CN114182435B

CN114182435B - Polylactic acid antibacterial composite fiber membrane and preparation method and application thereof

Info

Publication number: CN114182435B
Application number: CN202111503238.2A
Authority: CN
Inventors: 刘淑强; 吴改红; 武捷; 申佳鹤; 李静静; 张曼; 李甫; 贾潞; 张钰晶; 张爱琴
Original assignee: Taiyuan University of Technology
Current assignee: Taiyuan University of Technology
Priority date: 2021-12-10
Filing date: 2021-12-10
Publication date: 2023-03-17
Anticipated expiration: 2041-12-10
Also published as: CN114182435A

Abstract

The invention provides a polylactic acid antibacterial composite fiber membrane and a preparation method and application thereof, belonging to the technical field of antibacterial materials and comprising the following steps: mixing the silver source with tea polyphenol and water, and carrying out reduction reaction to obtain a composite antibacterial agent; mixing the composite antibacterial agent with polylactic acid, a solvent and a coupling agent to obtain a skin layer spinning solution; mixing polylactic acid and a solvent to obtain a core layer spinning solution; and (3) carrying out coaxial electrostatic spinning on the skin layer spinning solution and the core layer spinning solution to obtain the polylactic acid antibacterial composite fiber membrane. The invention firstly adopts a tea polyphenol biological reduction method to prepare the composite antibacterial agent, improves the antibacterial performance of the composite fiber membrane, adopts coaxial electrostatic spinning to prepare the skin-core composite fiber membrane and improves the mechanical performance of the composite fiber membrane. The results of the examples show that the antibacterial rate of the polylactic acid antibacterial composite fiber membrane prepared by the invention on escherichia coli reaches 99.32%, and the breaking strength reaches 53cN.

Description

Polylactic acid antibacterial composite fiber membrane and preparation method and application thereof

Technical Field

The invention relates to the technical field of antibacterial materials, in particular to a polylactic acid antibacterial composite fiber membrane and a preparation method and application thereof.

Background

With the development of social industry, impurities and bacteria contained in the air are increased, and harm is caused to human health. The polylactic acid has good biocompatibility, mechanical property and biodegradability, and is an environment-friendly sustainable development material. However, the polylactic acid material does not have antibacterial performance, and an antibacterial agent is generally required to be added in order to improve the antibacterial performance of the polylactic acid material and reduce the harm of bacteria to human bodies.

At present, the commonly used antibacterial agent is nano silver particles, but the improvement of the antibacterial performance of polylactic acid by adding nano silver is limited, the nano silver is added into the polylactic acid in the prior art such as the invention patent with the publication number of CN108914375A, and the highest antibacterial rate of the composite material to escherichia coli is only 95%.

Therefore, how to further improve the antibacterial performance of polylactic acid becomes a problem in the prior art.

Disclosure of Invention

In view of the above, the present invention aims to provide a polylactic acid antibacterial composite fiber membrane, and a preparation method and an application thereof. The polylactic acid antibacterial composite fiber membrane prepared by the invention has excellent antibacterial performance.

In order to achieve the above object, the present invention provides the following technical solutions:

the invention provides a preparation method of a polylactic acid antibacterial composite fiber membrane, which comprises the following steps:

(1) Mixing a silver source with tea polyphenol and water, and carrying out reduction reaction to obtain a composite antibacterial agent;

(2) Mixing the composite antibacterial agent obtained in the step (1) with polylactic acid, a solvent and a coupling agent to obtain a skin layer spinning solution;

(3) Mixing polylactic acid and a solvent to obtain a core layer spinning solution;

(4) Carrying out coaxial electrostatic spinning on the skin layer spinning solution obtained in the step (2) and the core layer spinning solution obtained in the step (3) to obtain a polylactic acid antibacterial composite fiber membrane;

the steps (1) and (3) are not in sequence.

Preferably, the ratio of the amount of the tea polyphenol to the silver source substance in the step (1) is (1-1.5): 1.

preferably, the solvent in step (2) and step (3) comprises N, N-dimethylformamide and dichloromethane.

Preferably, the mass ratio of the dichloromethane to the N, N-dimethylformamide is (2-3): 1.

preferably, the mass concentration of the polylactic acid in the skin layer spinning solution in the step (2) is 4-6%.

Preferably, the mass ratio of the composite antibacterial agent to the polylactic acid in the step (2) is (0.5-3): 5.

preferably, the coupling agent in the step (2) comprises a silane coupling agent; the mass ratio of the coupling agent to the composite antibacterial agent is (0.05-0.2): 1.

preferably, the spinning voltage of the coaxial electrostatic spinning in the step (4) is 14-16 kV; the spinning distance of the coaxial electrostatic spinning is 8-14 cm; the propelling speeds of the skin layer spinning solution and the core layer spinning solution are independent and are 1-2 mL/h in coaxial electrostatic spinning.

The invention provides the polylactic acid antibacterial composite fiber membrane prepared by the preparation method of the technical scheme.

The invention also provides the application of the polylactic acid antibacterial composite fiber membrane in the antibacterial field.

The invention provides a preparation method of a polylactic acid antibacterial composite fiber membrane, which comprises the following steps: mixing the silver source with tea polyphenol and water, and carrying out reduction reaction to obtain a composite antibacterial agent; mixing the obtained composite antibacterial agent with polylactic acid, a solvent and a coupling agent to obtain a skin layer spinning solution; mixing polylactic acid and a solvent to obtain a core layer spinning solution; and carrying out coaxial electrostatic spinning on the obtained skin layer spinning solution and the obtained core layer spinning solution to obtain the polylactic acid antibacterial composite fiber membrane. According to the invention, the nano-silver composite antibacterial agent is prepared by adopting the tea polyphenol biological reduction silver source, so that the nano-silver composite antibacterial agent has excellent antibacterial performance and can improve the antibacterial property of the fiber membrane; meanwhile, the skin-core composite fiber membrane is prepared by adopting coaxial electrostatic spinning, so that the mechanical property of the composite fiber membrane is improved. The results of the examples show that the antibacterial rate of the polylactic acid antibacterial composite fiber membrane prepared by the invention on escherichia coli reaches 99.32%, and the breaking strength reaches 53cN.

Drawings

FIG. 1 is a scanning electron microscope image of a fiber film prepared in example 1 of the present invention at a magnification of 3000;

FIG. 2 is a scanning electron microscope image of a fiber film prepared in example 1 of the present invention at 5000 magnification;

FIG. 3 is a scanning electron micrograph of a fibrous membrane prepared according to comparative example 2 of the present invention;

FIG. 4 is a scanning electron micrograph of a fibrous membrane prepared according to comparative example 3 of the present invention;

FIG. 5 is a scanning electron microscope image of a fiber film prepared in comparative example 1 of the present invention at a magnification of 3000;

FIG. 6 is a scanning electron microscope image of a fiber film prepared in comparative example 1 of the present invention at 5000 magnification;

FIG. 7 is a scanning electron micrograph of a fibrous membrane prepared in example 2 of the present invention;

FIG. 8 is a scanning electron micrograph of a fibrous membrane prepared according to example 3 of the present invention;

FIG. 9 is a scanning electron micrograph of a fibrous membrane prepared in example 4 of the present invention;

FIG. 10 is a scanning electron micrograph of a fibrous film prepared according to example 5 of the present invention;

FIG. 11 is an infrared spectrum of a fiber film prepared in examples 2 to 5 of the present invention and comparative example 1;

FIG. 12 is an XRD pattern of the fiber membranes prepared in examples 2 to 5 of the present invention and comparative example 1;

FIG. 13 is a colony count chart of the fiber membranes prepared in examples 2 to 5 of the present invention and comparative example 1;

FIG. 14 is a graph showing mechanical properties of fiber membranes prepared in examples 1 to 4 of the present invention and comparative example 1;

FIG. 15 is a contact angle of the fiber membrane prepared in example 3 of the present invention and comparative example 1;

fig. 16 is an XRD pattern of the composite antibacterial agent prepared in example 1 of the present invention;

FIG. 17 is a chart showing an ultraviolet-visible absorption spectrum of a composite antibacterial agent prepared in example 1 of the present invention;

FIG. 18 is a colony count chart of the composite antibacterial agent prepared in example 1 of the present invention.

Detailed Description

(1) Mixing the silver source with tea polyphenol and water, and carrying out reduction reaction to obtain a composite antibacterial agent;

(3) Mixing polylactic acid with a solvent to obtain a core layer spinning solution;

the steps (1) and (3) are not in sequence.

In the present invention, the sources of the components are not particularly limited, unless otherwise specified, and commercially available products known to those skilled in the art may be used.

The invention mixes the silver source with the tea polyphenol and water to carry out reduction reaction, thus obtaining the composite antibacterial agent.

In the present invention, the silver source preferably comprises silver nitrate or a silver ammonia solution, more preferably silver nitrate.

In the present invention, the ratio of the amount of the tea polyphenol to the silver-derived substance is preferably (1 to 1.5): 1, more preferably (1.1 to 1.4): 1, most preferably (1.2 to 1.3): 1. in the invention, the tea polyphenol is used as a reducing agent and a stabilizing agent of a silver source. The invention limits the quantity ratio of the tea polyphenol to the silver source in the range, can fully reduce the silver source to form the nano silver, and ensures that the nano silver is dispersed more uniformly.

In the present invention, the water is preferably deionized water.

In the present invention, the mixing manner of the silver source, tea polyphenol and water is preferably as follows: mixing a silver source with part of water to obtain a silver source solution; mixing tea polyphenols with the rest water, and adjusting pH to obtain tea polyphenols solution; the tea polyphenol solution was added dropwise to the silver source solution. In the present invention, the concentration of the silver source solution is preferably 0.02 to 0.06mol/L, more preferably 0.03 to 0.05mol/L, and most preferably 0.04mol/L. The invention limits the concentration of the silver source solution within the range, and can ensure that the generated nano silver has regular appearance, smaller size and narrower size distribution.

In the invention, the concentration of the tea polyphenol solution is preferably 0.05-0.06 g/mL; the pH value of the tea polyphenol solution is preferably 8.7-9.3, and more preferably 9. The invention limits the concentration and the pH value of the tea polyphenol solution within the range, and can ensure that the nano silver has smaller particle size and is dispersed more uniformly. The operation of adjusting the pH value of the tea polyphenol solution is not specially limited, and the pH value of the tea polyphenol solution can be ensured to be within the range. The invention preferably adds sodium hydroxide solution to adjust the pH value of the tea polyphenol solution. The concentration and the dosage of the sodium hydroxide solution are not specially limited, and the pH value of the tea polyphenol solution can be ensured to be in the range.

In the present invention, the rate of the dropwise addition is preferably 5 to 7mL/min, more preferably 6mL/min. In the invention, the dropping can ensure that the generated nano silver has smaller grain diameter and is not easy to agglomerate, thereby improving the performance of the product.

In the present invention, the temperature of the reduction reaction is preferably 15 to 25 ℃, more preferably 20 ℃; the time for the reduction reaction is preferably 1 to 3 hours, more preferably 2 hours. The invention limits the temperature and time of the reduction reaction in the range, and can ensure that the silver source fully reacts to generate the nano silver. In the invention, in the reduction reaction process, the silver source is reduced to generate nano silver, and the oxidation product of the tea polyphenol and the unreacted tea polyphenol are adsorbed on the surface of the nano silver to obtain the composite antibacterial agent.

After the reduction reaction is finished, the product of the reduction reaction is preferably frozen and dried to obtain the composite antibacterial agent.

In the present invention, the temperature of the freeze-drying is preferably-50 to-30 ℃, more preferably-40 ℃; the time for freeze-drying is preferably 12 to 36 hours, more preferably 24 hours.

After the composite antibacterial agent is obtained, the composite antibacterial agent is mixed with polylactic acid, a solvent and a coupling agent to obtain the skin layer spinning solution.

In the present invention, the average molecular weight of the polylactic acid is preferably 70000 to 90000, and more preferably 80000. The invention limits the molecular weight of the polylactic acid within the range, and can ensure that the fiber membrane has better mechanical property.

In the present invention, the mass concentration of the polylactic acid in the sheath spinning solution is preferably 4 to 6%, and more preferably 5%. According to the invention, the mass concentration of the polylactic acid in the skin layer spinning solution is limited within the range, so that the polylactic acid can be fully dissolved, and meanwhile, the skin layer spinning solution has relatively proper viscosity, which is beneficial to electrostatic spinning.

In the present invention, the mass ratio of the composite antibacterial agent to the polylactic acid is preferably (0.5 to 3): 5, more preferably (1 to 2): 5. The invention limits the mass ratio of the composite antibacterial agent to the polylactic acid within the range, so that the composite antibacterial agent can be uniformly dispersed in the polylactic acid, and the fiber membrane has excellent antibacterial performance and mechanical performance.

In the present invention, the solvent preferably includes N, N-dimethylformamide and dichloromethane; the mass ratio of the dichloromethane to the N, N-dimethylformamide is preferably (2 to 3): 1, more preferably (2.2 to 2.8): 1, most preferably (2.4 to 2.6): 1. in the present invention, the kind of the solvent and the mass ratio of the solvent to the solvent are limited to the above ranges, and the respective components can be dissolved more sufficiently.

The invention has no special limitation on the dosage of the solvent, and the mass concentration of the polylactic acid in the sheath spinning solution is ensured to be within the range.

In the present invention, the coupling agent is preferably a silane coupling agent, and more preferably a silane coupling agent KH550 or KH560. In the invention, the coupling agent can improve the compatibility of the composite antibacterial agent and the polylactic acid, and further improve the performance of the fiber membrane.

In the present invention, the mass ratio of the coupling agent to the composite antibacterial agent is preferably (0.05 to 0.2): 1, more preferably 0.1. According to the invention, the mass ratio of the coupling agent to the composite antibacterial agent is limited in the range, so that the composite antibacterial agent and the polylactic acid have better compatibility.

In the present invention, the mixing manner of the composite antibacterial agent with the polylactic acid, the solvent and the coupling agent is preferably: mixing the composite antibacterial agent and the coupling agent, and performing ultrasonic treatment for 0.5-1 h under the condition of 400-500W to obtain a mixed solution; mixing polylactic acid and dichloromethane, magnetically stirring for 1-3 h at 500-800 rpm, adding N, N-dimethylformamide, continuously stirring for 1-2 h, adding the mixed solution, and continuously stirring for 1-3 h. By adopting the mixing mode of the invention, the components can be dissolved and dispersed more fully.

The invention mixes polylactic acid and solvent to obtain the core layer spinning solution.

In the present invention, the mass concentration of the polylactic acid in the core layer spinning solution is preferably 4 to 6%, and more preferably 5%. According to the invention, the mass concentration of the polylactic acid in the core layer spinning solution is limited within the range, so that the polylactic acid can be fully dissolved, and meanwhile, the core layer spinning solution has relatively proper viscosity, which is beneficial to electrostatic spinning.

The invention has no special limitation on the dosage of the solvent, and the mass concentration of the polylactic acid in the core layer spinning solution is ensured to be within the range.

In the present invention, the polylactic acid and the solvent are preferably mixed in the following manner: mixing polylactic acid and dichloromethane, magnetically stirring for 1-3 h at 500-800 rpm, adding N, N-dimethylformamide, and continuously stirring for 1-2 h.

After the skin layer spinning solution and the core layer spinning solution are obtained, the invention carries out coaxial electrostatic spinning on the skin layer spinning solution and the core layer spinning solution to obtain the polylactic acid antibacterial composite fiber membrane.

In the electrostatic spinning process, the skin layer spinning solution and the core layer spinning solution are respectively injected into an injector, an electrostatic spinning needle head is inserted, the needle head is aligned to the center of the aluminum foil receiving device and is positioned at the same height with the center, the needle head is connected with the positive pole of a high-voltage current power supply, the aluminum foil receiving device is grounded, and electrostatic spinning is started.

In the present invention, the spinning voltage of the coaxial electrospinning is preferably 14 to 16kV, more preferably 15kV; the spinning distance of the coaxial electrostatic spinning is preferably 8-14 cm, and more preferably 10-12 cm; the independent advancing speed of the skin layer spinning solution and the core layer spinning solution in the coaxial electrostatic spinning is preferably 1-2 mL/h, and more preferably 1.5mL/h. The invention limits the spinning voltage, the spinning distance and the spinning solution advancing speed of the coaxial electrostatic spinning within the above ranges, can ensure that the spinning solution is fully stretched and split to form fibers, and the solvent has proper volatilization rate in the spinning process, so that the fiber diameter is more uniform, and the performance of the fiber membrane is further improved.

According to the invention, the nano-silver composite antibacterial agent is prepared by adopting the tea polyphenol biological reduction silver source, so that the nano-silver composite antibacterial agent has excellent antibacterial performance and can improve the antibacterial property of the fiber membrane; meanwhile, the skin-core composite fiber membrane is prepared by adopting coaxial electrostatic spinning, the mechanical property of the composite fiber membrane is improved, and the dosage of each component and each process parameter are controlled, so that the composite fiber membrane has excellent antibacterial property and mechanical property.

The invention also provides the polylactic acid antibacterial composite fiber membrane prepared by the preparation method of the technical scheme.

The polylactic acid antibacterial composite fiber membrane provided by the invention has excellent antibacterial property and mechanical property.

The operation of the application of the polylactic acid antibacterial composite fiber membrane in the antibacterial field is not particularly limited, and the technical scheme of the application of the polylactic acid antibacterial composite fiber membrane in the antibacterial field, which is well known to the technical personnel in the field, can be adopted.

The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It should be apparent that the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

(1) Dissolving 0.17g of silver nitrate in 25mL of deionized water to obtain 0.04mol/L silver nitrate solution;

(2) Dissolving 0.3372g of tea polyphenol (the mass ratio of the tea polyphenol to the silver nitrate is 1.2;

(3) Dripping the tea polyphenol solution into silver nitrate solution at the speed of 6mL/min, reacting for 2h at 20 ℃, and then freeze-drying for 24h at-40 ℃ to obtain a composite antibacterial agent Ag @ TP;

(4) Mixing the composite antibacterial agent with a coupling agent KH550, and carrying out ultrasonic treatment at 450W for 30min to obtain a mixed solution (the mass ratio of the coupling agent to the composite antibacterial agent is 0.1;

(5) Dissolving polylactic acid (average molecular weight 80000) in dichloromethane, magnetically stirring for 2h at 700rpm, adding N, N-dimethylformamide (the mass ratio of dichloromethane to N, N-dimethylformamide is 7); adding the mixed solution obtained in the step (4) (the mass ratio of the composite antibacterial agent to the polylactic acid is 0.5;

(6) Dissolving polylactic acid (average molecular weight 80000) in dichloromethane, magnetically stirring for 2 hours at 700rpm, adding N, N-dimethylformamide (the mass ratio of dichloromethane to N, N-dimethylformamide is 7), and continuously stirring for 1 hour to obtain a core layer spinning solution (the mass concentration of polylactic acid in the core layer spinning solution is 5%);

(7) Respectively injecting the skin layer spinning solution and the core layer spinning solution into a 10mL injector, fixing the injector in a clamping groove of a micro injection pump, inserting an 18G electrostatic spinning needle, enabling the needle to be aligned with the center of an aluminum foil receiving device and be positioned at the same height with the center, connecting the needle with the anode of a high-voltage current power supply, grounding the aluminum foil receiving device, and starting coaxial electrostatic spinning under the conditions that the spinning voltage is 15kV, the spinning distance is 10cm, and the propelling speed of each spinning solution is 1.5mL/h to obtain the polylactic acid antibacterial composite fiber membrane PLA/Ag @ TP-0.5%.

Example 2

The mass ratio of the composite antibacterial agent to the polylactic acid in the example 1 is replaced by 1.

Example 3

The mass ratio of the composite antibacterial agent to the polylactic acid in the example 1 is replaced by 1.5, and other parameters are the same as those in the example 1, so that the polylactic acid antibacterial composite fiber membrane PLA/Ag @ TP-1.5% is obtained.

Example 4

The mass ratio of the composite antibacterial agent to the polylactic acid in the example 1 is replaced by 2.

Example 5

The mass ratio of the composite antibacterial agent to the polylactic acid in the example 1 is replaced by 3, and other parameters are the same as those in the example 1, so that the polylactic acid antibacterial composite fiber membrane PLA/Ag @ TP-3% is obtained.

Comparative example 1

(1) Dissolving polylactic acid (average molecular weight 80000) in dichloromethane, magnetically stirring for 2 hours at 700rpm, adding N, N-dimethylformamide (the mass ratio of dichloromethane to N, N-dimethylformamide is 7, 3), and continuously stirring for 1 hour to obtain an electrostatic spinning solution (the mass concentration of polylactic acid in the electrostatic spinning solution is 5%);

(2) Injecting the electrostatic spinning solution into a 10mL injector, fixing the injector in a clamping groove of a micro injection pump, inserting an 18G electrostatic spinning needle head, aligning the needle head to the center of an aluminum foil receiving device and enabling the needle head to be located at the same height with the center, connecting the needle head to a positive electrode of a high-voltage current power supply, grounding the aluminum foil receiving device, and starting coaxial electrostatic spinning under the conditions that the spinning voltage is 15kV, the spinning distance is 10cm, and the spinning solution propelling speed is 1.5mL/h to obtain the pure polylactic acid fiber membrane PLA.

Comparative example 2

The mass ratio of dichloromethane to N, N-dimethylformamide in example 1 was 6, and other parameters were the same as in example 1.

Comparative example 3

The mass ratio of dichloromethane to N, N-dimethylformamide in example 1 was 8, and other parameters were the same as in example 1.

Scanning electron micrographs of the fiber films prepared in example 1, comparative example 2 and comparative example 3 were measured using an electron scanning microscope (S-1800, hitachi, 15kV), and the results are shown in FIGS. 1 to 4. FIG. 1 is a scanning electron micrograph of the fibrous membrane prepared in example 1 at 3000 magnifications; FIG. 2 is a scanning electron micrograph of the fibrous membrane prepared in example 1 at 5000 magnifications; FIG. 3 is a scanning electron micrograph of a fibrous membrane prepared in comparative example 2;

fig. 4 is a scanning electron microscope image of the fiber film prepared in comparative example 3. As can be seen from fig. 1 to 4, the fibers on the fiber membrane prepared in comparative example 2 are too fine and random to form a membrane; the fibers on the fiber membrane prepared in comparative example 3 were too cohesive and had a doubling phenomenon; the fibers on the fiber membrane prepared in the example 1 have no obvious bonding phenomenon and are longer; the solvent ratio in example 1 is preferably as described below.

Scanning electron micrographs of the fiber films prepared in examples 2 to 5 and comparative example 1 were measured by an electron scanning microscope (S-1800, hitachi, 15kV), and the results are shown in FIGS. 5 to 10. FIG. 5 is a scanning electron micrograph of the fibrous membrane prepared in comparative example 1 at 3000 magnifications; FIG. 6 is a scanning electron micrograph of the fibrous membrane prepared in comparative example 1 at 5000 magnification; FIG. 7 is a scanning electron micrograph of a fibrous membrane prepared according to example 2; FIG. 8 is a scanning electron micrograph of a fibrous membrane prepared according to example 3; FIG. 9 is a scanning electron micrograph of a fibrous membrane prepared according to example 4; FIG. 10 is a scanning electron micrograph of the fiber film prepared in example 5. As can be seen from fig. 5 to 10, the pure polylactic acid fiber prepared in comparative example 1 has a smooth surface and a random coherent porous structure; the fiber membrane prepared in the example 2 is messy and has a doubling phenomenon; the fiber membrane prepared in example 3 has uneven fiber thickness and curls; the fiber membrane prepared in the embodiment 4 has uniform fiber thickness, is porous and coherent, and has stacked fiber layers and small pores; the fiber membrane prepared in example 5 is coarse and non-uniform; in conclusion, the fibers prepared in example 4 have better morphology.

The infrared spectrograms of the fiber films prepared in examples 2 to 5 and comparative example 1 were measured by an infrared spectrometer (TL-8000, PE company, USA), and the results are shown in FIG. 11. As can be seen in FIG. 11, the IR spectrum of the composite fiber film was at 869cm ^-1 ，1079cm ^-1 And 1181cm ^-1 ，1370cm ^-1 ，1454cm ^-1 ，1754cm ^-1 The C-C stretching vibration peak, the C-O-C absorption peak, the C-H absorption peak and the methyl (-CH) of PLA appear ₃ ) Asymmetrically curved absorption peak and C = O absorption peak, further at 3400cm ^-1 A wider absorption band exists nearby, and is the characteristic absorption peak of phenolic hydroxyl (ArOH), which indicates that phenolic hydroxyl exists in molecules and the skeleton structure of tea polyphenol is basically reserved; at 1715cm ^-1 Characteristic absorption of carbonyl (-C = O), indicating that the reaction of tea polyphenol with metal compound occurs, and is 1617cm ^-1 A benzene ring absorption peak appears at the position, which indicates that the composite antibacterial agent is loaded on the PLA fiber film; 1037cm was seen as the content of the complex antimicrobial agent increased ^-1 The C-O-H stretching vibration absorption peak is gradually enhanced; in conclusion, the composite fiber membrane which is blended and spun by taking PLA as a carrier and Ag @ TP as an antibacterial agent is well compounded by combining valence bonds.

XRD patterns of the fiber films prepared in examples 2 to 5 and comparative example 1 were measured by XRD (TD-3700 model, dandongton technologies, ltd., angle range: 10 to 80 ℃ C.), and the results are shown in FIG. 12. As can be seen from fig. 12, the diffraction peak of the composite fiber film is different from the diffraction peak of the pure polylactic acid fiber film, and the composite fiber film has two relatively obvious characteristic diffraction peaks near 38.69 ° and 44.82 °, which are diffraction peaks belonging to silver nanoparticles, and the two diffraction peaks respectively correspond to the diffraction of (111) and (200) crystal planes of the simple substance silver in the face centered cubic system (JCPDS card No. 04-0783), which indicates that the prepared silver nanoparticle structure is a face centered cubic crystal, and further proves that the existence of silver particles in the composite fiber film increases the intensity of the diffraction peak of the fiber film with the increase of the composite antibacterial agent in the fiber film, that is, the crystallization performance of the fiber film increases, which may be due to the gradual increase of the proportion of the antibacterial agent in the composite fiber film.

And (3) testing antibacterial performance: the antibacterial performance of the fiber membrane is tested by a colony counting method by adopting gram-negative escherichia coli as an experimental strain;

and (3) culturing bacteria: (1) preparation of liquid culture medium: weighing 5g of beef extract on an electronic balance, then placing the beef extract into a large beaker with the capacity of 1000mL, sequentially placing 10g of peptone and 5g of sodium chloride powder, adding 1000mL of deionized water, uniformly stirring to dissolve the peptone and the sodium chloride powder, then adjusting the pH value to 7.5 by using a sodium hydroxide solution, pouring 250mL of the prepared solution into a conical flask, sealing the conical flask by using a cotton plug, opening an air volume controller of a clean bench, wiping the outer wall of the conical flask by using an alcohol cotton ball, then placing the conical flask on the clean bench, and keeping the rest liquid for later use; (2) preparation of experimental bacterial liquid: burning an inoculation spoon on a bacterial slant for 10s on an alcohol lamp, standing in a slant test tube for cooling, scraping a circle of thallus by using the inoculation spoon, inoculating the thallus into a liquid culture medium, carefully sealing a self-made absorbent cotton plug, putting the liquid culture medium with the bacteria into a gas bath constant-temperature oscillator, setting the constant temperature to be 37 ℃, the rotating speed to be 130r/min, culturing for 24 hours, adding 1ml of first-generation original bacterial liquid into 100ml of liquid culture medium, continuously oscillating for 12 hours in the oscillator at 37 ℃ and 130r/min to obtain second-generation original bacterial liquid, diluting 1ml of second-generation original bacterial liquid by 100 times by using the liquid culture medium, and further diluting by 100 times by using sterile PBS buffer solution to obtain bacterial liquid for experiments; (3) preparation of sample (experimental group): weighing 0.12g of nanofiber membrane, placing a sample on an ultraclean workbench for ultraviolet irradiation for 2h to finish sterilization, then sequentially adding 700ml of sterile PBS buffer solution and 5ml of bacteria liquid for experiments, placing the prepared sample into a gas bath constant temperature oscillator, setting the constant temperature to be 25 ℃, setting the rotating speed to be 150r/min, and culturing for 24h; (4) preparation of solid culture medium: adding 7.5g of agar into the remaining liquid culture medium at the beginning, heating the mixture in a water bath to 100 ℃, uniformly stirring the mixture, putting the mixture into a conical flask, wiping the hands of a disinfection experimenter with an alcohol cotton ball to clean the two hands, the outer side of the conical flask and an ultra-clean workbench surface, standing until the liquid culture medium in the conical flask is cooled to about 55 ℃, touching the wall of the conical flask with a hand to be slightly heated, igniting an alcohol lamp, burning the mouth of the conical flask on the flame of the alcohol lamp for 10s, holding the conical flask with the right hand, opening the cover of a culture dish with the left hand, opening only a small slit on the cover, quickly pouring 25ml of the liquid culture medium into the culture dish, shaking the culture medium on the ultra-clean workbench slightly until no bubbles exist, standing for standby after cooling, opening an ultraviolet sterilization switch of the ultra-clean workbench, and sterilizing the culture medium under an ultraviolet lamp for 1h.

And (3) counting colonies: the cultured bacteria liquid of the experimental group is subjected to gradient dilution by 10 times by using sterile water, 3 gradients are diluted, each gradient is made into two flat plates, the two plates are mutually contrasted, each group of samples is made into 6 flat plates, 100 mu L of the diluted bacteria liquid of each gradient is coated in a solid culture medium, the coated flat plates are immediately put into an incubator, the temperature is set to be 37 ℃, the growth condition of bacterial colonies is observed after 24h of culture, the number of the bacterial colonies is photographed and recorded, and the average number of the two contrast flat plates is taken to reduce experimental errors. Obtaining the bacteriostasis rate of the fiber membrane according to a formula:

I％＝(Nc-Ns)/Nc×100％，

wherein Nc and Ns are the bacterial colony numbers of the bacterial liquid of the polylactic acid fiber membrane after contacting with pure polylactic acid and adding the antibacterial agent and cultured on the surface of the culture medium on a flat solid culture medium respectively.

The test results are shown in fig. 13. In FIG. 13, a is a blank control group; b, adding the pure polylactic acid fiber membrane prepared in the comparative example 1; c adding the fiber membrane prepared in example 2; d adding the fiber membrane prepared in example 3; e adding the fibrous membrane prepared in example 4; f fibrous membrane prepared in example 5 was added. As can be seen from fig. 13, when the plate to which the pure polylactic acid fiber membrane prepared in comparative example 1 was added was used as a control, the relative bacteriostatic rate was calculated, and the pure polylactic acid fiber membrane had a large specific surface area, a high porosity, a strong adsorbability, and an adsorbability to bacteria, so the number of bacteria was smaller than that on the blank plate; the antibacterial property is gradually enhanced along with the increase of the content of the antibacterial agent, and the bacteriostasis rate of the fiber membrane prepared in example 4 reaches 100 percent.

And (3) testing mechanical properties: three samples are taken as a group, the shape of each sample is a strip with the length being 40 x 2 (mm), the tensile breaking strength of the sample is measured by an electronic single fiber strength tester, the lower end of the sample is clamped by a metal clamp, the measured sample is in a vertical state, then the sample is placed between two chucks of the electronic single fiber strength tester, and the chucks are used for fixing and keeping static, and the distance between the chucks is about 10mm. Throughout the test, ensuring uniform loading and recording the breaking force F (N) on the display screen after the sample breaks, the three samples were averaged to reduce the error, the results are shown in fig. 14. As can be seen from fig. 14, the breaking strength of the prepared nanofiber membrane is relatively small, but the breaking strength of the nanofiber membrane is increased after the antibacterial agent is added, because the small amount of 0.5% and 1% of ag @ tp particles is only equivalent to that impurities are embedded in the nanofibers, so that the PLA nanofibers are not long enough and are easily broken. Along with the increase of the antibacterial agent, the breaking elongation of the breaking strength is gradually increased, and after the content of the antibacterial agent is 1.5%, the breaking elongation exceeds that of a pure polylactic acid nanofiber membrane, so that the mechanical property of the composite nanofiber membrane can be improved along with the increase of the content of the antibacterial agent, because along with the addition of the nanoparticles, when the nanofiber membrane is subjected to an external force, the Ag @ TP particles play a role in transferring and transferring energy, and the external force acting on the nanofiber membrane is consumed.

Contact angle test: the static water contact angle of the sample is measured to indicate the hydrophilicity of the membrane and the test liquid is distilled water. Two samples each having a shape of a square of 2 × 2 (cm) in length were set, the samples were placed on a stage, the samples were leveled, a liquid was pressed out using a micro-syringe, a clear droplet was observed on the image by freezing the image within 10s as much as possible, the magnitude of the contact angle was measured by the goniometric method, the right contact angle was determined as a supplementary angle, and the two samples were averaged to reduce the error, as shown in fig. 15, wherein (a) is the contact angle of the pure polylactic acid fiber film prepared in comparative example 1, and (b) is the contact angle of the fiber film prepared in example 4. As can be seen from fig. 15, the pure polylactic acid nanofiber membrane is a hydrophobic membrane, and the addition of the antibacterial agent improves the hydrophobicity of the polylactic acid nanofiber membrane.

Contact angle data of the fiber membranes prepared in examples 1 to 5 and comparative example 1 are shown in table 1.

TABLE 1 contact angles of fiber membranes prepared in examples 1 to 5 and comparative example 1

The XRD pattern of the composite antibacterial agent prepared in example 1 was tested, and the result is shown in fig. 16. As can be seen from fig. 16, the graph conforms to the data on 04-0783 of the JCPDS card (2 θ is 38.096 °,44.257 °,64.406 ° and 77.452 °), which correspond to the (111), (200), (220) and (311) crystal planes of cubic silver, respectively, and shows that the resulting material is face-centered cubic pure phase elemental silver, with relatively pure particles and almost few impurity ions.

The ultraviolet-visible absorption spectrum of the composite antibacterial agent prepared in example 1 was tested, and the results are shown in fig. 17. As can be seen from FIG. 17, the absorption peak is around 380-420nm, which is consistent with the absorption peak of the nano-silver particles.

The antibacterial performance of the composite antibacterial agent prepared in example 1 was tested, and the results are shown in fig. 18. In the figure, (a) does not contain a composite antimicrobial agent, and (b) to (d) contain the same amount of the composite antimicrobial agent. Calculating the bacteriostasis rate of the composite antibacterial agent as follows:

in conclusion, the composite fiber membrane prepared by the invention has excellent antibacterial performance and mechanical strength.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and amendments can be made without departing from the principle of the present invention, and these modifications and amendments should also be considered as the protection scope of the present invention.

Claims

1. A preparation method of a polylactic acid antibacterial composite fiber membrane comprises the following steps:

the steps (1) and (3) are not in sequence;

the ratio of the amount of the tea polyphenol to the amount of the silver source substance in the step (1) is (1-1.5): 1;

the mass ratio of the composite antibacterial agent to the polylactic acid in the step (2) is (0.5-3): 5.

2. the method according to claim 1, wherein the solvent in the steps (2) and (3) comprises N, N-dimethylformamide and dichloromethane.

3. The production method according to claim 2, wherein the mass ratio of the dichloromethane to the N, N-dimethylformamide is (2 to 3): 1.

4. the preparation method according to claim 1, wherein the mass concentration of the polylactic acid in the skin layer spinning solution in the step (2) is 4-6%.

5. The production method according to claim 1, wherein the coupling agent in the step (2) comprises a silane coupling agent; the mass ratio of the coupling agent to the composite antibacterial agent is (0.05-0.2): 1.

6. the preparation method according to claim 1, wherein the spinning voltage of the coaxial electrospinning in the step (4) is 14 to 16kV; the spinning distance of the coaxial electrostatic spinning is 8-14 cm; the propelling speeds of the skin layer spinning solution and the core layer spinning solution are independent and are 1-2 mL/h in coaxial electrostatic spinning.

7. The polylactic acid antibacterial composite fiber membrane prepared by the preparation method of any one of claims 1 to 6.

8. The polylactic acid antibacterial composite fiber membrane of claim 7, which is applied to the antibacterial field.