A method for preparing a high-stability wearable lactate biosensor based on prussian blue analogues

Abstract

The application belongs to the technical field of sensing, and discloses a preparation method of a high-stability wearable lactic acid biosensor based on Prussian blue analogues. The method comprises the following steps: (1) constructing a three-electrode sensor array on a flexible substrate through a screen printing technology; (2) sequentially depositing gold nanoparticles and a PB-NiHCF composite catalytic layer on the surface of a working electrode through a cyclic voltammetry method; (3) finally obtaining the sensor by curing under the condition of 4 DEG C and avoiding light after layer-by-layer modification of a chitosan-carbon nanotube conductive layer, lactic acid oxidase and a diffusion-limiting membrane. The sensor significantly improves the stability under physiological pH conditions through the synergistic catalytic effect of PB-NiHCF, the linear detection range reaches 30 mM, the sensitivity is 223.94 nA mM ‑1 cm ‑2 , and the sensor is suitable for real-time monitoring of sweat lactic acid.

Description

Technical Field

[0001] This invention belongs to the field of sensing technology and relates to a method for preparing a highly stable wearable lactic acid biosensor based on a Prussian blue analogue. Background Technology

[0002] Lactate monitoring is generally used to assess athletes' maximum performance in high-intensity exercise and endurance activities, but lactate levels can also increase under certain pathological conditions, such as heart disease, pulmonary embolism, liver disease, diabetes, and other illnesses. Therefore, blood lactate levels are currently used as an indicator of health and clinical status.

[0003] Prussian blue-based biosensors are currently widely used for the detection of blood lactate. Prussian blue (PB) is an important polynuclear metal cyanide with a cubic crystal structure, in which Fe... 2+ and Fe 3+ The alternating ions on the face-centered cubic (FCC) lattice enable Prussian blue to function as a redox medium, characterized by: 1. Prussian blue has the properties of zeolite, and can rapidly replace alkali metal ions and transition metal ions of different valence states in aqueous solution, causing them to undergo redox reactions; 2. Prussian blue exhibits good electrochemical activity and reversibility, which makes it an ideal electrochemical sensor material. 3. Prussian blue, as a redox medium, reduces the reduction potential to about 0 V (relative to Ag / AgCl), thereby eliminating the need for an external power supply to activate the sensor. At the same time, it avoids interference currents caused by the oxidation of electrochemically active substances in biological samples under high potential conditions, thus improving anti-interference capability. 4. Prussian blue has a relatively low production cost and a relatively simple preparation process, which is conducive to large-scale production and application.

[0004] While Prussian blue offers numerous advantages as a redox medium, traditional PB-based biosensors suffer from poor stability. This is because the process of lactate oxidase catalyzing the oxidation of lactate to pyruvate in the human body produces hydrogen peroxide (H₂O₂) as a byproduct, and the reduction product of H₂O₂ is OH⁻. - It will disrupt the Fe-(CN)-Fe framework of the PB lattice (reaction: PB + OH-). - → Fe(OH)3+ [Fe(CN)6] 3- This causes Prussian blue to gradually degrade under physiological conditions. This invention addresses this by introducing a nickel ferrite (NiHCF) epitaxial layer into Prussian blue, utilizing Ni... 2+ Its inertness and small ionic radius can effectively suppress OH. -The PB-NiHCF active layer in this invention, as a Prussian blue analogue, possesses both the redox properties of Prussian blue and can withstand pH corrosion while maintaining consistent electrochemical catalytic activity. Based on this Prussian blue analogue, a wearable lactic acid biosensor can continuously and non-invasively monitor and analyze blood lactic acid levels in the human body. Summary of the Invention

[0005] In view of the problems existing in the prior art, the present invention provides a highly stable wearable lactate biosensor based on a Prussian blue analogue. This lactate biosensor significantly improves its stability and long-term stability under physiological pH conditions through the synergistic catalytic effect of PB-NiHCF. This wearable lactate biosensor can be mass-produced using screen printing, giving it good batch-to-batch stability and mechanical stability.

[0006] The technical solution of this invention: A method for preparing a highly stable wearable lactic acid biosensor based on a Prussian blue analogue, comprising the following steps: S1. Flexible electrode fabrication: The flexible electrode was fabricated by screen printing on a polyethylene terephthalate (PET) substrate to construct a three-electrode sensor. The three-electrode sensor includes a working electrode, a counter electrode, and a reference electrode. The area of ​​the counter electrode is 1.4 times that of the working electrode, and the area of ​​the reference electrode is the same as that of the working electrode. S2. Activation of working electrode: The flexible electrode was cleaned by 1 to 30 cycles of cyclic voltammetry (CV) using 0.5 M H2SO4 solution at a scan rate of 500 mV / s within a potential window of -1.2 to 1 V. S3. Working electrode interface modification: S3.1 Deposit gold nanoparticles (AuNPs) layers by performing 100 to 3000 pulse voltammetry cycles in a 2–50 mM HAuCl4·3H2O aqueous solution within a potential window of -0.9 to 0.9 V; S3.2 Electrodeposition of PB layer: In an aqueous solution containing 2.5~3 mM FeCl3, 2.5~3 mM K3[Fe(CN)6], 0.01~0.1 M HCl and 0.01~0.1 M KCl, CV was performed 2~20 times at a scan rate of 50~100 mV / s within a potential window of -0.2~0.6 V to deposit a PB layer on the gold nanoparticle (AuNPs) layer; S3.3 Electrodeposition of NiHCF layer: In an aqueous solution containing 0.5~1 mM NiCl2·6H2O, 0.5~1 mM K3[Fe(CN)6], 0.01~0.1 M HCl and 0.01~0.1 M KCl, CV was performed 1~50 times at a potential window of 0~0.8 V at a scan rate of 50~100 mV / s to deposit a NiHCF layer on the PB layer.

[0007] S4. Functionalization of the working electrode: Functionalization was carried out on the working electrode modified in step S3: First, chitosan-multi-walled carbon nanotube dispersion was drop-coated and dried; then lactate oxidase solution was drop-coated and stabilized for 12-24 h; finally, confined diffusion membrane solution was drop-coated and dried to obtain a highly stable wearable lactate biosensor based on Prussian blue analogue. The preparation method of S4.1 chitosan-multi-walled carbon nanotube dispersion is as follows: Chitosan was dissolved in acetic acid and stirred until dissolved. The dissolved solution was then added to water to prepare a 1% (w / w) chitosan solution. The chitosan solution was then mixed with multi-walled carbon nanotubes and stirred until uniformly dispersed to prepare a chitosan-multi-walled carbon nanotube dispersion.

[0008] Furthermore, the mass ratio of chitosan to acetic acid is 1:2.

[0009] Furthermore, the amount of multi-walled carbon nanotubes in the chitosan-multi-walled carbon nanotube dispersion is 0.5~4 mg / mL.

[0010] The preparation method of S4.2 lactate oxidase solution is as follows: First, prepare a 0.02 M phosphate buffer solution (PBS) with pH=7.4. Then, mix bovine serum albumin and lactate oxidase in the phosphate buffer solution (pH=7.4).

[0011] Furthermore, the bovine serum albumin content in the lactate oxidase solution is 5-15 mg / mL.

[0012] Furthermore, the lactate oxidase content in the lactate oxidase solution is 10~40 mg / mL.

[0013] The preparation method of the confined diffusion membrane solution in S4.3 is as follows: Polyvinyl chloride (PVC) and dioctyl sebacate (DOS) were weighed and dissolved in a solution of tetrahydrofuran (THF) to prepare a diffusion-limiting membrane solution. Furthermore, the mass ratio of polyvinyl chloride to dioctyl sebacate in the diffusion membrane solution is 1:1~6.

[0014] Furthermore, the concentration of polyvinyl chloride in the diffusion membrane solution is limited to 1~33 mg / mL.

[0015] The beneficial effects of this invention are: 1. The activated flexible screen-printed sensor exhibits consistent electrochemical test current background, demonstrating good electrode test stability.

[0016] 2. The prepared lactic acid biosensor was characterized by electrochemical analysis and showed good batch-to-batch stability. 3. The wearable lactic acid biosensor can still maintain its testing performance after 1000 mechanical bends, demonstrating good mechanical stability. 4. In this invention, a layer of NiHCF is electrodeposited on the outer layer of Prussian blue. The nesting of Prussian blue and NiHCF prevents the collapse of the Prussian blue structure. The synergistic catalytic effect of PB-NiHCF significantly improves its stability under physiological pH conditions, while it can withstand pH corrosion and maintain consistent electrochemical catalytic activity. 5. Electrodeposition allows PB-NiHCF to be uniformly applied to the working electrode surface, improving the repeatability and stability of the sensor. The thickness of the electrodeposited Prussian blue layer has a certain impact on the sensor's sensitivity and detection range. A thinner Prussian blue layer can provide better sensitivity, while a thicker Prussian blue layer can provide a wider linear response range.

[0017] 6. The limiting diffusion membrane of the present invention can broaden the linear detection range and realize the detection of high concentrations of lactic acid in sweat.

[0018] 7. Prussian blue has a relatively low production cost and a relatively simple preparation process, which is conducive to large-scale production and application.

[0019] The lactic acid sensor preparation method of the present invention is simple to operate and low in cost. Through the synergistic catalytic effect of PB-NiHCF and mechanical performance testing, it solves a series of problems such as poor stability and narrow detection range of traditional sensors. Attached Figure Description

[0020] Figure 1 This is the cyclic voltammetry diagram of Prussian blue electrodeposition in this invention; Figure 2 This is the cyclic voltammetry diagram of the electrodeposited nickel-based Prussian blue of this invention; Figure 3 The chronoamperometry response of the lactic acid sensor of the present invention in the corresponding analyte solution in phosphate buffer saline is shown in the figure. Figure 4 This is the calibration curve corresponding to the timing current response of the lactic acid sensor of the present invention; Figure 5 This is an example diagram illustrating the batch-to-batch stability performance of the lactic acid sensor of the present invention; Figure 6 An example diagram illustrating the mechanical stability performance of the lactic acid sensor of the present invention; Figure 7 The images show the response of the lactic acid sensor of the present invention under different pH conditions with the same lactic acid concentration; where a is the response of the PB-based sensor and b is the response of the PB-NiHCF-based sensor. Figure 8 The diagram shows the long-term stability of the lactic acid sensor of the present invention; where a is the long-term stability diagram of the PB-based sensor and b is the long-term stability diagram of the PB-NiHCF-based sensor. Detailed Implementation

[0021] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

[0022] The fabrication of a highly stable wearable lactate biosensor based on a Prussian blue analogue comprises the following steps: Example 1: Preparation and Characterization of PB-NiHCF 1. Preparation process of PB-NiHCF S1. Flexible electrode fabrication: S1.1 Preparation of the stencil required for screen printing S1.2 Using conductive silver paste as printing ink, a screen is applied to the surface of a PET substrate to print a reference electrode coating with a thickness of 40 μm; using conductive carbon paste as printing ink, a screen is applied to the surface of the PET substrate to print working electrode and counter electrode coatings with a thickness of 40 μm, thus completing the fabrication of the screen-printed electrode; wherein the working electrode area is 5.3844 mm². 2 The counter electrode area is 7.53816 mm². 2 The reference electrode area is 7.53816 mm². 2 ; S2. Activation of working electrode: The flexible electrode was cleaned by performing 30 cycles of cyclic voltammetry (CV) at a scan rate of 500 mV / s within a potential window of -1.2 to 1 V in 10 mL of aqueous solution containing 0.27 mL of concentrated H2SO4. S3. Working electrode interface modification: S3.1 A layer of gold nanoparticles (AuNPs) was deposited by performing 3000 pulse voltammetry cycles in 10 mL of an aqueous solution containing 197 mg HAuCl4·3H2O at a potential window of -0.9 to 0.9 V. S3.2 Electrodeposition of PB layer: In 80 mL of aqueous solution containing 32.5 mg FeCl3, 65.85 mg K3[Fe(CN)6], 292 mg HCl and 59.6 mg KCl, two CV scans were performed at a potential window of -0.2 to 0.6 V to deposit a PB layer on the gold nanoparticle (AuNPs) layer. S3.3 Electrodeposition of NiHCF layer: In 80 mL of aqueous solution containing 9.5 mg NiCl2·6H2O, 13.2 mg K3[Fe(CN)6], 292 mg HCl and 59.6 mg KCl, CV was performed 50 times at a scan rate of 100 mV / s within a potential window of 0~0.8 V to deposit a NiHCF layer on the PB layer.

[0023] 2. Structural Characterization Figure 1 The linear cyclic voltammogram of electrodeposited Prussian blue shows a pair of redox peaks, corresponding to the redox peaks of PB. Figure 2 Linear cyclic voltammetry plots of electrodeposited Prussian blue and its analogues showed complete peak separation between ferric hexacyanoferrate and nickel hexacyanoferrate, allowing control over the structural composition of the resulting mixed film.

[0024] Example 2: Functionalization of PB-NiHCF-based lactic acid sensor S4. Functionalization of the working electrode: Functionalization was carried out on the modified working electrode of Example 1: First, chitosan-multi-walled carbon nanotube dispersion was drop-coated and dried; then lactate oxidase solution was drop-coated and stabilized for 12 h; finally, confined diffusion membrane solution was drop-coated and dried to obtain a highly stable wearable lactate biosensor based on Prussian blue analogue. The preparation method of S4.1 chitosan-multi-walled carbon nanotube dispersion is as follows: 10 mg of chitosan and 20 mg of acetic acid were stirred and dissolved in 1 mL of water to prepare a 1% (w / w) chitosan solution. Then, the prepared chitosan solution was mixed with 2 mg of multi-walled carbon nanotubes and stirred until uniformly dispersed to prepare a chitosan-multi-walled carbon nanotube dispersion.

[0025] The preparation method of S4.2 lactate oxidase solution is as follows: First, prepare 1 mL of 0.02 M phosphate buffer solution (PBS) with pH=7.4. Then, mix 10 mg of bovine serum albumin and 20 mg of lactate oxidase in 1 mL of phosphate buffer solution (pH=7.4).

[0026] The preparation method of the confined diffusion membrane solution in S4.3 is as follows: To prepare a diffusion-limiting membrane solution, weigh out 33 mg of polyvinyl chloride (PVC) and 33 mg of dioctyl sebacate (DOS) and dissolve them in 1 mL of tetrahydrofuran (THF) solution.

[0027] S5. Electrochemical performance testing of lactic acid sensor The prepared lactic acid sensor was evaluated for electrochemical performance using a chronoamperometry method at a potential of 0 V.

[0028] The obtained lactic acid sensor from Figure 3 and Figure 4 It can be seen that the sensor has a good linear relationship (correlation coefficient of 0.99) in the concentration range of 5~30 mM, and can be used as a standard curve for evaluating real-time changes in lactic acid. Figure 5 It can be seen that the three electrodes of different batches of lactic acid sensor have good batch-to-batch stability (relative error less than 5%) within the corresponding concentration range. Figure 6 It can be seen that when the sensor is bent at a certain angle, the current change is very small every 200 bends, indicating good mechanical stability.

[0029] Example 3: Electrochemical Performance Evaluation of Lactic Acid Sensor Electrodeposition of PB layer: In 80 mL of aqueous solution containing 32.5 mg FeCl3, 65.85 mg K3[Fe(CN)6], 292 mg HCl and 59.6 mg KCl, CV was performed 4 times at a scan rate of 50 mV / s within a potential window of -0.2 to 0.6 V. Other steps were the same as in Examples 1 and 2.

[0030] Example 4 Electrodeposition of PB layer: CV was performed 8 times in 80 mL of an aqueous solution containing 32.5 mg FeCl3, 65.85 mg K3[Fe(CN)6], 292 mg HCl and 59.6 mg KCl at a scan rate of 50 mV / s within a potential window of -0.2 to 0.6 V. Other steps were the same as in Examples 1 and 2.

[0031] Example 5 Electrodeposition of PB layer: In 80 mL of aqueous solution containing 32.5 mg FeCl3, 65.85 mg K3[Fe(CN)6], 292 mg HCl and 59.6 mg KCl, CV was performed 12 times at a scan rate of 50 mV / s within a potential window of -0.2 to 0.6 V. Other steps were the same as in Examples 1 and 2.

[0032] Example 6 Electrodeposition of PB layer: CV was performed 16 times in an 80 mL aqueous solution containing 32.5 mg FeCl3, 65.85 mg K3[Fe(CN)6], 292 mg HCl and 59.6 mg KCl at a scan rate of 50 mV / s within a potential window of -0.2 to 0.6 V. Other steps were the same as in Examples 1 and 2.

[0033] Example 7 Electrodeposition of the PB layer: In 80 mL of aqueous solution containing 32.5 mg FeCl3, 65.85 mg K3[Fe(CN)6], 292 mg HCl, and 59.6 mg KCl, 20 CV cycles were performed at a scan rate of 50 mV / s within a potential window of -0.2 to 0.6 V. Other procedures were the same as in Examples 1 and 2. The electrochemical performance evaluation results of the lactic acid sensors in Examples 1, 3, 4, 5, 6, 7, and 8 showed that the lactic acid sensor exhibited the best electrochemical performance when 8 CV cycles were performed at a scan rate of 50 mV / s within a potential window of -0.2 to 0.6 V.

[0034] Example 8 10 mg of bovine serum albumin and 10 mg of lactate oxidase were mixed in 1 mL of phosphate buffer solution (pH=7.4). The rest of the procedure was the same as in Examples 1 and 2.

[0035] Example 9 10 mg of bovine serum albumin and 40 mg of lactate oxidase were mixed in 1 mL of phosphate buffer solution (pH=7.4). Other steps were the same as in Examples 1 and 2. The electrochemical performance evaluation results of the lactate sensors in Examples 2, 8, and 9 showed that the lactate sensor exhibited the best electrochemical performance when the amount of lactate oxidase was 20 mg.

[0036] Example 10 33 mg of polyvinyl chloride (PVC) and 66 mg of dioctyl sebacate (DOS) were weighed and dissolved in 1 mL of tetrahydrofuran (THF) solution to prepare a diffusion-limiting membrane solution. Other steps were the same as in Examples 1 and 2.

[0037] Example 11 33 mg of polyvinyl chloride (PVC) and 132 mg of dioctyl sebacate (DOS) were weighed and dissolved in 1 mL of tetrahydrofuran (THF) solution to prepare a diffusion-limiting membrane solution. Other steps were the same as in Examples 1 and 2.

[0038] Example 12 A diffusion-limiting membrane solution was prepared by dissolving 33 mg of polyvinyl chloride (PVC) and 198 mg of dioctyl sebacate (DOS) in 1 mL of tetrahydrofuran (THF) solution. Other steps were the same as in Examples 1 and 2. The electrochemical performance evaluation results of the lactic acid sensors in Examples 2, 10, 11, and 12 showed that the lactic acid sensor exhibited the best electrochemical performance when the mass of PVC was 33 mg and the mass of DOS was 132 mg.

[0039] Comparative Example 1: PB-based lactic acid sensor A PB-based lactic acid sensor was prepared as a comparative example using steps S1, S2, S3.1, and S3.2 of Example 1 and step S4 of the lactic acid sensor functionalization process in Example 2. Figure 8 It can be seen that the stability of the PB-based sensor decreases after 12,000 seconds, while the stability of the PB-NiHCF-based sensor can be maintained for about 10 hours (current decay rate is less than 80%).

[0040] Comparative Example 2: Unrestricted Diffusion Membrane Lactic Acid Sensor A lactic acid sensor with an unrestricted diffusion membrane was prepared using the preparation processes S1-S3 in Example 1 and the lactic acid sensor functionalization processes S4.1 and S4.2 in Example 2 as a comparative example. The detection range of the lactic acid sensor with the unrestricted diffusion membrane was found to be 50 μM to 5 mM, while the detection range of the lactic acid sensor with a restricted diffusion membrane was 50 μM to 30 mM. Since the lactic acid concentration in sweat is as high as 25 mM, the lactic acid sensor with a restricted diffusion membrane was chosen to detect high concentrations of lactic acid in sweat.

[0041] As mentioned above, lactate levels can be measured to diagnose physiological conditions. While laboratory-measured lactate concentrations may be sufficient to detect certain physiological conditions, in other cases, lactate levels fluctuate too much to yield accurate results. Wearable lactate biosensors based on Prussian blue analogues can conveniently and stably measure changes in lactate concentration, enabling long-term, real-time monitoring of lactate levels in patients.

Claims

1. A method for preparing a highly stable wearable lactic acid biosensor based on a Prussian blue analogue, characterized in that, Includes the following steps: (1) A three-electrode sensor was constructed on a polyethylene terephthalate substrate using screen printing technology to obtain a flexible electrode; (2) Use H2SO4 solution to perform cyclic voltammetry in a potential window of -1.2~1 V to clean the flexible electrode; (3) In HAuCl4 aqueous solution, 100 to 3000 pulse voltammetry cycles were performed within a potential window of -0.9 to 0.9 V to deposit a layer of gold nanoparticles; (4) Cyclic voltammetry was performed in an aqueous solution containing FeCl3, K3[Fe(CN)6], HCl and KCl within a potential window of -0.2 to 0.6 V to deposit a Prussian blue layer on the gold nanoparticle layer; (5) Cyclic voltammetry was performed in an aqueous solution containing NiCl2, K3[Fe(CN)6], HCl and KCl within a potential window of 0~0.8 V to deposit a NiHCF layer on the Prussian blue layer, thereby obtaining the modified working electrode; (6) Functionalization is carried out on the working electrode modified in step (5): First, chitosan-multi-walled carbon nanotube dispersion is dropped and dried; then lactate oxidase solution is dropped and stabilized for 12-24 h; finally, confined diffusion membrane solution is dropped and dried to obtain a highly stable wearable lactate biosensor based on Prussian blue analogue.

2. The method for preparing a highly stable wearable lactic acid biosensor based on a Prussian blue analogue according to claim 1, characterized in that, The three-electrode sensor in step (1) includes a working electrode, a counter electrode, and a reference electrode; wherein the area of ​​the counter electrode is 1.4 times that of the working electrode, and the area of ​​the reference electrode is the same as that of the working electrode.

3. The method for preparing a highly stable wearable lactic acid biosensor based on a Prussian blue analogue according to claim 1, characterized in that, The H2SO4 solution in step (2) is 0.5 M; the cyclic voltammetry scan rate is 500 mV / s, and the number of scans is 1 to 30.

4. The method for preparing a highly stable wearable lactic acid biosensor based on a Prussian blue analogue according to claim 1, characterized in that, In step (3), the concentration of HAuCl4 in the aqueous solution is 2~50 mM.

5. The method for preparing a highly stable wearable lactic acid biosensor based on a Prussian blue analogue according to claim 1, characterized in that, In step (4), the concentration of FeCl3 in the aqueous solution is 2.5~3 mM, the concentration of K3[Fe(CN)6] is 2.5~3 mM, the concentration of HCl is 0.01~0.1 M, and the concentration of KCl is 0.01~0.1 M; the cyclic voltammetry scan rate is 50~100 mV / s, and the number of cycles is 2~20.

6. The method for preparing a highly stable wearable lactic acid biosensor based on a Prussian blue analogue according to claim 1, characterized in that, In step (5), the concentration of NiCl2 in the aqueous solution is 0.5~1 mM, the concentration of K3[Fe(CN)6] is 0.5~1 mM, the concentration of HCl is 0.01~0.1 M, and the concentration of KCl is 0.01~0.1 M; the cyclic voltammetry scan rate is 50~100 mV / s, and the number of cycles is 1~50.

7. The method for preparing a highly stable wearable lactic acid biosensor based on a Prussian blue analogue according to claim 1, characterized in that, The preparation method of chitosan-multi-walled carbon nanotube dispersion is as follows: (1) Dissolve chitosan in acetic acid and stir until dissolved to prepare a 1% chitosan solution; (2) Mix the chitosan solution with multi-walled carbon nanotubes until uniformly dispersed to prepare a chitosan-multi-walled carbon nanotube dispersion; the amount of multi-walled carbon nanotubes in the chitosan-multi-walled carbon nanotube dispersion is 0.5~4 mg / mL.

8. The method for preparing a highly stable wearable lactic acid biosensor based on a Prussian blue analogue according to claim 1, characterized in that, The preparation method of lactate oxidase solution is as follows: (1) Prepare a 0.02 M phosphate buffer solution with pH=7.4; (2) Mix bovine serum albumin and lactate oxidase in a phosphate buffer solution; The content of bovine serum albumin in lactate oxidase solution is 5-15 mg / mL; the content of lactate oxidase in lactate oxidase solution is 10-40 mg / mL.

9. The method for preparing a highly stable wearable lactic acid biosensor based on a Prussian blue analogue according to claim 1, characterized in that, The method for preparing the confined diffusion membrane solution is as follows: Polyvinyl chloride and dioctyl sebacate were weighed and dissolved in a solution of tetrahydrofuran to prepare a diffusion-limiting membrane solution. The mass ratio of polyvinyl chloride to dioctyl sebacate in the diffusion membrane solution is 1:1~6; The concentration of polyvinyl chloride in the confined diffusion membrane solution is 1~33 mg / mL.

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