A biomimetic nanoenzyme material and its synthesis and application

Abstract

This invention belongs to the field of biomimetic nanomaterials technology, specifically providing a method for synthesizing biomimetic nanoenzymes and their application in antibacterial, anti-mold, and preservation of fruits and vegetables. The synthesis of the biomimetic nanoenzyme includes the following steps: (1) adding glutamic acid to deionized water and heating and stirring until a transparent or homogeneous glutamic acid solution is formed; (2) adding zinc sulfate and cerium sulfate to deionized water and ultrasonically dispersing them uniformly to obtain a bimetallic salt solution; (3) adding the bimetallic salt solution to the glutamic acid solution according to a molar ratio of zinc in zinc sulfate, cerium in cerium sulfate, and glutamic acid of 3~4:0.5~0.9:1, followed by the addition of an organic solvent, stirring under heating conditions, and then washing, drying, and grinding to obtain the biomimetic nanoenzyme. Experiments show that the biomimetic nanoenzyme Zn of this invention… 3.5 / Ce 0.9 -Glu has a bactericidal rate of 99.41% against Escherichia coli and 98.28% against Staphylococcus aureus, which can extend the storage period of cherry tomatoes to 12 days.

Description

Technical Field

[0001] This invention belongs to the field of biomimetic nanomaterials technology, specifically relating to a biomimetic nanoenzyme material, its synthesis, and its application in antibacterial, anti-mold, and preservation of fruits and vegetables. Background Technology

[0002] Even after harvesting, fruits and vegetables continue to undergo respiration and metabolism, resulting in the loss of internal moisture, acids, and sugars, leading to softening and spoilage. Microorganisms (fungi, bacteria, yeasts, etc.) invade through surface wounds, epidermal pores, or directly penetrate the epidermis, decomposing plant tissue to obtain nutrients, which is a key factor in their decay. Paper packaging materials have advantages such as being environmentally friendly and recyclable, automatically regulating moisture and breathable, low cost, and easy to use. However, they lack long-lasting antibacterial and anti-mold functions, limiting their practical application in extending the storage and shelf life of fruits and vegetables. Therefore, functional modification of fruit and vegetable packaging paper to create antibacterial paper-based preservation packaging materials is of great significance for eliminating or inhibiting microbial growth and extending the storage period of food.

[0003] Currently, antibacterial and anti-mold technologies for fruits and vegetables mainly include physical preservation, chemical fungicides, natural antibacterial agents, and organic / inorganic nanomaterials for preservation. Although chemical fungicides have strong antibacterial effects and low cost, long-term use can easily lead to problems such as pesticide residues, environmental pollution, and microbial resistance, making it difficult to meet the requirements of green and safe food. Physical preservation (low temperature, modified atmosphere, irradiation) has high energy consumption and large equipment investment, and some processing methods can easily damage the nutrition and flavor of fruits and vegetables. Natural antibacterial agents and organic / inorganic nanomaterials have the drawbacks of complex synthesis and high preparation costs, making them unsuitable for large-scale application in fruit and vegetable preservation. Summary of the Invention

[0004] The purpose of this invention is to provide a biomimetic nanoenzyme, its synthesis method, and its application. The biomimetic nanoenzyme possesses oxidase-like activity, effectively eliminating microorganisms in fruits and vegetables or inhibiting their reproduction rate. Simultaneously, it inhibits post-harvest oxidative aging of fruits and vegetables, achieving long-lasting antibacterial, anti-mold, and preservation effects, thereby extending the storage period of fruits and vegetables and expanding their sales radius.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] This invention first provides a method for synthesizing biomimetic nanozymes, which includes the following steps:

[0007] (1) Add glutamic acid to deionized water and heat and stir until a clear or homogeneous glutamic acid solution is formed;

[0008] (2) Add zinc sulfate and cerium sulfate to deionized water and sonicate to disperse them evenly to obtain a bimetallic salt solution;

[0009] (3) Add the bimetallic salt solution described in step (2) to the glutamic acid solution according to the molar ratio of zinc element in zinc sulfate, cerium element in cerium sulfate and glutamic acid of 3~4:0.5~0.9:1, then add organic solvent, stir under heating conditions, and after washing, drying and grinding, the biomimetic nanozyme is obtained.

[0010] Furthermore, in step (3), the molar ratio of zinc in zinc sulfate, cerium in cerium sulfate, and glutamic acid is 3.5:0.9:1.

[0011] Furthermore, the organic solvent in step (3) is one or more of dimethyl sulfoxide, dimethylformamide, and dimethylacetamide (which is beneficial for the deprotonation of amino acids); the volume fraction of the organic solvent in the mixed system (the mixed system refers to a mixture of glutamic acid solution, zinc sulfate, cerium sulfate and organic solvent) is 10% to 30%, preferably 20%.

[0012] Furthermore, the heating temperature in step (3) is 60℃~90℃, and the stirring time is 6~36h.

[0013] The present invention also provides a biomimetic nanozyme prepared by the above method.

[0014] The present invention also provides the application of the above-mentioned biomimetic nanoenzyme in the preparation of packaging materials for antibacterial, anti-mildew and freshness preservation of fruits and vegetables.

[0015] The present invention also provides a fruit and vegetable preservation paper, which includes a fruit and vegetable packaging paper substrate and an antibacterial coating loaded on the surface of the fruit and vegetable packaging paper substrate, wherein the antibacterial coating contains the above-mentioned biomimetic nanoenzyme.

[0016] Furthermore, the antibacterial coating is formed by spraying an antibacterial spray liquid onto a fruit and vegetable packaging paper substrate; the antibacterial spray liquid includes the biomimetic nanoenzyme, starch adhesive, and pure water; the mass fraction of the biomimetic nanoenzyme in the antibacterial spray liquid is 2.5% to 5.0%.

[0017] The present invention also provides an antibacterial agent comprising the above-mentioned biomimetic nanoenzyme as an active ingredient.

[0018] Furthermore, the antibacterial agent is used to inhibit Escherichia coli and / or Staphylococcus aureus.

[0019] The beneficial effects of this invention are as follows:

[0020] This invention achieves precise control over the framework structure, pore environment, and functional properties of Zn / Ce-Glu biomimetic nanozymes by coordinating and polymerizing bimetallic zinc and cerium with glutamic acid in a specific ratio. The resulting biomimetic nanozyme exhibits excellent antibacterial, antifungal, and preservative effects. Experiments show that the biomimetic nanozyme Zn...3.5 / Ce 0.9 -Glu not only has a high yield, but also has a bactericidal rate of 99.41% against E. coli and 98.28% against Staphylococcus aureus. At the same time, it can produce H2O2 and has high oxidase-like activity, which can extend the storage period of cherry tomatoes to 12 days.

[0021] Furthermore, the biomimetic nanoenzyme raw material composition and preparation method described in this invention are simple, and the antibacterial, anti-mildew and freshness preservation functions are achieved by loading paper-based packaging materials, which helps to reduce direct residues on the fruit surface and the difficulty of batch control, and has good market application prospects in the anti-mildew and freshness preservation of fruits and vegetables. Attached Figure Description

[0022] Figure 1 SEM and TEM images of different biomimetic nanozymes prepared in Example 1 are shown below. Figure 1 (a~d) represent Zn 3.5 -Glu、Zn 3.5 / Ce 0.5 -Glu、Zn 3.5 / Ce 0.9 -Glu、Zn 3.5 / Ce 1.5 -SEM image of Glu Figure 1 (e~h) represent Ce 0.9 -Glu, Zn3 / Ce 0.9 -Glu、Zn 3.5 / Ce 0.9 -Glu, Zn4 / Ce 0.9 -SEM image of Glu Figure 1 (i~l) represent Zn 3.5 / Ce 0.9 -TEM images of Glu at different magnifications.

[0023] Figure 2 When detecting the concentration of metal elements in different biomimetic nanozymes prepared in Example 1 using ICP-OES, the concentration of metal elements in these nanozymes was determined. Figure 2 (a) is Zn 3.5 -Glu、Zn 3.5 / Ce 0.5 -Glu、Zn 3.5 / Ce 0.9 -Glu、Zn 3.5 / Ce 1.5 -Concentration of metal elements in Glu Figure 2 (b) is

[0024] Ce 0.9 -Glu, Zn3 / Ce0.9 -Glu、Zn 3.5 / Ce 0.9 -Glu, Zn4 / Ce 0.9 - The concentration of the metal element in Glu.

[0025] Figure 3 XRD patterns of different biomimetic nanozymes prepared in Example 1, wherein, Figure 3 (a) Zn 3.5 -Glu、Zn 3.5 / Ce 0.5 -Glu、Zn 3.5 / Ce 0.9 -Glu、Zn 3.5 / Ce 1.5 -XRD pattern of Glu; Figure 3 (b) Ce 0.9 -Glu, Zn3 / Ce 0.9 -Glu、Zn 3.5 / Ce 0.9 -Glu, Zn4 / Ce 0.9 XRD pattern of Glu.

[0026] Figure 4 This is from Example 3, the cherry tomato preservation experiment, showing the rate of decay over time for different treatment groups of cherry tomatoes during storage.

[0027] Figure 5 Zn 3.5 / Ce 0.9 -Results of Glu free radical quenching experiments. Detailed Implementation

[0028] Example 1: Preparation and Characterization of Biomimetic Nanozymes

[0029] The preparation of the biomimetic nanozyme in this embodiment is carried out according to the following steps:

[0030] (1) Add amino acids to deionized water and heat and stir at 80℃~90℃ until a transparent liquid is formed to obtain an amino acid solution;

[0031] (2) Add the metal salt to deionized water and sonicate it to disperse it evenly to obtain a metal salt solution;

[0032] (3) Add the metal salt solution to the amino acid solution according to the preset molar ratio of the amino acid and the metal element in the metal salt, and then add the organic solvent N,N-dimethylacetamide, dimethyl sulfoxide or dimethylformamide (the volume fraction of the organic solvent in the mixed system is 10% to 30%). Stir at 60℃ to 90℃ for 6 to 36 hours, and after washing, drying and grinding, the biomimetic nanozyme is obtained.

[0033] The specific biomimetic nanoenzymes obtained are as follows:

[0034] Zn 3.5 -Glu, Ce 0.9 -Glu、Zn 3.5 / Ce 0.5 -Glu、Zn 3.5 / Ce 0.9 -Glu、Zn 3.5 / Ce 1.5 -Glu、Zn 3.5 / Ce 2.0 -Glu, Zn3 / Ce 0.9 -Glu、Zn 3.5 / Ce 0.9 -Glu、Zn 4.0 / Ce 0.9 -Glu、Zn 4.5 / Ce 0.9 -Glu、Zn 3.5 / Cu 0.9 -His、Zn 4.5 / Cu 0.9 -His、Fe 3.5 / Mn 0.9 -Asp、Fe 3.5 / Mn 2.0 -Asp、Zn 3.5 / Fe 0.9 -Lys、Zn 4.0 / Fe 0.9 -Lys.

[0035] Among them, Zn 3.5 -Glu represents the amino acid glutamic acid in step (1) and the metal salt zinc sulfate in step (2). The biomimetic nanozyme is obtained by mixing the glutamic acid solution and the zinc sulfate solution at a zinc to Glu molar ratio of 3.5:1; Zn 3.5 / Ce 0.5 -Glu represents that the amino acid in step (1) is glutamic acid, and the metal salt in step (2) is zinc sulfate and cerium sulfate. The glutamic acid solution is mixed with the mixed solution of zinc sulfate and cerium sulfate according to the molar ratio of zinc element, cerium element and glutamic acid of 3.5:0.5:1 to obtain the biomimetic nanozyme.

[0036] With Zn 3.5 / Ce 0.9 Taking Glu as an example, its preparation method is as follows:

[0037] (1) Add glutamic acid to deionized water and heat and stir at 85°C until a transparent liquid is formed to obtain a glutamic acid solution;

[0038] (2) Add zinc sulfate and cerium sulfate to deionized water and sonicate to disperse them evenly to obtain a bimetallic salt solution;

[0039] (3) According to the ratio of zinc element in zinc sulfate: cerium element in cerium sulfate: glutamic acid molar ratio of 3.5:0.9:1, add bimetallic salt solution to glutamic acid solution, then add organic solvent dimethyl sulfoxide (dimethyl sulfoxide volume fraction in the mixed system is 20%), stir at 80℃ for 24h, and after washing, drying and grinding, biomimetic nanozyme is obtained.

[0040] The microstructure, elemental distribution, metal concentration, crystal structure, and catalytic performance of the above-mentioned biomimetic nanozymes were characterized and analyzed by SEM, TEM, XRD, and ICP-OES.

[0041] 1. Scanning Electron Microscope (SEM)

[0042] The morphology and structure of the biomimetic nanozyme were observed using SEM. During sample preparation, conductive tape was used to attach the samples to the sample stage, and a high-pressure gas cylinder was used to purge excess sample to prevent it from falling off during testing. After 3 minutes of gold sputtering, SEM scanning was performed at 10 kV in SEM mode.

[0043] Figure 1 (a) Display Zn 3.5 -Glu has a clear structural outline, a smooth surface, and varies in size, exhibiting columnar or blocky structures, with material sizes ranging from 1 to 20 μm. Figure 1 (e) Display Ce 0.9 -Glu exhibits a porous and loose overall structure with no obvious crystal morphology. Combined with the 10µm scale, the particle size should be at the nanometer level. Figure 1 (b~d, f~h) represent the morphologies of Zn / Ce-Glu with different doping ratios, and their overall characteristics are similar to those of Ce. 0.9 -Similar to Glu. This indicates that Zn 3.5 -Glu doping with Ce will tend to favor Ce. 0.9 -The morphology of Glu is completely inconsistent with the original columnar and massive structure; while Ce 0.9 -The morphology of Glu did not change after doping with Zn. This may be due to Ce. 3+ Its ionic radius (10³ pm) is greater than that of Zn. 2+ (74 pm), and has a higher charge, resulting in stronger coordination ability with amino acid ligands (Ce 3+ The hard acid properties of amino acids are a better match for the hard base coordination sites of amino acids, such as carboxyl and amino groups.

[0044] 2. Transmission electron microscope (TEM)

[0045] TEM can be used to study the microstructure, particle morphology, and size distribution of biomimetic nanozymes. To prepare the test sample, it is dispersed in anhydrous ethanol and then sonicated to ensure uniform dispersion. A suitable amount of the sample dispersion is then dropped onto the surface of a copper mesh. After the sample has dried, TEM testing can be performed.

[0046] Figure 1 (i~l) is a biomimetic nanozyme Zn 3.5 / Ce 0.9 TEM images of Glu in the range of 10–500 nm show irregularly aggregated nanomaterials at scale 10 nm, while at scales 100 nm and 50 nm, individual irregular, bone-like structures with interconnected neck regions are clearly visible. This indicates that the biomimetic nanozyme Zn 3.5 / Ce 0.9 In Glu, Zn and Ce successfully coordinated with glutamic acid to form an irregular, bone-like nanoscale antibacterial agent.

[0047] 3. Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES)

[0048] Sample pretreatment before digestion: Weigh 0.01 g of biomimetic nanozyme powder sample into a 10 mL brown test tube, add 0.5 mL of nitric acid to dissolve it completely, and bring the volume to 10 mL. Filter the liquid using a disposable 0.22 μm filter tip. Prepare eight standard working solutions with concentrations of 0, 10, 25, 50, 75, 100, 150, and 200 μg / mL. Plot standard curves for Zn and Ce based on the instrument's response signals. Determine the contents of Zn and Ce sequentially using ICP-OES.

[0049] like Figure 2 As shown in (a), the Zn concentration decreases with increasing Ce concentration, indicating that Ce and Zn compete for coordination with D-glutamic acid. When the Zn / Ce molar ratio is low, Ce... 3+ It will preferentially occupy the major coordination sites of amino acids, Zn 2+ It can only function as an auxiliary ligand or fill lattice voids; when the Zn / Ce molar ratio is high, a large amount of Zn... 2+ Will with Ce 3+ Competing coordination sites may lead to mixed coordination structures. For example... Figure 2 (b) In the Ce series group, Zn 3.5 / Ce 0.9 -Glu is the inflection point, that is, when the molar ratio of Zn to Ce is 3.5:0.9, the Zn concentration first increases and then decreases, and the Ce concentration first decreases and then increases.

[0050] 4. X-ray diffraction (XRD)

[0051] XRD can help understand Zn. 3.5 -Glu, Ce 0.9 -Glu and Zn / Ce-Glu crystal structures. Before testing, the samples need to be dried and ground. The tests are conducted under Cu-Ka radiation (λ=0.154 nm), with a range of 5° to 80° and a scan step size of 5° / min. Different samples yield different characteristic peaks. The sharper the XRD diffraction peak, the better the crystallinity. If a bulging peak appears, it indicates poor crystallinity.

[0052] from Figure 3 (a) It can be seen that Zn 3.5 The XRD diffraction pattern of Glu-zinc shows a high degree of match between the diffraction peaks and relative intensities of the standard card for zinc glutamate, indicating good crystallinity and a single phase. With increasing Ce doping concentration, the diffraction peak intensity of glutamate-zinc gradually decreases, exhibiting a distinct peak envelopment in the 5°–10° range. This change suggests that Ce incorporation leads to a decrease in the crystallinity of glutamate-zinc, possibly forming a Ce-based phase. 3+ Zn is a mononuclear complex centered on Zn. 2+ It exists as a counter ion.

[0053] from Figure 3 (b) It can be seen that Ce 0.9 The XRD diffraction pattern of Glu shows a distinct peak in the 5°–10° range, and a slight, inconspicuous low-intensity peak in the 20°–30° range, indicating poor crystallinity of the material. Even after doping Ce-series elements with Zn, a peak still appears in the 5°–10° range, indicating Zn³⁺ / Ce⁻ 0.9 -Glu、Zn 3.5 / Ce 0.9 -Glu, Zn4 / Ce 0.9 -Glu also generates zinc glutamate, and with increasing Zn doping concentration, the zinc content increases. 3.5 / Ce 0.9 -Glu is used as the boundary, and some of its diffraction peaks are significantly stronger than those of Zn3 / Ce. 0.9 -Glu and Zn4 / Ce 0.9 -Glu indicates that the material reaches its optimal crystallinity when the molar ratio of Zn to Ce is 3.5:0.9. Too high or too low Zn ratio will affect the growth of the material's crystal phase.

[0054] Comparative Example 1

[0055] This comparative example provides the preparation methods for different ionic amino acid complexes as follows:

[0056] (1) Add amino acids to deionized water and heat to dissolve until a transparent liquid is obtained, thus obtaining an amino acid solution;

[0057] (2) Add metal A salt and metal B salt to deionized water respectively, and sonicate them to disperse them evenly to obtain a bimetallic salt solution;

[0058] (3) Add a bimetallic salt solution to the amino acid solution according to the molar ratio of metal A: metal B: amino acid of 3.5:0.9:1, then add 20% acetic acid to the mixture, stir at 60℃~90℃ for 6~36h, and then wash, dry and grind.

[0059] The materials prepared according to the method in this comparative example are denoted as: Zn 3.5 / Ce 0.9 -Glu acid treatment, Zn 3.5 / Cu 0.9 -His acid treatment, Fe 3.5 / Mn 0.9 -Asp acid treatment or Zn 3.5 / Fe 0.9 -Lys acid treatment.

[0060] Comparative Example 2

[0061] This comparative example provides Zn 3.5 / Ce 0.9 The preparation method of Glu (ethanol) is as follows:

[0062] (1) Add glutamic acid to deionized water and heat to dissolve until a clear liquid is obtained, thus obtaining a glutamic acid solution;

[0063] (2) Add zinc sulfate and cerium sulfate to deionized water and sonicate to disperse them evenly to obtain a bimetallic salt solution;

[0064] (3) Add the bimetallic salt solution obtained in step (2) to the glutamic acid solution according to the molar ratio of zinc:cerium:glutamic acid 3.5:0.9:1, then add 20% ethanol to the mixture, stir at 60℃~90℃ for 6~36h, wash, dry and grind, and record the obtained material as Zn 3.5 / Ce 0.9 -Glu (ethanol).

[0065] Example 2 Quantitative sterilization experiment

[0066] This embodiment tests the bactericidal properties of Example 1, Comparative Example 1, Comparative Example 2, and either amino acid or metal solution alone. Specific experiments were conducted according to the "Disinfection Technical Specifications 2002" for antibacterial effect testing, including the following steps:

[0067] (1) Sterilization of items: Place test tubes, disposable pipette tips, diluent, neutralizing agent, nutrient agar and other items required for the experiment into an autoclave and sterilize them at 121℃ and 103kPa for later use.

[0068] (2) Preparation of bacterial suspension: Add a certain amount of deionized water to the test tube, scrape bacteria that have been cultured at 37°C for 18-24 hours from the petri dish using a disposable inoculation loop and inoculate them into the test tube. Mix them in an electric vortex mixer and use a turbidity meter to measure the turbidity, ensuring that the concentration of the bacterial suspension in the test tube is 10. 6 CFU / mL.

[0069] (3) Reaction of bacterial suspension with antibacterial agent: Different test materials prepared in Example 1 and Comparative Examples 1-2 were added to deionized water to prepare antibacterial agents of different concentrations (wherein, the concentration of metal ions in the metal solution alone was 1.2 mmol / L; the concentration of amino acids in the amino acid solution alone was 0.3%; the concentration of different biomimetic nanozymes or ionic amino acid complexes was 0.3%), and then 1 ml of bacterial suspension (Escherichia coli and Staphylococcus aureus bacterial suspensions respectively) was added and mixed thoroughly. The reaction was timed for a certain period of time. Several sterilized test tubes were placed on a test tube rack. The first tubes of the blank group and the sample group (10 -1 Add 9 mL of neutralizing agent to each tube, and add 9 mL of sterile diluent to the remaining tubes. Label the tubes 10 from left to right. -1 10 -2 10 -3 10 -4 10 -5 10 -6 The blank group was configured with 6 dilution gradients (10-10). -1 ~10 -6 The sample group was set with 5 dilution gradients (10). -1 ~10 -5 ).

[0070] (4) Neutralizing agent termination stage: After the bacterial solution and antibacterial agent have interacted for 10 min, take 1 mL of the mixture and add it to the first gradient, let it mix thoroughly and interact for 10 min.

[0071] (5) Incubation stage: Perform 10-fold serial dilutions and inject 1 mL of each serial dilution into a disposable sterile culture dish. Then pour in about 15 mL of nutrient agar, mix the dilutions with the agar, wait for it to solidify, and then place it in a 37℃ constant temperature and humidity incubator for 24 h. Observe and record the experimental results.

[0072] (6) Calculation of sterilization rate:

[0073] ;

[0074] In the formula: X: sterilization rate; A: total bacterial count (CFU) of the control group (i.e., without any antibacterial agent); B: total bacterial count (CFU) of the experimental group.

[0075] (7) Yield calculation: Product mass (the product mass is based on solid product because it is required for the preparation of fruit and vegetable preservation paper) / (amino acid addition amount + metal salt addition amount) × 100%.

[0076] Table 1. Yields of different materials and their bactericidal rates against Escherichia coli and Staphylococcus aureus

[0077]

[0078] Example 3: Cherry Tomato Preservation Experiment

[0079] Purchase 360 ​​fresh cherry tomatoes of uniform color and quality with undamaged skin, and divide them into 5 groups of 72 tomatoes each. Perform the following different treatments:

[0080] (1) Blank: The fruit is not wrapped in any paper.

[0081] (2) Absorbent paper: Untreated absorbent paper used to wrap fruit;

[0082] (3) Adhesive absorbent paper treatment: Mix starch adhesive with pure water (the mass fraction of starch adhesive in the mixture is 10%), spray the mixture onto absorbent paper, and after drying, use it to package fruit;

[0083] (4) Zn 3.5 / Ce 0.9 -Glu-2.5% treatment: The Zn prepared in Example 1 3.5 / Ce 0.9 -Glu is mixed with starch adhesive and pure water, and the mixture is sprayed onto absorbent paper. After drying, it is used for packaging fruit; wherein, in the mixture, Zn 3.5 / Ce 0.9 -Glu mass fraction is 2.5%, starch adhesive mass fraction is 10%;

[0084] (5) Zn 3.5 / Ce 0.9 -Glu-5% treatment: The Zn prepared in Example 1 was subjected to... 3.5 / Ce 0.9 -Glu is mixed with starch adhesive and pure water, and the mixture is sprayed onto absorbent paper. After drying, it is used for packaging fruit; wherein, in the mixture, Zn 3.5 / Ce 0.9 -Glu content is 5% by mass, and starch adhesive content is 10% by mass.

[0085] The packaging paper for different treatments was used to cover the cherry tomatoes in two layers. Five groups of fruit samples under different treatment conditions were placed in a constant temperature and humidity incubator and stored in an environment with a temperature of 25℃ and a humidity of 55±5%.

[0086] Rot rate test:

[0087] In the experiment to determine the rot rate, the rot of cherry tomatoes was measured in 3-day cycles. Rot was defined as juice leakage, wrinkled skin, browning, mold growth, and cracking. The rot rate was negatively correlated with the preservation effect of cherry tomatoes; a higher rot rate resulted in poorer preservation, while a lower rot rate resulted in better preservation. The rot rate of cherry tomatoes was calculated using the following formula: Rot rate (%) = (Number of rotten fruits / Total number of fruits) × 100%.

[0088] The results are as follows Figure 4 As shown, Zn 3.5 / Ce 0.9 Cherry tomatoes preserved with -Glu -5% fruit and vegetable preservation paper exhibit the lowest rate of rotting and significantly extend their storage period from 6 days to 12 days, demonstrating excellent preservation effects.

[0089] Example 4: Biomimetic nanozymes with different Zn / Ce ratios (Zn) x / Ce y - Glu-type oxidase activity verification experiment

[0090] To explore biomimetic nanozymes with different Zn / Ce ratios x / Ce y - To investigate the catalytic activity of Glu and the main reactive oxygen species (ROS) generated during catalysis, this study employed a typical quencher capture experiment, the specific procedures of which are as follows:

[0091] 1. Correspondence between quenchers and ROS

[0092] The following enzymes were selected: catalase (CAT, which quenches H2O2), p-benzoquinone (BQ, which quenches superoxide anion•O2-), and L-histidine (L-His, which quenches singlet oxygen). 1 O2) and thiourea (TU, which quenches hydroxyl radicals •OH) are typical ROS quenchers.

[0093] 2. Reaction system setup

[0094] With each material (Zn) 3.5 -Glu、Zn 3.0 Ce 0.9 -Glu、Zn 3.5 Ce 0.5 -Glu、Zn 3.5 Ce 0.9 -Glu、Zn 3.5 Ce 1.5 -Glu、Zn 4.0 Ce 0.9 -Glu, Ce 0.9-Glu) Construct an oxidase-like catalytic reaction system and set up two control groups:

[0095] Blank control group: No quencher was added to the reaction system;

[0096] Quenching experimental group: The above-mentioned quenching agents were added to the reaction system respectively, and the catalytic reaction was carried out under the same conditions.

[0097] 3. Activity detection methods

[0098] The oxidase-like activity of the material was evaluated using the TMB colorimetric method. The absorbance of the system was measured at a wavelength of 652 nm, and the absorbance value was used to represent the amount of ox-TMB generated, which indirectly reflects the relative catalytic activity of the material.

[0099] As shown in Table 2, the quencher experiment results indicate that the single-component Zn-Glu and Ce-Glu materials have almost no oxidase-like activity, while the combination of Zn and Ce can significantly enhance the ROS generation capacity, and Zn... 3.5 Ce 0.9 -Glu exhibits optimal activity, indicating a significant synergistic effect between Zn and Ce, which can enhance the oxidase-like catalytic performance of the material by promoting the generation of reactive oxygen species such as •O2-, •OH and H2O2.

[0100] Table 2 Zn x Ce y -Absorbance of Glu with different free radical quenchers

[0101]

[0102] Example 5: Biomimetic Nanoenzyme Zn 3.5 / Ce 0.9 - Glu-type oxidase activity verification experiment

[0103] This embodiment systematically evaluates the biomimetic nanozyme Zn prepared in Example 1 using a combination of TMB oxidation colorimetric reaction and free radical quenching experiment. 3.5 / Ce 0.9 - Investigate the oxidase-like activity of Glu materials and identify the types of reactive oxygen species (ROS) that play a key role in the sterilization process.

[0104] 1. Zn 3.5 / Ce 0.9 Preliminary validation of Glu-type oxidase activity

[0105] The Zn prepared in Example 1 3.5 / Ce 0.9 - Dissolve Glu powder in an aqueous solution to prepare a 3‰ sample solution. Take an appropriate amount of Zn 3.5 / Ce 0.9-Glu sample solution was placed in a centrifuge tube, and 0.4 mL of 40 mM TMB solution (without H2O2) was added. The mixture was vortexed and reacted for 15 min. The color change of the solution was observed. Subsequently, the UV-Vis spectrophotometer was used to measure the UV characteristic absorption peak of the solution at a wavelength of 652 nm, and the absorbance value was recorded.

[0106] Zn under neutral conditions 3.5 / Ce 0.9 -Glu can oxidize colorless 3,3',5,5'-tetramethylbenzidine (TMB) to blue oxTMB, and a distinct UV characteristic absorption peak appears at 652 nm on a UV-Vis spectrophotometer, indicating that Zn 3.5 / Ce 0.9 -Glu itself can generate H2O2 and oxidize colorless TMB into blue oxTMB, confirming that the material has oxidase-like activity.

[0107] 2. Investigation of ROS types (free radical quenching experiment):

[0108] Take several centrifuge tubes and add equal amounts of 3‰ Zn to each. 3.5 / Ce 0.9 For each group of Glu sample solutions, add 0.4 mL of 40 mM TMB solution. Add 0.4 mL of the corresponding free radical quencher to each centrifuge tube: Group 1: catalase (quenches H2O2); Group 2: p-benzoquinone (PBQ) (quenches O2•-); Group 3: L-histidine (L-His) (quenches free radicals). 1 The fourth group added thiourea (quenching •OH), with a final concentration of 5 mM for all free radical quenchers (excluding catalase). A control group without any added quenchers was set up. All centrifuge tubes were vortexed for 15 min. After the reaction, the reaction solution was filtered using a disposable syringe with a 0.22 μm nylon 66 filter to remove impurities. The absorbance of each solution at 652 nm was then quickly measured using UV-Vis. Each experiment was repeated three times, and the average value was taken as the final experimental data.

[0109] Based on the changes in absorbance values ​​of each group, the relative activity of different ROS was calculated (using the absorbance value of the blank control group as a benchmark, the percentage decrease in absorbance after the addition of the quencher was calculated; the higher the percentage decrease, the stronger the relative activity of the ROS).

[0110] like Figure 5As shown, with the addition of various free radical quenchers (catalase, PBQ, Thiourea), the relative activities of H2O2, O2•-, and •OH all decreased significantly; while with the addition of L-His, 1 The relative activity of O2 decreased only slightly, and the decrease was much smaller than that of the other three ROS.

[0111] The above experimental results show that Zn 3.5 / Ce 0.9 -Glu materials possess oxidase-like activity, capable of generating H₂O₂ to oxidize TMB to oxTMB, thus achieving the colorimetric oxidation of TMB. H₂O₂, O₂•⁻, and •OH, the three ROS, play a major role in the sterilization process. 1 O2 contributes relatively little to the sterilization process.

[0112] The above description is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention. All components not explicitly stated in this embodiment can be implemented using existing technology.

Claims

1. A method for synthesizing biomimetic nanozymes, characterized in that, Includes the following steps: (1) Add glutamic acid to deionized water and heat and stir until a clear or homogeneous glutamic acid solution is formed; (2) Add zinc sulfate and cerium sulfate to deionized water and sonicate to disperse them evenly to obtain a bimetallic salt solution; (3) Add the bimetallic salt solution described in step (2) to the glutamic acid solution according to the molar ratio of zinc element in zinc sulfate, cerium element in cerium sulfate and glutamic acid of 3~4:0.5~0.9:1, then add organic solvent, stir under heating conditions, and after washing, drying and grinding, the biomimetic nanozyme is obtained.

2. The synthesis method according to claim 1, characterized in that, In step (3), the molar ratio of zinc in zinc sulfate, cerium in cerium sulfate, and glutamic acid is 3.5:0.9:

1.

3. The synthesis method according to claim 1, characterized in that, The organic solvent in step (3) is one or more of dimethyl sulfoxide, dimethylformamide, and dimethylacetamide; the volume fraction of the organic solvent in the mixed system is 10% to 30%.

4. The synthesis method according to claim 1, characterized in that, The heating temperature in step (3) is 60℃~90℃, and the stirring time is 6~36h.

5. A biomimetic nanoenzyme, characterized in that, The biomimetic nanozyme is synthesized by the method described in any one of claims 1 to 4.

6. The application of the biomimetic nanoenzyme according to claim 5 in the preparation of packaging materials for antibacterial, anti-mildew and preservation of fruits and vegetables.

7. A fruit and vegetable preservation paper, characterized in that, It includes a fruit and vegetable packaging paper substrate and an antibacterial coating loaded on the surface of the fruit and vegetable packaging paper substrate, wherein the antibacterial coating contains the biomimetic nanoenzyme as described in claim 5.

8. The fruit and vegetable preservation paper according to claim 7, characterized in that, The antibacterial coating is formed by spraying an antibacterial spray liquid onto a fruit and vegetable packaging paper substrate; the antibacterial spray liquid includes biomimetic nanoenzymes, starch adhesives, and pure water; the mass fraction of the biomimetic nanoenzymes in the antibacterial spray liquid is 2.5% to 5.0%.

9. An antibacterial agent, characterized in that, The antibacterial agent comprises the biomimetic nanozyme of claim 5 as an active ingredient.

10. The use of the antibacterial agent according to claim 9 in inhibiting Escherichia coli and / or Staphylococcus aureus.

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