Preparation method and application of a pseudo-oxidase gold nanoparticle and an antibacterial hydrogel

Abstract

This invention discloses a method for preparing and applying oxidase-like gold nanoparticles and antibacterial hydrogels. The oxidase-like gold nanoparticles are prepared by the following steps: HAuCl4 solution is added to a sulfated polysaccharide solution and stirred thoroughly. The molar ratio of sulfated polysaccharide to gold ions is 1:10-50. The pH of the solution is adjusted to 2-8, and the solution is heated in a water bath at 90℃-120℃ for 15-30 min. After cooling to room temperature, oxidase-like gold nanoparticles (Fuc-AuNPs) are obtained. This invention uses fucoidan as a stabilizer and reducing agent to synthesize gold nanoparticles in situ on fucoidan. The gold nanoparticles exhibit oxidase-like properties and can catalyze the dissolution of oxygen to generate singlet reactive oxygen species. Fucoidan serves as a template for synthesizing gold nanozymes, and the unique reducing properties of fucoidan are utilized in a one-pot method to prepare the gold nanozymes, avoiding the introduction of reducing agents with safety risks.

Description

Technical fields:

[0001] This invention relates to the field of food preservation technology, specifically to a method for preparing and applying a pseudo-oxidase gold nanoparticle and an antibacterial hydrogel. Background technology:

[0002] Meat products are an important part of our daily diet, but they are highly susceptible to microbial contamination and spoilage during production, processing, and transportation. Adding antimicrobial materials to food contact packaging can delay spoilage and reduce foodborne illnesses caused by pathogens. This requires antimicrobial materials not only to inhibit microbial growth but also to ensure they do not easily induce drug resistance and possess high biosafety. Therefore, the demand for novel antimicrobial materials is increasing. Nanozymes, a subset of nanomaterials, possess enzyme-mimicking properties and have been extensively explored in antimicrobial and food safety applications. Compared to similar natural enzymes, nanozymes have many unique advantages, such as ease of synthesis, low cost, wide availability, and high tolerance to adverse environments. These nanozymes typically generate reactive oxygen species (ROS) to inhibit bacterial proliferation. However, the development of nanozymes for combating bacteria still faces many challenges. Currently, most reported antimicrobial nanozymes rely primarily on their peroxidase-like activity, specifically the ability to decompose hydrogen peroxide to generate ROS. Hydrogen peroxide not only requires exogenous addition but also, due to its volatility and redox properties, negatively impacts the quality of meat products. Nanozymes with peroxidase-like properties have certain limitations when used as antibacterial agents. Therefore, there is a need for nanozymes that can directly generate reactive oxygen species (ROS) from dissolved oxygen, mimicking the properties of oxidases. Furthermore, due to the inherently short lifespan and short diffusion distance of ROS, almost all nanozymes cannot effectively interact with bacteria, significantly reducing their bactericidal effect. Therefore, an effective carrier is needed to enhance the interaction between nanozymes and bacteria.

[0003] Hydrogels have attracted widespread attention in the field of bioscience due to their unique physicochemical properties. Hydrogels exhibit excellent biocompatibility, deformation resistance, and water retention. By adjusting the chemical composition of hydrogels and encapsulating different functional components, they can be used in a variety of applications. Therefore, hydrogels can not only serve as effective carriers for nanozymes but also as containers for capturing and restricting bacterial activity, thereby fully leveraging the antibacterial function of reactive oxygen species in nanozymes. Hydrogels possess great potential as antibacterial and preservative materials for fresh meat products.

[0004] Currently, driven by environmental demands and pressures, there is a rapid increase in interest in developing more renewable, sustainable, and functional carrier materials. Natural polymers typically possess highly modifiable surface chemistry and colloidal properties, endowing nanozymes with in-situ synthesis and high loading capacity, allowing them to accommodate various nanozymes for specific purposes. While recent research on nanomaterials has been extensive, nanoparticles such as silver, copper, and metal oxides, despite possessing certain antibacterial properties, exhibit some toxicity to humans and are unsuitable for use as antibacterial materials in food contact. Gold, an inert noble metal, is stable and does not readily decompose into ions, offering relatively higher safety.

[0005] Foodborne pathogens pose a major threat to human health, leading to a growing demand for meat products that slow food spoilage and reduce the risk of foodborne illnesses. Nanomaterials have attracted significant attention in the field of antibacterial applications, but their reactive oxygen species antibacterial mechanisms are hampered by instability in terms of action distance and duration. This problem urgently needs to be addressed. Summary of the Invention:

[0006] To overcome the aforementioned problems in the existing technology, this invention provides a method for preparing and applying pseudo-oxidase gold nanoparticles and antibacterial hydrogels. This invention uses the most common sulfated polysaccharide as a template for synthesizing gold nanozymes, and prepares gold nanozymes in a one-pot process. The hydrogel is formed through the cross-linking of oppositely charged sulfated polysaccharide and chitosan polymer, which enhances the adhesion to bacteria, shortens the action distance of gold nanozymes, and fully utilizes the active oxygen antibacterial mechanism. It has promising applications in the preservation of food, especially fresh meat products.

[0007] The first objective of this invention is to provide a pseudo-oxidase gold nanoparticle, which is prepared by the following steps: adding HAuCl4 solution to a sulfated polysaccharide solution and stirring thoroughly, with the molar ratio of sulfated polysaccharide to gold ions being 1:10-50, adjusting the pH of the solution to 2-8, heating it in a water bath at 90℃-120℃ for 15-30 min, and cooling it to room temperature to obtain pseudo-oxidase gold nanoparticles Fuc-AuNPs.

[0008] Preferably, the mass fraction of the sulfated polysaccharide solution is 1%-3%, and the sulfated polysaccharide is fucoidan.

[0009] Preferably, the final molar concentration of Au in the solution obtained after adding HAuCl4 solution and stirring thoroughly is 1-8 mM.

[0010] This invention utilizes fucoidan as a stabilizer and reducing agent to synthesize gold nanoparticles in situ on fucoidan. The gold nanoparticles exhibit oxidase-like properties, catalyzing the dissolution of oxygen to generate singlet reactive oxygen species. Fucoidan serves as a template for synthesizing gold nanozymes, and the unique reducing properties of fucoidan are employed in a one-pot method to prepare the gold nanozymes, avoiding the introduction of reducing agents with safety risks.

[0011] A second objective of this invention is to provide a method for preparing an antibacterial hydrogel, comprising the following steps:

[0012] (1) Dissolve tea saponin in pure water to prepare a 0.05-0.15M tea saponin solution. Add NaIO4 powder to the tea saponin solution to make the concentration of NaIO4 in the tea saponin solution 0.1-0.4M. Stir at 60℃-80℃ in the dark for 3.5-4.5h, then add ethylene glycol and stir to stop the oxidation reaction. Dialyze with deionized water for 36-60h, retain a molecular weight cutoff of 3000, and freeze dry to obtain oxidized tea saponin.

[0013] (2) Take the aforementioned pseudo-oxidase gold nanoparticles Fuc-AuNPs, add oxidized tea saponin, mix evenly with chitosan solution, and place in an ice water bath to form an antibacterial hydrogel.

[0014] This invention utilizes the electrostatic cross-linking of fucoidan and chitosan to construct a hydrogel via ultrasonication. The hydrogel traps bacteria and enhances the destructive effect of reactive oxygen species generated by gold nanoparticles on bacteria. This hydrogel effectively slows down the bacterial spoilage process in chilled meat.

[0015] Preferably, the specific steps of step (1) are as follows: after stirring at 60℃-80℃ in the dark for 3.5-4.5h, ethylene glycol is added and stirred to stop the oxidation reaction, and then dialyzed with deionized water for 36-60h.

[0016] Preferably, the mass ratio of the pseudo-oxidase gold nanoparticles Fuc-AuNPs to oxidized tea saponins in step (2) is 1:0.25-1.

[0017] Further preferred, the mass ratio of oxidized tea saponin to chitosan in step (2) is 0.1-0.4:1.

[0018] Preferably, the chitosan solution in step (2) has a mass fraction of 1%-3%.

[0019] The third objective of this invention is to protect the antibacterial hydrogel prepared by the above-described preparation method.

[0020] This invention also protects the application of the aforementioned antibacterial hydrogel in food preservation. Specifically, the food preservation refers to the preservation and preservation of fresh meat products.

[0021] Compared with existing technologies, this invention has the following advantages: The materials used in this invention have high biocompatibility. The gold nanozyme uses common fucoidan as a template and leverages the unique reducing properties of fucoidan to prepare the gold nanozyme in a one-pot process, avoiding the introduction of reducing agents with safety risks. This gold nanozyme possesses the properties of an oxidase, inducing the production of active singlet oxygen, and retains catalytic activity over a wide pH range from acidic to neutral, thus exhibiting a certain degree of antibacterial ability without requiring the addition of exogenous hydrogen peroxide as a substrate. The formation of a hydrogel through the cross-linking of fucoidan and chitosan polymers with opposite charges enhances bacterial adhesion, shortens the action distance of the gold nanozyme, and fully utilizes the active oxygen antibacterial mechanism. It shows promising application prospects in food quality preservation, especially for fresh meat products. Attached image description:

[0022] Figure 1 The images shown are TEM, UV, IR, and XRD images of the enzyme-like gold nanoparticles Fuc-AuNPs obtained in Example 1; where A, B, C, and D are TEM, UV, IR, and XRD images, respectively.

[0023] Figure 2 The hydrogel properties obtained in Example 3 are characterized as follows: A is the hydrogel prepared by ultrasonication of a mixed solution of Fuc-AuNPs (a pseudo-oxidase gold nanoparticles) and chitosan; B is the large deformation compression curve of the hydrogel; C is the TPA texture curve of the hydrogel; and D is the viscoelastic property of the hydrogel.

[0024] Figure 3 The thixotropic curve of the hydrogel obtained in Example 3 under alternating high and low stress is shown.

[0025] Figure 4 Characterization of the enzymatic properties of the gold nanoparticles with pseudo-oxidases obtained in Examples 1 and 2; wherein: A is the ability of Fuc-AuNPs to catalyze the TMB oxidation reaction in (a) pH 4.0 buffer and (b) pH 6.0 buffer; B is the ability of Fuc-AuNPs to catalyze the TMB oxidation reaction in buffers with different pH values; C is the TMB oxidation reaction catalyzed by Fuc-AuNPs with different gold contents; D is the Lineweaver-Burk plot of the TMB oxidation reaction rate catalyzed by Fuc-AuNPs in (a) pH 4.0 buffer and (b) pH 6.0 buffer versus TMB concentration;

[0026] Figure 5 The intermediate obtained in Example 1 for detecting the catalytic oxidation reaction of Fuc-AuNPs using a singlet oxygen probe includes (A) a DPBF probe and (B) an ABDA probe.

[0027] Figure 6The inhibitory effect of the enzyme-mimicking gold nanoparticles obtained in Example 3 on Escherichia coli and Staphylococcus aureus; wherein: Figure 6 A is a TEM image of the inhibited bacteria; Figure 6 B represents the effect of oxidase-like gold nanoparticles on bacterial growth curves; Figure 6 C represents the inhibition of bacterial growth by the hydrogel using the plate count method;

[0028] Figure 7 The changes in volatile basic nitrogen (TVB-N) and total bacterial count during storage of the hydrogel-coated chilled pork obtained in Example 3 and the control sample are shown in Figure 3. A represents the change in volatile basic nitrogen (TVB-N) and B represents the change in total bacterial count. Detailed implementation method:

[0029] The following embodiments are further illustrations of the present invention, but not limitations thereof.

[0030] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention. Unless otherwise specified, the experimental materials and reagents used herein are commercially available products conventionally available in this technical field.

[0031] A method for preparing an antibacterial hydrogel includes the following steps:

[0032] (1) Add HAuCl4 solution to sulfate polysaccharide solution and stir thoroughly. The molar ratio of sulfate polysaccharide to gold ions is 1:10-50. Adjust the pH to 2-8 using hydrochloric acid solution or sodium hydroxide solution. Heat it in a water bath at 90℃-120℃ for 15-30 min. After cooling to room temperature, you will get Fuc-AuNPs, which are pseudo-oxidase gold nanoparticles.

[0033] (2) Dissolve tea saponin in pure water to prepare a 0.05-0.15M tea saponin solution. Add NaIO4 powder to the tea saponin solution to make the concentration of NaIO4 in the tea saponin solution 0.1-0.4M. Stir at 60℃-80℃ in the dark for 3.5-4.5h, then add ethylene glycol and stir to stop the oxidation reaction. Dialyze with deionized water for 36-60h, retain a molecular weight cutoff of 3000, and freeze dry to obtain oxidized tea saponin.

[0034] (3) Take the pseudo-oxidase gold nanoparticles Fuc-AuNPs, add oxidized tea saponin, mix them evenly with chitosan solution, and place them in an ice water bath to form an antibacterial hydrogel.

[0035] In the following examples, the preferred method is to use a sulfated polysaccharide solution with a mass fraction of 1%-3%, and the sulfated polysaccharide is fucoidan. The molar concentration of the HAuCl4 solution is 10-40 mM.

[0036] In the following embodiments, preferably, the mass ratio of the pseudo-oxidase gold nanoparticles Fuc-AuNPs to oxidized tea saponin is 1:0.25-1, and the mass ratio of oxidized tea saponin to chitosan is 0.1-0.4:1. The mass fraction of the chitosan solution is 1%-3%.

[0037] Example 1

[0038] A method for preparing pseudo-oxidase gold nanoparticles includes the following steps: Take 10g of a 2% (w / w) fucoidan solution in a 20mL screw-top glass bottle, place it on a magnetic stirrer at 300rpm. Add 1mL of a 25mM HAuCl4 solution and stir thoroughly. Adjust the pH to 2-8 (specifically 2, 3, 4, 5, 6, 7, 8) with NaOH or HCl solution. Heat the solution in a 105℃ water bath for 20min, cool to room temperature, and set aside to obtain pseudo-oxidase gold nanoparticles. Prepare control samples using the same steps. The sample with added Au is designated Fuc-AuNPs, and the pure fucoidan sample is designated Fuc.

[0039] The following tests and characterizations were performed on the enzyme-mimicking gold nanoparticles.

[0040] 1. The prepared gold nanoparticle samples, which resembled oxidases, were freeze-dried and then subjected to TEM scanning, ultraviolet spectroscopy, infrared spectroscopy, and X-ray diffraction analysis to characterize the structure of the gold-based nanozymes. For example... Figure 1 As shown, Figure 1 TEM images of A show that AuNPs are anchored on the surface of fucoidan. Figure 1 The UV-Vis absorption spectrum of B shows a characteristic absorption peak of AuNPs at 520 nm, indicating that fucoidan effectively reduces AuNPs. Figure 1 The FTIR spectrum of C showed that a redox reaction occurred on the hydroxyl groups of fucoidan to generate Au, which then interacted with AuNPs through coordination of the sulfate groups. Figure 1 The XRD pattern of D shows the (111), (200) and (220) crystal planes specific to AuNPs.

[0041] 2. The reaction mechanism of Fuc-AuNPs was analyzed. 190 μL of Fuc-AuNPs was added to 10 μL of ABDA (0.4 mM) as a substrate (final ABDA concentration in the system was 0.02 mM), and the generation of singlet oxygen was measured using a microplate reader in wavelength scanning mode (300-600 nm). Similarly, 190 μL of Fuc-AuNPs was added to 10 μL of DPBF (0.1 mg / mL) as a substrate (final DPBF concentration in the system was 5 μg / mL), and the generation of singlet oxygen was measured using a microplate reader in wavelength scanning mode (300-600 nm). Figure 5 As shown, Figure 5 This study demonstrates the detection of intermediates in the Fuc-AuNPs-catalyzed TMB oxidation reaction using reactive oxygen species probes. Figure 5 A shows that the addition of Fuc-AuNPs causes a rapid decrease in the absorption intensity of DPBF near 410 nm. Figure 5 B shows that the addition of Fuc-AuNPs rapidly reduces the absorption intensity of ABDA near 400 nm. This indicates that Fuc-AuNPs induce the formation of singlet oxygen as a reaction intermediate.

[0042] Example 2

[0043] A method for preparing pseudo-oxidase gold nanoparticles includes the following steps: 10 g of a 2% (w / w) fucoidan solution is placed in a 20 mL screw-top glass bottle and placed on a magnetic stirrer at 300 rpm. 1 mL of a 10-40 mM HAuCl4 solution (final molar concentrations of 1, 2, 4, 6, and 8 mM) is added and stirred thoroughly. The pH is adjusted to 6 with HCl solution. The solution is heated in a water bath at 105 °C for 20 min, cooled to room temperature, and then used to obtain pseudo-oxidase gold nanoparticles (Fuc-AuNPs).

[0044] The activity of the pseudo-oxidase gold nanoparticles Fuc-AuNPs obtained in Examples 1 and 2 was characterized. 20 μL of Fuc-AuNPs prepared under different conditions were added to 160 μL of HAc-NaAc buffer (0.2 M, pH 3.2-6.8) and mixed thoroughly. Then, 20 μL of TMB (20 mM) was added as a substrate (the final TMB concentration in the system was 2 mM). The oxidase properties of the samples were determined using a microplate reader in wavelength scanning mode (400-900 nm).

[0045] Figure 4 A shows the results of Fuc-AuNPs prepared under different pH conditions in acidic buffer ( Figure 4 A(a)) and neutral buffer ( Figure 4 Both A(b) and B showed oxidase activity. Figure 4B shows that the oxidase-like activity of Fuc-AuNPs (pH6) decreases with increasing buffer pH, indicating that the oxidase properties of gold nanozymes are related to the environment in which the nanozymes are located. Figure 4 C shows that the absorbance of Fuc-AuNPs with different gold contents increases significantly at 652 nm, indicating that the oxidase properties of gold nanozymes are positively correlated with the gold content. Figure 4 D shows a Lineweaver-Burk plot of the rate of TMB oxidation catalyzed by Fuc-AuNPs (pH6) in pH 4.0 and pH 6.0 buffers as a function of TMB concentration. (pH 4.0 buffer: V) max =0.197 μM / s; k = 0.48 μM; pH 6.0 buffer: V max =0.220μM / s; k=7.18μM).

[0046] Example 3

[0047] A method for preparing an antibacterial hydrogel includes the following steps:

[0048] (1) Dissolve 1.2g of tea saponin in 10mL of pure water to prepare a 0.1M tea saponin solution. Add NaIO4 powder to the tea saponin solution to a final concentration of 0.2M. Stir at 70℃ in the dark for 4h, then add 2mL of ethylene glycol and stir for 30min to stop the oxidation reaction. Dialyze with deionized water for 48h (molecular weight cutoff 3000), freeze-dry and collect the powder to obtain oxidized tea saponin;

[0049] (2) Take 2g of the pseudo-oxidase gold nanoparticles Fuc-AuNPs (pH3-8) prepared in Example 1, add 25mg of oxidized tea saponin, mix with 5g of chitosan solution with a mass fraction of 2% by ultrasonication, and place in an ice water bath to form a hydrogel, thus forming an antibacterial hydrogel.

[0050] The hydrogel obtained in step (2) was subjected to large deformation compression tests, TPA tests, and rheological analysis to characterize its physical properties. Thixotropic experiments were conducted on the hydrogel obtained by adding oxidized tea saponin to the pseudo-oxidase gold nanoparticles Fuc-AuNPs (pH6) to analyze its self-healing ability. Figure 2 and Figure 3 As shown, Figure 2 The large deformation compression test of B shows that the hydrogel becomes harder and more brittle as the pH increases. Figure 2 TPA tests on C showed that the mechanical properties and compression recovery of the hydrogel increased with increasing pH within a 50% deformation range. Figure 2 D further characterized the properties of the hydrogel using rheology, (a) the hydrogel exhibits viscoelastic solid properties as pH increases; (b) the hydrogel exhibits viscoelastic behavior independent of frequency. Figure 3The thixotropic curves of the hydrogel under low and high stress are shown. The hydrogel exhibits self-healing properties due to the Schiff base crosslinking network formed between tea saponin and chitosan amino groups.

[0051] The effect of Fuc-AuNPs on bacterial growth curves was investigated. Staphylococcus aureus and Escherichia coli were added to their respective LB broth and nutrient broth liquid media and incubated on a shaker at 37°C for 24 hours. After incubation, 1 mL of each culture was transferred to centrifuge tubes, washed twice with sterile physiological saline, and reconstituted in sterile physiological saline. The OD600 value was measured. The bacterial suspension was diluted to OD600 = 0.65 and set aside. In a 96-well plate, 100 μL of Fuc-AuNPs was added to the first well and subsequently diluted using a 2 / 3 dilution method to different concentrations of Fuc-AuNPs. Then, 100 μL of broth medium was added. 20 μL of bacterial suspension (OD600 = 0.65) was added to each of the different concentrations of Fuc-AuNPs. The samples containing the bacterial suspension were incubated in a 37°C oven. Samples were removed at 4 h, 8 h, 12 h, 18 h, and 24 h, and the OD600 value was measured. The bacterial growth curves were recorded. TEM was used to observe the inhibitory effect of nanozymes on bacteria. Figure 6 TEM results for A showed that the growth of Escherichia coli was inhibited and its length was shortened; the cell membrane of Staphylococcus aureus was damaged and wrinkled. Figure 6 B shows that gold nanozymes exhibit a significant inhibitory effect on bacterial growth.

[0052] The antibacterial activity of the hydrogel was determined using the plate method. Approximately 0.438 g of hydrogel / physiological saline was placed in a 2 mL sterile centrifuge tube. 21.9 μL of a bacterial suspension (OD600 = 0.65) prepared with sterile physiological saline was added to the surface, and the tube was incubated at 37°C for 2 h. Subsequently, 1 mL of sterile physiological saline was added to each tube, and the hydrogel was pulverized and thoroughly mixed to resuspend all surviving bacteria. Finally, 10 μL of each sample was plated onto agar plates and incubated at 37°C for 24 h, and photographs were taken for recording the results. Figure 6 C shows a significant reduction in bacterial colonies on the plate, indicating that the hydrogel significantly enhances the antibacterial effect by capturing and restricting bacteria.

[0053] Hydrogels prepared using Fuc-AuNPs (pH 6) pseudo-oxidase gold nanoparticles were used for the preservation of meat products. Commercially available chilled lean pork was cut into two cubes (5cm × 5cm × 5cm), and the hydrogel was coated onto the surface of each cube. The cubes were then placed in a 4°C refrigerator, and the TVB-N values ​​and total bacterial counts were measured on days 0, 2, 4, 6, 9, and 10. Figure 7 The results show that the hydrogel coating on the surface of pork produces bactericidal and deoxygenating effects similar to oxidases, which allows the pork to maintain good quality for a long time.

[0054] Example 4

[0055] A method for preparing an antibacterial hydrogel includes the following steps:

[0056] (1) Add HAuCl4 solution with a molar concentration of 25 mM to a 1% fucose polysaccharide solution and stir thoroughly. The molar ratio of fucose polysaccharide to gold ions is 1:10. Adjust the pH of the solution to 6, heat it in a 90℃ water bath for 30 min, and cool it to room temperature to obtain pseudo-oxidase gold nanoparticles Fuc-AuNPs.

[0057] (2) Dissolve tea saponin in pure water to prepare a 0.05M tea saponin solution. Add NaIO4 powder to the tea saponin solution to make the NaIO4 concentration in the tea saponin solution 0.1M. Stir at 80℃ in the dark for 3.5h, then add ethylene glycol and stir to stop the oxidation reaction. Dialyze with deionized water for 36h, retain a molecular weight cutoff of 3000, and freeze dry to obtain oxidized tea saponin.

[0058] (3) Take the pseudo-oxidase gold nanoparticles Fuc-AuNPs, add oxidized tea saponin, and mix them evenly with a chitosan solution with a mass fraction of 1%. The mass ratio of pseudo-oxidase gold nanoparticles Fuc-AuNPs to oxidized tea saponin is 1:0.25, and the mass ratio of oxidized tea saponin to chitosan is 0.1:1. Place them in an ice water bath to form an antibacterial hydrogel.

[0059] Example 5

[0060] A method for preparing an antibacterial hydrogel includes the following steps:

[0061] (1) Add HAuCl4 solution with a molar concentration of 25mM to a 3% fucose polysaccharide solution and stir thoroughly. The molar ratio of fucose polysaccharide to gold ions is 1:50. Adjust the pH of the solution to 6, heat it in a 120℃ water bath for 15min, and cool it to room temperature to obtain pseudo-oxidase gold nanoparticles Fuc-AuNPs.

[0062] (2) Dissolve tea saponin in pure water to prepare a 0.15M tea saponin solution. Add NaIO4 powder to the tea saponin solution to make the concentration of NaIO4 in the tea saponin solution 0.4M. Stir at 60℃ in the dark for 4.5h, then add ethylene glycol and stir to stop the oxidation reaction. Dialyze with deionized water for 60h, the molecular weight cutoff is 3000, and freeze-dry to obtain oxidized tea saponin.

[0063] (3) Take the pseudo-oxidase gold nanoparticles Fuc-AuNPs, add oxidized tea saponin, and mix them evenly with a chitosan solution with a mass fraction of 3%. The mass ratio of pseudo-oxidase gold nanoparticles Fuc-AuNPs to oxidized tea saponin is 1:1, and the mass ratio of oxidized tea saponin to chitosan is 0.4:1. Place them in an ice water bath to form an antibacterial hydrogel.

[0064] The above description of the embodiments is only for the purpose of helping to understand the technical solution and core idea of ​​the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing an antibacterial hydrogel, characterized in that, Includes the following steps: (1) Dissolve tea saponin in pure water to prepare a 0.05-0.15 M tea saponin solution. Add NaIO4 powder to the tea saponin solution to make the concentration of NaIO4 in the tea saponin solution 0.1-0.4 M. Stir at 60℃-80℃ in the dark for 3.5-4.5 h, then add ethylene glycol and stir to stop the oxidation reaction. Dialyze with deionized water for 36-60 h, retain a molecular weight cutoff of 3000, and freeze dry to obtain oxidized tea saponin. (2) Take the pseudo-oxidase gold nanoparticles Fuc-AuNPs, add oxidized tea saponin, mix them evenly with chitosan solution, and place them in an ice water bath to form an antibacterial hydrogel; The simulated oxidase gold nanoparticles were prepared by the following steps: HAuCl4 solution was added to a sulfated polysaccharide solution and stirred thoroughly. The molar ratio of sulfated polysaccharide to gold ions was 1:10-50. The pH of the solution was adjusted to 2-8. The solution was heated in a water bath at 90℃-120℃ for 15-30 min and cooled to room temperature to obtain simulated oxidase gold nanoparticles Fuc-AuNPs.

2. The preparation method according to claim 1, characterized in that, The mass fraction of the sulfated polysaccharide solution is 1%-3%, and the sulfated polysaccharide is fucoidan.

3. The preparation method according to claim 1, characterized in that, The specific steps of step (1) are as follows: after stirring at 60℃-80℃ in the dark for 3.5-4.5 h, ethylene glycol is added and stirred to stop the oxidation reaction, and then dialyzed with deionized water for 36-60 h.

4. The preparation method according to claim 1, characterized in that, The mass ratio of the pseudo-oxidase gold nanoparticles Fuc-AuNPs to oxidized tea saponins in step (2) is 1:0.25-1.

5. The preparation method according to claim 4, characterized in that, The mass ratio of oxidized tea saponin to chitosan in step (2) is 0.1-0.4:

1.

6. The preparation method according to claim 1, characterized in that, The chitosan solution in step (2) has a mass fraction of 1%-3%.

7. The antibacterial hydrogel prepared by the preparation method according to claim 1.

8. The application of the antibacterial hydrogel according to claim 7 in food preservation.

9. The application according to claim 8, characterized in that, The food preservation mentioned above specifically refers to the preservation and anti-corrosion of fresh meat products.

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