Filter paper for red blood cell collection

Abstract

The present invention provides filter paper for red blood cell collection, the filter paper being used for separating and collecting red blood cells from blood, said filter paper being characterized by comprising glass filter paper and a water-absorbing sheet, and the glass filter paper being overlapped on the water-absorbing sheet. Also provided is a method for analyzing the fatty acid composition in a red blood cell membrane using the aforementioned filter paper for red blood cell collection.

Description

Filter paper for collecting red blood cells

[0001] The present disclosure relates to filter paper for separating and collecting a red blood cell fraction from blood.

[0002] Fatty acids are essential for maintaining healthy living organisms, serving as an energy source, a component of cell membranes, and for promoting vitamin absorption. Essential fatty acids cannot be synthesized in the body and must be ingested through diet. While both ω-3 and ω-6 fatty acids are essential for the body, maintaining a healthy balance between ω-3 and ω-6 fatty acid intake is crucial. While ω-3-derived metabolites have been shown to exhibit anti-inflammatory properties, increased intake of ω-6 fatty acids has been shown to increase the production of arachidonic acid (20:4n-6), which in turn produces prothrombotic and pro-inflammatory n-6 metabolites (Stark et al., Nutr. Rev. 66:323-332 2008). Furthermore, an increased ratio of ω3 to ω6 fatty acids is thought to promote the onset of many diseases, including cardiovascular disease, osteoporosis, inflammation, and autoimmune diseases (Stark et al., Nutr. Rev. 66:323-332 2008.). Therefore, knowing the intake status of essential fatty acids, such as ω3 and ω6 fatty acids, through diet is beneficial for maintaining the health of the body.

[0003] In various tests to assess human health status, blood is often used as an important source of outcome data, excluding non-invasive measurements. Blood components (red blood cells, plasma or serum, white blood cells, and platelets) provide valuable information. For example, plasma or serum is used in blood biochemistry tests to assess liver function, kidney function, diabetic lipids, and electrolytes. However, in lipid research, such as ω-3 and ω-6 fatty acids, the serum or plasma fatty acid composition is easily affected by recent dietary intake, raising questions about the reliability and interpretation of data. For example, the International Society for the Study of Fatty Acids and Lipids (ISSFAL) stated in 2020 that "clinical trials examining the effects of fatty acids should consider the influence of fatty acid status (baseline, endpoint, and change from baseline to endpoint) on outcome variables" (Renate et al., Prostaglandins Leukot. Essent. Fatty Acids 157:102029 2020.). Traditionally, blood (plasma or serum) EPA and DHA concentrations have been measured as indicators of ω-3 fatty acid intake (Liu et al., Prostaglandins Leukot Essent Fatty Acids 91:251-260 2014). However, as mentioned above, commonly performed fatty acid analysis of blood (plasma) samples reflects dietary influences over the last few days, making it difficult to assess long-term (monthly) ω-3 fatty acid intake. On the other hand, the fatty acid composition of erythrocyte membranes reflects fatty acids ingested over the past 1-2 months and is therefore useful for determining long-term fatty acid intake (Harris and Thomas, Clin Biochem. 43:338-340 2010). Currently, data calculated from the Omega-3 index (the sum of EPA and DHA in blood) and erythrocyte membrane fatty acid composition are becoming mainstream eligibility criteria.

[0004] With the recent increase in health awareness, various health self-monitoring services are being offered. While there are currently services for analyzing fatty acids in blood (dried whole blood) samples (see, for example, Liu et al., Prostaglandins Leukot Essent Fatty Acids 91:251-260 2014), there are no services for analyzing fatty acids in red blood cell samples separated from plasma. One reason for this is the lack of a convenient method for preparing red blood cell samples. In clinical settings, fatty acid analysis is typically performed using (1) plasma and serum samples, (2) red blood cell membranes (layers) are not analyzed, and (3) whole blood DBS (Dry Blood Spot), which is prepared by dropping blood onto filter paper and drying it, is currently used for health self-monitoring.

[0005] In view of the above circumstances, one embodiment of the present disclosure aims to develop means and methods for easily measuring changes in fatty acid composition in a living body over a long-term diet (e.g., over 1 to 2 months), and aims to provide filter paper for easily separating red blood cells from plasma components and collecting red blood cells that can be easily subjected to fatty acid analysis.

[0006] The inventors discovered that when a glass filter paper made of glass fiber and an absorbent sheet were overlapped and blood was dropped onto the glass filter paper and allowed to stand, the plasma component of the blood was absorbed by the absorbent filter paper, while the red blood cells remained on the glass filter paper, and thus completed the present invention. The filter paper according to one embodiment of the present disclosure (hereinafter also referred to as "red blood cell collection filter paper"), which is made by overlapping a glass filter paper and an absorbent sheet, can be used to analyze the fatty acid composition of red blood cell membranes when dried, while the dried lower sheet containing plasma and serum dilutes the red blood cell portion. Therefore, by using this lower sheet, various markers can be detected with higher sensitivity than when using existing dried blood spots (DBS).

[0007] That is, the present disclosure can include the following (1) to (12). (1) A filter paper for collecting red blood cells, comprising a glass filter paper and a water-absorbent sheet, the glass filter paper being superimposed on the water-absorbent sheet. (2) The filter paper for collecting red blood cells according to (1) above, wherein the glass filter paper comprises one or more inorganic glasses selected from the group consisting of soda-lime glass, aluminosilicate glass, borosilicate glass, alkali-free glass, and quartz glass. (3) The filter paper for collecting red blood cells according to (1) or (2) above, wherein the glass filter paper comprises borosilicate glass. (4) The filter paper for collecting red blood cells according to any one of (1) to (3) above, wherein the content of inorganic glass relative to the total mass of the glass filter paper is 90 mass% or more. (5) The filter paper for collecting red blood cells according to any one of (1) to (4) above, wherein the glass filter paper has a retention particle size of 0.2 μm to 1.5 μm. (6) The filter paper for collecting red blood cells according to any one of (1) to (5) above, wherein the water-absorbent sheet contains a cellulose-based compound. (7) The filter paper for collecting red blood cells according to any one of (1) to (6) above, wherein the water-absorbent sheet contains one or more porous materials selected from the group consisting of activated carbon, zeolite, silica gel, activated alumina, clay minerals, aluminophosphates, silicoaluminophosphates, and styrene-divinylbenzene copolymers. (8) The filter paper for collecting red blood cells according to any one of (1) to (7) above, wherein an adhesive layer is included between the glass filter paper and the water-absorbent sheet. (9) The filter paper for collecting red blood cells according to any one of (1) to (8) above, wherein at least one of the glass filter paper and the water-absorbent sheet contains at least one of an antioxidant and a chelating agent. (10) A method for analyzing the fatty acid composition of red blood cell membranes, comprising dropping blood onto the glass filter paper of the red blood cell collection filter paper described in any one of (1) to (9) above, drying the filter paper, and then measuring the fatty acid composition contained in the glass filter paper. (11) A kit for testing the fatty acid composition of red blood cell membranes, comprising glass filter paper and a water-absorbent sheet. (12) A filter paper for collecting red blood cells, comprising a separation filter paper and a water-absorbent sheet, wherein the separation filter paper is overlaid on the water-absorbent sheet, and the separation filter paper has a retention particle size of 0.2 μm to 1.5 μm.

[0008] According to one embodiment of the present disclosure, it becomes possible to monitor changes in the fatty acid composition in a living body that are affected by diet over several months using a simple method.

[0009] Furthermore, by using the filter paper for collecting red blood cells according to one embodiment of the present disclosure, blood can be easily separated into plasma and red blood cells, and red blood cells can be easily collected by the patient themselves, eliminating the need for the complicated process typically performed at medical institutions.

[0010] Fig. 1 is a diagram showing a schematic structure of a filter paper for collecting red blood cells according to one embodiment of the present disclosure, and Fig. 2 is a diagram showing a schematic structure of a filter paper for collecting red blood cells according to another embodiment of the present disclosure.

[0011] Hereinafter, embodiments of the present invention will be described. Note that, unless otherwise specified, the term "the present embodiment" refers to all embodiments described in this specification.

[0012] DEFINITIONS When this specification is translated into English and includes the singular words "a," "an," and "the," this shall include the plural as well as the singular, unless the context clearly indicates otherwise.

[0013] In this specification, "comprise" is used in the sense of including "consist of." "Comprise" means that it may contain components other than those included, and "consist" means that it does not essentially contain components other than those included. "Consist only of" means that it does not contain components other than those included.

[0014] In this specification, the term "to" indicating a numerical range is used to mean that the numerical values ​​before and after it are included as the upper and lower limits. In this specification, in numerical ranges described in stages, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in this specification, the upper or lower limit value of a numerical range described in a numerical range may be replaced with a value shown in an example.

[0015] <First Red Blood Cell Collection Filter Paper> In one embodiment, the red blood cell collection filter paper (also referred to as "red blood cell collection filter paper of this embodiment") is a filter paper for separating and collecting red blood cells from blood, and is characterized in that it includes glass filter paper and a water-absorbent sheet, with the glass filter paper being overlaid on the water-absorbent sheet. The red blood cell collection filter paper of this embodiment may be used for humans, or may be used for non-human animals other than humans.

[0016] (Glass Filter Paper) In this embodiment, the "glass filter paper" may be any type of filter paper that contains so-called "glass" fibers.

[0017] The glass may be organic glass or inorganic glass, but is preferably inorganic glass from the viewpoint of blood separation ability. Examples of inorganic glass include soda-lime glass, aluminosilicate glass, borosilicate glass, alkali-free glass, and quartz glass. From the viewpoint of blood separation ability, the glass filter paper preferably contains borosilicate glass among the above. The glass filter paper may contain two or more types of inorganic glass. From the viewpoint of blood separation ability, the glass contained in the glass filter paper is preferably fibrous, but is not limited thereto.

[0018] From the viewpoint of blood separation performance, the glass content relative to the total mass of the glass filter paper is preferably 50% by mass or more, more preferably 75% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more. The upper limit of this content is not particularly limited, and may be 100% by mass.

[0019] To improve strength, the glass filter paper may contain organic molecules (organic binders) that function as a bonding agent. Furthermore, the glass filter paper may contain antioxidants or chelating agents (e.g., EDTA) to prevent oxidation of fatty acids, prevent blood coagulation, and stabilize blood. Antioxidants include, but are not limited to, dibutylhydroxytoluene (DHT), tert-butylhydroquinone (TBHQ), butylated hydroxyanisole (BHA), citric acid, vitamin C (ascorbic acid), vitamin E (tocopherol), and sugar alcohols such as trehalose, maltitol, and sorbitol. The above antioxidants may be impregnated into the glass filter paper.

[0020] Any glass filter paper can be used as long as its particle retention size is smaller than that of red blood cells and does not clog. Those skilled in the art can easily select glass filter paper with an appropriate particle retention size through preliminary experiments. For example, mouse red blood cells are approximately 4 μm to 5 μm in diameter, and human red blood cells are approximately 7 μm to 8 μm in diameter. Therefore, a glass filter paper with a retention particle size of 0.2 μm to 1.5 μm is preferred, a retention particle size of 0.3 μm to 1.2 μm is more preferred, and a retention particle size of 0.5 μm to 1.0 μm is even more preferred. In this specification, "retention particle size" refers to the particle size at which 90% or more of a seven-type powder dispersion is retained when naturally filtered through glass filter paper in accordance with JIS Z 8901 (2006).

[0021] The thickness of the glass filter paper is preferably changed depending on the amount of blood to be dropped, but is preferably 0.10 mm to 0.70 mm, more preferably 0.13 mm to 0.55 mm, and even more preferably 0.15 mm to 0.40 mm.

[0022] The glass filter paper to be used may be one produced by a conventionally known method or a commercially available one, for example, the GC series manufactured by ADVANTEC (Toyo Roshi Co., Ltd.).

[0023] (Water-Absorbent Sheet) The "water-absorbent sheet" in this embodiment may be made of any material as long as it is a sheet capable of absorbing liquid components such as blood plasma. The water-absorbent sheet may contain a water-absorbent material. Examples of water-absorbent materials include acrylic polymers such as partial sodium salts of acrylic acid polymers and crosslinked products thereof, partial sodium salts of acrylic acid graft polymers and crosslinked products thereof, starch-acrylic acid graft polymer salts and crosslinked products thereof, saponified vinyl acetate-acrylic acid ester copolymers and crosslinked products thereof, and 2-acrylamido-2-methylpropanesulfonic acid-acrylic acid copolymer salts and crosslinked products thereof; cellulose-based compounds such as sodium carboxymethylcellulose and ammonium carboxymethylcellulose; alkylene oxide polymers such as polyalkylene oxides and modified polyalkylene oxides; hydrolyzed starch-acrylonitrile graft polymers, hydrolyzed acrylonitrile copolymers or acrylamide copolymers or crosslinked products thereof, crosslinked products of cationic monomers, and crosslinked isobutylene-maleic acid copolymers. Among the above, cellulose-based compounds are preferred from the viewpoint of blood separation properties.

[0024] The content of the water-absorbent material relative to the total mass of the water-absorbent sheet is preferably 30% by mass to 90% by mass.

[0025] The water-absorbent sheet may contain a porous material, such as activated carbon, zeolite, silica gel, activated alumina, clay minerals, aluminophosphates, silicoaluminophosphates, and styrene-divinylbenzene copolymers. Among these, silica gel is preferred from the viewpoint of blood separation properties.

[0026] The content of the porous material in the total mass of the water-absorbent sheet is preferably 30% by mass to 90% by mass.

[0027] The absorbent sheet may contain an antioxidant or a chelating agent (such as EDTA) to prevent oxidation of fatty acids. The antioxidant is as described above. The absorbent sheet may be impregnated with the antioxidant.

[0028] The thickness of the water-absorbent sheet is preferably adjusted appropriately depending on the amount of blood to be dropped. When cellulose filter paper is used, the thickness is preferably 0.15 mm to 0.50 mm, more preferably 0.20 mm to 0.40 mm, and even more preferably 0.25 mm to 0.30 mm, from the viewpoint of blood separation performance.

[0029] In this embodiment, "overlapping" refers to a state in which the glass filter paper and the water-absorbent sheet are in direct or indirect contact and overlapped in a layered manner, as shown in Figure 1. The state in which the glass filter paper and the water-absorbent sheet are in indirect contact and overlapped in a layered manner means a state in which an adhesive layer formed by an adhesive or the like exists between the glass filter paper and the water-absorbent sheet.

[0030] The areas of the glass filter paper and the absorbent sheet may be approximately the same, but from the perspective of blood separation, it is preferable that the area of ​​the absorbent sheet be larger than that of the glass filter paper. The area of ​​the glass filter paper is not particularly limited, but is preferably, for example, approximately the same as the area of ​​a circle with a diameter of approximately 5 mm to 10 mm. The shape of the glass filter paper may be other than circular. By making the glass filter paper circular with a diameter of approximately 5 mm to 10 mm, blood separation can be further improved and manufacturing costs can be reduced. The area of ​​the absorbent sheet is not particularly limited as long as it is equal to or larger than the area of ​​the glass filter paper, and when multiple samples are collected simultaneously, any shape and area may be used as long as the glass filter papers can be stacked with a distance sufficient to prevent the blood samples from mixing.

[0031] <Adhesive Layer> In one embodiment, the red blood cell collecting filter paper may include an adhesive layer between the glass filter paper and the water-absorbent sheet, as shown in Figure 2. The adhesive layer may include an adhesive that does not affect the accuracy of the analysis of lipids in the red blood cell membrane, such as an epoxy-based adhesive, a urethane-based adhesive, an acrylic-based adhesive, or an emulsion-based adhesive. Among the above, acrylic adhesives are preferred because they allow the glass filter paper and the water-absorbent sheet to be easily separated during analysis of lipid components.

[0032] The adhesive layer can be formed by applying an adhesive to the surface of the absorbent sheet and drying it. Although the adhesive application method is not limited, it is preferable to apply the adhesive by a spray method from the viewpoint of migration of blood plasma and the like.

[0033] <Second Red Blood Cell Collection Filter Paper> In one embodiment, the red blood cell collection filter paper (also referred to as "red blood cell collection filter paper according to another embodiment") is a filter paper for separating and collecting red blood cells from blood, the filter paper comprising a separation filter paper and a water-absorbent sheet, the separation filter paper being overlaid on the water-absorbent sheet, and the separation filter paper having a retention particle size of 0.2 μm to 1.5 μm. The red blood cell collection filter paper according to another embodiment may be used for humans, or may be used for non-human animals other than humans.

[0034] (Separation Filter Paper) From the viewpoint of blood separation performance, the retention particle size of the separation filter paper is preferably 0.20 mm to 0.40 mm, and more preferably 0.25 mm to 0.30 mm.

[0035] The separation filter paper may contain particles or fibers, and the material is not limited as long as it can achieve the above-mentioned retention particle size, but glass is preferred. Glass has been described above, so a description thereof will be omitted here. Furthermore, the preferred glass content in the separation filter paper is the same as that of the glass filter paper in the first red blood cell collection filter paper, and therefore a description thereof will be omitted here. The separation filter paper may contain a binder, an antioxidant, and a chelating agent, as in the first red blood cell collection filter paper. The preferred thickness of the separation filter paper is the same as that of the glass filter paper in the first red blood cell collection filter paper, and therefore a description thereof will be omitted here. Hereinafter, the separation filter paper will also be referred to as glass filter paper, as in the first red blood cell collection filter paper.

[0036] (Water-absorbent sheet) The water-absorbent sheet that can be used is the same as that described in the first filter paper for capturing red blood cells, and therefore a description thereof will be omitted here.

[0037] (Adhesive Layer) In one embodiment, the red blood cell collecting filter paper may include an adhesive layer between the separation filter paper and the water-absorbent sheet. The adhesive layer may be the same as that described for the first red blood cell collecting filter paper, and a description thereof will be omitted here.

[0038] <Method for analyzing the fatty acid composition of red blood cell membrane> In one embodiment, the method for analyzing the fatty acid composition of red blood cell membrane comprises dropping blood onto a glass filter paper (the first or second red blood cell collection filter paper) comprising a glass filter paper and an absorbent sheet, with the glass filter paper and the absorbent sheet superimposed on each other (see Figure 1), drying the filter paper, and then measuring the fatty acid composition contained in the glass filter paper.

[0039] As mentioned above, the fatty acid composition of erythrocyte membrane reflects the fatty acids ingested in the past few months, and is therefore useful for understanding the long-term fatty acid intake status, whereas the fatty acid composition of whole blood including plasma reflects the influence of the diet of the past few days immediately before analysis.Therefore, the conventional simple method for analyzing the fatty acid composition of blood (whole blood including plasma) cannot eliminate the influence of the fatty acids contained in plasma, and it is difficult to examine the fatty acid composition ingested over a long period of time.In contrast to such conventional methods, the fatty acid analysis method of the present invention allows for the simple examination of the long-term fatty acid intake status by analyzing the fatty acid composition of erythrocyte membrane collected by the erythrocyte collection filter paper according to this embodiment.

[0040] The fatty acid composition of the erythrocytes collected on the glass filter paper can be easily analyzed by a standard method. For example, blood is dropped onto the erythrocyte collection filter paper according to the present embodiment, the filter paper is thoroughly dried, the dried glass filter paper is peeled off from the absorbent sheet, and the methylation treatment is performed, followed by gas chromatography analysis (for details, see Lepage et al., J. Lipid Res. 25:1391-1396 1984 and Masood et al., J. Lipid Res. 46:2299-2305 2005).

[0041] <Kit> In one embodiment, the kit is a kit for testing the fatty acid composition of red blood cell membranes (also referred to as "the kit according to this embodiment") that includes glass filter paper and a water-absorbent sheet. The kit according to this embodiment is a kit for testing the fatty acid composition of red blood cell membranes that includes glass filter paper and a water-absorbent sheet as essential components. For details about the glass filter paper and the water-absorbent sheet, see the description of the first or second red blood cell collection filter paper above.

[0042] The kit according to this embodiment is intended for a user to overlay glass filter paper on a water-absorbent sheet to create a filter paper for capturing red blood cells according to this embodiment, and then drip blood onto the glass filter paper, but the glass filter paper and water-absorbent sheet may be previously adhered with the above-mentioned adhesive, etc. In addition to the glass filter paper and water-absorbent sheet, the kit may also include tools for collecting blood (e.g., a puncture needle), disinfectant alcohol, absorbent cotton, adhesive bandages, adhesive, instructions for use (or information such as the URL of a website explaining how to use the kit), etc.

[0043] The present invention will be further explained below by showing examples, but these examples are merely illustrative of embodiments of the present invention and do not limit the scope of the present invention.

[0044] 1. Preparation of filter paper (special filter paper) for collecting red blood cells The glass filter paper used was a 0.19 mm thick filter paper (GC-50) manufactured by ADVANTEC (Toyo Roshi Co., Ltd.), and the water-absorbent sheet used was a 0.27 mm thick ion-exchange filter paper (Whatman SG81, SILICAGEL LOADED) manufactured by Whatman Co. The particle retention diameter of the glass filter paper was 0.5 μm.

[0045] The glass filter paper was cut into a circle with a diameter of 8 mm, and the ion-exchange filter paper was cut into a square with a size of 4 cm x 7.5 cm. The ion-exchange filter paper was sprayed with a spray (3M Spray Glue 55, 3M Company) to form an adhesive layer on the surface of the ion-exchange filter paper, and the glass filter paper and ion-exchange filter paper were then adhered together to prepare the red blood cell collection filter paper shown in Figure 2.

[0046] Then, as an antioxidant treatment, a butylhydroxytoluene (BHT) solution (5 mg / mL) and a mixed solution of EDTA and trehalose (5 mg / mL; EDTA, 50 mg / mL; trehalose) were dropped onto the glass filter paper, which was then dried and used in the following experiments.

[0047] 2. Analysis of Fatty Acid Composition of Erythrocyte Membranes 2-1. Example 1 Mice bred on a normal diet (MF) were fed a high-fat diet. Three days later, blood samples were collected. Whole blood samples were then centrifuged to obtain plasma and red blood cell layers. Blood samples from the same individual (whole blood) were also dropped onto a special filter paper (red blood cell collection filter paper according to the present embodiment, hereinafter the same) and, after drying, the glass filter paper (8 mm diameter) containing the dried red blood cells was removed. A 12 mm diameter circular punchout was used to obtain the absorbent sheet containing dried plasma, the ion-exchange filter paper. The glass filter paper and ion-exchange filter paper were subjected to methylation treatment and analyzed by gas chromatography (n = 4) (Lepage et al., J. Lipid Res. 25:1391-1396 1984 and Masood et al., J. Lipid Res. 46:2299-2305 2005). Similarly, whole blood, plasma, and red blood cell layers were methylated and analyzed by gas chromatography (n=4). As a control, blood samples from mice not switched to a high-fat diet (normal diet) were used (n=4). The measurement results are shown in Tables 1 and 2.

[0048]

[0049]

[0050] After three days of feeding a high-fat diet enriched with ω-6 fatty acids, plasma ω-6 fatty acids were elevated compared to those fed a normal diet (Table 1, boxed text; 44.4). In contrast, there was almost no increase in ω-6 fatty acids in the red blood cell layer, reflecting the fatty acid composition resulting from the intake of normal feed before feeding the high-fat diet (see Table 1, underlined numbers). Furthermore, in whole blood, the degree of increase in ω-6 fatty acids was buffered by the influence of fatty acids derived from red blood cells (Table 1). Meanwhile, the fatty acid composition and total ω-6 / ω-3 ratio of the dried plasma and dried red blood cells separated and obtained by the method of the present invention were confirmed to almost faithfully reproduce the fatty acid composition of the plasma and red blood cells obtained by centrifugation of whole blood (Table 2).

[0051] 2-2. Example 2 The diet of adult female mice bred and raised on a diet deficient in ω3 fatty acids (Def) was replaced with a normal diet (Adq), and after three days of raising, blood was collected and the fatty acid composition of whole blood, plasma, red blood cell layer, and dried plasma and dried red blood cells dropped onto special filter paper was measured in the same manner as in Example 1 (DA, n = 4). As a control, blood samples from mice raised on Def without changing the diet were used (DD, n = 4). The measurement results are shown in Tables 3 and 4.

[0052]

[0053]

[0054] When animals fed an ω-3 fatty acid-deficient diet were fed an ω-3 fatty acid-normal diet for three days, plasma ω-3 fatty acids increased (Table 3, boxed text; 3.2). Similar to the results of Example 1, this change was barely observed in the red blood cell layer, reflecting the fatty acid composition due to the ω-3 fatty acid-deficient diet (see Table 3, underlined numbers). In whole blood, the degree of increase in ω-3 fatty acids was buffered by the influence of fatty acids derived from red blood cells (Table 3). Meanwhile, the fatty acid composition and total ω6 / ω3 ratio of the dried plasma and dried red blood cells separated and obtained by the method of the present invention were confirmed to almost faithfully reproduce the fatty acid composition of the plasma and red blood cells obtained by centrifuging whole blood (Table 4).

[0055] From the above results, it became clear that the fatty acid composition of dried red blood cells dropped onto the red blood cell collection filter paper of this embodiment can be used to evaluate the fatty acid balance in a long-term diet in an extremely simple manner, without the need for procedures such as blood sampling and centrifugation at a medical institution.

[0056] According to the present invention, it is possible to easily examine the composition of fatty acids ingested over a long period of time in a diet. Therefore, the present invention is expected to be used in the fields of health management, health monitoring, medical care, etc.

Claims

1. A filter paper for collecting red blood cells, comprising a glass filter paper and a water-absorbent sheet, the glass filter paper being superimposed on the water-absorbent sheet.

2. The filter paper for collecting red blood cells according to claim 1, wherein the glass filter paper comprises one or more inorganic glasses selected from the group consisting of soda-lime glass, aluminosilicate glass, borosilicate glass, alkali-free glass, and quartz glass.

3. A filter paper for collecting red blood cells according to claim 1 or 2, wherein the glass filter paper comprises borosilicate glass.

4. A filter paper for collecting red blood cells according to any one of claims 1 to 3, wherein the content of inorganic glass relative to the total mass of the glass filter paper is 90 mass% or more.

5. A filter paper for collecting red blood cells according to any one of claims 1 to 4, wherein the particle size of the glass filter paper to be retained is 0.2 μm to 1.5 μm.

6. A filter paper for collecting red blood cells according to any one of claims 1 to 5, wherein the absorbent sheet contains a cellulose compound.

7. A filter paper for collecting red blood cells according to any one of claims 1 to 6, wherein the water-absorbent sheet comprises one or more porous materials selected from the group consisting of activated carbon, zeolite, silica gel, activated alumina, clay minerals, aluminophosphates, silicoaluminophosphates, and styrene-divinylbenzene copolymers.

8. A filter paper for collecting red blood cells according to any one of claims 1 to 7, which comprises an adhesive layer between the glass filter paper and the water-absorbent sheet.

9. A filter paper for collecting red blood cells according to any one of claims 1 to 8, wherein at least one of the glass filter paper and the water-absorbent sheet contains at least one of an antioxidant and a chelating agent.

10. A method for analyzing the fatty acid composition of red blood cell membranes, comprising dropping blood onto a glass filter paper of a red blood cell collection filter paper described in any one of claims 1 to 9, drying the filter paper, and then measuring the fatty acid composition contained in the glass filter paper.

11. Red blood cell membrane fatty acid composition test kit, including glass filter paper and absorbent sheet.

12. A filter paper for collecting red blood cells, comprising a separation filter paper and an absorbent sheet, the separation filter paper being superimposed on the absorbent sheet, and the particle size of the separation filter paper being 0.2 μm to 1.5 μm.

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