DE102013012678A1 - FLAT FILTER MEDIA FOR THE DISTRIBUTION OF PLASMA OR SERUM OF FULL BLOOD - Google Patents

Abstract

Use of flat filter media for whole blood filtration, wherein the blood plasma / serum is separated from the blood cells. The filtration processes can achieve cell-free or virtually cell-free plasma without the occurrence of hemolysis while maintaining the concentration of diagnostic plasma analytes.

Description

FIELD OF THE INVENTION

The present invention relates to the use of flat filter media for separating blood plasma or blood serum from whole blood.

BACKGROUND OF THE INVENTION

Various types of blood and plasma / serum separation and treatment processes are known in the medical technology and state of the art. The most common way to separate blood cells from the liquid part of the blood is centrifugation.

In transfusion medicine, filters are used to remove leukocytes from transfusion blood and to remove blood clots and particles. In addition, arterial filters are used during operations, for example, to remove blood clots, particles and gas bubbles. Plasmapheresis filters are used to purify plasma of patients poisoned by bacteria, viruses or other components that are life threatening and to replace them with artificial blood plasma or plasma from donors.

In addition, micro-systems for whole-blood analysis are known which are based either on "test strips" or on a laboratory-on-a-chip technology. When these systems are used, only a few microliters of blood are needed for blood or serum analysis. With these devices, the separation of plasma / serum from whole blood is usually achieved by liquid mechanical effects, such as the wetting behavior of different surfaces or the use of microchannels. Although this method is very attractive in terms of rapidly obtaining blood analysis results, results from these analyzes are limited to a few test-specific components. These applications are inadequate to replace plasma / serum-based blood analysis with the existing sophisticated systems in laboratories and hospitals, which involve the analysis of a variety of blood components and which are capable of obtaining a holistic picture of the patient's health status. In addition, the task of separating blood cells from the liquid part of the blood is not satisfactorily resolved even for microsystems.

The "test strip" based separation of blood cells is highly dependent on the lateral separation efficiency of the separation media and preferably allows for qualitative blood analysis. Often, chemical agents are applied to the "test strip" which, depending on the presence and / or concentration of a blood component, results in a color reaction.

In many countries, it is obligatory to draw sufficient blood from the patient to be able to store the resulting plasma / serum sample for some time to check the analysis result some time later with a so-called reset sample. Until now, the task of obtaining sufficient cell-free plasma / serum can only be solved by centrifugation.

The centrifugation methods typically used to separate blood plasma / serum from whole blood are not only cumbersome in requiring a high degree of manual and mechanical handling, but they are also time consuming, which is particularly detrimental in emergency medicine.

Blood plasma / blood serum analyzers, which have a large capacity for plasma / serum samples, can not run at full capacity if preceded by a centrifugation process that works in batches and is a "bottleneck" in blood sampling. This bottleneck problem could possibly be overcome with a filtration process instead of a centrifugation process for plasma / serum recovery. Such a system would allow flexible analysis of samples: Urgent samples from emergency patients could be processed at a higher priority without having to interrupt an ongoing centrifugation process or wait for the end of the centrifugation process.

It is another advantage of a simple filtration process for whole blood separation that whole blood separation in plasma / serum and blood cells can be performed directly after collection of the blood sample. This is particularly advantageous for the quality of the subsequent blood analysis, because the stability of the red blood cells decreases with increasing sample storage time. This may affect the plasma / serum composition if the plasma / serum separation is not performed immediately after the blood sampling, but with some time delay. This aspect becomes important in rural Areas or developing countries where no plasma / serum separation centrifuge is available and where the blood sample needs to be transported for a prolonged period and / or a longer distance, sometimes even in a hot and / or humid environment.

Therefore, plasma / serum separation methods have been developed as an alternative measure to obtain blood plasma / serum from whole blood. However, these prior art plasma / serum separation methods are problematic in terms of, for example, blood cell concentration, plasma / serum yield, molecular adsorption capacity, extent of hemolysis, and leakage of blood cells (erythrocytes, platelets, and leukocytes). Hemolysis is one of the major problems because red blood cells, when they burst, alter the concentration of some plasma / serum analytes needed for further testing and, in some cases, analysis using optical measurement techniques due to the red color of the released one Hemoglobin impossible. In addition, the leakage of red blood cells is problematic because the cells or even other particles can destroy the blood plasma / blood serum analyzers because the sensitive capillaries and leads can become clogged. Only (essentially) cell- and hemolysis-free plasma / serum can be used for reliable blood analysis.

• US 5,674,394 offenbart eine geringvolumige wegwerfbare Filtrationstechnologie, um Blutplasma von Vollblut abzutrennen.
• US 5,919,356 bezieht sich auf eine Flüssigkeitsentnahmevorrichtung.
• US 2003/0206828 beschreibt eine Vollblutentnahmevorrichtung.
• US 5906742 A richtet sich auf Mikrofiltrationsmembranen, die eine hohe Porendichte und eine gemischte isotrope und anisotrope Struktur besitzen.
• WO 2012/143864 A1 betrifft ein Verfahren und Vorrichtung zur Bestimmung von Analyten in Vollblut.
• WO 93/19831 betrifft eine Blutfiltrationsvorrichtung und entsprechende Verfahren.
• US 5,186,843 betrifft Blutabtrennungsmedien und Verfahren zur Trennung von Plasma von Vollblut.
• US 20040222168 A1 beschreibt eine Vorrichtung zur Abtrennung und Ablassen von Plasma.

This is also the case with the use of "test strips" for qualitative blood analysis: Since color reactions are often used to indicate the presence and / or concentration of a blood component, no blood cells and no hemolysis must change the color of the plasma / serum and therefore the plasma / serum must be (essentially) free of cell and hemolysis.

• US 5,674,394 discloses a low volume disposable filtration technology to separate blood plasma from whole blood.
• US 5,919,356 refers to a fluid sampling device.
• US 2003/0206828 describes a whole blood collection device.
• US 5906742 A is aimed at microfiltration membranes that have a high pore density and a mixed isotropic and anisotropic structure.
• WO 2012/143864 A1 relates to a method and apparatus for the determination of analytes in whole blood.
• WO 93/19831 relates to a blood filtration device and related methods.
• US 5,186,843 relates to blood separation media and methods for separating plasma from whole blood.
• US 20040222168 A1 describes a device for separating and discharging plasma.

There remains a need for filter media for separating blood plasma / serum from whole blood which permit effective separation of blood plasma / serum from whole blood and which are suitable for use in a rapid, safe and robust manner to produce an appropriate amount of cell-free To obtain plasma / serum without causing hemolysis. With this type of separation process, deterioration of blood quality after patient blood collection or poor analysis results due to a delay in a centrifugation process or transportation can be avoided because blood cell separation can be performed immediately without centrifuge in an emergency or at the site of collection the blood test.

An option for a system for separating blood plasma / serum from blood cells without using a centrifuge is separation with a flat filter medium. However, such a separation process faces several challenges. Flat-panel media have limited capacity to contain and retain blood cells within or on the surface of the filter.

Typically, flat filter media are used in filtration of low particulate liquids rather than whole blood, which consists of approximately 40-50% cells. In particular, small pores within these filters tend to clog quickly due to the formation of a filter cake on the raw side, resulting in a high pressure drop across the filter. The pressure loss would then require an increase in pressure to continue the filtration process, but high pressure would cause bursting of blood cells and subsequent onset of hemolysis in the filtrate. In contrast, if the pores of a flat filter are too large, the clogging of the filter can be reduced, but instead some of the blood cells can pass through the filter into the filtrate. Furthermore, the amount of blood volume for a flat filter medium is usually highly dependent on the filter surface area, and therefore its capacity.

It is therefore an object of the present invention to provide the use of a whole blood filter medium and a method for separating whole blood blood plasma / serum advantageous over the prior art, especially with regard to the problems of hemolysis and leakage of blood cells (erythrocytes, platelets and leukocytes).

It is another object of the invention to provide the use of a whole blood filter medium and a method of separating blood plasma / serum from whole blood, wherein the separation from a sufficiently large amount of cell-free blood plasma / serum with none or substantially none Hemolysis is possible.

It is yet a further object of the invention to provide the use of a whole blood filter medium and a method for separating blood plasma / serum from a whole blood sample, wherein the separation of blood plasma / serum preferably in a manual or in a simple automatic manner without the Use of centrifuging agents is possible.

It is a further object of the present invention to provide for the use of a whole blood filter medium and a method for separating blood plasma / serum from whole blood, wherein the separation is less time consuming than the separation by conventional methods such. B. centrifugation methods.

It should be noted in this connection that there is usually no need for the blood cells to be recovered so that the method would require the step of isolating the red blood cells from the filter.

It is another object of the present invention to provide a blood filter medium, particularly a whole blood filter medium, and a method for separating blood plasma / serum from whole blood of a whole blood sample in an emergency. Ideally, cell separation may already take place at the site of the blood collection. Subsequently, the resulting plasma / serum sample can be immediately treated and delivered directly to a blood plasma / serum analyzer or a laboratory on-chip blood analysis product. The term emergency not only includes patient diagnosis in the event of an accident, but also blood treatment processes as provided by medical offices or patient controls during operations in hospitals. In this context, it is also an object to overcome the bottleneck problem of centrifugation and / or to avoid a falsification of the blood analysis by too long a treatment or too long transport of the non-separated whole blood sample.

It is a further object of the present invention to provide a whole blood filter medium and a method for separating blood plasma / serum from whole blood which reduce the risk of leakage of red blood cells into the filtrate.

It is another object of the present invention to provide a whole blood filter medium and a method of separating blood plasma from whole blood resulting in a cell-free or substantially cell-free plasma / serum filtrate, wherein the relative amounts of the molecular components to be analyzed in the filtration remain essentially unchanged. Ideally, the method comprises a filter medium that is inert and hemocompatible, does not release extractables or particles, and does not result in the adsorption of certain blood plasma / blood serum components on its solid surface nor in cross-reaction of certain blood plasma / blood serum components with its solid surface.

It is a further object of the present invention to provide a whole blood filter medium which can be used to separate blood plasma / serum from a whole blood sample, wherein the whole blood filter medium does not cause blood cell rupture, for example due to frictional forces or other mechanical stresses. caused.

It is another object of the present invention to provide a whole blood filter medium which can be used to separate blood plasma / serum from a whole blood sample without clogging the filter medium.

SUMMARY OF THE INVENTION

• a. Mikroglasfasern behandelt mit einem Binder;
• b. Mikroglasfasern behandelt mit einer Laminierung; oder
• c. Kombinationen davon.

In one aspect, the present invention relates to the use of a flat filter medium for separating blood plasma or blood serum from whole blood, the flat filter medium comprising a first material comprising:

• a. Microglass fibers treated with a binder;
• b. Microglass fibers treated with a lamination; or
• c. Combinations of it.

• i. Bereitstellen eines Flachfiltermediums umfassend Mikroglasfasern, behandelt mit einem Binder und einer Laminierung;
• ii. optionale Positionierung des Flachfiltermediums zwischen Blenden an der Rohseite und/oder der Reinseite;
• iii. optionales Bereitstellen eines Netzes an der Reinseite des Flachfiltermediums;
• iv. Auftragen von Vollblut auf die Rohseite des Flachfiltermediums;
• v. optionales Anwenden von Über- oder Unterdruck, vorzugsweise bis zu 0,8 bar und noch bevorzugter bis zu 0,4 bar; und
• vi. Aufsammeln des Plasma- oder Serumfiltrats von der Reinseite.

In yet another aspect, the present invention is directed to a method of separating plasma or serum from whole blood comprising the steps of:

• i. Providing a flat filter medium comprising microfiber fibers treated with a binder and a lamination;
• ii. optional positioning of the flat filter medium between apertures on the raw side and / or the clean side;
• iii. optionally providing a network on the clean side of the flat filter medium;
• iv. Application of whole blood to the raw side of the flat filter medium;
• v. optionally applying positive or negative pressure, preferably up to 0.8 bar and more preferably up to 0.4 bar; and
• vi. Collect the plasma or serum filtrate from the clean side.

• i. Das Bereitstellen eines Flachfiltermediums umfassend Mikroglasfasern mit einem Binder;
• ii. Das Auftragen von Vollblut auf das Flachfiltermedium;
• iii. Warten, bis Plasma oder Serum getrennt werden und lateral transportiert werden innerhalb des Flachfiltermediums (ohne Druck aufzulegen) in Richtung eines chemischen Agens, mit welchem ein oder mehrere bestimmte Blutkomponenten reagieren.

In yet another aspect, the present invention is directed to a method of separating plasma or serum from whole blood comprising the steps of:

• i. Providing a flat filter medium comprising micro glass fibers with a binder;
• ii. The application of whole blood to the flat filter medium;
• iii. Wait until plasma or serum is separated and transported laterally within the flat filter media (without applying pressure) towards a chemical agent with which one or more specific blood components react.

• i. Bereitstellen eines Flachfiltermediums umfassend Mikroglasfasern mit einem Binder;
• ii. Auftragen von Vollblut auf das Flachfiltermedium;
• iii. Warten, bis Plasma oder Serum getrennt wird und lateral transportiert wird innerhalb des Flachfiltermediums (ohne Druck aufzulegen);
• iv. Abschneiden des Filtermediums an der Grenze zwischen der Filterfläche gefüllt mit roten Blutkörperchen und der Filterfläche gefüllt mit flüssigem Plasma/Serum;
• v. Auspressen des getrennten Plasmas/Serums, um ein flüssiges Filtrat zu erlangen; und
• vi. Sammeln des Plasma- oder Serumfiltrats.

In yet another aspect, the present invention is directed to a method of separating plasma or serum from whole blood comprising the steps of:

• i. Providing a flat filter medium comprising micro glass fibers with a binder;
• ii. Applying whole blood to the flat filter medium;
• iii. Wait until the plasma or serum is separated and transported laterally within the flat filter medium (without applying pressure);
• iv. Cutting the filter medium at the boundary between the filter surface filled with red blood cells and the filter surface filled with liquid plasma / serum;
• v. Squeezing the separated plasma / serum to obtain a liquid filtrate; and
• vi. Collect the plasma or serum filtrate.

DESCRIPTION OF THE INVENTION

As used herein, the term "whole blood" refers to blood composed of blood plasma, which is typically unclimbed, and cellular components. The plasma represents about 50% to about 60% of the volume, and the cellular components, i. H. Erythrocytes (red blood cells or RBCs), leucocytes (white blood cells or WBCs) and platelets (platelets) represent about 40% to about 50% of the volume. As used herein, the term "whole blood" may refer to whole blood from an animal, but preferably to the whole blood of a human subject.

Erythrocytes, which contribute about 90 to about 99% of the total of all blood cells, are in the shape of biconcave discs and have a diameter of about 7 μm with a thickness of about 2 μm in an undeformed state. During maturation in the bone marrow, the erythrocytes lose their nucleus. They include the plasma membrane protein Spectrin and other proteins to provide flexibility to change shape if necessary. Their unique and flexible shape allows them to pass through very narrow capillaries and provides a maximum surface area to exchange oxygen and carbon dioxide. This flexibility makes it particularly difficult to separate the red blood cells from a whole blood sample by filtration because they can elongate and reduce their diameter to about 1.5 μm. Normal whole blood has approximately 4.5 to 5.5 million erythrocytes per microliter. The lifespan of erythrocytes is about 120 days in a circulating bloodstream. A core component of erythrocytes is hemoglobin, which binds oxygen for transport to the tissues, then releases oxygen and binds carbon dioxide to transport it as a waste product to the lungs. Hemoglobin is responsible for the red color of the erythrocytes and therefore for the blood as a whole. Erythrocytes are the major factor contributing to blood viscosity.

Leukocytes make up less than about 1% of the total number of blood cells and can be differentiated into different white blood cell groups (lymphocytes, granulocytes and monocytes). You can leave capillaries by diapedesis. In addition, they can move through tissue spaces through amyboid movements and positive chemotaxis. They have a diameter of about 6 to about 20 microns. Leukocytes participate in the body defense mechanisms, for example against bacterial or viral attacks.

Platelets are the smallest blood cells with a length of about 2 to 4 μm and a thickness of about 0.9 to about 1.3 μm. They are membrane-bound cell fragments that contain enzymes or other substances that are important for blood clotting. In particular, they form a temporary platelet plug that helps to occlude cracks in blood vessels.

The terms "blood plasma" or "plasma" refer to the liquid portion of the blood and lymphatic fluid that constitutes about half the blood volume (eg, about 50 to about 60% by volume). Plasma is free of cells and, unlike serum, it has not clotted. Therefore it contains all coagulation factors, especially fibrinogen. It is a clear yellow liquid, comprising about 90 to about 95% by volume of water.

The term "blood serum" or "serum" refers to the clear fluid that separates from the blood when it can clot completely, and therefore it is blood plasma from which, in particular, fibrinogen has been removed by coagulation. Like plasma, serum has a pale yellow color.

Molecular plasma / serum components can be classified into various groups including electrolytes, lipid metabolizers, markers such as for infections or tumors, enzymes, substrates, proteins, and even pharmaceuticals and vitamins.

As used herein, the term "cell-free" describes a plasma / serum sample having no or substantially no cells (erythrocytes, leukocytes, platelets) in a volume prepared, for example, by a centrifuge. A substantially cell-free or cell-free sample is needed for subsequent plasma / serum analysis to prevent blocking of the analysis system and to prevent color distortions in "test strips".

For the plasma analysis performed on the plasma obtained by the filtration or the squeezing out of liquid from the filter medium, the following analytes can be selected which include the relevant molecular groups. The reference concentration ranges of these selected heparinized blood analytes depend on the instrumentation used. The following exemplary reference concentration ranges of these selected analytes are obtained by the "Dimension" analyzer from Siemens. Plasma components: Reference concentration ranges of analytes for heparin-stabilized whole blood and the selected meter electrolytes potassium 3.5-5.1 mmol / l sodium 136-145 mmol / l calcium 2.12-2.52 mmol / l magnesium 0.74-0.99 mmol / l chloride 98-107 mmol / l phosphate 0.80-1.60 mmol / l lipids triglycerides 75-175 mg / dl cholesterol 110-200 mg / dl HDL cholesterol 35-60 mg / dl LDL Cholesterol <150 mg / dl markers of infection CRP 0-5.00 mg / l enzymes AST / GOT 0-35 unit / l lipase 114-286 unit / l substrates albumin 3.4-5.0 g / dl bilirubin 0-1.0 mg / dl glucose 74-106 mg / dl creatinine 0.60-1.30 mg / dl proteins IgG 6.81-16.48 g / l ferritin 3.0-244 ng / l hormones TSH basal 0.36-16.00 mUnit / l

The "Dimension" analyzer from Siemens can be used not only for the analysis of blood plasma, but also for the analysis of blood serum.

As used herein, the term "ensuring permeability", e.g. "To blood plasma or serum" or "to whole blood" preferably, that none of the above-mentioned plasma or serum components to be analyzed are completely retained in the separation. Preferably, the concentrations of the blood components to be analyzed are not significantly changed compared to the whole blood sample before separation. More preferably, the concentrations of the plasma or serum components to be analyzed are changed by not more than 50%, preferably not more than 35%, more preferably not more than about 10%, most preferably not more than about 8%.

As used herein, the term "hemolysis" refers to the bursting of erythrocytes, for example, by chemical, thermal or mechanical influences that cause the release of the hemoglobin and other internal components into the surrounding fluid. Hemolysis can be visually detected by the appearance of pink to red staining in plasma / serum. Hemolysis is a common feature observed in serum and plasma samples and may affect the laboratory test parameters for blood analysis. Hemolysis can occur for two reasons. In vivo hemolysis can be caused by pathological conditions such. Autoimmune hemolytic anemia or a transfusion reaction. In vitro hemolysis may be due to improper collection of samples, improper sample processing or improper sample transport. In particular, hemolysis can be caused by a high pressure drop and a high shear or strain rate, which can occur, for example, during filtration processes when the sample passes through a porous filter medium. Other important factors for hemolysis include bacterial contamination, pressure, temperature, osmotic environment, pH, contact with surfaces, frictional forces, age of the blood and storage time of the undivided whole blood sample.

The extent of hemolysis can be visually detected in comparison to a plasma reference solution having a certain concentration of hemoglobin (Hb, HGB). Blood plasma samples that are the same color as a reference solution that does not contain hemoglobin do not show any hemolysis. Blood plasma samples that are the same or less red than a solution containing approximately 50 mg / dL hemoglobin have essentially no hemolysis. In this regard, "substantially no hemolysis" means that the blood plasma samples have such a degree of hemolysis that is still sufficient to assure that the samples can be analyzed with satisfactory results, for example, the Siemens "Dimension" plasma analyzer , Blood plasma samples that are equal to or less red than a solution containing approximately 100 mg / dL hemoglobin have a moderate degree of hemolysis. Blood plasma samples of one color that match a solution with a hemoglobin content greater than 100 mg / dl have a high degree of hemolysis.

Any medium or material that does not interact with whole blood is generally described as "hemocompatible." In particular, no interaction means that the medium or material does not cause blood clotting, for example by interaction with the blood clotting system or the platelets. Accordingly, a hemocompatible material has no thrombotic effect. It is preferred that the bulk filter media of the present invention be hemocompatible. In addition, it is preferable that the filter media does not modify any of the blood component concentrations by adsorption or reaction, and that the contact with the whole blood does not cause hemolysis.

• (a) gemäß ihrer Molekülstruktur können diagnostische Marker zur Gruppe gehören umfassend atomische Ionen, Lipide, Lipoproteine, Steroide, Zucker, Nukleinsäuren, Proteine, Peptide, Aminosäuren, Alkohole und Porphyrine;
• (b) gemäß ihrer Funktion können diagnostische Marker zu der Gruppe gehören, umfassend Elektrolyte, Enzyme, Substrate, Antikörper, Hormone, Toxine, Neurotransmitter, Medikamente, Metabolite, Lipidmetabolite, Transportproteine, Vitamine, oder
• (c) gemäß ihrem Molekulargewicht; diagnostische Marker können zu der Gruppe gehören umfassend niedermolekulare Analyten eines Molekülgewichts von 10 bis 2000 Da, oder hochmolekulare Moleküle, welche Proteine und Proteinkomplexe mit einem Molekulargewicht größer als 2000 Da umfassen; oder
• (d) gemäß ihrer Anwendung in der Detektion einer speziellen Krankheit; diagnostische Marker können zu der Gruppe gehören umfassend Krebsmarker, Herzmarker, Autoimmunmarker, metabolische Marker.

The term "diagnostic markers" as used herein refers to a molecular parameter wherein its presence in whole blood, or preferably in blood plasma or serum, or a dilution thereof, can be measured. A diagnostic marker may also preferably be quantified, and it reflects the seriousness or presence of a physiological condition or other condition. A diagnostic marker may further indicate even a risk or the progression of a disease, or the sensitivity of the disease to a given treatment. Diagnostic markers can be categorized into different groups, for example

• (a) according to their molecular structure, diagnostic markers may belong to the group comprising atomic ions, lipids, lipoproteins, steroids, sugars, nucleic acids, proteins, peptides, amino acids, alcohols and porphyrins;
• (b) according to their function, diagnostic markers may belong to the group comprising electrolytes, enzymes, substrates, antibodies, hormones, toxins, neurotransmitters, drugs, metabolites, lipid metabolites, transport proteins, vitamins, or
• (c) according to their molecular weight; diagnostic markers may belong to the group comprising low molecular weight analytes of molecular weight from 10 to 2000 Da, or high molecular weight molecules comprising proteins and protein complexes having a molecular weight greater than 2000 Da; or
• (d) according to its application in the detection of a particular disease; Diagnostic markers may belong to the group comprising cancer markers, cardiac markers, autoimmune markers, metabolic markers.

Examples of diagnostic markers include the potassium cation, sodium cation, calcium cation, magnesium cation, chloride, phosphate, triglyceride, cholesterol, high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol, C-reactive protein (CRP ), Aspartate transaminase / glutamate oxaloacetate transaminase (AST / GOT), lipase, albumin, bilirubin, glucose, creatinine, IgG, ferritin, TSH, insulin, rheumatoid factors, prostate specific antigen (PSA), S100B, cytochrome C, Creatine kinase or troponin.

The term "mesh", as used herein, refers to a solid medium, preferably a filter medium, which is preferably flat and preferably made of polymer or metal fibers which are geometrically combined, for example, as a square mesh, inverted smooth woven mesh, plain plain Tissue fabric or weave fabric in twill weave by textile weaving technologies. Preferably, the mesh does not contribute to the separation of plasma from whole blood, and preferably has a stabilizing effect, and thereby counteracts the deformation of the flat filter to avoid tearing of the filter. Preferably, the mesh provides a mesh size between 50 μm and 1000 μm, preferably between 150 μm and 400 μm, and even more preferably between 200 and 350 μm. Preferably, the mesh is made of hydrophobic fibers or fibers coated with a hydrophobic layer.

The term "capillary effects" refers to the flow of fluid in tight spaces without the assistance of an external force such as gravity or pressure. They are based on intermolecular forces between the liquid and solid surrounding surfaces, the combination of surface tension and adhesive forces between the liquid and surrounding material causing the liquid to move.

As used herein, the "raw side" or "upstream" side of a filter is the side or surface through which the liquid enters the filter media. It is considered as the entry side or surface. The "clean side" or "downstream" side of a filter is the side or surface through which the fluid exits the filter media. It is considered as the exit side or surface.

The term "flat filter" as used herein refers to filters wherein the filter media are relatively "flat" and therefore preferably have a thickness of less than 5 mm, more preferably less than 2 mm, and even more preferably less than 1 mm. A flat filter may comprise one or more layers of filter media.

The term "aperture" refers to a thin plate with at least one hole, preferably in the middle of the plate. Preferably, the plate is impermeable to whole blood or any blood components. Therefore, the aperture per se does not constitute a filter medium. In this context, the term "multi-aperture" refers to apertures with more than one hole.

The term "lateral filtration" refers to a so-called "wicking" separation method wherein a certain volume of blood is applied to the surface of a filter medium and then the blood cells from the whole blood from the plasma or serum through different transport mechanisms and / or different transport rates at the same Side or in the depth of the filter medium. For example, lateral filtration is often used in blood test strips where a drop of blood is applied to a loading zone and the plasma or serum is then passed through the strip into a loading zone Detection zone is transported, in which certain analytes of the plasma or serum can undergo a chemical reaction with a detection agent. The resulting signal can be measured as qualitative or quantitative signals, for example in a colorimetric or fluorescence assay.

The term "basis weight" as used herein refers to the density of a flat filter media as a measure of the mass of the filter media per unit of filter media area. The unit of basis weight is g / m ² . Basis weight is also known as paper density.

The term "MFP" refers to the mean pore size, which is the pore diameter at a pressure loss at which the flow through a wetted medium is 50% of the flow through the dry medium.

mit der Grenzflächenspannung γ zwischen der benetzenden Flüssigkeit und umfließender Gasphase und dem Kontaktwinkel ϑ zwischen der benetzenden Flüssigkeit und der festen Oberfläche. Die größte zu entleerende Pore (bei dem niedrigsten Druck, bei welchem ein Fluss wahrgenommen wird) definiert den sogenannten Bubble Point. Nachdem alle Poren entleert wurden (bis zum höchsten erreichbaren Druck) während eines Benetzungslaufs, wird ein zweiter Trockenlauf mit derselben Probe durchgeführt. Als Resultat werden vollständige Datensätze, umfassend den Volumenfluss (für den Nass- und Trockenlauf) im Vergleich zu der auferlegten Druckdifferenz, erhalten. Aus diesen Datensatzpunkten, wird der Punkt, bei dem der Fluss durch ein benetztes Medium 50% des Flusses durch das Trockenmedium ist, bestimmt als die mittlere Flussporengröße.To determine the average pore size experimentally, the capillary flow pore method is used. This method uses the simple principle of gas pressure to force a wetting liquid out of through pores in a sample. Through pores are simply those that connect one side of the sample to the other. The pressure at which voids pore is inversely proportional to the pore size, larger pores require less pressure than smaller pores. The resulting volumetric gas flow through deflated pores is also measured. The corresponding pore size d opened and traversed by the gas at a given differential pressure Δp is calculated using the Washburn equation:

with the interfacial tension γ between the wetting liquid and the surrounding gas phase and the contact angle θ between the wetting liquid and the solid surface. The largest pore to be evacuated (at the lowest pressure at which a flow is sensed) defines the so-called bubble point. After all pores have been emptied (to the highest pressure achievable) during a wetting run, a second dry run is performed on the same sample. As a result, complete data sets including the volume flow (for the wet and dry run) compared to the imposed pressure difference are obtained. From these data points, the point at which the flow through a wetted medium is 50% of the flow through the dry medium is determined to be the mean pore size.

According to the "Filtration and Separation Dictionary" (Steve Tarleton and Richard Wakeman), a binder is "an organic or inorganic solid or liquid that is used to help fuse / flock fibers or particles connect, like those of a filter medium. For example, resins are used to effect resin bonding, where the mesh is dipped or sprayed in resin, and subsequently dried and / or applied to make the final product. "

According to the "Filtration and Separation Dictionary" (Steve Tarleton and Richard Wakeman), laminated media "fixes together two or more layers of media."

• a. Mikroglasfasern behandelt mit einem Binder;
• b. Mikroglasfasern behandelt mit einer Laminierung; oder
• c. Kombinationen davon.

In a first embodiment, a flat filter medium is used to separate blood plasma or blood serum from whole blood, the flat filter medium comprising a first material comprising:

• a. Microglass fibers treated with a binder;
• b. Microglass fibers treated with a lamination; or
• c. Combinations of it.

In another embodiment, the flat filter medium comprises a mixture of glass fibers treated with a binder and / or a lamination. In another preferred embodiment, the glass fibers comprise microfiber fibers.

In another preferred embodiment, the binder is selected from the group consisting of epoxy, latex acrylic or acrylic resins, or combinations thereof.

In another preferred embodiment, the binder is hydrophilic for lateral filtration, and is preferably epoxy or latex acrylic. In another embodiment, the lamination preferably leads to a hydrophobic surface for the separation of blood plasma from the raw side of the flat filter medium to the clean side.

In yet another preferred embodiment, the glass fibers are selected from borosilicate fibers or soda lime glass, and are preferably borosilicate fibers.

In another embodiment, the flat filter medium has a thickness between about 0.2 mm and about 1 mm, preferably between about 0.3 mm and about 0.8 mm, and even more preferably between about 0.4 mm and about 0.6 mm ,

In yet another embodiment, the flat filter medium has an average pore size between about 2 μm and about 8 μm, preferably between about 2 μm and about 5.5 μm, even more preferably between about 2 μm and about 4 μm, and most preferably between about 2.5 μm and about 3 μm.

In a particularly preferred embodiment, the flat filter medium comprises borosilicate fibers having a lamination to provide a hydrophobic surface, the binder is an acrylic resin, and the flat filter medium has a thickness between about 0.4 mm and about 0.6 mm, an average pore size between about 2 , 5 μm and about 3 μm, and a basis weight of between about 72 g / m ² and about 85 g / m ² .

In another preferred embodiment, the flat filter comprises a network downstream. Preferably, the mesh is a polymeric woven mesh. A mesh having a hydrophobic surface with a pore size which ensures permeability to whole blood, blood plasma or serum is preferred. Even more preferably, the mesh has a mesh size of between about 250 μm and about 350 μm.

In a preferred embodiment, the netting is a woven network of polyester fibers having a mesh of between about 250 μm and about 300 μm and an open area of 44%, having a mesh of about 23 / cm, a wire diameter of about 145 μm, a weight of about 110 g / ^m2 and a thickness of about 255 microns, the mesh being coated with a hydrophobic coating.

In another preferred embodiment, the net is a woven uncoated net of hydrophobic fibers.

In another embodiment, a second material is arranged on the inflow side of the flat filter medium, preferably a hydrophobic fiber filter medium. The hydrophobic fiber filter medium may be selected from the group consisting of polyester, polypropylene, polyethylene terephthalate, or a combination thereof. The hydrophobic fiber filter medium may be a nonwoven material, preferably a meltblown nonwoven material.

In another embodiment, the hydrophobic fiber filter medium comprises one or more layers of polypropylene fibers.

In yet another preferred embodiment, the flat filter medium is positioned between apertures or multihole apertures.

These panels are made of a material that is not permeable to blood, plasma or serum.

In one embodiment, the panels are made of a polymeric material, preferably a hydrophobic material, for example polypropylene.

In another embodiment, the plates are made of a flat material having a thickness between about 0.3 mm and about 3 mm.

In yet another embodiment, the apertures show a central hole with a circular cross-section which confers blood, plasma or serum through this hole.

In yet another preferred embodiment, the orifices exhibit a number of annular holes with material fillets between which the blood, plasma or serum is provided through these holes.

In yet another preferred embodiment, the diaphragms show some holes of different geometries which are combined in a diaphragm which confers the blood, plasma or serum through these holes.

In yet another preferred embodiment, different apertures are combined with different hole shapes within a filter. Preferably, the aperture is positioned with the central hole downstream of the flat filter medium, and the aperture with annular holes is positioned upstream of the flat filter medium.

In one embodiment, the flat filter medium is used for filtration from the raw side to the clean side.

In another embodiment, the flat filter medium is used for lateral filtration.

In another embodiment, the whole blood is diluted with isotonic sodium chloride solution. Preferably, the whole blood sample is diluted with isotonic sodium chloride solution in a ratio of about 0.5: 1 to about 1: 5, preferably in a ratio of about 1: 1 to about 1: 4.

In a preferred embodiment, the whole blood of the sample is stabilized by an anti-coagulation agent selected from the group consisting of EDTA, citrate, heparin, and combinations thereof.

In another preferred embodiment, the whole blood of the sample is pretreated with a cell agglomeration agent, such as lectin.

• i. Bereitstellen eines Flachfiltermediums, umfassend Mikroglasfasern mit einem Binder und einer Laminierung;
• ii. optionale Positionierung des Flachfiltermediums zwischen Blenden an der Rohseite und/oder der Reinseite;
• iii. Bereitstellen eines Netzes an der Reinseite des Flachfiltermediums;
• iv. Auftragen von Vollblut auf der Rohseite des Flachfilters;
• v. optionales Anbringen eines Über- oder Unterdrucks, vorzugsweise bis zu 0,8 bar und noch bevorzugter bis zu 0,4 bar; und
• vi. Sammeln von Plasma oder Serumfiltrat von der Reinseite.

In another embodiment, the separation of plasma or serum from whole blood comprises the steps of:

• i. Providing a flat filter medium comprising micro glass fibers with a binder and a lamination;
• ii. optional positioning of the flat filter medium between apertures on the raw side and / or the clean side;
• iii. Providing a network on the clean side of the flat filter medium;
• iv. Application of whole blood on the raw side of the flat filter;
• v. optionally applying an overpressure or underpressure, preferably up to 0.8 bar and more preferably up to 0.4 bar; and
• vi. Collect plasma or serum filtrate from the clean side.

The pressure in step iv. Overpressure can be applied to the raw side or negative pressure attached to the clean side. In one embodiment, the positive or negative pressure is induced with a syringe. Preferably, the pressure is less than 0.8 bar, preferably less than 0.4 bar, and even more preferably less than 0.3 bar.

• i. Bereitstellen eines Flachfiltermediums umfassend Mikroglasfasern mit einem Binder;
• ii. Auftragen von Vollblut auf das Flachfiltermedium;
• iii. Warten, bis Plasma oder Serum getrennt und lateral transportiert wird innerhalb des Flachfiltermediums (ohne Druck aufzulegen) in Richtung eines chemischen Agens, mit welchem ein oder mehrere bestimmte Blutkomponenten reagieren.

In yet another aspect, the present invention is directed to a method of separating plasma or serum from whole blood comprising the steps of:

• i. Providing a flat filter medium comprising micro glass fibers with a binder;
• ii. Applying whole blood to the flat filter medium;
• iii. Wait until plasma or serum is transported separately and laterally within the flat filter media (without applying pressure) towards a chemical agent with which one or more specific blood components will react.

• i. Bereitstellen eines Flachfiltermediums umfassend Mikroglasfasern mit einem Binder;
• ii. Auftragen von Vollblut auf das Flachfiltermedium;
• iii. Warten, bis Plasma oder Serum getrennt und lateral transportiert wird innerhalb des Flachfiltermediums (ohne Druck aufzuerlegen);
• iv. Abschneiden des Filtermediums an der Grenze zwischen der Filterfläche gefüllt mit roten Blutkörperchen und der Filterfläche gefüllt mit flüssigem Plasma/Serum;
• v. Auspressen des getrennten Plasmas/Serums, um ein flüssiges Filtrat zu erlangen; und
• vi. Sammeln des Plasma- oder Serumfiltrats.

in einer anderen Ausführungsform enthalten die Flachfiltermedien keine Zellulosefasern.In yet another aspect, the present invention is directed to a method of separating plasma or serum from whole blood comprising the steps of:

• i. Providing a flat filter medium comprising micro glass fibers with a binder;
• ii. Applying whole blood to the flat filter medium;
• iii. Wait until plasma or serum is transported separately and laterally within the flat filter media (without imposing pressure);
• iv. Cutting the filter medium at the boundary between the filter surface filled with red blood cells and the filter surface filled with liquid plasma / serum;
• v. Squeezing the separated plasma / serum to obtain a liquid filtrate; and
• vi. Collect the plasma or serum filtrate.

in another embodiment, the flat filter media does not contain cellulosic fibers.

Example 1 Drop test

Each filter medium reacts differently when in direct contact with a drop of liquid or blood. As a result, in a first test, a drop of blood was applied to the flat filter media. The test was carried out with both sides of the filter, the raw side and the clean side. The observations from a drop test allow a first assessment of the filter material, for example, in terms of hydrophobicity, hydrophilic capillary effects or immediate on-contact hemolysis.

Glass fiber media without binder, Ahlstrom Grade III and 151, were wetted with one drop of whole blood. It was immediately observed that the surrounding ring within the filter media was red rather than yellow-orange, indicating immediate hemolysis.

Binder, LyPore XL Grade 9102-F, and Grade 9104-D glass filter media were wetted with one drop of whole blood after delamination of the coarse pre-filter. Droplets on the treated glass fiber filter medium were rapidly absorbed to form a red spot of blood cells and a yellow-colored hemolysis-free plasma ring around the red dot.

Ahlstrom grade MFPS0201 glass fiber media with binder and lamination shows a hydrophobic behavior: the contact angle between the whole blood drop and the filter medium in air is greater than 90 ° and the droplet remains on the surface without being absorbed.

Example 2 Filtration Using Glass Microfibers with Binder

The separation efficiency of flat filter media has usually been studied in at least two experiments. For flat filter media that were asymmetric, d. H. where the two surface sides of the medium were different, each side was the raw side. Between 0.5 and 1 ml of whole blood was applied to the filter medium in each filtration experiment. If necessary, pressure was applied using a syringe to transport the fluid through the filter medium. The discoloration of the filter media on the clean side and the obtained filtrate droplets on the clean side were analyzed to assess the separation efficiency.

In all experiments, a woven network of polyester fibers called Hyphobe 285/44 from Saatitech, which has a hydrophobically coated 285 μm mesh surface, was placed as a mesh downstream of the flat filter media as a stabilizing net.

The flat filter media were used as a round flat filter in small housings. Typically, a polypropylene housing with a filter diameter of about 27.7 mm and a filter area of about 5.81 cm ^{2 was} used. Downstream of the filter medium, the housing was open to observe the filtration result.

In one experiment, the filter medium was MFPS0201 from Ahlstrom. In addition, MFPS0301 was used as a filter medium.

The results of the filtration experiments with different filter material are summarized in Table 1. Table 1 Flat filter medium comment MFPS0301 (finely structured side of the filter medium downstream) After application of low pressure, formation of small, clear, yellow-orange droplets on the clean side of the filter MFPS0201 (finely structured side of the filter medium downstream) First droplets were yellow and clear at the clean side of the filter; only after application of higher pressure; first plasma droplets appear at 0.3 bar or even at lower pressure and a maximum pressure of 0.8 bar could be applied.

Example 3 Use of glass fiber with binder in lateral whole blood filtration

The drop test was performed using Lypore XL 9102F. The filter medium was an asymmetric filter material that could be delaminated into a first layer and a second layer. The drop test was carried out with both layers. The drop test showed that lateral filtration, i. H. the formation of a yellow ring around the area of the blood drop application, using only one of the layers, the other layer did not separate plasma from blood cells and no yellow plasma surface was obtained around the area of whole blood application.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 5674394 [0011]
• US 5919356 [0011]
• US 2003/0206828 [0011]
• US 5906742 A [0011]
• WO 2012/143864 A1 [0011]
• WO 93/19831 [0011]
• US 5186843 [0011]
• US 20040222168 A1 [0011]

Claims (20)

Use of a flat filter medium for separating blood plasma or blood serum from whole blood, the flat filter medium comprising a first material comprising: a. Microglass fibers treated with a binder; b. Microglass fibers treated with a laminate; or c. Combinations of it. Use of the flat filter medium according to claim 1, wherein the binder is selected from the group consisting of epoxy, latex acrylic or acrylic resin, or combinations thereof. Use of the flat filter medium according to one of claims 1 or 2, wherein the micro glass fibers comprise borosilicate fibers, alkali-free borosilicate fibers, quartz fibers or combinations thereof. Use of the flat filter medium according to any one of claims 1 to 3, wherein the first material has a thickness between about 0.2 mm and about 1 mm, preferably between about 0.3 mm and about 0.8 mm, and even more preferably between about 0 , 4 mm and about 0.6 mm. Use of the flat filter medium according to any one of claims 1 to 4, wherein the first material of the flat filter medium has an average pore size between about 2 μm and about 8 μm, preferably between about 2 μm and about 5.5 μm, even more preferably between about 2 μm and about 4 μm, and most preferably between about 2.5 μm and about 3 μm. Use of the flat filter medium according to any one of claims 1 to 5, wherein the basis weight of the first material of the flat filter medium is between about 70 g / m ² and about 100 g / m ² , and preferably between about 72 g / m ² and about 85 g / m ² is. Use of the flat filter medium of any one of claims 1 to 6, wherein the first material is borosilicate fibers, the binder is an acrylic resin, and the flat filter has a thickness between about 0.4 mm and about 0.6 mm, a mean pore size between about 2, 5 microns and about 3 microns and a basis weight between about 72 g / m ² and about 85 g / m ² . Use of the flat filter medium according to any one of claims 1 to 7, wherein the flat filter medium further comprises a mesh disposed downstream of the first material. Use of the flat-filtering medium according to claim 8, wherein the net is a hydrophobic net, and preferably a polymeric woven net having a hydrophobic surface. Use of the flat filter medium according to one of claims 1 to 9, further comprising a second material disposed upstream of the first material, and wherein the second material is preferably a hydrophobic material. Use of the flat filter medium of claim 10, wherein the hydrophobic material comprises one or more layers of polypropylene nonwoven web. Use of the flat filter medium according to any one of claims 1 to 11, wherein the flat filter medium is free from cellulose fibers. Use of flat filter medium according to one of claims 1 to 12, wherein the flat filter medium is positioned between apertures or multi-hole apertures. Use of flat filter medium according to one of claims 1 to 13, wherein the plasma or serum is separated from the whole blood from the raw side of the medium towards the clean side of the medium. Use of flat filter medium according to any one of claims 1 to 14, wherein the separation of plasma or serum from whole blood is a lateral separation. Use of flat filter medium of claims 1 to 15, wherein the whole blood is pretreated with a) isotonic sodium chloride solution, preferably with a 0.9% sodium chloride solution (w: v) in a ratio of 0.5: 1 to 1: 5, preferably in a ratio of 1: 1 to 1: 4; b) an anti-coagulation agent selected from the group consisting of EDTA, citrate, heparin, and combinations thereof; or c) a cell agglomeration agent, preferably lectin. A method of separating plasma or serum from whole blood comprising the steps of: i. Providing a flat filter medium comprising micro glass fibers treated with a binder or a laminate; ii. optional positioning of the flat filter medium between apertures on the raw side and / or the clean side; iii. optionally providing a network on the clean side of the flat filter medium; iv. Application of whole blood to the raw side of the flat filter medium; v. optionally applying positive or negative pressure, preferably up to 0.8 bar and more preferably up to 0.4 bar; and vi. Collect plasma or serum filtrate from the clean side of the filter media. A method of separating plasma or serum from whole blood comprising the steps of: i. Providing a flat filter medium comprising microfiber fibers treated with a binder; ii. Applying whole blood into a first zone of the flat filter medium; iii. Lateral spreading of blood plasma or serum from a first zone to a second zone, the second zone extending at least partially beyond the first zone; iv. optional reaction of the blood plasma or serum analyte with a reagent located in the second zone. A method of separating plasma or serum from whole blood comprising the steps of: i. Providing a flat filter medium comprising microfiber fibers treated with a binder; ii. Applying whole blood into a first zone of the flat filter medium; iii. Lateral spreading of blood plasma or serum from a first zone to a second zone, the second zone extending at least partially beyond the first zone; iv. Collecting the plasma or serum from the second zone. The method of any of claims 16 to 18, wherein the whole blood is pretreated with: a) isotonic sodium chloride solution, preferably with a 0.9% sodium chloride solution (w: v), in a ratio of 0.5: 1 to 1: 5, preferably in a ratio of 1: 1 to 1: 4; b) an anti-coagulation agent selected from the group consisting of EDTA, citrate, heparin, and combinations thereof; or c) a cell agglomeration agent, preferably with lectin.