Filtration unit for leukocyte apheresis of blood with a relief-perforated nonwoven fabric

Abstract

The invention relates to a filtration unit (1) intended to allow the leucocytapheresis of the blood or of a blood product, comprising an external pouch (2) provided with at least one inlet orifice (3) and with at least one outlet orifice (4), the pouch containing a porous element interposed between said orifices, said porous element comprising at least one leucocytapheresis medium (8) that works by adsorbing and / or by filtering out the leucocytes, and at least one layer of nonwoven (7) provided with a plurality of bumps, each of the bumps having a perforation passing through it in the heightwise direction to form a relief-perforated nonwoven layer.

Description

FILTRATION UNIT FOR BLOOD DELEUKOCYTATION COMPRISING A PERFORATED NON-WOVEN FABRIC WITH EMBOSSED TEXTURE

[0001] The invention relates to a filtration unit for removing leukocytes from blood or a blood component, a method for manufacturing said filtration unit comprising a layer of embossed perforated non-woven material, an extracorporeal leukoreduction method using such a unit and a bag system comprising such a unit.

[0002] The invention typically applies to the filtration of blood or a blood component, and more particularly to the removal of leukocytes from whole blood or a red blood cell concentrate.

[0003] Blood, or a blood component, after collection and separation (in the case of a component), is intended for transfusion to a patient in need. During this transfusion, it is well known that leukocytes are undesirable because they can cause troublesome and / or potentially dangerous reactions in the patient. Indeed, leukocytes increase the risk of immune rejection, such as graft-versus-host disease, and facilitate the transmission of infectious agents.

[0004] This is why it is recommended, or even required in some countries, to remove leukocytes from the blood or blood component prior to transfusion, and this within a given yield.

[0005] To date, the optimal solution for removing leukocytes is to filter the blood or blood component through a filtration unit equipped with a leukoreduction medium.

[0006] Such a leukoreduction medium comprises one or more layer(s) made of a polymer material and chosen to improve the leukoreduction rate, the recovery of blood components, the filtration time and / or the filtration selectivity.

[0007] Most leukoreduction media include layers of nonwoven fabric. A nonwoven fabric is defined as a manufactured sheet, consisting of a web or sheet of fibers oriented directionally or randomly, bonded by friction and / or cohesion, and / or adhesion, excluding paper and its derivatives. by weaving, knitting, tufting, sewing incorporating binding threads or filaments or felted by wet fulling, whether or not they are needle-punched.

[0008] These nonwovens are produced by melt spinning or direct spinning. Spun-bond nonwovens typically produce fibers with a diameter of less than 20 µm. Melt-blown fibers, produced using an extrusion blow molding technique, generally have a diameter of less than 5 µm. Spun-bond and melt-blown nonwovens therefore possess a relatively dense structure capable of retaining leukocytes through adsorption and / or surface filtration (or sieving).

[0009] In addition to a leukoreduction medium, filtration units also generally include a pre-filter designed to remove micro-aggregates. For example, in document EP 1 336 417, a polyester layer with a permeability between 1000 and 5000 L / m³ is used. 2 / s and a pore size of approximately 35 pm is arranged upstream of the leukoreduction medium.

[0010] Depending on the country and the practices of blood banks, blood components can be stored before filtration for up to 14 days, at 4°C or at room temperature, with or without an additive solution such as saline adenine glucose mannitol (SAGM).

[0011] Under these conditions, filtration times with filtration units of the type described in document EP 1 336 417 can increase to over an hour. These filtration units can also become clogged, causing filtration to stop and the blood component to be lost.

[0012] These cloggings and prolonged filtration times are mainly due to the presence of aggregates composed primarily of red blood cells, platelets, and fibrin gel. The size of these aggregates increases with storage time, ranging from 20 µm to 200 µm.

[0013] To eliminate these aggregates and retain leukocytes, US patent 4,923,620 proposes a filtration unit comprising three elements: a needle-punched cloth with a fiber diameter between 20 and 30 µm to remove gels and aggregates, two or more intermediate layers of melt-blown non-woven fibers to remove micro-aggregates, and several Final layers of melt-blown non-woven fibers are used to eliminate leukocytes; these fibers have a smaller diameter than the fibers in the intermediate layers. The needle-punched web contains an acrylic binder and is hot-compressed to reduce its pore size to approximately 50 µm.

[0014] Document EP 2 286 821 describes a filter material for removing aggregates comprising, on the one hand, short fibers having a density between 0.7 and 4 decitex (dtex) and a length between 1 and 80 mm, and on the other hand, a backing fabric comprising long spun-bond fibers. The short fibers have a three-dimensional structure and are entangled, notably by water jet, within the long fibers, so as to obtain a surface density between 10 and 80 g / m². 2 .

[0015] Document WO2013 / 110694 proposes the use of grooved fibers, including trilobed fibers from spun-bond or melt-blown technology, to remove aggregates, gels, cellular debris and other fragments from blood products.

[0016] Finally, document WO2015 / 197955 discloses a prefilter material for a blood leukocyte removal filter comprising a thermally bonded carded web made of at least two types of discontinuous fibers. This web has a structure sufficiently permeable to retain aggregates without risk of clogging while also having sufficient mechanical strength to be integrated into a filtration unit.

[0017] In addition, in the field of hygiene products, particularly feminine hygiene products, it is known to use a perforated non-woven material, such as that described in document GB 2 208 666, which improves the transfer of liquids to absorbent materials placed downstream of the perforated non-woven material.

[0018] The applicant identified that this type of perforated non-woven material could be used advantageously in blood filtration units to retain aggregates and other blood gels while significantly reducing the risk of clogging.

[0019] To this end, and according to a first aspect, the invention proposes a filtration unit intended to allow the leukoreduction of blood or a blood component, comprising an outer casing having at least one inlet orifice and at least one outlet orifice, the casing containing a porous element interposed between said orifices, said porous element comprising at least one leukoreduction medium by adsorption and / or filtration of leukocytes and at least one layer of non-woven fabric having a plurality of bumps, each of said bumps being traversed vertically by a perforation, so as to form a layer of perforated non-woven fabric in relief.

[0020] According to another aspect, the invention relates to a method for manufacturing a filtration unit according to the first aspect of the invention comprising - the formation of a layer of perforated non-woven fabric by embossing and piercing a layer of non-woven fabric between two rollers, at least one of which is equipped with a plurality of needles, so as to perforate the non-woven fabric by creating bumps around the perforations which are raised relative to the surface of the non-woven fabric, - 1'assembly of said layer of embossed perforated non-woven fabric with a leukoreduction medium so as to form a porous element, and - the arrangement of said porous element in an outer casing of a filtration unit

[0021] The invention also relates to an extracorporeal method for leukoreducing blood or a blood component comprising passing said blood or said blood component contained in a bag through a filtration unit according to the first aspect of the invention.

[0022] According to yet another aspect, the invention relates to a bag system for the leukoreduction of blood or a blood component comprising a filtrate collection bag connected, via tubing and at an inlet port, to an outlet port of a filtration unit according to the first aspect.

[0023] Other items and benefits will appear in the description that follows.

[0024] [Fig.1] represents a schematic view of a filtration unit according to the invention.

[0025] [Fig. 2] represents a scanning electron microscope photograph of a layer of spun bonded perforated nonwoven fabric in relief.

[0026] [Fig. 3] represents a scanning electron microscope photograph of a layer of meltblown fiber nonwoven, perforated in relief.

[0027] [Fig. 4] represents a schematic cross-sectional and profile view of a slice of embossed perforated non-woven material.

[0028] [Fig. 5] represents a schematic view of a pocket system comprising a filtration unit according to the invention.

[0029] [Fig. 6] represents the pore size distribution of a non-woven fabric before perforation.

[0030] [Fig. 7] represents the pore size distribution of the non-woven fabric in Fig. 6, after perforation.

[0031] [Fig. 8] represents the optical measurement of a bump on a raised perforated non-woven fabric.

[0032] The filtration unit according to the invention is intended to allow the leukoreduction of blood or a blood component.

[0033] Blood components include, in particular, red blood cell concentrates, platelet concentrates, plasma, platelet-rich or platelet-poor plasma, and the buffy coat. Red blood cell concentrates are generally obtained by gentle centrifugation of a unit of whole blood followed by extraction of the platelet-rich plasma layer. In one variation, red blood cell concentrates are obtained by hard centrifugation of a unit of whole blood followed by extraction of the platelet-poor plasma layer. These red blood cell concentrates are then referred to as "non-depleted in leukocytes and platelets." In another variation, red blood cell concentrates are obtained by hard centrifugation of a unit of whole blood followed by extraction of the buffy coat and the platelet-poor plasma layer. These red blood cell concentrates are then referred to as "depleted in leukocytes and platelets."

[0034] In relation to Figure 1, the filtration unit 1 comprises an outer casing 2 having at least one inlet orifice 3 and at least one outlet orifice 4, the casing 2 containing a porous element interposed between said orifices 3 and 4. The porous element forms a compartment with the casing 2. an inlet compartment 5 intended to receive the fluid to be filtered, said inlet compartment 5 being in communication with the inlet port 3, and an outlet compartment 6 intended to collect the filtrate, said outlet compartment 6 being in communication with the outlet port 4.

[0035] The outer casing 2 of the filtration unit is flexible, rigid or semi-rigid. For example, the casing is made of polycarbonate, polyvinyl chloride or a polyolefin, such as polypropylene, polyethylene or a polypropylene-based complex.

[0036] The direction of fluid flow in the filtration unit, from inlet 3 to outlet 4, allows us to define the terms "upstream" and "downstream" used in the description.

[0037] The porous element contains at least one leukoreduction medium 8 by adsorption and / or filtration of leukocytes.

[0038] According to the invention, the porous element further contains at least one layer of non-woven fabric 7 provided with a plurality of bumps 9, each of said bumps being traversed vertically by a perforation 10, so as to form a layer of perforated non-woven fabric in relief. Such a layer is illustrated in Figures 2 to 4.

[0039] Nonwoven fabrics consist of fibers entangled together, but which are neither woven nor knitted. Examples of nonwoven fabrics include meltblown fiber nonwovens and spun-bonded nonwovens.

[0040] The embossed perforated nonwoven fabric comprises thermoplastic fibers of a biocompatible polymer such as polyester, polypropylene, polyethylene, polyamide, cellulose, or blends of these polymers. In particular, the fibers are polyester fibers, notably polyethylene terephthalate.

[0041] The perforated bumps are produced by embossing and piercing the nonwoven fabric completely. For example, the embossed perforated nonwoven layer is manufactured by embossing and piercing a layer of nonwoven fabric between two rollers, at least one of which is equipped with a plurality of needles. In this way, the nonwoven fabric is perforated, creating bumps 9 around the perforations 10, which are raised above the surface of the nonwoven fabric. These bumps 9 are hollow and define the perforations. In particular, the bumps 9 have substantially all the same dimensions and are formed on the same side of the non-woven fabric.

[0042] Advantageously, embossed perforated nonwoven is a spunbond nonwoven that exhibits advantageous mechanical properties, particularly in terms of tensile strength. With this type of spunbond nonwoven material, it is possible to form higher and more stable bumps by embossing than with a meltblown fiber nonwoven.

[0043] In particular, the 9 bumps are truncated cone-shaped. The 9 bumps rise and taper from a surface of the non-woven fabric. Other three-dimensional shapes are possible.

[0044] The shape of the perforations corresponds substantially to the shape of the bumps. For example, in the case of a truncated conical bump, the perforation is truncated conical, and the proximal and distal openings of the perforation are substantially circular or elliptical. The terms "proximal" and "distal" refer to the surface of the nonwoven fabric.

[0045] The 9 bumps are separated from each other. They are distributed on the non-woven fabric in a regular or irregular manner. In particular, the 9 bumps form a distinct and repeating pattern on the non-woven fabric.

[0046] Figures 2 and 3 show a scanning electron microscope image of a raised perforated nonwoven, of spun bond type and of meltblown fibers, respectively.

[0047] Unexpectedly, this layer of embossed perforated non-woven fabric has a good capacity to retain aggregates and other gels present in the blood or the blood component being filtered, while preventing clogging. Furthermore, filtration times are reduced. Aggregates form during blood storage and are composed primarily of red blood cells, platelets, and fibrin gel.

[0048] Indeed, as schematically illustrated in Figure 4, the presence of the raised perforated bumps 9 in the non-woven fabric 7 allows for a thicker structure than the same non-perforated non-woven fabric, composed of hills and valleys in which aggregates can lodge without blocking the entire filtration surface of the non-woven fabric.

[0049] Advantageously, the embossed perforated non-woven layer is arranged in the filtration unit upstream of the leukoreduction medium to retain aggregates of blood or blood component before leukoreduction.

[0050] More specifically, several layers of embossed perforated non-woven fabric, for example two or three layers, are arranged upstream of the leukoreduction medium.

[0051] More specifically, the layer(s) of embossed perforated non-woven fabric are arranged in the most upstream part of the porous element of the filtration unit.

[0052] The embossed perforated nonwoven fabric is asymmetrical. In the filtration unit, the layer of embossed perforated nonwoven fabric is arranged with the 9 bumps facing upstream or downstream of the filtration unit. If the filtration unit has several layers of embossed perforated nonwoven fabric, the layers of embossed perforated nonwoven fabric are arranged with the 9 bumps facing in the same direction or in opposite directions.

[0053] When the 9 bumps are directed downstream, the flow of blood or blood component into the filtration unit is facilitated while preventing backflow.

[0054] According to one implementation, the thickness of the embossed perforated non-woven layer is between 400 and 1,500 µm, measured using a micrometer with a pressure of 10 kPa (ISO 9073-2:1995 standard). A thickness in the range of 500 to 1,300 µm is advantageous for achieving sufficient thickness to trap aggregates.

[0055] The embossed perforated non-woven fabric has a surface mass ranging from 40 to 90 g / m². 2 , in particular within the range of 50 to 80 g / m² 2 .

[0056] Below 50 g / m² 2 It appears that the leukoreduction rate deteriorates considerably due to the insufficient fiber density. Above 90 g / m³ 2 The fiber density is too high and the risk of blockage increases.

[0057] The air permeability of the embossed perforated non-woven layer is in the range of 800 to 3,000 L / m². 2 / s.

[0058] Air permeability is determined according to standard NF EN ISO 9237 on a sample of at least 100 cm³ 2 using an air permeabilimeter such as the TextTest FX 3300 with an air pressure set at 196 Pa (EDANA 140.1 standard).

[0059] An air permeability greater than 3,000 L / m 2A lower filtration rate (L / s) results in a shorter filtration time, since the blood potentially has more room to circulate, but carries a risk of an increased number of residual leukocytes. Below 800 L / m³ 2 / s, the filtration time increases as does the risk of blockage.

[0060] An air permeability of the embossed perforated non-woven layer within the range of 1,300 to 2,500 L / m 2 / s is a good compromise between filtration time, occurrence of blockages and leukoreduction rate.

[0061] The air permeability of the non-woven layer depends on several parameters including the air permeability of the base non-perforated non-woven, the dimensions of the perforations and the number of perforations in the non-woven.

[0062] In the case of a spun-bonded nonwoven, the average fiber diameter is in the range of 5 pm to 30 pm, particularly from 8 pm to 20 pm.

[0063] The dimensions of the 9 bumps and perforations are determined by optical measurement and porometry.

[0064] The bumps 9 extend from the surface of the non-woven fabric over a height between 200 pm and 1,500 pm, particularly between 400 pm and 700 pm.

[0065] According to one embodiment, the 9 bosses have a distal opening, substantially cylindrical in shape, with a diameter between 100 µm and 800 µm, particularly between 100 µm and 500 µm. The proximal opening of the 9 bosses is substantially cylindrical in shape, with a diameter between 1000 µm and 3000 µm, particularly between 1500 µm and 2500 µm.

[0066] Specifically, embossed perforated non-woven fabric has a perforation rate ranging from 5 to 20 perforations per cm 2 .

[0067] In addition to the embossed perforated non-woven layer(s), the porous element of the filtration unit comprises a leukoreduction medium 8 by adsorption and / or filtration of leukocytes. This leukoreduction medium 8 comprises in in particular one or more layers 11 of a non-woven material of meltblown fibers.

[0068] For example, the fibers of the leukoreduction medium 8 are chosen from polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate fibers and their copolymers.

[0069] Each layer 11 of the leukoreduction medium has a lower air permeability than the embossed perforated non-woven 7, so as to create a decreasing air permeability gradient from upstream to downstream.

[0070] In order to retain leukocytes as effectively as possible, each layer 11 of the leukoreduction medium 8 has a permeability within the range of 90 to 500 L / m 2 / s.

[0071] The surface mass of each layer 11 of the leukoreduction medium 8 is within the range of 20 to 80 g / m² 2 , in particular the range from 30 to 60 g / m 2 for a thickness between 100 and 400 µm.

[0072] A method for manufacturing a layer of embossed perforated nonwoven for the filtration of blood or a blood component with a filtration unit as described above includes embossing and piercing a layer of nonwoven between two rollers, at least one of which is provided with a plurality of needles, so as to perforate the nonwoven by creating bumps 9 around the perforations which are raised relative to the surface of the nonwoven.

[0073] To facilitate and reinforce the creation of the nine perforated embossing holes on the non-woven fabric, one of the rollers contains a plurality of needles, and the other roller contains cavities whose geometry is adapted to the interlocking of said needles during embossing. Furthermore, it is beneficial for at least one of the rollers to be heated.

[0074] The layer of embossed perforated non-woven fabric thus obtained by this manufacturing process is used to remove aggregates from blood or a blood component intended to be filtered.

[0075] In particular, this layer of embossed perforated non-woven fabric is assembled with a leukoreducing medium to form a porous element, said element porous material then being placed in an outer casing of a filtration unit.

[0076] A manufacturing process for a filtration unit 1 according to the first aspect thus comprises: - the formation of a layer of perforated non-woven fabric in relief by embossing and piercing a layer of non-woven fabric between two rollers, at least one of which is provided with a plurality of needles, so as to perforate the non-woven fabric by creating bumps 9 around the perforations 10 which are raised relative to the surface of the non-woven fabric; - the assembly of said layer of embossed perforated non-woven fabric with a leukoreduction medium so as to form a porous element, and - the arrangement of said porous element in an outer casing of a filtration unit.

[0077] The invention also relates to a method for leukoreducing blood or a blood component comprising passing said blood or blood component through a filtration unit as described above.

[0078] The leukoreduction process is an extracorporeal procedure, performed outside the human body, once the blood or blood component has been extracted and isolated from the donor. Specifically, the blood or blood component to be leukocyte-treated is contained in a bag.

[0079] According to another aspect and in relation to figure 5, the invention further relates to a bag system 12 for the leukoreduction of a fluid such as blood or a blood component, comprising a filtrate collection bag 13, said bag 13 being connected, via a tube 14 and at the level of an inlet port, to an outlet port of a filtration unit 1 according to the first aspect of the invention.

[0080] The system 12 further includes means for connecting to a bag (not shown) containing the fluid to be filtered, which are connected, via a tube 15, to an inlet port of the filtration unit. The connection means are, for example, a perforator 16.

[0081] Alternatively, a bag (not shown) intended to contain the fluid to be filtered is pre-connected to the filtration unit 1 via tubing 15.

[0082] Thus, the fluid, once collected and transferred into a bag, can be introduced into the bag system 12 to be filtered using the filtration unit, the filtrate then being collected in the filtrate collection bag 13.

[0083] A drip chamber 17 is connected to the system on the tubing 15 linking the filtration unit 1 and the means of connection to a bag containing the fluid to be filtered.

[0084] A bypass tube 18 is connected on one side to the tube 14 linking the filtration unit 1 and the filtrate collection bag 13, and on the other side to the tube 15 linking the filtration unit and the means of connection to a bag containing the fluid to be filtered, upstream of the drip chamber 17, if applicable.

[0085] This bypass tube 18 is used to expel air from the filtrate collection bag 13 and to purge the filtration unit 1.

[0086] Other well-known pocket systems, such as those described in document EP 1 336 417, can be used in the context of the invention.

[0087] Examples

[0088] Example 1: Characterization of embossed perforated nonwovens

[0089] A spun-linked nonwoven fabric was produced

[0090] The physical characteristics of a spunbond (SB) type nonwoven and a meltblown (MB) type nonwoven before and after perforation are shown below:

[0091] [Table 1]

[0092] The raised perforations were characterized using a liquid extrusion porometer from the company PMI.

[0093] The analytical results are as follows:

[0094] [Table 2]

[0095] Figure 6 represents the pore size distribution of the SB nonwoven before perforation and Figure 7, the pore size distribution of the SB11 nonwoven.

[0096] Figure 8 represents the optical characterization of SB11. According to this optical characterization, the height of a bump 9 is approximately 575 pm, the diameter of the distal perforation opening is approximately 375 pm and the diameter of the proximal perforation opening is approximately 2200 pm.

[0097] Example 2: Filtration of a red blood cell concentrate stored for 7 days at room temperature

[0098] A first series of tests was carried out to test the performance of a filtration unit according to the invention comprising one or two layers of embossed perforated non-woven material.

[0099] The blood component to be leukocyte-treated is a red blood cell concentrate obtained by gentle centrifugation (2000 g) of a whole blood sample (450–480 ml) supplemented with an anticoagulant (CRD). To promote aggregate formation, the red blood cell concentrate is stored without the addition of any other solution for 7 days at 4°C before filtration. Filtration is performed at room temperature, with the red blood cell concentrate at approximately 12–15°C.

[0100] Reference filtration unit 1

[0101] A filtration unit was created comprising, within a rigid housing, a porous element made up of layers stacked one on top of the other, from upstream to downstream: - a carded web consolidated by air penetration comprising a mixture of PET and Co-PET fibers having a permeability between 4000 and 5000 L / m 2 / s, a surface mass between 50 and 70 g / m² 2, and an average pore size of approximately 100 pm; - two layers of melt-blown polypropylene non-woven fabric with a thickness of approximately 285 µm and an air permeability of approximately 800 L / m 2 / s, as pre-filter layers; - sixteen layers of melt-blown polypropylene non-woven fabric, each having a surface mass of approximately 40 g / m² 2 and an air permeability of approximately 110 l / m 2 / s, as a leukoreduction medium.

[0102] Filtration Unit 1

[0103] In the filtration unit, the carded web of the reference filtration unit was replaced by a layer of embossed perforated non-woven SB11, with the 9 bumps directed downstream of the filtration unit.

[0104] Filtration Unit 2

[0105] In filtration unit 2, the carded web of the reference filtration unit was replaced by two layers of perforated non-woven SB11, stacked one on top of the other, with the bumps 9 directed downstream of the filtration unit.

[0106] Filtration Unit 3

[0107] In filtration unit 3, the carded web of the reference filtration unit was replaced by two layers of SB11 perforated non-woven fabric with the 9 bumps directed upstream of the filtration unit.

[0108] Filtration Unit 4

[0109] In filtration unit 4, the carded mat of the reference filtration unit was replaced by a layer of perforated non-woven SB7. The bumps 9 are directed downstream of the filtration unit.

[0110] Filtration Unit 5

[0111] In filtration unit 5, the carded web of the reference filtration unit was replaced by two layers of meltblown fiber type non-woven MB7, with the bumps 9 directed downstream of the filtration unit.

[0112] Filtration Unit 6

[0113] In filtration unit 6, the carded veil of the reference filtration unit was replaced by a layer of MB11 non-woven fabric with the 9 bumps directed downstream.

[0114] Filtration Unit 7

[0115] In filtration unit 7, the carded web of the reference filtration unit was replaced by two layers of perforated non-woven MB11 stacked one on top of the other, with the bumps 9 directed downstream of the filtration unit.

[0116] The leukoreduction results are shown in Table 3.

[0117] [Table 3]

[0118] It is noted that the filtration times of filtration units 5 to 7, which include layers of perforated melt-blown nonwoven fabric, are longer than those of other filtration units, which include layers of perforated spun-bond nonwoven fabric. Therefore, it is advantageous to use a layer of perforated spun-bond nonwoven fabric to retain aggregates.

[0119] Example 3: Filtration of a red blood cell concentrate not depleted in leukocytes and platelets

[0120] Another series of tests was carried out to test the performance of a closed-system filtration unit according to the invention comprising one or two layers of embossed perforated non-woven fabric.

[0121] The blood component to be leukocyte-treated is a red blood cell concentrate not depleted in leukocytes and platelets, obtained by hard centrifugation of a whole blood sample (450-480 ml) supplemented with an anticoagulant (CRD) and stored at 4°C for 3 days. The red blood cell concentrate is separated from the plasma, and the red blood cell concentrate / leukocyte-platelet layer mixture is filtered at room temperature.

[0122] Reference filtration unit 2

[0123] A filtration unit was created comprising, within a flexible casing, a porous element made up of layers stacked one on top of the other, from upstream to downstream: - two layers of spun-bonded polyester non-woven fabric with a thickness of approximately 330 µm, and an air permeability greater than 800 L / m 2 / s. - 26 layers of meltblown polypropylene fiber nonwoven fabric forming a decreasing air permeability gradient from approximately 400 to approximately 70 L / m 2 / s - a layer of spunbond woven nonwoven fabric having a thickness of approximately 330 µm and an air permeability greater than 800 L / m 2 / s.

[0124] Filtration Unit 8

[0125] In filtration unit 8, the first two layers of spun bonded nonwoven from reference filtration unit 2 were replaced by two SB11 layers with the bumps 9 directed downstream of the filtration unit.

[0126] The leukoreduction results are shown in Table 4.

[0127] [Table 4]

[0128] Example 4: Filtration of a red blood cell concentrate at room temperature

[0129] In this assay, the blood component to be leukocyte-treated is a red blood cell concentrate obtained by gentle centrifugation (2600 g) of a whole blood sample (450–480 ml) supplemented with an anticoagulant (CRD). The red blood cell concentrate is separated from the platelet-rich plasma, mixed with a SAGM-type additive solution, and filtered at room temperature. Filtration is performed within 8 hours of blood collection using filtration unit 8.

[0130] The leukoreduction results are shown in Table 5.

[0131] [Table 5]

Claims

DEMANDS 1 Filtration unit (1) intended to allow the leukoreduction of blood or a blood component, comprising an outer casing (2) provided with at least one inlet orifice (3) and at least one outlet orifice (4), the casing containing a porous element interposed between said orifices, said porous element comprising at least one leukoreduction medium (8) by adsorption and / or filtration of leukocytes, characterized in that said porous element further comprises at least one layer of non-woven fabric (7) provided with a plurality of bumps (9), each of said bumps being traversed vertically by a perforation (10), so as to form a layer of perforated non-woven fabric in relief. 2 Filtration unit according to claim 1, characterized in that the bumps (9) are frustoconical in shape. 3 Filtration unit according to any one of claims 1 or 2, characterized in that the bumps (9) form on the non-woven fabric a distinct and repeated pattern. 4 Filtration unit according to any one of claims 1 to 3, characterized in that the layer of embossed perforated non-woven material is arranged upstream of the leukoreduction medium (8). 5 Filtration unit according to any one of claims 1 to 4, characterized in that the embossed perforated non-woven has a thickness in the range of 500 to 1300 pm.

6. Filtration unit according to any one of claims 1 to 5, characterized in that the embossed perforated non-woven fabric has a surface mass in the range of 40 to 90 g / m² 2 .

7. Filtration unit according to any one of claims 1 to 6, characterized in that the embossed perforated nonwoven fabric has an air permeability in the range of 800 to 3,000 L / m². 2 / s. 8 Filtration unit according to any one of claims 1 to 7, characterized in that the bumps (9) extend from the surface of the non-woven fabric over a height of between 200 prn and 1,500 pm.

9. Filtration unit according to any one of claims 1 to 8, characterized in that the embossed perforated nonwoven fabric comprises a perforation rate in the range of 5 to 20 perforations per cm² 2 . 10 Filtration unit according to any one of claims 1 to 9, characterized in that the embossed perforated nonwoven is a spun bonded nonwoven. 11 Filtration unit according to any one of claims 1 to 10, characterized in that the leukoreduction medium (8) comprises one or more layers (11) of a meltblown nonwoven fiber material.

12. Filtration unit according to any one of claims 1 to 11, characterized in that the leukoreduction medium (8) comprises one or more layers (11) of a non-woven material, each layer (11) of the leukoreduction medium having a permeability in the range of 90 to 500 L / m³ 2 / s. 13 Filtration unit according to any one of claims 1 to 12, characterized in the leukoreduction medium (8) comprises one or more layers (11) of a non-woven material, each layer (11) of the leukoreduction medium having an air permeability lower than that of the embossed perforated non-woven layer.

14. Method for manufacturing a filtration unit (1) according to any one of claims 1 to 13, characterized in that it comprises: - the formation of a layer of perforated non-woven fabric in relief by embossing and piercing a layer of non-woven fabric between two rollers, at least one of which is provided with a plurality of needles, so as to perforate the non-woven fabric by creating bumps (9) around the perforations (10) which are raised relative to the surface of the non-woven fabric; - the assembly of said layer of embossed perforated non-woven fabric with a leukoreduction medium so as to form a porous element, and - the arrangement of said porous element in an outer casing of a filtration unit. 15 Manufacturing method according to claim 14, characterized in that one of the rollers comprises a plurality of needles and the other roller comprises cavities whose geometry is adapted to the fitting of the needles during embossing. 16 Extracorporeal method for leukoreducing blood or a blood component comprising passing said blood or said blood component contained in a bag through a filtration unit (1) according to any one of claims 1 to 13. 17 Bag system (12) for leukoreduction of blood or a blood component, characterized in that it comprises a bag (13) for collecting the filtrate, said bag (13) being connected, via a tube (14) and at the level of an inlet port, to an outlet port of a filtration unit (1) according to any one of claims 1 to 13.