A tannic acid-imidazolium / polyacrylamide composite hydrogel, its preparation method and application

Abstract

This invention belongs to the field of antibacterial materials, specifically relating to a tannic acid-imidazolium / polyacrylamide composite hydrogel, its preparation method, and its applications. This invention successfully prepared a tannic acid-imidazolium organic complex by directly polymerizing antibacterial units and incorporated it into the network structure of the hydrogel. Systematic testing showed that this material exhibits significant antibacterial effects against Staphylococcus aureus and Escherichia coli, with inhibition zone diameters exceeding 30 mm. Furthermore, the material also demonstrates good antioxidant and adhesive properties. As a novel antibacterial material, this composite hydrogel has broad application potential. The tannic acid-imidazolium / polyacrylamide composite hydrogel prepared by this invention not only possesses dual antibacterial effects and chemical stability but also exhibits excellent hydrogel properties and a wide range of applications, further enhancing its application potential as a novel antibacterial material.

Description

Technical Field

[0001] This invention belongs to the field of antibacterial materials, specifically relating to a tannic acid-imidazolium / polyacrylamide composite hydrogel, its preparation method, and its application. Background Technology

[0002] Antibiotics are currently the main drugs for treating bacterial infections, but their overuse and inappropriate use have led to serious drug resistance problems, posing a significant threat to public health. To address this challenge, researchers are actively exploring the synthesis of compounds with unique antibacterial activities. Antibacterial hydrogels show great promise in the treatment of chronic wounds, particularly in addressing the challenge of antibiotic resistance (AMR). However, traditional techniques such as silver-based dressings suffer from toxicity issues and have a narrow antibacterial spectrum. While low-temperature plasma-activated hydrogels (PAHT) achieve both bactericidal and healing effects through the dual action of reactive oxygen species (ROS) and nitrogenous substances (RONS), the precise control of RONS loading and release limits their effectiveness.

[0003] Currently, tannic acid (TA) hydrogels have been reported to damage the external structure of Candida albicans, and the degree of damage increases with increasing concentration. Therefore, how to utilize tannic acid and imidazole compounds to prepare gel antibacterial materials with good synergistic effects and exert their protective effect on wounds is an important issue in current industrial research. Summary of the Invention

[0004] In view of this, the present invention discloses a tannic acid-imidazolium / polyacrylamide composite hydrogel, its preparation method and application.

[0005] It should be noted that tannic acid provides antibacterial and antioxidant effects, while imidazole enhances the mechanical properties and tolerance of the composite hydrogel. The combination of these two components achieves broad-spectrum antibacterial activity, while optimizing antibacterial agent loading and controlled release, forming a durable antibacterial barrier, and promoting wound healing. This approach combines high efficiency and biocompatibility, providing an innovative solution for upgrading traditional dressings. Therefore, hydrogels designed based on tannic acid-imidazole complexes offer new solutions for synergistic enhancement of antibacterial activity, multifunctional integration, and toxicity management, opening new pathways for chronic wound treatment and antibacterial agent replacement.

[0006] Furthermore, this invention successfully prepared a tannic acid-imidazolium organic complex by directly polymerizing antibacterial units and introduced it into the network structure of a hydrogel. This composite hydrogel material exhibits excellent swelling properties, mechanical stability, and significant antibacterial effects against Staphylococcus aureus and Escherichia coli under various conditions, while also possessing a high free radical scavenging rate, demonstrating its application potential in the fields of biomedicine, packaging, and public health.

[0007] Specifically, the tannic acid-imidazolium composite polymer forms a stable structure through hydrogen bonding and chemical cross-linking, and its infrared spectrum ( Figure 12 The characteristics indicate that: in the range of 3300-3500cm -1 Within the range, the absorption peaks of hydroxyl and NH decrease and red shift, indicating enhanced hydrogen bonding; 1000-1100 cm⁻¹ -1 The newly added characteristic peaks are attributed to the formation of ether bonds (COC) and amine bonds (CN). Subsequently, acrylamide initiates an in-situ free radical polymerization reaction, and the tannic acid-imidazolium composite polymer and polyacrylamide significantly improve the compactness of the gel network through hydrogen bonding of functional groups such as polyphenols and amides. The multi-point chemical cross-linking of the composite provides structural support for the gel, while trapping antibacterial agent molecules in the pores, enhancing its loading capacity and controlled release performance. The honeycomb three-dimensional network of this composite hydrogel effectively improves porosity and antibacterial agent loading capacity.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] The first objective of this invention is to provide a method for preparing tannic acid-imidazolium / polyacrylamide composite hydrogels.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] A method for preparing a tannic acid-imidazolium / polyacrylamide composite hydrogel, the method specifically comprising the following steps:

[0012] (1) Dissolve tannic acid in deionized water to obtain a tannic acid solution; then take a certain mass fraction of the tannic acid solution, add tannic acid and imidazole in a suitable ratio, and stir in an ice-water bath for a certain time;

[0013] (2) A certain amount of epichlorohydrin was added dropwise to the reaction system in step (1) at a rate of 0.5 mL / min, and the reaction continued. After the reaction was completed, the mixture was centrifuged and freeze-dried to obtain tannic acid-imidazolium composite polymer (TIP).

[0014] (3) Add the tannic acid-imidazolium composite polymer TIP to deionized water and heat to dissolve. Add acrylamide (AM), ammonium persulfate (APS) and N,N'-methylenebisacrylamide (BIS), stir and place in an oven overnight. Use APS thermally initiated free radical polymerization to prepare composite hydrogel.

[0015] Optionally, in step (1), the mass fraction of the tannic acid solution is 0.5% to 30%, the molar ratio of tannic acid to imidazole is 1:1 to 1:20, and the stirring time is 0.5-5h.

[0016] Optionally, in step (2), 0.5-15 mL of epichlorohydrin is added to a 50 mL mixture of tannic acid and imidazole, and the reaction is continued in an ice-water bath for 8-24 h.

[0017] Optionally, in step (2), after the reaction is completed, the tannic acid-imidazolium composite polymer is centrifuged at 3000-10000 rpm for 5 min to 1 h, and then freeze-dried to obtain the tannic acid-imidazolium composite polymer.

[0018] Optionally, in step (3), the amount of tannic acid-imidazolium composite polymer is 0.01-2g, the amount of deionized water is 5-100mL, the amount of acrylamide monomer added is 5mg-15g, and after thorough stirring, 5mg-1g of ammonium persulfate and 5mg-1g of N,N'-methylenebisacrylamide are added to the solution respectively, and after stirring evenly, a prepolymer solution is obtained.

[0019] Furthermore, in step (3), the temperature of the tannic acid-imidazolium / polyacrylamide prepolymer solution placed in the oven is 20℃~100℃, and the overnight preparation time is 30min~12h.

[0020] To fully disclose the key technical points of this case, the preferred method for preparing the above-mentioned tannic acid-imidazolium / polyacrylamide composite hydrogel is as follows:

[0021] Take 50 mL of 6% tannic acid aqueous solution and dissolve it in an ice-water bath for 1 h at a molar ratio of tannic acid to imidazole of 1:13. Then add epichlorohydrin with the same molar amount as imidazole and continue the reaction for 1.5 h to obtain tannic acid-imidazole composite polymer. The total phenol content is determined to be >90% by the Folin-Ciocalteu method. Dissolve 0.4 g of tannic acid-imidazole composite polymer in 20 mL of deionized water, then add 7.5 g of acrylamide monomer. After stirring thoroughly, add 0.3 g of ammonium persulfate and 0.75 g of N,N'-methylenebisacrylamide to the solution and stir evenly to obtain a prepolymer solution. Place the beaker containing the prepolymer solution in a 60 °C oven for 6 h to prepare tannic acid composite imidazole / polyacrylamide composite antibacterial hydrogel.

[0022] The second technical objective of this invention is to provide a tannic acid-imidazolium / polyacrylamide composite hydrogel prepared using the above method.

[0023] It should be noted that the microstructure of the tannic acid-imidazolium / polyacrylamide complex is a porous structure formed by the tannic acid-imidazolium complex and polyacrylamide, with well-developed pores and imidazolium uniformly distributed inside the gel, such as... Figure 7 As shown.

[0024] It is worth noting that the purpose of this invention is to address the problem of increased bacterial resistance caused by antibiotic overuse. A novel antibacterial material has been successfully prepared through the direct polymerization of antibacterial units. This material not only possesses dual antibacterial effects but also exhibits high chemical stability, superior hydrogel properties, and a wide range of applications. These characteristics make the tannic acid-imidazolium / polyacrylamide composite hydrogel a promising candidate for applications in food, packaging, and medical fields, and it holds significant importance for improving public health and promoting sustainable health development.

[0025] The third technical objective of this invention is to provide an application of the tannic acid-imidazolium / polyacrylamide composite hydrogel as described above in biomedicine, packaging, and public health.

[0026] Specifically, the tannic acid-imidazolium / polyacrylamide composite hydrogel described in this invention has a significant antibacterial effect against Staphylococcus aureus and Escherichia coli, with an inhibition zone diameter of over 30 mm.

[0027] Escherichia coli and Staphylococcus aureus strains were inoculated into beef jelly liquid medium and cultured overnight. After incubation, composite hydrogels were placed into the wells and cultured for 24-48 hours. Bacterial viability was then counted using a colony count / inhibition zone measurement instrument.

[0028] Furthermore, Escherichia coli and Staphylococcus aureus strains were inoculated into 0–1000 mL of beef jelly liquid culture medium and cultured overnight at 37°C and 150–1000 r / min on a shaker for later use.

[0029] Furthermore, the Escherichia coli and Staphylococcus aureus bacterial cultures were placed in a constant temperature incubator (37℃, 150rpm) and cultured with shaking for 0.5–2 hours, and then diluted 10–100,000 times with sterile PBS.

[0030] Compared with the prior art, the beneficial effects of the present invention are:

[0031] 1. The tannic acid-imidazolium / polyacrylamide composite hydrogel prepared by this invention is an antibacterial material for wounds that is simple to produce, inexpensive, and can be used to inhibit bacteria and fungi.

[0032] 2. The tannic acid-imidazolium / polyacrylamide composite hydrogel prepared in this invention uses imidazolium, which has the simplest structure, and its cost is much lower than that of other modified imidazolium derivatives prepared to improve antibacterial efficiency.

[0033] 3. The tannic acid-imidazolium / polyacrylamide composite hydrogel prepared by this invention has a high compression modulus, the imidazolium in the composite material is uniformly distributed, the internal pores of the material are well developed, the tannic acid-imidazolium composite polymer is not easily lost, and the antibacterial effect is long-lasting.

[0034] 4. The tannic acid-imidazolium / polyacrylamide composite hydrogel provided by the present invention can be used as an antibacterial wound gel. It has strong adhesion and self-healing properties. The antibacterial gel prepared by it can not only cover the wound well, but can also be used multiple times. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0036] Figure 1 This is a graph showing the antibacterial effect of tannic acid-imidazolium / polyacrylamide composite hydrogel on Staphylococcus aureus after 24 hours.

[0037] Figure 2 The image shows the antibacterial effect of tannic acid-imidazolium / polyacrylamide composite hydrogel on Escherichia coli after 24 hours.

[0038] Figure 3 This is a graph showing the antioxidant properties of tannic acid-imidazolium / polyacrylamide composite hydrogel against DPPH.

[0039] Figure 4 This is a graph showing the antioxidant properties of tannic acid-imidazolium / polyacrylamide composite hydrogel against ABTS.

[0040] Figure 5 This is a diagram showing the mechanical properties of the tannic acid-imidazolium / polyacrylamide composite hydrogel.

[0041] Figure 6 This is a diagram showing the swelling properties of the tannic acid-imidazolium / polyacrylamide composite hydrogel.

[0042] Figure 7 This is a scanning electron microscope image of a tannic acid-imidazolium / polyacrylamide composite hydrogel.

[0043] Figure 8 This is a graph showing the compression modulus-elongation of tannic acid-imidazolium / polyacrylamide composite hydrogel.

[0044] Figure 9 This is a graph showing the compressive modulus-time of a tannic acid-imidazolium / polyacrylamide composite hydrogel.

[0045] Figure 10 This is a graph showing the compression modulus-temperature of tannic acid-imidazolium / polyacrylamide composite hydrogel.

[0046] Figure 11 This is a graph showing the compressive modulus-angular velocity of a tannic acid-imidazolium / polyacrylamide composite hydrogel.

[0047] Figure 12 This is the infrared spectrum of imidazole, tannic acid, and tannic acid-imidazole / polyacrylamide composite hydrogels. Detailed Implementation

[0048] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0049] The term "embodiment" used herein, as an example, is not necessarily to be construed as superior to or better than other embodiments. Performance testing in the embodiments of this application, unless otherwise specified, employs conventional testing methods in the art. It should be understood that the terminology used in this application is merely for describing particular implementations and is not intended to limit the scope of this disclosure.

[0050] Unless otherwise stated, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; other experimental methods and technical means not specifically mentioned herein refer to experimental methods and technical means commonly used by one of ordinary skill in the art.

[0051] To better illustrate the content of this application, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that this application can be implemented even without certain specific details. In the embodiments, some methods, means, instruments, and devices well-known to those skilled in the art are not described in detail in order to highlight the main points of this application.

[0052] Without conflict, the technical features disclosed in the embodiments of this application can be combined arbitrarily, and the resulting technical solution belongs to the content disclosed in the embodiments of this application.

[0053] This invention discloses a method for preparing tannic acid-imidazolium / polyacrylamide composite hydrogel and its application.

[0054] To better understand the present invention, the following embodiments are provided for further detailed description of the present invention, but they should not be construed as limiting the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above-described invention are also considered to fall within the protection scope of the present invention.

[0055] Example 1:

[0056] Take 50 mL of 6% tannic acid aqueous solution and dissolve it in an ice-water bath for 1 h at a molar ratio of tannic acid to imidazole of 1:13. Then add epichlorohydrin with the same molar amount as imidazole and continue the reaction for 1.5 h to obtain tannic acid-imidazole composite polymer. Dissolve 0.4 g of tannic acid-imidazole composite polymer in 20 mL of deionized water, then add 7.5 g of acrylamide monomer. After stirring thoroughly, add 0.3 g of ammonium persulfate and 0.75 N,N'-methylenebisacrylamide to the solution and stir evenly to obtain a prepolymer solution. Place the beaker containing the prepolymer solution in a 60 °C oven for 6 h to prepare tannic acid composite imidazole / polyacrylamide composite antibacterial hydrogel.

[0057] In antibacterial performance tests, this material showed significant antibacterial effects against both Staphylococcus aureus and Escherichia coli, with an inhibition zone diameter of 35.285 mm (see attached image). Figure 1-2 In addition, this material also exhibits excellent antioxidant properties, with a DPPH free radical scavenging rate of up to 88.12% and an ABTS free radical scavenging rate of 81.68% (see appendix). Figure 3-4 The microstructure of the freeze-dried sample after water absorption equilibrium of the composite hydrogel exhibits a honeycomb structure, consistent with the characteristics of hydrogels with high water absorption properties (see attached image). Figure 7 ).

[0058] Example 2:

[0059] Referring to the preparation method of Example 1, the amount of tannic acid-imidazolium composite polymer added was modified to 0.1g, 0.2g, 0.3g and 0.5g, respectively. The antioxidant properties of the tannic acid-imidazolium / polyacrylamide hydrogel changed significantly. Its DPPH free radical scavenging rate was 78.09%, 87.54% and 82.15%; its ABTS free radical scavenging rate was 51.05%, 76.78%, 75.24% and 81.96%.

[0060] As a control, the polyacrylamide hydrogel showed virtually no scavenging effect on DPPH and ABTS free radicals.

[0061] Example 3:

[0062] Using Example 1, the water absorption equilibrium swelling ratio of the tannic acid-imidazolium / polyacrylamide composite hydrogel prepared after 24 hours was 607.65 times. Under the same conditions, the water absorption equilibrium swelling ratio of the polyacrylamide hydrogel was 696.41 times.

[0063] Changing the amount of tannic acid-imidazolium added to 0.1g, 0.2g, 0.3g, and 0.5g resulted in water absorption equilibrium swelling ratios of 544.04, 614.24, 684.75, and 702.69 times, respectively (see attached figure). Figure 6 ).

[0064] Example 4:

[0065] Using the tannic acid-imidazolium / polyacrylamide composite hydrogel prepared in Example 1, it was cut into rectangular blocks of a fixed size (20mm × 10mm × 5mm). A tensile test was then performed on the samples using a universal testing machine tensile clamp at a speed of 100mm / min. The hydrogel did not fracture at a strain length of 22mm, while the polyacrylamide gel fractured at 1.40mm. The gel strain ranged from 5.69mm to 16.48mm, and its shear force was approximately 4.59 N / mm². 2 At this point, the polyacrylamide gel exhibits a shear force of 1.92 N / mm at a strain of 4.5 mm. 2 Under these conditions, the crosslinking density and network structure of its gel are significantly improved; at the same time, it exhibits good adhesion to glass slides, rubber, stainless steel sheets, etc. (see attached image) Figure 5 ).

[0066] Example 5:

[0067] Using Example 1, the compressive modulus of the prepared tannic acid-imidazolium / polyacrylamide composite hydrogel was determined. The tensile test chart showed that the compressive modulus of the composite hydrogel at different tensile rates was always higher than that of the polyacrylamide hydrogel, exhibiting better resistance to deformation.

[0068] Under varying time and frequency conditions, the composite hydrogel exhibits superior storage modulus (G') and loss modulus (G") compared to the polyacrylamide hydrogel, demonstrating its better energy storage and dissipation capabilities. Particularly in the high-frequency range, the composite hydrogel shows a significant increase in G', indicating higher stability and strength under rapid repeated loading (see appendix). Figure 8-11 ).

[0069] Example 6:

[0070] 0.1 g of tannic acid-imidazolium composite polymer was dissolved in 20 mL of deionized water. The tannic acid-imidazolium / polyacrylamide composite hydrogel prepared according to the method in Example 1 showed that changing the amount of tannic acid added had a significant effect on the antibacterial effect against Staphylococcus aureus and Escherichia coli in the antibacterial performance test.

[0071] When the tannic acid solution concentrations were 8%, 10%, and 12%, the inhibition zone diameters against Staphylococcus aureus were 33.835 mm, 31.775 mm, and 35.541 mm, respectively. Furthermore, the inhibition zone diameters against Escherichia coli were 19.095 mm, 19.627 mm, and 19.767 mm, respectively.

[0072] Example 7:

[0073] Referring to the preparation method of Example 1, the amount of tannic acid-imidazolium composite polymer added was modified to 0.1g, 0.2g, 0.3g and 0.5g, respectively. The tensile energy of the tannic acid-imidazolium / polyacrylamide hydrogel changed significantly, with elongations at break of 6.012mm, 9.956mm, 8.520mm and ∞, respectively; the elongation at break of the control polyacrylamide hydrogel was only 1.406mm.

[0074] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a tannic acid-imidazolium / polyacrylamide composite hydrogel, characterized in that, The method specifically includes the following steps: (1) Dissolve tannic acid in deionized water to obtain a tannic acid solution; (2) The tannic acid solution was mixed with imidazole and stirred in an ice-water bath. Then epichlorohydrin was added dropwise and the reaction continued. After centrifugation, the mixture was freeze-dried to obtain the tannic acid-imidazole composite polymer. (3) Add the tannic acid-imidazolium composite polymer to the acrylamide solution, then add ammonium persulfate and N,N'-methylenebisacrylamide, and stir until homogeneous; (4) The reaction system of step (3) is heated and free radical polymerization is initiated. After a certain reaction time, the tannic acid-imidazolium / polyacrylamide composite hydrogel is prepared.

2. The method for preparing tannic acid-imidazolium / polyacrylamide composite hydrogel according to claim 1, characterized in that, The tannic acid solution has a mass fraction of 0.5% to 30%.

3. The method for preparing tannic acid-imidazolium / polyacrylamide composite hydrogel according to claim 1, characterized in that, The molar ratio of tannic acid to imidazole is 1:1 to 1:

20.

4. The method for preparing tannic acid-imidazolium / polyacrylamide composite hydrogel according to claim 1, characterized in that, The dosage of acrylamide is 5mg to 15g, the dosage of ammonium persulfate is 5mg to 1g, and the dosage of N,N'-methylenebisacrylamide is 5mg to 1g.

5. The method for preparing tannic acid-imidazolium / polyacrylamide composite hydrogel according to claim 1, characterized in that, Add 0.5-15 mL of epichlorohydrin to a 50 mL mixture of tannic acid and imidazole, and continue the reaction of the tannic acid and imidazole mixture with epichlorohydrin in an ice-water bath for 8-24 hours.

6. The method for preparing the tannic acid-imidazolium / polyacrylamide composite hydrogel according to claim 1, characterized in that, In step (2), the centrifugation speed is 3000-10000 rpm and the centrifugation time is 5 min to 1 h.

7. The method for preparing tannic acid-imidazolium / polyacrylamide composite hydrogel according to claim 1, characterized in that, The polymerization reaction temperature in step (4) is 20℃~100℃, and the reaction time is 30min~12h.

8. A tannic acid-imidazolium / polyacrylamide composite hydrogel prepared by the method described in claim 1.

9. The application of a tannic acid-imidazolium / polyacrylamide composite hydrogel prepared by the method of claim 1 or the tannic acid-imidazolium / polyacrylamide composite hydrogel of claim 8 in biomedicine, packaging and public health.

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