Intelligent biomimetic hydrogel and preparation method and application thereof

Abstract

The application discloses intelligent bionic hydrogel and a preparation method and application thereof, and belongs to the technical field of nanobiological materials and food preservation. The intelligent bionic hydrogel comprises the following raw materials in parts by weight: polyvinyl alcohol 4-5 parts, cationic chitosan 0.4-0.5 parts, glycerol 0.4-0.6 parts and water 20-22 parts, and further comprises a two-dimensional V2C MXene nanosheet water dispersion liquid; the preparation method comprises the following steps: (1) weighing the raw materials; (2) preparing a polyvinyl alcohol solution; (3) adding glycerol and cationic chitosan, and then adding the two-dimensional V2C MXene nanosheet, and uniformly stirring; and (4) freezing-thawing treatment, and the intelligent bionic hydrogel is obtained. The application realizes deep decoupling and cooperation of physical anti-water loss and chemical sterilization, exhibits excellent efficacy in postharvest preservation of fruits (such as cherries and citrus), effectively prolongs a high-quality shelf life, reduces a weight loss rate and strictly guarantees microbial safety.

Description

Technical Field

[0001] This invention relates to the field of nanobiomaterials and food preservation technology, and more specifically to an intelligent biomimetic hydrogel, its preparation method and application. Background Technology

[0002] Postharvest spoilage of fresh fruit (especially high-moisture, perishable berries) is a core pain point that exacerbates global food waste, and is usually driven by irreversible physiological water loss and exogenous pathogenic microbial infection.

[0003] Currently, traditional physical barrier coatings (such as edible films based on polysaccharides or proteins) lack sufficient stress dissipation capacity and cannot adapt to the dynamic volume shrinkage of live fruits during storage due to respiration and moisture evaporation. This makes them highly susceptible to developing microcracks invisible to the naked eye, leading to the failure of the moisture barrier and opening channels for opportunistic pathogens to invade. To compensate for the vulnerability of physical defenses, traditional active packaging often introduces releasing antimicrobial agents such as essential oils or metal ions. However, this leads to the dilemma of rapid depletion of antimicrobial agents resulting in insufficient long-term preservation capabilities and uncontrolled migration posing serious toxicity risks.

[0004] In recent years, emerging nanozymes with excellent stability have provided a new perspective for antimicrobial packaging of food. However, their catalytic sterilization mechanism usually relies on a continuous supply of exogenous hydrogen peroxide (H2O2) as a substrate. Artificially adding chemical oxidants to the surface of fresh food not only seriously violates the clean labeling trend and safety regulations of the modern food industry, but also triggers systemic oxidative stress, thereby accelerating the physiological aging of fruit tissues.

[0005] Therefore, how to construct a protective system that can both flexibly adapt to the shrinkage of fruit volume and intelligently activate the nanozyme chemical immune system without the need for exogenous chemical reagents is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] In view of this, the purpose of this invention is to provide a smart biomimetic hydrogel, its preparation method and application, in order to overcome the shortcomings of the prior art.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A smart biomimetic hydrogel comprises the following raw materials in parts by weight: 4-5 parts polyvinyl alcohol (PVA), 0.4-0.5 parts cationic chitosan (CC), 0.4-0.6 parts glycerol, and 20-22 parts water (H2O); It also includes a two-dimensional V2C MXene nanosheet aqueous dispersion; the amount of the two-dimensional V2C MXene nanosheet aqueous dispersion added is such that the mass fraction of the two-dimensional V2C MXene nanosheets in the final hydrogel system is 3%-5%.

[0009] Furthermore, the aforementioned intelligent biomimetic hydrogel comprises the following raw materials in parts by weight: 4.05 parts polyvinyl alcohol, 0.45 parts cationic chitosan, 0.5 parts glycerol, and 20.2 parts water; It also includes an aqueous dispersion of two-dimensional V2C MXene nanosheets; the amount of the aqueous dispersion of two-dimensional V2C MXene nanosheets added is such that the mass fraction of two-dimensional V2C MXene nanosheets in the final hydrogel system is 4%.

[0010] In this invention, the hydrogel possesses an interpenetrating polymer network structure. Polyvinyl alcohol (PVA) and cationic chitosan are bonded through electrostatic crosslinking. Glycerol forms a competitive hydrogen-bonded network within the hydrogel. The two-dimensional V2C MXene nanosheets are monolayer nanosheets with oxygen-containing functional groups on their surface, which crosslink with PVA and cationic chitosan via hydrogen bonds; simultaneously, the two-dimensional V2C MXene nanosheets exhibit peroxidase-like activity. Ultimately, the two-dimensional V2C MXene nanosheets are anchored within a dynamic polymer network composed of PVA, cationic chitosan, and glycerol.

[0011] The glycerol-driven hydrogen bond network in the hydrogel of this invention endows the coating with dynamic morphological adaptability, enabling it to seamlessly conform to the shrinkage of fruit to lock in moisture and eliminate microcracks; the two-dimensional V2C MXene nanosheets capture trace amounts of endogenous substances produced by the metabolism of pathogenic microorganisms in situ, triggering a local reactive oxygen species storm to achieve sterilization.

[0012] The innovative aspects of this invention are as follows: 1. Traditional rigid coatings based on polysaccharides or proteins are prone to microcracks when fruit shrinks, leading to moisture loss and opening channels for pathogen invasion. To address this issue, this invention utilizes the strong electrostatic crosslinking between PVA and CC to give the hydrogel matrix excellent dynamic morphological adaptability, ensuring that the coating adheres seamlessly during the continuous shrinkage of the fruit, remaining dense and free of microcracks.

[0013] 2. The intelligent biomimetic hydrogel of this invention contains glycerol. The introduction of glycerol establishes a robust anti-water loss barrier through a competitive hydrogen bonding mechanism. The numerous hydroxyl groups in its molecule form stable hydrogen bonds with free water molecules, firmly locking water within the three-dimensional framework of the polymer, fundamentally blocking the pathway of internal water loss and constructing a flexible physical armor.

[0014] 3. The intelligent biomimetic hydrogel of this invention contains a two-dimensional V2C MXene nanosheet composite system. Traditional active packaging typically adds release-type antibacterial agents such as essential oils or metal ions, which are not only easily depleted quickly, but their uncontrolled penetration into the fruit pulp can also lead to the risk of toxic migration. Emerging nanosheet sterilization methods usually rely on a continuous artificial supply of exogenous hydrogen peroxide, which seriously violates food safety regulations and accelerates fruit senescence. For this reason, this invention uses V2C monolayer nanosheets with excellent peroxidase-like activity as the core nanosheet engine, achieving highly efficient self-driven sterilization without any external chemical additions.

[0015] 4. Two-dimensional V2C MXene nanosheets are confined and anchored within a three-dimensional porous hydrogel framework microenvironment. The three-dimensional porous framework of the hydrogel acts as a micro-concentrator, providing a unique microenvironmental confinement effect for the nanosheets. Here, the V2C MXene nanosheets function as a smart biochemical radar, sensitively capturing trace amounts of endogenous hydrogen peroxide secreted by pathogenic microorganisms during metabolism or when fruit is slightly damaged, triggering a highly localized reactive oxygen species (ROS) lethal storm in situ. This heterogeneous microenvironment design significantly enhances the hydrogel's chemoimmunization performance against pathogens.

[0016] Furthermore, the specific method for preparing the above-mentioned two-dimensional V2C MXene nanosheet aqueous dispersion is as follows: (1) Etching reaction V2AlC powder was added to an aqueous solution of hydrofluoric acid and magnetically stirred to carry out an etching reaction to selectively remove the aluminum layer. (2) Cleaning and drying After the reaction was completed, the precipitate was collected by centrifugation and washing, dried, and ground to obtain layered V2C powder. (3) Intercalation stripping Layered V2C powder was dispersed in an aqueous solution of tripropylammonium hydroxide, and intercalation and exfoliation were performed by magnetic stirring at room temperature. After centrifugation and washing, the supernatant was collected to obtain a two-dimensional V2C MXene nanosheet aqueous dispersion.

[0017] The further beneficial effect of the above-mentioned method is that the V2C MXene nanosheets prepared by the chemical exfoliation method of the present invention contain abundant oxygen-containing hydrophilic functional groups on their surface, which provides core anchoring points for constructing a strong competitive hydrogen bond network.

[0018] Furthermore, in step (1) above, the mass fraction of hydrofluoric acid aqueous solution is 50%; the ratio of V2AlC powder to hydrofluoric acid aqueous solution is 1 g: 30 mL; the temperature of magnetic stirring is 55℃ and the time is 72 h.

[0019] Furthermore, in step (2) above, the centrifugal washing speed is 8000 r / min, the time is 5 min, until the pH value of the supernatant stabilizes at 7.0; the drying equipment is a vacuum oven, the temperature is 60℃, and the time is 12h.

[0020] Furthermore, in step (3) above, the mass fraction of the tripropylammonium hydroxide aqueous solution is 5%; the ratio of layered V2C powder to tripropylammonium hydroxide aqueous solution is 1 g: 10 mL; and the magnetic stirring time is 24 h.

[0021] A method for preparing a smart biomimetic hydrogel specifically includes the following steps: (1) Weigh each raw material according to the above-mentioned proportions of intelligent biomimetic hydrogel; (2) Disperse polyvinyl alcohol in water and stir to dissolve it to obtain a polyvinyl alcohol solution; (3) Glycerol and cationic chitosan were added to the polyvinyl alcohol solution in sequence, followed by the addition of two-dimensional V2C MXene nanosheet aqueous dispersion, and stirred evenly to obtain a mixture; (4) The mixture is subjected to freeze-thaw treatment to obtain the intelligent biomimetic hydrogel.

[0022] Furthermore, in step (2) above, the temperature for stirring and dissolving is 80°C.

[0023] Furthermore, in step (4) above, the conditions for the freeze-thaw process are: first freeze at -20℃ for 12 hours, and then thaw at 25℃ for 2 hours.

[0024] The further beneficial effect of adopting the above-mentioned method is that the freeze-thaw physical cross-linking method is not only simple and environmentally friendly, but also avoids the introduction of toxic chemical cross-linking agents, ensuring that the intelligent biomimetic hydrogel fully meets the safety requirements of food-grade contact materials while maintaining high mechanical toughness and catalytic activity.

[0025] This invention also claims protection for the application of the above-described intelligent biomimetic hydrogel or the intelligent biomimetic hydrogel prepared by the above-described method in the preparation of a postharvest fresh fruit preservation coating.

[0026] This invention also claims protection for the application of the above-described intelligent biomimetic hydrogel or the intelligent biomimetic hydrogel prepared by the above-described method in the preparation of self-driven antibacterial materials.

[0027] As can be seen from the above technical solution, compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention designs a microenvironment-responsive smart biomimetic hydrogel driven by two-dimensional V2C MXene nanosheets. First, two-dimensional V2C MXene nanosheets are prepared by hydrofluoric acid etching and intercalation exfoliation. Then, the smart biomimetic hydrogel is obtained through physical mixing and freeze-thaw cycle process. It can be applied to self-driven antibacterial and post-harvest preservation of fruits under conditions without the addition of exogenous chemical reagents.

[0028] 2. On a macroscopic level, the glycerol-driven hydrogen bond network endows the hydrogel's surface with dynamic morphological adaptability, enabling it to seamlessly conform to the fruit's contraction to lock in moisture and eliminate microcracks that lead to bacterial invasion. On a microscopic level, the two-dimensional V2C MXene nanosheets act as a smart biochemical radar, capturing trace amounts of endogenous substances produced by pathogenic microorganisms' metabolism. This triggers a localized, lethal reactive oxygen species storm without the addition of exogenous chemicals, achieving self-driven antibacterial action. This invention achieves deep decoupling and synergy between physical water loss prevention and chemical sterilization, demonstrating outstanding efficacy in postharvest preservation of fruits (such as cherries and citrus), effectively extending high-quality shelf life, reducing weight loss, and strictly ensuring microbial safety, providing a new paradigm for next-generation green and intelligent food packaging.

[0029] 3. The hydrogel of this invention successfully achieves self-driven antibacterial activity against Escherichia coli and Staphylococcus aureus through a dual physical-chemical defense mechanism, and exhibits excellent 9-day preservation effects on perishable fruits such as cherries and citrus fruits. This invention not only successfully achieves deep decoupling and synergy between physical water retention and chemical sterilization, but also provides a pioneering practical blueprint for developing a new generation of green packaging for fresh agricultural products that is leached-free and has zero chemical additives.

[0030] 4. This invention develops a smart biomimetic hydrogel composed of two-dimensional V2C MXene nanosheets and an interpenetrating polymer network for efficient, additive-free fruit preservation. This significant performance improvement stems from the perfect synergy between the structural carrier and the nanosheet engine. The polymer network provides excellent dynamic morphological adaptability and a physical barrier against water loss, while the constrained two-dimensional V2C MXene nanosheets precisely execute in-situ ROS-based bactericidal chemoimmunization based on endogenous substrates. When applied to highly perishable cherries and citrus fruits, this hydrogel successfully achieved excellent preservation for up to 9 days, perfectly maintaining the visual freshness of the fruit and minimizing weight loss, while strictly limiting the total surface bacterial count to within safe edible thresholds. This work overcomes the mechanical defects of traditional preservation films and the challenges of antimicrobial agent depletion / toxic migration, providing a transformative example for developing next-generation smart food packaging with zero chemical additives and for sustainable postharvest agricultural development. Attached Figure Description

[0031] Figure 1The images show the synthesis, morphological evolution, and structural characterization of the two-dimensional V2C MXene nanosheets in Example 1; where (a) is a SEM image of V2AlC powder; (b) is a SEM image of the two-dimensional V2C MXene nanosheets; (c) is a TEM image of the two-dimensional V2C MXene nanosheets; (d) is an HRTEM image of the two-dimensional V2C MXene nanosheets; (e) is an XRD pattern of V2AlC powder and two-dimensional V2C MXene nanosheets; and (f) is a high-resolution XPS pattern of the V 2p region. Figure 2 The microstructure and properties of the hydrogels for each treatment are shown in the figure; (a) is the FTIR spectrum of each polymer system; (b) is the water retention (WR) curve of the smart biomimetic hydrogel; and (c) is the stress-strain curve of the smart biomimetic hydrogel. Figure 3 The graphs show the peroxidase-like activity analysis of hydrogels for each treatment; where (a) is the UV-vis absorption spectrum of each treated hydrogel; (b) and (c) are the K values ​​obtained from steady-state kinetic analysis and calculation for H2O2 and TMB substrates, respectively. m and V max picture; Figure 4 The images show the antibacterial activity tests of various treated hydrogels against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus; where (a) and (b) are digital photographs of Escherichia coli and Staphylococcus aureus colonies after incubation with different hydrogel samples, respectively; and (c) and (d) are the quantitative antibacterial rates of Escherichia coli and Staphylococcus aureus calculated by plate counting, respectively. Figure 5 The figures show the preservation performance of fruits treated with different hydrogels; (a) and (b) are photos of the appearance changes of cherries and citrus fruits throughout the entire shelf life; (c) and (d) are the weight loss curves of cherries and citrus fruits; (e) and (f) are the total bacterial count (TVC) change curves of cherries and citrus fruits. Detailed Implementation

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Example 1 Intelligent biomimetic hydrogel (P) 90 VC 10G), comprising the following raw materials by weight: 4.05 g polyvinyl alcohol, 0.45 g cationic chitosan, 0.5 g glycerol, and 20.2 mL water; and also comprising an aqueous dispersion of two-dimensional V2C MXene nanosheets, the amount of which is added such that the mass fraction of two-dimensional V2C MXene nanosheets in the final hydrogel system is 4%; The preparation method of the two-dimensional V2C MXene nanosheet dispersion (chemical etching combined with intercalation exfoliation) is as follows: (1) Etching reaction Weigh 1 g of V2AlC powder and slowly add it to 30 mL of 50% HF aqueous solution; place the mixture in a constant temperature water bath at 55℃ and stir magnetically for 72 h to selectively remove the Al atomic layer; (2) Cleaning and drying After the reaction was completed, the product was repeatedly centrifuged and washed with deionized water (8000 r / min, 5 min) until the pH of the supernatant stabilized at 7.0. The precipitate was collected and dried in a vacuum oven at 60℃ for 12 h. After grinding, layered V2C powder was obtained. (3) Intercalation stripping 1 g of layered V2C powder was dispersed in 10 mL of 5% TPAOH aqueous solution, and the intercalation was carried out by magnetic stirring at room temperature for 24 h. After centrifugation and washing, the supernatant was collected to finally obtain a stable two-dimensional V2C MXene nanosheet dispersion. The preparation method of the above-mentioned intelligent biomimetic hydrogel (physical mixing and freeze-thaw process) specifically includes the following steps: (1) Weigh each raw material according to the weight of the above-mentioned intelligent biomimetic hydrogel; (2) Add polyvinyl alcohol powder to deionized water and stir continuously at 80°C for 2 hours until completely dissolved to obtain a polyvinyl alcohol solution; (3) Add glycerol and cationic chitosan to the polyvinyl alcohol solution in sequence, followed by the addition of a two-dimensional V2C MXene nanosheet aqueous dispersion, so that the mass fraction of the two-dimensional V2C MXene nanosheets in the final hydrogel system is 4%. Stir magnetically until uniformly mixed to obtain a mixture. (4) Pour the mixture into a mold and freeze it at -20°C for 12 hours. Then thaw it at 25°C for 2 hours. A network structure is formed through physical cross-linking, thus obtaining the intelligent biomimetic hydrogel.

[0034] Example 2 Intelligent biomimetic hydrogel (P) 95VC5G includes the following raw materials by weight: 4.275 g polyvinyl alcohol, 0.225 g cationic chitosan, 0.5 g glycerol and 20.2 mL water; it also includes an aqueous dispersion of two-dimensional V2C MXene nanosheets, the amount of which is added so that the mass fraction of two-dimensional V2C MXene nanosheets in the final hydrogel system is 4%.

[0035] The only difference between this embodiment and Embodiment 1 is that the mass ratio of polyvinyl alcohol to cationic chitosan is 95:5, otherwise it is the same as Embodiment 1.

[0036] Example 3 Intelligent biomimetic hydrogel (P) 85 VC 15 G), comprising the following raw materials by weight: 3.825 g polyvinyl alcohol, 0.675 g cationic chitosan, 0.5 g glycerol and 20.2 mL water; and also comprising an aqueous dispersion of two-dimensional V2C MXene nanosheets, the amount of which is added such that the mass fraction of two-dimensional V2C MXene nanosheets in the final hydrogel system is 4%.

[0037] The only difference between this embodiment and Embodiment 1 is that the mass ratio of polyvinyl alcohol to cationic chitosan is 85:15; otherwise, they are the same as in Embodiment 1.

[0038] Example 4 Intelligent biomimetic hydrogel (P) 80 VC 20 G), comprising the following raw materials by weight: 3.6 g polyvinyl alcohol, 0.9 g cationic chitosan, 0.5 g glycerol and 20.2 mL water; and also comprising an aqueous dispersion of two-dimensional V2C MXene nanosheets, the amount of which is added such that the mass fraction of two-dimensional V2C MXene nanosheets in the final hydrogel system is 4%.

[0039] The only difference between this embodiment and Embodiment 1 is that the mass ratio of polyvinyl alcohol to cationic chitosan is 80:20; otherwise, they are the same as in Embodiment 1.

[0040] Comparative Example 1 PVA-H2O comprises the following raw materials by weight: 4.5g of polyvinyl alcohol and 20.2mL of water.

[0041] The only difference between this comparative example and Example 1 is that it does not contain cationic chitosan, glycerol, and two-dimensional V2C MXene nanosheets; otherwise, it is the same as Example 1.

[0042] Comparative Example 2 PG comprises the following ingredients by weight: 4.5g polyvinyl alcohol, 0.5g glycerin, and 20.2mL water.

[0043] The only difference between this comparative example and Example 1 is that it does not contain cationic chitosan and two-dimensional V2C MXene nanosheets; otherwise, it is the same as Example 1.

[0044] Comparative Example 3 PVG comprises the following raw materials by weight: 4.5 g polyvinyl alcohol, 0.5 g glycerol, and 20.2 mL water; it also includes an aqueous dispersion of two-dimensional V2C MXene nanosheets, the amount of which is added such that the mass fraction of two-dimensional V2C MXene nanosheets in the final hydrogel system is 4%. The only difference between this comparative example and Example 1 is that it does not contain cationic chitosan; otherwise, it is the same as Example 1.

[0045] Performance testing Take P obtained in Example 1 90 VC 10 G. P prepared in Example 2 95 VC5G, P prepared in Example 3 85 VC 15 G. P prepared in Example 4 80 VC 20 G, PVA-H2O prepared in Comparative Example 1, PG prepared in Comparative Example 2, and PVG prepared in Comparative Example 3 were subjected to the following performance tests.

[0046] 1. Synthesis, morphological evolution and structural characterization of two-dimensional V2C MXene nanosheets like Figure 1 As shown in (a)-(d), the V2AlC powder exhibits a dense, blocky morphology, which transforms into a typical accordion-like multilayer structure after etching. The exfoliated two-dimensional V2C MXene nanosheets appear as ultrathin sheets, and HRTEM shows that their lattice spacing is approximately 0.252 nm, corresponding to the (002) crystal plane. Figure 1 In the XRD pattern of (e), the (002) characteristic peak appears near 8° after etching, confirming the successful preparation of two-dimensional V2C MXene nanosheets. Figure 1 XPS spectra in (f) show the presence of VC and VO bonds, indicating that the surface of the two-dimensional V2C MXene nanosheets is rich in oxygen-containing functional groups.

[0047] 2. Microstructure and properties of hydrogels like Figure 2 The FTIR spectrum in (a) is shown at 3342 cm⁻¹. -1 The broad peak at 1000-1200 cm⁻¹ confirms the presence of a rich hydrogen bond network within the system. -1 The VO vibration peak appearing at this point indicates that V2C has been successfully crosslinked with the polymer matrix. For example... Figure 2As shown in (b), the water retention rate of the glycerol-containing hydrogel was significantly higher than that of the pure PVA gel. This is because glycerol forms a stable hydrogen bond water-locking barrier with water molecules. Figure 2 As shown in (c), the addition of cationic chitosan significantly improved the tensile strength and mechanical toughness of the hydrogel.

[0048] 3. Peroxidase-like activity analysis Each of the 3.6 g hydrogels was placed in a pH 4.0 buffer solution, and 1.0 mM TMB and 100 mM H2O2 were added. The mixture was then incubated at 37 °C for 10 min.

[0049] like Figure 3 As shown in (a), the V2C-containing hydrogel effectively catalyzes the oxidation of TMB to a blue product (maximum absorption peak at 652 nm), while the control group without V2C shows no color reaction. Figure 3 Figures (b) and (c) show that P 90 VC 10 The Michaelis constant of G with respect to H2O2 (K) m The maximum reaction rate (V0) was 1.59 mM. max The value is 1.63 × 10⁻⁸ M·s -1 Data show that this hydrogel has extremely high affinity for the substrate, superior to many previously reported enzyme-like materials.

[0050] 4. Self-driven antibacterial test Its antibacterial efficacy was evaluated using the plate count method: Escherichia coli and Staphylococcus aureus (10⁻¹⁰) were counted. 6 CFU mL -1 ) and incubate with each treatment hydrogel for 2 hours.

[0051] Under conditions where no exogenous H2O2 is added, such as Figure 4 As shown in (a)-(d), P 90 VC 10 Group G showed a significant reduction in bacterial colony count, with inhibition rates exceeding 75% against both pathogenic bacteria. This confirms its intelligent biochemical radar function: achieving sterilization by efficiently capturing endogenous H2O2 produced by bacterial metabolism and converting it in situ into a lethal ROS storm.

[0052] 5. Applications in fruit preservation Using cherries and citrus fruits as models, the actual preservation effect of hydrogels was verified. Washed and dried fruits were randomly divided into a control group, a PVA group, a PVG group, and a P... 90 VC 10 Group G, store at room temperature.

[0053] like Figure 5(a) and (b) show that on day 9, the fruit in the control group showed severe spoilage, shriveling, and mold; while P 90 VC 10 The fruits in Group G retain their vibrant colors and plump appearance. For example... Figure 5 (c) and (d) show that P 90 VC 10 Group G consistently maintained the lowest weight loss rate, demonstrating the hydrogel's superior ability to prevent moisture evaporation. Figure 5 Figures 5(e) and 5(f) show that on day 9, the total bacterial count (TVC) in the control group far exceeded the safety limit; while P 90 VC 10 Group G's TVC is strictly limited to 3.43 Lg (CFU / g) (cherries) and 3.09 Lg (CFU / g) (citrus), which fully meets the standards for safe consumption.

[0054] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A smart biomimetic hydrogel, characterized in that, The raw materials include the following parts by weight: 4-5 parts polyvinyl alcohol, 0.4-0.5 parts cationic chitosan, 0.4-0.6 parts glycerol, and 20-22 parts water; It also includes a two-dimensional V2C MXene nanosheet aqueous dispersion; the amount of the two-dimensional V2C MXene nanosheet aqueous dispersion added is such that the mass fraction of the two-dimensional V2C MXene nanosheets in the final hydrogel system is 3%-5%.

2. The intelligent biomimetic hydrogel according to claim 1, characterized in that, The raw materials include the following parts by weight: 4.05 parts polyvinyl alcohol, 0.45 parts cationic chitosan, 0.5 parts glycerol, and 20.2 parts water; It also includes a two-dimensional V2C MXene nanosheet aqueous dispersion; the amount of the two-dimensional V2C MXene nanosheet aqueous dispersion added is such that the mass fraction of the two-dimensional V2C MXene nanosheets in the final hydrogel system is 4%.

3. The intelligent biomimetic hydrogel according to claim 1 or 2, characterized in that, The specific method for preparing the two-dimensional V2C MXene nanosheet aqueous dispersion is as follows: (1) Etching reaction V2AlC powder was added to an aqueous solution of hydrofluoric acid and magnetically stirred to carry out an etching reaction to selectively remove the aluminum layer. (2) Cleaning and drying After the reaction was completed, the precipitate was collected by centrifugation and washing, dried, and ground to obtain layered V2C powder. (3) Intercalation stripping Layered V2C powder was dispersed in an aqueous solution of tripropylammonium hydroxide, and intercalation and exfoliation were performed by magnetic stirring at room temperature. After centrifugation and washing, the supernatant was collected to obtain the aqueous dispersion of the two-dimensional V2C MXene nanosheets.

4. The intelligent biomimetic hydrogel according to claim 3, characterized in that, In step (1), the mass fraction of the hydrofluoric acid aqueous solution is 50%; the ratio of V2AlC powder to hydrofluoric acid aqueous solution is 1 g: 30 mL; the temperature of the magnetic stirring is 55℃ and the time is 72 h.

5. The intelligent biomimetic hydrogel according to claim 3, characterized in that, In step (2), the centrifugal washing speed is 8000 r / min and the time is 5 min until the pH value of the supernatant stabilizes at 7.0; the drying equipment is a vacuum oven with a temperature of 60℃ and a time of 12 h.

6. The intelligent biomimetic hydrogel according to claim 3, characterized in that, In step (3), the mass fraction of the tripropylammonium hydroxide aqueous solution is 5%; the ratio of the layered V2C powder to the tripropylammonium hydroxide aqueous solution is 1g:10mL; and the magnetic stirring time is 24h.

7. A method for preparing an intelligent biomimetic hydrogel, characterized in that, Specifically, the following steps are included: (1) Weigh each raw material according to the weight proportions of the intelligent biomimetic hydrogel according to any one of claims 1-6; (2) Disperse polyvinyl alcohol in water and stir to dissolve it to obtain a polyvinyl alcohol solution; (3) Glycerol and cationic chitosan were added to the polyvinyl alcohol solution in sequence, followed by the addition of two-dimensional V2C MXene nanosheet aqueous dispersion, and stirred evenly to obtain a mixture; (4) The mixture is subjected to freeze-thaw treatment to obtain the intelligent biomimetic hydrogel.

8. The method for preparing a smart biomimetic hydrogel according to claim 7, characterized in that, In step (2), the temperature for stirring and dissolving is 80°C; In step (4), the conditions for the freeze-thaw process are: first freeze at -20℃ for 12 hours, and then thaw at 25℃ for 2 hours.

9. The application of a smart biomimetic hydrogel as described in claims 1-6 or a smart biomimetic hydrogel prepared by the preparation method as described in claim 7 or 8 in the preparation of a postharvest fresh fruit preservation coating.

10. The application of a smart biomimetic hydrogel as described in claims 1-6 or a smart biomimetic hydrogel prepared by the preparation method as described in claim 7 or 8 in the preparation of self-driven antibacterial materials.

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