MnO2atZIF-67 composite nano-particle with high oxidase activity, method and application of MnO2atZIF-67 composite nano-particle

Abstract

The invention discloses MnO2 (at) ZIF-67 composite nanoparticles with high oxidase activity as well as a preparation method and application of the MnO2 (at) ZIF-67 composite nanoparticles. The preparation method comprises the following steps: uniformly mixing a potassium permanganate aqueous solution and a cerous nitrate aqueous solution to obtain a mixed solution I; and adding nitric acid into the mixed solution I, carrying out hydrothermal reaction to obtain a substance MnO2, uniformly mixing the obtained MnO2 and a methanol solution of PVP, adding cobalt nitrate hexahydrate and 2-methylimidazole, and standing to obtain the MnO2 ZIF-67 composite nanoparticles. The nano-particles with high enzymatic activity are prepared through a simple hydrothermal synthesis method, have good oxidase mimetic activity, catalyze O2 and TMB to rapidly develop color and become dark blue, and can specifically, sensitively and rapidly detect the total antioxidant capacity of cells, so that the nano-particles have good practical application value.

Description

Technical Field

[0001] The present invention relates to a MnO2@ZIF-67 composite nanoparticle, method and application, and in particular to a MnO2@ZIF-67 composite nanoparticle with high oxidase activity and a preparation method and application thereof, belonging to the technical field of detecting the overall antioxidant capacity of antioxidant molecules and cells. Background Art

[0002] Natural enzymes have a wide range of uses, but they are susceptible to environmental temperature, pH, and ionic strength. Furthermore, their immunogenicity, degradability, and manufacturing difficulties, as well as their instability, difficulty in recycling, and high cost, hinder their practical application. To overcome these drawbacks, nanozymes have emerged. Among different nanozymes, peroxidase mimics hold great potential for building bioanalytical platforms, and significant efforts have been invested in this area. However, H2O2 is destructive and can significantly compromise the high stability of peroxidase-like nanozymes in biosensing experiments. Furthermore, peroxidase-like nanozymes often possess multienzyme activity, which may affect the sensitivity and accuracy of detection. Oxidase enzymes can activate molecular oxygen to oxidize reduced substrates in the absence of H2O2. Therefore, it is urgent to consider the use of oxidase-like nanozymes to construct biosensing platforms to avoid the use of unstable H2O2 and provide more reliable and stronger output signals.

[0003] Total antioxidant capacity (TAC) refers to the sum of the antioxidant capacities of all antioxidant substances in the sample to be tested. TCA is also a clinical biochemical test indicator and can be assessed by detecting the content of antioxidants in blood, urine or other body fluids. Total antioxidant capacity can reflect the body's ability to fight free radicals and oxidative stress, and is an important tool for assessing health status and disease risk. Antioxidant capacity refers to the ability of an organism to resist free radical damage. It can inhibit the oxidative attack of free radicals on the human body and reduce the harmful effects of oxidation processes and reactive oxygen species. Current studies have shown that cells of different types or in different states exhibit different levels of reducing properties. Among the current methods for detecting the total antioxidant capacity of cells, fluorescence spectrophotometry, electrochemical biosensor methods, etc. are generally used, but these methods are relatively complicated to operate, and some require relatively expensive detection equipment, which is not conducive to the promotion and application of actual detection.

[0004] The redox state of the cell surface is closely related to cellular function and cell surface receptor-mediated signal transduction, and is involved in the development and progression of diseases. For example, the surface redox state of T cells is crucial for their activity and is one of the key mechanisms of T cell immune inactivation. When the body's antioxidant defenses are weakened, cells and tissues are more susceptible to dysfunction and / or diseases such as aging, cancer, and Alzheimer's disease. Furthermore, a relationship has been shown between the antioxidant capacity of tumor cells and drug resistance. Oxidants can prevent oxidative stress by scavenging ROS and RNS, and total antioxidant capacity (TAC) is considered an important biomarker for detecting oxidative stress. In general, antioxidants, particularly cysteine ​​(Cys), glutathione (GSH), and exogenously supplemented ascorbic acid (AA), can maintain redox homeostasis in cells and tissues. However, due to the large variety of antioxidants and their potential interactions, the analysis of individual antioxidants is challenging. Therefore, developing a rapid and convenient method to measure cell surface redox status would help reveal the relationship between cellular redox status and cellular function and potentially enable rapid drug screening at the cellular level.

[0005] Among common metal compounds with catalytic activity, manganese-based oxides have been shown to exhibit effective enzyme-like activities, such as peroxidase and oxidase mimicking activities, due to the valence state change characteristics of manganese. The oxidase-like activity of MnO2 has been widely used in the detection of biomarkers in serum and the detection of small molecules (ascorbic acid, glutathione, cysteine). MnO2 has oxidase-like activity and has the advantages of high specific surface area and high active sites. It has been widely used in the detection of serum biomarkers and antioxidant small molecules. However, manganese-based oxide nanoparticles are usually accompanied by agglomeration and poor dispersion, which usually affects their enzyme-like activity. Therefore, the oxidase activity of MnO2 itself needs to be further optimized. Summary of the Invention

[0006] In order to address the shortcomings of the above-mentioned technology, the present invention provides a MnO2@ZIF-67 composite nanoparticle with high oxidase activity and its preparation method and application. The nanoparticles with high enzyme activity are prepared by a simple hydrothermal synthesis method. Experimental studies have found that the nanoparticles have good oxidase-like activity, catalyzing O2 and 1.3,3,5,5-tetramethylbenzidine (TMB) to quickly develop a dark blue color, and can specifically, sensitively and quickly detect the total antioxidant capacity of cells, so they have good practical application value.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing MnO2@ZIF-67 composite nanoparticles with high oxidase activity, the preparation method comprising the following steps: Synthesis of S1 and MnO2

[0008] 1.1 Add potassium permanganate aqueous solution to cerium nitrate aqueous solution and stir to obtain a uniform mixed solution I; 1.2 Add nitric acid to the mixed solution I, stir evenly, and perform a hydrothermal reaction to prepare MnO2;

[0009] Synthesis of S2, MnO2@ZIF-67 composite nanoparticles

[0010] 2.1 Add the MnO2 and PVP obtained in S1 to the solvent and obtain a mixed solution II by ultrasonic treatment; 2.2 Add cobalt nitrate hexahydrate to mixed solution II to obtain mixed solution III; 2.3 Add 2-methylimidazole to mixed solution III to obtain mixed solution IV; 2.4 Let the mixed solution IV stand overnight to obtain MnO2@ZIF-67.

[0011] Preferably, in step 1.1, the potassium permanganate aqueous solution is 0.002-0.008 mol dissolved in 35 mL of water; the cerium nitrate aqueous solution is 0.001-0.002 mol dissolved in 35 mL of water.

[0012] Preferably, the optimal concentration of the potassium permanganate aqueous solution is 0.006 mol / 35 mL, and the optimal concentration of the cerium nitrate aqueous solution is 0.0017 mol / 35 mL.

[0013] Preferably, in step 1.2, the added volume of nitric acid is 4 mL.

[0014] Preferably, the temperature of the hydrothermal reaction is 100-180° C., and the reaction time is 2-5 hours.

[0015] Preferably, in step 2.1, the solvent is methanol, and the mass ratio of the added amount of PVP to MnO2 is 6:1.

[0016] 7 Preferably, in step 2.1, the ultrasonic treatment time is 30 minutes; in step 2.4, the standing time is 10-16 hours.

[0017] A MnO2@ZIF-67 composite nanoparticle is prepared by the above-mentioned preparation method of MnO2@ZIF-67 composite nanoparticles with high oxidase activity.

[0018] The invention discloses an application of MnO2@ZIF-67 composite nanoparticles, which is used for catalyzing oxygen oxidation of TMB color development, or for detecting the anti-aging and antioxidant capacity of substances, or for a kit for detecting antioxidant capacity based on colorimetric sensing technology, or for a colorimetric sensor for detecting reducing substances.

[0019] The invention discloses an application of MnO2@ZIF-67 composite nanoparticles in the screening of anti-aging drugs.

[0020] The present invention discloses a MnO2@ZIF-67 composite nanoparticle with high oxidase activity and a preparation method and application thereof. Compared with existing technologies, it has the following technical advantages: (1) Improving enzymatic activity: The present invention utilizes a simpler material synthesis method to synthesize a nanozyme with high enzymatic activity. The synthesis method is simple and controllable, does not require precise operation, and does not involve complex chemical reactions. It solves the problem of low enzymatic activity of nanozymes caused by poor aggregation and dispersibility of MnO2. The present invention synthesizes a nanocomposite material with high oxidase activity, that is, the oxidase activity is higher than that of the individual components in the composite material, and the detection sensitivity is higher.

[0021] (2) Improving the binding of nanozymes to cells: The introduction of cobalt-based metal framework components improves the surface potential of MnO2 nanoparticles, changing the surface potential from negative to positive, thereby improving the binding ability and detection sensitivity of nanozymes to cells with negative surface potential.

[0022] (3) The detection method invented has high detection sensitivity and has the advantages of simple operation, specificity, fast response, high sensitivity, and visualization. It is suitable for rapid, specific, highly sensitive, and visual rapid testing of antioxidant capacity and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a transmission electron microscope image of the morphology of the MnO2@ZIF-67 material in the embodiment;

[0024] Figure 2 This is the elemental energy spectrum of the MnO2@ZIF-67 material in the embodiment;

[0025] Figure 3 is the surface potential change in the embodiment

[0026] Figure 4 This is a diagram showing the oxidase-like activity of MnO2@ZIF-67 in the examples;

[0027] Figure 5 This is the specific response diagram of MnO2@ZIF-67 to ascorbic acid in the embodiment;

[0028] Figure 6 The specific response of copper MnO2@ZIF-67 to reduced glutathione in the example

[0029] Figure 7The specific response of copper MnO2@ZIF-67 to cysteine ​​in the embodiment

[0030] Figure 8 This is a graph showing the total antioxidant capacity of copper MnO2@ZIF-67 on drug-resistant cells and drug-sensitive cells in the examples;

[0031] Figure 9 This is a graph showing the total antioxidant capacity of MnO2@ZIF-67 on senescent cells in the example.

[0032] Figure 10 This is a test diagram of the total antioxidant capacity of MnO2@ZIF-67 on VC in slowing down cellular aging in the example. DETAILED DESCRIPTION

[0033] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present application belongs.

[0034] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0035] The present invention will be further described with reference to specific examples. The following examples are intended only to illustrate the present invention and are not intended to limit its contents. Experimental conditions not specified in the examples are generally based on conventional conditions or those recommended by the sales company. Materials and reagents used in the examples are commercially available unless otherwise specified.

[0036] So far, there are many methods for detecting cellular antioxidants, each of which has its advantages and disadvantages and scope of application. For example, high-performance liquid chromatography, electrochemical-based analysis, electron spin resonance, spectrophotometry-based methods, including colorimetry, fluorescence, etc. However, due to their low availability, their widespread application is mostly limited. Therefore, the design and development of new, reliable, and efficient antioxidant screening platforms are necessary for clinical, industrial, and regulatory agencies. Among them, the most commonly used is biological kit detection, which is relatively expensive, and some kits may not be easy to obtain. In addition, the performance of different kits may vary and need to be selected with caution. The use of peroxidase-like nanozymes to detect antioxidants uses unstable H2O2, resulting in the inability to provide a more reliable output signal.

[0037] Because the aforementioned methods are complex and difficult to obtain, it is crucial to synthesize a nanomaterial with oxidase activity and create a platform for detecting cellular antioxidant capacity. This nanoenzyme detection platform can reveal the patterns of different physiological and pathological phenomena in cells through differences in antioxidant levels.

[0038] In one embodiment of the present invention, a method for preparing MnO2@ZIF-67 composite nanoparticles with high oxidase activity is provided, the preparation method comprising: Synthesis of S1 and MnO2

[0039] (1.1) adding the potassium permanganate aqueous solution to the cerium nitrate aqueous solution and stirring to obtain a uniformly mixed solution I;

[0040] (1.2) Nitric acid is added to the mixed solution I, stirred evenly, and subjected to a hydrothermal reaction to prepare MnO2. The addition of nitric acid can promote the occurrence of the oxidation reaction.

[0041] Synthesis of S2, MnO2@ZIF-67

[0042] (2.1) MnO2 and PVP (polyvinyl pyrrolidone) obtained in step S1 are added to a methanol solution and subjected to ultrasonic treatment to obtain a mixed solution II. PVP has good compatibility with a variety of solvents and can be coated on the particle surface through steric hindrance, forming a good dispersion effect. In addition, PVP can act as a surfactant during the synthesis of nanomaterials to prevent the aggregation of nanoparticles, thereby maintaining the excellent performance of the nanomaterials. (2.2) Adding cobalt nitrate hexahydrate to mixed solution II to obtain mixed solution III; (2.3) Adding 2-methylimidazole to mixed solution III to obtain mixed solution IV; wherein 2-methylimidazole acts as a ligand during the synthesis process and forms a zeolitic imidazole ester framework material ZIF-67 having a periodic network structure and a three-dimensional framework through coordination bonds with cobalt ions; (2.4) Finally, the mixed solution IV was allowed to stand overnight to obtain MnO2@ZIF-67.

[0043] In step (1.1), 0.002-0.008 mol of potassium permanganate aqueous solution is dissolved in 35 mL of water; 0.001-0.002 mol of cerium nitrate aqueous solution is dissolved in 35 mL of water as a hexahydrate. Preferably, the optimal concentration of the potassium permanganate aqueous solution is 0.006 mol / 35 mL, and the optimal concentration of the cerium nitrate aqueous solution is 0.0017 mol / 35 mL.

[0044] In step (1.2), the volume of nitric acid added is 4 mL; the temperature of the hydrothermal reaction is 100-180°C, and the reaction time is 2-5 hours. Preferably, the optimal conditions for the hydrothermal reaction are 140°C and 3 hours.

[0045] In step (2.1), methanol solution was used as the solvent, the mass ratio of PVP added to MnO2 was 6:1, and the ultrasonic treatment time was 30 minutes.

[0046] In step (2.2), the added mass of cobalt nitrate hexahydrate is 1.095 g, and in step (2.3), the added mass of 2-methylimidazole is 2.463 g.

[0047] In step (2.4), the overnight standing time is 10-16 hours, preferably 14 hours.

[0048] In another specific embodiment of the present invention, MnO2@ZIF-67 composite nanoparticles prepared by the above-mentioned preparation method are provided, which have optimized simulated oxidase activity, wherein ZIF-67 has no oxidase activity, and the synthesized MnO2@ZIF-67 composite nanoparticles significantly improve the oxidase activity of MnO2. By calculating the maximum reaction rate, it was found that the oxidase activity was increased by 20%.

[0049] In another embodiment of the present invention, the prepared MnO2@ZIF-67 composite nanoparticles are used to catalyze the oxidation of 1,3,3,5,5-tetramethylbenzidine (TMB) with O2. The MnO2@ZIF-67 composite nanoparticles are added to an acetate buffer containing TMB, and then the reaction is carried out. By incubating the nanoparticles with TMB, the absorbance change at 652 nm, based on the TMB redox color reaction, is used to detect reducing substances.

[0050] In another specific embodiment of the present invention, the prepared MnO2@ZIF-67 composite nanoparticles are applied to a colorimetric sensor. The colorimetric sensor at least includes the above-mentioned MnO2@ZIF-67 composite nanoparticles with high oxidase activity. The colorimetric sensor can further be used for the detection of reducing substances.

[0051] In another embodiment of the present invention, the prepared MnO2@ZIF-67 composite nanoparticles are used to test the antioxidant capacity of substances. This includes qualitative analysis of antioxidant substances, specifically, by measuring changes in absorbance at 652 nm; lower absorbance indicates higher total antioxidant capacity. Furthermore, antioxidant capacity is compared by measuring the absorbance of the reaction between MnO2@ZIF-67 and TMB and calculating the consumed substrate concentration.

[0052] In another embodiment of the present invention, a colorimetric sensor comprising the prepared MnO2@ZIF-67 composite nanoparticles or MnO2@ZIF-67 composite nanoparticles with high oxidase activity is used to measure the antioxidant capacity of cells. Specifically, the MnO2@ZIF-67 and / or colorimetric sensor containing MnO2@ZIF-67 is placed in cells for detection using a colorimetric method.

[0053] In another specific embodiment of the present invention, the prepared MnO2@ZIF-67 composite nanoparticles are used in a kit for detecting antioxidant capacity based on colorimetric sensing technology. The kit contains reagent a: MnO2@ZIF-67 (30 μg / mL), reagent b: 200 μL HAc-NaAc buffer solution, reagent c: TMB (0.2 mM), and the reaction time is incubation for 5 minutes.

[0054] This kit is typically used to detect antioxidant small molecules. The assay method is as follows: Different concentrations of ascorbic acid (AA) are mixed with MnO2@ZIF-67 (30 μg / mL) in 200 μL of HAc-NaAc buffer. TMB (0.2 mM) is added and incubated for 5 minutes. The absorbance of ox-TMB at 652 nm is monitored. The total antioxidant capacity can then be accurately calculated. The analytical procedures for cysteine ​​(Cys) and glutathione (GSH) are identical to those for ascorbic acid (AA).

[0055] In another specific embodiment of the present invention, the prepared MnO2@ZIF-67 composite nanoparticles are used in the screening of anti-aging drugs.

[0056] The present invention, based on the oxidase-like activity of MnO2-doped ZIF-67 (MnO2@ZIF-67), catalyzes TMB to produce ox-TMB, causing the solution to change from colorless to blue. ox-TMB has an absorption peak at 652 nm. Glutathione, ascorbic acid, and cysteine, as antioxidants, inhibit the redox reaction catalyzed by MnO2@ZIF-67, causing the solution to change from blue to colorless and resulting in a decrease in absorbance. Based on this, a standard curve is established, enabling quantitative detection of antioxidants. The system constructed using this method is stable, has low environmental sensitivity, a rapid response, a wide detection range, a low detection limit, and strong specificity, providing new methodological experience for the detection of antioxidants.

[0057] The technical effects of the present invention are further verified and explained below in conjunction with specific experimental measurements.

[0058] [Example]

[0059] First, prepare the manganese and cobalt composite material: Synthesis of S1 and MnO2

[0060] (1) Add 0.006 mol, 35 mL of potassium permanganate aqueous solution to 0.0017 mol, 35 mL of cerium nitrate aqueous solution and stir for 10 minutes.

[0061] (2) Add 4 mL of nitric acid solution to the mixed solution in step (1) and stir for 5.0 minutes.

[0062] (3) The mixed solution in step (2) was placed in a reactor at a reaction temperature of 140°C and a reaction time of 3 hours to obtain manganese dioxide (MnO2).

[0063] Synthesis of S2, MnO2@ZIF-67 composite nanoparticles

[0064] (1) Dissolve 50 mg of MnO2 and 300 mg of PVP in 30 mL of methanol and sonicate for 30 minutes.

[0065] (2) Add 1.095 g of cerium nitrate hexahydrate to the mixed solution in step (4) above and stir for 150 minutes.

[0066] (3) Add 2.463 g of 2-methylimidazole to the mixed solution in step (5), stir for 30 minutes, and let it stand for 24 hours to obtain the final desired material, the morphology of which is as follows: Figure 1 shown.

[0067] 1. Characterization of MnO2@ZIF-67 composite nanoparticles: like Figure 1 As shown, combined with transmission electron microscopy (TEM), it was found that the nanomaterial exhibited a core / shell structure, and it was believed that the MnO2@ZIF-67 nanoparticles showed a structure in which ZIF-67 was a shell-wrapped MnO2. Combined with energy dispersive x-ray spectroscopy (EDS), as shown Figure 2 As shown, the mapping and line scan profiles of a single NP verified that the elements cobalt and manganese were enriched in the core and shell regions, respectively, further confirming the presence of cobalt and manganese. Figure 3 As shown in Figure 3, the Zeta potential shows that MnO2 is negatively charged, ZIF-67 is positively charged, and the MnO2@ZIF-67 composite nanoparticles are positively charged.

[0068] 2. Verification of oxidase-like activity of MnO2@ZIF-67 composite nanoparticles: Experimental system a: The catalytic reaction system consisted of acetate buffer (pH 5, 200 mM), the MnO2@ZIF-67 composite nanoparticles (30 μg / mL) obtained above, and the organic color developer TMB (0.2 mM). The reaction was then allowed to proceed at room temperature for 5 minutes, and the visible absorption spectrum in the 400-800 nm range was measured using a microplate reader.

[0069] In addition, a control experiment b was performed: the catalytic system included acetate buffer (pH 5, 200 mM) and MnO2@ZIF-67 (30 ug / mL). The other reaction conditions were the same as the above experimental system, and the absorbance was measured after 5 minutes.

[0070] Another control experiment c: No MnO2@ZIF-67 composite material was added to the catalytic reaction system, and the absorbance value was detected after 5 minutes of reaction under the same conditions as the above experimental system.

[0071] like Figure 4 As shown, experimental system a exhibits a distinct peak, indicating that the copper nanoclusters exhibit significant oxidase activity at pH 5. Control experiment b exhibits no distinct peak near 652 nm, indicating that no significant reaction would occur without the MnO2@ZIF-67 composite as a catalyst. Control experiment c also exhibits no distinct peak, indicating that the peak in experimental system a is not caused by a response of the material itself.

[0072] 3. Qualitative detection of antioxidants: Catalytic reaction system a contains an antioxidant (40 μM), MnO2@ZIF-67 (30 μg / mL), an organic color developer TMB (0.2 mM), and acetate buffer (pH 5, 200 mM). The reaction is carried out at room temperature for 5 minutes, and the color is observed.

[0073] Reaction system b does not contain antioxidants, and the other conditions are the same as the above experimental system. The color change is observed after the reaction for 5 minutes.

[0074] 4. Quantitative detection of antioxidants: The catalytic reaction system contains different concentrations of antioxidants (ascorbic acid, glutathione, cysteine), MnO2@ZIF-67 (30ug / mL), organic color developer TMB (0.2mM), and acetate buffer (pH 5, 200mM). The reaction is carried out at room temperature for 5 minutes and the color is observed. After 5 minutes of reaction at room temperature, the absorbance at 652nm is measured using a microplate reader and the working curves of each antioxidant are plotted. Figure 5 As shown, the linear range of ascorbic acid is 2.5-40 μM; Figure 6 As shown, the linear range of glutathione is 0.0625-45 μM; Figure 7As shown, the linear range for cysteine ​​is 0.015-25 μM.

[0075] In this example, the minimum detection limits of ascorbic acid, glutathione, and cysteine ​​were 912 nM, 13.5 nM, and 3.12 nM, respectively, indicating high sensitivity and low detection limits.

[0076] 5. Antioxidant capacity test; Qualitative detection of cellular antioxidant capacity under different physiological and pathological conditions: The overall antioxidant capacity of drug-resistant tumor cells and conventional tumor cells was detected. The catalytic reaction system contained different numbers of cells (MCF-7, MCF-7 drug-resistant cells, A549, A549 drug-resistant cells, 10*104-1604), MnO2@ZIF-67 (30ug / mL), organic color developer TMB (0.2 mM) and acetate buffer (pH 5, 200 mM). The reaction was carried out at room temperature for 5 minutes and the color was observed. After reacting at room temperature for 5 minutes, the absorbance at 652 nm was detected using an enzyme-labeled instrument. Figure 8 As shown, drug-resistant cells detected higher reduction.

[0077] Qualitative detection of the overall antioxidant capacity of senescent cells and normal cells: Similar to the above catalytic reaction system, human umbilical vein epithelial cells (HUVEC) were induced to age by hydrogen peroxide. After 5 minutes of reaction at room temperature, the absorbance at 652 nm was detected using a microplate reader. Figure 9 As shown in Figure 3, senescent cells exhibit lower total antioxidant capacity. This assay can be used to detect the total antioxidant capacity of cells under different physiological states.

[0078] 5. The TMB colorimetric detection platform based on MnO2@ZIF-67 oxidase is expected to be used for the screening of anti-aging drugs:

[0079] After treatment with vitamin C (VC), a known anti-aging small molecule compound, it showed increased antioxidant capacity. The catalytic reaction system contained senescent cells, senescent cells treated with VC (100 μM), MnO2@ZIF-67 (30 μg / mL), organic color developer TMB (0.2 mM), and acetate buffer (pH 5, 200 mM). The reaction was allowed to react at room temperature for 5 minutes and the color was observed. After 5 minutes of reaction at room temperature, the absorbance at 652 nm was measured using a microplate reader. Figure 9 、 Figure 10 As shown, senescent cells have lower reducing capacity, but after treatment with anti-aging drugs, their total antioxidant capacity is restored. This is expected to be used for screening anti-aging drugs.

[0080] The above embodiments are not limitations of the present invention, and the present invention is not limited to the above examples. Any changes, modifications, additions or substitutions made by technicians in this technical field within the scope of the technical solution of the present invention also fall within the scope of protection of the present invention.

Claims

1. A method for preparing MnO2@ZIF-67 composite nanoparticles with high oxidase activity, characterized in that the preparation method comprises the following steps: Synthesis of S1 and MnO2 1.1 Add potassium permanganate aqueous solution to cerium nitrate aqueous solution and stir to obtain a uniform mixed solution I; 1.2 Add nitric acid to the mixed solution I, stir evenly, and perform a hydrothermal reaction to prepare MnO2; Synthesis of S2, MnO2@ZIF-67 composite nanoparticles 2.1 Add the MnO2 and PVP obtained in S1 to the solvent and obtain a mixed solution II by ultrasonic treatment; 2.2 Add cobalt nitrate hexahydrate to mixed solution II and mix well to obtain mixed solution III; 2.3 Add 2-methylimidazole to mixed solution III and mix well to obtain mixed solution IV; 2.4 Let the mixed solution IV stand overnight to obtain MnO2@ZIF-67.

2. The method for preparing MnO2@ZIF-67 composite nanoparticles with high oxidase activity according to claim 1, characterized in that: In step 1.1, 0.002-0.008 mol of the potassium permanganate aqueous solution is dissolved in 35 mL of water; and 0.001-0.002 mol of the cerium nitrate aqueous solution is dissolved in 35 mL of water.

3. The method for preparing MnO2@ZIF-67 composite nanoparticles with high oxidase activity according to claim 2, characterized in that: The optimal concentration of the potassium permanganate aqueous solution is 0.006 mol / 35 mL, and the optimal concentration of the cerium nitrate aqueous solution is 0.0017 mol / 35 mL.

4. The method for preparing MnO2@ZIF-67 composite nanoparticles with high oxidase activity according to claim 1, characterized in that: In step 1.2, the added volume of nitric acid is 4 mL.

5. The method for preparing MnO2@ZIF-67 composite nanoparticles with high oxidase activity according to claim 1, characterized in that: The temperature of the hydrothermal reaction is 100-180° C., and the reaction time is 2-5 hours.

6. The method for preparing MnO2@ZIF-67 composite nanoparticles with high oxidase activity according to claim 1, characterized in that: In step 2.1, the solvent is methanol, and the mass ratio of the added amount of PVP to MnO2 is 6:

1.

7. The method for preparing MnO2@ZIF-67 composite nanoparticles with high oxidase activity according to claim 6, characterized in that: In step 2.1, the ultrasonic treatment time is 30 minutes; in step 2.4, the standing time is 10-16 hours.

8. A MnO2@ZIF-67 composite nanoparticle, characterized by: The nanoparticles are prepared by the method for preparing MnO2@ZIF-67 composite nanoparticles with high oxidase activity according to any one of claims 1 to 7.

9. A use of the MnO2@ZIF-67 composite nanoparticles according to claim 8, characterized in that: The MnO2@ZIF-67 composite nanoparticles are used to catalyze oxygen oxidation of TMB color development, or to detect the anti-aging and antioxidant capabilities of substances, or to a kit for detecting antioxidant capabilities based on colorimetric sensing technology, or to a colorimetric sensor for detecting reducing substances.

10. A use of the MnO2@ZIF-67 composite nanoparticles according to claim 8, characterized in that: The MnO2@ZIF-67 composite nanoparticles are used in the screening of anti-aging drugs.

Images