A Ru / RuO2 nanofoam enzyme and its preparation method and application

Abstract

The present invention provides a Ru / RuO2 nanofoam enzyme and its preparation method and application, belonging to the field of nanozyme technology. The preparation method of the Ru / RuO2 nanofoam enzyme comprises the following steps: after uniformly mixing graphene, a ruthenium precursor and a solvent, reflux reaction, and collecting a solid product A; mixing the solid product A with a molten salt 1 and grinding it, then adding it to a molten salt 2 in a molten state and keeping it warm, cooling it after the insulation is completed, washing it, and drying it to obtain the Ru / RuO2 nanofoam enzyme. The preparation method of the present invention does not require a strict inert atmosphere and a complex calcination process, and the method is simple; the colorimetric sensing method for glucose detection based on the nanozyme has an extremely low detection limit, exhibits high specificity and sensitivity, and is suitable for accurate glucose detection.

Description

Technical Field

[0001] The present invention relates to the technical field of nanoenzymes, and in particular to a Ru / RuO2 nanofoam enzyme and a preparation method and application thereof. Background Art

[0002] Hyperglycemia is one of the main causes of the development and progression of diabetic nephropathy. It causes severe damage to the kidneys by causing glomerular hyperperfusion, hyperfiltration, tubular damage, and inflammatory responses. Long-term hyperglycemia can lead to thickening of the glomerular basement membrane, tubulointerstitial fibrosis, and a gradual increase in urinary protein, which may eventually develop into diabetic nephropathy. Blood glucose testing plays an important clinical role in the prevention and management of diabetic nephropathy. Regular monitoring of blood glucose levels can promptly detect abnormal blood glucose levels and initiate intervention, effectively preventing the onset of diabetic nephropathy. Furthermore, during the treatment of diabetic nephropathy, strict blood glucose control can mitigate further deterioration of the disease, slow the decline of renal function, and provide a good foundation for the patient's recovery. Therefore, blood glucose testing is not only an important part of the daily management of diabetic patients, but also a crucial means of protecting kidney health and improving quality of life.

[0003] Common blood glucose monitoring technology is based on natural glucose oxidase (GOx) sensors. Glucose can be decomposed into gluconic acid and hydrogen peroxide (H2O2) under the action of natural glucose oxidase. The concentration of hydrogen peroxide is then detected by colorimetry to indirectly measure blood glucose levels. The advantages of this method are its ease of operation, high sensitivity and specificity, and its suitability for the blood glucose monitoring needs of most patients. However, this detection technology also has some shortcomings, mainly including the following: 1) The natural biological enzyme in traditional glucose oxidase sensors is sensitive to temperature and pH, and is easily deactivated during long-term storage and use, affecting detection accuracy. 2) The extraction and purification process of natural biological enzymes is complex and costly, limiting their large-scale application.

[0004] A promising solution is to replace traditional natural enzymes with nanozymes. Nanozymes are a new generation of artificial enzyme mimics, a class of nanomaterials with catalytic efficiency and enzymatic reaction kinetics similar to those of natural enzymes. Compared to traditional natural enzymes, they are more stable and can maintain high activity under extreme conditions. Therefore, using nanozyme materials with peroxidase-like activity to replace natural enzymes and applying them to blood glucose meters can greatly improve the lifespan of the instruments. However, the activity of currently synthesized nanozymes used for blood glucose testing is relatively low, limiting their application.

[0005] The construction of coherent grain boundaries can induce significant charge redistribution, thereby establishing a metastable electronic state and significantly enhancing the catalytic activity of nanozymes. However, most heterojunctions have large lattice mismatches and multiple dangling bonds, often exhibiting non-coherent structures. Therefore, developing a simple and effective method to synthesize highly active nanozymes with abundant coherent grain boundaries to replace natural enzymes for the detection of glucose in blood is of great clinical significance. Summary of the Invention

[0006] In light of this, the present invention aims to provide a Ru / RuO2 nanofoam enzyme, its preparation method, and application. The graphene-confined Joule-heated molten salt calcination method proposed in this invention promotes uniform and rapid nucleation of different crystals, inhibits the agglomeration and overgrowth of single crystals, and thus facilitates the formation of nanozymes with abundant coherent grain boundaries. These unique coherent grain boundaries induce significant charge redistribution, thereby establishing a metastable electronic state and significantly enhancing the catalytic activity of the nanozyme. When this Ru / RuO2 nanofoam enzyme with abundant coherent grain boundaries is used for glucose detection, the colorimetric sensor exhibits a limit of detection (LOD) as low as 28.5µM, which is of great significance for the accurate and rapid measurement of blood glucose.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] One of the technical solutions of the present invention is a method for preparing Ru / RuO2 nanofoam enzyme, comprising the following steps:

[0009] After the graphene, ruthenium precursor and solvent are uniformly mixed, the mixture is refluxed to react, and the solid product A is collected;

[0010] The solid product A and molten salt 1 are mixed and ground, and then added to molten salt 2 for heat preservation. After the heat preservation is completed, it is cooled to room temperature, washed, and dried to obtain the Ru / RuO2 nanofoam enzyme.

[0011] In the present invention, the ruthenium precursor is ruthenium chloride, ruthenium acetylacetonate or ruthenium oxalate; the mass ratio of the graphene to the ruthenium precursor is 1:0.5~1.5.

[0012] In the present invention, the solvent is ethylene glycol. The amount of ethylene glycol used is not particularly limited in the present invention, and any amount of solvent known in the art that can meet the requirements of the reflux reaction can be selected, for example, 1-5 mL of ethylene glycol is added per 1 mg of graphene.

[0013] The reason why the present invention sets the ratio of graphene and ruthenium chloride to the above parameters is:

[0014] A high graphene ratio: on the one hand, it will cause waste, and on the other hand, too much metal is adsorbed on the graphene surface, which is easy to aggregate during calcination; a low graphene ratio: graphene cannot completely adsorb the metal in the solution.

[0015] In the present invention, the temperature of the reflux reaction is 150-180° C., and the time is 1-10 h.

[0016] Furthermore, the reflux reaction temperature is 170-180° C., and the time is 1-5 hours.

[0017] In the present invention, the molten salt 1 and the molten salt 2 are both potassium chloride or sodium chloride; the mass ratio of the solid product A to the molten salt 1 is 1:1-5.

[0018] The present invention does not impose any particular limitation on the amount of molten salt 2, and its amount can meet the amount required by the molten salt calcination method. For example, the mass ratio of Ru / RuO2 nanofoam enzyme to molten salt 2 is 1:6~15. The preparation method of the molten salt 2 in the present invention is: heating the molten salt 2 at 800°C to a molten state.

[0019] In the present invention, the insulation time is 1 to 100 seconds.

[0020] Furthermore, the insulation time is 1 to 50 seconds.

[0021] Furthermore, the insulation time is 10 to 30 seconds.

[0022] Furthermore, the insulation time is 10s.

[0023] In the present invention, if the holding time is too long, sintering is likely to occur, resulting in a decrease in the specific surface area of the product and a weakening of the performance.

[0024] The second technical solution of the present invention is a Ru / RuO2 nanofoam enzyme prepared by the above preparation method.

[0025] The third technical solution of the present invention is an application of the above-mentioned Ru / RuO2 nanofoam enzyme in glucose detection.

[0026] A fourth technical solution of the present invention is a colorimetric sensing method for glucose detection, comprising the following steps:

[0027] (1) Buffer solution 1, glucose oxidase, and glucose solution are mixed and incubated; then, the Ru / RuO2 nanofoam enzyme, 3,3',5,5'-tetramethylbenzidine (TMB), and buffer solution 2 are added to the incubated glucose solution, and the mixture is incubated. After the incubation, the absorbance of the reaction solution is measured;

[0028] (2) Establish a standard curve based on the concentration and absorbance of the glucose solution;

[0029] (3) Buffer solution 1, glucose oxidase, and the test solution are mixed and incubated; then, the Ru / RuO2 nanofoam enzyme, TMB, and buffer solution 2 are added to the incubated glucose solution and incubated. After the incubation, the absorbance of the reaction solution is measured, and the measured absorbance is then applied to the standard curve of step (2) to obtain the glucose concentration of the test solution. That is, the difference between step (3) and step (1) is that the glucose solution in step (1) is replaced by the test solution.

[0030] In the present invention, the buffer solution 1 is a PBS solution with a pH of 7; the buffer solution 2 is a sodium acetate buffer solution; the concentration of the buffer solution 2 is 0.2 M, and the pH is 4.5.

[0031] The present invention discloses the following technical effects:

[0032] The present invention uses graphene to anchor and disperse Ru ions, combined with molten salt-assisted pyrolysis technology, to in situ generate Ru / RuO2 nanofoam enzymes with rich coherent grain boundaries in an air atmosphere. This preparation process eliminates the need for a strict inert atmosphere and complex calcination process, significantly reducing preparation costs while improving production efficiency.

[0033] The nanozyme preparation method of the present invention is simple and has the advantages of high stability and low cost. It can effectively overcome the problems of easy inactivation and high price of natural enzymes in traditional blood glucose testing, and provides a more economical and reliable solution for blood glucose testing.

[0034] The nanozyme prepared by the present invention has abundant coherent grain boundaries and nanofoam properties. The coherent grain boundaries can optimize the coordination environment of the Ru active site, triggering charge redistribution of the Ru element at the interface, thereby significantly enhancing the catalytic activity of the nanozyme. In addition, the foaming properties of the nanozyme facilitate the adsorption, activation, and desorption of substrate molecules at the Ru active site, thereby significantly improving the sensitivity and service life of the glucose sensor based on Ru / RuO2 nanofoam enzyme.

[0035] Based on the nanozymes prepared in this invention, a colorimetric sensing method for glucose detection was constructed. This method has an extremely low detection limit, exhibits high specificity and sensitivity, and is suitable for accurate glucose detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0037] Figure 1 is the powder X-ray diffraction pattern of Ru / RuO2-1 in Example 1;

[0038] Figure 2 This is a scanning electron micrograph of Ru / RuO2-1 of Example 1;

[0039] Figure 3 This is the nitrogen adsorption-desorption isotherm of Ru / RuO2-1 in Example 1, and the inset is the pore size distribution diagram;

[0040] Figure 4 This is a high-resolution electron microscopy image of Ru / RuO2-1 in Example 1;

[0041] Figure 5 This is a comparison of the peroxidase-like activities of the samples of Example 1 and Comparative Examples 1-3;

[0042] Figure 6 UV absorption spectra of Ru / RuO2 nanozyme system with different glucose concentrations;

[0043] Figure 7 This is the relationship curve between UV absorption value and glucose concentration. DETAILED DESCRIPTION

[0044] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0045] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value within any stated value or stated range, and each smaller range between any other stated value or intermediate value within the stated range, is also encompassed within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0046] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0047] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.

[0048] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0049] The present invention adopts the following methods to detect the activity of Ru / RuO2 nanofoam enzyme and the detection sensitivity of Ru / RuO2 nanofoam enzyme to glucose.

[0050] (1) Activity evaluation of Ru / RuO2 nanofoam enzyme

[0051] Coherent grain boundary-rich Ru / RuO2 nanofoam enzyme suspension (5 mg / mL), TMB (1 mM), and H2O2 (100 mM) solutions were prepared in pure water, respectively. Subsequently, 150 µL of Ru / RuO2 nanofoam enzyme suspension, 150 µL of H2O2 solution, and 150 µL of TMB solution were mixed in 2550 µL of sodium acetate-acetic acid (NaAc-Hac, pH = 4.5, 0.2 M) buffer solution. After incubation at room temperature for 5 min, the absorbance of the reaction solution was measured at 652 nm using a UV-visible spectrophotometer to evaluate the activity of the Ru / RuO2 nanofoam enzyme.

[0052] (2) Evaluation of detection sensitivity

[0053] 200µL of glucose solutions of varying concentrations (0-15mM) were added to 0.5mL of PBS (pH=7.4), followed by 100µL of glucose oxidase (GOx, 2mg / mL). After incubation at 37°C for 10 minutes, 150µL of a Ru / RuO2 nanofoam enzyme suspension (5mg / mL), 200µL of a TMB solution (1mM), and 1.85mL of sodium acetate buffer (0.2M, pH=4.5) were added to the glucose solution and incubated at room temperature for 10 minutes. Finally, the absorbance of the reaction solution was measured at 652nm using a UV-visible spectrophotometer to determine the glucose content in the solution. This was used to evaluate the sensitivity of the nanozyme-based colorimetric sensing method for glucose detection.

[0054] Unless otherwise specified, the technical solutions described in the present invention are all conventional solutions in the field, and the reagents or raw materials used, unless otherwise specified, are purchased from commercial channels or have been disclosed.

[0055] In order to better understand the present invention, the content of the present invention is further illustrated below in conjunction with the examples, but the content of the present invention is not limited to the following examples.

[0056] Example 1

[0057] Step S1, adding 120 mg of graphene, 120 mg of ruthenium trichloride, and 240 mL of ethylene glycol into a round-bottom flask, ultrasonically dispersing, and then reflux reacting at 170° C. for 3 h, and then centrifugally washing to obtain a first solid A;

[0058] Step S2: adding 200 mg of the first solid substance A and 400 mg of potassium chloride into a mortar and grinding for ten minutes to obtain a second solid substance B;

[0059] Step S3, placing 5 g of potassium chloride in a muffle furnace and heating it at 850° C. until it is molten, then adding 600 mg of the second solid B to the molten potassium chloride, keeping the temperature for 10 seconds, removing the molten salt, pouring it into a graphite cooling tank and rapidly cooling it to obtain a third solid C;

[0060] Step S4: The third solid C was washed three times by centrifugation with deionized water and then dried to obtain a Ru / RuO2 nanofoam enzyme with rich coherent grain boundaries, which was named Ru / RuO2-1.

[0061] Example 2

[0062] The only difference from Example 1 is that in step S1, 120 mg of ruthenium trichloride is replaced by 60 mg of ruthenium trichloride, and the reflux reaction conditions are changed to 180° C. for 1 h. The remaining steps and parameters are the same as those in Example 1. The obtained Ru / RuO2 nanofoam enzyme is recorded as Ru / RuO2-2.

[0063] Example 3

[0064] The only difference from Example 1 is that 400 mg of potassium chloride is replaced by 200 mg of potassium chloride in step S2, and the remaining steps and parameters are the same as those in Example 1. The obtained Ru / RuO2 nanofoam enzyme is recorded as Ru / RuO2-3.

[0065] Example 4

[0066] The only difference from Example 1 is that potassium chloride is used instead of sodium chloride in the preparation process, and the remaining steps and parameters are the same as those in Example 1. The obtained Ru / RuO2 nanofoam enzyme is recorded as Ru / RuO2-4.

[0067] Example 5

[0068] The only difference from Example 1 is that ruthenium trichloride is used in the preparation process instead of ruthenium oxalate of equal mass, and the remaining steps and parameters are the same as those in Example 1. The obtained Ru / RuO2 nanofoam enzyme is recorded as Ru / RuO2-5.

[0069] Comparative Example 1

[0070] Step S1, same as step S1 in Example 1;

[0071] Step S2: 200 mg of the first solid substance A was placed in a muffle furnace and kept at 850° C. for 20 seconds, then taken out and cooled to obtain RuO2 nanozyme, which was named RuO2.

[0072] Comparative Example 2

[0073] Step S1, same as step S1 in Example 1;

[0074] Step S2: Place 200 mg of the first solid substance A into a tube furnace, heat to 850°C at a heating rate of 5°C / min under a reducing atmosphere (H2 / Ar: 5 / 95), keep warm for 20 seconds, and cool to obtain Ru nanozyme, named Ru.

[0075] Comparative Example 3

[0076] Step S1, same as step S1 of comparative example 2;

[0077] Step S2, same as step S2 of comparative example 2;

[0078] Step S3: 200 mg of Ru nanozyme was placed in a muffle furnace and kept at 300° C. for 0.5 h, then taken out and cooled to obtain Ru / RuO2 nanozyme, which was named Ru / RuO2-D.

[0079] Characterization and effect verification:

[0080] 1. Figure 1 This is the powder X-ray diffraction pattern of Ru / RuO2-1 in Example 1. As can be seen from the figure, Example 1 is mainly composed of two phases, Ru and RuO2. This shows that the scheme of the present invention does not require a strict inert atmosphere and a complex calcination process, and directly generates a composite material of Ru and RuO2 in situ under an air atmosphere. The synergistic effect between the different components within this composite material can significantly enhance the catalytic activity of the active site, thereby exhibiting higher nanozyme activity.

[0081] 2. Figure 2 The scanning electron micrograph of Ru / RuO2-1 prepared in Example 1 is shown. The results show that the Ru / RuO2 prepared in Example 1 mainly exhibits a porous foam structure with accumulated particles.

[0082] 3. N2 adsorption-desorption test further analyzed the pore structure of Ru / RuO2-1. Figure 3 As shown, the characteristic hysteresis loop indicates that Example 1 possesses a rich mesoporous structure. The Barrett-Joyner-Halenda (BJH) analysis results in the inset show that the pore size distribution of Example 1 is primarily concentrated in the range of 5-40 nm. This rich pore structure further demonstrates the nanofoam properties of Example 1, which facilitate the adsorption, activation, and desorption of substrate molecules at the Ru active sites, thereby significantly improving the sensitivity and service life of the Ru / RuO2 nanofoam enzyme-based glucose sensor.

[0083] 4. Figure 4 This is a high-resolution electron microscope image of Ru / RuO2-1 in Example 1. As can be seen from the figure, the coherent growth characteristics of Ru and RuO2 components in Example 1, and this coherent growth produces obvious coherent grain boundaries. The reason for the formation of this coherent characteristic is mainly due to the high-temperature potassium chloride molten salt oxidation process of graphene that uniformly adsorbs Ru ions. Graphene itself has a certain reducing property that can reduce part of the Ru element to Ru elemental substance, and the molten salt can isolate most of the air to avoid the complete oxidation of the Ru elemental substance. At the same time, some of the Ru ions loaded on the graphene will also be oxidized by the oxygen inside the molten salt to form RuO2. In addition, the confinement effect of graphene and the rapid high-temperature oxidation of the molten salt can promote the uniform and rapid nucleation of Ru and RuO2, inhibit the agglomeration and excessive growth of Ru and RuO2, and thus facilitate the formation of Ru / RuO2 nanozymes with rich coherent grain boundaries. This coherent grain boundary can optimize the coordination environment of the Ru active site, trigger the charge redistribution of the interface Ru element, thereby significantly enhancing the intrinsic catalytic activity of the nanozyme.

[0084] 5. Use pure water to prepare coherent grain boundary-rich Ru / RuO2 nanofoam enzyme suspension (5 mg / mL), TMB (1 mM), and H2O2 (100 mM) solutions, respectively. Then, 150 µL of Ru / RuO2 nanofoam enzyme, 150 µL of H2O2, and 150 µL of TMB were mixed in 2550 µL of sodium acetate-acetic acid (NaAc-Hac, pH = 4.5, 0.2 M) buffer solution. After incubation at room temperature for 5 minutes, the absorbance of the reaction solution was measured at 652 nm using a UV-visible spectrophotometer to evaluate the activity of the Ru / RuO2 nanofoam enzyme.

[0085] Figure 5The peroxidase-like activities of Example 1 and Comparative Examples 1-3 were compared. Example 1 exhibited the strongest absorption peak at 652 nm, which was stronger than Comparative Example 3, Comparative Example 2, and Comparative Example 1, respectively. This indicates that the order of nanozyme activity is Example 1 > Comparative Example 3 > Comparative Example 2 > Comparative Example 1. Table 1 lists the phase composition and pore structure information of Example 1 and Comparative Examples 1-3. As can be seen from Table 1, Comparative Example 1 and Comparative Example 2 are composed of RuO2 and Ru, respectively, while Comparative Example 3 is a mixed phase composed of RuO2 and Ru. In addition, the specific surface area and pore size distribution range of the comparative examples are much smaller than those of Example 1, especially Comparative Example 1 has almost no porous structure. The above information shows that the activity of the nanozymes with a mixed phase of RuO2 and Ru (Example 1 and Comparative Example 3) is much better than that of single-phase RuO2 (Comparative Example 1) and Ru (Comparative Example 2), indicating that the synergistic effect between RuO2 and Ru can significantly enhance the catalytic activity of the nanozymes. Furthermore, the nanozyme activity of the Ru / RuO2 nanofoam enzyme with rich coherent grain boundaries (Example 1) was significantly superior to that of the conventionally prepared Ru / RuO2-D (Comparative Example 3). The high nanozyme activity of Example 1 is primarily due to its abundant coherent grain boundaries and porous nanofoam structure.

[0086] Table 1 Phase composition and pore structure information of Example 1 and Comparative Examples 1-3

[0087]

[0088] 6. 200µL of glucose solutions of varying concentrations (0, 0.75, 1.5, 3, 4.5, 6, 7.5, 9, 10.5, 12, 13, and 15mM) were added to 0.5mL of PBS (pH 7.4), followed by 100µL of glucose oxidase (GOx, 2mg / mL). After incubation at 37°C for 10 minutes, 150µL of Ru / RuO2-1 nanofoam enzyme, 200µL of TMB solution (1mM), and 1.85mL of sodium acetate buffer (0.2M, pH 4.5) were added to the glucose solution and incubated at room temperature for 10 minutes. Finally, the absorbance of the reaction solution was measured at 652nm using a UV-visible spectrophotometer to determine the glucose content in the solution. This was used to evaluate the sensitivity of the nanozyme-based colorimetric sensing method for glucose detection.

[0089] The principle of glucose colorimetric detection relies on the oxidation of glucose catalyzed by glucose oxidase (GOx) to generate hydrogen peroxide. Under the efficient catalysis of the coherent grain boundary-rich Ru / RuO2 nanofoam enzyme, the hydrogen peroxide reacts with the colorimetric reagent (TMB), triggering a significant color change in the solution. By precisely measuring the intensity of the color (i.e., subtle changes in absorbance), we can accurately quantify the glucose concentration in the solution. Figure 6 The UV-VIS absorption spectra of glucose solutions at different concentrations, ranging from 0 to 1 mM, are shown. As the glucose concentration increases, the color of the sample solution changes from clear and colorless to a deep blue, and the absorbance at 652 nm increases with increasing glucose concentration.

[0090] Figure 7 The following curve shows the relationship between UV absorbance and glucose concentration. The data show a nearly perfect linear relationship within the concentration range of 0 to 0.5 mM, with the linear equation: y = 3.154x + 0.0047 (R² = 0.999). The detection limit for glucose is approximately 28.5 µM, demonstrating that the colorimetric sensing method based on the coherent grain boundary-rich Ru / RuO2 nanofoam enzyme exhibits excellent glucose detection sensitivity and high scientific value.

[0091] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing Ru / RuO2 nanofoam enzyme, characterized in that: The following steps are involved: After the graphene, ruthenium precursor and solvent are uniformly mixed, the mixture is refluxed to react, and the solid product A is collected; The solid product A and molten salt 1 are mixed and ground, and then added to molten salt 2 for heat preservation. After the heat preservation is completed, it is cooled to room temperature, washed, and dried to obtain the Ru / RuO2 nanofoam enzyme.

2. The method for preparing Ru / RuO2 nanofoam enzyme according to claim 1, characterized in that: The ruthenium precursor is ruthenium chloride, ruthenium acetylacetonate or ruthenium oxalate; the mass ratio of the graphene to the ruthenium precursor is 1:0.5~1.

5.

3. The method for preparing Ru / RuO2 nanofoam enzyme according to claim 1, characterized in that: The temperature of the reflux reaction is 150-180° C., and the time is 1-10 hours.

4. The method for preparing Ru / RuO2 nanofoam enzyme according to claim 1, characterized in that: The molten salt 1 and the molten salt 2 are both potassium chloride or sodium chloride; the mass ratio of the solid product A to the molten salt 1 is 1:1~5.

5. The method for preparing Ru / RuO2 nanofoam enzyme according to claim 1, characterized in that: The insulation time is 1 to 100 seconds.

6. A Ru / RuO2 nanofoam enzyme prepared by the preparation method according to any one of claims 1 to 5.

7. Use of the Ru / RuO2 nanofoam enzyme according to claim 6 in detecting glucose content.

8. A colorimetric sensing method for glucose detection, characterized in that: The following steps are involved: (1) Buffer solution 1, glucose oxidase, and glucose solution are mixed and incubated; then, the Ru / RuO2 nanofoam enzyme, TMB, and buffer solution 2 according to claim 6 are added to the incubated glucose solution, and the mixture is incubated. After the incubation, the absorbance of the reaction solution is measured; (2) Establish a standard curve based on the concentration and absorbance of the glucose solution; (3) Mixing the buffer solution 1, glucose oxidase and the test solution and incubating them; then adding the Ru / RuO2 nanofoam enzyme, TMB and buffer solution 2 described in claim 6 to the incubated glucose solution, incubating, and measuring the absorbance of the reaction solution after the incubation. Then, the measured absorbance is applied to the standard curve of step (2) to obtain the glucose concentration of the test solution.

9. The colorimetric sensing method for glucose detection according to claim 8, wherein: The buffer solution 1 is a PBS solution; the buffer solution 2 is a sodium acetate buffer solution.

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