SYSTEM FOR THE SELECTIVE REMOVAL OF A TARGET SUBSTANCE FROM A BIOLOGICAL LIQUID

Description

[0001] The present invention relates to a system for treating a biological fluid such as blood or a blood component by selective removal of a target substance, and to a method for treating a biological fluid using such a system.

[0002] It is typically applied to the processing of biological fluids, particularly blood, blood components, or blood products intended for transfusion to a patient, and in cases where the target substance includes viruses, proteins such as prion proteins, bacteria, parasites, cells such as leukocytes, tumor or cancer cells, toxins, surface or circulating antigens, antibodies, or endogenous or exogenous substances such as exogenous substances used in a pathogen inactivation process. It is particularly applicable to the selective removal of anti-A and / or anti-B antibodies from blood or plasma.

[0003] A filtration unit for the selective removal of a target substance from blood, comprising particles with an affinity for the target substance, is known from document WO2007 / 042644. These spherical particles have, in particular, an average diameter between 20 and 150 µm and are held in the filtration unit between two layers of non-woven fabric having an average pore diameter of less than 8 µm.

[0004] US patent US7700746 describes a filtration column used to reduce the amount of anti-A and anti-B antibodies in whole blood or blood plasma. The column includes particles linked, via a spacer, to a saccharide such as a blood group A or B marker. For blood filtration, the particles are between 100 and 250 µm in size and are held within the column by a membrane with a porosity between 30 and 100 µm.

[0005] In this type of particle device, it is important to ensure that the particles do not contaminate the filtered fluid. The devices described above are suitable for purifying blood using particles with a calibrated size greater than approximately 20 µm, but are not suitable when the average particle size is less than approximately 15 µm or when the particle size distribution is such that a significant proportion of particles, for example 10%, are smaller than 15 µm. Using a material with lower porosity to constrain these small particles in such devices risks impeding the proper flow of the fluid through the devices and / or altering the quality of the biological fluid by retaining components of interest.

[0006] US patent application 2012 / 0219633 describes a system for the sequential removal of immunoglobulins and leukocytes from the blood. The system comprises a bag containing particles that bind to the immunoglobulins and a porous, fibrous filter for leukocyte retention. The particles are retained by a mesh or sieve bag, that is, a material with large openings, formed from a network of metallic or plastic wires, similar to a net. For example, the particles are retained by a polyethylene sieve with 35-40 µm openings. The openings in these sieves are too large to retain leukocytes.

[0007] The invention proposes a system for the selective removal of a target substance present in the blood or a blood component using particles that can be small in size, in particular less than 15 µm, allowing the treatment in a reasonable time of blood volumes of up to two liters, preserving the biological properties of the blood while ensuring that the treated blood is free of particles.

[0008] To this end and according to a first aspect, the invention proposes a system for treating a biological fluid such as blood or a blood component by selectively removing a target substance, comprising a treatment bag provided with at least one inlet orifice and at least one outlet orifice, said treatment bag containing a set of particles having an affinity for the target substance, said set comprising small particles having a size of less than 15 µm, the system further comprising a barrier means for isolating said particles from the biological fluid, said barrier means being composed of at least one porous membrane made of a hydrophilic material, the pores of said membrane being calibrated to a size suitable for preventing the passage of said small particles, namely less than 3 µm.

[0009] According to a second aspect, the invention relates to a method for treating a biological fluid such as blood or a blood component by selectively removing a target substance using a system according to the first aspect, said system further comprising a transfer bag in fluidic communication or intended to be brought into fluidic communication with the treatment bag via a transfer tube, said method comprising: the introduction of the biological fluid to be treated into the treatment bag containing the set of particles having an affinity for said target substance, the contacting of said biological fluid with said set of particles for a sufficient time to bind the target substance to said particles, so as to obtain a mixture of treated biological fluid from which the target substance has been removed and particles bound or not to the target substance, the transfer of said mixture from the treatment bag to the transfer bag via the transfer tubing, the barrier means of said system preventing said set of particles from passing into the transfer bag, so as to obtain the biological fluid thus treated separated from said set of particles, and the collection of the biological fluid thus treated and separated from the set of particles in the transfer bag 7.

[0010] The attached drawings illustrate the invention: [Fig.1 [ ] schematically represents a treatment pocket of a system according to an embodiment of the invention in which the barrier means is freely arranged within said treatment pocket. Fig. 2 [ ] schematically represents a treatment pocket of a system according to another embodiment of the invention in which the barrier means is fixed in said treatment pocket. ] Fig. 3 [ ] schematically represents a system according to a particular embodiment including the treatment pocket of the figure 1 and a transfer pouch. Fig. 4 ] schematically represents a system according to another embodiment of the invention comprising a treatment bag, a transfer bag and a barrier means arranged in a filtering unit disposed between said treatment bag and said transfer bag.

[0011] According to a first aspect, the invention provides a system for treating a biological fluid by removing a target substance. The biological fluid is, in particular, blood or a blood component intended for transfusion. The blood component is, in particular, a red blood cell concentrate, platelet-rich plasma, platelet-poor plasma, or a platelet concentrate.

[0012] In some cases, it is necessary to remove a target substance from the blood or a blood component before transfusion to a patient.

[0013] For example, the target substance includes leukocytes, prion proteins, viruses, bacteria, parasites, fungi, or other pathogens.

[0014] In another example, the target substance is an anti-A and / or anti-B antibody. Removing anti-A and anti-B antibodies from a donor's plasma makes it compatible with patients of any blood type.

[0015] In yet another example, the target substance is a substance used to inactivate pathogens in the blood or a blood component. Such a substance is, for example, methylene blue, a psoralen derivative, or riboflavin.

[0016] The elimination of the target substance is total or partial, i.e. sufficient to suppress or reduce the infectious risk associated with infectious agents, and / or suppress or reduce the toxicity of the target substances, to a level acceptable for transfusion.

[0017] With reference to the drawings of figures 1 to 4, system 1 includes a treatment bag 2 having at least one inlet port 3 and at least one outlet port 4. This treatment bag 2 is intended to contain the biological fluid to be treated.

[0018] The treatment bag is made from two flexible sheets joined together around their perimeter to form an internal volume. This internal volume is sufficient to contain the fluid to be treated. For example, the treatment bag is configured to hold a quantity of biological fluid ranging from 20 ml to 2000 ml, specifically between 100 ml and 700 ml.

[0019] The treatment bag contains a set of five particles with an affinity for the target substance. The target substance is thus eliminated via these particles, which bind to it by affinity. The particles bound to the target substance are then separated from the biological fluid.

[0020] For example, the particles may have an affinity for one type of target substance. Alternatively, the particles may have an affinity for several target substances to allow for the simultaneous removal of multiple target substances from a biological fluid.

[0021] In one particular example, the particles comprise a mixture of particles having an affinity for anti-A antibodies and particles having an affinity for anti-B antibodies.

[0022] The particles include adsorbent particles, such as activated carbon, aluminum oxide, and silica. Alternatively, the particles are polymer-based, such as polystyrene, polycarbonate, cellulose, dextran, polymethacrylate, or polyacrylate.

[0023] In particular, these particles are treated physically and / or chemically to improve their specificity and / or affinity for the target substance(s).

[0024] More specifically, the particles are grafted with oligosaccharides, such as oligosaccharides capable of binding antibodies like anti-A and / or anti-B antibodies. For example, these particles are ultrafine cellulose particles grafted with an antigenic oligosaccharide of group A or B, such as those described in document WO2016 / 177967. In another example, the particles are those described in document EP3141558A1 or the IsoClear beads marketed by Prometic Bioseparations.

[0025] The set of particles contained in the treatment bag includes small particles with a size less than 15 µm.

[0026] In the first example, all the particles are small particles with an average size of less than 15 µm; more specifically less than 10 µm.

[0027] In another example, the particles have an average size greater than 15 µm, but some of the particles are small, namely less than 15 µm, specifically less than 10 µm.

[0028] The entire set of particles can be characterized by their particle size distribution. This measurement of particle size distribution is notably carried out using a laser diffraction particle size analyzer.

[0029] In particular, the set of particles includes 10% of particles with a size less than 15 µm, notably less than 10 µm.

[0030] The particles are generally substantially spherical, and their size corresponds to the diameter of the sphere. In the case where the particles are not spherical, their size corresponds to the equivalent diameter, that is, the diameter of the sphere of the same volume that would behave identically to the non-spherical particle during its retention.

[0031] In a particular example, the particles are ellipsoidal in shape with approximate dimensions of 2.2 µm by 8 µm. These particles are considered to have a size of approximately 2 µm.

[0032] The entire set of particles 5 is generally left free in the treatment pocket. In one variant, in order to prevent their agglomeration, the entire set of particles is impregnated or integrated into a textile layer such as a non-woven fabric, as envisaged in document WO2007 / 042644.

[0033] Depending on a particular embodiment, the quantity of particles varies from 1 to 10 mg / ml of biological fluid, in particular from 2 to 5 mg / ml of biological fluid.

[0034] According to the invention, the system further comprises a barrier means 6 which blocks the passage of particles but allows the passage of biological fluid.

[0035] This barrier means 6 is composed of at least one porous membrane made of a hydrophilic material, the pores of said membrane being calibrated to a size suitable for preventing the passage of said particles, namely less than 3 µm.

[0036] This porous membrane is flat and has a non-crosslinked structure, notably without any entanglement of threads, fibers or strands, nor a mesh-like structure. This porous membrane is manufactured, for example, by phase inversion.

[0037] The pores of the membrane have a size suitable for preventing the passage of said particles, that is to say that the size of the pores of the membrane is substantially smaller than the minimum size of the particles.

[0038] In particular, the porous membrane has a thickness between 90 µm and 150 µm.

[0039] In one particular embodiment, to ensure that the particle set does not include any particles smaller than the pores of the porous membrane, the particles are passed through a sieve with pores matching the size of the membrane pores. The particles that do not pass through the sieve constitute the particle set of the system for treating the biological fluid.

[0040] The membrane pores are specifically calibrated to a size less than or equal to 3 µm, and more specifically less than or equal to 1 µm. For example, the membrane pores are approximately 0.65 µm.

[0041] This membrane with a porosity of approximately 0.65 µm is advantageous in that it also allows for the simultaneous retention of cellular constituents such as leukocytes from blood plasma.

[0042] The membrane is made of a hydrophilic material chosen from among naturally hydrophilic materials or plastic-based materials made hydrophilic. Indeed, the hydrophilic nature of the material is important to ensure good hemocompatibility with blood or blood components.

[0043] For example, the hydrophilic material is chosen from polymers and / or copolymers based on polypropylene, polyester, polyamide, high or low density polyethylene, polyurethane, poly(vinylidene fluoride) or cellulose-based products such as cellulose acetate and its derivatives.

[0044] These polymeric products are generally not naturally hydrophilic and must be treated by physical or chemical methods to give them said hydrophilic properties.

[0045] These treatments include, for example, the grafting of hydrophilic substituents, such as hydroxyl or carboxylic groups, onto the polymer using known methods. Another treatment involves gaseous plasma treatment, particularly with oxygen.

[0046] In relation to figures 3 and 4The system further includes a transfer bag 7 in fluidic communication or intended to be put in fluidic communication with the treatment bag 2 via a transfer tube 8. This transfer bag 7 is intended to collect the treated biological fluid, depleted in target substance and free of particles.

[0047] The transfer tubing 8 is connected to the outlet port 4 of the treatment bag 2 and to an inlet port 9 of the transfer bag 7.

[0048] The barrier medium 6 is placed inside or outside the treatment pocket 2.

[0049] In a design depicted on the figures 1 to 3The barrier medium 6 is placed inside the treatment bag 2. In this case, the barrier medium is intended to retain the particles in the treatment bag 2. During the transfer of the treated biological fluid from the treatment bag 2 into the transfer bag 7, the particles 5 are confined in the treatment bag 2. The biological fluid collected in the transfer bag 7 is thus free of particles.

[0050] In a first configuration shown on the figure 1 , the barrier means 6 is in the form of a sachet 10 containing the particles 5, said sachet being composed of said porous membrane.

[0051] The porosity of the porous membrane forming the sachet is such that the particles 5 cannot exit the sachet 10 by passing through its walls, but the biological fluid can pass through it to come into contact with these particles 5.

[0052] The bag is made, for example, by assembling a double layer of porous membrane on the sides, or by assembling two membranes, one on top of the other, on the bottom and sides. The assembly is carried out using methods such as heat welding, high-frequency welding, or ultrasound.

[0053] In one variant, bag 10 is a double-walled bag, each wall being composed of the porous membrane. In this variant, the double-walled bag is produced, for example, by placing a first bag containing the particles inside a second bag, each of the first and second bags being composed of the porous membrane. Thus, if small particles escape from the first bag, they are retained by the porous membrane of the second bag.

[0054] In another variant, the bag 10 includes a first and a second peripheral seal located at a distance from each other. Thus, if one of the peripheral seals is defective, the other peripheral seal ensures the bag 10 remains airtight.

[0055] To ensure proper containment of particles in bag 10, the bag is a double-walled bag with a double weld seal.

[0056] On the figure 1 The bag 10 is sealed, meaning that the top of the bag is closed, notably by welding. The particles are then enclosed inside the bag 10.

[0057] The sachet 10 is advantageously loose in the treatment bag 2. Alternatively, it is fixed by one of its sides to one of the edges of the treatment bag 2.

[0058] In a variant of the configuration shown on the figure 2, the sachet 10 containing the particles 5 is arranged inside the treatment bag 2 and has an opening 11, said opening being in fluidic communication with the inlet orifice 3 of the treatment bag 2.

[0059] In this configuration, the biological fluid to be treated is introduced into the bag 10 of the treatment bag 2 to be brought into contact with the particles, then passes through the porous membrane forming the bag.

[0060] In another configuration not shown, the barrier means 6 is in the form of a wall composed of said porous membrane, said wall being arranged inside the treatment bag 2 so as to delimit an inlet compartment in fluidic communication with the inlet orifice 3 of the treatment bag and an outlet compartment in fluidic communication with the outlet orifice 4 of the treatment bag 2. The inlet compartment of the treatment bag 2 contains the particles 5.

[0061] Advantageously, the wall comprising the porous membrane is held in a sealed frame, which facilitates the assembly of the barrier medium 6 in the treatment pocket 2.

[0062] In another illustrated work on the figure 4 , the barrier means 6 is disposed outside the treatment pocket 2, on the flow path defined by the transfer tubing 8.

[0063] The barrier means 6, external to the treatment bag 2, is for example in the form of a filter unit 12, said filter unit containing a filtration medium composed of at least said porous membrane.

[0064] In this embodiment, the system includes a transfer bag 7 in fluidic communication with the treatment bag 2 via a transfer tube 8, said filter unit 12 being arranged on said transfer tube 8.

[0065] In this case, during the transfer of the biological fluid from the treatment bag 2 into the transfer bag 7, the particles 5 are retained by the barrier means 6 without reaching the transfer bag 7. Thus, the treated biological fluid collected in the transfer bag 7 is free of particles.

[0066] The filter unit 12 comprises a flexible, rigid, or semi-rigid casing, inside which the porous membrane forming the barrier medium 6 is arranged. The filter unit further includes an inlet port 13 and an outlet port 14, the filtration medium delimiting an inlet compartment in communication with the inlet port 13 and an outlet compartment in communication with the outlet port 14.

[0067] The filtration medium is advantageously retained in the filter unit by means of a flexible and airtight frame.

[0068] The filtration medium consists solely of one or more porous membranes.

[0069] Advantageously, the filtration medium further comprises one or more layers of a hydrophilic porous material to prevent clogging of the porous membrane and / or to filter other substances from the biological fluid.

[0070] Even more advantageously, the filtration medium is capable of removing leukocytes from the blood or a blood component.

[0071] In particular, the filtration medium further comprises upstream of the porous membrane(s), one or more layers of a hydrophilic porous material, each having an average pore size greater than the pore size of the porous membrane.

[0072] In particular, the hydrophilic porous material is a spun-bonded nonwoven or meltblown fiber.

[0073] For example, the filtration medium includes, upstream of the porous membrane, several layers of non-woven fabric with an average porosity between 8 and 12 µm.

[0074] Such a filtering unit is advantageously suited to further remove cellular components, such as leukocytes, from blood plasma. A specific example of such a filtering unit is described in document EP 0 953 361 A1.

[0075] In the case where the set of particles 5 binds the anti-A and / or anti-B antibodies of the blood plasma, the system comprising such a porous membrane finds an application for obtaining a universal leukoreduced plasma intended for transfusion.

[0076] According to a second aspect, a method for treating a biological fluid such as blood or a blood component by selectively removing a target substance using a system according to the first aspect of the invention is now described. The system further comprises a transfer bag 7 in fluidic communication with the treatment bag via a transfer tube 8.

[0077] The process includes: the introduction of the biological fluid to be treated into the treatment bag 2 containing the set of particles 5 having an affinity for said target substance, the contacting of said biological fluid with said set of particles 5 for a sufficient time to bind the target substance to said particles, so as to obtain a mixture of treated biological fluid from which the target substance has been removed and particles bound or not to the target substance, the transfer of said mixture from the treatment bag 2 to the transfer bag 7 via the transfer tubing 8, the barrier means 6 of said system preventing the set of particles from passing into the transfer bag, so as to obtain the biological fluid thus treated separated from said set of particles, and the collection of the biological fluid thus treated and separated from the set of particles in the transfer bag.

[0078] Biological fluid includes, in particular, blood previously taken from a donor or a blood component derived from blood taken from a donor and separated, for example, by filtration and / or centrifugation from other blood components.

[0079] In particular, in the case where all the particles have an affinity for anti-A and / or anti-B antibodies, the process is used to obtain a particle-free universal plasma, ready to be transfused.

[0080] Preliminary example: particle retention by a porous membrane

[0081] In order to test the ability of a porous membrane according to the invention to retain small particles, the following test was carried out.

[0082] A filter unit was constructed comprising a filtration medium consisting, from upstream to downstream, of: a layer of bonded spun polyester nonwoven fabric, four layers of melt-blown polypropylene nonwoven fabric, each with a surface mass of approximately 40 g / m² and an air permeability of approximately 110 l / m² / s, a layer of hydrophilic poly(vinylidene fluoride) membrane with a porosity of 0.65 µm, a layer of melt-blown polypropylene nonwoven fabric with a surface mass of approximately 40 g / m² and an air permeability of approximately 110 l / m² / s, and a layer of bonded spun polyester nonwoven fabric. The filtration surface area is approximately 20 cm².

[0083] A bag was filled with a suspension of 250 ml of water for injection and ultrafine cellulose particles (5 mg / ml), ellipsoidal in shape with an approximate size of 2.2 µm x 8 µm.

[0084] The contents of the bag were passed through the filter bag and the number of particles after filtration was determined using a particle counter in liquids. [Table 1]

[0085] Table 1 Volume of water analyzed Average particle number > 5 µm Average particle number > 10 µm Average particle number > 25 µm Poached 120 ml 87.86 per ml 7.64 per ml 0.08 per ml

[0086] These results are consistent with the American Pharmacopoeia (Volume 6, <788> Particulate matter in injections, USP 42, edition 2019, 6942-6946) and the European Pharmacopoeia (European Pharmacopeia 10.0, Section < 2.9.19 > Particulate contamination: Sub-Visible particles, 360-362, 04 / 2011: 20919) which stipulate that for injectable preparations with a volume greater than 100 ml, the following conditions must be met: [Table 2]

[0087] Table 2 Volume of the parenteral preparation Particle size Number of particles per ml US Pharmacopoeia Number of particles per ml EP Pharmacopoeia > 100 ml ≥ 10 µm 25 per ml 12 per ml ≥ 25 µm 3 per ml 2 per ml Example: elimination of anti-B antibodies from group O blood plasma Material

[0088] 750 mg of ultrafine cellulose particles grafted with a group B antigenic oligosaccharide, of ellipsoidal shape with an approximate size of 2.2 µm x 8 µm, were introduced into a PVC bag.

[0089] The filter bag used in this example is identical to the one described in the preliminary example above. Plasma treatment

[0090] Approximately 250 ml of group O plasma was obtained by centrifuging one unit of group O whole blood (approximately 500 ml). After introducing the plasma into the PVC bag containing the particles, the PVC bag was agitated horizontally for approximately 30 minutes, and then its contents were filtered by gravity through the filter bag. Analyses

[0091] Immunoglobulin G (IgG) and immunoglobulin M (IgM) antibody titers were determined in the initial plasma, i.e. before treatment, and in the final plasma, i.e. after filtration through the filter bag.

[0092] Antibody titer determination is performed by a direct agglutination test for IgM titration and an indirect agglutination test for IgG titration.

[0093] Plasma samples (initial and final) are diluted in PBS buffer, by successive dilution by a factor of 2 (1 / 1, 1 / 2, ..., 1 / 64) and brought into contact with erythrocytes of blood group B. The titer given corresponds to the last dilution where the agglutinates of red blood cells due to the presence of blood antibodies remain visible.

[0094] The results are shown below. [Table 3]

[0095] Table 3 Title Initial antibody titer Final antibody titer Titration gain IgM 1 / 128 1 / 2 6 IgG 1 / 64 1 / 2 5

[0096] Biochemical assays of plasma factors were also carried out. The results are shown in Table 4 below. [Table 4]

[0097] Table 4 Untreated plasma Plasma after filtration Factor Vc 58% 57% Factor VIIIc 31% 30% Factor XIc 85% 78% fibrinogen 2,91 g / l 2,78 g / l prothrombin 79% 79%

[0098] In this table, the concentrations of coagulation factors factor V, factor VIII, factor IX, and prothrombin are expressed as a percentage relative to a standard normal human plasma. The measurements are chronometric assays.

[0099] Filtration has no impact on the plasma factors tested: prothrombin, fibrinogen, Factor V, Factor VIII and Factor XI.

Claims

1. A system (1) for treating a biological fluid such as blood or a blood component by selective removal of a target substance, comprising a treatment bag (2) provided with at least one inlet orifice (3) and at least one outlet orifice (4), said treatment bag (2) containing a set of particles (5) having an affinity for the target substance, said set comprising small particles having a size of less than 15 µm, characterised in that the system further comprises a barrier means (6) composed of at least one porous membrane made of a hydrophilic material, the pores of said membrane being calibrated to a size suitable for preventing the passage of said small particles, namely less than 3 µm.

2. The system according to claim 1, characterised in that the hydrophilic material is selected from polymers and / or copolymers based on polypropylene, polyester, polyamide, high- or low-density polyethylene, polyurethane, polyvinylidene fluoride, or cellulose-based products such as cellulose acetate and its derivatives.

3. The system according to one of claims 1 to 2, characterised in that it further comprises a transfer bag (7) in fluid communication or intended to be put in fluid communication with the treatment bag (2) via a transfer tubing (8).

4. The system according to any one of claims 1 to 3, characterised in that the barrier means (6) is disposed inside the treatment bag (2).

5. The system according to claim 4, characterised in that the barrier means (6) is in the form of a pouch (10) enclosing said set of particles (5), said pouch (10) being composed of said porous membrane.

6. The system according to claim 5, characterised in that the pouch (10) is a double-walled pouch, each of the walls being composed of the porous membrane.

7. The system according to any one of claims 5 to 6, characterised in that the pouch (10) is sealed or has an opening (11), said opening (11) being in fluid communication with the inlet orifice (3) of the treatment bag (2).

8. The system according to claim 4, characterised in that the barrier means (6) is in the form of a wall composed of said porous membrane, said wall being arranged within the treatment bag (2) so as to delimit an inlet compartment in fluid communication with the inlet orifice (3) of the treatment bag (2) and an outlet compartment in fluid communication with the outlet orifice (4) of the treatment bag (2), said inlet compartment of the treatment bag (2) enclosing said set of particles (5).

9. The system according to claim 8, characterised in that the wall comprising the porous membrane is held in a sealed frame.

10. The system according to one of claims 1 or 2, characterised in that the barrier means (6) is in the form of a filter unit (12), said filter unit enclosing a filtration medium composed of at least said porous membrane.

11. The system according to claim 10, characterised in that it further comprises a transfer bag (7) in fluid communication with the treatment bag (2) via a transfer tubing (8), said filter unit (12) being arranged on the transfer tubing (8).

12. The system according to one of claims 10 or 11, characterised in that the filtration medium further comprises one or more layers of a hydrophilic porous material each having an average pore size greater than the average pore size of the porous membrane.

13. The system according to claim 12, characterised in that the hydrophilic porous material is a spunbonded non-woven fabric or a melt-blown fibre.

14. The system according to any one of claims 10 to 13, characterised in that the filtration medium is able to remove leukocytes from blood or a blood component.

15. A method for treating a biological fluid such as blood or a blood component by selective removal of a target substance using a system (1) according to any of claims 3 to 14, comprising the steps of: - introducing the biological fluid to be treated into the treatment bag (2) containing the set of particles (5) having an affinity for said target substance, - contacting said biological fluid with said set of particles (5) for a time sufficient to bind the target substance to said particles, so as to obtain a mixture of treated biological fluid from which the target substance has been removed and particles bound or not bound to the target substance, - transferring said mixture from the treatment bag (2) to the transfer bag (7) via the transfer tubing (8), the barrier means (6) of said system preventing said set of particles from passing into the transfer bag (7), so as to obtain the biological fluid thus treated separated from said set of particles, and - collecting the biological fluid thus treated and separated from the set of particles in the transfer bag (7).