module used in the production method of the present invention, will be described with reference to FIGS. 3 is a longitudinal sectional view of the hollow fiber membrane module 14 for external pressure type, and FIG. 4 is a sectional view perpendicular to the longitudinal direction of the hollow fiber membrane module 14 for external pressure type. In the case of a hollow fiber membrane module for external pressure type, filtration is performed by flowing a platelet suspension into a space outside the hollow fiber membrane. Regarding the external pressure type hollow fiber membrane module according to the second embodiment, those having the same functions as those of the internal pressure type hollow fiber membrane module illustrated in FIG. 1 and FIG. explain.

  The hollow fiber membrane module 14 for external pressure type has a tubular member 2 and headers 3 and 4 that are liquid-tightly connected and fixed to both ends of the tubular member 2, and a bundle of hollow fiber membranes 5 is placed inside the tubular member 2. It is the structure to hold. In addition, a platelet suspension inlet 6 for introducing the platelet suspension into the hollow fiber membrane module is formed on the side of the tubular member 2 on the header 3 side, and on the header 4 side of the tubular member 2. On the side portion, a washed platelet outlet 7 for discharging a liquid containing washed platelets separated from the platelet suspension by being filtered by the bundle 5 of hollow fiber membranes is formed so as to protrude. Furthermore, a filtrate outlet 8 is formed at the top of the header 4 for discharging the filtrate containing impurities such as unnecessary protein molecules separated from the platelet suspension.

  The bundle of hollow fiber membranes 5 is disposed over the entire length in the long axis direction in the cylindrical member 2, and both ends of the hollow fiber membranes 5 are at least the end portions of the hollow fiber membranes 5 on the side close to the filtrate outlet 8. (The opening portion of the hollow fiber membrane hollow portion 13) is fixed inside the tubular member 2 by the partition wall 9 on the header 3 side and the partition wall 10 on the header 4 side formed by a hardened potting agent so as not to be blocked. ing. Unlike the internal pressure type module that is the first form, in the external pressure type hollow fiber membrane module, the end of the hollow fiber membrane 5 on the side far from the filtrate outlet 8 may be closed, It may be folded back into a U-shape.

  When the platelet suspension is introduced from the platelet suspension inlet 6, the platelet suspension flows into the inflow side space 11. The inflow side space 11 is a space in which platelet suspension before filtration (that is, platelet suspension before passing through the membrane through the pores of the hollow fiber membrane) stays. In the external pressure type hollow fiber membrane module 14, the inflow side space 11 is a space excluding the hollow fiber membrane 5 and the hollow fiber membrane hollow portion 13 among the spaces sandwiched between the tubular member 2 and the partition walls 9 and 10. Point to. The inflow side space 11 communicates with the platelet suspension inlet 6 and the washed platelet outlet 7. Therefore, in this aspect, the inflow side space 11 is a space formed by the inner wall of the cylindrical member 2 having the platelet suspension inlet 6 and the washed platelet outlet 7 and the gap between the hollow fiber membranes 5. Can do.

  Further, in the external pressure type hollow fiber membrane module 14, the filtration side space 12 includes a space surrounded by the header 3 and the partition wall 9, a space surrounded by the header 4 and the partition wall 10, and a space in the hollow fiber membrane hollow portion 13. It refers to the space where Further, the filtration side space 12 communicates with the filtrate discharge port 8. Therefore, in the said aspect, it can be said that the filtration side space 12 is the space formed by the inside of the header 3, the inside of the header 4 which has the filtrate discharge port 8, and the hollow fiber membrane hollow part 13. FIG.

  In the present invention, the hollow fiber membrane used in the module is not particularly limited as long as it is a hollow fiber membrane made of a so-called blood compatible material that does not activate platelets, and washed platelets are produced by a membrane filtration method. A hollow fiber membrane used by a known method, for example, a hollow fiber membrane described in Patent Documents 2 and 3 can be preferably used.

  Examples of the material of the hollow fiber membrane include polyamide, aromatic polyamide, polyethylene terephthalate, polyethylene, polypropylene, polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile, and polysulfone-based polymers such as polysulfone or polyethersulfone. Polysulfone polymers having excellent water permeability and blood component separation performance are preferred.

  The hollow fiber membrane constituting the hollow fiber membrane bundle has at least a surface on the side in contact with platelets (for example, if filtration is performed with an internal pressure method, at least the hollow fiber membrane to prevent activation of platelets in contact therewith) It is preferable that a hydrophilic component is contained in the lumen-side surface. Here, the “hydrophilic component” refers to a substance that is easily soluble in water and has a solubility of 10 g / 100 g or more with respect to pure water at 20 ° C.

  As the hydrophilic component, since there is less concern about elution, a polymer compound is preferable. Examples of the polymer compound as the hydrophilic component include methacrylic acid, acrylic acid, itaconic acid, 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl methacrylate, 2-hydroxypropyl acrylate, glycerol methacrylate, and polyethylene glycol. Homopolymers of these compounds, such as methacrylate, N, N′-dimethylacrylamide, N-methylacrylamide, dimethylaminoethyl methacrylate, methylenebisacrylamide, diacetone acrylamide, vinyl pyrrolidone, vinyl alcohol, ethylene glycol or propylene glycol Examples include a copolymer containing at least one monomer.

  Examples of the method for incorporating a hydrophilic component on the surface of the hollow fiber membrane include a coating method using physical adsorption, a crosslinking method using heat or radiation, or a chemical bonding method using a chemical reaction. Further, in the step of producing the hollow fiber membrane, the injection solution is flowed inward when the membrane forming stock solution is discharged from the double annular die, and a hydrophilic polymer may be added to the injection solution. In this way, the hydrophilic polymer in the injection solution diffuses to the membrane forming stock solution side before the hollow fiber membrane is phase-separated and the membrane structure is determined, so that the hydrophilic polymer is localized on the inner surface of the hollow fiber membrane. Can be materialized.

  The inner diameter and film thickness of the hollow fiber membrane are not particularly limited, but those having an inner diameter of about 100 to 500 μm and a film thickness of about 30 to 120 μm can be preferably used.

  The average pore size of the pores of the hollow fiber membrane is 2 μm or less, preferably 1 μm or less because the size of platelets to be washed, particularly human platelets, is 3 to 4 μm.

  A device for washing platelet suspension used in the production method of the present invention will be described with reference to FIGS. FIG. 5 is a schematic diagram of a platelet suspension washing device using a hollow fiber membrane module for internal pressure, and FIG. 6 is a schematic diagram of a platelet suspension washing device using a hollow fiber membrane module for external pressure. is there. A bag for storing the platelet suspension and a bag for storing the preservation solution are arranged in parallel in the uppermost stream of the circuit connected to the platelet suspension inlet 6 and the tube clamp 17 is arranged downstream so that the connection to the circuit can be switched. Has been. Between the platelet suspension and preservation solution and the hollow fiber membrane module 1 or 14, the pump 16 for feeding the platelet suspension and preservation solution and the gas mixed into the hollow fiber membrane module 1 or 14. An air chamber 15 is arranged for prevention. A bag for storing filtrate is disposed downstream of the circuit connected to the filtrate discharge port 8, and a bag for storing washed platelets is disposed downstream of the circuit connected to the washed platelet outlet 7 so that the connection to the circuit can be switched. A tube clamp 17 is arranged upstream of each bag.

  “Platelet suspension” refers to a fluid in which platelets collected from a donated donor or the like are suspended in plasma. What is generally called a platelet preparation is included in the platelet suspension referred to herein. An anticoagulant such as citric acid or a preservation solution may be added to the platelet suspension. The platelet suspension used in the method of the present invention usually has a platelet concentration that is three times higher than that of whole blood.

  The “preservation solution” is a liquid that stably floats platelets in the liquid. As this preservation solution, a liquid containing bicarbonate is preferably used.

  “Washing liquid” is a liquid for washing platelets remaining in the inflow side space, and in order to stably float the platelets in the liquid, a liquid containing bicarbonate is preferable as well as a preservation liquid. Used for.

  A method for producing washed platelets from a suspension of platelets by a total filtration method using the hollow fiber membrane module 1 or 14 described above will be described below with reference to the drawings as appropriate.

The method of producing washed platelets from the suspension of platelets by total filtration is
(A) a dilution step for diluting the platelet suspension;
(B) In the inflow side space of the hollow fiber membrane module in which the inflow side space in which the liquid that does not permeate the hollow fiber membrane flows and the filtration side space in which the liquid that has permeated the hollow fiber membrane flow are separated by the hollow fiber membrane, A filtration step of removing the protein molecules in the platelet suspension by introducing the platelet suspension diluted in the dilution step (a), filtering the whole amount by a filtration method, and allowing the protein molecules to pass through the filtration side space;
(C) a washing step of introducing a washing solution into the inflow side space and removing protein molecules remaining in the inflow side space; and (d) introducing a preservation solution into the inflow side space and presenting platelets in the inflow side space. A recovery step of recovering

  In the filtration step (b), the whole amount of the platelet suspension is filtered through the hollow fiber membrane, so that platelets that do not permeate the hollow fiber membrane remain in the inflow side space, and protein molecules and moisture that permeate the hollow fiber membrane as the filtrate. After passing through the filtration side space, the filtrate is discharged through the filtrate outlet. In the inflow side space after the filtration step (b) is performed, protein molecules that could not be filtered normally remain together with platelets. Therefore, in the washing step (c), a washing solution is poured into the inflow side space to remove protein molecules. Further removal is performed. Thereby, the protein removal rate can be further increased. Platelets after washing are collected by flowing a preservation solution into the inflow side space in the collection step (d).

  By these operations, washed platelets from which protein molecules have been removed can be produced. In the course of this operation, if protein molecules act on platelets, and platelets adhere to the hollow fiber membrane surface, the platelet recovery rate decreases.

  In the present invention, in order to increase the platelet recovery rate, the dilution step (a) for diluting the platelet suspension is performed before the filtration step (b). The dilution step (a) includes diluting the protein concentration of the platelet suspension to 55 mg / mL or less, preferably 50 mg / mL or less, more preferably 45 mg / mL or less.

  The dilution step (a) may be diluted by adding the diluent to the total amount of the platelet suspension as a raw material (in this case, the diluted platelet suspension is used as the platelet suspension bag of the device of FIG. 5 or FIG. 6). And the subsequent steps can be carried out), or the diluted platelet solution can be diluted by joining it into a circuit that sends the platelet suspension before filtration to the hollow fiber membrane module. Alternatively, since platelets are more likely to aggregate in the later stage when the platelet concentration and filtration pressure also increase than in the initial stage of the filtration step (b), the platelets are gradually introduced into the hollow fiber membrane module as the filtration proceeds. The platelet suspension concentration may be decreased. When diluting stepwise in this way, when the filtration step (b) is completed, the protein concentration of the platelet suspension introduced into the inflow side space of the hollow fiber membrane module is 55 mg / mL or less, preferably 50 mg / mL. It may be not more than mL, more preferably not more than 45 mg / mL.

  Since some protein molecules in the platelet suspension have an effect of stabilizing the platelets, the storage stability of the platelets is reduced by removing the protein molecules. For this reason, it is preferable to use a liquid suitable for the storage and stabilization of platelets as the diluent used in the dilution step (a). For the same reason, it is preferable to use a liquid suitable for the preservation and stabilization of platelets as the washing liquid used in the washing step (c). The storage solution used in the collection step (d) is a liquid suitable for the stabilization of platelet storage as defined above. In the present invention, liquids having the same composition can be used as the diluent, the cleaning liquid, and the storage liquid. In other words, the preservation solution can be used as a diluent and a washing solution.

  The preservation solution is not particularly limited, but M-sol, G-sol, bicarbonated Ringer's solution (Bikanate Infusion (registered trademark)), a solution obtained by adding ACD-A solution to physiological saline, and the like are preferably used. M-sol is, for example, 180 mL of Ringer's acetate solution (Solaceto F (registered trademark)), 30 mL of ACD-A solution, 12 mL of sodium hydrogen carbonate (Meiron (registered trademark)), 0.75 mL of 0.5 M magnesium sulfate, and JP It can be prepared by mixing 17.25 mL of water. G-sol can be prepared, for example, by mixing 250 mL of glucose-acetated Ringer's solution, 75 mL of ACD-A solution, 20 mL of sodium bicarbonate (Meylon (registered trademark)), and 250 mL of distilled water for injection into Japan.

  When the preservation solution contains bicarbonate, bubbles are generated from the preservation solution. When air bubbles are mixed into the hollow fiber membrane module, platelets aggregate and the platelet recovery rate tends to decrease. Therefore, it is preferable to provide a filter or an air chamber for preventing air bubbles from entering the liquid feed line to the hollow fiber membrane module. Moreover, when performing liquid feeding with a roller pump, since generation | occurrence | production of a bubble is induced by a roller, it is preferable to provide the filter and air chamber which prevent bubble mixing in the downstream of a roller pump.

  In order to suppress platelet aggregation, it is preferable to add an aggregation inhibitor in the dilution step (a). Although not particularly limited, citrate, EDTA salt, heparin and the like are preferably used as the aggregation inhibitor. When diluting solution is merged into the circuit that sends the platelet suspension before filtration to the hollow fiber membrane module and the dilution step (a) is performed, the platelet suspension is sent to the module in the same manner as the dilution solution. The liquid containing the aggregation inhibitor may be merged in the circuit.

  The filtration step (b) is performed by whole volume filtration as described above. With the tube clamp 17 disposed downstream of the washed platelet outlet 7 closed, the washed platelet outlet 7 closed, and the filtrate outlet 8 opened, the diluted platelet suspension is poured into the module. That's fine.

  In the conventional method, in the process of filtering the platelet suspension, the platelets clog the surface of the hollow fiber membrane and the filtration pressure rises. As the filtration pressure rises, excessive physical pressure is applied to the platelets. Platelet aggregation occurs and clogging progresses further. When platelets aggregate, they adhere to the surface of the hollow fiber membrane. For this reason, even if an attempt is made to collect the platelets by flowing a storage solution through the module, the platelets remaining on the surface of the hollow fiber membrane without being collected increase, and the platelet collection rate decreases. In addition, in the case of the internal pressure type in which the platelet suspension is passed through the hollow part of the hollow fiber membrane as the inflow side space, the aggregated platelets block the hollow part. And the recovery rate of platelets decreases. In particular, since the platelet suspension used as a raw material generally has a platelet concentration three times or more that in the body, clogging is likely to occur during filtration.

  In order to suppress clogging and increase the recovery rate of platelets by filtering the platelet suspension by the total amount filtration method, it is necessary to maintain a state in which the filtration pressure is low and platelet aggregation is suppressed. By reducing the flow rate of (b), filtration pressure can be suppressed and platelet aggregation can be suppressed.

  As a result of experiments, the optimum flow rate in the filtration step (b) was found. Specifically, in the filtration step (b), the maximum flow rate (mL / min) / water permeability performance of the hollow fiber membrane module (mL / kPa / min) is preferably 0.15 kPa or less, more preferably 0.11 kPa or less. . The water permeation performance of the hollow fiber membrane module can be calculated by Equation 2 described in the following examples.

  Also, in the filtration step (b), by reducing the number of platelets relative to the membrane area of the hollow fiber membrane, the number of platelets clogging the hollow fiber membrane is reduced, the filtration pressure is lowered, and the platelet recovery rate is increased. be able to.

As a result of experiments, the total number of platelets relative to the membrane area of the optimum hollow fiber membrane in the filtration step (b) was found. Specifically, the total platelet count / membrane area value subjected to the filtration treatment is preferably 6 × 10 ¹¹ cells / m ² or less.

  “Membrane area” as used herein refers to the area of the surface that comes into contact with the platelet suspension and is the effective membrane area at the time of filtration, excluding the portion where the pores of the membrane are filled with potting material. Say. In the hollow fiber membrane module for internal pressure type, it is the membrane area based on the inner diameter of the hollow fiber membrane (the area of the membrane surface on the hollow fiber membrane lumen side), and in the hollow fiber membrane module for external pressure type, it is outside the hollow fiber membrane. This is the diameter-based membrane area (the area of the outer surface of the hollow fiber membrane). The membrane area can be calculated by Equation 1 described in the following examples.

  Further, the total platelet count to be subjected to the filtration treatment is the total number of platelets contained in the platelet suspension used as a raw material. For example, in the device shown in FIG. 5 or FIG. The total number of platelets. The total platelet count can be calculated by measuring the platelet count per unit volume with a multi-item automatic blood cell counter XT1800i (manufactured by Sysmec) and multiplying by the volume of the platelet suspension.

  In order to suppress platelet aggregation and increase the platelet recovery rate, the maximum pressure of the filtration pressure in the filtration step (b) is preferably 30 kPa or less, and more preferably 20 kPa or less. By reducing the flow rate during filtration, the filtration pressure can be lowered. Since the filtration pressure increases with time in the filtration step (b), the flow rate may be reduced during the filtration step so as not to exceed the maximum pressure as the filtration pressure increases.

  In the filtration step (b), the filtrate permeates the filtration side space, so that platelets are concentrated in the inflow side space. When platelets are concentrated, the interaction between platelets becomes stronger and it tends to aggregate, and in particular, the platelet suspension that is the raw material for washed platelets is generally concentrated more than 3 times in the body, It tends to aggregate more.

As a result of experiments, an optimum concentration ratio in the filtration step (b) was found. Specifically, in the filtration step (b), the platelet concentration ratio is preferably 6 times or less, more preferably 3 times or less. The concentration ratio is the ratio of the platelet concentration of the platelet suspension before dilution to the average concentration of platelets in the inflow side space in the filtration step (b). The concentration ratio can also be calculated by dividing the amount of platelet suspension before dilution by the volume of the inflow side space of the hollow fiber membrane module. The platelet suspension used as a raw material is often a suspension containing 10 units of platelets. According to the standard, the platelet concentration is 1.9 × 10 ⁹ cells / mL or more and less than 8.3 × 10 ⁸ cells / mL. Is 160 mL or more and less than 240 mL.

  On the other hand, if the concentration ratio is too low, the removal rate of contaminants such as protein molecules decreases, resulting in an increase in the amount of the cleaning solution in the cleaning step (c). Therefore, in the filtration step (b), the platelet concentration ratio is preferably 1.1 times or more, and more preferably 1.3 times or more.

  As another method, the concentration ratio can be lowered by increasing the volume of the inflow side space with respect to the amount of the raw material platelet suspension. To reduce the concentration ratio, the series of platelet suspension treatment is divided into two or more times (for example, 10 units of platelet treatment is divided into two or more times), and the resulting platelet suspension is mixed. Also good.

  In the filtration step (b), stress due to shear is applied to the platelets due to contact with the surface of the hollow fiber membrane. The shear stress applied to the platelets is proportional to the linear velocity flowing through the hollow fiber membrane module. For this reason, by lowering the linear velocity, platelet aggregation can be suppressed and the platelet recovery rate can be increased. In the total volume filtration using the hollow fiber membrane module, the linear velocity of the liquid flowing in the inflow side space of the hollow fiber membrane module is determined by the inlet point (for example, internal pressure type) where the platelet suspension introduced into the module first contacts the membrane. In this case, the maximum value is at the inlet portion of the hollow fiber membrane closest to the platelet suspension flow inlet, and the amount of liquid is reduced by filtration, so that it decreases in the longitudinal direction. Therefore, the platelet recovery rate can be increased by controlling the linear velocity at the entrance point as described above. In the present invention, this linear velocity at the inlet point is referred to as “linear velocity at the inlet of the hollow fiber membrane module” or simply “linear velocity at the inlet”. On the other hand, when the linear velocity is low, the processing time becomes long, and the platelets are likely to stay long in the state where the platelets are concentrated in the inflow side space in the filtration step (b).

  As a result of experiments, the optimum inlet linear velocity in the filtration step (b) was found. Specifically, in the filtration step (b), the linear velocity at the inlet of the hollow fiber membrane module is preferably 2 cm / min or more, and more preferably 5 cm / min or more. On the other hand, the linear velocity at the inlet of the hollow fiber membrane module is preferably 150 cm / min or less, and more preferably 60 cm / min or less. The linear velocity at the inlet can be calculated by dividing the flow rate flowing through the hollow fiber membrane module by the cross-sectional area of the inflow side space in a cross section viewed perpendicularly to the longitudinal direction of the hollow fiber membrane module.

  The washing step (c) is performed after the filtration step (b). Similar to the filtration step (b), the washing solution may be poured into the module with the washing platelet outlet 7 closed and the filtrate outlet 8 opened. As the cleaning liquid, the preserving liquid used in the recovery step (d) can be used. The flow rate (mL / min) of the washing solution may be approximately the same as the flow rate of the platelet suspension in the filtration step (b).

  In order to efficiently recover platelets pressed against the hollow fiber membrane in the recovery step (d), a flow parallel to the hollow fiber membrane is effective, and without filtering the hollow fiber membrane module (ie, It is preferred to flow the preservation solution (at a pressure that does not allow the preservation solution to permeate the membrane). For example, the preservation solution may be poured from the platelet suspension inlet 6 with the filtrate outlet 8 closed and the washed platelet outlet 7 open.

  For the purpose of shortening the entire processing time, a part or all of the recovery step (d) may be performed simultaneously with the cleaning step (c). In that case, the preservation solution may be flowed by a cross flow method in which the preservation solution is simultaneously flowed in two directions, ie, a liquid flow perpendicular to the surface of the hollow fiber membrane and a parallel liquid flow.

  The total amount filtration method of the hollow fiber membrane module includes an internal pressure filtration that performs filtration from the hollow portion of the hollow fiber membrane toward the outside, and an external pressure filtration that performs filtration from the outside of the hollow fiber membrane toward the hollow portion. However, in the present invention, in the filtration step (b), it is preferable to use internal pressure filtration in which speed unevenness is less likely to occur and platelet retention is less likely to occur.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

(1) Measurement of water permeation performance The water permeation performance of the hollow fiber membrane module is measured by measuring the water permeation performance per membrane area of the hollow fiber membrane cut out from the hollow fiber membrane module, and the membrane of the hollow fiber membrane incorporated in the hollow fiber membrane module. Calculated by multiplying the area. First, the water permeability per membrane area can be measured by the following method. A hollow fiber membrane built in the hollow fiber membrane module was cut out, the hollow fiber membrane was inserted into a plastic tube, and both ends of the hollow fiber membrane were potted on the inner walls of both ends of the plastic tube to produce a mini module with an effective length of 10 cm. . “Effective length” refers to the length of the portion that functions effectively as a separation membrane. The portion that functions effectively during filtration, excluding the portion where the pores of the membrane are filled with a potting agent, etc. The length of the thread membrane. 5 and 6, the effective length is indicated as L. The number of hollow fiber membranes was adjusted so that the membrane area of the minimodule was 0.003 m ² . The membrane area is the membrane area based on the inner diameter when the hollow fiber membrane module is used in the internal pressure type, and the membrane area based on the outer diameter when the hollow fiber membrane module is used in the external pressure type. The membrane area of the mini module was calculated by the following formula 1.

A _mini = D × π × L × n ・ ・ ・ Equation 1
A _mini : Mini module membrane area (m ² )
D: Hollow fiber diameter (m) (inner diameter for internal pressure type, outer diameter for external pressure type)
π: Pi ratio
L: Effective length (m)
n: Number of hollow fiber membranes

A water pressure of 1.3 × 10 ⁴ Pa was applied to the manufactured minimodule, and the amount of water per unit time flowing out to the surface side where the filtrate of the hollow fiber membrane was obtained was measured. When the hollow fiber membrane module is used with internal pressure, the water pressure is applied to the mini module with internal pressure. When the hollow fiber membrane module is used with external pressure, the mini module is external with pressure. Water pressure was applied. The water permeability of the hollow fiber membrane was calculated according to the following formula 2. As a result, the water permeability of the hollow fiber membrane used in the following production example was 76 mL / hr / Pa / m ² .

F _M = Q / (T × P × A _mini ) Equation 2
F _M : Water permeability of hollow fiber membrane (mL / hr / Pa / m ² )
Q ： Amount of water flowing out (mL)
T: Time when water pressure is applied (hr)
P: Water pressure (Pa)
A _mini : Mini module membrane area (m ² )

  Next, the membrane area of the hollow fiber membrane module was calculated by Formula 3, and the water permeability of the hollow fiber membrane module was calculated by Formula 4 below.

A _MD = D × π × L × n Equation 3
A _MD : Membrane area of the hollow fiber membrane module (m ² )
D: Hollow fiber diameter (m) (Inner diameter for internal pressure type. Outer diameter for external pressure type)
π: Pi ratio
L: Effective length (m)
n: Number of hollow fiber membranes

F _MD = F _M × A _MD・ ・ ・ Formula 4
F _MD : Water permeability of hollow fiber membrane module (mL / Pa / hr)
F _M : Water permeability of hollow fiber membrane (mL / hr / Pa / m ² )
A _MD : Membrane area of the hollow fiber membrane module (m ² )

(2) Protein concentration measurement The protein concentration measurement was performed by BCA method using BCA PROTEIN ASSAY KIT (manufactured by THERMO SCIENTIFIC). As a measurement sample, platelet suspension or washed platelets were centrifuged at 10,000 × g for 20 minutes, and the supernatant was used. For measurement, a BCA reagent and a calibration curve sample were prepared first. For sample dilution, M-sol, which is a stock solution used for the production of washed platelets, was used. According to the specification of the kit, the BCA reagent was added to the sample for the calibration curve or the measurement sample, and stirred at room temperature for 30 seconds using a micromixer. Then, it incubated for 30 minutes at 37 degreeC. After the sample was lowered to room temperature, the absorbance of the sample at a wavelength of 562 nm was measured. The wavelength at which the absorbance is measured need not be exactly the same, but may be in the vicinity of the wavelength around ± 20 nm. The protein concentration of the measurement sample was determined by drawing a calibration curve of protein concentration and absorbance from the calibration curve sample and substituting the absorbance of the measurement sample into the equation of the calibration curve.

(3) Production example 1 of hollow fiber membrane module
A mixture of 15 parts Udel (R) polysulfone (P3500; Solvay), 8 parts polyvinylpyrrolidone (PVP) (K90; ISP), 75 parts dimethylacetamide (DMAC) and 2 parts water, A solution prepared by mixing and dissolving at 50 ° C. and then keeping it at 50 ° C. was used as a film forming stock solution. Further, a core solution was prepared by adding 30 parts of PVP (K30; ISP) to a mixed solution composed of 80 parts of DMAC and 20 parts of water and mixing and dissolving them.

  Using an orifice-type double-cylindrical die with an outer diameter of 1.0 mm and an inner diameter of 0.7 mm, the film-forming stock solution is discharged simultaneously from the outer cylinder, and the core liquid is discharged simultaneously from the inner cylinder. After passing through the dry part of the product, it is immersed in a 90 ° C coagulation bath containing a mixed solution consisting of 85 parts of water and 15 parts of DMAC, and further washed with warm water in an 80 ° C hot water bath and then dried. The film was wound around a frame to obtain a wet hollow fiber membrane. When the film forming speed was 40 m / min, the inner diameter of the hollow fiber membrane was 300 μm, and the film thickness of the hollow fiber membrane was 80 μm.

  The obtained wet hollow fiber membrane was cut into 0.4 m lengths, subdivided, immersed in a 90 ° C warm water bath for 50 minutes and washed with warm water, and then subjected to a drying treatment at 100 ° C for 10 hours, A heat-crosslinking treatment was performed at 170 ° C. for 5 hours with a dry heat dryer to obtain a hollow fiber membrane.

  A hollow fiber membrane module was produced from the obtained hollow fiber membrane as follows. First, in a cylindrical case with an inner diameter of 44 mm and a length of 290 mm, a plastic discharge module is provided at a location where the filtrate outlet is 21 mm from the case end surface, that is, 7% from the case end surface to the end surface length. A bundle of 5,000 hollow fiber membranes obtained by the above membrane forming operation was inserted, and the ends were sealed with a potting agent made of polyurethane resin to provide partition walls, and the hollow fiber membranes at the ends faced outwards on both sides. Cut the potting agent in a direction parallel to the cross section of the case so that it opens, attach a 6.4 mL header with a platelet suspension inlet at the end of the case far from the filtrate outlet, and wash the other side. A cylindrical header with a volume of 6.4 mL with a platelet outlet was attached. A hollow fiber membrane with an effective length of 255 mm is filled in a case containing a hollow fiber membrane with a 1000 ppm VA64 1000 ppm aqueous solution in which ethanol is dissolved, irradiated with 25 gGy from the outside of the case, and subjected to radiation irradiation crosslinking treatment. A membrane module production example 1 was obtained. The inflow side space in Production Example 1 is a space surrounded by a header and a partition wall having a platelet suspension flow inlet, a space surrounded by a header and a partition wall having a washed platelet outlet, and a space in the hollow portion of the hollow fiber membrane, Used for internal pressure type.

The water permeability of Production Example 1 was measured by the method (1). The hollow fiber membrane inner diameter cross-sectional area of Production Example 1 (cross-sectional area of the inflow side space) was 3.5 cm ² . Membrane area was 1.2m ^2. The sum of the volume of the space surrounded by the header and the partition and the hollow part of the hollow fiber membrane (volume of the inflow side space) was 101 mL. The water permeability of the hollow fiber membrane module was 91 mL / Pa / hr.

(4) Production example 2 of hollow fiber membrane module
Production Example 2 of a hollow fiber membrane module having an effective length of 255 mm was produced in the same manner as in Production Example 1 except that the case inner diameter was 19 mm, the header volume was 1.2 mL, and the number of inserted yarns was 1000.

The inner diameter cross-sectional area of the hollow fiber membrane of Production Example 2 (the cross-sectional area of the inflow side space) was 0.7 cm ² . Membrane area was 0.24m ^2. The sum of the volume of the space surrounded by the header and the partition and the hollow part of the hollow fiber membrane (volume of the inflow side space) was 23 mL. The water permeability of the hollow fiber membrane module was 18 mL / Pa / hr.

Example 1
For Preparation Example 1, washed platelets were produced by flowing 10 units of platelet suspension. Ten units of platelet suspension contained 2.0 × 10 ¹¹ or more and less than 3.0 × 10 ¹¹ platelets, and the liquid volume was about 200 mL. The number of platelets in the platelet suspension was measured with a multi-item automatic blood cell counter XT1800i (manufactured by Sysmec). Further, the protein concentration of the platelet suspension was measured by the method (2).

  Terumo Solaceto F 746.2mL, Otsuka Pharmaceutical Meylon 52.2mL, Terumo ACD-A solution 126.8mL, Otsuka Pharmaceutical Mg correction solution (1mEq / mL) 3.2mL, and Otsuka Pharmaceutical distilled water 71.6 mL was added and mixed to prepare M-sol as a stock solution.

  The inside of the hollow fiber membrane module of Production Example 1 was replaced with M-sol. As a dilution step (a), the platelet suspension was diluted with twice the amount of M-sol, and then 1/10 of the ACD-A solution was added (addition of an aggregation inhibitor). The diluted platelet suspension was sampled and the protein concentration was measured by the method (2). The inside of the circuit tube was made liquid-tight with M-sol and connected to the platelet suspension inlet of the hollow fiber membrane module. In the circuit tube, an air chamber having a capacity of 13 mL was installed between the roller pump and the hollow fiber membrane module. In the filtration step (b), the washed platelet outlet is closed, the filtrate outlet is opened, and the platelet suspension is introduced at a flow rate of 50 mL / min from the platelet suspension inlet of the hollow fiber membrane module. Filtration was performed, and the filtrate consisting of contaminants such as protein molecules and water was discharged. The pressure at the platelet suspension inlet and the filtrate outlet at the hollow fiber membrane module were measured. After flowing the whole amount of the platelet suspension, as a washing step (c), 1000 mL of M-sol was flowed at 50 mL / min through the same route. Next, as the recovery step (d), the filtrate outlet is closed, the washed platelet outlet is opened, and 200 mL of M-sol is flowed into the hollow portion of the hollow fiber membrane at 250 mL / min, and washed from the washed platelet outlet. Platelets were drained. The platelet concentration and protein concentration of the obtained washed platelets were measured by the methods (1) and (2).

  Further, the protein removal rate was calculated from Formula 5 and the platelet recovery rate was calculated from Formula 6 from the concentration and amount of platelet suspension and washed platelets.

Protein removal rate (%) = (1− (Co1 × Vo) / (Ci1 × Vi)) × 100 Equation 5
Co1: Protein concentration of washed platelets (mg / mL)
Ci1: Protein concentration in platelet suspension (mg / mL)
Vo: Washed platelet volume (mL)
Vi: Volume of platelet suspension (mL)

Platelet recovery rate (%) = (Co2 × Vo) / (Ci2 × Vi)) Equation 6
Co2: Platelet concentration of washed platelets (pieces / mL)
Ci2: Platelet concentration in platelet suspension (pieces / mL)
Vo: Washed platelet volume (mL)
Vi: Volume of platelet suspension (mL)

The protein concentration after dilution was 18 mg / mL. The total platelet count of the treated platelet suspension was 2.5 × 10 ¹¹ . In filtration step (b), the flow rate / module permeability is 0.033 kPa, the platelet concentration ratio is 1.98 times, the total platelet count / membrane area is 2.1 × 10 ¹¹ / m ² , and the inlet linear velocity is The maximum filtration pressure was 1.5 kPa. Platelet recovery was 98.0% and protein removal was 98.5%.

  By reducing the protein concentration by dilution and filtering the total amount by adjusting the flow rate with respect to the water permeability of the module, platelet aggregation was suppressed, and the protein removal rate and the platelet recovery rate were increased. The results are shown in Table 1 as Example 1.

(Example 2)
The same experiment as in Example 1 was performed except that the flow rate in the filtration step (b) was 150 mL / min. The protein concentration after dilution was 19 mg / mL. The total platelet count of the treated platelet suspension was 2.6 × 10 ¹¹ . In filtration step (b), the flow rate / module permeability is 0.099 kPa, the platelet concentration ratio is 1.98 times, the total platelet count / membrane area is 2.2 × 10 ¹¹ / m ² , and the inlet linear velocity is The maximum filtration pressure was 5 kPa. Platelet recovery was 84.0% and protein removal was 97.5%. The results are shown in Table 1 as Example 2.

(Example 3)
The same experiment as in Example 1 was performed except that the dilution ratio in the dilution step (a) was 1.5 times. The protein concentration after dilution was 40 mg / mL. The total platelet count of the treated platelet suspension was 2.5 × 10 ¹¹ . In filtration step (b), the flow rate / module permeability is 0.033 kPa, the platelet concentration ratio is 1.98 times, the total platelet count / membrane area is 2.1 × 10 ¹¹ / m ² , and the inlet linear velocity is The maximum filtration pressure was 4.0 kPa. Platelet recovery was 94.1% and protein removal was 98.2%. The results are shown in Table 1 as Example 3.

(Comparative Example 1)
The same experiment as in Example 1 was performed except that the dilution step (a) was not performed. The protein concentration in the platelet suspension was 56 mg / mL. The total platelet count of the treated platelet suspension was 2.5 × 10 ¹¹ . In filtration step (b), the flow rate / module permeability is 0.033 kPa, the platelet concentration ratio is 1.98 times, the total platelet count / membrane area is 2.1 × 10 ¹¹ / m ² , and the inlet linear velocity is The maximum filtration pressure was 4.0 kPa. Platelet recovery was 78.1% and protein removal was 97.7%. Since the protein concentration was high, platelet aggregation occurred and the platelet recovery rate was low. The above results are shown in Table 1 as Comparative Example 1.

(Comparative Example 2)
The same experiment as in Example 1 was performed except that the flow rate in the filtration step (b) was set to 580 mL / min. The protein concentration after dilution was 18 mg / mL. The total platelet count of the treated platelet suspension was 2.6 × 10 ¹¹ . In the filtration step (b), the flow rate / module permeability is 0.38 kPa, the platelet concentration ratio is 1.98 times, the total platelet count / membrane area is 2.2 × 10 ¹¹ / m ² , and the inlet linear velocity is The maximum filtration pressure was 25 kPa. Platelet recovery was 60.8% and protein removal was 98.1%. Platelet recovery was low due to the large flow rate for module permeability. The above results are shown in Table 1 as Comparative Example 2.

(Comparative Example 3)
The same experiment as in Example 1 was performed except that the hollow fiber membrane module obtained in Production Example 2 of the hollow fiber membrane module was used. The protein concentration after dilution was 18 mg / mL. The total platelet count of the treated platelet suspension was 2.2 × 10 ¹¹ . In the filtration step (b), the flow rate / module permeability is 0.17 kPa, the platelet concentration ratio is 8.7 times, the total platelet count / membrane area is 9.2 × 10 ¹¹ / m ² , and the inlet linear velocity is The maximum filtration pressure was 32 kPa. Platelet recovery was 32.0% and protein removal was 98.2%.

The flow rate with respect to the module water permeability was large, the platelet concentration ratio was high, and the number of platelets with respect to the membrane area was large. Therefore, the filtration pressure was high and the platelets aggregated, resulting in a low platelet recovery rate.
The results are shown in Table 1 as Comparative Example 3.

  The present invention is capable of removing contaminants such as protein molecules at a high rate from the platelet suspension without reducing the total platelet count, and washing platelets with a low total protein amount and a high total platelet count. Can be manufactured.

DESCRIPTION OF SYMBOLS 1 Hollow fiber membrane module for internal pressure type 2 Cylindrical member 3 Header 4 Header 5 Hollow fiber membrane 6 Platelet floating liquid inflow port 7 Washing platelet outflow port 8 Filtrate discharge port 9 Bulkhead 10 Bulkhead 11 Inflow side space 12 Filtration side space 13 Hollow Thread membrane hollow part 14 Hollow fiber membrane module for external pressure type 15 Air chamber 16 Roller pump 17 Tube clamp

Claims (6)

(A) a dilution step for diluting the platelet suspension;
(B) In the inflow side space of the hollow fiber membrane module in which the inflow side space in which the liquid that does not permeate the hollow fiber membrane flows and the filtration side space in which the liquid that has permeated the hollow fiber membrane flow are separated by the hollow fiber membrane, A filtration step of removing the protein molecules in the platelet suspension by introducing the platelet suspension diluted in the dilution step (a), filtering the whole amount by a filtration method, and allowing the protein molecules to pass through the filtration side space;
(C) a washing step of introducing a washing solution into the inflow side space and removing protein molecules remaining in the inflow side space; and (d) introducing a preservation solution into the inflow side space and presenting platelets in the inflow side space. A method for producing washed platelets, comprising a recovery step of recovering
The dilution step (a) includes diluting the protein concentration in the platelet suspension to 55 mg / mL or less,
The method in which the value of the maximum flow rate / water permeability performance of the hollow fiber membrane module in the filtration step (b) is 0.15 kPa or less.   The method according to claim 1, wherein a concentration ratio of platelets in the filtration step (b) is 1.1 times or more and 6 times or less. The method according to claim 1 or 2, wherein the total platelet count / membrane area subjected to the filtration treatment in the filtration step (b) is 6 × 10 ¹¹ cells / m ² or less.   The method according to any one of claims 1 to 3, wherein a linear velocity at an inlet of the hollow fiber membrane module in the filtration step (b) is 2 cm / min or more and 150 cm / min or less.   The method according to any one of claims 1 to 4, wherein the filtration step (b) is performed by internal pressure filtration.   The method according to any one of claims 1 to 5, wherein a maximum filtration pressure in the filtration step (b) is 30 kPa or less.