Composite nanofiber membrane, preparation method thereof and low-temperature-resistant and multi-scene applicable wipe

Abstract

The application belongs to the field of nanofiber membranes, and relates to a composite nanofiber membrane, a preparation method thereof and a low-temperature-resistant and multi-scene applicable wipe. The composite nanofiber membrane is a blended polyvinyl alcohol-quaternized lignin nanofiber membrane and a polycaprolactone-quercetin nanofiber membrane. The composite nanofiber membrane contains an N-halamine precursor. The application develops a low-temperature-resistant composite nanofiber membrane to realize rapid inactivation of viruses, overcomes the problems that a disinfectant is not suitable for use in a low-temperature environment and is not suitable for household use, and solves the problem that a conventional antibacterial factor has a long action time.

Description

Technical Field

[0001] This invention belongs to the field of nanofiber membranes, specifically relating to a composite nanofiber membrane and its preparation method, a chlorinated composite nanofiber membrane and its preparation method, the application of nanofiber membranes, and a low-temperature resistant wipe suitable for multiple scenarios. Background Technology

[0002] The cold chain is a crucial method for the transportation, trading, and storage of fresh food, as low temperatures ensure food quality and freshness. Viruses and foodborne pathogens such as Escherichia coli and Staphylococcus aureus can adhere to food packaging and maintain high survival rates during storage and transportation. This means that low-temperature foods and their packaging can become carriers of viruses, leading to cross-contamination. Therefore, an effective method for virus elimination is needed to prevent the spread of virus particles through food packaging.

[0003] Common physical disinfection methods include autoclaving, ultraviolet sterilization, and ionizing radiation sterilization. These methods are commonly used in food production workshops and often require specialized machinery, making them unsuitable for home use. Common chemical disinfection methods utilize ozone, peroxides, and alcohol-based disinfectants. The effectiveness of traditional disinfectants is easily affected by various factors, such as concentration, cleaning methods, and environmental conditions. For example, frequent use of alcohol-based disinfectants has led to high alcohol tolerance in bacterial strains. Using traditional chemical disinfectants at low temperatures can cause freezing, affecting disinfectant concentration, prolonging contact time, and failing to effectively inactivate viruses. Quaternary ammonium compounds (QACs), as a novel type of disinfectant, possess low toxicity, good environmental stability, and low bacterial resistance, and have been used on many contact surfaces. Their mechanism of action involves positively charged quaternary ammonium groups attracting negatively charged bacteria, irreversibly disrupting the bacterial cell membrane through electrostatic and hydrophobic interactions, ultimately leading to bacterial death. Existing research indicates that quaternary ammonium groups can combine with natural polymers to enhance their antibacterial properties, such as chitosan and lignin. The introduction of quaternary ammonium groups can improve the hydrophilicity of compounds and enhance their antibacterial properties.

[0004] Chemical disinfection methods typically involve spraying, soaking, or wiping, but these are unsuitable for low-temperature stored foods. Furthermore, the overuse of disinfectants poses a serious challenge to ecosystems. Therefore, a new disinfection method is needed that is suitable for both low-temperature food disinfection and home use, while offering better safety. Bacteria and viruses easily adhere to surfaces such as food packaging, supermarket shopping cart handles, and door handles. Infected individuals leave their viruses or bacteria on these surfaces, leading to infection of subsequent contacts and causing cross-infection to some extent. To avoid infection, the simplest method is wiping disinfection. In dynamic wiping, shear and compressive forces are applied, which helps overcome the adhesion between bacteria and the surface, transferring bacteria from the object to the wiping cloth. Cellulose (including cotton and wood pulp), regenerated cellulose materials (such as viscose fiber), and synthetic polymers (such as polyester and polypropylene) are currently the most commonly used raw materials for the production of commercial wiping cloths. However, research shows that choosing unsuitable textile materials may bind to absorbed active ingredients, leading to reduced or complete inhibition of antibacterial efficacy. Therefore, selecting appropriate textile materials combined with antibacterial agents is crucial. Furthermore, conventional textile materials are non-biodegradable, so disinfectant wipes cannot be used in low-temperature environments, and their large-scale use also burdens the environment.

[0005] In summary, conventional disinfection methods are not suitable for low-temperature scenarios and home use. Bio-based disinfection products have a long action time, weak ability to kill viruses, and poor performance. There is an urgent need to develop a new type of product that can withstand low temperatures and be used in multiple scenarios to quickly kill bacteria and viruses. Summary of the Invention

[0006] To overcome the above shortcomings, this invention innovatively introduces haloamine precursors and PCL into the preparation of PQL-Cl / PQ composite nanofiber membranes. The aim is to improve the wipeable and rapid antibacterial properties of the nanofiber membranes. At the same time, the PQL-Cl / PQ composite nanofiber membranes are biodegradable, reducing the burden on the ecosystem.

[0007] To achieve the above objectives, the present invention provides a composite nanofiber membrane, wherein the composite nanofiber membrane is a blended polyvinyl alcohol-quaternized lignin nanofiber membrane and a polycaprolactone-quercetin nanofiber membrane; the composite nanofiber membrane contains an N-haloamine precursor.

[0008] A second aspect of the present invention provides a method for preparing the above-mentioned composite nanofiber membrane, comprising the following steps:

[0009] (1) Mix the aqueous solution of quaternized lignin with polyvinyl alcohol and polyethylene oxide, heat to dissolve completely, and obtain a stable polyvinyl alcohol-quaternized lignin electrospinning solution;

[0010] (2) Mix the polycaprolactone solution with quercetin evenly to obtain a stable polycaprolactone-quercetin electrospinning solution;

[0011] (3) The N-haloamine precursor is mixed evenly with polyvinyl alcohol-quaternized lignin electrospinning solution, and then electrospinned together with polycaprolactone-quercetin electrospinning solution to obtain the composite nanofiber membrane.

[0012] According to a preferred embodiment of the present invention, in step (1), the concentration of quaternized lignin in the polyvinyl alcohol-quaternized lignin electrospinning solution is 0.2~0.8wt%, and the concentration of polyvinyl alcohol is 6~10wt%.

[0013] The conditions for complete dissolution by heating include: first stirring continuously at 85~95℃ for 1~3 hours, and then stirring overnight at room temperature.

[0014] According to a preferred embodiment of the present invention, in step (1), the quaternized lignin is prepared by a method comprising the following steps:

[0015] Under alkaline conditions, a lignin sulfonate solution was mixed with a (3-chloro-2-hydroxypropyl)trimethylammonium chloride solution and heated to react. After the reaction was completed, the mixture was purified by dialysis to obtain the quaternized lignin.

[0016] Preferably, the alkaline condition is a pH of 11.5 to 12.5.

[0017] Preferably, the heating reaction conditions include: a temperature of 80~90℃ and a time of 3~6h.

[0018] Preferably, the dialysis purification is carried out using a dialysis bag with a molecular weight cutoff of 800-1200 kDa in a solution with a pH of 11.5-12.5.

[0019] According to a preferred embodiment of the present invention, in step (2), the solvent of the polycaprolactone solution is N,N-dimethylformamide and dichloromethane, with a volume ratio of 1:1~2;

[0020] The concentration of the polycaprolactone solution is 12-18 wt%, and the concentration of the quercetin is 2-8 wt%.

[0021] According to a preferred embodiment of the present invention, in step (3), the amount of the N-haloamine precursor added is 0.1~1wt% of the polyvinyl alcohol-quaternized lignin electrospinning solution, preferably 0.1~0.5wt%, more preferably 0.1~0.3wt%.

[0022] The N-haloamine precursor compound is one or more of 5,5-dimethylhydantoin, 2,2,6,6-tetramethylpiperidinol, and cyanuric acid.

[0023] The electrospinning parameters include: using an 18-gauge blunt needle, a distance of 15-17 cm between the needle and the roller collector, a roller rotation speed of 400-600 r / min, a 10 mL syringe with a flow rate of 0.6-1.0 mL / h, a high-voltage power supply set to 18-20 KV, and a temperature of 25°C. 2℃, relative humidity 50% 1%.

[0024] A third aspect of the present invention provides a chlorine-containing composite nanofiber membrane, wherein the chlorine-containing composite nanofiber membrane is obtained by chlorination treatment of the above-mentioned composite nanofiber membrane.

[0025] According to a preferred embodiment of the present invention, the chlorination treatment involves contacting the composite nanofiber membrane with chlorine gas.

[0026] Preferably, the chlorination treatment method includes: placing the composite nanofiber membrane near a sodium hypochlorite-hydrochloric acid mixed solution but not in direct contact with the mixed solution, while allowing the gas generated by the sodium hypochlorite-hydrochloric acid mixed solution to contact the composite nanofiber membrane and chlorinate it; more preferably, the pH of the sodium hypochlorite-hydrochloric acid mixed solution is 4.5~5.5.

[0027] According to a specific embodiment of the present invention, the chlorination treatment method includes: preparing a sodium hypochlorite-hydrochloric acid mixed solution with a pH of 4.5-5.5 to enable uniform gas generation; placing the composite nanofiber membrane in a beaker and separating it from the mixed solution using a polytetrafluoroethylene partition; and performing chlorination treatment under the condition that the sodium hypochlorite-hydrochloric acid mixed solution uniformly generates gas.

[0028] A fourth aspect of the present invention provides the application of the above-described composite nanofiber membrane or chlorine-containing composite nanofiber membrane in the preparation of disinfection products.

[0029] The fifth aspect of the present invention provides a low-temperature resistant wipeable cloth applicable to multiple scenarios, wherein the low-temperature resistant wipeable cloth is made from the above-mentioned composite nanofiber membrane or the above-mentioned chlorine-containing composite nanofiber membrane, and can be made using conventional wipeable cloth preparation processes in the art.

[0030] The various scenarios include: cardboard boxes (express delivery packaging, whole boxes of fresh food packaging, etc.), plastic packaging (ice cream packaging, meat product packaging, etc.), stainless steel equipment, etc.

[0031] This invention develops a low-temperature resistant composite nanofiber membrane to achieve rapid virus inactivation, which overcomes the problems that disinfectants are not suitable for low-temperature environments and for home use, and also solves the problem of long action time of conventional antibacterial agents.

[0032] The technical effects of this invention include:

[0033] (1) In this invention, quaternized lignin and PVA are selected to prepare an electrospinning solution, and quaternary ammonium groups are introduced into it to improve antibacterial properties; PCL and quercetin are selected to fully utilize the hydrophobic properties of PCL and the antibacterial properties of quercetin. The haloamine precursor DMH is introduced into the PVA-QL spinning solution, and a composite nanofiber membrane is prepared by blending. The composite nanofiber membrane is then chlorinated to achieve rapid killing of bacteria and viruses.

[0034] (2) This invention selects PVA and PCL to fully utilize the inherent degradation properties of these polymers, and the addition of PVA can improve the problem of slow degradation rate of PCL. The composite nanofiber membrane, as a wiping cloth, can effectively kill bacteria and viruses on the surface of food packaging stored at low temperatures. Compared with commercially available wipes, the nanofiber membrane is lighter, weighing only 0.5g, which reduces transportation costs in practical applications, and can be naturally degraded in soil, reducing the burden on the ecosystem.

[0035] (3) This invention improves the utilization of the high added value of lignin and provides a good prospect for the future development of biodegradable wipes.

[0036] (4) The composite nanofiber membrane of the present invention can rapidly inactivate bacteria within 2 minutes. It can be applied to cardboard boxes (express packaging, whole-box fresh food packaging, etc.), plastic packaging (ice cream packaging, meat product packaging, etc.), and stainless steel equipment (trays, dining tables, door handles, etc.), and has good versatility in multiple scenarios. It has been developed into a wipeable disinfection wipe product. The cost is comparable to that of commercially available disinfection wipes. In particular, the wipeable wipe of the present invention has good degradation properties, is green and environmentally friendly, and can be promoted for household use.

[0037] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0038] The above and other objects, features and advantages of the present invention will become more apparent from the more detailed description of exemplary embodiments of the invention in conjunction with the accompanying drawings.

[0039] Figure 1 The characterization results of quaternized lignin are shown: (a) Fourier transform infrared spectrum of quaternized lignin; (b) Zeta potential of quaternized lignin.

[0040] Figure 2 The performance evaluation results for polyvinyl alcohol-quaternized lignin nanofiber membranes are shown: (a) SEM image, (b) diameter distribution, (c) tensile strength, (d) elongation at break, and (e) water contact angle.

[0041] Figure 3 The performance evaluation results for PQL / PQ composite nanofiber membranes are shown: (a) SEM image, (b) tensile strength, (c) elongation at break, and (d) water contact angle.

[0042] Figure 4 The following are the performance evaluation results for the PQL-Cl / PQ composite nanofiber membrane: (a), (b) SEM images, (c) elemental mapping, (d) tensile strength, (e) elongation at break, (f) water contact angle, and (g) Cl. + Content, (h) in vitro cytotoxicity test, (i) biodegradation experiment.

[0043] Figure 5 The results of the antibacterial performance evaluation of the PQL-Cl / PQ composite nanofiber membrane are shown.

[0044] Figure 6 The effects of PQL-Cl / PQ composite nanofiber membranes on bacterial cell membrane damage are shown.

[0045] Figure 7 The practical antibacterial application of PQL-Cl / PQ composite nanofiber membranes is shown. Detailed Implementation

[0046] Preferred embodiments of the invention will now be described in more detail. While preferred embodiments of the invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0047] Unless otherwise specified in the examples, all procedures were performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0048] Materials and Methods

[0049] Sodium lignosulfonate (BR, 96%), starch indicator (1%), and polyethylene oxide were purchased from Shanghai Yuanye Biotechnology Co., Ltd. (China). Polycaprolactone (average Mn 80000), quercetin (97%), 5',5-dimethylhydantoin (98%), and sodium thiosulfate standard solution (0.1000 mol / L) were purchased from Shanghai Maclean Biochemical Technology Co., Ltd. (China). (3-chloro-2-hydroxypropyl)trimethylammonium chloride aqueous solution (65 wt%), iodine standard solution (0.05000 mol / L, 0.1 N), and polyvinyl alcohol were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. (China). Phosphate buffer solution (1×PBS) was purchased from Beijing Solarbio Technology Co., Ltd. (China). Sodium hypochlorite solution was purchased from Tianjin Fengchuan Chemical Reagent Technology Co., Ltd. Staphylococcus aureus (ATCC 6538) and Escherichia coli (ATCC 25922) were purchased from Beina Biotechnology (China). Tryptic Soy Agar and Tryptic Soy Broth were purchased from BD Bacto (USA). The Live & Dead Bacterial Staining Kit was purchased from Yisheng Biotechnology Co., Ltd. (Shanghai, China).

[0050] The electrospinning parameters used in the preparation of the thin film in this example are as follows: 18-gauge blunt needles were used for spinning; the distance between the spinning needle and the roller collector was 15-17 cm; the rotation speed of the roller was 500 r / min; a 10 mL syringe was used; the flow rate was 0.8 mL / h; the high-voltage power supply was set to 18-20 KV; and the temperature was 25°C. 2℃, relative humidity 50% 1%.

[0051] Example 1: Preparation of Quaternized Lignin

[0052] Lignosulfonate was weighed and prepared into a 20 wt% solution, and sodium hydroxide was added to adjust the pH to 12 to create an alkaline environment. The solution was heated in a water bath to 80°C, and a 65 wt% solution of (3-chloro-2-hydroxypropyl)trimethylammonium chloride (CHPTAC) was added. After 5 min, a 20 wt% sodium hydroxide solution was added to ensure the reaction proceeded under alkaline conditions. The reaction was carried out at 85°C for 4 h. After the reaction was complete, the solution was dialyzed using a dialysis bag with a molecular weight cutoff of 1000 kDa in a solution at pH 12 to remove unreacted CHPTAC and small molecule impurities. Dialysis was then performed in deionized water. The quaternized lignin was collected by freeze-drying after dialysis. Fourier transform infrared spectroscopy and Zeta potential were used to characterize the quaternized lignin.

[0053] Figure 1Figure (a) shows the FT-IR spectra of quaternized lignin (QL) and sodium lignin sulfonate (Li). At approximately 1467 cm⁻¹... -1 A new peak, a characteristic peak of the quaternary ammonium group, appeared at QL, indicating that the quaternary ammonium group was successfully grafted onto lignin. Figure 1 Figure (b) shows the Zeta potential diagrams of quaternized lignin and sodium lignin sulfonate. In a neutral deionized aqueous solution, the potential of QL is much higher than that of lignin without quaternary ammonium groups, indicating that the positively charged quaternary ammonium groups grafted onto the lignin surface neutralize some of the negative charge of sodium lignin sulfonate. These results demonstrate the grafting of positively charged quaternary ammonium groups onto lignin.

[0054] Example 2: Preparation of polyvinyl alcohol-quaternized lignin nanofiber membranes

[0055] Different proportions of quaternized lignin (0 wt%, 0.2 wt%, 0.4 wt%, 0.6 wt%) were dissolved in 10 mL of deionized water until fully dissolved. 8% polyvinyl alcohol and polyethylene oxide were then added, and the mixture was stirred continuously at 90°C for 2 hours to ensure complete and uniform dissolution. The mixture was then stirred overnight at room temperature to form a stable PVA-QL electrospinning solution.

[0056] Each PVA-QL electrospinning solution was electrospun to obtain polyvinyl alcohol-quaternized lignin nanofiber membranes, which were subsequently named PVA, PQL-2, PQL-4, and PQL-6.

[0057] Example 3: Preparation of polycaprolactone-quercetin nanofiber membranes

[0058] Polycaprolactone was weighed and dissolved in a solution of N,N-dimethylformamide and dichloromethane (N,N-dimethylformamide and dichloromethane volume ratio 2:3), and stirred for 4 hours to obtain a polycaprolactone solution with a final concentration of 15 wt%. Quercetin was added to the solution at a concentration of 4 wt%, and the solution was stirred overnight at room temperature to form a stable PCL-Que electrospinning solution.

[0059] Electrospinning was performed on each PCL-Que electrospinning solution to prepare polycaprolactone-quercetin nanofiber membranes, denoted as PQ nanofiber membranes.

[0060] Example 4: Preparation of blended polyvinyl alcohol-quaternized lignin / polycaprolactone-quercetin composite nanofiber membranes

[0061] (1) Composite nanofiber membrane PQL / PQ

[0062] Polyvinyl alcohol-quaternized lignin electrospinning solution (according to PQL-6 conditions) and polycaprolactone-quercetin electrospinning solution (according to PQ conditions) were prepared separately, stirred evenly at room temperature, and then electrospinned to obtain composite nanofiber membranes. After spinning, the composite nanofiber membranes were dried in a vacuum drying oven at 25°C, denoted as PQL / PQ.

[0063] (2) Composite nanofiber membrane PQL-DMH / PQ

[0064] Polyvinyl alcohol-quaternized lignin electrospinning solution (according to PQL-6 conditions) and polycaprolactone-quercetin electrospinning solution (according to PQ conditions) were prepared separately. 0.2 wt% of 5,5-dimethylhydantoin was added to the polyvinyl alcohol-quaternized lignin electrospinning solution. After stirring evenly at room temperature, electrospinning was performed to obtain a composite nanofiber membrane. After spinning, the composite nanofiber membrane was dried in a vacuum drying oven at 25℃, and designated as PQL-DMH / PQ nanofiber membrane.

[0065] Example 5 Chlorination of composite nanofiber membranes

[0066] A sodium hypochlorite-hydrochloric acid mixed solution with a pH of 5 was prepared to generate gas uniformly. The dried composite nanofiber membrane (PQL-DMH / PQ) prepared in Example 4 was placed in a beaker and separated from the solution by a polytetrafluoroethylene partition. Chlorination was carried out for 2 hours under the condition that the sodium hypochlorite-hydrochloric acid mixed solution generated gas uniformly, and the chlorinated composite nanofiber membrane was obtained, which was denoted as PQL-Cl / PQ.

[0067] Material property characterization

[0068] 1. Structural characterization

[0069] Field emission scanning electron microscopy (SEM) was used to test polyvinyl alcohol-quaternized lignin nanofiber membranes with different ratios and blended PQL / PQ, PQL-DMH / PQ, and PQL-Cl / PQ composite nanofiber membranes to examine the microstructure of the film surface.

[0070] 2. Mechanical property characterization

[0071] PQL nanofiber membranes with different contents and blended PQL / PQ, PQL-DMH / PQ, and PQL-Cl / PQ composite nanofiber membranes were all cut into 1×8 cm rectangles. The thickness of the nanofiber membranes was measured, and the tensile properties of the nanofiber membranes were determined using a tensile testing machine at a speed of 50 mm / min and an initial distance of 50 mm between the fixtures. Each group of samples was measured three times and the average value was taken.

[0072] 3. Characterization of water contact angle

[0073] Water contact angles of PQL nanofiber membranes with different contents and blended PQL / PQ, PQL-DMH / PQ, and PQL-Cl / PQ composite nanofiber membranes were determined by WCA analysis to evaluate the surface wettability of the materials.

[0074] 4. Determination of available chlorine content and stability of chlorine during storage.

[0075] The available chlorine content of the samples was determined using the iodometric method. The samples were weighed, chopped, and placed in a 0.001 N sodium thiosulfate solution, stirred for 20 min, and then 1 mL of starch indicator was added to simulate the dechlorination process of the composite nanofiber membrane. Titration was performed using a 0.001 N iodine standard solution, and the volume of iodine standard solution consumed was recorded. The available chlorine content was then calculated using the following formula:

[0076] Cl + (ppm) =

[0077] In the formula:

[0078] V0: The volume of iodine standard solution consumed without the addition of the composite nanofiber membrane, in mL.

[0079] V i : The volume of iodine standard solution consumed after adding the composite nanofiber membrane, in mL.

[0080] m: Mass of the added composite nanofiber membrane, in g.

[0081] The sample storage process was simulated by storing the sample in a sealed, dry, dark environment at room temperature and measuring its available chlorine content at different time points (1 w, 2 w, 3 w, 4 w).

[0082] 5. Antibacterial properties

[0083] (1) Determination of antibacterial rate by agar plate counting method

[0084] The antibacterial properties of the composite nanofiber membrane were evaluated using the agar plate count method. Gram-positive bacteria, represented by Staphylococcus aureus (ATCC 6538), and Gram-negative bacteria, represented by Escherichia coli (ATCC 25922), were selected to evaluate the antibacterial performance of the composite nanofiber membrane. Escherichia coli and Staphylococcus aureus were inoculated into 10 mL of liquid culture medium and cultured at 200 r / min and 37 ℃ until reaching 1×10⁻⁶. 8 After reaching CFU / mL, the bacterial culture was diluted to 1×10⁻⁶. 5Prepare CFU / mL for later use. Take 100 µL of bacterial suspension and drop it onto different types of membranes (2 cm × 3 cm). Incubate at 37 ℃ for 2 min, 5 min, 10 min, and 20 min. Then, add 900 µL of phosphate buffer, mix well, and take 100 µL of the bacterial suspension again. Inoculate the mixture onto solid agar plates, spread evenly, and incubate overnight in a constant temperature and humidity incubator. Evaluate the antibacterial performance of the material using the plate count method. The formula for calculating the antibacterial rate is as follows:

[0085] Antibacterial rate (%) = ×100

[0086] (2) Bacterial dead / live activity assay

[0087] 1×10 bacterial suspensions were used 8 CFU / mL of the bacterial suspension was incubated overnight at 37°C with the composite nanofiber membrane, using untreated bacteria as a control. After incubation, the suspension was centrifuged at 10,000 rpm for 1 min, the precipitate was collected, washed with physiological saline, and finally resuspended in 100 µL of physiological saline. The suspension was then stained for 15 min at room temperature using a live / dead bacteria staining kit. Two fluorescent dyes, DMAO and EthD-III, were used in a 1:2 ratio. 1 µL of the mixed dye was added to the bacterial suspension. After staining, 5 µL of the bacterial suspension was dropped onto a glass slide, and bacterial viability was observed under a confocal microscope at excitation / emission wavelengths of 496 / 528 nm (DMAO, green) and 532 / 625 nm (EthD-III, red).

[0088] (3) SEM characterization of bacterial morphology

[0089] 1×10⁻⁶ bacterial suspensions were cultured overnight. 9 CFU / mL. 1000 µL of *E. coli* and *Staphylococcus aureus* suspensions were incubated with a PQL-Cl / PQ composite nanofiber membrane at 37°C for 2 h. The control group was not included. The treated bacterial suspensions were centrifuged at 5000 rpm for 5 min and washed three times with 0.01 M PBS. 1 mL of 2.5% glutaraldehyde solution was added and the solution was fixed at 4°C for 4 h. The supernatant was discarded after centrifugation at 5000 rpm for 5 min, and the solution was washed three times with 0.01 M PBS. Dehydration was then performed by adding 1 mL of 30% ethanol, 50% ethanol, 70% ethanol, 90% ethanol, and 100% ethanol sequentially for 10 min each time. After dehydration, the solution was dropped onto a silicon wafer and dried overnight in a freeze dryer. The samples were then mounted on a scanning electron microscope plate and coated with a conductive layer for observation under a scanning electron microscope.

[0090] 6. Applications of composite nanofiber membranes

[0091] (1) Application of composite nanofiber membranes on the surface of cold chain food packaging

[0092] Gram-positive bacteria, represented by Staphylococcus aureus, and Gram-negative bacteria, represented by Escherichia coli, were selected to evaluate the application of composite nanofiber membranes on the surface of cold chain food packaging. Two different types of ice cream packaging (box packaging and bag packaging) were used to dilute the bacterial solution to 1×10⁻⁶. 4 CFU / mL was prepared for use. 200 µL of bacterial suspension was inoculated onto the packaging surface. After inoculation, the packaging was placed at different storage temperatures (4℃, -20℃, -80℃) to simulate the temperatures of cold chain food during transportation and storage. The next day, the packaging was removed and wiped with a composite nanofiber membrane. The control group was not wiped. A 1×1 cm cube was cut from the packaging surface and placed in 1 mL of liquid LB medium. The cube was incubated at 200 r / min and 37℃ for 2 h. 100 µL of bacterial suspension was then dropped onto a solid agar plate, spread evenly, and incubated overnight in a constant temperature and humidity incubator. The colony count on the agar plate was used to evaluate the wipeable bactericidal effect of the composite nanofiber membrane on cold chain food packaging.

[0093] (2) Application of composite nanofiber membranes on stainless steel surfaces

[0094] 100 µL of the above bacterial suspension was inoculated onto the surface of a stainless steel material. After inoculation, the surface of the stainless steel material was simulated by wiping. The control group was not wiped. Sterile cotton swabs were used to collect samples from the surface of the stainless steel material. After sampling, the samples were incubated in liquid culture medium for 2 hours and then spread onto agar plates. The colony count on the agar plates was used to evaluate the wipeable sterilization effect of the composite nanofiber membrane on cold chain food packaging.

[0095] 7. Safety evaluation of composite nanofiber membranes

[0096] The CCK-8 assay kit was used to evaluate the in vitro cytotoxicity of the composite nanofiber membrane. A 6 cm... 2 The composite nanofiber membrane was soaked in DMEM medium for 24 hours, and the sample extract was obtained by filtration. Mouse fibroblasts L929 were selected and cultured at 5 × 10⁻⁶ cells. 3 The sample was seeded at a concentration of [value missing] mL in 96-well plates. The cells were cultured at 37°C with 5% CO2 for 24 h. Then, 100 µL of sample extract was added to each well. After 24 h of incubation, 10 μL of CCK-8 solution was added to each well, and the plates were incubated at 37°C for 1 h. Commercially available polyethylene film (PE film) was used as a control group. OD values ​​were measured at 450 nm using a microplate reader.

[0097] Cell viability = (As - Ab) × 100 / (Ac - Ab)

[0098] As: Absorbance of experimental group (including cells, culture medium, CCK-8 solution and drug solution);

[0099] Ac: Absorbance of the negative control group (containing cells, culture medium, and CCK-8 solution, but excluding drugs);

[0100] Ab: Absorbance of blank group (including culture medium and CCK-8 solution, but excluding cells and drugs).

[0101] 8. Degradability of composite nanofiber membranes

[0102] The biodegradation experiment of the composite nanofiber membrane was carried out using the soil burial degradation method. Natural soil from an outdoor environment was selected. The composite nanofiber membrane with a size of 3 cm × 3 cm was placed in the same soil environment, and the degradation of the nanofiber membrane was observed and recorded by photography on the 1st, 3rd, 5th, 7th, 14th, and 28th days.

[0103] Performance evaluation and application of nanofiber membranes

[0104] 1. Performance evaluation of polyvinyl alcohol-quaternized lignin nanofiber membranes

[0105] like Figure 2 As shown in (a), the surface morphology and diameter distribution of PVA nanofiber membranes, PQL-2 nanofiber membranes, PQL-4 nanofiber membranes, and PQL-6 nanofiber membranes were observed using field emission scanning electron microscopy (SEM). With increasing amounts of quaternized lignin, their apparent morphology did not change significantly.

[0106] like Figure 2 As shown in (b), the fiber diameter of the nanofibers slightly increases with the increase of quaternized lignin addition. Specifically, the fiber diameter with 8% PVA solution is mainly distributed at around 205 nm. With the addition of quaternized lignin, the fiber diameter tends to increase (from around 205 nm to around 307 nm), which may be due to the hydrogen bonds formed between the hydroxyl groups of quaternized lignin and polyvinyl alcohol. Due to the interaction of hydrogen bonds, the viscosity of the spinning solution increases, resulting in a slight increase in diameter under the same voltage.

[0107] The tensile properties of nanofiber membranes are crucial for dynamic wiping. A tensile testing machine was used to evaluate the mechanical properties of the nanofiber membranes. Elongation at break is the ratio of the elongation at break to the original length. Tensile strength is the stress required to produce maximum uniform plastic deformation in a material. For example... Figure 2As shown in (c) and (d), the addition of quaternized lignin increased the tensile strength to twice that of the PVA nanofiber membrane, significantly optimizing its mechanical properties. However, the elongation at break gradually decreased. This is because the addition of quaternized lignin creates hydrogen bonds between the hydroxyl groups of the quaternized lignin and the hydroxyl groups of polyvinyl alcohol. The interaction between these hydrogen bonds increases the intermolecular bonding, leading to increased tensile strength and decreased elongation of the nanofibers.

[0108] Figure 2 Figure (e) shows the water contact angle of the quaternized lignin nanofiber membrane. It can be seen that after the addition of quaternized lignin, the water contact angle decreased from 48.57° to 34.21°, and the water contact angle gradually decreased with the addition of quaternized lignin. This is because quaternized lignin is a water-soluble substance, and its addition leads to better solubility of the nanofiber membrane in water. Considering that increasing the amount of quaternized lignin did not significantly affect the mechanical properties, appearance, or water contact angle of the PVA-QL nanofiber membrane, PQL-6 (denoted as PQL) was selected for further research in this invention.

[0109] 2. Performance evaluation of PQL / PQ composite nanofiber membranes

[0110] The surface morphology of polycaprolactone-quercetin (PQ) nanofiber membranes, PQL nanofiber membranes, and PQL / PQ composite nanofiber membranes was observed using field emission scanning electron microscopy (SEM). Figure 3 As shown in (a), the PQ nanofiber membrane exhibits fiber adhesion, possibly due to excessively high solution concentration and incomplete evaporation of the organic reagent. However, the scanning electron microscope image of the PQL / PQ composite nanofiber membrane shows both distinct individual fibers and adhered fibers, indicating that the composite nanofiber membrane obtained through blending possesses both PQL and PQ nanofiber membrane morphologies, signifying the successful synthesis of the composite nanofiber membrane.

[0111] The mechanical properties of nanofiber membranes were evaluated using a tensile testing machine. For example... Figure 3 As shown in (b) and (c), the tensile strength of the PQL / PQ composite nanofiber membrane is 8.73 MPa, which is much higher than that of the single nanofiber membrane; the elongation at break of the PQL / PQ composite nanofiber membrane is slightly lower than that of the single nanofiber membrane.

[0112] The surface wettability of composite nanofiber membranes and single nanofiber membranes was evaluated using a WCA analyzer. Figure 3As shown in (d), the PQL nanofiber membrane exhibits good water solubility, thus making it unsuitable for wiping disinfection and sterilization. In contrast, the PQ nanofiber membrane possesses superior hydrophobic properties, with a water contact angle as high as 102°. The PQL / PQ composite nanofiber membrane has a water contact angle of 75.09°, significantly higher than that of the single PQL nanofiber membrane. This demonstrates that the PQ nanofiber membrane increases the water contact angle of the composite nanofiber membrane, providing a hydrophobic substrate for its subsequent applications.

[0113] 3. Performance evaluation of PQL-Cl / PQ composite nanofiber membranes

[0114] The surface morphology of the nanofiber membranes before and after chlorination was observed using field emission scanning electron microscopy. Figure 4 (a) is the composite nanofiber membrane PQL-DMH / PQ obtained by adding the haloamine precursor 5',5-dimethylhydantoin (DMH) during the blending process. The morphology of the original PQL / PQ composite nanofiber membrane is not significantly different. Figure 4 (b) is the PQL-DMH / PQ composite nanofiber membrane obtained by chlorination. It is obvious that the morphology of the PQL-DMH / PQ composite nanofiber membrane has changed. The fibers have changed from the original circular cross-section to a flat ellipse or ribbon shape, which may be due to the pressure applied to the nanofibers during the operation.

[0115] Figure 4 The elemental mapping diagram (c) reflects that N and Cl elements are evenly distributed in the PQL-Cl / PQ composite nanofiber membrane, and the large presence of Cl element indicates that the chlorination reaction proceeds smoothly.

[0116] The mechanical properties of PQL-Cl / PQ composite nanofiber membranes are reduced, such as... Figure 4 As shown in (d) and (e).

[0117] The surface wettability of the nanofiber membrane after DMH introduction and chlorination reaction was evaluated using a water contact angle meter. Figure 4 As shown in (f), the water contact angle of the PQL-DMH / PQ composite nanofiber membrane with the addition of the haloamine precursor decreased from 75.09° to 62.44°. This may be because DMH contains NH bonds, which can form hydrogen bonds with the hydroxyl groups of water molecules, increasing hydrophilicity and thus decreasing the water contact angle. After the chlorination reaction, the NH bonds are converted into N-Cl bonds, the hydrogen bonds disappear, and the water contact angle of the PQL-Cl / PQ composite nanofiber membrane recovers.

[0118] Considering that the wipes are not immediately used after preparation, this invention simulates the storage process of the wipes by placing them in a sealed environment at room temperature to test the Cl content of PQL-Cl / PQ composite nanofiber membranes at different storage times.+ The available chlorine content was assessed to evaluate the storage stability of the PQL-Cl / PQ composite nanofiber membrane. Iodometric analysis was used to evaluate the available chlorine content of the chlorinated composite nanofiber membrane. Figure 4 As shown in (g), with increasing storage time, from 1 day to 7 days, Cl + The content decreased rapidly, but stabilized after 7 days. + The concentration remained between 200 ppm and 300 ppm, indicating that the PQL-Cl / PQ composite nanofiber membrane exhibits good storage stability.

[0119] This invention employs the CCK-8 assay to evaluate the in vitro cytotoxicity of nanofiber membranes. The in vitro cytotoxicity of PQL nanofiber membranes, PQ nanofiber membranes, PQL / PQ composite nanofiber membranes, PQL-DMH / PQ composite nanofiber membranes, and PQL-Cl / PQ composite nanofiber membranes was studied using mouse fibroblast L929 cells. The results of cell viability analysis using the CCK-8 assay are as follows: Figure 4 As shown in (h), both single and composite nanofiber membranes exhibited cell viability exceeding 70%, showing no significant difference from the negative control PE membrane. This demonstrates that the PQL-Cl / PQ composite nanofiber membrane possesses excellent cell biocompatibility and is non-cytotoxic. Therefore, it can be applied to the surfaces of low-temperature food packaging and processing / transportation equipment.

[0120] To assess the burden of nanofiber membranes on ecosystems, this invention simulates the biodegradation process of nanofiber membranes, such as... Figure 4 As shown in (i), using PE membrane as the control group, it can be seen that, except for PE membrane, the other nanofiber membranes showed obvious shape changes after 14 days. The PQL-DMH / PQ and PQL-Cl / PQ composite nanofiber membranes showed surface wrinkling. The PQL nanofiber membrane had already completed degradation by day 3, possibly because PVA is water-soluble, and the nanofiber membrane absorbed moisture from the soil to complete the degradation. Due to the presence of PQL nanofiber membranes, both the PQL-DMH / PQ and PQL-Cl / PQ composite nanofiber membranes showed surface wrinkling and reduced area on day 3. All membranes showed significant biodegradation after 2 weeks, with the PQL-DMH / PQ and PQL-Cl / PQ composite nanofiber membranes showing more pronounced degradation characteristics. This indicates that the blended composite nanofiber membrane optimized the slow degradation rate of the single PQ nanofiber membrane, demonstrating that both single and composite nanofiber membranes have good biodegradability under natural soil conditions.

[0121] 4. Evaluation of the antibacterial performance of composite nanofiber membranes

[0122] Based on the novel coronavirus's resistance to disinfectants, Staphylococcus aureus (Staphylococcus aureus) is a selectable indicator microorganism. S. aureus ATCC 6538) and Escherichia coli ( E. coli ATCC25922) is used as an indicator microorganism during chemical disinfection. Therefore, this invention selects... S. aureus ATCC 6538 and E. coli ATCC25922 was used as a model bacterium to evaluate the antibacterial activity of PQL-Cl / PQ composite nanofiber membranes. Antibacterial experiments were conducted using PQL-DMH / PQ composite nanofiber membranes, commercially available antibacterial wipes, and PQL-Cl / PQ composite nanofiber membranes. Figure 5 As shown in (a) and (c), after 2 minutes of contact between Staphylococcus aureus and Escherichia coli and different membranes, the colony-forming units (CFU) on the surface of commercially available antibacterial wipes and PQL-Cl / PQ composite nanofiber membranes were significantly lower than those on the PQL-DMH / PQ composite nanofiber membrane. According to the agar plate counting method, the contact kill and antibacterial rate of PQL-Cl / PQ composite nanofiber membrane against Escherichia coli and Staphylococcus aureus within 2 minutes was 99.9%. Figure 5 (b) and (d)).

[0123] This invention investigated the effect of PQL-Cl / PQ composite nanofiber membranes on bacterial cell membrane damage, using DMAO and EthD-III dyes. DMAO is a green nucleic acid fluorescent dye that can stain both live and dead bacteria. EthD-III is a red nucleic acid fluorescent dye that only stains dead bacteria with damaged cell membranes. When DMAO and EthD-III were mixed for staining, bacteria with intact cell membranes appeared green, while bacteria with damaged cell membranes appeared both green and red. The PQL-Cl / PQ composite nanofiber membranes were incubated with bacteria overnight at 37°C, and the bacterial viability could be visually assessed using the red and green staining. Figure 6 As shown in (a) and (b), under a laser confocal microscope, Escherichia coli and Staphylococcus aureus treated with PQL-Cl / PQ composite nanofiber membranes appear red, indicating that the PQL-Cl / PQ composite nanofiber membranes cause irreversible damage to the bacterial cell membranes.

[0124] 5. Practical applications of composite nanofiber membranes

[0125] This invention simulates the home use scenario of PQL-Cl / PQ composite nanofiber membranes, selecting common packaging for low-temperature food storage, such as bag packaging and cardboard box packaging, and using 4℃, -20℃, and -80℃ to simulate the storage temperature conditions for low-temperature food storage. Figure 7 (a) and (b) show that pathogenic bacteria were inoculated onto the outer surface of food packaging at a rate of 2 × 10⁻⁶. 4CFU (Chemical Fumes) were stored overnight at different temperature conditions to simulate a real-world scenario of bacterial contamination of food packaging. The experimental group was treated by wiping with a 6×6 cm PQL-Cl / PQ composite nanofiber membrane for 2 minutes, while the control group received no treatment. Samples were collected and cultured from the packaging surface using sterile cotton swabs. Figure 7 As shown in (e) and (f), after wiping the two types of packaging with the PQL-Cl / PQ composite nanofiber membrane for 2 minutes at different ambient temperatures, the colony-forming units on the agar plates were significantly smaller than those of the unwiped control group. The kill rate of Staphylococcus aureus and Escherichia coli on the food packaging surface after wiping was as high as 99.9%. This indicates that the PQL-Cl / PQ composite nanofiber membrane can eliminate pathogenic bacteria on the surface of food packaging.

[0126] Stainless steel is commonly used in the storage and transportation of low-temperature foods. Examples include stainless steel plates and drawers used in cold storage construction; and it is also frequently used in everyday catering preparation areas and food factory production lines, such as stainless steel tabletops and the stainless steel casings of operating equipment. This invention uses stainless steel trays to replace stainless steel materials (…). Figure 7 (c)). Inoculate 2×10 on the tray surface. 4 CFU bacteria were used in an experimental group where stainless steel trays were wiped with a 6×6cm PQL-Cl / PQ composite nanofiber membrane for 2 minutes, while the control group received no treatment. Samples were collected from the treated trays using sterile cotton swabs and incubated with liquid culture medium at 37℃ for 2 hours. The bacterial suspension was then spread onto agar plates. After wiping with the PQL-Cl / PQ composite nanofiber membrane for 2 minutes, the colony-forming units on the agar plates were significantly smaller than those in the untreated control group, resulting in an antibacterial rate as high as 99.9%. Figure 7 (d) The above experiments demonstrate that PQL-Cl / PQ composite nanofiber membranes can be used to wipe stainless steel equipment, desktops, etc., to prevent bacteria from being located on the surface of stainless steel, thereby affecting the quality of food during food processing.

[0127] This invention presents a low-temperature resistant wipe suitable for various scenarios, enabling rapid inactivation of novel viruses. It exhibits low-temperature adaptability and rapid killing of bacteria and viruses. The invention utilizes a blend of PVA-QL and PCL-Que spinning solutions to prepare the nanofiber membrane. The addition of quaternary ammonium groups attracts negatively charged bacterial and viral particles, allowing the PQL-Cl / PQ composite nanofiber membrane to rapidly exert its effects upon contact with these particles. The introduction of PVA optimizes the slow degradation rate of PCL-based composite nanofiber membranes. The addition of PCL and quercetin imparts hydrophobic properties to the composite nanofiber membrane, giving it wipeable properties. The PQL-Cl / PQ composite nanofiber membrane can rapidly kill Escherichia coli and Staphylococcus aureus within 2 minutes. It demonstrates good versatility for cardboard boxes, plastic packaging, and stainless steel equipment, and has been developed as a disinfectant wipe product for coronaviruses and foodborne pathogens. In particular, the PQL-Cl / PQ composite nanofiber membrane is extremely lightweight, significantly reducing transportation costs. More importantly, this wiping cloth exhibits excellent biodegradability, making it environmentally friendly. In conclusion, the PQL-Cl / PQ composite nanofiber membrane can be used for wiping, disinfecting, and antibacterial purposes on low-temperature food packaging, playing a crucial role in effectively blocking the spread of viruses through cold chain logistics, and is suitable for home use.

[0128] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A method for preparing a composite nanofiber membrane, characterized in that, The composite nanofiber membrane is a blend of polyvinyl alcohol-quaternized lignin nanofiber membrane and polycaprolactone-quercetin nanofiber membrane; the composite nanofiber membrane contains N-haloamine precursor; The preparation method includes the following steps: (1) Mix the aqueous solution of quaternized lignin with polyvinyl alcohol and polyethylene oxide, heat to dissolve completely, and obtain a stable polyvinyl alcohol-quaternized lignin electrospinning solution; (2) Mix the polycaprolactone solution with quercetin evenly to obtain a stable polycaprolactone-quercetin electrospinning solution; (3) The N-haloamine precursor is mixed evenly with polyvinyl alcohol-quaternized lignin electrospinning solution, and then electrospinned together with polycaprolactone-quercetin electrospinning solution to obtain the composite nanofiber membrane.

2. The method for preparing the composite nanofiber membrane according to claim 1, characterized in that, In step (1), the concentration of quaternized lignin in the polyvinyl alcohol-quaternized lignin electrospinning solution is 0.2~0.8wt%, and the concentration of polyvinyl alcohol is 6~10wt%. The conditions for complete dissolution by heating include: first stirring continuously at 85~95℃ for 1~3 hours, and then stirring overnight at room temperature.

3. The method for preparing the composite nanofiber membrane according to claim 1, characterized in that, In step (1), the quaternized lignin is prepared by a method comprising the following steps: Under alkaline conditions, a lignin sulfonate solution was mixed with a (3-chloro-2-hydroxypropyl)trimethylammonium chloride solution and heated to react. After the reaction was completed, the mixture was purified by dialysis to obtain the quaternized lignin.

4. The method for preparing the composite nanofiber membrane according to claim 3, characterized in that, The alkaline conditions are a pH of 11.5 to 12.5; The heating reaction conditions include: a temperature of 80~90℃ and a time of 3~6h; The dialysis purification was carried out using a dialysis bag with a molecular weight cutoff of 800-1200 kDa in a solution with a pH of 11.5-12.

5.

5. The method for preparing the composite nanofiber membrane according to claim 1, characterized in that, In step (2), the solvent of the polycaprolactone solution is N,N-dimethylformamide and dichloromethane, with a volume ratio of 1:1~2. The concentration of the polycaprolactone solution is 12-18 wt%, and the concentration of the quercetin is 2-8 wt%.

6. The method for preparing the composite nanofiber membrane according to claim 1, characterized in that, In step (3), the amount of the N-haloamine precursor added is 0.1~1wt% of the polyvinyl alcohol-quaternized lignin electrospinning solution; The N-haloamine precursor compound is one or more of 5,5-dimethylhydantoin, 2,2,6,6-tetramethylpiperidinol, and cyanuric acid; The electrospinning parameters include: using an 18-gauge blunt needle, a distance of 15-17 cm between the needle and the roller collector, a roller rotation speed of 400-600 r / min, a 10 mL syringe with a flow rate of 0.6-1.0 mL / h, a high-voltage power supply set to 18-20 KV, and a temperature of 25°C. 2℃, relative humidity 50% 1%.

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