Metal organic framework composite material based on gamma-cyclodextrin as well as preparation and application of metal organic framework composite material

Abstract

The invention provides a gamma-cyclodextrin-based metal organic framework composite material as well as preparation and application thereof. The metal organic framework composite material based on gamma-cyclodextrin comprises chitosan, gamma-CD-MOFs (Metal Organic Frameworks) and an active substance. The preparation method comprises the following steps: by taking chitosan as a film material base material, synthesizing gamma-CD-MOFs by utilizing a hydrothermal method, and then loading cinnamyl aldehyde with antibacterial property, 2-methoxycinnamyl aldehyde with ultraviolet light resistance and curcumin with an antioxidant effect into the gamma-CD-MOFs. And finally, mixing with chitosan with better film-forming property, and spraying on glass or the surfaces of fresh fruits. The gamma-CD-MOFs has the characteristic of slowly releasing bioactive substances, is non-toxic and is a material capable of being applied to food packaging.

Description

Technical Field

[0001] The present invention relates to the technical field of metal organic framework preparation, and in particular to a metal organic framework composite material based on gamma-cyclodextrin and the preparation and application thereof. Background Art

[0002] γ-cyclodextrin (γ-CD) is a naturally occurring cyclic oligosaccharide that has been widely used in the food industry due to its unique hydrophilic and hydrophobic cavity structures. In this context, food-grade γ-CD and alkali metal ions (K + ) developed non-toxic, biocompatible cyclodextrin-based metal-organic frameworks (γ-CD-MOFs). γ-CD-MOFs exhibit improved biosafety, higher porosity, abundant hydroxyl groups, and humidity-responsive controlled release via host-guest interactions, making them promising reservoirs for bioactive compounds, and the sustained-release properties of γ-CD-MOFs can be used for food packaging. Chitosan is a polysaccharide extracted from deacetylated chitin, and is most commonly used in the manufacture of packaging materials due to its high biodegradability, non-toxicity, good hydrophilicity, and film-forming properties.

[0003] In this regard, the present invention is proposed. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a metal organic framework based on γ-cyclodextrin and its preparation and application.

[0005] In the first aspect, the present invention provides a metal organic framework composite material based on γ-cyclodextrin, wherein the metal organic framework composite material based on γ-cyclodextrin includes chitosan, γ-CD-MOFs and active substances; the γ-CD-MOFs is synthesized by a hydrothermal method from raw materials including γ-cyclodextrin, potassium hydroxide and polyethylene glycol. The γ-CD-MOFs preparation technology provided by the present invention uses γ-cyclodextrin, potassium hydroxide and polyethylene glycol as raw materials for hydrothermal synthesis, and the γ-CD-MOFs provided by the present invention can better prepare metal organic framework composite chitosan loaded with different active substances. The γ-CD-MOFs provided by the present invention has the characteristics of slowly releasing active molecules, which prolongs the shelf life of food. The composite material is non-toxic and can be used in food.

[0006] In the present invention, γ-cyclodextrin (γ-CD) is a naturally occurring cyclic oligosaccharide, which has been widely used in the food field due to its unique hydrophilic and hydrophobic cavity structure. + ) developed nontoxic, biocompatible cyclodextrin-based metal-organic frameworks (γ-CD-MOFs).

[0007] Preferably, the active substance includes one or more of cinnamaldehyde, 2-methoxycinnamaldehyde and curcumin. The present invention uses cinnamaldehyde, 2-methoxycinnamaldehyde and curcumin loaded on γ-CD-MOFs and mixed with chitosan to form a coating with antibacterial, light-blocking and antioxidant functions. For example, when γ-CD-MOFs are loaded with 2-methoxycinnamaldehyde, it has a light-blocking effect. Its ultraviolet absorption is measured and it is found that it can block ultraviolet light up to 380nm, and the light-blocking effect is ideal.

[0008] Preferably, the polyethylene glycol is polyethylene glycol 20000. The present invention finds that polyethylene glycol 20000 has more advantages than other alcohol raw materials, and the prepared γ-CD-MOFs have better application effect in food packaging.

[0009] Preferably, the molar ratio of γ-cyclodextrin to potassium hydroxide is 1:2-32; preferably, the molar ratio of γ-cyclodextrin to potassium hydroxide is 1:6-10, preferably 1:8; the effect of using the above raw materials in the preferred ratio is better. For example, the molar ratio of γ-cyclodextrin to potassium hydroxide is 1:2, 1:4, 1:6, 1:8, 1:10, 1:16, 1:32, etc. and any value therebetween, preferably 1:8.

[0010] Preferably, the volume ratio of the chitosan to the γ-CD-MOFs is 1:0.5-8, preferably 1:1. The present invention does not limit the amount of some raw materials such as polyethylene glycol, for example, it can be appropriately adjusted based on the specific amount in the embodiments of the present invention.

[0011] In the present invention, the reaction time of γ-cyclodextrin, potassium hydroxide, methanol and polyethylene glycol can be as short as 15 minutes, 30 minutes, 45 minutes and 60 minutes, preferably 45 minutes. The reaction time of the hydrothermal method in the existing method reaches more than 6 hours. The present invention greatly shortens the reaction time and improves the efficiency; the concentration of the chitosan can be 1%, 2%, 3%, 4% and 5%, preferably 2%.

[0012] In the γ-CD-MOFs synthesized by the present invention, the oxygen on the ether bond of γ-cyclodextrin is connected to the hydroxyl group thereon via potassium ions. The γ-CD-MOFs with a cubic structure synthesized by this method can be loaded with some water-insoluble bioactive substances, which can be dissolved in water after loading, thereby improving water solubility, and then chitosan with adhesiveness is mixed with the substances for spraying. Cinnamaldehyde, 2-methoxycinnamaldehyde and curcumin loaded by γ-CD-MOFs can not only improve their stability, but also control their release, so as to better exert the antibacterial effect of cinnamaldehyde, the light-blocking effect of 2-methoxycinnamaldehyde and the antioxidant effect of curcumin.

[0013] The invention provides a preparation technology for γ-CD-MOFs and a preparation method for a metal organic framework composite chitosan capable of loading different active substances, which solves the problem of unstable and volatile properties of biologically active substances. Chitosan is used as a polymer and mixed with γ-CD-MOFs to form a CS / γ-CD-MOFs solution. γ-CD-MOFs can load various biologically active substances and have the characteristics of slow release. This carrier can improve the stability and bioavailability of biologically active substances.

[0014] In a second aspect, the present invention provides an application of the above-mentioned γ-cyclodextrin-based metal organic framework composite material in food packaging, comprising spraying the γ-cyclodextrin-based metal organic framework composite material on the surface of food or food packaging.

[0015] In a third aspect, the present invention provides a method for preparing a metal organic framework composite material based on γ-cyclodextrin, comprising: 1) A γ-cyclodextrin solution and a potassium hydroxide solution are mixed, a methanol solution is added, ultrasonic treatment is performed, and then the obtained mixed solution is heated.

[0016] 2) Mixing the mixed solution treated in step 1) with polyethylene glycol and allowing it to stand for reaction; then centrifuging, absorbing the supernatant and retaining the precipitate; washing and drying the obtained precipitate.

[0017] 3) The γ-CD-MOFs treated in step 2) are shaken in a dichloromethane solution and then dried to increase the loading amount of the γ-CD-MOFs to obtain activated γ-CD-MOFs.

[0018] 4) The active material is mixed with the activated γ-CD-MOFs in step 3), shaken, washed and dried.

[0019] 5) Mixing the γ-CD-MOFs loaded with active substances in step 4) with chitosan solution to obtain a metal organic framework composite material based on γ-cyclodextrin. The γ-CD-MOFs prepared by the present invention exhibit better biosafety, higher porosity, abundant hydroxyl groups and humidity-responsive controlled release through host-guest interaction, making them a promising reservoir for bioactive compounds, and the sustained release properties of γ-CD-MOFs can be used for food packaging. Chitosan has good biodegradability and film-forming properties, and can be sprayed on the surface of food to prevent it from spoiling.

[0020] Preferably, in step 1), the alcohol solution is a methanol solution; the ultrasonic treatment time is 3-10 min, preferably 5 min; the heating treatment temperature is 60-80° C., preferably 70° C. in a water bath.

[0021] Further preferably, in step 2), the polyethylene glycol is polyethylene glycol 20000, and the concentration is 6-10 mg / ml, preferably 8 mg / ml; and / or, the mixing temperature is 15-30°C, preferably room temperature; and / or, the standing reaction time is 15-60 min; for example, the standing reaction time is 15 min, 30 min, 45 min, 60 min, etc. and any value therebetween, preferably 45 min, and the centrifugal condition is 6000-10000 r / min, preferably 10000 r / min, for 5-10 min, preferably 10 min. If the centrifugal speed is too low or the time is too short, the precipitate cannot be separated. This condition is the best condition for leaving the precipitate. The obtained precipitate is washed 2-3 times with isopropanol and dried in vacuo at 45-50°C.

[0022] Further preferably, in step 3), the dichloromethane solution needs to be replaced every 20-30 hours during the oscillation process; and / or, after oscillating for 3-4 days, vacuum drying is performed at 45-50°C.

[0023] Further preferably, in step 4), after shaking for 10 to 12 hours, washing with anhydrous ethanol 2 to 3 times and vacuum drying at 45 to 50° C.; and / or, the concentration of the active substance is made to reach a saturated loading amount; preferably, the loading concentration of cinnamaldehyde is ≤4 mg / ml; and / or, the loading concentration of 2-methoxycinnamaldehyde is ≤2 mg / ml; and / or, the loading concentration of curcumin is ≤2 mg / ml.

[0024] Further preferably, in step 5), the volume ratio of the γ-CD-MOFs loaded with active substances to the chitosan solution is 1:0.5-1:8, preferably 1:1. Too much chitosan will destroy the crystallinity of γ-CD-MOF and change the structure of γ-CD-MOF, while too little chitosan will reduce the adhesion of the material; and / or the concentration of the chitosan is 18-20 mg / ml.

[0025] The present invention can improve the stability and bioavailability of bioactive substances based on the slow release characteristics of γ-CD-MOFs. γ-CD-MOFs can be used as a platform to load different bioactive substances for use in food packaging, thereby improving the preservation effect of food. The present invention loads cinnamaldehyde with antibacterial properties, 2-methoxycinnamaldehyde with UV blocking properties, and curcumin with antioxidant effects into γ-CD-MOFs. Finally, it is mixed with chitosan with good film-forming properties and sprayed on glass or the surface of fresh fruits. γ-CD-MOFs has the characteristics of slow release of bioactive substances and is non-toxic. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art.

[0027] Figure 1 The synthetic electron micrographs of γ-CD-MOFs provided in the embodiments of the present invention and the PdI values ​​of γ-CD-MOFs at different growth times are shown.

[0028] Figure 2 Fourier transform infrared spectroscopy (FTIR) diagram of the γ-CD-MOFs provided in an embodiment of the present invention before and after loading cinnamaldehyde, 2-methoxycinnamaldehyde and curcumin.

[0029] Figure 3 X-ray diffraction spectra (XRD) of the γ-CD-MOFs provided in the embodiments of the present invention before and after loading cinnamaldehyde, 2-methoxycinnamaldehyde and curcumin.

[0030] Figure 4 The saturated loading amount of cinnamaldehyde, 2-methoxycinnamaldehyde and curcumin loaded on the γ-CD-MOFs provided in the embodiment of the present invention.

[0031] Figure 5 The sustained release curves of the three active substances provided in the examples of the present invention from γ-CD-MOFs.

[0032] Figure 6 The present invention provides an embodiment of the invention which provides a mixture of γ-CD-MOFs loaded with cinnamaldehyde and chitosan for antibacterial properties.

[0033] Figure 7 The light-blocking property of the γ-CD-MOFs loaded with 2-methoxycinnamaldehyde and chitosan provided in the embodiment of the present invention.

[0034] Figure 8 The antioxidant properties of the mixture of γ-CD-MOFs loaded with curcumin and chitosan provided in the embodiments of the present invention.

[0035] Fig. 9 The invention provides the cytotoxicity of γ-CD-MOFs after loading cinnamaldehyde, 2-methoxycinnamaldehyde and curcumin. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] If no specific technology or conditions are specified in the embodiments of the present invention, the technology or conditions described in the literature in this field or the product instructions are used. If the manufacturer of the devices, instruments, reagents, etc. is not specified, they are all conventional products that can be purchased through regular channels. The raw materials used in the present invention can be easily purchased in the domestic product market.

[0038] As a preferred embodiment, the method for preparing the metal organic framework composite material based on γ-cyclodextrin comprises the following steps: (1) Mix the γ-cyclodextrin solution and potassium hydroxide solution, add methanol solution to obtain a white emulsion, and treat with ultrasound for 5 min.

[0039] (2) Place the mixture obtained in step (1) in a water bath at 70°C until the white emulsion becomes clear.

[0040] (3) At room temperature, quickly add polyethylene glycol 20000 to the transparent solution obtained in step (2) and let it stand for 1 hour.

[0041] (4) After standing for 1 hour, centrifuge, aspirate the supernatant and retain the precipitate.

[0042] (5) The precipitate obtained in step (4) was washed 2 to 3 times with isopropanol and then dried in vacuum at 50°C.

[0043] (6) Activation: The γ-CD-MOFs solid powder obtained after drying was immersed in a dichloromethane solution, shaken for 3 days, and then dried in a vacuum oven at 50 °C.

[0044] (7) Cinnamaldehyde, 2-methoxycinnamaldehyde and curcumin were added to the activated γ-CD-MOFs respectively, and after oscillation for 12 h, they were washed with anhydrous ethanol for 2 to 3 times and dried for later use.

[0045] (8) Mixing the γ-CD-MOFs loaded with the corresponding substances with the chitosan solution.

[0046] As a preferred embodiment, in step (1), the molar ratio of γ-cyclodextrin solution to potassium hydroxide solution is 1:8. In step (2), a water bath is required at 70°C. In step (3), 8 mg / ml of polyethylene glycol 20000 is used and added quickly at room temperature. In step (4), the reaction time must be strictly calculated according to 1 hour, and the centrifugation condition is 10,000 r / min for 5 minutes. In step (6), the dichloromethane solution must be replaced every 24 hours during the oscillation process. In step (7), the concentration of the three active substances should reach the saturated loading amount and vacuum dried at 50°C. In step (8), the concentration of chitosan is 20 mg / ml.

[0047] In the present invention, some terms are explained as follows: γ-CD: γ-cyclodextrin, γ-CD-MOFs: metal organic framework based on γ-cyclodextrin, K + : potassium ion, CS: chitosan, Cia: cinnamaldehyde, methoxyclnnamaldehyde: 2-methoxycinnamaldehyde, Cur: curcumin.

[0048] The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art, and the raw materials used are all commercially available products.

[0049] The experimental materials and instruments used in the following examples are: γ-cyclodextrin, 98%, purchased from Aladdin. Potassium hydroxide, AR, purchased from Aladdin. Methanol, polyethylene glycol (20000), purchased from Aladdin. Dichloromethane, AR 99.5%, purchased from Aladdin. Chitosan was purchased from Shanghai MacLean Biochemical Technology Co., Ltd. Cinnamaldehyde, ≥95%, purchased from Aladdin. 2-Methoxycinnamaldehyde, 98%, purchased from Aladdin. Curcumin, 98% (synthetic), purchased from Aladdin. Isopropyl alcohol, 99.8% (preparative chromatography reagent), purchased from Shanghai E-En Chemical Technology Co., Ltd.

[0050] Magnetic stirrer (Aika), RCT bask set; long axis rotary mixer (Qun'an), RO-80; vacuum drying oven (Linhai Yonghao), DZF-6024; plastic vacuum dryer, HP-PC-150, purchased from Changde Beekman Biotechnology Co., Ltd. UV spectrophotometer, Q-6, purchased from Shanghai Yuanxi Instrument Co., Ltd. Ultrasonic cleaner, purchased from Kunshan Ultrasonic Instrument Co., Ltd. Electronic balance (Qun'an); high-speed refrigerated centrifuge, H1750R, purchased from Hunan Xiangyi Laboratory Instrument Development Co., Ltd.

[0051] Example 1 This embodiment provides a preparation technology of γ-CD-MOFs and a preparation method of a metal organic framework composite chitosan capable of loading different active substances, comprising the following steps: Step 1: Take 3 mL of 130 mg / 3 mL γ-CD solution and 0.84 mL of 45 mg / 0.84 mL KOH solution in a 50 mL centrifuge tube, add 2.7 mL of methanol solution to mix to obtain a white emulsion, and ultrasonicate for 5 min.

[0052] Step 2: Quickly add 6.5 mL of polyethylene glycol 20000 solution (concentration 8 mg / ml) to the above solution at room temperature. After standing for 1 hour, centrifuge at 10000 r / min for 10 minutes, aspirate the supernatant, and keep the precipitate.

[0053] Step 3: The precipitate obtained in step 2 was washed three times with isopropanol and dried under vacuum at 50 °C for 10 h.

[0054] Step 4: Add 1 mL of cinnamaldehyde (2-methoxycinnamaldehyde or curcumin) solution to a centrifuge tube containing 1.5 mg of γ-CD-MOFs powder, shake for 12 h, centrifuge at 6000 r / min for 10 min, wash the precipitate with anhydrous ethanol three times, and vacuum dry at 50 °C for 4 h.

[0055] Example 2 60 mg of γ-CD-MOFs were immersed in a centrifuge tube filled with dichloromethane solution, shaken on a long-axis rotary mixer for 3 days, centrifuged at 10000 r / min for 10 min, and vacuum dried at 50 °C for 12 h.

[0056] Compared with Example 1, the difference in Example 2 is that the γ-CD-MOFs are activated to remove the high boiling point solvent and water in the pores.

[0057] Example 3 40 mL of cinnamaldehyde (2-methoxycinnamaldehyde, curcumin) solution was added to a centrifuge tube containing 60 mg of γ-CD-MOFs powder, shaken for 12 h, centrifuged at 6000 r / min for 10 min, and the precipitate was washed three times with anhydrous ethanol and dried in vacuum at 50 °C for 4 h.

[0058] Compared with Example 1, the difference in Example 3 is that the cinnamaldehyde (2-methoxycinnamaldehyde, curcumin) solution reaches the saturated loading concentration for loading.

[0059] Example 4 Compared with Example 1, Example 4 is different in that a chitosan solution is added to the γ-CD-MOFs loaded with cinnamaldehyde (2-methoxycinnamaldehyde, curcumin) molecules.

[0060] Example 5 Compared with Example 4, the difference in Example 5 is that the concentration of the added chitosan solution is adjusted to 20 mg / ml.

[0061] Example 6 Compared with Example 5, the difference in Example 6 is that the volume ratio of the added chitosan solution to the γ-CD-MOFs solution is adjusted to 1:1.

[0062] Comparative Example 1 As a comparison standard for each of the above embodiments, the present invention provides a chitosan material prepared without γ-CD-MOFs, comprising the following steps: Step 1: Add 1 g of CS to 49.5 ml of aqueous solution, then add 500 μL of 1% (V / V) acetic acid solution, and stir at 800 rpm for 12 h until CS is completely dissolved to obtain a CS aqueous solution.

[0063] Step 2: Take 1 ml of CS solution, mix it, shake it with ultrasound, and then evacuate it to remove bubbles.

[0064] Structure and performance test: The chitosan material prepared in the above comparative example 1 and the chitosan composite material with antibacterial, antioxidant and light-blocking properties prepared in Example 5 were subjected to structural and performance tests. The synthesis electron micrograph of γ-CD-MOFs is shown in FIG. Figure 1 The chemical structures of γ-CD-MOFs and γ-CD-MOFs loaded with cinnamaldehyde, 2-methoxycinnamaldehyde and curcumin molecules were characterized by Fourier transform infrared spectroscopy (FTIR), such as Figure 2 The crystal structures of γ-CD-MOFs and γ-CD-MOFs loaded with cinnamaldehyde, 2-methoxycinnamaldehyde and curcumin molecules were characterized by X-ray diffraction (XRD), such as Figure 3 ; Saturation loadings of cinnamaldehyde, 2-methoxycinnamaldehyde, and curcumin, e.g. Figure 4 ; The antibacterial properties were tested according to the inhibition zone method, such as Figure 5 ; The light blocking property is tested by UV spectrophotometer, such as Figure 6 ; Antioxidant properties were tested according to the DPPH free radical scavenging method, such as Figure 7 .

[0065] Analysis of test results: 1. Synthesis electron microscopy of γ-CD-MOFs Figure 1 The results show that γ-CD-MOFs were successfully synthesized. As shown in the figure, the nanomaterial has a typical cubic structure and is evenly distributed, with a diameter of 200-300 nm. When the reaction time is 45 minutes, the polymer dispersion coefficient of γ-CD-MOFs is the smallest, indicating that the crystals are relatively uniform at this time.

[0066] 2. FTIR analysis results The structural characteristics of γ-CD and γ-CD-MOF are similar, with a peak at 1022 cm -1 A strong absorption peak was observed at γ-CD-MOF, indicating that γ-CD-MOF contains not only the structural information of γ-CD, but also K +Participation. 2924cm -1 The stretching vibration peaks on the left and right sides moved to 2905 cm -1 , 3300cm -1 The stretching vibration peaks on the left and right are slightly enhanced, indicating the successful synthesis of γ-CD-MOF. -1 The stretching vibration peak of COC appears around 3000-3700cm -1 、2926 cm -1 、1647 cm -1 There are similar characteristic peaks at 1650 cm -1 The characteristic peaks of carbonyl groups are obvious on the left and right. In the spectrum of Cur, at 1281 cm -1 The characteristic peak of the phenolic hydroxyl group of Cur at 3000-3700 cm is obvious. After encapsulating cinnamaldehyde, 2-methoxycinnamaldehyde and curcumin, the infrared spectrum did not change significantly. Compared with γ-CD-MOF, γ-CD-MOF@Cur has a -1 After loading, the characteristic peaks of 500-1800 cm -1 The characteristic peak at γ-CD-MOF disappears or decreases in intensity, which is due to the fact that the bioactive molecules enter the cavity of γ-CD-MOF and are shielded by it.

[0067] 3. XRD analysis results like Figure 3 As shown, there is no obvious change in the characteristic peaks of γ-CD-MOFs before and after loading cinnamaldehyde, 2-methoxycinnamaldehyde and curcumin, indicating that the loading did not change the crystal structure of γ-CD-MOFs.

[0068] 4. Saturation loading analysis results like Figure 4 As shown, 1.5 mg of γ-CD-MOFs was used to load different concentrations of cinnamaldehyde, 2-methoxycinnamaldehyde and curcumin. The results showed that the saturation loading capacity was reached after loading cinnamaldehyde at a concentration of 4 mg / ml, the saturation loading capacity was reached after loading 2-methoxycinnamaldehyde at a concentration of 2 mg / ml, and the saturation loading capacity was reached after loading curcumin at a concentration of 2 mg / ml.

[0069] 5. Release Behavior Research Results like Figure 5As shown, the release patterns of cinnamaldehyde, 2-methoxycinnamaldehyde and curcumin from γ-CD-MOFs conform to the Ritger-Peppas equation, indicating that the material has sustained-release properties.

[0070] 6. Antibacterial performance analysis results like Figure 6 As shown in the figure, the sizes of inhibition zones treated with CS, CS / MOF and CS / MOF@Cia solutions show that CS / MOF@Cia solution has good antibacterial ability, indicating that the solution has good antioxidant properties.

[0071] 7. UV-Vis performance analysis results like Figure 7 As shown, the transmission spectra of CS, CS / MOF and CS / MOF@2-methoxyclnnamaldehyde solutions. The CS / MOF@2-methoxyclnnamaldehyde solution shows extensive and significant UV absorption (protection).

[0072] 8. Antioxidant performance analysis results like Figure 8 As shown in Figure 2, the DPPH scavenging rates of CS, CS / MOF and CS / MOF@Cur solutions were calculated. It was found that CS / MOF@Cur solution had good free radical scavenging ability and good antioxidant effect.

[0073] 9. Cytotoxicity test results like Fig. 9 As shown, the cell survival rates after treatment with γ-CD-MOF, γ-CD-MOF loaded with cinnamaldehyde, γ-CD-MOF loaded with 2-methoxycinnamaldehyde and γ-CD-MOF loaded with curcumin were not significantly different from those of the control group, indicating that the material is non-toxic and can be used in food.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A metal-organic framework composite material based on γ-cyclodextrin, characterized in that: The γ-cyclodextrin-based metal organic framework composite material comprises chitosan, γ-CD-MOFs and active substances; the γ-CD-MOFs are synthesized from raw materials including γ-cyclodextrin, potassium hydroxide and polyethylene glycol through a hydrothermal method.

2. The metal-organic framework composite material based on γ-cyclodextrin according to claim 1, characterized in that: The active substance includes one or more of cinnamaldehyde, 2-methoxycinnamaldehyde and curcumin.

3. The metal-organic framework composite material based on γ-cyclodextrin according to claim 1 or 2, characterized in that: The polyethylene glycol is polyethylene glycol 20000.

4. The metal-organic framework composite material based on γ-cyclodextrin according to any one of claims 1 to 3, characterized in that: The molar ratio of the γ-cyclodextrin to potassium hydroxide is 1:2-32; preferably, the molar ratio of the γ-cyclodextrin to potassium hydroxide is 1:

8.

5. Use of the metal organic framework composite material based on γ-cyclodextrin according to any one of claims 1 to 4 in food packaging.

6. A method for preparing a metal-organic framework composite material based on γ-cyclodextrin, characterized in that: include: 1) mixing a γ-cyclodextrin solution and a potassium hydroxide solution, adding an alcohol solution, ultrasonically treating the mixture, and then heating the obtained mixture; 2) mixing the mixed solution treated in step 1) with polyethylene glycol and allowing to stand for reaction; then centrifuging, absorbing the supernatant and leaving the precipitate; washing and drying the obtained precipitate; 3) shaking the γ-CD-MOFs treated in step 2) in a dichloromethane solution, and then drying to obtain activated γ-CD-MOFs; 4) mixing the active substance with the activated γ-CD-MOFs in step 3), shaking, washing and drying; 5) Mixing the γ-CD-MOFs loaded with active substances in step 4) with a chitosan solution to obtain a metal organic framework composite material based on γ-cyclodextrin.

7. The method for preparing a metal-organic framework composite material based on γ-cyclodextrin according to claim 6, characterized in that: In step 1), the alcohol solution is a methanol solution; the ultrasonic treatment time is 3 to 10 minutes; the heating treatment temperature is 60 to 80°C; and / or, in step 2), the polyethylene glycol is polyethylene glycol 20000 with a concentration of 6 to 10 mg / ml; and / or, the mixing temperature is 15 to 30°C; and / or, the static reaction time is 15 to 60 minutes, and the centrifugal condition is centrifugation at a speed of 6000 to 10000 r / min for 5 to 10 minutes; and / or, the obtained precipitate is washed 2 to 3 times with isopropanol and vacuum dried at 45 to 50°C.

8. The method for preparing a metal-organic framework composite material based on γ-cyclodextrin according to any one of claims 6 to 7, characterized in that: In step 3), the dichloromethane solution needs to be replaced every 20 to 30 hours during the oscillation process; and / or, after oscillating for 3 to 4 days, vacuum drying is performed at 45 to 50°C.

9. The method for preparing a metal-organic framework composite material based on γ-cyclodextrin according to any one of claims 6 to 8, characterized in that: In step 4), after shaking for 10 to 12 hours, washing with anhydrous ethanol 2 to 3 times and vacuum drying at 45 to 50° C.; and / or, the concentration of the active substance reaches a saturated loading amount; preferably, the loading concentration of cinnamaldehyde is ≤4 mg / ml; and / or, the loading concentration of 2-methoxycinnamaldehyde is ≤2 mg / ml; and / or, the loading concentration of curcumin is ≤2 mg / ml.

10. The method for preparing a metal-organic framework composite material based on γ-cyclodextrin according to any one of claims 6 to 9, characterized in that: In step 5), the concentration of chitosan is 18-20 mg / ml.

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