Antibacterial film loaded with fucoxanthine nano material and preparation method of antibacterial film

Abstract

The invention discloses an antibacterial film loaded with a fucoxanthin nano material and a preparation method of the antibacterial film. The antibacterial film is prepared by taking a nitrogen-rich hollow carbon material-fucoxanthin (NHC-FX) nano material as an antibacterial photosensitizer, chitosan as a substrate of a film and glycerol as a plasticizer of the film through a solution casting method. The antibacterial film disclosed by the invention is good in hydrophobicity and high in stability, can reduce transmission of ultraviolet light, and has a good photodynamic antibacterial effect. The antibacterial food packaging material can be used as an antibacterial food packaging material or a preservative film, can prevent food from being polluted by microorganisms, and can isolate damage of ultraviolet rays to the food.

Description

Technical Field

[0001] The invention relates to the technical field of antibacterial packaging films, and in particular to an antibacterial film loaded with fucoxanthin nanomaterials and a preparation method thereof. Background Art

[0002] In recent years, the market of pre-prepared food has grown tremendously and has become an important part of the modern food industry with broad market prospects. The production process of pre-prepared food is based on modern assembly line standards. Whether the food is fresh when it is finally delivered to customers depends largely on the packaging technology of the pre-prepared food. Therefore, how to control the quality of pre-prepared food through effective antibacterial packaging technology has become one of the key points for the further development of the pre-prepared food industry.

[0003] Photodynamic antimicrobial technology (PDI) is a technology that uses a large number of active oxygen free radicals produced by photosensitizers under light conditions to inactivate microorganisms. It is a potential new non-thermal sterilization technology and a hot spot in the current research field. PDI not only does not cause microbial resistance, but also maintains the nutritional and sensory quality of processed food, which is more advantageous than traditional food preservation methods.

[0004] Chitosan (CS) is a natural polysaccharide obtained by deacetylation of chitin. Due to its excellent film-forming properties, biodegradability, good safety and low cost, CS and its derivatives are widely used as substrates for various packaging films and are also widely used in the fields of cosmetics, food and biomedicine.

[0005] Zeolitic imidazolate framework-8 (ZIF-8) uses zinc as the metal center and 2-methylimidazole (2-MIM) as the organic ligand, and self-assembles through coordination bonds. ZIF-8 also has excellent chemical stability and hydrothermal stability, and has a larger pore size and specific surface area than other MOFs. Due to its superior biocompatibility, easy modification and degradability, ZIF-8 has been widely studied in the biomedical field, especially in drug carriers.

[0006] Although various types of antibacterial films have been proposed, they are restricted in practical application due to the inherent defects of traditional antibacterial agents. For example, the patent application with publication number CN116278273A discloses an antibacterial polyethylene composite film. The polyethylene composite film prepared by this method has antibacterial effects in both the middle film and the inner film, which inhibits the production of bacteria to a greater extent. The patent application with publication number CN118849576A discloses an anti-fog antibacterial fresh-keeping film with a fresh-keeping function. The zirconium phosphate silver added in the invention has good heat resistance, good antibacterial effect, and small antibacterial particle size. The overall antibacterial effect and organic gas adsorption of the product can achieve good results, and at the same time have the effect of spontaneous gas conditioning. However, the organic antibacterial agents added to these films need to be used in large doses, and because of their violent release, the antibacterial effect lasts for a short time, and even causes microorganisms to develop drug resistance. In contrast, metal-based inorganic antimicrobial agents have a longer duration of action. For example, the patent application with publication number CN113004568A discloses a composite antibacterial food packaging film, which combines the advantages of natural antimicrobial agents and inorganic metal antimicrobial agents, and solves the disadvantage of weak antimicrobial performance of natural antimicrobial agents. The patent application with publication number CN1 16409038A discloses a frozen food packaging film with long-lasting antibacterial and antiviral functions, which forms a constant antibacterial and antiviral ability by fixing the position of ionic zinc elements, providing excellent antibacterial properties for the entire product. However, this type of method uses inorganic antimicrobial agents for antibacterial, which takes effect slowly and may have safety hazards of metal residues. In addition, pure CS film does have limited bactericidal activity, low mechanical strength and poor hydrophobicity in practical applications, which cannot meet the application of food industry. Therefore, it is necessary to combine other strengthening strategies to improve the comprehensive effects of the film such as antibacterial, so as to effectively inhibit or kill pathogenic microorganisms and achieve long-term preservation. Although adding functional fillers is a promising method that can enhance the inherent properties of the film while grafting specific functions, the prior art, such as the patent application with patent publication number CN116039199B, discloses a photodynamic antibacterial, UV-resistant, biodegradable multifunctional composite film based on ZIF-8, adding ZIF-8 loaded with Bengal red photosensitizer, and combining PDI technology to disinfect bacteria. However, although this method has a certain antibacterial effect, it still has problems such as residual zinc ions and the need to improve the stability of the carrier.

[0007] Therefore, it is very meaningful to develop an advanced antibacterial packaging system to make up for the above defects and extend the shelf life of food. Summary of the invention

[0008] In view of the above problems existing in the prior art, the present invention provides an antibacterial film loaded with fucoxanthin nanomaterials and a preparation method thereof. The present invention uses nitrogen-rich hollow carbon material-fucoxanthin (NHC-FX) nanomaterial as an antibacterial photosensitizer, chitosan as a film matrix, and glycerol as a film plasticizer, and is prepared by a solution casting method. The antibacterial film of the present invention has good hydrophobicity, high stability, can reduce the penetration of ultraviolet light, and has a good photodynamic antibacterial effect.

[0009] The technical solution of the present invention is as follows:

[0010] The first object of the present invention is to provide a method for preparing an antibacterial film loaded with fucoxanthin nanomaterials, comprising the following steps:

[0011] (1) Zn(NO3)2·6H2O reacts with 2-methylimidazole to prepare ZIF-8 crystals;

[0012] (2) dissolving ZIF-8 crystals in an ethanol solution to form a ZIF-8 ethanol solution, and then reacting with a tannic acid aqueous solution to obtain an etched ZIF-8, i.e., HZIF-8;

[0013] (3) HZIF-8 is calcined at high temperature to obtain a carbonized product NHC, which is then compounded with fucoxanthin FX to obtain an NHC-FX composite material;

[0014] (4) Chitosan, glycerol and NHC-FX composite materials are mixed and dissolved in an acetic acid aqueous solution to prepare a film-forming solution, which is then formed into a film in a mold to obtain an antibacterial film loaded with fucoxanthin nanomaterials.

[0015] In one embodiment of the present invention, in step (1), the molar ratio of Zn(NO3)2·6H2O to 2-methylimidazole is 1:8 to 1:10; and the reaction conditions are: 20 to 37°C, 1 to 2h.

[0016] In one embodiment of the present invention, in step (1), Zn(NO3)2·6H2O and 2-methylimidazole are dissolved in anhydrous methanol to form two solutions, which are mixed and stirred at 20-37°C for 1-2h, then centrifuged at 8000-10000rpm for 5min, washed with anhydrous methanol, and the operation is repeated at least three times, and then dried at 60°C to obtain ZIF-8 crystals.

[0017] In one embodiment of the present invention, in step (2), the concentration of the ZIF-8 ethanol solution is 0.02 g / mL; the volume ratio of the ZIF-8 ethanol solution to the tannic acid aqueous solution is 1:5; and the concentration of the tannic acid aqueous solution is 6 to 12 g / L.

[0018] In one embodiment of the present invention, in step (2), the reaction conditions are: stirring at room temperature for 0.5 to 1 hour; after the reaction, the precipitate is washed with deionized water and methanol, centrifuged, and vacuum dried.

[0019] In one embodiment of the present invention, in step (2), the concentration of the ethanol solution is 90-100 wt %.

[0020] In one embodiment of the present invention, in step (2), the centrifugation, washing and drying conditions remain the same as in step (1).

[0021] In one embodiment of the present invention, in step (3), the conditions for high temperature calcination are: calcination at 700-900° C. for 1.5-2 h in a nitrogen atmosphere; and the mass ratio of FX to NHC is 1:1-4.

[0022] In one embodiment of the present invention, in step (3), FX and NHC are mixed and dispersed in anhydrous ethanol, ultrasonically treated for 10 minutes, stirred at room temperature, and blown dry with a nitrogen stream to obtain a solid powder; then the solid powder is dispersed in a 10wt% ethanol aqueous solution, centrifuged, washed and vacuum freeze-dried to obtain an NHC-FX composite material; the centrifugation and washing conditions must be consistent with those in step (1).

[0023] In one embodiment of the present invention, the purity of fucoxanthin is 97-99.9%, all of which comes from marine brown algae and is a natural active compound. The molecular weight of chitosan is 50-300 kDa, and the degree of deacetylation is ≥95%.

[0024] In one embodiment of the present invention, in step (4), the volume concentration of the acetic acid aqueous solution is 1%.

[0025] In one embodiment of the present invention, in step (4), the mass ratio of chitosan, glycerol and NHC-FX composite material is 1:0.25:0.01-0.02.

[0026] In one embodiment of the present invention, in step (4), the film-forming liquid is ultrasonically removed from bubbles before film formation in the mold, and then poured into the mold; the film-forming conditions are: 50-75° C., 6-12 h.

[0027] The second object of the present invention is to provide an antibacterial film loaded with fucoxanthin nanomaterials prepared by the above method.

[0028] The third object of the present invention is to provide an application of the above antibacterial film, which is used as an antibacterial food packaging material or a fresh-keeping film, which can prevent food from being contaminated by microorganisms and isolate food from damage by ultraviolet rays.

[0029] The beneficial technical effects of the present invention are:

[0030] The NHC used in the present invention is ZIF 8 which has been subjected to high temperature carbonization to remove the metal ion Zn 2+ The porous structure formed by the FX reduces the residual metal ions. FX is a green and safe natural pigment that can produce active oxygen with bactericidal effect under the irradiation of light of a certain wavelength.

[0031] After FX is loaded onto NHC, the FX molecules are fully dispersed and coupled with NHC to construct a heterostructure, thereby inhibiting the rapid recombination of photogenerated electron-hole pairs and improving the ability of fucoxanthin to generate active oxygen after light irradiation.

[0032] Traditional antibacterial cling film may produce drug resistance to bacteria and cannot effectively eliminate bacteria. The present invention combines "photodynamic antibacterial" to disinfect bacteria, which can effectively kill bacteria, prevent the emergence of drug-resistant bacteria, and hinder the formation of bacterial biofilm.

[0033] The antibacterial film loaded with fucoxanthin nanomaterials prepared by the present invention has a smooth surface and a compact structure. Compared with a pure CS-based film, the antibacterial film has excellent PDI activity, significantly improved hydrophobicity, and significantly reduced water vapor permeability, water content, and water solubility. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of the synthesis route of the present invention;

[0035] Figure 2 TEM images of materials prepared at different synthesis stages in Example 1 of the present invention;

[0036] Figure 3 The SEM images of the composite membranes prepared in Example 1 and Comparative Examples 1-3 of the present invention;

[0037] Figure 4 The UV-visible spectra of the films prepared in Example 1 and Comparative Examples 1-3 of the present invention;

[0038] Figure 5 The killing effect of the composite film prepared in Example 1 of the present invention on two types of bacteria at different illumination times;

[0039] Figure 6 The killing of two kinds of bacteria by the films prepared in Example 1 of the present invention and Comparative Examples 1-3 when irradiated with light for the same time. DETAILED DESCRIPTION

[0040] The present invention is described in detail below in conjunction with the accompanying drawings and embodiments.

[0041] The terms used in the following examples generally have the meanings commonly understood by those of ordinary skill in the art, unless otherwise specified. In addition, the raw materials, equipment, etc. used in the following examples can be obtained by purchasing commercial products unless otherwise specified. Fucoxanthin in the examples was purchased from Chengdu Desi Biotechnology Co., Ltd.

[0042] Figure 1 Schematic diagram of the synthesis route of the present invention. After ZIF-8 is prepared by dimethylimidazole and zinc nitrate, NHC-FX is prepared by acid etching and high temperature annealing.

[0043] Example 1

[0044] A method for preparing an antibacterial film loaded with fucoxanthin nanomaterials comprises the following steps:

[0045] Step (1): Under room temperature, Zn(NO3)2·6H2O and 2-methylimidazole are dissolved in anhydrous methanol in a molar ratio of 1:8 to form two solutions. 2-MIM is slowly dripped into Zn(NO3)2·6H2O to obtain a synthetic solution. Stir vigorously at 20°C for 1 hour, then centrifuge the crystal dispersion obtained after synthesis (10000rpm, 5min) to obtain a crude product, and then wash the obtained precipitate with fresh anhydrous methanol. After repeating the above centrifugation operation three times, the precipitate is placed in a constant temperature oven at 60°C and dried for 12 hours to obtain ZIF-8 crystals.

[0046] Step (2): Dissolve ZIF-8 crystals in an ethanol solution (the concentration of the ethanol solution is 90 wt%) to form a ZIF-8 ethanol solution with a concentration of 0.02 g / mL, and then mix with a tannic acid aqueous solution (6 g / L), the volume ratio of the ZIF-8 ethanol solution to the tannic acid aqueous solution being 1:5, stir at room temperature for 1 hour, and after the precipitate is formed, wash thoroughly with deionized water and methanol for 3 times to remove impurities. Finally, dry at 60° C. under vacuum conditions for 12 hours to obtain etched ZIF-8 (HZIF-8).

[0047] Step (3): The HZIF-8 obtained in step (2) is placed in a nitrogen atmosphere and calcined in a tubular furnace at 700° C. for 2 h at a heating rate of 3° C. / min to obtain a carbonized product NHC.

[0048] Step (4): FX and NHC obtained in step (3) were mixed and dispersed in anhydrous ethanol at a mass ratio of 1:1, and ultrasonically treated for 10 minutes, and then stirred at room temperature for 4 hours. Subsequently, the mixed solution was dried with a nitrogen stream to obtain a solid powder.

[0049] Step (5): The solid powder obtained in step (4) is dispersed in a 10 wt % ethanol aqueous solution to eliminate free FX molecules, and then the final NHC-FX composite material is obtained by centrifugation, washing and vacuum freeze drying.

[0050] Step (6): chitosan, glycerol and NHC-FX composite material were added in sequence according to a mass ratio of 1:0.25:0.01, fully dissolved in a 1wt% acetic acid aqueous solution, and stirred to form a film-forming solution. After removing bubbles from the film-forming solution by ultrasonic, the solution was poured into a mold and placed in a 55°C oven for drying for 12 hours to obtain an antibacterial film (CS-NHC-FX) loaded with fucoxanthin nanomaterials.

[0051] Example 2

[0052] A method for preparing an antibacterial film loaded with fucoxanthin nanomaterials comprises the following steps:

[0053] Step (1): Under room temperature, Zn(NO3)2·6H2O and 2-methylimidazole are dissolved in anhydrous methanol in a molar ratio of 1:8 to form two solutions. 2-MIM is slowly dripped into Zn(NO3)2·6H2O to obtain a synthetic solution. Stir vigorously at 20°C for 1 hour, then centrifuge the crystal dispersion obtained after synthesis (10000rpm, 5min) to obtain a crude product, and then wash the obtained precipitate with fresh anhydrous methanol. After repeating the above centrifugation operation three times, the precipitate is placed in a constant temperature oven at 60°C and dried for 12 hours to obtain ZIF-8 crystals.

[0054] Step (2): Dissolve ZIF-8 crystals in an ethanol solution (the concentration of the ethanol solution is 90 wt%) to form a ZIF-8 ethanol solution with a concentration of 0.02 g / mL, and then mix with a tannic acid aqueous solution (7 g / L), the volume ratio of the ZIF-8 ethanol solution to the tannic acid aqueous solution being 1:5, and stir at room temperature for 0.9 h. After the precipitate is formed, wash thoroughly with deionized water and methanol for 3 times to remove impurities. Finally, dry at 60° C. under vacuum conditions for 12 h to obtain etched ZIF-8 (HZIF-8).

[0055] Step (3): The HZIF-8 obtained in step (2) is placed in a nitrogen atmosphere and calcined in a tubular furnace at 800° C. for 2 h at a heating rate of 3° C. / min to obtain a carbonized product NHC.

[0056] Step (4): FX and NHC obtained in step (3) were mixed and dispersed in ethanol at a ratio of 1:1, and ultrasonically treated for 10 mon, and stirred at room temperature for 4 hours. Subsequently, the mixed solution was dried with a nitrogen stream to obtain a solid powder.

[0057] Step (5): The solid powder obtained in step (4) is dispersed in a 10 wt% ethanol aqueous solution to eliminate free FX molecules. The final NHC-FX composite material is obtained by centrifugation, washing and vacuum freeze drying.

[0058] Step (6): chitosan, glycerol and NHC-FX composite material were added in sequence according to a mass ratio of 1:0.25:0.01, fully dissolved in a 1wt% acetic acid aqueous solution, and stirred to form a film-forming solution. After removing bubbles from the film-forming solution by ultrasonic, the solution was poured into a mold and placed in a 55°C oven for drying for 12 hours to obtain an antibacterial film (CS-NHC-FX) loaded with fucoxanthin nanomaterials.

[0059] Example 3

[0060] A method for preparing an antibacterial film loaded with fucoxanthin nanomaterials comprises the following steps:

[0061] Step (1): Under room temperature, Zn(NO3)2·6H2O and 2-methylimidazole are dissolved in anhydrous methanol in a molar ratio of 1:9 to form two solutions. 2-MIM is slowly dripped into Zn(NO3)2·6H2O to obtain a synthetic solution. The mixture is vigorously stirred at 27°C for 1h 10min, and then the crystal dispersion obtained after synthesis is centrifuged (9000rpm, 5min) to obtain a crude product, and the precipitate obtained is then washed with fresh anhydrous methanol. After repeating the above centrifugation operation three times, the precipitate is placed in a constant temperature oven at 60°C and dried for 12h to obtain ZIF-8 crystals.

[0062] Step (2): Dissolve ZIF-8 crystals in an ethanol solution (the concentration of the ethanol solution is 90 wt%) to form a ZIF-8 ethanol solution with a concentration of 0.02 g / mL, and then mix with a tannic acid aqueous solution (8 g / L), the volume ratio of the ZIF-8 ethanol solution to the tannic acid aqueous solution being 1:5, and stir at room temperature for 0.8 h. After the precipitate is formed, wash thoroughly with deionized water and methanol for 3 times to remove impurities. Finally, dry at 60° C. under vacuum conditions for 12 h to obtain etched ZIF-8 (HZIF-8).

[0063] Step (3): The HZIF-8 obtained in step (2) is placed in a nitrogen atmosphere and calcined in a tubular furnace at 800° C. for 2 h at a heating rate of 3° C. / min to obtain a carbonized product NHC.

[0064] Step (4): FX and NHC obtained in step (3) were mixed and dispersed in ethanol at a ratio of 1:1, and ultrasonically treated for 10 minutes, and then stirred at room temperature for 4 hours. Subsequently, the mixed solution was dried with a nitrogen stream to obtain a solid powder.

[0065] Step (5): The solid powder obtained in step (4) is dispersed in a 10 wt% ethanol aqueous solution to eliminate free FX molecules. The final NHC-FX composite material is obtained by centrifugation, washing and vacuum freeze drying.

[0066] Step (6): chitosan, glycerol and NHC-FX composite material were added in sequence according to a mass ratio of 1:0.25:0.01, and fully dissolved in a 1wt% acetic acid aqueous solution, and then stirred to form a film-forming solution. The film-forming solution was ultrasonically removed of bubbles, poured into a mold, and placed in a 55°C oven to dry for 12 hours to obtain an antibacterial film (CS-NHC-FX) loaded with fucoxanthin nanomaterials.

[0067] Example 4

[0068] A method for preparing an antibacterial film loaded with fucoxanthin nanomaterials comprises the following steps:

[0069] Step (1): Under room temperature, Zn(NO3)2·6H2O and 2-methylimidazole are dissolved in anhydrous methanol in a molar ratio of 1:10 to form two solutions. 2-MIM is slowly dripped into Zn(NO3)2·6H2O to obtain a synthetic solution. The mixture is vigorously stirred at 27°C for 1h 20min, and then the crystal dispersion obtained after synthesis is centrifuged (8000rpm, 5min) to obtain a crude product, and the precipitate obtained is then washed with fresh anhydrous methanol. After repeating the above centrifugation operation three times, the precipitate is placed in a constant temperature oven at 60°C and dried for 12h to obtain ZIF-8 crystals.

[0070] Step (2): Dissolve ZIF-8 crystals in an ethanol solution (the concentration of the ethanol solution is 90 wt%) to form a ZIF-8 ethanol solution with a concentration of 0.02 g / mL, and then mix with a tannic acid aqueous solution (9 g / L), the volume ratio of the ZIF-8 ethanol solution to the tannic acid aqueous solution being 1:5, and stir at room temperature for 0.5 h. After the precipitate is formed, wash thoroughly with deionized water and methanol for 3 times to remove impurities. Finally, dry at 60° C. under vacuum conditions for 12 h to obtain etched ZIF-8 (HZIF-8).

[0071] Step (3): The HZIF-8 obtained in step (2) is placed in a nitrogen atmosphere and calcined in a tubular furnace at 800° C. for 2 h at a heating rate of 3° C. / min to obtain a carbonized product NHC.

[0072] Step (4): FX and NHC obtained in step (3) were mixed and dispersed in anhydrous ethanol at a ratio of 1:2, and ultrasonically treated for 10 minutes, and then stirred at room temperature for 4 hours. Subsequently, the mixed solution was dried with a nitrogen stream to obtain a solid powder.

[0073] Step (5): The solid powder obtained in step (4) is dispersed in a 10 wt% ethanol aqueous solution to eliminate free FX molecules. The final NHC-FX composite material is obtained by centrifugation, washing and vacuum freeze drying.

[0074] Step (6): chitosan, glycerol and NHC-FX composite material were added in sequence according to a mass ratio of 1:0.25:0.02, fully dissolved in a 1wt% acetic acid aqueous solution, and stirred to form a film-forming solution. After removing bubbles from the film-forming solution by ultrasonic, the solution was poured into a mold and placed in a 65°C oven for drying for 12 hours to obtain an antibacterial film (CS-NHC-FX) loaded with fucoxanthin nanomaterials.

[0075] Example 5

[0076] A method for preparing an antibacterial film loaded with fucoxanthin nanomaterials comprises the following steps:

[0077] Step (1): Under room temperature, Zn(NO3)2·6H2O and 2-methylimidazole are dissolved in anhydrous methanol in a molar ratio of 1:10 to form two solutions. 2-MIM is slowly dripped into Zn(NO3)2·6H2O to obtain a synthetic solution. The mixture is vigorously stirred at 30°C for 1h 20min, and then the crystal dispersion obtained after synthesis is centrifuged (8000rpm, 5min) to obtain a crude product, and the obtained precipitate is then washed with fresh anhydrous methanol. After repeating the above centrifugation operation three times, the precipitate is placed in a constant temperature oven at 60°C and dried for 12h to obtain ZIF-8 crystals.

[0078] Step (2): Dissolve ZIF-8 crystals in an ethanol solution (the concentration of the ethanol solution is 90 wt%) to form a ZIF-8 ethanol solution with a concentration of 0.02 g / mL, and then mix with a tannic acid aqueous solution (10 g / L), the volume ratio of the ZIF-8 ethanol solution to the tannic acid aqueous solution being 1:5, and stir at room temperature for 0.5 h. After the precipitate is formed, wash thoroughly with deionized water and methanol for 3 times to remove impurities. Finally, dry at 60° C. under vacuum conditions for 12 h to obtain etched ZIF-8 (HZIF-8).

[0079] Step (3): The HZIF-8 obtained in step (2) is placed in a nitrogen atmosphere and calcined in a tubular furnace at 800° C. for 2 h at a heating rate of 3° C. / min to obtain a carbonized product NHC.

[0080] Step (4): FX and NHC obtained in step (3) were mixed and dispersed in anhydrous ethanol at a ratio of 1:2, and ultrasonically treated for 10 minutes, and then stirred at room temperature for 4 hours. Subsequently, the mixed solution was dried with a nitrogen stream to obtain a solid powder.

[0081] Step (5): The solid powder obtained in step (4) is dispersed in a 10 wt% ethanol aqueous solution to eliminate free FX molecules. The final NHC-FX composite material is obtained by centrifugation, washing and vacuum freeze drying.

[0082] Step (6): chitosan, glycerol and NHC-FX composite material were added in sequence according to a mass ratio of 1:0.25:0.02, fully dissolved in a 1wt% acetic acid aqueous solution, and stirred to form a film-forming solution. After removing bubbles from the film-forming solution by ultrasonic, the solution was poured into a mold and placed in a 65°C oven for drying for 12 hours to obtain an antibacterial film (CS-NHC-FX) loaded with fucoxanthin nanomaterials.

[0083] Example 6

[0084] A method for preparing an antibacterial film loaded with fucoxanthin nanomaterials comprises the following steps:

[0085] Step (1): Under room temperature, Zn(NO3)2·6H2O and 2-methylimidazole are dissolved in anhydrous methanol in a molar ratio of 1:10 to form two solutions. 2-MIM is slowly dripped into Zn(NO3)2·6H2O to obtain a synthetic solution. The mixture is vigorously stirred at 30°C for 1h 20min, and then the crystal dispersion obtained after synthesis is centrifuged (8000rpm, 5min) to obtain a crude product, and the obtained precipitate is then washed with fresh anhydrous methanol. After repeating the above centrifugation operation three times, the precipitate is placed in a constant temperature oven at 60°C and dried for 12h to obtain ZIF-8 crystals.

[0086] Step (2): Dissolve ZIF-8 crystals in an ethanol solution (the concentration of the ethanol solution is 90 wt%) to form a ZIF-8 ethanol solution with a concentration of 0.02 g / mL, and then mix with a tannic acid aqueous solution (11 g / L), the volume ratio of the ZIF-8 ethanol solution to the tannic acid aqueous solution being 1:5, and stir at room temperature for 0.5 h. After the precipitate is formed, wash thoroughly with deionized water and methanol for 3 times to remove impurities. Finally, dry at 60° C. under vacuum conditions for 12 h to obtain etched ZIF-8 (HZIF-8).

[0087] Step (3): The HZIF-8 obtained in step (2) is placed in a nitrogen atmosphere and calcined in a tubular furnace at 800° C. for 2 h at a heating rate of 3° C. / min to obtain a carbonized product NHC.

[0088] Step (4): FX and NHC obtained in step (3) were mixed and dispersed in anhydrous ethanol at a ratio of 1:2, and ultrasonically treated for 10 minutes, and then stirred at room temperature for 4 hours. Subsequently, the mixed solution was dried with a nitrogen stream to obtain a solid powder.

[0089] Step (5): The solid powder obtained in step (4) is dispersed in a 10 wt% ethanol aqueous solution to eliminate free FX molecules. The final NHC-FX composite material is obtained by centrifugation, washing and vacuum freeze drying.

[0090] Step (6): chitosan, glycerol and NHC-FX composite material were added in sequence according to a mass ratio of 1:0.25:0.02, fully dissolved in a 1wt% acetic acid aqueous solution, and stirred to form a film-forming solution. After removing bubbles from the film-forming solution by ultrasonic, the solution was poured into a mold and placed in a 65°C oven for drying for 12 hours to obtain an antibacterial film (CS-NHC-FX) loaded with fucoxanthin nanomaterials.

[0091] Example 7

[0092] A method for preparing an antibacterial film loaded with fucoxanthin nanomaterials comprises the following steps:

[0093] Step (1): Under room temperature, Zn(NO3)2·6H2O and 2-methylimidazole are dissolved in anhydrous methanol in a molar ratio of 1:10 to form two solutions. 2-MIM is slowly dripped into Zn(NO3)2·6H2O to obtain a synthetic solution. The mixture is vigorously stirred at 37°C for 1h 20min, and then the crystal dispersion obtained after synthesis is centrifuged (8000rpm, 5min) to obtain a crude product, and the precipitate obtained is then washed with fresh anhydrous methanol. After repeating the above centrifugation operation three times, the precipitate is placed in a constant temperature oven at 60°C and dried for 12h to obtain ZIF-8 crystals.

[0094] Step (2): Dissolve ZIF-8 crystals in an ethanol solution (the concentration of the ethanol solution is 90 wt%) to form a ZIF-8 ethanol solution with a concentration of 0.02 g / mL, and then mix with a tannic acid aqueous solution (12 g / L), the volume ratio of the ZIF-8 ethanol solution to the tannic acid aqueous solution being 1:5, stir at room temperature for 0.5 h, and after the precipitate is formed, wash thoroughly with deionized water and methanol for 3 times to remove impurities. Finally, dry at 60° C. under vacuum conditions for 12 h to obtain etched ZIF-8 (HZIF-8).

[0095] Step (3): The HZIF-8 obtained in step (2) is placed in a nitrogen atmosphere and calcined in a tubular furnace at 800° C. for 2 h at a heating rate of 3° C. / min to obtain a carbonized product NHC.

[0096] Step (4): FX and NHC obtained in step (3) were mixed and dispersed in anhydrous ethanol at a ratio of 1:2, and ultrasonically treated for 10 minutes, and then stirred at room temperature for 4 hours. Subsequently, the mixed solution was dried with a nitrogen stream to obtain a solid powder.

[0097] Step (5): The solid powder obtained in step (4) is dispersed in a 10 wt% ethanol aqueous solution to eliminate free FX molecules. The final NHC-FX composite material is obtained by centrifugation, washing and vacuum freeze drying.

[0098] Step (6): chitosan, glycerol and NHC-FX composite material were added in sequence according to a mass ratio of 1:0.25:0.02, fully dissolved in a 1wt% acetic acid aqueous solution, and stirred to form a film-forming solution. After removing bubbles from the film-forming solution by ultrasonic, the solution was poured into a mold and placed in a 65°C oven for drying for 12 hours to obtain an antibacterial film (CS-NHC-FX) loaded with fucoxanthin nanomaterials.

[0099] Comparative Example 1

[0100] A method for preparing an antibacterial film comprises the following steps:

[0101] Chitosan and glycerol were added in a mass ratio of 1:0.25, fully dissolved in a 1wt% acetic acid aqueous solution, and stirred to form a film-forming solution. The film-forming solution was ultrasonically debubbled, poured into a mold, and dried in an oven at 55°C for 12 hours to obtain a film CS.

[0102] Comparative Example 2

[0103] A method for preparing an antibacterial film comprises the following steps:

[0104] Steps (1) to (3): Same as in Example 1;

[0105] Step (4): chitosan, glycerol and NHC were added in sequence according to a mass ratio of 1:0.25:0.02, and after being fully dissolved in a 1wt% acetic acid aqueous solution, they were stirred evenly to prepare a film-forming solution. The film-forming solution was ultrasonically removed of bubbles, poured into a mold, and placed in a 55°C oven to dry for 12 hours to obtain a composite film CS-NHC.

[0106] Comparative Example 3

[0107] A method for preparing an antibacterial film comprises the following steps:

[0108] Chitosan, glycerol and FX were added in sequence according to a mass ratio of 1:0.25:0.02, fully dissolved in a 1wt% acetic acid aqueous solution, and stirred evenly to form a film-forming solution. After the film-forming solution was ultrasonically removed of bubbles, it was poured into a mold and placed in a 55°C oven to dry for 12 hours to obtain a composite film CS-FX.

[0109] Test example:

[0110] 1. Preparation and characterization of the synthetic material of the present invention

[0111] Example 1 The microstructure of the materials prepared at different synthesis stages was verified by TEM ( Figure 2 ), it can be seen that ZIF-8 presents uniform dodecahedral particles, and after acid etching, it changes from micropores to hollow mesoporous structures (HZIF-8), and then after high-temperature carbonization, HZIF-8 loses its sharp edges and corners, but completely retains a clear hollow structure (NHC). The morphology of NHC does not change significantly before and after the addition of FX, which shows that NHC-FX in the present invention has excellent stability.

[0112] 2. Surface and cross-sectional SEM images of the composite membrane of the present invention

[0113] Figure 3 The SEM images of the composite membranes prepared in Example 1 and Comparative Examples 1-3 show that the hydrophobic self-aggregation of FX leads to partial protrusions and cracks on the membrane surface and inside, and the good water dispersibility of NHC improves the distribution of NHC-FX in the membrane matrix. It can be seen that in the present invention, the addition of NHC-FX material does not affect the smooth morphology of the composite membrane.

[0114] 3. Test on the anti-ultraviolet effect of the composite film of the present invention

[0115] Ultraviolet radiation (200-400nm) is one of the important factors that cause food to deteriorate, so research on anti-ultraviolet radiation is very necessary. The films (pure CS, CS-NHC, CS-FX prepared in Comparative Examples 1-3 and CS-NHC-FX prepared in Example 1) were cut into 4cm×1cm films and tested at 200-800nm ​​using a UV-visible spectrophotometer.

[0116] like Figure 4 The UV-visible spectrum of the composite film is shown. Compared with the pure CS film, the UV light transmittance of the CS-NHC-FX film tends to decrease, and it has a certain UV blocking ability. At the same time, the transmittance at 600-800nm ​​is still maintained at about 50%. At the same time, the light source is one of the most important factors in photodynamic sterilization. Therefore, the composite film CS-NHC-FX film of the present invention has good light transmittance within the range of photodynamic action.

[0117] 4. Test on the antibacterial effect of the composite film of the present invention

[0118] Two representative bacteria, Escherichia coli and Staphylococcus aureus, were selected and the antibacterial ability of the composite film (CS-NHC-FX prepared in Example 1) against them was measured by plate count method. First, the film cut into 8 mm was irradiated with ultraviolet light for 30 minutes to remove the bacteria on the surface. Then, the bacterial suspension (1×10 6CFU / mL) and centrifuged, discarded the supernatant, resuspended the precipitate with PBS, and placed it in a 1.5 mL centrifuge tube with the CS-NHC-FX membrane under a 300 W xenon lamp (100 mW / cm 2 ) irradiated for 0, 5, 10, 15, 20, and 25 min. Then 100 μL of bacterial solution was spread on solid LB agar medium and incubated in a constant temperature incubator at 37°C for 12 h for counting.

[0119] Figure 5 The antibacterial test results of the film are shown in Table 2. Figure 5 It can be seen that the antibacterial effect of CS-NHC-FX membrane on E. coli and S. aureus shows a positive correlation with the extension of time, and the two bacteria are gradually killed with the increase of irradiation time. When the irradiation time is 25 minutes, the killing rate reaches> 99%, and thereafter, extending the irradiation time has no significant effect on the killing rate. It can be seen that the composite membrane of the present invention has excellent antibacterial effect under 25 minutes of irradiation time.

[0120] Figure 6 The results of antibacterial tests of different films under the same irradiation time are shown in Figure 2. It is not difficult to find that the CS-NHC-FX film group has the highest killing rate against Escherichia coli and Staphylococcus aureus under visible light irradiation, reaching 98.85% and 98.78% respectively. This significant bactericidal ability is the result of the synergistic effect of the inherent antibacterial properties of CS and the excellent photodynamic antibacterial activity of NHC-FX. It can be seen that compared with the composite film of the control case, the composite film of the present invention has excellent antibacterial effect.

[0121] The embodiments provided above are not intended to limit the scope of the present invention, and the steps described are not intended to limit the execution order thereof. Those skilled in the art may make obvious improvements to the present invention in combination with existing common knowledge, which also fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for preparing an antibacterial film loaded with fucoxanthin nanomaterials, characterized in that: The steps include: (1) Zn(NO3)2·6H2O reacts with 2-methylimidazole to prepare ZIF-8 crystals; (2) dissolving ZIF-8 crystals in an ethanol solution to form a ZIF-8 ethanol solution, and then reacting with a tannic acid aqueous solution to obtain an etched ZIF-8, i.e., HZIF-8; (3) HZIF-8 is calcined at high temperature to obtain a carbonized product NHC, which is then compounded with fucoxanthin FX to obtain an NHC-FX composite material; (4) Chitosan, glycerol and NHC-FX composite materials are mixed and dissolved in an acetic acid aqueous solution to prepare a film-forming solution, which is then formed into a film in a mold to obtain an antibacterial film loaded with fucoxanthin nanomaterials.

2. The preparation method according to claim 1, characterized in that: In step (1), the molar ratio of Zn(NO3)2·6H2O to 2-methylimidazole is 1:8-1:10; and the reaction conditions are: 20-37°C, 1-2h.

3. The preparation method according to claim 1, characterized in that: In step (2), the concentration of the ZIF-8 ethanol solution is 0.02 g / mL; the volume ratio of the ZIF-8 ethanol solution to the tannic acid aqueous solution is 1:5; and the concentration of the tannic acid aqueous solution is 6 to 12 g / L.

4. The preparation method according to claim 1, characterized in that: In step (2), the reaction conditions are: stirring at room temperature for 0.5 to 1 hour; after the reaction is completed, the precipitate is washed with deionized water and methanol, centrifuged, and vacuum dried.

5. The preparation method according to claim 1, characterized in that: In step (3), the high temperature calcination conditions are: calcination at 700-900° C. for 1.5-2 h in a nitrogen atmosphere; the mass ratio of FX to NHC is 1:1-4.

6. The preparation method according to claim 1, characterized in that: In step (3), FX and NHC are mixed and dispersed in anhydrous ethanol, ultrasonically treated for 10 minutes, stirred at room temperature, and blown dry with a nitrogen stream to obtain a solid powder; then the solid powder is dispersed in a 10wt% ethanol aqueous solution, centrifuged, washed and vacuum freeze-dried to obtain an NHC-FX composite material.

7. The preparation method according to claim 1, characterized in that: In step (4), the volume concentration of the acetic acid aqueous solution is 1%.

8. The preparation method according to claim 1, characterized in that: In step (4), the mass ratio of chitosan, glycerol and NHC-FX composite material is 1:0.25:0.01-0.

02.

9. The preparation method according to claim 1, characterized in that: In step (4), the film-forming liquid is ultrasonically removed from bubbles before film formation in the mold, and then poured into the mold; the film-forming conditions are: 50-75° C., 6-12 h.

10. An antibacterial film loaded with fucoxanthin nanomaterials prepared by the method according to any one of claims 1 to 9.

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