Self-driven wearable microneedle for detecting lactic acid in interstitial fluid and preparation method of self-driven wearable microneedle

Abstract

The invention belongs to the technical field of biosensing, and particularly discloses a self-driven wearable microneedle for detecting lactic acid in interstitial fluid and a preparation method of the self-driven wearable microneedle. The preparation method comprises the following steps: mixing epoxy resin, polyether amine and carbon nanotubes to obtain a mixture; then adding the mixture into a microneedle mold, adding a wire to enable the wire to be electrically connected with the conductive mixture, and curing to obtain a microneedle; carrying out Pt nano particle deposition on the obtained microneedle to obtain a microneedle A; sequentially carrying out metal spraying treatment and lactate oxidase solution incubation to obtain a microneedle B; the microneedle A serves as a counter electrode, the microneedle B serves as a working electrode, and the self-driven wearable microneedle for detecting lactic acid in interstitial fluid is obtained. The microstructure of the microneedle can be utilized to generate a capillary effect, human interstitial fluid can be quickly absorbed, the content of lactic acid in the interstitial fluid is detected, and minimally invasive interstitial fluid extraction is realized for detection; the preparation method has the advantages of simplicity and convenience in operation.

Description

Technical Field

[0001] The present invention relates to the field of biosensing technology, and particularly to a self-driven wearable microneedle for detecting lactic acid in interstitial fluid and a preparation method thereof. Background Art

[0002] In recent years, the point-of-care detection of lactic acid has attracted extensive attention because it plays a crucial role in sports medicine and clinical care. Lactic acid is a key metabolite produced by muscles during the anaerobic metabolism of glucose, and its monitoring is essential for evaluating the performance of athletes during high-intensity and endurance training. In healthy individuals, the blood lactic acid level at rest is usually between 0.5 and 2 mM, while it can rise to 15 mM during exercise and up to 25 mM during extreme exercise. In addition, elevated lactic acid levels are also associated with various pathological conditions, including heart diseases, endotoxin shock, pulmonary embolism, liver diseases, diabetes, etc. The latest research has also found that lactic acid is the main factor for the acidification of the cancer cell microenvironment, which makes it particularly important in cancer diagnosis.

[0003] Interstitial fluid (ISF) is the most common accessible fluid in the human body, accounting for 75% of the extracellular fluid and 15% to 25% of body weight. This biological fluid is mainly derived from the exchange of capillary blood, and its application potential in in-situ biomarker analysis has attracted extensive attention. ISF shares at least 84% of the key biomarkers with plasma, such as glucose and lactic acid, indicating a high correlation between the levels of these biomarkers in ISF and blood. By analyzing ISF in-situ, the metabolic changes within tissues can be monitored in real time, which is crucial for early disease diagnosis and personalized medical intervention. ISF contains biomarkers that reflect the local tissue state, providing important information on the physiological state of cells and tissues. Research has shown that ISF not only contains information similar to that of plasma but also unique biomarkers not detected in plasma. Extracting ISF from under the skin and performing on-site biomarker analysis helps to overcome the interference of skin residues and environmental pollutants, as well as the challenges posed by the naturally low-yield biological fluids (such as sweat) in the skin.

[0004] The development of a highly sensitive and selective monitoring system combined with interstitial fluid (ISF) extraction is crucial for the precise quantification of analytes. As an analytical tool, biosensors can measure analytes in biological or chemical reactions. Due to their characteristics such as rapid response, small sample requirements, superior analytical performance, and high reliability, they have become a powerful complement to traditional methods. Electrochemical biosensors are particularly prominent, providing a versatile and sensitive analytical platform for the detection of analytes. Their advantage lies in the ability to measure with an extremely low sample volume (in the order of tens of microliters), while enabling automated operation and low-cost testing. By combining advanced materials and biorecognition elements, electrochemical biosensors can convert biochemical reactions into quantifiable electrical signals, enabling rapid and label-free detection of target molecules. Summary of the Invention

[0005] In view of this, the present invention provides a self-driven wearable microneedle for lactate detection in interstitial fluid and its preparation method to solve the many drawbacks existing in the current subcutaneous extraction of ISF and on-site biomarker analysis.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A preparation method of a self-driven wearable microneedle for lactate detection in interstitial fluid, comprising the following steps:

[0008] 1) Mix epoxy resin, polyetheramine, and carbon nanotubes to obtain a mixture;

[0009] 2) Add the mixture to a microneedle mold, add a wire to form an electrical connection between the wire and the conductive mixture, and obtain a microneedle after curing;

[0010] 3) Deposit Pt nanoparticles on the microneedle obtained in step 2) to obtain microneedle A;

[0011] Spray gold on the microneedle obtained in step 2) and incubate it with a lactate oxidase solution in sequence to obtain microneedle B;

[0012] 4) Use microneedle A as the counter electrode and microneedle B as the working electrode to obtain a self-driven wearable microneedle for lactate detection in interstitial fluid.

[0013] Preferably, in step 1), the mass ratio of the epoxy resin to the polyetheramine is 3 - 4:1; the total mass ratio of the epoxy resin and the polyetheramine to the carbon nanotubes is 4:0.4 - 0.6.

[0014] Preferably, in step 2), the curing temperature is 60 - 80 °C, and the curing time is 6 - 12 h.

[0015] Preferably, in step 3), the deposition solution for Pt nanoparticle deposition is a mixed aqueous solution of chloroplatinic acid and formic acid;

[0016] The molar concentration of chloroplatinic acid in the deposition solution is 4-6 mmol / L, and the molar concentration of formic acid is 1-2 mmol / L.

[0017] Preferably, the deposition voltage for depositing Pt nanoparticles is -0.5 to 0 V, and the deposition time is 30 to 180 s.

[0018] Preferably, the time for sputtering gold in step 3) is 30 to 120 s.

[0019] Preferably, the incubation time of the lactate oxidase solution is 0.5 to 2 h, and the incubation temperature is 25 to 37 °C;

[0020] The preparation method of the lactate oxidase solution is to mix lactate oxidase with water to obtain a mixed solution, and then mix the mixed solution with an aqueous acetic acid solution of chitosan.

[0021] Preferably, the volume ratio of the mixed solution to the aqueous acetic acid solution of chitosan is 1-1.5:1;

[0022] The mass concentration of lactate oxidase in the mixed solution is 8-12 mg / mL, the mass concentration of chitosan in the aqueous acetic acid solution of chitosan is 0.8-1.2 wt.%, and the molar concentration of acetic acid is 0.1-0.15 mmol / L.

[0023] Another object of the present invention is to provide a self-driven wearable microneedle for detecting lactate in interstitial fluid prepared by the above preparation method.

[0024] According to the above technical solutions, compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. In the present invention, an epoxy resin, a polyetheramine and a carbon nanotube composite material are prepared into microneedles by a template method. By using the micro-structure of the microneedles, a capillary effect is generated, which can quickly absorb human interstitial fluid and detect the lactate content in the interstitial fluid, realizing minimally invasive extraction of interstitial fluid for detection (lactate oxidase oxidizes lactate to carbon dioxide and pyruvate, and platinum nanoparticles reduce oxygen to water, and the generated electrical signal can be detected by open circuit voltage (OCP));

[0026] 2. Compared with the existing solutions, the preparation method of the present invention is simple and easy to operate, which can make lactate oxidase adhere to the microneedles. By constructing a lactate biofuel cell, the need to carry an external power source can be reduced, increasing the portability of the device. The present invention can effectively utilize the capillary effect, can collect sufficient interstitial fluid, and analyze the lactate content in the interstitial fluid through a sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.

[0028] Figure 1 Schematic diagram of the preparation process of the microneedles in Embodiment 1 of the present invention;

[0029] Figure 2 Physical diagram of the microneedles prepared in Embodiment 1 of the present invention, where Figure 2 (a) in is the top view of the microneedles, Figure 2 (b) in is the side view of the microneedles;

[0030] Figure 3 SEM diagram of the microneedles prepared in Embodiment 1 of the present invention, where Figure 3 (a) in is the planar SEM diagram, Figure 3 (b) in is the cross-sectional SEM diagram;

[0031] Figure 4 Mapping diagram of the microneedles A prepared in Embodiment 1 of the present invention and the microneedles B not incubated in the lactate oxidase solution, where Figure 4 (a) in is the mapping diagram of the microneedles B not incubated in the lactate oxidase solution, Figure 4 (b) in is the mapping diagram of the microneedles A;

[0032] Figure 5 Relationship diagram between the open-circuit voltage and the lactate concentration of the self-driven wearable microneedles prepared by the present invention;

[0033] Figure 6 Linear regression equation of lactate and open-circuit voltage of the self-driven wearable microneedles prepared in Embodiment 1 of the present invention. Detailed implementation manners

[0034] The present invention provides a preparation method for self-driven wearable microneedles for lactate detection in interstitial fluid, comprising the following steps:

[0035] 1) Mix epoxy resin, polyetheramine and carbon nanotubes to obtain a mixture;

[0036] 2) Add the mixture to a microneedle mold, add a wire to form an electrical connection between the wire and the conductive mixture, and obtain microneedles after curing;

[0037] 3) Deposit Pt nanoparticles on the microneedles obtained in step 2) to obtain microneedles A;

[0038] The microneedles obtained in step 2) are successively subjected to sputtering with gold and incubation in a lactate oxidase solution to obtain microneedles B.

[0039] 4) Using microneedles A as the counter electrode and microneedles B as the working electrode, a self-powered wearable microneedle for detecting lactate in interstitial fluid is obtained.

[0040] In the present invention, the epoxy resin and polyetheramine are preferably commercially available AB glue. The A component is the epoxy resin, and the B component is the polyetheramine.

[0041] In the present invention, the addition of carbon nanotubes makes the microneedles charged, and compared with externally spraying a conductive medium, this method can form a better conductive path.

[0042] In the present invention, in step 1), the mass ratio of the epoxy resin to the polyetheramine is 3 - 4:1, preferably 3 - 3.8:1, further preferably 3 - 3.5:1, still further preferably 3 - 3.2:1, and most preferably 3:1; the total mass ratio of the epoxy resin and polyetheramine to the mass of the carbon nanotubes is 4:0.4 - 0.6, preferably 4:0.45 - 0.55, and further preferably 4:0.5.

[0043] In the present invention, in step 2), the curing temperature is 60 - 80°C, specifically it can be 62°C, 65°C, 68°C, 70°C, 72°C, 75°C, 78°C; the curing time is 6 - 12 h, specifically it can be 7 h, 8 h, 9 h, 10 h, 11 h.

[0044] In the present invention, in step 3), the deposition solution for depositing Pt nanoparticles is an aqueous mixed solution of chloroplatinic acid and formic acid.

[0045] In the present invention, the purpose of depositing Pt nanoparticles is to reduce oxygen to water to form the cathode of a fuel cell. This deposition method can autonomously control the thickness of the platinum layer deposition and is more firmly adhered compared to the drop-casting method.

[0046] In the present invention, the molar concentration of chloroplatinic acid in the deposition solution is 4 - 6 mmol / L, specifically it can be 4.2 mmol / L, 4.5 mmol / L, 4.8 mmol / L, 5 mmol / L, 5.2 mmol / L, 5.5 mmol / L, 5.8 mmol / L; the molar concentration of formic acid is 1 - 2 mmol / L, specifically it can be 1.2 mmol / L, 1.4 mmol / L, 1.5 mmol / L, 1.6 mmol / L, 1.8 mmol / L.

[0047] In the present invention, the deposition voltage for depositing the Pt nanoparticles is -0.5 to 0 V, and the deposition voltage is not 0. Specifically, it can be -0.5 V, -0.4 V, -0.3 V, -0.2 V, -0.1 V; the deposition time is 30 to 180 s, and specifically, it can be 35 s, 40 s, 45 s, 50 s, 55 s, 60 s, 65 s, 70 s, 75 s, 80 s, 85 s, 90 s, 100 s, 120 s, 150 s, 160 s.

[0048] In the present invention, the time for the gold spraying treatment in step 3) is 30 to 120 s, and specifically, it can be 40 s, 50 s, 60 s, 70 s, 80 s, 90 s, 100 s, 110 s.

[0049] In the present invention, the gold spraying treatment can increase the conductivity of the microneedles and can also form gold-sulfur bonds with lactate oxidase, enabling lactate oxidase to be better loaded on the microneedles through chemical bonding.

[0050] In the present invention, the incubation time of the lactate oxidase solution is 0.5 to 2 h, and specifically, it can be 0.6 h, 0.8 h, 1 h, 1.2 h, 1.5 h, 1.8 h. The incubation temperature is 25 to 37 °C, and specifically, it can be 26 °C, 28 °C, 30 °C, 32 °C, 34 °C, 35 °C, 36 °C.

[0051] In the present invention, the preparation method of the lactate oxidase solution is to mix lactate oxidase with water to obtain a mixed solution, and then mix the mixed solution with an aqueous acetic acid solution of chitosan.

[0052] In the present invention, the volume ratio of the mixed solution to the aqueous acetic acid solution of chitosan is 1 to 1.5:1, preferably 1 to 1.4:1, further preferably 1 to 1.2:1, and still further preferably 1:1.

[0053] In the present invention, the mass concentration of lactate oxidase in the mixed solution is 8 to 12 mg / mL, and specifically, it can be 8.5 mg / mL, 9 mg / mL, 9.5 mg / mL, 10 mg / mL, 10.5 mg / mL, 11 mg / mL, 11.5 mg / mL; the mass concentration of chitosan in the aqueous acetic acid solution of chitosan is 0.8 to 1.2 wt.%, and specifically, it can be 0.8 wt.%, 0.9 wt.%, 1 wt.%, 1.1 wt.%, 1.2 wt.%; the molar concentration of acetic acid is 0.1 to 0.15 mmol / L, and specifically, it can be 0.11 mmol / L, 0.12 mmol / L, 0.13 mmol / L, 0.14 mmol / L.

[0054] The present invention also provides a self-powered wearable microneedle for detecting lactate in interstitial fluid prepared by the above preparation method.

[0055] The self-driven wearable microneedles of the present invention can be used to detect lactic acid in interstitial fluid.

[0056] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0057] Example 1

[0058] Pour commercial AB epoxy glue (A component: epoxy resin, B component: polyetheramine, Wenzhou Yinghuoban Technology Co., Ltd., A:B mass ratio = 3:1) into a measuring cup, and then add carbon nanotubes to the epoxy glue at a mass ratio of 9:1 to obtain a mixture. Stir the mixture thoroughly for 30 min until it is evenly mixed.

[0059] Put the commercially available silicone micro-needle mold into ethanol and ultrasonicate it for 30 min to remove impurities in the micro-needle channels. After drying, pour the obtained mixture into the mold, cover the mold lid, place it in a centrifuge tube, and centrifuge it at 3500 rpm to make the mixture penetrate into the micro-channels. Then remove the lid of the centrifuged mold, wipe off the mixture on the edge of the mold, continue to fill the mixture, insert the wire into the mixture, and then place it in an oven and dry it at 70 °C for 12 h to complete the curing of the micro-needles. Subsequently, peel off the cured micro-needles; the schematic diagram of the preparation of the micro-needles is as Figure 1 shown (the insertion of the wire is not shown), and the physical picture is as shown ( Figure 2 the shown micro-needles are bare micro-needles without inserted wires), and the SEM image is as Figure 2 shown, where Figure 3 (a) in it is a planar SEM image, Figure 3 (b) in it is a cross-sectional SEM image. The preparation process of the micro-needles can be understood from Figure 3 . Figure 1 is the physical picture of the prepared micro-needle patch. It can be seen that due to the introduction of carbon nanotubes, the micro-needles show a uniform black appearance. Each micro-needle has a complete conical geometric structure, where the effective action area is 6.15 mm × 6.15 mm, and the overall patch size is a square structure of 8.9 mm × 8.9 mm, where the thickness of the base part is 2 mm. It can be seen from Figure 2 that the diameter of the micro-needles is 300 μm, the center distance between adjacent needle tips is 650 μm, and the surface is complete and smooth. From the cross-sectional morphology, it can be seen that the length of the micro-needles is 800 μm, the diameter of the needle tips is 15 μm, and the needle bodies are in an upright state without observing bending deformation. Given that the human dermis is located about 0.5 - 2 mm below the epidermis, the structural parameters of the micro-needles indicate their potential feasibility for detecting skin interstitial fluid.

[0060] Place the above-prepared microneedles in an aqueous mixed solution of chloroplatinic acid and formic acid for Pt nanoparticle deposition (ensure that the tip and the base surface of the microneedles in contact with the microneedles are immersed in the deposition solution. Among them, the molar concentration of chloroplatinic acid is 5 mmol / L, the molar concentration of formic acid is 1.5 mmol / L, the deposition voltage is -0.1 V, and the deposition time is 30 s) to obtain microneedle A. The mapping diagram of microneedle A is as shown in Figure 3 (b) in Figure 4 . It can be seen from (b) in

[0061] that the platinum (Pt) element is evenly distributed on the surface of the microneedles, indicating that the deposition process of platinum nanoparticles is successfully completed. Figure 4 (a) in Figure 4 . It can be seen from (a) in

[0062] that the gold (Au) element is evenly distributed on the surface of the microneedles, indicating that the gold layer modification process is successfully completed.

[0063] Test example

[0064] Insert microneedle A and microneedle B into agarose gels containing different concentrations of lactic acid (the specific concentrations of lactic acid are 0, 0.5, 1, 1.5, 2, 4, 6, 8, 10 mmol / L). Use an electrochemical workstation with microneedle A as the counter electrode and microneedle B as the working electrode to measure their open-circuit voltages. Measuring the open-circuit voltage is for lactic acid quantification and also to reflect the output voltage of the fuel cell. The relationship diagram between the open-circuit voltage and the lactic acid concentration is as shown in Figure 4 . It can be seen from Figure 5 that there is a good linear relationship between lactic acid and the open-circuit voltage. The linear regression equation is as shown in Figure 5 . It can be seen from Figure 6 Figure 6 that its linear regression equations are y = 0.037×C Lactate – 0.1979 (R 2 = 0.9878) and y = 0.013×C Lactate – 0.1517 (R 2= 0.9886), and the limit of detection (LOD) was 0.11 mM.

[0065] Example 2

[0066] Pour the commercial AB epoxy resin (A component: epoxy resin, B component: polyetheramine, Wenzhou Yinghuoban Technology Co., Ltd., A:B mass ratio = 3.5:1) into a measuring cup, and then add carbon nanotubes to the epoxy resin at a mass ratio of 4.5:0.6 to obtain a mixture. Stir the mixture thoroughly for 30 min until it is well mixed.

[0067] Place the commercially available silicone micro-needle mold in ethanol and sonicate for 30 min to remove impurities in the micro-needle channels. After drying, pour the obtained mixture into the mold, cover the mold lid, place it in a centrifuge tube, and centrifuge at 3500 rpm to allow the mixture to penetrate into the micro-channels. Then remove the lid of the centrifuged mold, wipe off the mixture on the edge of the mold, continue to fill the mixture, insert the wire into the mixture, and then dry it in an oven at 60 °C for 12 h to complete the curing of the micro-needles. Subsequently, peel off the cured micro-needles;

[0068] Deposit Pt nanoparticles on the micro-needles prepared above by placing them in an aqueous mixed solution of chloroplatinic acid and formic acid (ensure that the tip and the surface of the base of the micro-needles in contact with the micro-needles are immersed in the deposition solution, where the molar concentration of chloroplatinic acid is 4 mmol / L, the molar concentration of formic acid is 1 mmol / L, the deposition voltage is -1.5 V, and the deposition time is 90 s) to obtain micro-needle A.

[0069] At the same time, sputter the micro-needles prepared above with gold for 100 s, and then incubate them in a lactate oxidase solution (mix an aqueous lactate oxidase solution with a mass concentration of 10 mg / mL and 1 wt.% chitosan dissolved in 0.1 mol / L acetic acid aqueous solution in equal volume to obtain a lactate oxidase solution; the incubation time is 1 h and the incubation temperature is 25 °C). Then dry them at room temperature to obtain micro-needle B.

[0070] Use micro-needle A as the counter electrode and micro-needle B as the working electrode to obtain a self-powered wearable micro-needle for lactate detection in interstitial fluid.

[0071] Example 3

[0072] Pour the commercial AB epoxy resin (A component: epoxy resin, B component: polyetheramine, Wenzhou Yinghuoban Technology Co., Ltd., A:B mass ratio = 4:1) into a measuring cup, and then add carbon nanotubes to the epoxy resin at a mass ratio of 5:0.5 to obtain a mixture. Stir the mixture thoroughly for 30 min until it is well mixed.

[0073] Put the commercially available silicone rubber microneedle mold into ethanol and ultrasonicate it for 30 min to remove impurities in the microneedle channels. After drying, pour the obtained mixture into the mold, cover the mold lid, place it in a centrifuge tube, and centrifuge at 3500 rpm to allow the mixture to penetrate into the microchannels. Then remove the lid of the centrifuged mold, wipe off the mixture on the edge of the mold, continue to load the mixture, insert the wire into the mixture, and then place it in an oven and dry at 80 °C for 8 h to complete the curing of the microneedles. Subsequently, peel off the cured microneedles;

[0074] Place the microneedles prepared above in a mixed aqueous solution of chloroplatinic acid and formic acid for Pt nanoparticle deposition (ensure that the tip and the base surface of the microneedle in contact with the microneedle are immersed in the deposition solution, where the molar concentration of chloroplatinic acid is 6 mmol / L, the molar concentration of formic acid is 2 mmol / L, the deposition voltage is -0.5 V, and the deposition time is 50 s) to obtain microneedle A.

[0075] At the same time, perform gold spraying treatment on the microneedles prepared above for 50 s, and then incubate them in a lactate oxidase solution (mix an aqueous lactate oxidase solution with a mass concentration of 10 mg / mL and 1 wt.% chitosan dissolved in 0.1 mol / L acetic acid aqueous solution in equal volume to obtain a lactate oxidase solution; the incubation time is 1 h and the incubation temperature is 25 °C). Then dry at room temperature to obtain microneedle B.

[0076] Use microneedle A as the counter electrode and microneedle B as the working electrode to obtain a self-driven wearable microneedle for lactate detection in interstitial fluid.

[0077] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The same or similar parts among the various embodiments can be referred to each other.

[0078] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A preparation method of a self-driven wearable microneedle for detecting lactic acid in interstitial fluid, characterized in that, It includes the following steps: 1) Mix epoxy resin, polyetheramine and carbon nanotubes to obtain a mixture; 2) Add the mixture into a microneedle mold, add a wire to form an electrical connection between the wire and the conductive mixture, and obtain microneedles after curing; 3) Deposit Pt nanoparticles on the microneedles obtained in step 2) to obtain microneedles A; The microneedles obtained in step 2) are successively subjected to gold spraying treatment and incubation with a lactate oxidase solution to obtain microneedles B; 4) Use microneedles A as the counter electrode and microneedles B as the working electrode to obtain self-driven wearable microneedles for lactate detection in interstitial fluid.

2. The preparation method of a self-powered wearable microneedle for lactic acid detection in interstitial fluid according to claim 1, characterized in that, In step 1), the mass ratio of the epoxy resin to the polyetheramine is 3-4:1; the total mass of the epoxy resin and the polyetheramine to the mass of the carbon nanotubes is 4:0.4-0.

6.

3. The preparation method of a self-powered wearable microneedle for lactic acid detection in interstitial fluid according to claim 2, characterized in that, In step 2), the curing temperature is 60-80°C and the curing time is 6-12 h.

4. The preparation method of a self-powered wearable microneedle for lactic acid detection in interstitial fluid according to any one of claims 1 to 3, characterized in that, In step 3), the deposition solution for Pt nanoparticle deposition is an aqueous mixed solution of chloroplatinic acid and formic acid; The molar concentration of chloroplatinic acid in the deposition solution is 4-6 mmol / L, and the molar concentration of formic acid is 1-2 mmol / L.

5. The preparation method of a self-powered wearable microneedle for lactic acid detection in interstitial fluid according to claim 4, wherein, The deposition voltage for Pt nanoparticle deposition is -0.5-0 V, and the deposition time is 30-180 s.

6. The preparation method of a self-powered wearable microneedle for lactic acid detection in interstitial fluid according to claim 5, characterized in that, In step 3), the time for gold spraying treatment is 30-120 s.

7. The preparation method of a self-powered wearable microneedle for lactic acid detection in interstitial fluid according to claim 5 or 6, characterized in that, The incubation time of the lactate oxidase solution is 0.5-2 h, and the incubation temperature is 25-37°C; The preparation method of the lactate oxidase solution is to mix lactate oxidase with water to obtain a mixed solution, and then mix the mixed solution with an aqueous acetic acid solution of chitosan.

8. The preparation method of a self-powered wearable microneedle for lactic acid detection in interstitial fluid according to claim 7, characterized in that, The volume ratio of the mixed solution to the aqueous acetic acid solution of chitosan is 1-1.5:1; The mass concentration of lactate oxidase in the mixed solution is 8-12 mg / mL, the mass concentration of chitosan in the aqueous acetic acid solution of chitosan is 0.8-1.2 wt.%, and the molar concentration of acetic acid is 0.1-0.15 mmol / L.

9. Self-driven wearable microneedles for lactate detection in interstitial fluid prepared by the preparation method according to any one of claims 1-8.

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