Composite CaCO3-pullulan membrane as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of paper-based microfluidic analysis, and particularly relates to a composite CaCO3-pullulan membrane as well as a preparation method and application thereof. The composite CaCO3-Pulullan film is formed by divalent calcium ions and Pulullan, the divalent calcium ions and the Pulullan can generate chelation reaction, the composite CaCO3-Pulullan film is a uniform opaque milk white film, and the thickness of the composite CaCO3-Pulullan film is 60-100 [mu] m. The composite CaCO3-Pulullan membrane is prepared by taking a Pulullan solution, calcium carbonate and polyvinyl alcohol mixed solution as precursors, has toughness and folding resistance, has the characteristics of flow control, timed flow closing and the like when being embedded into a paper-based microfluid device, and can realize control on flow rates of complexing solutions with different concentrations.

Description

Technical Field

[0001] The present invention belongs to the technical field of paper-based microfluidic analysis, and in particular relates to a composite CaCO3-pullulan membrane and a preparation method and application thereof. Background Art

[0002] Microfluidic technology, due to its highly miniaturized and integrated features, is widely used in medical diagnosis, food safety analysis, and environmental monitoring. While existing microfluidic systems offer advantages such as low reagent consumption, high-throughput separation and detection, and rapid analysis, their manufacturing typically relies on complex silicon-based microelectronics processing, which not only increases production costs but also limits their widespread application in resource-limited areas and on-site testing scenarios. In the field of paper-based microfluidic devices, although their low cost and portability have led to their widespread use in medical diagnosis and food safety testing, the paper-based material itself has the inherent defect of being unable to effectively control the flow rate of the solution.

[0003] Therefore, developing a new material that can achieve precise flow rate control is of great significance for improving the performance of paper-based microfluidic devices. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a composite CaCO3-pullulan membrane, a preparation method and application thereof. The present invention uses a pullulan polysaccharide solution, a calcium carbonate and a polyvinyl alcohol mixed solution as precursors to prepare a composite CaCO3-pullulan membrane. The composite CaCO3-pullulan membrane is embedded in a paper-based microfluidic device and has the characteristics of flow control and timed flow shutdown, and can realize the control of the flow rate of complex solutions of different concentrations.

[0005] The technical solutions adopted by the present invention to solve the above problems are as follows:

[0006] A composite CaCO3-pullulan film is formed from divalent calcium ions capable of undergoing a chelating reaction and pullulan polysaccharide. The composite CaCO3-pullulan film is a uniform, opaque, milky white film with a thickness of 60 to 100 μm. The composite CaCO3-pullulan film is tough and fold-resistant.

[0007] Preferably, the composite CaCO3-pullulan film comprises the following preparation raw materials: pullulan polysaccharide solution, calcium carbonate and polyvinyl alcohol mixed solution;

[0008] The pullulan solution comprises the following components: pullulan, methoxy polyethylene glycol, citric acid, anhydrous ethanol, and deionized water; the mass contents of the deionized water, pullulan, methoxy polyethylene glycol, and citric acid are in the range of 92% to 93%, 4.2% to 4.8%, 1.6% to 2.0%, and 0.8% to 1.4%, respectively; and the volume ratio of the deionized water to the anhydrous ethanol is 100:(1 to 1.5);

[0009] The calcium carbonate and polyvinyl alcohol mixed solution comprises the following components in percentage by mass: 96% to 98% of deionized water, 1.5% to 2% of polyvinyl alcohol, and 0.5% to 1.5% of light calcium carbonate.

[0010] The present invention provides a method for preparing the composite CaCO3-pullulan film, comprising the following steps:

[0011] S1. Prepare pullulan solution;

[0012] S2. Preparation of a mixed solution of calcium carbonate and polyvinyl alcohol;

[0013] S3. Mix the pullulan polysaccharide solution with the mixed solution of calcium carbonate and polyvinyl alcohol, continue stirring to form a uniform milky white liquid, and then pour it onto a flat surface to dry into a film to obtain a composite CaCO3-pullulan film.

[0014] Preferably, the method for preparing the pullulan solution in step S1 comprises: adding pullulan to deionized water and stirring until dissolved; then adding methoxy polyethylene glycol, citric acid and anhydrous ethanol and stirring until dissolved to obtain the pullulan solution.

[0015] Preferably, the method for preparing the mixed solution of calcium carbonate and polyvinyl alcohol in step S2 includes: heating deionized water, then adding polyvinyl alcohol, stirring until dissolved, then adding light calcium carbonate, and continuing to stir until uniformly dispersed to obtain a mixed solution of calcium carbonate and polyvinyl alcohol.

[0016] Preferably, in step S2, the temperature of the deionized water is 70-80°C.

[0017] The present invention also provides the use of the composite CaCO3-pullulan membrane as a soluble control valve in a paper-based microfluidic device.

[0018] A paper-based microfluidic device comprises the composite CaCO3-pullulan membrane described above. The composite CaCO3-pullulan membrane serves as a soluble control valve.

[0019] Preferably, the paper-based microfluidic device comprises:

[0020] Paper-based materials;

[0021] A microfluidic channel formed on the paper-based material by blocking with a hydrophobic material;

[0022] a strip-shaped hole provided on a microfluidic channel, wherein the microfluidic channel is separated by the strip-shaped hole;

[0023] The composite CaCO3-pullulan film and the polyester film with hydrophilic surface treatment respectively cover the upper and lower surfaces of the strip-shaped hole to form a closed air gap.

[0024] Preferably, the paper-based material can be a clean paper material formed of inert cellulose, having a capillary structure, and capable of absorbing water, including but not limited to qualitative filter paper and quantitative filter paper.

[0025] Preferably, the hydrophobic material can be selected from hydrophobic materials that are easy to process and easy to combine with paper-based materials, including but not limited to wax.

[0026] Preferably, the method for preparing the polyester film having a hydrophilic surface treatment comprises: performing surface treatment on the polyester film using a plasma cleaning machine.

[0027] Preferably, the surface treatment power is 100W to 150W, and the time is 100s to 200s.

[0028] The present invention has the following beneficial effects:

[0029] The present invention uses pullulan solution, calcium carbonate and polyvinyl alcohol mixed solution as precursors, and utilizes the chelating properties and film-forming ability of calcium carbonate and pullulan to prepare a composite CaCO3-pullulan film. The composite film has excellent film-forming ability and good solubility, low preparation cost, simple operation and good biocompatibility. 2+ The chelation constant K MY The dissolution rate of the composite CaCO3-pullulan film of the present invention will change accordingly. MY The larger the value, the shorter the membrane dissolution time and the shorter the flow distance, allowing for precise control of the solution flow rate. Compared to pullulan membranes, the composite CaCO3-pullulan membrane performs better in terms of solubility and flow rate control, demonstrating its significant advantages in paper-based microfluidics technology.

[0030] Based on the excellent solubility characteristics of the composite CaCO3-pullulan membrane, the composite CaCO3-pullulan membrane prepared by the present invention was embedded in a paper-based microfluidic device and the results were shown in Table 1. MYThe device, which features high selectivity and sensitivity, enables precise flow rate control and timed flow shut-off for a variety of complexing solutions, resolving the inability of conventional paper-based microfluidics to precisely control flow rates. The device is simple to use, convenient, quick, low-cost, and highly portable, and is suitable for rapid on-site testing and multi-channel analysis in fields such as biomedical diagnostics and environmental testing, with broad potential applications and promising economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 : Synthesis route of composite pullulan membrane.

[0032] Figure 2 : Relationship between the concentration of each mobile solution and the dissolution time of the composite CaCO3-pullulan film.

[0033] Figure 3 : Synthesis process of paper-based microfluidic devices.

[0034] Figure 4 : Optical contact angle / interfacial tension meter display diagrams before and after polyester film treatment.

[0035] Figure 5 : Relationship diagram between concentration of each flowing solution and flow distance.

[0036] Figure 6 : Relationship between dissolution time and flow distance of composite CaCO3-pullulan film. DETAILED DESCRIPTION

[0037] To make the technical problems, technical solutions, and technical advantages of the present invention more clear, the following will be described in detail with reference to specific examples. However, the scope of protection of the present invention is not limited to the following specific embodiments. The embodiments described are only part of the embodiments of the present invention, not all of the embodiments, and are not limitations of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0038] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0039] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0040] The quantitative tests in the following examples were all performed in triplicate, and the data are the average values ​​or the average values ​​± standard deviations of the three repeated experiments.

[0041] Example 1: Preparation of composite CaCO3-pullulan membrane

[0042] The synthesis route of the composite CaCO3-pullulan membrane is as follows Figure 1 As shown, the specific steps include:

[0043] (1) Preparation of pullulan solution: 20.0 g of deionized water was weighed into a 100 mL beaker using an electronic balance, and a magnetic stirrer was added, followed by stirring on a magnetic heating stirrer; 1.0 g of pullulan was weighed, and added into the beaker in small amounts and multiple times, and stirred until the pullulan was completely dissolved; after the pullulan was completely dissolved, 0.40 g of methoxypolyethylene glycol, 0.24 g of citric acid, and 0.30 mL of anhydrous ethanol were weighed, and added into the beaker in sequence, and stirred to dissolve.

[0044] (2) Preparation of a mixed solution of calcium carbonate and polyvinyl alcohol: 19.6 g of deionized water was weighed into a 100 mL beaker using an electronic balance, the deionized water was heated to 70°C, a magnetic stirrer was added, and the mixture was stirred on a magnetic stirrer; 0.4 g of polyvinyl alcohol was weighed and added to the beaker in small amounts and multiple times, and the mixture was stirred until the polyvinyl alcohol was completely dissolved; after the polyvinyl alcohol was completely dissolved, 0.2 g of light calcium carbonate was weighed and added to the beaker in small amounts and multiple times, and the mixture was stirred until the calcium carbonate was evenly distributed in the solution.

[0045] (3) The prepared pullulan solution was slowly poured into the mixed solution of calcium carbonate and polyvinyl alcohol. After adding a magnetic stirrer, the mixture was heated to 70°C and stirred continuously for 12 hours until a uniform opaque milky white mixed solution was formed. 3.5 g of the milky white mixed solution was added to several round glass culture dishes with a diameter of 60 mm using a rubber-tipped dropper. The round glass culture dishes containing the milky white mixed solution were placed in a fume hood and dried at 25°C and RH = 45% for 24 to 36 hours to prepare multiple composite CaCO3-pullulan films.

[0046] Example 2: Preparation of solutions of different concentrations

[0047] (1) Prepare 100 mL of 0.01 mol / L, 0.05 mol / L, and 0.1 mol / L DTPMPA solutions. Pipette 0.58 mL, 2.92 mL, and 5.85 mL of a 50% DTPMPA aqueous solution into three clean beakers, dilute, transfer to a 100 mL volumetric flask, adjust to volume, pour into a 100 mL plastic bottle, and label.

[0048] (2) Prepare 100 mL of 0.01 mol / L, 0.05 mol / L, and 0.1 mol / L HEDP solutions. Pipette 3.43 mL, 17.17 mL, and 34.34 mL of 60% HEDP aqueous solution into three clean beakers, dilute, transfer to a 100 mL volumetric flask, adjust to volume, pour into a 100 mL plastic bottle, and label.

[0049] (3) Prepare 100 mL of 0.01 mol / L, 0.05 mol / L, and 0.1 mol / L EDTA-2Na solutions. Weigh 0.3722 g, 1.1861 g, and 3.7224 g of EDTA-2Na solid into three clean beakers, stir and dissolve, transfer to a 100 mL volumetric flask, make up to volume, pour into a 100 mL plastic bottle, and label it.

[0050] (4) Prepare 100 mL of 0.01 mol / L, 0.05 mol / L, and 0.1 mol / L sodium metasilicate solutions. Weigh 0.1364 g, 0.6818 g, and 1.3636 g of solid sodium metasilicate into three clean beakers, stir and dissolve. Transfer the solution to a 100 mL volumetric flask, adjust to volume, pour into a 100 mL plastic bottle, and label it.

[0051] (5) Prepare 100 mL of 0.01 mol / L, 0.05 mol / L, and 0.1 mol / L sodium tripolyphosphate solutions. Weigh 0.4085 g, 2.0437 g, and 4.0867 g of solid sodium tripolyphosphate into three clean beakers, stir and dissolve, transfer to a 100 mL volumetric flask, adjust to volume, pour into a 100 mL plastic bottle, and label it.

[0052] Example 3: Exploring the dissolution time of composite CaCO3-pullulan film in various flowing solutions

[0053] Take 10 mL of the mobile solution to be tested prepared in Example 2 into a plastic culture dish, use tweezers to pick up the composite CaCO3-pullulan film prepared in Example 1 and place it into the mobile solution, and use a timer to record the time from the composite CaCO3-pullulan film being placed in the solution to becoming a transparent film.

[0054] The test results of the dissolution time of the composite CaCO3-pullulan film in each flow solution are shown in Table 1 and Figure 2 shown.

[0055] Table 1:

[0056]

[0057] It can be seen from Table 1 that in the same solution, as the solution concentration increases, the time required for the composite CaCO3-pullulan film to dissolve into a transparent film in the flowing solution becomes shorter.

[0058] like Figure 2 As shown in the figure, the solution concentration is inversely proportional to the dissolution time of the composite CaCO3-pullulan film, and at the same concentration of different solutions, the solution and Ca 2+ Chelation constant K MY The larger the value, the shorter the dissolution time.

[0059] Example 4: Preparation of paper-based microfluidic device The synthetic route of the paper-based microfluidic device is as follows Figure 3 As shown, the specific steps include:

[0060] (1) First, make a paper-based microfluidic channel. Figure 3 As shown in Figure A. Use a paper cutter to cut qualitative filter paper into a 3 cm × 8 cm rectangular paper base. Mark 2.5 cm on the short side of one end of the paper base with a pencil. Use flat hole pliers to cut a 3 mm × 13 mm strip hole at the marked point, with the horizontal width of the strip hole exceeding 2 to 3 mm from the two long lines. Select one side of the rectangular paper base and draw two long lines 1 cm from the long sides at both ends with a pencil. Place the beaker containing the slicing paraffin wax in a magnetic heating stirrer set to 85°C, with only the heating function turned on, and heat until the slicing paraffin wax is completely melted. Then treat the two long sides of the paper-based microfluidic system using paraffin wax immersion, with the paraffin wax immersion portion not exceeding the two drawn long lines, so that a dense wax layer measuring 1 cm × 8 cm is attached to each long side, resulting in a 1 cm × 8 cm paper-based microfluidic channel in the center of the paper base.

[0061] (2) Then, composite CaCO3-pullulan membrane and pullulan membrane strip membrane were prepared respectively. Figure 3 As shown in Figure B, the experimentally prepared composite CaCO3-pullulan membrane and pullulan membrane were each cut into 4 mm × 15 mm strips using flat-hole pliers. The strips were slightly larger than the strip holes. Solid glue was applied to the junction of the strip hole and the wax layer on one side of the paper substrate. The strips were then fixed above the strip holes, with the side containing the strips serving as the front of the paper-based microfluidic device.

[0062] (3) Finally, a strip of polyester film was made. A 6 cm × 10 cm rectangular polyester film was cut out using a paper cutter and placed in a plasma cleaning machine for surface treatment. The treatment power was 150 W and the treatment time was 200 s.

[0063] like Figure 3 C. Cut the treated polyester film into 4mm x 15mm rectangular strips with scissors. Place the strips over the strip-shaped holes on the other side of the paper substrate, with the hydrophilic side of the film facing the holes. Secure the strips to the paper-based device with transparent tape, with the side containing the polyester film serving as the back of the paper-based microfluidic device. Gently press the strips at the junction with the paper-based microfluidic channel to create a closed air gap between the strips and the film.

[0064] Actual picture Figure 3 As shown in D. The shorter end of the paper substrate from the strip hole is the bottom end of the strip hole. The upper end of the strip hole is the measurement starting point. The position reached by the solution after 30 minutes of flow is the measurement end point. The distance from the starting point to the end point is the flow distance of the solution.

[0065] like Figure 4 As shown in the figure, the contact angle of the polyester film before and after treatment was measured using an optical contact angle / interfacial tension meter, and the change in its surface hydrophilicity was measured. It was found that the contact angle decreased from 68° to 25°. The contact angle decreased, and the hydrophilicity of the polyester film surface increased, which was conducive to the smooth passage of the flowing solution at the strip pores.

[0066] Example 5: Study on the flow rate control of the flowing solution using a paper-based microfluidic device embedded with a composite CaCO3-pullulan membrane

[0067] 15 mL of the flow solution to be tested prepared in Example 2 was placed in a plastic culture dish. The lower end of the paper-based microfluidic device embedded with a composite pullulan membrane fixed on a glass slide was tilted about 11° and placed into the plastic culture dish containing the flow solution. The entire flow process of the solution was observed for 30 minutes, and the flow distance of the flow solution in the paper-based microfluidic device after 30 minutes was recorded.

[0068] The test results of the paper-based microfluidic device embedded with the composite CaCO3-pullulan membrane for controlling the flow rate of the flowing solution are shown in Table 2.

[0069] Table 2:

[0070] Concentration + flow distance / cm 0.01mol / L 0.05mol / L 0.1mol / L <![CDATA[With Ca 2+ Chelation constant K MY > DTPMPA 2.26 1.62 1.06 16.2 HEDP 2.86 2.00 1.13 13.1 EDTA-2Na 3.53 3.46 2.86 10.7 Sodium metasilicate 4.23 4.15 3.50 8.0 Sodium tripolyphosphate 4.40 4.13 3.67 6.9 Deionized water - 4.67 - -

[0071] As shown in Table 2, at 30 min, in the same solution, as the concentration of the solution increases, the flow distance of the solution on the paper-based microfluidic device becomes shorter. 2+ The chelation constant K is inversely proportional to MY The larger it is, the shorter the distance the solution has to flow.

[0072] Figure 5 is the relationship between the concentration of each flowing solution and the flow distance; Figure 5 As shown, the solution concentration is inversely proportional to the flow distance, and at the same concentration of different solutions, the solution and Ca 2+ Chelation constant K MY The larger the value, the shorter the flow distance.

[0073] Figure 6 The relationship between the dissolution time and flow distance of the composite CaCO3-pullulan film is shown in FIG. Figure 6As shown in the figure, the flow distance of the solution in the paper-based microfluidic device is proportional to the dissolution time of the composite CaCO3-pullulan film in the solution. 2+ Chelation constant K MY The larger the value, the shorter the dissolution time of the composite CaCO3-pullulan film in the solution.

[0074] In summary, as the solution concentration and Ca 2+ The chelation constant K MY The dissolution rate of the composite CaCO3-pullulan film provided by the present invention will change accordingly. MY The larger the value, the shorter the dissolution time of the membrane and the shorter the flow distance, thus achieving precise control of the solution flow rate. Based on its excellent dissolution characteristics and controllability, the composite CaCO3-pullulan membrane can be applied to a variety of complex substances and medical diagnosis, environmental testing and other fields. MY The solution with the highest value has good selectivity and sensitivity, can realize precise control of flow rate and timed flow shutdown, and has broad application prospects and market potential.

[0075] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0076] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. To avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0077] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A composite CaCO3-pullulan membrane, characterized in that: It is formed by divalent calcium ions capable of undergoing chelating reaction and pullulan polysaccharide; the composite CaCO3-pullulan film is a uniform, opaque milky white film with a thickness of 60 to 100 μm.

2. The composite CaCO3-pullulan membrane according to claim 1, characterized in that The composite CaCO3-pullulan film comprises the following preparation raw materials: pullulan polysaccharide solution, calcium carbonate and polyvinyl alcohol mixed solution; The pullulan solution comprises the following components: pullulan, methoxy polyethylene glycol, citric acid, anhydrous ethanol, and deionized water; the mass contents of the deionized water, pullulan, methoxy polyethylene glycol, and citric acid are in the range of 92% to 93%, 4.2% to 4.8%, 1.6% to 2.0%, and 0.8% to 1.4%, respectively; and the volume ratio of the deionized water to the anhydrous ethanol is 100:(1 to 1.5); The calcium carbonate and polyvinyl alcohol mixed solution comprises the following components in percentage by mass: 96% to 98% of deionized water, 1.5% to 2% of polyvinyl alcohol, and 0.5% to 1.5% of light calcium carbonate.

3. A method for preparing the composite CaCO3-pullulan film according to claim 2, characterized in that: The steps include: S1. Prepare pullulan solution; S2. Preparation of a mixed solution of calcium carbonate and polyvinyl alcohol; S3. Mix the pullulan polysaccharide solution with the mixed solution of calcium carbonate and polyvinyl alcohol, continue stirring to form a uniform milky white liquid, and then pour it onto a flat surface to dry into a film to obtain a composite CaCO3-pullulan film.

4. The method for preparing a composite CaCO3-pullulan film according to claim 3, characterized in that: The method for preparing the pullulan solution in step S1 comprises: adding pullulan to deionized water and stirring until dissolved; then adding methoxy polyethylene glycol, citric acid and anhydrous ethanol and stirring until dissolved to obtain the pullulan solution.

5. The method for preparing the composite CaCO3-pullulan film according to claim 3, characterized in that: The method for preparing the mixed solution of calcium carbonate and polyvinyl alcohol in step S2 includes: heating deionized water, then adding polyvinyl alcohol, stirring until dissolved, then adding light calcium carbonate, and continuing to stir until uniformly dispersed to obtain a mixed solution of calcium carbonate and polyvinyl alcohol.

6. The method for preparing a composite CaCO3-pullulan film according to claim 5, characterized in that: In step S2, the temperature of the deionized water is 70-80°C.

7. Use of the composite CaCO3-pullulan membrane according to any one of claims 1 to 2 or the composite CaCO3-pullulan membrane prepared by the preparation method according to any one of claims 3 to 6 as a soluble control valve in a paper-based microfluidic device.

8. A paper-based microfluidic device, characterized in that The invention comprises the composite CaCO3-pullulan film according to any one of claims 1 to 2 or the composite CaCO3-pullulan film prepared by the preparation method according to any one of claims 3 to 6.

9. The paper-based microfluidic device according to claim 8, characterized in that include: Paper-based materials; A microfluidic channel formed on the paper-based material by blocking with a hydrophobic material; a strip-shaped hole provided on a microfluidic channel, wherein the microfluidic channel is separated by the strip-shaped hole; The composite CaCO3-pullulan film and the polyester film with hydrophilic surface treatment respectively cover the upper and lower surfaces of the strip-shaped hole to form a closed air gap.

10. The paper-based microfluidic device according to claim 9, wherein The method for preparing the polyester film with hydrophilic surface treatment comprises: performing surface treatment on the polyester film by using a plasma cleaning machine; the power of the surface treatment is 100W to 150W, and the time is 100s to 200s.

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