A uric acid sensing material, electrode, preparation method and application

Abstract

The application provides a uric acid sensing material, an electrode and a preparation method and application, belongs to the field of nanomaterial preparation and electrochemical sensing technology, and provides the uric acid sensing material and the electrode with the NiFc-MOF@HMCS composite material as the high-activity catalytic core, the AOx as the selective shielding outer layer, the silane coupling covalent anchoring as the stability guarantee, the cooperation with the Bluetooth wireless integration, and realizes the high-sensitivity, high-selectivity, long-term stability and real-time continuous monitoring of interstitial fluid uric acid. After human verification, the detection result is highly consistent with that of a commercial fingertip blood detection kit, has good clinical practical potential, and provides a reliable technical tool for the individualized health management of gout and other hyperuricemia related diseases.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterial preparation and electrochemical sensing technology, specifically relating to a uric acid sensing material, electrode, preparation method, and application. Background Technology

[0002] In recent years, electrochemical sensors have been widely used in uric acid detection due to their advantages such as high sensitivity, fast response speed, and strong potential for device miniaturization. Existing uric acid electrochemical sensing electrodes typically use noble metals, metal oxides, carbon materials, conductive polymers, or their composites as the sensitive interface. However, uric acid detection still faces several challenges in complex biological fluid environments: Firstly, the redox potential of ascorbic acid, which coexists with uric acid in interstitial fluid (ISF), is similar to that of uric acid. In electrochemical detection, it readily overlaps significantly with the uric acid signal, making it the primary interfering factor for accurate uric acid detection. Traditional strategies such as potential window separation or single-material exclusion often have limited effectiveness and struggle to effectively eliminate ascorbic acid interference in real physiological samples.

[0003] Secondly, microneedle electrodes need to operate in a dynamic physiological environment for extended periods. Mechanical stress, bodily fluid erosion, and natural enzyme inactivation can cause the sensitive material to gradually detach from the electrode surface, resulting in signal drift or even loss over time, severely limiting the sensor's lifespan. Currently, most studies use simple physical adsorption or drop-coating methods to immobilize the sensitive material, resulting in weak interfacial bonding that cannot meet the requirements for long-term stable monitoring.

[0004] Third, highly active catalytic materials often tend to aggregate, which masks the active sites and results in actual catalytic efficiency far lower than the theoretical value; while simply increasing the specific surface area of ​​the support material lacks sufficient intrinsic catalytic activity.

[0005] Fourth, most existing uric acid sensors are still limited to in vitro solution detection and lack a complete technical solution that can be combined with wearable microneedle platforms for real-time monitoring of interstitial fluid.

[0006] Therefore, it is necessary to develop a new uric acid sensing material and its microneedle electrode construction method, so that it can achieve highly sensitive, highly selective and stable detection of uric acid in complex physiological environments, and further be applicable to wearable, minimally invasive, real-time interstitial fluid uric acid monitoring. Summary of the Invention

[0007] The purpose of this invention is to provide a uric acid sensing material, electrode, preparation method, and application. In view of the above-mentioned defects, the uric acid sensing material is improved and a corresponding sensing electrode is prepared to achieve wearable real-time monitoring of interstitial fluid uric acid with high sensitivity, high selectivity, and long-term stability in a real physiological environment.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: On one hand, the present invention provides a uric acid sensing material, comprising hollow mesoporous carbon spheres and a nickel-ferrocene-based metal-organic framework material loaded on the hollow mesoporous carbon spheres. The hollow mesoporous carbon spheres are carbon sphere materials with a hollow structure and mesoporous channels. The nickel-ferrocene-based metal-organic framework material is formed by a solvothermal or hydrothermal reaction of a nickel salt with a ferrocene dicarboxylic acid organic ligand.

[0009] Preferably, the nickel salt includes one or more of nickel chloride, nickel nitrate, nickel acetate, and nickel sulfate.

[0010] Preferably, the nickel salt is nickel chloride hexahydrate.

[0011] Preferably, the ferrocene dicarboxylic acid organic ligand includes ferrocene dicarboxylic acid, ferrocene dicarboxylic acid, or derivatives thereof.

[0012] Preferably, the ferrocene dicarboxylic acid organic ligand is ferrocene dicarboxylic acid.

[0013] On the other hand, the present invention also provides a uric acid sensing electrode, the uric acid sensing electrode comprising a conductive microneedle substrate and a uric acid sensitive layer disposed on the surface of the conductive microneedle substrate, the uric acid sensitive layer comprising the aforementioned uric acid sensing material.

[0014] Preferably, the conductive microneedle substrate is an acupuncture needle.

[0015] Preferably, the acupuncture needle has a silane coupling layer on its surface, and the uric acid sensing material is loaded on the silane coupling layer.

[0016] Preferably, the silane coupling layer is formed of aminosilane.

[0017] Preferably, the aminosilane is 3-aminopropyltrimethoxysilane.

[0018] Preferably, the uric acid sensing electrode further includes an ascorbic acid oxidase layer disposed on the outside of the uric acid sensing material.

[0019] Preferably, the uric acid sensing electrode has the following hierarchical structure from the inside out: The acupuncture needle base, silane coupling layer, nickel-ferrocene-based metal-organic framework material-hollow mesoporous carbon sphere composite material layer, and ascorbic acid oxidase layer.

[0020] In another aspect, the present invention provides a method for preparing a uric acid sensing material, comprising the following steps: S1. Preparation of hollow mesoporous carbon spheres; S2. Disperse or dissolve hollow mesoporous carbon spheres with ferrocene dicarboxylic acid organic ligands in an organic solvent to obtain the first mixed system; S3. Dissolve the nickel salt in water to obtain a nickel salt solution; S4. The first mixture system is mixed with the nickel salt solution and then subjected to a hydrothermal or solvothermal reaction to load the nickel-ferrocene-based metal-organic framework material onto hollow mesoporous carbon spheres to obtain a uric acid sensing material.

[0021] Preferably, in S1, the hollow mesoporous carbon spheres are prepared by a template-assisted method.

[0022] Preferably, the template-assisted method includes: using silica spheres as templates, coating the surface of the silica spheres with resorcinol-formaldehyde resin, removing the silica template after carbonization treatment, and obtaining hollow mesoporous carbon spheres.

[0023] Preferably, the carbonization process is carried out under an inert atmosphere.

[0024] Preferably, the inert atmosphere is a nitrogen atmosphere.

[0025] Preferably, the carbonization treatment temperature is 700°C to 900°C, and the time is 1 h to 4 h.

[0026] More preferably, the carbonization treatment is carried out at 800°C for 2 hours under a nitrogen atmosphere.

[0027] Preferably, the silicon dioxide template is removed by etching with hydrofluoric acid.

[0028] Preferably, in S2, the organic solvent is N,N-dimethylformamide.

[0029] Preferably, in step S4, the hydrothermal or solvothermal reaction temperature is 100°C to 140°C, and the reaction time is 8 h to 16 h.

[0030] Preferably, the hydrothermal or solvothermal reaction temperature is 120°C to 125°C, and the reaction time is 12 h.

[0031] In addition, the present invention also provides a method for preparing a uric acid sensing electrode, comprising the following steps: A1. Electrochemical pretreatment of acupuncture needles is performed to obtain activated acupuncture needles; A2. The activated acupuncture needle is placed in a silane solution for silanization treatment, so that amino functional groups are introduced on the surface of the acupuncture needle to obtain a silane-modified acupuncture needle. A3. Load the above-mentioned uric acid sensing material onto the surface of the silane-modified acupuncture needle to obtain a composite material-modified acupuncture needle; A4. Ascorbic acid oxidase was fixed on the surface of acupuncture needles modified with composite materials to obtain uric acid sensing electrodes.

[0032] Preferably, in step A1, the electrochemical pretreatment includes performing cyclic voltammetric scans in an acidic solution.

[0033] Preferably, the acidic solution is a sulfuric acid solution.

[0034] Preferably, the concentration of the sulfuric acid solution is from 0.1 M to 1.0 M.

[0035] Preferably, the sulfuric acid solution has a concentration of 0.5 M.

[0036] Preferably, in step A2, the silane solution comprises 3-aminopropyltrimethoxysilane.

[0037] Preferably, in step A3, the uric acid sensing material is loaded onto the surface of the silane-modified acupuncture needle using an impregnation method, a drop coating method, a spray coating method, or an electrophoretic deposition method.

[0038] Preferably, in step A3, the uric acid sensing material is loaded onto the surface of the silane-modified acupuncture needle using an impregnation method.

[0039] Preferably, in step A4, ascorbic acid oxidase is fixed onto the surface of the composite material-modified acupuncture needle using a drop-coating method.

[0040] Preferably, the ascorbic acid oxidase is fixed and then cured at 0°C to 10°C.

[0041] More preferably, the ascorbic acid oxidase is fixed and then cured at 4°C.

[0042] The present invention also provides a uric acid detection device, comprising the above-mentioned uric acid sensing electrode, reference electrode and counter electrode.

[0043] Preferably, the reference electrode is a silver / silver chloride modified acupuncture needle electrode.

[0044] Preferably, the counter electrode is an acupuncture needle electrode modified with carbon material.

[0045] Preferably, the counter electrode is an acupuncture needle electrode modified with hollow mesoporous carbon spheres.

[0046] The present invention also provides a wearable uric acid detection device, including the above-mentioned uric acid sensing electrode, reference electrode, counter electrode, housing, circuit board and wireless communication module.

[0047] Preferably, the housing is a polytetrafluoroethylene (PTFE) housing.

[0048] Preferably, the circuit board is electrically connected to the uric acid sensing electrode, the reference electrode, and the counter electrode for acquiring uric acid detection signals.

[0049] Preferably, the wireless communication module is a Bluetooth communication module, used to transmit the uric acid detection signal to the mobile terminal.

[0050] The present invention also provides the application of the above-mentioned uric acid sensing material, uric acid sensing electrode, uric acid detection device or wearable uric acid detection device in uric acid detection.

[0051] Preferably, the uric acid detection is the detection of uric acid in a biological fluid.

[0052] Preferably, the biofluid includes blood, serum, sweat, urine, tissue fluid, or interstitial fluid.

[0053] Preferably, the biofluid is an interstitial fluid.

[0054] Preferably, the uric acid detection is real-time detection, continuous detection, in-situ detection, or wearable detection.

[0055] The technical solution of this invention solves the key problems of the prior art through the following technical means: In terms of selectivity, this invention constructs a spatially partitioned functional interface of "internal catalysis-external shielding": the inner NiFc-MOF@HMCS synergistically catalyzes the electrochemical oxidation of uric acid through nickel active sites and ferrocene redox relays; the outer fixed AOx catalyzes and decomposes the interfering ascorbic acid, so that it is consumed before reaching the inner catalytic interface, fundamentally eliminating the interference of ascorbic acid and realizing highly selective uric acid detection.

[0056] In terms of stability, this invention introduces 3-aminopropyltrimethoxysilane (APTM) to silanize the surface of the acupuncture needle, introducing a large number of amino functional groups on the electrode surface. Through the chemical bonding between the amino groups and NiFc-MOF@HMCS, the material is covalently anchored, constructing a robust "material-electrode" chemical interface, which significantly enhances the mechanical stability and long-term operational reliability of the sensor in complex dynamic physiological environments.

[0057] In terms of catalytic activity and mass transfer efficiency, the HMCS support has a hollow mesoporous structure, providing a high specific surface area and excellent mass transfer channels, ensuring that uric acid molecules can diffuse efficiently to the active sites; NiFc-MOF ultrathin nanosheets are anchored in situ on the HMCS surface, fully exposing the active sites and avoiding activity loss caused by material agglomeration; the synergistic effect of the dual active sites of nickel active sites and ferrocene redox relay further improves the intrinsic catalytic efficiency.

[0058] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention uses hollow mesoporous carbon spheres as conductive and mass transfer carriers. The hollow structure and mesoporous channels improve the mass transfer efficiency of uric acid molecules, while providing a large specific surface area, which is beneficial for exposing more catalytic active sites.

[0059] 2. This invention loads nickel-ferrocene-based metal-organic framework materials onto hollow mesoporous carbon spheres to form a composite catalytic material that combines the advantages of metal active centers, ferrocene redox activity, and carbon sphere conductivity and mass transfer, which is beneficial to improving the electrochemical oxidation response of uric acid.

[0060] 3. This invention introduces amino functional groups on the surface of acupuncture needles through a silane coupling strategy, enabling uric acid sensing materials to be stably loaded on the surface of acupuncture needles, which significantly improves the interfacial stability of microneedle electrodes in long-term storage, continuous detection and dynamic physiological environments.

[0061] 4. The present invention introduces an ascorbic acid oxidase layer on the outer layer of the composite catalytic material, which can reduce the influence of coexisting interfering substances such as ascorbic acid on uric acid detection, forming a functional sensing interface that combines inner catalysis and outer shielding, thereby improving detection selectivity.

[0062] 5. This invention uses acupuncture needles as the conductive substrate for microneedles, which has the advantages of simple structure, high mechanical strength, low cost, easy preparation and suitability for minimally invasive contact with interstitial fluid, and can be used to construct wearable uric acid detection devices.

[0063] 6. The uric acid sensing electrode of the present invention can be integrated with a reference electrode, a counter electrode, a miniaturized circuit board and a wireless communication module to realize real-time, continuous or wearable monitoring of uric acid levels in interstitial fluid, and has good prospects for practical application. Attached Figure Description

[0064] Figure 1 The image shows the characterization of NiFc-MOF@HMCS in Embodiment 2 of the present invention, where the left side is the TEM image and the right side is the mapping image. Figure 2 The NiFc-MOF@HMCS in Test Example 1 of this invention 0.5 / AN, FeFc-MOF@HMCS 0.5 / AN, CoFc-MOF@HMCS 0.5 / AN and ZnFc-MOF@HMCS 0.5 Voltammetric curve of the / AN microelectrode in a 0.1 M phosphate buffer solution containing 500 μM uric acid; Figure 3 In Example 4 of this invention, different concentrations of UA were injected into 0.1 M PBS to obtain AOx / NiFc-MOF@HMCS. 0.5 Chronocurrent curve of the / AN microelectrode; Figure 4 The NiFc-MOF@HMCS for uric acid detection with / without APTM microelectrode prepared in Test Example 2 of this invention 0.5 Long-term stability plot; Figure 5The following are detection current diagrams of two microelectrodes in the anti-interference experiment of test example 3 of the present invention, where (a) shows the microelectrode without AOx and (b) shows the microelectrode with AOx. Figure 6 The comparative electrodes in Test Example 4 of this invention are NiFc-MOF / AN, HMCS / AN, and NiFc-MOF@HMCS. 0.5 Chronoamperometry curves of AN injected with different concentrations of UA in 0.1 M PBS; Figure 7 This is a schematic diagram of the wearable sensor in Embodiment 6 of the present invention, wherein (a) is a photograph of the actual sensor and (b) is a schematic diagram of the electrode being inserted into the skin; Figure 8 This is a data graph showing the real-time monitoring of uric acid in interstitial fluid by a wearable sensor in Embodiment 7 of the present invention. Detailed Implementation

[0065] To enable those skilled in the art to better understand the present application, the technical solutions in specific embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by those skilled in the art.

[0066] Unless otherwise stated, all reagents and materials used in the following examples are commercially available, and all experimental methods employed are conventional methods in the art.

[0067] Example 1 This embodiment provides a method for preparing hollow mesoporous carbon spheres.

[0068] First, 260 mL of ethanol and 60 mL of water were mixed, and 10 mL of ammonia was added. The mixture was stirred at room temperature. Then, 24 mL of tetrapropoxysilane was added to the mixture, and stirring was continued for 20 minutes. Finally, the resin monomer (2.4 g of resorcinol and 3.2 mL of formaldehyde) was added, and the mixture was stirred at room temperature for 24 hours. SiO2@RF was obtained by centrifugation, washed until the supernatant was clear, and then freeze-dried.

[0069] Subsequently, the obtained composite precursor (SiO2@RF) was subjected to high-temperature carbonization under a nitrogen atmosphere. Preferably, the carbonization temperature was 800℃ and the holding time was 2 h. After carbonization, it was naturally cooled to room temperature to obtain a silica sphere / carbon composite material.

[0070] Then, the silica template was removed by etching with hydrofluoric acid. After washing, centrifugation and drying, hollow mesoporous carbon spheres were obtained, denoted as HMCS.

[0071] The prepared HMCS has a hollow structure and mesoporous channels, which can provide mass transfer channels for the diffusion of uric acid molecules and provide a carrier for the subsequent loading of nickel-ferrocene-based metal-organic framework materials.

[0072] Example 2 This embodiment provides a method for preparing a uric acid sensing material.

[0073] Take 1 mmol of HMCS prepared in Example 1 and 0.5 mmol of ferrocene dicarboxylic acid, add them to 8 mL of N,N-dimethylformamide, and disperse by sonication or stirring to obtain the first solution.

[0074] Take another 0.5 mmol of nickel chloride hexahydrate, add it to 4 mL of deionized water and dissolve it to obtain a second solution.

[0075] The first and second solutions were mixed and transferred to a 15 mL stainless steel high-pressure reactor. The reactor was sealed and reacted at 120°C to 125°C for 12 hours. After the reaction was complete, the reactor was allowed to cool naturally to room temperature, and the product was removed.

[0076] The obtained product was washed sequentially with deionized water and ethanol to remove unreacted and poorly adhered substances. Subsequently, the product was dried overnight in a vacuum oven at 60°C to obtain a nickel-ferrocene-based metal-organic framework-hollow mesoporous carbon sphere composite material, denoted as NiFc-MOF@HMCS. 0.5 .

[0077] like Figure 1 As shown, the layered NiFc-MOF can be anchored to the surface or internal cavity of hollow mesoporous carbon spheres through non-covalent interactions such as van der Waals forces. Thanks to the unique three-dimensional porous structure of the hollow mesoporous carbon spheres, they not only serve as a conductive support framework to improve the electron transport capability of the composite material, but also effectively alleviate the stacking and aggregation between NiFc-MOF layers, thereby exposing more accessible catalytic active sites. Furthermore, the abundant mesoporous channels facilitate the rapid penetration of electrolyte ions and the mass transfer and diffusion of uric acid molecules, further promoting the interfacial electrocatalytic reaction kinetics. These structural advantages collectively endow the NiFc-MOF@HMCS composite material with higher active site utilization and superior uric acid electrocatalytic oxidation performance.

[0078] In this composite material, HMCS provides high specific surface area, good conductivity, and fast mass transfer channels; the nickel-ferrocene-based metal-organic framework provides the active sites and redox-mediating effects required for the electrochemical oxidation of uric acid. The combination of HMCS and NiFc-MOF is not a simple physical mixture. The hollow mesoporous structure of HMCS provides continuous mass transfer channels and a large loading area, making it easier for uric acid molecules to diffuse to the catalytic active sites; NiFc-MOF provides nickel active centers and redox activity involving ferrocene groups. The combination improves both the accessibility of active sites and the electron transfer efficiency, resulting in a superior electrochemical response to uric acid compared to either HMCS or NiFc-MOF alone.

[0079] Example 3 This embodiment provides a method for preparing a uric acid sensing electrode.

[0080] First, bare acupuncture needles were used as conductive microneedle substrates. The bare acupuncture needles were placed in a 0.5 M sulfuric acid solution for cyclic voltammetry scanning to remove surface impurities and activate the needle surface, resulting in activated acupuncture needles.

[0081] Subsequently, the activated acupuncture needles were immersed in a 3-aminopropyltrimethoxysilane solution for silanization treatment, which formed a silane coupling layer containing amino functional groups on the surface of the acupuncture needles, thus obtaining APTM-modified acupuncture needles.

[0082] Then, the APTM-modified acupuncture needles were immersed in NiFc-MOF@HMCS. 0.5 In the dispersion, NiFc-MOF@HMCS 0.5 The composite material is loaded onto the surface of an acupuncture needle. The amino functional groups introduced by APTM can interact with the composite material, thereby improving the performance of NiFc-MOF@HMCS. 0.5 Adhesion stability on the surface of acupuncture needles.

[0083] Finally, the ascorbic acid oxidase solution was drop-coated onto NiFc-MOF@HMCS. 0.5 The surface of acupuncture needles was modified and fixed at 4°C to obtain a uric acid sensing microneedle electrode, denoted as AOx / NiFc-MOF@HMCS. 0.5 / AN electrode.

[0084] In this designation, AN represents an acupuncture needle, and AOx represents ascorbic acid oxidase. The electrode comprises an acupuncture needle substrate, a silane coupling layer, and NiFc-MOF@HMCS. 0.5 A multi-layered functional structure consisting of a composite catalytic layer and an AOx anti-interference layer.

[0085] Example 4 This embodiment tests the electrochemical response of the uric acid sensing microneedle electrode. The AOx / NiFc-MOF@HMCS electrode prepared in Example 3 was used. 0.5 An electrochemical testing system was constructed using an AN electrode as the working electrode, a silver / silver chloride electrode as the reference electrode, and a carbon-modified electrode as the counter electrode.

[0086] The electrodes were placed in 0.1 M phosphate buffer, and uric acid solutions of different concentrations were gradually added under stirring. The current response was recorded using chronoamperometry.

[0087] like Figure 3 As shown, the test results indicate that with increasing uric acid concentration, AOx / NiFc-MOF@HMCS 0.5 The / AN electrode produces a clear and stable stepped current response, indicating that it can respond rapidly to changes in uric acid concentration. The linear detection range of this electrode covers the physiologically relevant range of uric acid concentration in interstitial fluid, suggesting its suitability for uric acid detection in interstitial fluid.

[0088] AOx / NiFc-MOF@HMCS 0.5 The good response of the / AN electrode to uric acid can be attributed to: NiFc-MOF@HMCS 0.5 Composite materials provide a highly efficient catalytic interface, HMCS improves mass transfer and conductivity processes, nickel-ferrocene-based metal-organic framework materials provide active sites for the electrochemical oxidation of uric acid, and the AOx layer can reduce the influence of interfering substances such as ascorbic acid, thereby improving detection selectivity.

[0089] Comparative Example 1 This comparative example demonstrates the preparation of composite electrodes made of different ferrocene-based metal-organic framework materials. In the preparation of the uric acid sensing material, the metal salt used was replaced with cobalt chloride; the remaining steps were the same as in Example 2, resulting in CoFc-MOF@HMCS. 0.5 During electrode fabrication, APTM-modified acupuncture needles were immersed in CoFc-MOF@HMCS. 0.5 In the dispersion, the remaining steps are the same as in Example 3 to prepare AOx / CoFc-MOF@HMCS. 0.5 / AN electrode.

[0090] Comparative Example 2 This comparative example demonstrates the preparation of composite electrodes made of different ferrocene-based metal-organic framework materials. In the preparation of the uric acid sensing material, the metal salt used was replaced with zinc chloride; the remaining steps were the same as in Example 2, resulting in ZnFc-MOF@HMCS. 0.5 During electrode fabrication, APTM-modified acupuncture needles were immersed in ZnFc-MOF@HMCS. 0.5In the dispersion, the remaining steps are the same as in Example 3 to prepare AOx / ZnFc-MOF@HMCS. 0.5 / AN electrode.

[0091] Comparative Example 3 This comparative example demonstrates the preparation of composite electrodes made of different ferrocene-based metal-organic framework materials. In the preparation of the uric acid sensing material, the metal salt used was replaced with ferric chloride; the remaining steps were the same as in Example 2, resulting in FeFc-MOF@HMCS. 0.5 During electrode fabrication, APTM-modified acupuncture needles were immersed in FeFc-MOF@HMCS. 0.5 In the dispersion, the remaining steps are the same as in Example 3 to prepare AOx / FeFc-MOF@HMCS. 0.5 / AN electrode.

[0092] Test Example 1 This test case compares different nickel-ferrocene-based metal-organic framework composite electrodes to illustrate the advantages of nickel-ferrocene-based metal-organic frameworks in uric acid detection.

[0093] The different working electrodes prepared in Example 3 and Comparative Examples 1-3 were combined with a silver / silver chloride reference electrode and a counter electrode to form a three-electrode system, and cyclic voltammetry was performed in 0.1 M phosphate buffer containing 500 μM uric acid. The test potential range was -0.2 V to 0.6 V, and the scan rate was 50 mV / s.

[0094] like Figure 2 As shown, the test results indicate that using NiFc-MOF@HMCS 0.5 The modified acupuncture needle microelectrode exhibits a superior electrochemical response to uric acid, indicating that the composite of nickel-ferrocene-based metal-organic frameworks (MOFs) with HMCS can effectively enhance the catalytic performance of uric acid oxidation. Therefore, NiFc-MOF@HMCS... 0.5 Suitable as a uric acid sensing material.

[0095] Comparative Example 4 This comparative example demonstrates the preparation of a control electrode without APTM silane coupling treatment. This control electrode was directly loaded with NiFc-MOF@HMCS after activation with acupuncture needles. 0.5 Composite materials, and further fix AOx.

[0096] Test Example 2 This test case examines the effect of silane coupling on the stability of the uric acid sensing microneedle electrode. Electrodes prepared in Example 3 and Comparative Example 4 were placed in 0.1 M phosphate buffer containing 500 μM uric acid for electrochemical response testing, and their uric acid response current was repeatedly tested after different storage times.

[0097] like Figure 4 As shown, the test results indicate that the uric acid sensing microneedle electrode treated with APTM silane coupling can still maintain a high proportion of the initial current response after long-term storage; while the control electrode without APTM silane coupling treatment shows a significant decrease in response.

[0098] When nanocatalytic materials are directly loaded onto the surface of acupuncture needles, material detachment is prone to occur during continuous detection, storage, or insertion into subcutaneous tissue, leading to a decrease in current response. This invention addresses this issue by forming a coupling layer on the acupuncture needle surface using aminosilane, enabling the composite material to be stably bonded to the needle surface through amino-related interactions. Compared to electrodes without silane coupling treatment, electrodes treated with silane coupling maintain a higher uric acid response current even after long-term storage. This result demonstrates that the silane coupling layer can significantly enhance the performance of NiFc-MOF@HMCS. 0.5 The adhesion stability of composite materials on the surface of acupuncture needles reduces material detachment and interface failure, thereby improving the long-term stability of uric acid sensing microneedle electrodes.

[0099] Comparative Example 5 This comparative example demonstrates the fabrication of a control electrode without fixed AOx. During electrode fabrication, APTM-modified acupuncture needles were immersed in NiFc-MOF@HMCS. 0.5 In the dispersion, the remaining steps are the same as in Example 3, except that the enzyme is not immobilized, to prepare NiFc-MOF@HMCS. 0.5 / AN electrode.

[0100] Test Example 3 This test case examines the effect of the shielding effect of AOx enzymes on the anti-interference performance of uric acid sensing microneedle electrodes. Electrodes prepared in Example 3 and Comparative Example 5 were placed in 0.1 M phosphate buffer solutions containing uric acid and different interfering substances, respectively, for electrochemical response testing.

[0101] like Figure 5 As shown in the results, the anti-interference ability of the uric acid sensing microelectrode is significantly improved after immobilizing AOx in the outer sensing layer compared to the electrode without enzyme immobilization. This result indicates that AOx outer layer modification can effectively reduce the influence of common interfering substances on the uric acid detection signal, thereby improving the detection selectivity and reliability of the electrode in complex sample environments, which is of great significance for its subsequent practical applications.

[0102] Comparative Example 6 This comparative example demonstrates the fabrication of control electrodes for HMCS / AN and NiFc-MOF / AN. During electrode fabrication, NiFc-MOF@HMCS... 0.5 Replace with HMCS or NiFc-MOF, and follow the same steps as in Example 3.

[0103] Test Example 4 This test example examines the effect of composite materials on the electrochemical performance of uric acid sensing microneedle electrodes. Electrodes prepared in Example 3 and Comparative Example 6 were placed in 0.1 M phosphate buffer solution, and uric acid solutions of different concentrations were gradually added under stirring conditions. The current response was recorded using a chronoamperometry method.

[0104] like Figure 6 As shown, the test results indicate that the HMCS / AN electrode can generate a certain current response after continuously adding different concentrations of uric acid, suggesting that the HMCS structure helps improve the conductivity and mass transfer process at the electrode interface. However, due to its limited catalytic activity, the overall response improvement is still limited. Although the NiFc-MOF / AN electrode has good catalytic active sites, it may suffer from insufficient utilization of active sites and limited mass transfer channels when loaded alone, resulting in a relatively low response current. In contrast, NiFc-MOF@HMCS... 0.5 The current response of the / AN electrode was the most significant, exhibiting a stable stepwise increase with increasing uric acid concentration. This result indicates that HMCS not only provides excellent conductivity and mass transfer support for NiFc-MOF but also helps improve the loading and dispersion of the active material; while NiFc-MOF provides effective catalytic oxidation sites for uric acid. The synergistic effect of these two factors significantly enhances the electrocatalytic response performance of the microelectrode to uric acid, providing an important foundation for achieving highly sensitive and stable uric acid detection.

[0105] Example 5 This embodiment provides a method for preparing a reference electrode and a counter electrode for use with a uric acid sensing microneedle electrode. The reference electrode is a silver / silver chloride modified acupuncture needle electrode. Specifically, the acupuncture needle is placed in a mixed solution containing silver nitrate, sodium thiosulfate, and sodium bisulfite for electrodeposition at a deposition current of -0.01 mA for 300 to 600 s. Subsequently, the deposited acupuncture needle is sequentially immersed in a ferric chloride solution and a mixed solution containing polyvinyl butyral and sodium chloride to construct a polymer protective film layer, obtaining the silver / silver chloride modified acupuncture needle reference electrode. The counter electrode is a hollow mesoporous carbon sphere modified acupuncture needle electrode. Specifically, after cleaning and silanizing the acupuncture needle, HMCS is loaded onto the surface of the acupuncture needle using an impregnation method, obtaining an HMCS modified acupuncture needle electrode. The uric acid sensing microneedle electrode, the silver / silver chloride modified acupuncture needle reference electrode, and the HMCS modified acupuncture needle electrode can together form a micro-uric acid electrochemical detection electrode system.

[0106] Example 6 This embodiment provides a wearable uric acid detection device. For example... Figure 7 As shown, the AOx / NiFc-MOF@HMCS prepared in Example 3 0.5The AN uric acid sensing microneedle electrode, the silver / silver chloride modified acupuncture needle reference electrode prepared in Example 5, and the HMCS modified acupuncture needle electrode are embedded in a polytetrafluoroethylene shell to form a microneedle electrode array.

[0107] The polytetrafluoroethylene (PTFE) shell can be fabricated through 3D modeling and 3D printing. The tip of the acupuncture needle is exposed on the outside of the shell, allowing it to contact the skin and enter the subcutaneous interstitial fluid region; the tail of the acupuncture needle is located inside the shell and is electrically connected to the circuit board. The circuit board has electrochemical signal acquisition and wireless communication functions. The wireless communication function is Bluetooth communication. The circuit board acquires the current signal generated by the uric acid sensing microneedle electrode and transmits this signal to a mobile terminal via Bluetooth, where the mobile terminal can read, display, or analyze the data.

[0108] This wearable uric acid detection device can be used for real-time detection of uric acid content in interstitial fluid, and is suitable for scenarios such as personal health monitoring, metabolic abnormality risk assessment and chronic disease management.

[0109] Example 7 This embodiment illustrates the application of the uric acid sensing microneedle electrode of the present invention for the detection of uric acid in interstitial fluid. For example... Figure 8 As shown, the wearable uric acid detection device prepared in Example 6 is fixed to the skin surface of the subject, allowing the tip of the uric acid-sensing microneedle electrode to enter the subcutaneous interstitial fluid region. The electrochemical signal of the uric acid-sensing microneedle electrode is acquired via a circuit board and transmitted to a mobile terminal in real time via Bluetooth. During the detection process, finger-prick blood samples can be collected periodically and compared with commercial uric acid analyzers or reagent kits. The comparison results can be used to verify the accuracy of the detection results of the wearable uric acid detection device of the present invention. The detection results show that the uric acid-sensing microneedle electrode of the present invention can work stably in the subcutaneous interstitial fluid environment and can reflect changes in uric acid levels in real time. This result indicates that the uric acid-sensing microneedle electrode and wearable uric acid detection device of the present invention have the application potential for minimally invasive, real-time, and continuous uric acid monitoring.

[0110] The method for preparing uric acid sensing materials provided by this invention is simple, the raw materials are readily available, and it is suitable for mass production. The constructed uric acid sensing microneedle electrode has a compact structure and can be integrated with miniaturized circuit boards and wireless communication modules, making it suitable for wearable detection devices. This uric acid sensing microneedle electrode can be used for uric acid detection in interstitial fluid, blood, serum, sweat, urine, or other biological fluids, and is particularly suitable for monitoring uric acid levels related to hyperuricemia, gout, renal dysfunction, and metabolic diseases, showing promising prospects for industrial application.

[0111] Finally, it should be noted that the described embodiments are merely some, not all, of the embodiments of the present invention. Those skilled in the art will understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the claims and their equivalents; that is, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A uric acid sensing material, characterized in that, The invention includes hollow mesoporous carbon spheres and a nickel-ferrocene-based metal-organic framework material supported on the hollow mesoporous carbon spheres; wherein the nickel-ferrocene-based metal-organic framework material is formed by coordination of nickel ions with a ferrocene dicarboxylic acid organic ligand, specifically, the ferrocene dicarboxylic acid organic ligand is ferrocene dicarboxylic acid, and the nickel ions are derived from nickel chloride hexahydrate; the hollow mesoporous carbon spheres are used to provide mass transfer channels for uric acid molecules and loading sites for the nickel-ferrocene-based metal-organic framework material.

2. An electrode, characterized in that, It includes a conductive microneedle substrate and a uric acid sensitive layer disposed on the surface of the conductive microneedle substrate, wherein the uric acid sensitive layer includes the uric acid sensing material as described in claim 1.

3. The electrode according to claim 2, characterized in that, The uric acid-sensitive layer comprises, from the inside out: a silane coupling layer, a nickel-ferrocene-based metal-organic framework material-hollow mesoporous carbon sphere composite material layer, and an ascorbic acid oxidase layer.

4. The electrode according to claim 3, characterized in that, The silane coupling layer is formed of aminosilanes; the aminosilanes include 3-aminopropyltrimethoxysilane and / or 3-aminopropyltriethoxysilane.

5. A method for preparing the electrode according to any one of claims 2 to 4, characterized in that, Includes the following steps: S1. Preparation of hollow mesoporous carbon spheres; S2. Disperse or dissolve the hollow mesoporous carbon spheres and ferrocene dicarboxylic acid organic ligands in an organic solvent, and mix them with a nickel salt solution to carry out a hydrothermal or solvothermal reaction to obtain a nickel-ferrocene-based metal-organic framework material-hollow mesoporous carbon sphere composite material. S3. Perform electrochemical pretreatment on the conductive microneedles to obtain activated conductive microneedles; S4. The activated conductive microneedles are placed in a silane solution for silanization treatment to obtain silane-modified conductive microneedles. S5. Load the composite material obtained in S2 onto the surface of the silane-modified conductive microneedles to obtain conductive microneedles modified with composite material. S6. Ascorbic acid oxidase is immobilized on the surface of conductive microneedles modified with composite materials to obtain uric acid sensing microneedle electrodes.

6. The preparation method according to claim 5, characterized in that, In S2, the organic solvent is N,N-dimethylformamide, the nickel salt is nickel chloride hexahydrate, the ferrocene dicarboxylic acid organic ligand is ferrocene dicarboxylic acid, and the hydrothermal or solvothermal reaction temperature is 100℃~140℃, and the time is 8 h~16 h.

7. The preparation method according to claim 5, characterized in that, In S3, the electrochemical pretreatment involved cyclic voltammetry scanning in a sulfuric acid solution; in S6, ascorbic acid oxidase was fixed and then cured at 0°C to 10°C.

8. The application of the electrode according to any one of claims 2-4 in uric acid detection.

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