Chitosan and gelatin antibacterial antioxidant composite packaging film loaded with ZCDG nanoparticles and preparation method and application of chitosan and gelatin antibacterial antioxidant composite packaging film loaded with ZCDG nanoparticles

Abstract

The invention relates to a ZCDG nanoparticle-loaded chitosan and gelatin antibacterial antioxidant composite packaging film as well as a preparation method and application thereof, and belongs to the technical field of novel bio-based polymer composite materials. The preparation method of the composite packaging film comprises the following steps: (1) weighing chitosan CS, dissolving in an acetic acid-deionized water mixed solution, adding a plasticizer, and uniformly stirring to obtain a solution A; (2) weighing gelatin Gel, dissolving in deionized water, heating and stirring to obtain a solution B; (3) mixing the solution A and the solution B, heating and stirring to obtain a solution C; (4) dissolving ZCDG nanoparticles in water to obtain a solution D; and (5) adding the solution D into the solution C, ultrasonically stirring uniformly, pouring into a mold, and drying. The composite packaging film has excellent performances of good flexibility, oxidation resistance, antibacterial activity, thermal stability, biocompatibility, environmental protection, degradability and the like.

Description

Technical Field

[0001] The present application relates to the technical field of novel bio-based polymer composite materials, and in particular to a chitosan and gelatin antibacterial and antioxidant composite packaging film loaded with ZCDG nanoparticles, and a preparation method and application thereof. Background Art

[0002] Solution casting is an important method for preparing multifunctional composite films. By manipulating the rheological properties of the film-forming matrix and the dispersion state of the functional components, composite films with dense three-dimensional networks can be constructed. This technology offers advantages such as simplicity, the absence of complex equipment, and scalability, making it particularly suitable for constructing composite systems of nanoparticles and biopolymers.

[0003] Chitosan is a natural cationic polysaccharide. The amino groups on its molecular chain give it excellent antibacterial activity and good film-forming and biodegradability. Gelatin, as a hydrolyzed product of collagen, has temperature-responsive gelation properties and can form an interpenetrating network structure with chitosan through electrostatic interactions. The three-dimensional network formed by the two not only has an ideal mechanical support function, but also provides abundant binding sites for the loading of nanoparticles.

[0004] ZCDG nanoparticles are functional particles prepared from natural active ingredients through methods such as antisolvent precipitation and self-assembly. Their abundant surface active groups significantly enhance their free radical scavenging ability and exert broad-spectrum antibacterial effects by disrupting the integrity of microbial cell membranes. When embedded in a chitosan-gelatin three-dimensional network, ZCDG nanoparticles not only improve the film's mechanical properties through physical filling, but also produce a synergistic antibacterial effect with chitosan.

[0005] Existing research mostly focuses on the addition of a single antimicrobial agent or antioxidant, but there are few reports on simultaneously improving the physical barrier properties and biological activity of films through nanoparticle structure design. Summary of the Invention

[0006] In view of this, the present application provides a chitosan and gelatin antibacterial and antioxidant composite packaging film loaded with ZCDG nanoparticles, and its preparation method and application. The composite packaging film has excellent properties such as good flexibility, antioxidant, antibacterial, thermal stability, biocompatibility and environmental degradation, and can effectively overcome the defects of the above-mentioned prior art.

[0007] The first aspect of the present application provides a method for preparing a chitosan and gelatin antibacterial and antioxidant composite packaging film loaded with ZCDG nanoparticles, comprising the following steps:

[0008] (1) Chitosan CS was weighed and dissolved in a mixed solution of acetic acid and deionized water, and then a plasticizer was added and stirred to obtain solution A;

[0009] (2) Weigh gelatin Gel and dissolve it in deionized water, heat and stir to obtain solution B;

[0010] (3) mixing solution A and solution B, heating and stirring to obtain solution C;

[0011] (4) dissolving ZCDG nanoparticles in water to obtain solution D;

[0012] (5) Solution D was added to solution C, and after ultrasonic stirring, the mixture was poured into a mold and dried to obtain a chitosan and gelatin antibacterial and antioxidant composite packaging film loaded with ZCDG nanoparticles.

[0013] Given that ZCDG nanoparticles have unique advantages in regulating the microstructure of thin films: on the one hand, their nano-size effect can reduce the porosity of the matrix and improve the water vapor barrier; on the other hand, the surface active groups can form hydrogen bonds with the polymer chains to cross-link and enhance the tensile strength of the film. Therefore, the present application constructs a ZCDG nanoparticle / chitosan / gelatin ternary composite system by solution casting, which combines the natural antibacterial properties of chitosan, the film-forming processability of gelatin and the strong antioxidant properties of ZCDG nanoparticles. During the film formation process, the nanoparticles can be evenly distributed in the gaps of the polymer network. Compared with the traditional physical blending method, the preparation process of the present application can effectively avoid the agglomeration of nanoparticles, give full play to their surface effect and small size effect, so that the film has good biocompatibility, good mechanical properties and flexibility, and at the same time has multiple functions such as anti-oxidation, antibacterial, and anti-ultraviolet. It is a composite fresh-keeping composite packaging film, which is of great significance in the field of food preservation.

[0014] Preferably, the preparation of the ZCDG nanoparticles comprises the following steps:

[0015] S1, dissolving curcumin Cur and zein Zein in an ethanol-water mixed solution, stirring to form a uniform mixed solution, adding the mixed solution dropwise into deionized water, and stirring to obtain a ZC NPs solution;

[0016] S2, adding the dihydroquercetin DHQ solution dropwise to the ZC NPs solution and stirring to obtain a ZCD NPs solution;

[0017] S3, dissolving gum arabic GA in deionized water and adjusting the pH to 5 to obtain a gum arabic GA solution, slowly adding the ZCDG NPs solution to the gum arabic GA solution and stirring to obtain a ZCDG NPs solution;

[0018] S4. The ZCDG NPs solution was centrifuged and purified to remove uncoated components, and the supernatant was freeze-dried to obtain ZCDG nanoparticles.

[0019] Preferably, in step S1, the volume ratio of ethanol to water in the mixed solution of ethanol and water is 7:3.

[0020] Preferably, the mass ratio of curcumin Cur, zein, dihydroquercetin DHQ and gum arabic GA is 0.05:0.5:0.01:0.08.

[0021] Preferably, the mass ratio of chitosan CS to gelatin Gel is 2:3.

[0022] Preferably, in step (1), the volume ratio of acetic acid to deionized water in the mixed solution of acetic acid and deionized water is 1:99.

[0023] Preferably, in step (1), the plasticizer is glycerol, and the addition amount of glycerol is 30% of the mass of chitosan.

[0024] Preferably, in step (5), the stirring time is 1h, and the ultrasonic time is 5min; the drying temperature is 50℃, and the drying time is 12h.

[0025] The second aspect of the present application also provides a chitosan and gelatin composite packaging film loaded with ZCDG nanoparticles, which is prepared by the above method.

[0026] The third aspect of the present application also provides the application of the above-mentioned chitosan and gelatin composite packaging film loaded with ZCDG nanoparticles in the field of food packaging materials and the field of biomedicine.

[0027] Compared with the prior art, the present application has the following beneficial effects:

[0028] 1. The preparation method of the present application first embeds zein on curcumin, then adds dihydroquercetin to adsorb on the surface of zein, and finally embeds with gum arabic, which enhances the stability of the nanoparticles and increases the water solubility of the raw materials, thereby improving the water insolubility of the raw materials; in addition, the introduction of curcumin and dihydroquercetin enhances the antioxidant and antibacterial activities of the composite packaging film, and the two have a synergistic effect; the nanoparticles are added to the chitosan and gelatin composite film to fill the space network structure, forming a CS\Gel-ZCDG-NPs composite film.

[0029] 2. The chitosan and gelatin composite packaging film loaded with ZCDG nanoparticles prepared by the present application has good flexibility, antioxidant, antibacterial, thermal stability, biocompatibility, light transmittance and environmental protection and biodegradability, and can be widely applied in the field of food packaging materials.

[0030] 3. The reaction conditions of the preparation method of the present application are room temperature, the required equipment is simple, the operation is easy, the production efficiency is high, and the controllability is strong; the preparation conditions of the ZCDG nanoparticles of the present application are simple, and the synthesized nanoparticles are small and stable; the preparation method of the present application provides a high content of ZCDG nanoparticles for the composite film system, so that the three-dimensional network structure formed between gelatin and chitosan is filled, thereby enhancing the physical and mechanical properties of the film and giving the film good antibacterial and antioxidant properties. The present application constructs a new multifunctional antioxidant and antibacterial composite film integrating multiple functional components by blending the synthesized nanoparticles with a gel system; the chitosan and gelatin composite packaging film loaded with ZCDG nanoparticles prepared in the present application has good biocompatibility and acceptability, and has a wide range of application prospects as a food packaging material. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the present application or the prior art, the following briefly introduces the drawings required for use in the description of the present application or the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0032] Figure 1 (A) is a scanning electron micrograph of the freeze-dried powder of ZCDG nanoparticles obtained in Example 1. Figure 1 (B) is a transmission electron microscopy image of the freeze-dried powder of ZCDG nanoparticles obtained in Example 1. Figure 1 (C) Zeta potential, particle size, and PDI of the ZCDG nanoparticle solution prepared in Example 1;

[0033] Figure 2 Scanning electron micrographs of the surface and cross-section of the CS\Gel-ZCDG NPs composite packaging films prepared in Examples 2-5 and the film prepared in Comparative 1;

[0034] Figure 3 (A) is a stress-strain curve diagram of the chitosan and gelatin composite packaging films loaded with ZCDG nanoparticles prepared in Examples 2-5 and the film prepared in Comparative 1, Figure 3 (B) is a graph of the elastic modulus of the chitosan and gelatin composite packaging films loaded with ZCDG nanoparticles prepared in Examples 2-5 and the film prepared in Comparative 1, Figure 3 (C) is a graph showing the tensile strength of the chitosan and gelatin composite packaging films loaded with ZCDG nanoparticles prepared in Examples 2-5 and the film prepared in Comparative 1. Figure 3 (D) is a graph of the elongation at break of the chitosan and gelatin composite packaging films loaded with ZCDG nanoparticles prepared in Examples 2-5 and the film prepared in Comparative 1;

[0035] Figure 4 DPPH free radical and ABTS free radical scavenging rate graphs of the ZCDG nanoparticle-loaded chitosan and gelatin composite packaging films prepared in Examples 2-5 and the film prepared in Comparative 1;

[0036] Figure 5 (A) is a plate colony count diagram of the chitosan and gelatin composite packaging films loaded with ZCDG nanoparticles prepared in Examples 2-5 and the film prepared in Comparative 1, Figure 5 (B) is a graph showing the inhibition rate of the chitosan and gelatin composite packaging films loaded with ZCDG nanoparticles prepared in Examples 2-5 and the film prepared in Comparative 1 on Escherichia coli (E. coli). Figure 5 (C) is a graph showing the inhibition rate of the chitosan and gelatin composite packaging films loaded with ZCDG nanoparticles prepared in Examples 2-5 and the film prepared in Comparative 1 against Staphylococcus aureus (S. aureus);

[0037] Figure 6 The UV transmittance graphs of the ZCDG nanoparticle-loaded chitosan and gelatin composite packaging films prepared in Examples 2-5 and the film prepared in Comparative 1;

[0038] Figure 7 The blood compatibility diagram of the chitosan and gelatin composite packaging films loaded with ZCDG nanoparticles prepared in Examples 2-5 and the film prepared in Comparative 1;

[0039] Figure 8 This is a differential thermal scanning diagram of the chitosan and gelatin composite packaging films loaded with ZCDG nanoparticles prepared in Examples 2-5 and the film prepared in Comparative 1. DETAILED DESCRIPTION

[0040] To make the objectives, technical solutions, and advantages of this application more clear, the technical solutions of this application will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments of this application, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of this application.

[0041] Unless otherwise specified, the experimental methods used in the examples of this application are all conventional methods.

[0042] In the following examples and comparative examples, unless otherwise specified, all raw materials can be purchased commercially or prepared by conventional methods.

[0043] Example 1

[0044] (1) 0.05 g of curcumin (Cur) and 0.5 g of zein (Zein) were weighed and dissolved in a mixed solution of 35 mL of ethanol and 15 mL of deionized water, and stirred to form a uniform mixture; 20 mL of the above solution was added dropwise into 60 mL of deionized water and stirred at 600 rpm for 6 h to obtain ZC NPs solution; then, 0.01 g of dihydroquercetin (DHQ) was dissolved in 10 mL of anhydrous ethanol solution and then added dropwise to the ZC NPs solution and stirred at 600 rpm for 1 h to obtain ZCD NPs solution; finally, 0.08 g of gum arabic (GA) was dissolved in 40 mL of deionized water and the pH was adjusted to 5. 90 mL of the above ZCD NPs solution was slowly added to 40 mL of gum arabic (GA) solution and stirred at 600 rpm for 1 h to obtain ZCDG NPs solution; then centrifuged at 6,000r for 10min to purify and remove uncoated components, and the supernatant was freeze-dried to obtain ZCDG NPs powder.

[0045] (2) The ZCDG NPs powder obtained after freeze-drying was observed by scanning electron microscopy and photographed at 25,000× magnification. Figure 1 (A) shown.

[0046] (3) The ZCDG NPs powder obtained after freeze-drying was observed by transmission electron microscopy. Figure 1 (B) shown.

[0047] (4) The supernatant of the ZCDGNPs solution after centrifugation was taken to measure the Zeta potential, particle size and polydispersity index (PDI). The results are as follows: Figure 1 (C) shown.

[0048] Depend on Figure 1 (A) It can be seen that most of the nanoparticles are spherical, with a relatively regular shape, a relatively smooth surface, and a relatively uniform distribution. Some particles have a certain degree of agglomeration. Figure 1 (B) It can be seen that the nanoparticles have clear outlines, relatively smooth edges, and obvious core-shell structures. Figure 1 (C) It can be seen that the average diameter of the nanoparticles is 287.1 nm, and the PDI is 0.24, indicating that the particle size distribution of the nanoparticles is relatively narrow and the particle size in the system is relatively uniform; the Zeta potential is -34.6 mV, indicating that the surface of the nanoparticles has a negative charge; at the same time, the absolute value of the Zeta potential is greater than 30 mV, which means that there is a strong electrostatic repulsion between the particles, which can effectively prevent particle agglomeration and maintain the stability of the system.

[0049] Example 2

[0050] (1) Preparation of ZCDG nanoparticles:

[0051] 0.05 g of curcumin (Cur) and 0.5 g of zein (Zein) were weighed and dissolved in a mixed solution of 35 mL of ethanol and 15 mL of deionized water, and stirred to form a uniform mixture; 20 mL of the above solution was added dropwise to 60 mL of deionized water and stirred at 600 rpm for 6 h to obtain ZC NPs solution; then, 0.01 g of dihydroquercetin (DHQ) was dissolved in 10 mL of anhydrous ethanol solution and then added dropwise to the ZC NPs solution and stirred at 600 rpm for 1 h to obtain ZCD NPs solution; finally, 0.08 g of gum arabic (GA) was dissolved in 40 mL of deionized water and the pH was adjusted to 5. The above 90 mL of ZCD NPs solution was slowly added to 40 mL of gum arabic (GA) solution and stirred at 600 rpm for 1 h to obtain ZCDG NPs solution; then centrifuged at 6,000r for 10min to purify and remove uncoated components, and the supernatant was freeze-dried to obtain ZCDG NPs powder.

[0052] (2) Preparation of chitosan and gelatin mixed solution:

[0053] Weigh 2 g of chitosan (CS) and dissolve it in a mixed solution of 1 mL of acetic acid and 99 mL of deionized water. Then add 0.6 g of glycerol and stir until uniform. Weigh 3 g of gelatin (Gel) and dissolve it in 100 mL of deionized water. Stir at 50°C until dissolved. Mix the above two solutions in a 1:1 ratio and stir at 50°C for 2 h to obtain a uniform solution.

[0054] (3) Preparation of antibacterial and antioxidant composite packaging films of chitosan and gelatin loaded with ZCDG nanoparticles:

[0055] 0.01 g (0.5 mg / mL) of freeze-dried ZCDG NPs powder was weighed and redissolved in water, and then added to 20 mL of chitosan and gelatin mixed solutions respectively. After stirring for 1 hour, ultrasonication was performed for 5 minutes to make it evenly dispersed. Then, it was poured into a mold and dried at 50°C for 12 hours to obtain a chitosan and gelatin antibacterial and antioxidant composite packaging film loaded with ZCDG nanoparticles, which was named CS\Gel-NPs-0.5.

[0056] Example 3

[0057] The antibacterial and antioxidant composite packaging film of chitosan and gelatin loaded with ZCDG nanoparticles in this embodiment and its preparation method can refer to Example 2, except that the addition amount of ZCDG NPs powder is 0.02 g (1.0 mg / mL), and it is named CS\Gel-NPs-1.0.

[0058] Example 4

[0059] The antibacterial and antioxidant composite packaging film of chitosan and gelatin loaded with ZCDG nanoparticles in this embodiment and its preparation method can refer to Example 2, except that the addition amount of ZCDG NPs powder is 0.03 g (1.5 mg / mL), and it is named CS\Gel-NPs-1.5.

[0060] Example 5

[0061] The antibacterial and antioxidant composite packaging film of chitosan and gelatin loaded with ZCDG nanoparticles in this embodiment and its preparation method can refer to Example 2, except that the addition amount of ZCDG NPs powder is 0.04 g (2.0 mg / mL), and it is named CS\Gel-NPs-2.0.

[0062] Comparative Example 1

[0063] The chitosan and gelatin composite packaging film and its preparation method of this comparative example can refer to Example 2, except that the addition amount of ZCDG NPs powder is 0 g, and it is named CS\Gel.

[0064] Test Case

[0065] The surfaces and cross-sections of the CS\Gel-ZCDG NPs composite packaging films prepared in Examples 2-5 and the film prepared in Comparative 1 were observed using a scanning electron microscope.

[0066] Scanning electron microscope test: Cut the above five composite packaging films into appropriate sizes, stick them on the conductive adhesive and spray gold, then observe them on the machine. The results are as follows Figure 2 shown.

[0067] Figure 2 For scanning electron microscopy images, Figure 2 It can be seen that the surface of the CS\Gel film is relatively smooth and flat. As the nanoparticle loading increases from 0.5 to 2.0, the surface of the CS\Gel-NPs series films gradually becomes rough, and a discretely distributed granular structure appears, indicating that the nanoparticles are successfully loaded onto the gel surface. The higher the loading, the more obvious the surface granular structure; the cross-section shows a relatively uniform structure without stratification or special phase separation, indicating that the internal structure of the gel is dense and uniform.

[0068] 1. Mechanical properties tests were performed on the five composite packaging films prepared in Examples 2-5 and Comparative Example 1.

[0069] Mechanical properties test: The mechanical properties of the film were evaluated according to ASTM D882. The film was cut into rectangles (15×70 mm), and the distance between the clamp and the crosshead was set to 20 mm and 1 mm / s respectively. Each group of samples was tested 5 times. The results are as follows: Figure 3 shown.

[0070] Figure 3 (A) is the stress-strain curve, through Figure 3 (A) As can be seen, the pure CS\Gel film has a weak ability to withstand stress and is more susceptible to deformation and failure. As the nanoparticle loading increases, the stress-strain curve shifts upward, indicating that the composite gel's ability to resist deformation is enhanced. This demonstrates that the addition of nanoparticles effectively enhances the mechanical strength of the gel material, and the higher the loading, the more pronounced the enhancement.

[0071] Figure 3 (B) is the elastic modulus diagram, through Figure 3 (B) It can be seen that the elastic modulus of the pure CS\Gel film is the lowest, indicating that the pure gel material has poor elasticity and is not easy to recover to its original state under the action of external force; the nanoparticle loading amount is positively correlated with the elastic modulus. The introduction of nanoparticles enhances the elasticity of the material and is conducive to the material returning to its original state after being subjected to force.

[0072] Figure 3 (C) is the tensile strength diagram, through Figure 3 (C) It can be seen that the pure CS\Gel film has the lowest tensile strength, indicating that its ability to resist tensile failure is weak; the tensile strength of the CS\Gel-NPs-0.5 film to the CS\Gel-NPs-2.0 film gradually increases, and the CS\Gel-NPs-2.0 film reaches the highest. This shows that increasing the nanoparticle loading can effectively improve the tensile strength of the gel material, making the material more able to withstand tensile external forces without being destroyed.

[0073] Figure 3 (D) is the elongation at break diagram, Figure 3 (D) It can be seen that CS\Gel has the highest elongation at break, indicating that the pure gel material can undergo a large deformation before fracture; as the nanoparticle loading increases, the elongation at break gradually decreases, indicating that the addition of nanoparticles reduces the deformation ability of the material before fracture. This may be because the nanoparticles play a reinforcing and rigidifying role in the gel, making the material more prone to brittle fracture.

[0074] 2. Antioxidant performance test of the five composite packaging films prepared in Examples 2-5 and Comparative Example 1

[0075] DPPH radical scavenging ability test: 10 mg of different composite films were weighed and dissolved in 10 mL of anhydrous ethanol to prepare a 1 mg / mL film sample solution. 2 mL of sample was mixed with 2 mL of 0.1 mM DPPH dissolved in anhydrous ethanol, 2 mL of sample solution was mixed with 2 mL of anhydrous ethanol solution, and the absorbance of 2 mL of anhydrous ethanol solution and 2 mL of DPPH solution was measured to make them fully mixed and stored in the dark for 40 minutes. The DPPH radical scavenging ability of the composite packaging film was calculated by the absorbance at 517 nm. The specific results are shown in Figure 4 .

[0076] ABTS free radical scavenging ability test: ABTS (0.0384g) and K2S2O8 (0.0134g) were dissolved in 10mL of deionized water to obtain ABTS and K2S2O8 solutions respectively. The two reagents were then mixed in a 1:1 ratio and kept away from light for 12 hours. The mixture was diluted with PBS at pH = 7.4 to an absorbance of 0.70±0.02, i.e., the ABTS working solution. 10mg of different composite films were weighed and dissolved in anhydrous ethanol as sample solution. 0.8mL of ABTS working solution and 0.2mL of anhydrous ethanol were mixed and shaken for 10s, allowed to stand for 6min, and A1 was measured at 734nm. 0.8mL of ABTS working solution and 0.2mL of sample solution were mixed and shaken for 10s, allowed to stand for 6min, and A2 was measured at 734nm. The calculation formula is: ABTS scavenging rate (%) = (A1-A2) / A1×100%. For specific results, see Figure 4 .

[0077] Figure 4 This is the antioxidant effect test chart, Figure 4 It can be seen that the pure CS\Gel film itself has weak ability to scavenge DPPH free radicals and also has limited ability to scavenge ABTS free radicals. However, after the addition of nanoparticles, the DPPH antioxidant activity gradually increased and the ABTS antioxidant activity gradually increased, and both showed significant differences. This shows that the introduction of nanoparticles and the increase in loading amount can effectively improve the antioxidant properties of the material.

[0078] 3. Antibacterial performance test of the five composite packaging films prepared in Examples 2-5 and Comparative Example 1

[0079] Test of film antibacterial rate: The antibacterial effect of the film on Escherichia coli and Staphylococcus aureus was determined by the dilution coating plate method. In this test, physiological saline was selected as the blank control (Control). 20 mg of film solution was weighed and mixed with 400 μL of physiological saline, and then 100 μL of 10 8 CFU / mL of bacterial solution was allowed to react for at least 30 min. After the reaction was complete, 500 μL of physiological saline was added to make the concentration 10 7CFU / mL, then sequentially diluted to 10 3 CFU / mL. 500 μL of the bacterial suspension was inoculated onto the plate for spreading, then cultured in a 37℃ incubator for 12-15h, and the number of colonies growing on the plate was counted. The calculation formula was: the antibacterial rate (%) = (T0-T i ) / T0x100%, wherein, T0and T i represent the number of visible colonies in the control group and the film group, respectively. The specific results are shown in Figure 5 .

[0080] Figure 5 Figure is the antibacterial effect test diagram, through Figure 5 (A) it can be seen that for E. coli and S. aureus, the number of colonies on the plate in the control group is large and densely distributed, indicating that under the condition of no treatment, both bacteria can grow and reproduce normally. After CS / Gel treatment, the number of colonies of the two bacteria on the plate is reduced, which is due to the antibacterial property of chitosan itself, but the antibacterial ability is limited; after adding nanoparticles, the number of colonies in the CS / Gel-NPs-2.0 treatment group is the least, indicating that the addition of nanoparticles significantly enhances the antibacterial effect of the gel material, and the higher the loading amount, the stronger the antibacterial effect. In addition, through Figure 5 (B) and Figure 5 (C) it can be seen that the loading amount of nanoparticles is positively correlated with the antibacterial performance against E. coli, and at the same time, the increase of the loading amount of nanoparticles can effectively improve the antibacterial ability against S. aureus.

[0081] 4. The light transmittance of the five composite packaging films prepared in Examples 2-5 and Comparative Example 1 was tested

[0082] Light transmittance test: the above five packaging films were cut into 1.0 cm x 5.0 cm, placed in a quartz cuvette, and scanned in the range of 200-800 nm using a UV spectrophotometer. The calculation formula was: light transmittance T (%) = 10 -A , wherein: A is the measured UV-visible spectrophotometric value, and the results are shown in Figure 6 .

[0083] Figure 6 Figure is the UV transmittance diagram of the film, through Figure 6 it can be seen that the light transmittance of the film gradually decreases with the increase of the nanoparticles; in addition, in the films of CS\Gel-NPs-1.0, CS\Gel-NPs-1.5 and CS\Gel-NPs-2.0, the UV transmittance of the film is almost 0 in the range of 200-290 nm, which indicates that ZCDG NPs can greatly improve the light resistance of CS / Gel film. At the same time, the film has good visibility in the visible light range.

[0084] 5. Hemolytic performance test of the five composite packaging films prepared in Examples 2-5 and Comparative Example 1

[0085] Hemolytic performance test: Whole blood was obtained from healthy BALB / c mice using the eyeball blood collection method, collected in anticoagulant tubes, shaken evenly, and centrifuged at 3,000r for 15 minutes. The supernatant was carefully aspirated and discarded. Two times the amount of PBS was added, shaken again, and centrifuged at 3,000r for 15 minutes. The supernatant was discarded until the upper PBS layer was colorless. The supernatant was discarded and the lower blood cells were obtained. Composite films of different concentrations were dissolved in PBS. 1mL of film material solution, 1mL of ultrapure water (ddH20), and 1mL of PBS solution were taken and mixed with 20uL of red blood cell suspension. The samples were incubated at 37°C for 4 hours and centrifuged at 3,000r for 15 minutes. The samples were placed on the same horizontal line, and the hemolysis phenomenon was photographed with a mobile phone. The sample supernatant was aspirated with a pipette, and the absorbance of the sample at 542nm was measured using a microplate reader. The calculation formula is: Hemolysis rate (%) = (OD sample - OD PBS group) / (OD ddH20 group - OD PBS group × 100%.

[0086] Figure 7 is the blood compatibility diagram, through Figure 7 It can be seen that compared with the positive control ddH20 group, the hemolysis rates of the experimental groups such as CS\Gel and CS\Gel-NPs were lower than 5%, indicating that these materials have good blood compatibility and meet the requirements of biomaterials for hemolysis rate.

[0087] 6. Thermal stability test of the five composite packaging films prepared in Examples 2-5 and Comparative Example 1

[0088] Weigh approximately 0.007 g of each sample in an aluminum pan, weigh it, and seal it. An empty crucible under the same conditions was used as a reference. The thermal properties of the samples were studied on a DSCQ2000 (TA Instruments, USA). Thermal analysis was performed in the temperature range of 30-230°C with a heating rate of 10°C / min, a cooling rate of 20°C / min, a scanning speed of 10°C / min, and a nitrogen flow rate of 50 mL / min. The results are shown in Figure 2. Figure 8 .

[0089] Figure 8 It is a differential thermal scan diagram, through Figure 8 It can be seen that the addition of ZCDG nanoparticles increases the thermal stability of the original chitosan and gelatin composite film, giving it excellent thermal stability and meeting the temperature requirements of daily food packaging materials.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application 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 or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing a ZCDG nanoparticle-loaded chitosan and gelatin antibacterial and antioxidant composite packaging film, characterized in that: The following steps are involved: (1) Chitosan CS was weighed and dissolved in a mixed solution of acetic acid and deionized water, and then a plasticizer was added and stirred to obtain solution A; (2) Weigh gelatin Gel and dissolve it in deionized water, heat and stir to obtain solution B; (3) mixing solution A and solution B, heating and stirring to obtain solution C; (4) dissolving ZCDG nanoparticles in water to obtain solution D; (5) Solution D was added to solution C, and after ultrasonic stirring, the mixture was poured into a mold and dried to obtain a chitosan and gelatin antibacterial and antioxidant composite packaging film loaded with ZCDG nanoparticles.

2. The method for preparing the antibacterial and antioxidant composite packaging film of chitosan and gelatin loaded with ZCDG nanoparticles according to claim 1, characterized in that: The preparation of the ZCDG nanoparticles comprises the following steps: S1, dissolving curcumin Cur and zein Zein in an ethanol-water mixed solution, stirring to form a uniform mixed solution, adding the mixed solution dropwise into deionized water, and stirring to obtain a ZC NPs solution; S2, adding the dihydroquercetin DHQ solution dropwise to the ZC NPs solution and stirring to obtain a ZCD NPs solution; S3, dissolving gum arabic GA in deionized water and adjusting the pH to 5 to obtain a gum arabic GA solution, slowly adding the ZCDG NPs solution to the gum arabic GA solution and stirring to obtain a ZCDG NPs solution; S4. The ZCDG NPs solution was centrifuged and purified to remove uncoated components, and the supernatant was freeze-dried to obtain ZCDG nanoparticles.

3. The method for preparing the antibacterial and antioxidant composite packaging film of chitosan and gelatin loaded with ZCDG nanoparticles according to claim 2, characterized in that: In step S1, the volume ratio of ethanol to water in the ethanol-water mixed solution is 7:

3.

4. The method for preparing the antibacterial and antioxidant composite packaging film of chitosan and gelatin loaded with ZCDG nanoparticles according to claim 2, characterized in that: The mass ratio of curcumin Cur, zein Zein, dihydroquercetin DHQ and gum arabic GA is 0.05:0.5:0.01:0.

08.

5. The method for preparing the antibacterial and antioxidant composite packaging film of chitosan and gelatin loaded with ZCDG nanoparticles according to claim 1, characterized in that: The mass ratio of the chitosan CS to the gelatin Gel is 2:

3.

6. The method for preparing the antibacterial and antioxidant composite packaging film of chitosan and gelatin loaded with ZCDG nanoparticles according to claim 1, characterized in that: In step (1), the volume ratio of acetic acid to deionized water in the acetic acid-deionized water mixed solution is 1:

99.

7. The method for preparing the antibacterial and antioxidant composite packaging film of chitosan and gelatin loaded with ZCDG nanoparticles according to claim 1, characterized in that: In step (1), the plasticizer is glycerol, and the added amount of the glycerol is 30% of the mass of the chitosan.

8. The method for preparing the antibacterial and antioxidant composite packaging film of chitosan and gelatin loaded with ZCDG nanoparticles according to claim 1, characterized in that: In step (5), the stirring time is 1 hour, the ultrasonic time is 5 minutes; the drying temperature is 50° C., and the drying time is 12 hours.

9. A chitosan and gelatin antibacterial and antioxidant composite packaging film loaded with ZCDG nanoparticles, characterized in that: A chitosan and gelatin antibacterial and antioxidant composite packaging film loaded with ZCDG nanoparticles, prepared by the method according to any one of claims 1 to 8.

10. Use of the antibacterial and antioxidant composite packaging film of chitosan and gelatin loaded with ZCDG nanoparticles according to claim 9 in the field of food packaging materials and biomedicine.

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