A degradable photothermal antibacterial composite film based on MXene loaded epsilon-polylysine and preparation and application thereof

Abstract

The application discloses a kind of based on MXene load ε-polylysine degradable photothermal antibacterial composite film and its preparation and application.The MX@PL composite nanomaterial is prepared by the electrostatic self-assembly of the successfully etched MXene and ε-PL, then glycerol plasticizer-containing chitosan film liquid is added and stirred uniformly, and the degradable packaging film with photothermal antibacterial property is prepared by solvent casting method after ultrasonic degassing.Both the shortcomings of the cationic ε-PL being easily interacted with the anion components of food matrix to hinder the antibacterial activity and the two-dimensional nanoparticles with photothermal antibacterial property are obtained.

Description

Technical Field

[0001] This invention belongs to the field of antibacterial and biodegradable packaging film technology, specifically relating to a biodegradable photothermal antibacterial composite film based on MXene-loaded ε-polylysine and its preparation and application. Background Technology

[0002] Ensuring food safety for a growing global population is one of the most important challenges of the 21st century. In particular, foodborne pathogens not only cause a range of foodborne illnesses but also lead to food spoilage and decay. Food packaging protects food components from spoilage and prevents damage from the external environment. However, traditional petroleum-based packaging films lack biodegradability and antibacterial activity, hindering sustainable development and are gradually being replaced. Furthermore, the excessive or improper use of antimicrobial agents leads to bacterial resistance. While existing heat sterilization technologies can effectively prevent bacterial resistance, they are energy-intensive.

[0003] Chitosan has been a research hotspot in the food packaging film field due to its low cost, biodegradability, and unique film-forming properties. It exhibits excellent antibacterial properties after the addition of antibacterial agents. Cationic ε-polylysine (ε-PL) is a natural, food-grade antibacterial substance with characteristics such as edibility, biodegradability, heat resistance, and non-toxicity to humans. However, it readily interacts with the anionic components of the food matrix, leading to turbidity, precipitation, and hindering antibacterial activity. MXene Ti3C2, as an emerging two-dimensional nanomaterial, has been studied for its high aspect ratio, large specific surface area, and lack of drug resistance, and is used to load or immobilize antibacterial agents to improve antibacterial properties. Furthermore, MXene can convert light energy into heat energy under near-infrared light irradiation, making it an excellent photothermal agent. Photothermal antibacterial methods are not only energy-saving but also easily controlled by near-infrared light irradiation, thus overcoming the high energy consumption of existing thermal sterilization methods.

[0004] Chinese patent application 202111460539.1 discloses a "method for producing a biodegradable frozen food packaging film with photothermal antibacterial function." This method uses arabinoxylan extracted from wheat bran as the film substrate, and by adding plasticizers and antibacterial agents, a photothermal antibacterial biodegradable frozen food packaging film is prepared through casting, spraying with a photothermal agent, and hydrophobic modification. However, this film has drawbacks such as complex operation procedures and long processing times, and its photothermal antibacterial effect against Listeria monocytogenes in frozen foods is only investigated. Chinese patent application 202110482889.1 discloses a "pectin-based nano-melanin edible photothermal antibacterial film and its preparation method and application." This invention adds natural melanin nanoparticles to a pectin base liquid, and obtains a safe and edible photothermal antibacterial film through casting and drying. However, its drying time is long, the light power is high, and the sterilization time is long, and its sterilization effect is also only investigated against Listeria monocytogenes. Therefore, it is of great significance to develop a biodegradable photothermal antibacterial packaging film that is easy to operate, has low light power, and high sterilization efficiency. Summary of the Invention

[0005] To overcome the problems of complex and time-consuming preparation processes, high light power, limited sterilization types, and long sterilization times in existing photothermal nanocomposite film technologies, the primary objective of this invention is to provide a method for preparing a biodegradable photothermal antibacterial composite film based on MXene-loaded ε-polylysine (ε-PL). First, successfully etched MXene and ε-PL are electrostatically self-assembled to obtain MX@PL composite nanomaterials. Then, these nanomaterials are added to a chitosan (CS) film solution containing glycerol plasticizer and stirred until homogeneous. After ultrasonic degassing, a photothermal antibacterial and biodegradable packaging film (CMP film) is prepared by solvent casting.

[0006] Another object of the present invention is to provide a biodegradable photothermal antibacterial composite film based on MXene-loaded ε-polylysine prepared by the above preparation method.

[0007] Another object of the present invention is to provide the application of the above-mentioned MXene-loaded ε-polylysine biodegradable photothermal antibacterial composite film in food packaging.

[0008] The objective of this invention is achieved through the following technical solution:

[0009] A method for preparing a biodegradable photothermal antibacterial composite film based on MXene-loaded ε-polylysine includes the following steps:

[0010] (1) Mix MXene suspension and ε-polylysine (ε-PL) solution, stir for a period of time, collect by centrifugation, wash, and obtain MX@PL composite nanomaterials;

[0011] (2) Prepare a chitosan (CS) film solution containing plasticizer, mix the chitosan film solution and MX@PL composite nanomaterial evenly, degas, pour the film, and dry to obtain a composite film.

[0012] Preferably, in step (1), the mass ratio of MXene to ε-polylysine (ε-PL) is 1:(0-4), wherein the mass of ε-polylysine is not 0; more preferably, the mass ratio of MXene to ε-polylysine (ε-PL) is 1:4.

[0013] Preferably, the concentration of the MXene suspension in step (1) is 1 to 10 mg / mL; more preferably, it is 1 mg / mL.

[0014] Preferably, the concentration of the ε-polylysine (ε-PL) solution in step (1) is 0 to 4 mg / mL, wherein the concentration value is not 0; more preferably, it is 1 to 4 mg / mL.

[0015] Preferably, the solvent for both the MXene suspension and the ε-polylysine (ε-PL) solution in step (1) is water.

[0016] Preferably, the stirring time in step (1) is 1 to 5 hours; more preferably, it is 1 hour.

[0017] Preferably, the precipitate collected by centrifugation in step (1) is washed with water.

[0018] Preferably, in step (2), the mass ratio of plasticizer to chitosan is 0.2 to 0.6: 0.8 to 1; more preferably, it is 0.3: 1.

[0019] Preferably, in step (2), the plasticizer is glycerin.

[0020] Preferably, in the chitosan (CS) film solution containing plasticizer described in step (2), the concentration of chitosan is 10-20 mg / ml, more preferably 10 mg / ml; the solvent is an aqueous solution of acetic acid with a volume fraction of 1-3%, more preferably an aqueous solution of acetic acid with a volume fraction of 1%.

[0021] Preferably, the specific operation of preparing the chitosan (CS) film solution containing plasticizer in step (2) is as follows: add chitosan to an aqueous acetic acid solution, heat and stir to dissolve, then add plasticizer, mix evenly, and obtain the chitosan (CS) film solution containing plasticizer.

[0022] More preferably, the heating and stirring dissolution temperature is 40-60°C, and the time is 20-40 minutes.

[0023] Preferably, the MX@PL composite nanomaterial in step (2) accounts for 5-10% of the mass of chitosan; more preferably, it accounts for 5%.

[0024] Preferably, the degassing method in step (2) is ultrasonic degassing, and the ultrasonic time is 60 to 120 minutes.

[0025] Preferably, the drying time in step (2) is 40-60°C for 4-8 hours.

[0026] The above preparation method yields a biodegradable photothermal antibacterial composite film based on MXene-loaded ε-polylysine.

[0027] The above describes the application of an MXene-loaded ε-polylysine biodegradable photothermal antibacterial composite film in food packaging.

[0028] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0029] (1) In this invention, edible and heat-resistant cationic ε-PL and MXene two-dimensional nanomaterials with high specific surface area and negative charge are used to prepare MX@PL complex by efficient and green electrostatic adsorption self-assembly method. This not only solves the disadvantage that cationic ε-PL is easy to interact with the anionic components of food matrix and hinder antibacterial activity, but also obtains two-dimensional nanoparticles that can be photothermally antibacterial.

[0030] (2) The photothermal antibacterial and biodegradable CMP composite membrane obtained in this invention uses natural, inexpensive and biodegradable chitosan as the membrane substrate. By adding the prepared MX@PL composite, the membrane has good ultraviolet shielding performance and mechanical properties.

[0031] (3) The photothermal antibacterial and biodegradable CMP composite film obtained by the present invention has excellent oxygen barrier properties, which can effectively prevent food oxidation caused by the packaging environment.

[0032] (4) The CMP composite film prepared by this invention can withstand 808nm near-infrared laser light with a laser power density of 1.5W / cm². 2 After 3 minutes of irradiation, the membrane exhibits good bactericidal effects against common foodborne pathogens, with both Staphylococcus aureus and Escherichia coli showing photothermal antibacterial activity greater than 99%. Furthermore, the membrane demonstrates good photothermal stability and repeatability. Attached Figure Description

[0033] Figure 1 The loading rate of ε-PL in the MX@PL complex at different ε-PL to MXene mass ratios obtained in Example 1 is shown.

[0034] Figure 2 This is a schematic diagram illustrating the principle of the photothermal antibacterial biodegradable packaging film prepared based on MX@PL composite material obtained in Example 1.

[0035] Figure 3Transmittance diagrams of the CM film prepared for Comparative Example 2, the CS film prepared for Comparative Example 3, and the CMP-4 composite film prepared for Example 1.

[0036] Figure 4 Oxygen permeability diagrams of the CM membrane prepared for Comparative Example 2, the CS membrane prepared for Comparative Example 3, and the CMP-4 composite membrane prepared for Example 1.

[0037] Figure 5 Mechanical properties of the CM membrane prepared for Comparative Example 2, the CS membrane prepared for Comparative Example 3, and the CMP-4 composite membrane prepared for Example 1.

[0038] Figure 6 Photothermal stability curves of the CM film prepared for Comparative Example 2, the CS film prepared for Comparative Example 3, and the CMP-4 composite film prepared for Example 1;

[0039] Figure A shows the photothermal heating temperature change curves of the three films under 808nm laser irradiation. Figures B and C show the temperature changes of the CM film and CMP-4 film at 1.5W / cm², respectively. 2 Temperature change curves under photothermal cycling with 808nm laser irradiation, with 5 cycles.

[0040] Figure 7 The antibacterial effects of the CM membrane prepared for Comparative Example 2, the CS membrane prepared for Comparative Example 3, and the CMP-4 composite membrane prepared for Example 1 on Staphylococcus aureus and Escherichia coli are shown in the figure.

[0041] Figures A and C show the antibacterial effects of the membranes prepared in the comparative examples and the embodiment against Escherichia coli and Staphylococcus aureus, respectively. Figures B and D show the inhibition rates of the membranes prepared in the comparative examples and the embodiment against Escherichia coli and Staphylococcus aureus, respectively. Detailed Implementation

[0042] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the implementation of the present invention is not limited thereto.

[0043] Unless otherwise specified in the embodiments of this invention, the conditions shall be performed according to conventional conditions or conditions recommended by the manufacturer. All raw materials and reagents used, unless otherwise specified, are commercially available conventional products.

[0044] Preparation method of MXene powder: 1.0 g LiF was added to 20 mL HCl (9 mol / L) to obtain HF etching solution. After magnetic stirring until homogeneous, 1 g Ti3AlC2 powder was slowly added to the etching solution and stirred at 35℃ for 24 h. The resulting slurry was centrifuged at 3500 rpm for 5 min and the etching product was washed repeatedly with deionized water until a supernatant with pH = 6-7 was obtained. The precipitate was then collected, and an appropriate amount of deionized water was added for ultrasonic treatment for 1 h, followed by centrifugation at 3500 rpm for 1 h to obtain MXene Ti3C2Tx colloidal solution. Finally, the MXene colloidal solution was freeze-dried to obtain MXene powder.

[0045] Comparative Example 1: Preparation method of MX@PL complex

[0046] First, add 3 mg of MXene powder to 3 mL of deionized water and sonicate for 15 minutes using an ultrasonic cleaner to obtain a uniform and stable 1 mg / mL MXene suspension.

[0047] 2. According to the mass ratio of ε-PL:MXene of 0, 1, 2, 3, 4, 0, 3, 6, 9, 12 mg of ε-PL were dissolved in 3 mL of deionized water to form ε-PL solutions with concentrations of 0, 1, 2, 3, 4 mg / mL, respectively.

[0048] 3. Add ε-PL solutions with concentrations of 0, 1, 2, 3, and 4 mg / mL to the MXene solution from step 1, respectively. After stirring at room temperature for 1 hour, centrifuge the solution, collect the supernatant, and immediately determine the mass concentration of ε-PL in the supernatant using the methyl orange colorimetric method and calculate the loading rate. The precipitate collected by centrifugation is repeatedly washed with deionized water and then freeze-dried to obtain the MX@PL composite material.

[0049] Comparative Example 2: Preparation method of CM composite membrane

[0050] 1. Dissolve 0.12g CS in 12mL of 1% acetic acid aqueous solution and stir at 50℃ for 30min to obtain CS solution. Then add 0.036g glycerol as plasticizer and stir magnetically for 1h to obtain plasticized CS film solution.

[0051] 2. Add 6 mg of MXene powder to the CS membrane solution and mix well to obtain a membrane solution containing MXene nanomaterials, wherein the mass of MXene material is 5% relative to CS.

[0052] 3. Stir evenly and sonicate for 60 minutes to remove air bubbles from the membrane solution. Then slowly pour it into a 60 mm diameter culture dish and dry at 50 °C for 6 hours to obtain the CM composite membrane.

[0053] Example 1: Preparation method of CMP composite membrane

[0054] 1. Add 3 mg of MXene powder to 3 mL of deionized water and sonicate for 15 minutes to obtain a uniform and stable MXene suspension with a concentration of 1 mg / mL.

[0055] 2. According to the mass ratio of ε-PL:MXene of 1, 2, 3, 4, 3, 6, 9, 12 mg of ε-PL were dissolved in 3 mL of deionized water to form ε-PL solutions with concentrations of 1, 2, 3, 4 mg / mL, respectively.

[0056] 3. 3 mL of MXene suspension with a concentration of 1 mg / mL was mixed with 3 mL of ε-PL solutions with concentrations of 1, 2, 3, and 4 mg / mL, respectively, and stirred at room temperature for 1 h. The solutions were collected by centrifugation, the precipitates were washed with deionized water, and freeze-dried to obtain MX@PL-1, MX@PL-2, MX@PL-3, and MX@PL-4 composite nanomaterials, respectively.

[0057] 4. Dissolve 0.12g of CS in 12mL of 1% acetic acid aqueous solution, stir at 50℃ for 30min to obtain CS solution, then add 0.036g of glycerol as plasticizer, and stir magnetically for 1h to obtain plasticized CS film solution.

[0058] 5. Add 6 mg of MX@PL-1, MX@PL-2, MX@PL-3, and MX@PL-4 composite nanomaterials to the CS membrane solution, respectively, and mix evenly to obtain membrane solutions containing MX@PL-1, MX@PL-2, MX@PL-3, and MX@PL-4 nanomaterials, wherein the mass of MX@PL material is 5% relative to CS.

[0059] 6. Stir evenly and sonicate for 60 minutes to remove air bubbles from the membrane solution. Then slowly pour it into a 60 mm diameter culture dish and dry at 50 °C for 6 hours to obtain CMP-1, CMP-2, CMP-3 and CMP-4 composite membranes.

[0060] Comparative Example 3: Preparation method of CS membrane

[0061] 1. Dissolve 0.12g CS in 12mL of 1% acetic acid aqueous solution and stir at 50℃ for 30min to obtain CS solution. Then add 0.036g glycerol as plasticizer and stir magnetically for 1h to obtain plasticized CS film solution.

[0062] 2. Stir the CS membrane solution evenly and sonicate for 60 minutes to remove air bubbles. Then slowly pour it into a 60 mm diameter petri dish and dry it at 50 °C for 6 hours to obtain the CS membrane.

[0063] The antibacterial films prepared in the above embodiments and comparative examples were subjected to various tests and analyzed below:

[0064] (1) Comparison analysis of light transmittance

[0065] The CMP-4 film obtained in step six of Example 1 was cut into rectangular strips of 15mm × 40mm and placed on the sample holder of the UV spectrophotometer to measure the transmittance. (See attached image.) Figure 3 As shown:

[0066] from Figure 3 It can be seen that, compared with the CS film, the CMP-4 composite film shows varying degrees of decrease in transmittance in the near-ultraviolet region (200-400nm) and the visible light region (400-780nm), indicating that it has good ultraviolet shielding performance.

[0067] (2) Comparative analysis of oxygen permeability

[0068] The CMP-4 film obtained in step six of Example 1 was cut into circular films with a diameter of 80 mm. The gas permeability of the samples was measured using a gas permeability tester. See [link to relevant documentation]. Figure 4 As shown:

[0069] Figure 4 To assess the oxygen permeability of CS, CM, and CMP-4 films, from Figure 4 It can be seen that after the addition of MX@PL nanocomposite material, the CS membrane exhibits better compatibility with the CS membrane (2.87×10⁻⁶). -13 cm 3 ·cm / (cm 2 Compared to ·s·Pa), CM membrane (2.8×10 -14 cm 3 ·cm / (cm 2 ·s·Pa)) and CMP-4 membrane (2.64×10 -14 cm 3 ·cm / (cm 2 The oxygen permeability of ·s·Pa)) decreased significantly.

[0070] (3) Comparative analysis of mechanical properties

[0071] The CMP-4 film obtained in step six of Example 1 was cut into 10×90mm rectangular strips, and the tensile properties of the film were tested using an electronic universal testing machine. (See attached image.) Figure 5 As shown:

[0072] Figure 5 For the tensile strength and elongation at break of CS, CM and CMP-4 films, from Figure 5 It can be seen that the tensile strength of CMP-4 is increased to 18.76 MPa due to the introduction of MX@PL nanomaterials.

[0073] (4) Comparative analysis of photothermal stability

[0074] The CMP-4 film obtained in step six of Example 1 was cut into circular films with a diameter of 10 mm, and then subjected to an 808 nm near-infrared laser at a laser power density of 1.5 W / cm². 2 Irradiate the thin film sample for 3 minutes, then turn off the laser irradiator and allow it to cool naturally to room temperature before turning the laser back on. Repeat this process five times, recording the temperature change every 15 seconds.

[0075] Figure 6 The temperature variation curves of the CMP-4 thin film over five cycles; from Figure 6 It can be seen that during the five illumination cycles, the fluctuations in the maximum temperature of the CM film and the CMP-4 film were 1.59℃ (maximum temperatures of 74.08, 73.54, 74.6, 74.24 and 73.01) and 1.86℃ (maximum temperatures of 74.28, 73.72, 74.06, 72.42 and 74.24), respectively, with fluctuations not exceeding 2.6%.

[0076] (5) Comparative analysis of photothermal antibacterial properties

[0077] The plate count method was used to evaluate the performance of the CS membrane obtained in Comparative Example 3, the CM membrane obtained in Comparative Example 2, and the CMP-4 composite membrane obtained in Example 1 under 808 nm near-infrared laser light with a laser power density of 1.5 W / cm². 2 Antibacterial activity under irradiation. The prepared films were cut into 10mm diameter circular films and placed sequentially into 24-well plates. 1mL of *Escherichia coli* (ATCC 25922) or *Staphylococcus aureus* (ATCC 25923) suspension was added to the surface of each film. The films were treated with near-infrared laser (+NIR) or without near-infrared laser (-NIR) irradiation for 3 minutes each. All samples were then incubated at 37℃ for 4 hours. Subsequently, appropriately diluted bacterial solutions were plated onto LB agar plates and incubated at 37℃ for 12 hours. The inhibition rate was then calculated. (See attached table). Figure 7 As shown:

[0078] Figure 7 The image shows the antibacterial effect of the photothermal biodegradable antibacterial film prepared for the comparative examples and embodiments against Staphylococcus aureus and Escherichia coli.

[0079] from Figure 7It can be seen that, without 808nm near-infrared light irradiation, the antibacterial rates of CM membrane and CMP-4 membrane against Escherichia coli increased to 65.16% and 90.13%, respectively, compared to the CS membrane's inhibition rate (51.34%). After irradiation with 808nm infrared light, the antibacterial rate of CS membrane against E. coli did not change significantly, while the antibacterial rates of CM membrane and CMP-4 membrane significantly increased to 86.79% and 99.99%, respectively.

[0080] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a biodegradable photothermal antibacterial composite film based on MXene-loaded ε-polylysine, characterized in that, Includes the following steps: (1) Mix MXene suspension and ε-polylysine solution, stir for a period of time, collect by centrifugation, wash, and obtain MX@PL composite nanomaterials; (2) Prepare a chitosan film solution containing plasticizer, mix the chitosan film solution and MX@PL composite nanomaterial evenly, degas, pour the film, and dry to obtain a composite film; In step (1), the mass ratio of MXene to ε-polylysine is 1:(0-4), where the mass of ε-polylysine is not 0. In step (2), the MX@PL composite nanomaterial accounts for 5-10% of the mass of chitosan.

2. The method for preparing a biodegradable photothermal antibacterial composite film based on MXene-loaded ε-polylysine according to claim 1, characterized in that, In step (2), the mass ratio of plasticizer to chitosan is 0.2–0.6:0.8–1; The plasticizer is glycerin.

3. The method for preparing a biodegradable photothermal antibacterial composite film based on MXene-loaded ε-polylysine according to claim 1, characterized in that, The concentration of the MXene suspension in step (1) is 1–10 mg / mL; The concentration of the ε-polylysine solution in step (1) is 0 to 4 mg / mL, wherein the concentration value is not 0; The solvents for both the MXene suspension and the ε-polylysine solution in step (1) are water.

4. The method for preparing a biodegradable photothermal antibacterial composite film based on MXene-loaded ε-polylysine according to claim 1, characterized in that, In step (2), the concentration of chitosan in the plasticizer-containing chitosan film solution is 10-20 mg / ml; the solvent is an aqueous solution of acetic acid with a volume fraction of 1-3%.

5. The method for preparing a biodegradable photothermal antibacterial composite film based on MXene-loaded ε-polylysine according to claim 1, characterized in that, The stirring time in step (1) is 1 to 5 hours; The specific operation of preparing the chitosan film solution containing plasticizer in step (2) is as follows: add chitosan to an aqueous acetic acid solution, heat and stir to dissolve, then add plasticizer, mix evenly, and obtain the chitosan film solution containing plasticizer; The heating and stirring process is carried out at a temperature of 40–60°C for 20–40 minutes. The degassing method described in step (2) is ultrasonic degassing, and the ultrasonic time is 60-120 min; The drying time in step (2) is 40-60℃ for 4-8 hours.

6. The method for preparing a biodegradable photothermal antibacterial composite film based on MXene-loaded ε-polylysine according to claim 1, characterized in that, In step (1), the mass ratio of MXene to ε-polylysine is 1:4; In step (2), the mass ratio of plasticizer to chitosan is 0.3:1; In step (2), the MX@PL composite nanomaterial accounts for 5% of the mass of chitosan.

7. The method for preparing a biodegradable photothermal antibacterial composite film based on MXene-loaded ε-polylysine according to claim 1, characterized in that, The concentration of the MXene suspension in step (1) is 1 mg / mL; The concentration of the ε-polylysine solution in step (1) is 1–4 mg / mL; In step (2), the concentration of chitosan in the plasticizer-containing chitosan film solution is 10 mg / ml; the solvent is an aqueous solution of acetic acid with a volume fraction of 1%.

8. A biodegradable photothermal antibacterial composite film based on MXene-loaded ε-polylysine, prepared by the method according to any one of claims 1 to 7.

9. The application of the MXene-loaded ε-polylysine biodegradable photothermal antibacterial composite film according to claim 8 in food packaging.

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