A backed nitrocellulose membrane and its preparation method and application

Abstract

The application provides a nitrocellulose membrane with backing, a preparation method and application thereof, and belongs to the technical field of high polymer materials. The preparation method of the nitrocellulose membrane with backing comprises the following steps: S10, dissolving nitrocellulose, a pore former and a hydrophilic polymer in DMF and / or DMA and performing filtering and degassing treatment to obtain a uniform and stable nitrocellulose casting solution; S20, performing film casting on a backing made of PVC to obtain a precursor film; S30, performing phase separation on the precursor film in a solution to obtain a semi-wet film; and S40, washing and drying the semi-wet film to obtain the nitrocellulose membrane with backing. The nitrocellulose membrane with backing has the characteristics of uniform and controllable pore size, good hydrophilicity, strong protein binding capacity and scalable production, and has a wide application prospect in the field of in-vitro diagnostic reagents.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a backed nitrocellulose membrane, its preparation method, and its application. Background Technology

[0002] Nitrocellulose membranes (NC membranes) are a type of functional membrane material primarily composed of nitrocellulose, a cellulose derivative. Due to the strong dipolarity of the nitrate groups on nitrocellulose, they exhibit strong non-specific adsorption of macromolecules such as proteins, enabling efficient immobilization of biomolecules. Therefore, NC membranes play a crucial role as solid-phase carriers in colloidal gold immunochromatographic assays. Furthermore, NC membranes can also be used in molecular biology and biochemistry fields such as cell culture, biosensors, molecular hybridization, and immunoblotting.

[0003] The preparation process of nitrocellulose membranes is mainly as follows: First, nitrocellulose particles are dissolved in an organic solvent, and a certain proportion of surfactant is added. The mixture is stirred to form a uniform casting solution. Then, the casting solution is passed through a roller to form a thin film that is spread flat on a planar carrier. The film is then dried and shaped using a specific process. Finally, it is harvested and slit to obtain the nitrocellulose membrane product. Patent CN114768545A discloses a nitrocellulose microporous membrane and its continuous preparation method. Using a simple conventional process, a protein adsorbent with good compatibility with nitrocellulose is added during the casting solution preparation process to prepare an NC membrane with excellent protein binding capacity. Patent CN114130373A discloses a nitrocellulose membrane and its preparation method. Using a simple conventional process, a hydrotalcite with a special layered structure is added during the casting solution preparation process to prepare an NC membrane with a multi-porous support layer structure. Patent CN113150334A discloses a nitrocellulose membrane preparation process. In this process, by improving the surfactant treatment process, the influence of bubbles and impurities on the NC membrane during production is reduced, thereby producing a higher quality NC membrane. As a key component of immunochromatography, the non-conductive chromatographic (NC) membrane serves as both the solid-phase support for the detection (T-line) and control (C-line) lines, and the region where antigens and antibodies react. Its quality directly impacts the performance of in vitro diagnostic reagents. Methods for assessing NC membrane quality include "water immersion performance" and "spotting tests," both of which are related to the membrane's pore size and hydrophilicity. Small-pore membranes have a large specific surface area, allowing for greater protein binding and slower chromatography speeds. This results in longer transit times for the gold-labeled complex through the T-line, leading to more complete reactions and higher sensitivity. However, small-pore membranes also result in slower plate running speeds, a higher chance of non-specific binding, and a greater likelihood of false positives. Therefore, NC membranes with appropriate pore sizes are required for the detection of different analytes.

[0004] Nitrocellulose membranes, a type of cellulose derivative, possess some hydrophilicity, but it is not ideal and needs to be improved through surfactant treatment during the preparation process. However, surfactants are small molecules and are lost during NC membrane storage, resulting in reduced and uneven hydrophilicity. Furthermore, surfactant solutions are prone to bubbling, which can accumulate on the NC membrane surface during continuous production, affecting membrane quality. Therefore, to obtain NC membranes with stable quality and controllable pore size, it is necessary to improve the NC membrane preparation process to achieve adjustment of pore size and hydrophilicity during preparation. Summary of the Invention

[0005] This invention is made to solve the above-mentioned problems, and its purpose is to provide a cellulose nitrate membrane with a backing, a method for preparing the membrane, and its application.

[0006] This invention provides a method for preparing a backed nitrocellulose membrane, characterized by the following steps: S10, dissolving nitrocellulose, a pore-forming agent, and a hydrophilic polymer in DMF and / or DMAC at a ratio of (10-50) wt%: (1-30) wt%: (1-15) wt%, and then filtering and degassing to obtain a homogeneous and stable nitrocellulose casting solution, wherein the pore-forming agent includes polyvinylpyrrolidone and / or polyethylene glycol, and the hydrophilic polymer includes sulfonated polyethersulfone, polyaniline, or polyacrylamide. Any one or more; S20, the nitrocellulose casting solution is coated onto a PVC backing with a thickness of 0.06 mm to 0.10 mm to form a precursor film; S30, the precursor film is separated into phases in a solution to obtain a semi-wet film; S40, the semi-wet film is washed and dried to obtain a backed nitrocellulose membrane, wherein the backed nitrocellulose membrane is a microporous membrane, the micropore size of the backed nitrocellulose membrane can be controlled by adjusting the amount of pore-forming agent, and the hydrophilic properties of the backed nitrocellulose membrane can be controlled by adjusting the amount of hydrophilic polymer.

[0007] The method for preparing a backed nitrocellulose membrane provided by the present invention may also have the following feature: in step S10, the degassing treatment is performed by letting the membrane stand for more than 4 hours to remove bubbles.

[0008] The method for preparing a backed nitrocellulose membrane provided by the present invention may also have the following feature: in step S20, the tool used for film forming is a scraper with a film thickness of 0.38 mm.

[0009] The method for preparing a backed nitrocellulose membrane provided by the present invention may also have the following feature: in step S30, the solution includes an aqueous solution of any one or more of DMF, DMAC, isopropanol or ethanol with a concentration not exceeding 25 wt%.

[0010] The method for preparing a backed nitrocellulose membrane provided by the present invention may also have the following feature: in step S40, the washing method is a water bath at 20°C to 50°C for at least 30 seconds.

[0011] The present invention also provides a backed nitrocellulose membrane, characterized in that it is prepared by any of the preceding methods for preparing a backed nitrocellulose membrane, wherein the backed nitrocellulose membrane comprises: a PVC backing with a thickness of 0.06 mm to 0.10 mm; and a nitrocellulose membrane, which is covered on the backing and is made of nitrocellulose and a hydrophilic polymer.

[0012] The present invention also provides an application of a backed nitrocellulose membrane in in vitro diagnostic reagents with different requirements for NC membrane pore size.

[0013] The role and effect of invention

[0014] The present invention provides a method for preparing a backed nitrocellulose membrane. By adjusting the amount of pore-forming agent, the pore size of the membrane can be well controlled during the membrane preparation process. The resulting nitrocellulose membrane has the characteristics of uniform pore size and controllable size, and is suitable for in vitro diagnostic reagents with different requirements for NC membrane pore size.

[0015] The present invention provides a method for preparing a backed nitrocellulose membrane by adding a hydrophilic polymer to the casting solution. On the one hand, this effectively adjusts the hydrophilicity of the NC membrane and the foaming problem during the production process. On the other hand, compared with small molecule surfactants, the hydrophilic polymer is not easily lost, thus ensuring the stability of the NC membrane quality during storage.

[0016] The preparation method of the backed nitrocellulose membrane of the present invention has simple conditions and processes, and is easy to mass-produce.

[0017] The backed nitrocellulose membrane of the present invention has the characteristics of uniform and controllable pore size, good hydrophilicity, strong protein binding ability and large-scale production, and has broad application prospects in the field of in vitro diagnostic reagents. Attached Figure Description

[0018] Figure 1 This is a flowchart illustrating a method for preparing a backed nitrocellulose membrane according to an embodiment of the present invention.

[0019] Figure 2 This is a comparison of the capillary migration speeds of samples 1, 11, 12, and 13 in the test examples of this invention. Detailed Implementation

[0020] To make the technical means, creative features, objectives and effects of the present invention easy to understand, the following embodiments, in conjunction with the accompanying drawings, specifically illustrate a backed nitrocellulose membrane of the present invention, its preparation method and application.

[0021] <Example>

[0022] Figure 1 This is a flowchart illustrating a method for preparing a backed nitrocellulose membrane according to an embodiment of the present invention.

[0023] like Figure 1 As shown, this embodiment provides a method for preparing a backed nitrocellulose membrane, including the following steps:

[0024] S10: Dissolve nitrocellulose, pore-forming agent, and hydrophilic polymer in DMF and / or DMAC at a ratio of (10–50) wt% : (1–30) wt% : (1–15) wt%. After filtration, allow the solution to stand for at least 4 hours to remove bubbles, resulting in a homogeneous and stable nitrocellulose casting solution.

[0025] The pore-forming agent includes polyvinylpyrrolidone and / or polyethylene glycol, and the hydrophilic polymer includes any one or more of sulfonated polyethersulfone, polyaniline or polyacrylamide.

[0026] S20, using a doctor blade with a film thickness of 0.38 mm, the nitrocellulose casting solution is coated onto a PVC backing with a thickness of 0.06 mm to 0.10 mm to form a precursor film;

[0027] S30, the precursor film is separated into phases in an aqueous solution of any one or more of DMF, DMAC, isopropanol or ethanol with a concentration not exceeding 25wt% to obtain a semi-wet film.

[0028] S40, the semi-wet membrane is washed in a water bath at 20°C for 30 seconds and then dried to obtain a backed nitrocellulose membrane.

[0029] This embodiment also provides a backed nitrocellulose membrane, which is prepared by the method for preparing a backed nitrocellulose membrane in this embodiment.

[0030] The nitrocellulose membrane with backing provided in this embodiment includes: a PVC backing with a thickness of 0.06 mm to 0.10 mm; and a nitrocellulose membrane covering the backing, the material of which is nitrocellulose and a hydrophilic polymer.

[0031] Specifically, the parameters for the preparation process of the backed nitrocellulose membrane in this embodiment are selected as follows: In step S10, 200g of nitrocellulose, 300g of polyethylene glycol-400 as the pore-forming agent, and 10g of sulfonated polyethersulfone (sulfonation degree ≥30%) as the hydrophilic polymer are dissolved in 490g of DMAC by mechanical stirring at room temperature; in step S20, the thickness of the membrane scraped by the doctor blade is 0.38mm; in step S30, the solution used for phase separation is an aqueous solution of 25wt% ethanol, and the immersion time is 3min.

[0032] <Test Example>

[0033] This test example uses a method for preparing a backed nitrocellulose membrane provided in the embodiment to prepare 15 kinds of films, which are referred to as samples 1 to 15. The specific parameter selection of the preparation process of samples 1 to 15 is shown in Table 1.

[0034] Table 1 (Specific parameter selection for the preparation process of samples 1-15)

[0035]

[0036] In this test example, two thin films were prepared according to the prior art “Example 1 in Chinese Patent CN114130373A” and “Example 2 in Chinese Patent CN114130373A”, respectively, and were designated as Sample 16 and Sample 17.

[0037] This test example performs the following performance characterization tests on samples 1 to 17:

[0038] (1) Use a stopwatch to record the time (in seconds) it takes for purified water to “climb” from the bottom of the membrane to the top 4 cm via capillary action to test the capillary migration speed of the membrane.

[0039] (2) The capillary migration effect of the membrane is evaluated by observing the rising state of the liquid level line during the capillary migration experiment.

[0040] (3) The pore size of the membrane was tested in accordance with the standard GB / T 38949-2020 "Determination of Pore Size of Porous Membranes - Standard Particle Method".

[0041] (4) The protein rejection rate of the membrane was determined using bovine serum albumin (BSA). A BSA solution with a molecular weight of 67000 g / mol was dissolved in NaCl solution (0.2 mol / L). This solution was poured into an ultrafiltration vessel and filtered through a nitrocellulose membrane at 0.2 MPa. The rejection rate of BSA was calculated based on the bovine serum albumin standard curve.

[0042] The results of the above performance characterization tests are shown in Table 2.

[0043] Table 2 (Performance characterization test results for samples 1–17)

[0044]

[0045]

[0046] As can be seen from samples 1, 8, 9 and 10 in Tables 1 and 2, the pore size of the cellulose nitrate membrane with backing in this test example can be controlled by adjusting the amount of pore-forming agent.

[0047] Figure 2 This is a comparison of the capillary migration velocities of samples 1, 11, 12, and 13 from the test examples of this invention. The results are shown in Tables 1 and 2. Figure 2 As shown, the "migration speed" value of the backed nitrocellulose membrane in this test example decreases with the increase of hydrophilic polymer (the "migration speed" value is the time it takes for purified water to "climb" from the bottom of the membrane to the top 4cm through capillary action; the lower the value, the faster the migration speed and the better the hydrophilicity of the membrane). That is, the hydrophilicity of the membrane can be controlled by adjusting the amount of hydrophilic polymer.

[0048] As shown in Tables 1 and 2, compared to sample 1, sample 14 is a dense membrane with a pore size much smaller than 1 μm, while sample 15 has poor hydrophilicity and a large migration speed. This indicates that the pore size and hydrophilicity of the backed nitrocellulose membrane of the present invention are controlled by pore-forming agents and hydrophilic polymers.

[0049] As can be seen from samples 1, 16 and 17 in Tables 1 and 2, the backed nitrocellulose membrane in this test example has better hydrophilicity. This is because the hydrophilic polymer used in this test example has better hydrophilicity than common surfactants and polysulfone additives.

[0050] Those skilled in the art should understand that this invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to this invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a backed nitrocellulose membrane, characterized by, Includes the following steps: S10, nitrocellulose, pore-forming agent, and hydrophilic polymer are dissolved in DMF and / or DMAC at a ratio of (10-50) wt%: (1-30) wt%: (1-15) wt%, and then filtered and degassed to obtain a homogeneous and stable nitrocellulose casting solution. The pore-forming agent includes polyvinylpyrrolidone and / or polyethylene glycol, and the hydrophilic polymer includes any one or more of sulfonated polyethersulfone, polyaniline, or polyacrylamide. S20, the nitrocellulose casting solution is coated onto a PVC backing with a thickness of 0.06 mm to 0.10 mm to form a precursor film. The tool used for film forming is a scraper with a film thickness of 0.38 mm; S30, the precursor film is separated into phases in a solution to obtain a semi-wet film. The solution includes an aqueous solution of any one or more of DMF, DMAC, isopropanol or ethanol with a concentration not exceeding 25 wt%. S40, the semi-wet membrane is washed and dried to obtain a nitrocellulose membrane with a backing. The backed nitrocellulose membrane is a microporous membrane. The micropore size of the backed nitrocellulose membrane can be controlled by adjusting the amount of the pore-forming agent, and the hydrophilic properties of the backed nitrocellulose membrane can be controlled by adjusting the amount of the hydrophilic polymer.

2. The method for preparing a backed nitrocellulose membrane according to claim 1, characterized in that: wherein, In step S10, the degassing process involves letting the mixture stand for at least 4 hours to remove bubbles.

3. The method for preparing a backed nitrocellulose membrane according to claim 1, characterized in that: in, In step S40, the washing method is a water bath at 20 ℃~50 ℃ for at least 30 s.

4. A nitrocellulose membrane with a backing, characterized in that, It is prepared by the method for preparing a backed nitrocellulose membrane according to any one of claims 1 to 3. The backed nitrocellulose membrane comprises: The PVC backing is 0.06 mm to 0.10 mm thick; and A nitrocellulose membrane, covering the backing, is made of nitrocellulose and the hydrophilic polymer.

5. The application of a backed nitrocellulose membrane as described in claim 4 in in vitro diagnostic reagents with different requirements for NC membrane pore size.

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