An interstitial fluid glucose detection device based on porous microneedle array

Abstract

This application relates to the field of medical devices and specifically discloses an interstitial fluid glucose detection device based on a porous microneedle array. The device comprises a microneedle module, a colorimetric detection module, an electrochemical detection module, and a fluid-conducting layer. The microneedle module comprises a porous microneedle array having a porosity gradient, with the porosity gradually increasing from the needle tip to the microneedle base. The porous microneedle array pierces the human epidermis and draws interstitial fluid, which is then transferred to the colorimetric detection module and the electrochemical detection module via the fluid-conducting layer. In the colorimetric detection module, glucose reacts and develops color on the colorimetric film, enabling rapid glucose detection. In the electrochemical detection module, glucose undergoes an oxidation-reduction reaction on the working electrode to generate a current signal, enabling accurate glucose detection. This application has a simple structure and is easy to operate, achieving minimally invasive and painless skin puncture, and can both rapidly and accurately detect interstitial fluid glucose concentration.

Description

Technical Field

[0001] The present application relates to the field of medical devices, and in particular to an interstitial fluid glucose detection device based on a porous microneedle array. Background Art

[0002] As the number of people with diabetes and those in the early stages of the disease continues to grow, accurate blood sugar testing is crucial for self-management and timely treatment. While traditional fingertip blood tests offer good accuracy, they are cumbersome and painful. Therefore, developing a blood sugar testing technology that is accurate, simple, convenient, minimally invasive, and pain-free is crucial.

[0003] Interstitial fluid is an extracellular fluid that is located between cells and intravascular fluid, filling the intercellular spaces of tissues. It is one of the important fluid environments for maintaining normal cell function. Interstitial fluid contains biomarkers such as glucose, and exchanges substances with plasma through tiny pores in the capillary walls, making the concentrations of these markers in the interstitial fluid strongly correlated with their concentrations in the blood, thus having potential value for bioinformatics analysis. Therefore, indirectly detecting blood sugar concentration by detecting the concentration of glucose in the interstitial fluid has become a feasible solution.

[0004] With the rapid development of micro-nano processing technology, porous microneedle arrays, as a new type of minimally invasive transdermal device, have shown unique advantages in the field of biosensing, especially in the extraction of skin interstitial fluid, and have potential important application value. Summary of the Invention

[0005] In order to improve the problems of cumbersome and painful operation of current conventional blood glucose testing, the present application provides an interstitial fluid glucose detection device based on a porous microneedle array.

[0006] The present application provides an interstitial fluid glucose detection device based on a porous microneedle array, which adopts the following technical solutions:

[0007] An interstitial fluid glucose detection device based on a porous microneedle array, comprising:

[0008] A microneedle module includes a porous microneedle array for piercing the human epidermis and extracting interstitial fluid. The porous microneedle array includes a microneedle base and a plurality of porous microneedles arrayed on the microneedle base. The porous microneedles have a porosity gradient, with the porosity gradually increasing from the needle tip to the microneedle base.

[0009] A colorimetric detection module, comprising a colorimetric film for reacting with glucose in the interstitial fluid to develop color, wherein the depth of the developed color is related to the glucose concentration;

[0010] An electrochemical detection module comprising a flexible substrate and a three-electrode system disposed on the flexible substrate, wherein the three-electrode system comprises a counter electrode, a reference electrode, and a working electrode. Glucose in the interstitial fluid undergoes an oxidation-reduction reaction on the working electrode and generates a current signal related to the glucose concentration.

[0011] The liquid conducting layer is attached to the microneedle substrate and is used to transfer the interstitial fluid drawn by the porous microneedle array to the colorimetric detection module and the electrochemical detection module at the same time.

[0012] The porous microneedles in the porous microneedle array exhibit a porosity gradient, increasing from the tip to the base. The lower porosity of the needle tip provides greater strength, resulting in stronger puncture and less painful punctures. The higher porosity of the needle body provides excellent water absorption, enabling rapid extraction of interstitial fluid and providing sufficient target for colorimetric and electrochemical detection.

[0013] The porous microneedle array draws interstitial fluid, which is then transferred via the fluid-conducting layer to the colorimetric and electrochemical detection modules. In the colorimetric detection module, the colorimetric film reacts with glucose in the interstitial fluid to produce a color whose depth correlates with the glucose concentration, enabling rapid detection of glucose concentration. In the electrochemical detection module, glucose in the interstitial fluid undergoes an oxidation-reduction reaction at the working electrode, generating a current signal correlated with the glucose concentration, enabling accurate detection of glucose concentration.

[0014] The detection device provided in this application can perform both rapid and accurate detection of interstitial fluid glucose concentration. The colorimetric detection module and the electrochemical detection module can be used simultaneously or separately, and are suitable for different application scenarios. The colorimetric detection module is used in scenarios requiring rapid detection, and the electrochemical detection module is used in scenarios requiring accurate detection. This provides a solution for diabetic patients and risk groups to conveniently and accurately assess blood sugar levels.

[0015] Furthermore, the porous microneedle is in the shape of a quadrangular pyramid.

[0016] Compared with the conical type, the quadrangular pyramid needle tip is smaller and easier to pierce the skin. At the same time, the tip-guiding characteristics brought by its shape structure help guide the skin interstitial fluid to the microneedle base.

[0017] Furthermore, the porous microneedles have a micrometer-scale spatial network structure.

[0018] The porous structure obtained by the traditional porogen method usually has uneven pore distribution, which will form unstable points locally and easily collapse when subjected to stress; the pores of the porous microneedles provided in the present application are spatially network-connected, with good mechanical stability and good water absorption performance.

[0019] Furthermore, the method for preparing the porous microneedle array having a porosity gradient comprises the following steps:

[0020] Positive mold preparation: Prepare the positive mold of the microneedle array by 3D printing;

[0021] Preparation of negative mold: Cover the negative mold material on the surface of the microneedle array positive mold, and then demould to obtain the microneedle array negative mold;

[0022] Solvent evaporation: A hexafluoroisopropanol solution of polyglycolide is injected into the negative mold of the microneedle array. After the hexafluoroisopropanol evaporates in a directionally controlled manner, a porous microneedle array with a porosity gradient is obtained.

[0023] Furthermore, in the solvent volatilization step, the solvent at the needle body evaporates first, and the solvent at the needle tip evaporates later.

[0024] During the rapid evaporation of the hexafluoroisopropanol solvent, the polyglycolide-hexafluoroisopropanol solution gradually becomes saturated, with localized high-saturation regions appearing particularly at the solid-liquid-gas boundary. A small amount of polyglycolide then precipitates and forms crystal nuclei. Subsequently, the polyglycolide components in the solution precipitate and grow around the crystal nuclei. Influenced by the semi-crystalline nature of polyglycolide, the growth is undirectional and ultimately exhibits a high-porosity spatial network structure. The higher the polyglycolide concentration, the higher the supersaturation of the solution, resulting in an increase in the number of crystal nuclei in the solution and an increase in the rate of polyglycolide precipitation. However, the volume of the individual crystallization regions decreases, and the resulting spatial network structure has a low porosity.

[0025] During the solvent evaporation step in preparing the porous microneedle array, the solvent near the microneedle base evaporates first, and the solvent near the microneedle tip evaporates later, i.e., the solvent evaporates in a directional manner. The closer to the microneedle tip, the slower the solvent evaporates, and the higher the concentration of the residual polyglycolide-hexafluoroisopropanol solution, resulting in a lower porosity for the precipitated polyglycolide. In this way, by controlling the direction of solvent evaporation, a porous microneedle array with a porosity gradient can be prepared.

[0026] Furthermore, the colorimetric film is a TMB-functionalized porous film immobilized with glucose oxidase and horseradish peroxidase, and the colorimetric film is attached to the liquid-conducting layer.

[0027] During detection, interstitial fluid diffuses in the colorimetric film, and glucose oxidase oxidizes the glucose in the interstitial fluid to produce hydrogen peroxide, which further reacts with TMB under the action of horseradish peroxidase to produce a colored product. The higher the glucose concentration, the more colored products are produced and the darker the color. The glucose concentration can be detected based on the depth of the color.

[0028] Furthermore, the method for preparing the colorimetric film comprises the following steps:

[0029] TMB is dissolved in a hexafluoroisopropanol solution of polyglycolide and spread on a substrate, and the hexafluoroisopropanol is allowed to evaporate to obtain a TMB-functionalized porous film.

[0030] Glucose oxidase and horseradish peroxidase solutions were added dropwise to the TMB-functionalized porous film to obtain a colorimetric film.

[0031] During the evaporation of the solvent, polyglycolide and TMB precipitate simultaneously, allowing TMB to be evenly distributed and fixed in the spatial network structure of polyglycolide, significantly reducing the "coffee ring effect", which is beneficial to improving the color uniformity and stability of the colorimetric film.

[0032] Furthermore, the three-electrode system is coated with a hydrogel layer, and the hydrogel layer is adhered to the liquid-conducting layer.

[0033] Furthermore, the working electrode includes a conductive circuit in a cross-comb structure and a porous conductive carrier covering the conductive circuit, and the porous conductive carrier is loaded with glucose oxidase.

[0034] Furthermore, the porous conductive carrier is polyglycolide porous particles adsorbed with carbon nanotubes.

[0035] Glucose in the interstitial fluid reacts with glucose oxidase in the working electrode to produce hydrogen peroxide. When a certain external potential is applied, the hydrogen peroxide oxidizes and decomposes to produce electrons. The higher the glucose concentration, the more hydrogen peroxide is produced, which means more electrons and a greater current is generated. By measuring the current, the glucose concentration in the interstitial fluid can be analyzed.

[0036] The conductive circuit with a cross-comb structure increases the contact area between the test solution and the working electrode. The porous conductive carrier has a conductive three-dimensional structure with a high specific surface area and good biocompatibility. It can increase the contact area of ​​the reaction while tightly fixing glucose oxidase and maintaining enzyme activity, thereby obtaining a larger detection current at the same test substance concentration, improving signal resolution and detection accuracy, and realizing high-sensitivity detection of glucose in interstitial fluid.

[0037] In summary, this application includes at least one of the following beneficial technical effects:

[0038] 1. The porous microneedles in the porous microneedle array provided herein have a micrometer-scale spatial network structure and a porosity gradient, with the porosity gradually increasing from the needle tip to the microneedle base. The needle tip with a smaller porosity has greater strength, thus having a stronger puncture ability. The needle body with a larger porosity has good water absorption capacity, enabling rapid absorption of interstitial fluid, providing sufficient target for colorimetric and electrochemical detection, and thus improving detection efficiency.

[0039] 2. The colorimetric detection module provided in this application utilizes the principle of color response change to determine the concentration of a specific substance by analyzing the degree of color change caused by the substance. It is highly selective and sensitive, capable of rapidly responding to changes in the concentration of the target substance and accurately measuring it, allowing users to quickly obtain test results.

[0040] 3. The electrochemical detection module circuit provided in this application is manufactured using inkjet printing technology, which is simple to manufacture and easy to mass-produce. The porous conductive support in the working electrode has a conductive three-dimensional structure with a high specific surface area and good biocompatibility. It can tightly fix glucose oxidase and maintain enzyme activity while increasing the contact area for the reaction. This allows for a higher detection current at the same analyte concentration, improving signal resolution and detection accuracy, and enabling highly sensitive detection of glucose in interstitial fluid.

[0041] 4. The interstitial fluid glucose detection device based on a porous microneedle array provided in this application has a simple structure and is easy to operate. It can puncture the skin minimally invasively and painlessly and realize in situ real-time detection. It can perform both rapid and accurate detection of interstitial fluid glucose concentration. The colorimetric detection module and the electrochemical detection module can be used simultaneously or separately, providing a solution for diabetic patients and risk groups to conveniently and accurately assess blood sugar levels. It can be applied to actual scenarios such as self-testing of blood sugar concentration by diabetic patients and rapid blood sugar testing. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 2 is a side view of an interstitial fluid glucose detection device based on a porous microneedle array in an embodiment of the present application;

[0043] Figure 2 1 is a top view of an interstitial fluid glucose detection device based on a porous microneedle array in an embodiment of the present application;

[0044] Figure 3 1 is a partial view of a porous microneedle with a porosity gradient in an embodiment of the present application, wherein (a) is the needle tip; (b) is the middle of the needle body; and (c) is the portion of the needle body close to the microneedle base.

[0045] Figure 4 This is a graph showing the performance results of colorimetric detection of simulated interstitial fluid at 0-10 mM glucose in an embodiment of the present application;

[0046] Figure 5 This is a graph showing the performance results of the simulated interstitial fluid in the electrochemical detection of 0-10 mM glucose in the examples of this application.

[0047] Figure numerals: 1. microneedle module; 11. porous microneedle array; 12. porous microneedle; 2. colorimetric detection module; 21. liquid-conducting layer; 22. colorimetric film; 3. electrochemical detection module; 31. lower substrate; 32. upper substrate; 33. nanosilver conductive circuit; 331. reference electrode; 332. working electrode; 333. counter electrode; 34. porous conductive carrier with immobilized enzyme; 35. hydrogel; 4. epidermis; 5. dermis. DETAILED DESCRIPTION

[0048] The English abbreviations in this article are as follows:

[0049] PGA (Polyglycolide acid): polyglycolide;

[0050] TMB (Tetramethylbenzidine): 3.3'5.5'-tetramethylbenzidine;

[0051] PDMS (Polydimethylsiloxane): dimethylsiloxane;

[0052] HFIP (Hexafluoroisopropanol): Hexafluoroisopropanol;

[0053] PI (Polyimide): polyimide.

[0054] The following is combined with Figure 1-5 This application is described in further detail.

[0055] The present application discloses an interstitial fluid glucose detection device based on a porous microneedle array. Figure 1 The interstitial fluid glucose detection device based on the porous microneedle array includes a microneedle module 1, a colorimetric detection module 2, an electrochemical detection module 3 and a liquid conducting layer 21.

[0056] Reference Figure 1 and Figure 2 The microneedle module 1 includes a porous microneedle array 11 for piercing the human epidermis and drawing interstitial fluid. The porous microneedle array 11 includes a microneedle base and a plurality of porous microneedles 12 arrayed on the microneedle base. The porous microneedles 12 have a porosity gradient, and the porosity gradually increases from the needle tip to the microneedle base.

[0057] The method for preparing the porous microneedle array 11 with a porosity gradient comprises the following steps:

[0058] Step 1. Positive mold preparation: Prepare a positive mold for the microneedle array by 3D printing. The substrate size is 10 mm × 10 mm, and 36 quadrangular pyramidal microneedles are evenly distributed in a 6 × 6 pattern. The spacing between adjacent microneedles is 1 mm. The length and width of the base of a single microneedle are both 480 μm, the height is 900 μm, and the tip angle is 30°.

[0059] Step 2, negative mold preparation: Cover the negative mold material PDMS on the surface of the microneedle array positive mold, and then demould to obtain the microneedle array negative mold;

[0060] Step 3, solvent evaporation: inject a hexafluoroisopropanol solution of polyglycolide (polyglycolide concentration is 50 mg / mL) into the negative mold of the microneedle array, place the negative mold of the microneedle array upright (open end facing up, needle tip facing down), and evaporate the hexafluoroisopropanol in a direction, that is, the solvent in the needle body evaporates first, and the solvent in the needle tip evaporates later. The resulting porous microneedle array 11 has a micron-scale spatial network structure and a porosity gradient. Figure 3 As shown in the figure, the porosity gradually increases from the needle tip to the microneedle base, and the porosity gradient ranges from 7% to 48%.

[0061] The needle tip with smaller porosity has greater strength and thus stronger puncture ability, which helps to reduce the pain of puncture; the needle body with larger porosity has good water absorption capacity to achieve rapid absorption of interstitial fluid and provide sufficient target for colorimetric detection and electrochemical detection.

[0062] Reference Figure 1 and Figure 2 The liquid-conducting layer 21 is a porous polyglycolide membrane bonded to the microneedle substrate. It has an average thickness of 49 μm, pores with a distribution diameter of 1-5 μm, and a porosity of 42%. The liquid-conducting layer 21 is used to transfer interstitial fluid drawn from the porous microneedle array 11 to both the colorimetric detection module 2 and the electrochemical detection module 3.

[0063] Reference Figure 1 and Figure 2 The colorimetric detection module 2 includes a colorimetric film 22 for reacting with glucose in the interstitial fluid to develop color. The colorimetric film 22 is a TMB-functionalized porous film immobilized with glucose oxidase and horseradish peroxidase. The colorimetric film 22 is attached to the liquid-conducting layer 21 .

[0064] The preparation method of the colorimetric film comprises the following steps:

[0065] Step 1: Dissolve 10 mg of TMB in 2 mL of a 50 mg / mL polyglycolide-hexafluoroisopropanol (PGA-HFIP) solution. Mix thoroughly and spread on a substrate. Allow the PGA-HFIP to evaporate to obtain a TMB-functionalized porous film with a porosity of 43%.

[0066] During the evaporation of the solvent, polyglycolide and TMB precipitate simultaneously, allowing TMB to be evenly distributed and fixed in the spatial network structure of polyglycolide, significantly reducing the "coffee ring effect", which is beneficial to improving the color uniformity and stability of the colorimetric film.

[0067] Step 2: Add 2 μL of glucose oxidase and horseradish peroxidase solution (the concentration of both enzymes is 100 U / mL) dropwise to the TMB-functionalized porous film, so that the glucose oxidase and horseradish peroxidase are adsorbed in the porous structure of the TMB-functionalized porous film to obtain a colorimetric film.

[0068] Reference Figure 1 and Figure 2 The electrochemical detection module 3 includes a flexible substrate and a three-electrode system disposed on the flexible substrate. The three-electrode system includes a counter electrode 333, a reference electrode 331, and a working electrode 332. The three-electrode system is encapsulated by a hydrogel 35, which is attached to the liquid-conducting layer 21.

[0069] Reference Figure 1 and Figure 2 The flexible substrate comprises a lower substrate 31 and an upper substrate 32. The lower substrate 31 is a 50μm thick polyimide (PI) film measuring 15mm x 5mm, while the upper substrate 32 is a 70μm thick polydimethylsiloxane (PDMS) film measuring 15mm x 5mm. After oxygen plasma treatment, the upper substrate 32 is inkjet-printed with 100μm-wide nanosilver conductive lines 33. The flexible substrate printed with the nanosilver conductive lines 33 is sintered and cured at 150°C. The reference electrode 331, counter electrode 333, and working electrode 332 are then prepared as follows:

[0070] The reference electrode 331 and the counter electrode 333 are Ag / AgCl electrodes obtained by chlorination of the nanosilver conductive circuit 33 .

[0071] Reference Figure 1 and Figure 2 The working electrode 332 comprises a conductive circuit in a cross-comb structure with a tooth spacing of 150 μm and an average resistivity of 2.7 Ω / mm. The cross-comb structure is covered with a porous conductive support 34 on which the enzyme is immobilized. The porous conductive support is composed of porous particles of polyglycolide adsorbed with carbon nanotubes, on which glucose oxidase is loaded.

[0072] The preparation method of polyglycolide porous particles is as follows: an equal amount of water is slowly added to a 50 mg / mL PGA-HFIP solution and slowly stirred to produce polyglycolide flocs; the polyglycolide flocs are then broken up by high-speed stirring to obtain polyglycolide porous particles. By controlling the high-speed stirring time, polyglycolide porous particles of different particle sizes can be obtained. In this example, the high-speed stirring time is 48 hours, and the resulting polyglycolide porous particles have a particle size of 10-20 μm.

[0073] After mixing carbon nanotubes with porous polyglycolide particles, glucose oxidase is added to form a porous conductive carrier 34 immobilized with the enzyme. This carrier is then applied to the cross-comb-shaped conductive traces in the working electrode 332 region, completing the preparation of the working electrode 332. Finally, the three-electrode system is encapsulated with hydrogel 35, completing the preparation of the electrochemical detection module 3.

[0074] In the steps of preparing the porous microneedle array, preparing the colorimetric film, and preparing the polyglycolide porous particles, the preparation method of the polyglycolide hexafluoroisopropanol solution (PGA-HFIP solution) is as follows:

[0075] Polyglycolide particles were wrapped in aluminum foil and placed on the bottom plate of a hot press preheated to 230°C. The polyglycolide particles were heated for 100 seconds to completely melt the polyglycolide particles. The temperature was then maintained and the hot press was operated to apply pressure for 100 seconds. After the hot pressing treatment, the aluminum foil wrapped with polyglycolide was removed from the hot press, cooled at room temperature for 15 seconds, and peeled off from the aluminum foil to obtain a low-crystallinity polyglycolide film. The low-crystallinity polyglycolide film was dissolved in hexafluoroisopropanol to obtain a polyglycolide hexafluoroisopropanol solution (PGA-HFIP solution).

[0076] By hot pressing, polyglycolide particles with a diameter of several millimeters are pressed into a film hundreds of microns thick, which greatly increases the heat exchange area and can be quickly cooled in room temperature air. At the same time, the high thermal conductivity of aluminum foil is utilized to quench and cool the polyglycolide film in the air, blocking the recrystallization process of polyglycolide, thereby reducing the crystallinity of polyglycolide and making it easily soluble in organic solvents such as hexafluoroisopropanol.

[0077] After completing the preparation of the microneedle module 1, the colorimetric detection module 2, and the electrochemical detection module 3, the modules are assembled into an interstitial fluid glucose detection device and attached to human skin. The porous microneedles 12 pierce the epidermis 4 of the skin, and the interstitial fluid migrates to the microneedle base through the pore channels inside the porous microneedle array 11 and is quickly transferred to the two detection modules by the liquid conducting layer 21.

[0078] In the colorimetric detection module 2, interstitial fluid diffuses in the colorimetric film 22, and glucose oxidase oxidizes the glucose in the interstitial fluid to produce hydrogen peroxide, which further reacts with TMB under the action of horseradish peroxidase to produce a colored product. The higher the glucose concentration, the more colored product is produced and the darker the color. The glucose concentration can be detected based on the depth of the color.

[0079] In electrochemical detection module 3, glucose in the interstitial fluid reacts with glucose oxidase in the working electrode to produce hydrogen peroxide. When a certain external potential is applied, the hydrogen peroxide oxidizes and decomposes to produce electrons. The higher the glucose concentration, the more hydrogen peroxide is produced, which in turn generates more electrons and a greater current. By measuring the current, the glucose concentration in the interstitial fluid can be determined.

[0080] The detection results of the colorimetric detection module 2 on the simulated interstitial fluid containing 0-10mM glucose are as follows: Figure 4 The test showed a uniform color distribution without large areas of obvious color difference. The color gradients displayed by different glucose concentrations were obvious. The gray value of the color was calibrated against the glucose concentration, showing good linearity, which can cover the linear detection range of normal fluctuations in human blood sugar. Its sensitivity was 10.07 / mM, R 2 =0.977. The specific values ​​of the detection accuracy are shown in Table 1, which is 96.2%.

[0081] Table 1 Detection accuracy results of colorimetric detection module

[0082]

[0083] The detection effect of electrochemical detection module 3 on simulated interstitial fluid containing 0-10mM glucose is as follows Figure 5 As the glucose concentration increases, the response current increases, and the response current at 10s shows obvious discrimination. The specific values ​​of detection accuracy are shown in Table 2. The average detection accuracy of the electrochemical sensor module is 97.8%.

[0084] Table 2 Detection accuracy results of electrochemical detection module

[0085]

[0086] This application can perform both rapid and accurate detection of interstitial fluid glucose concentration, and is suitable for different application scenarios, providing a convenient and accurate solution for assessing blood sugar levels for diabetic patients and those at risk.

[0087] The above are all preferred embodiments of the present application, and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A device for detecting interstitial fluid glucose based on a porous microneedle array, characterized by: include: A microneedle module includes a porous microneedle array for piercing the human epidermis and extracting interstitial fluid. The porous microneedle array includes a microneedle base and a plurality of porous microneedles arrayed on the microneedle base. The porous microneedles have a porosity gradient, with the porosity gradually increasing from the needle tip to the microneedle base. A colorimetric detection module, comprising a colorimetric film for reacting with glucose in the interstitial fluid to develop color, wherein the depth of the developed color is related to the glucose concentration; An electrochemical detection module comprising a flexible substrate and a three-electrode system disposed on the flexible substrate, wherein the three-electrode system comprises a counter electrode, a reference electrode, and a working electrode. Glucose in the interstitial fluid undergoes an oxidation-reduction reaction on the working electrode and generates a current signal related to the glucose concentration. a liquid conducting layer, attached to the microneedle substrate, for simultaneously transferring the interstitial fluid drawn by the porous microneedle array to the colorimetric detection module and the electrochemical detection module; The method for preparing the porous microneedle array having a porosity gradient comprises the following steps: Positive mold preparation: Prepare the positive mold of the microneedle array by 3D printing; Preparation of negative mold: Cover the negative mold material on the surface of the microneedle array positive mold, and then demould to obtain the microneedle array negative mold; Solvent evaporation: A hexafluoroisopropanol solution of polyglycolide is injected into the negative mold of the microneedle array. After the hexafluoroisopropanol evaporates in a directionally controlled manner, a porous microneedle array with a porosity gradient is obtained. Among them, the solvent in the needle body evaporates first, and the solvent in the needle tip evaporates later.

2. The interstitial fluid glucose detection device based on a porous microneedle array according to claim 1, characterized in that: The porous microneedle is in a quadrangular pyramid shape.

3. The interstitial fluid glucose detection device based on a porous microneedle array according to claim 1, characterized in that: The porous microneedles have a micron-scale spatial network structure.

4. The interstitial fluid glucose detection device based on a porous microneedle array according to claim 1, characterized in that: The colorimetric film is a TMB functionalized porous film fixed with glucose oxidase and horseradish peroxidase, and the colorimetric film is attached to the liquid-conducting layer.

5. The interstitial fluid glucose detection device based on a porous microneedle array according to claim 4, characterized in that: The preparation method of the colorimetric film comprises the following steps: TMB is dissolved in a hexafluoroisopropanol solution of polyglycolide and spread on a substrate, and the hexafluoroisopropanol is allowed to evaporate to obtain a TMB-functionalized porous film. Glucose oxidase and horseradish peroxidase solutions were added dropwise to the TMB-functionalized porous film to obtain a colorimetric film.

6. The interstitial fluid glucose detection device based on a porous microneedle array according to claim 1, characterized in that: The three-electrode system is coated with a hydrogel layer, and the hydrogel layer is adhered to the liquid-conducting layer.

7. The interstitial fluid glucose detection device based on a porous microneedle array according to claim 1, characterized in that: The working electrode includes a conductive circuit in a cross-comb structure and a porous conductive carrier covering the conductive circuit, and the porous conductive carrier is loaded with glucose oxidase.

8. The interstitial fluid glucose detection device based on a porous microneedle array according to claim 7, characterized in that: The porous conductive carrier is polyglycolide porous particles adsorbed with carbon nanotubes.

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