Preparation method of polyvinyl alcohol-lignin-carbohydrate compound gel

Abstract

The invention discloses a preparation method of a polyvinyl alcohol-lignin-carbohydrate compound gel. The preparation method specifically comprises the following steps: adding boric acid, ascorbic acid and N, N-methylene bisacrylamide into deionized water, and fully dissolving to obtain a solution A; adding polyvinyl alcohol into the solution A, heating and fully dissolving, and cooling to room temperature to obtain a solution B; and dissolving the lignin-carbohydrate compound and ammonium persulfate in deionized water, fully and uniformly mixing, adding into the solution B, and heating to fully react to obtain a gel product. The polyvinyl alcohol-lignin-carbohydrate compound gel prepared by the preparation method disclosed by the invention has the outstanding characteristics of excellent antibacterial property and good biocompatibility, and also has good swelling property, stability and relatively strong oxidation resistance. The preparation method of the gel disclosed by the invention has the advantages of simple process steps and low cost, and also avoids the problems of poor biocompatibility, increased toxicity and the like possibly caused by introduction of an antibacterial additive into the gel.

Description

Technical Field

[0001] The invention belongs to the technical field of gel dressing preparation, and particularly relates to a polyvinyl alcohol-lignin-carbohydrate composite gel. Background Art

[0002] As a new type of wound care product, gel dressing has a series of unique physical and chemical properties, such as good moisturizing performance, absorbency, buffering protection and biocompatibility. When covered on the surface of the wound, it can provide a wound with an environment conducive to healing. Different types of gel dressings have relatively different properties and functions due to differences in gel components. The gels currently used to prepare gel dressings mainly include the following: 1) Hydrogel, which is mainly composed of hydrophilic polymer materials (such as sodium polyacrylate), has good water absorption properties, can absorb a large amount of water and form a moist environment; 2) Alginate gel, which is a natural polysaccharide extracted from seaweed, such as sodium alginate, calcium alginate, etc. This type of gel can absorb exudate and form a gel-like substance; 3) Sodium carboxymethyl cellulose gel: It is a cellulose derivative with good hydrophilicity and absorbency.

[0003] Although these gels have been widely used in dressing preparation, some urgent problems remain. Poor antibacterial performance is a prominent and common problem, causing these gel dressings to infect wounds with bacteria, fungi, viruses, and other microorganisms during use. To address this issue, additives such as nanoparticles, metal ions, and antibiotics can be added to the gel to improve its antibacterial properties. However, this can complicate the preparation process and increase costs, and can even lead to problems such as poor biocompatibility and increased toxicity. Summary of the Invention

[0004] In view of the above problems, the present invention aims to provide a method for preparing a dressing gel with excellent antibacterial properties, good biocompatibility, simple process steps and low cost.

[0005] To achieve the above results, the present invention adopts the following technical solutions:

[0006] A method for preparing a polyvinyl alcohol-lignin-carbohydrate composite gel, characterized by comprising the following steps:

[0007] 1) Adding boric acid, ascorbic acid, and N,N-methylenebisacrylamide to deionized water and heating to fully dissolve them to obtain solution A;

[0008] 2) Add polyvinyl alcohol (PVA) to solution A, heat until fully dissolved, and then cool the solution to room temperature to obtain solution B;

[0009] 3) Dissolving lignin-carbohydrate complex (LCC) and ammonium persulfate in deionized water, mixing thoroughly until the solution is uniform, and then slowly adding to solution B. After heating to allow for a full reaction, a polyvinyl alcohol-lignin-carbohydrate complex gel is obtained.

[0010] Furthermore, the amounts of boric acid and ascorbic acid are 10-20% and 5-10% of the amount of polyvinyl alcohol, respectively, by mass ratio; the amounts of N,N-methylenebisacrylamide, lignin-carbohydrate complex and ammonium persulfate are all 2-5% of the amount of polyvinyl alcohol, by mass ratio.

[0011] Furthermore, the heating method in step 1) is water bath heating at a temperature of 40 to 50° C.; the heating method in step 2) is water bath heating at a temperature of 80 to 90° C., and the heating duration is 40 to 60 minutes; the heating method in step 3) is water bath heating at a temperature of 55 to 65° C., and the heating duration is 30 to 40 minutes.

[0012] Preferably, the lignin-carbohydrate complex is an acetic acid-treated lignin-carbohydrate complex (LCC-AcOH), or comprises an acetic acid-treated lignin-carbohydrate complex.

[0013] Furthermore, the lignin-carbohydrate complex is prepared by the following steps:

[0014] a. Filter the eucalyptus pre-hydrolyzate and concentrate it by rotary evaporation to 1 / 4 of its original volume;

[0015] b. After the concentrate has cooled, extract it with a 96:4 (v / v) 1,4-dioxane-water solution for 24 hours. Centrifuge the extracted liquid and store the supernatant at 4°C. Repeat the same extraction and centrifugation procedures twice for the precipitate obtained by centrifugation.

[0016] c. The supernatants obtained from the three centrifugations in step b were combined, rotary evaporated to dryness, and then dissolved in 90% acetic acid aqueous solution, centrifuged, and the obtained supernatant was added dropwise to water, centrifuged again, and the obtained supernatant was rotary evaporated to dryness; after repeating the process three times, the acetic acid-treated lignin-carbohydrate complex (LCC-AcOH) was obtained;

[0017] d. The precipitate after the third extraction and centrifugation in step b was dissolved in a 50% acetic acid aqueous solution and then centrifuged for 24 hours. This was repeated three times, and the supernatant obtained each time was collected, rotary evaporated to dryness, and then extracted with N,N-dimethylformamide; the supernatant obtained after centrifugation of the extract was added dropwise to ether and centrifuged. The obtained precipitate was vacuum-dried and then dissolved in a 50% acetic acid aqueous solution and centrifuged. The supernatant was added dropwise to acetone and centrifuged again. The obtained precipitate was vacuum-dried to obtain a lignin-carbohydrate complex (LCC).

[0018] The polyvinyl alcohol-lignin-carbohydrate complex gel prepared by the present invention has the outstanding characteristics of excellent antibacterial performance and good biocompatibility, and has good swelling performance, stability and strong antioxidant performance, and has a certain scavenging ability for DPPH and hydroxyl radicals. The raw materials for preparing the gel of the present invention are cheap and easy to obtain, and the lignin-carbohydrate complex used is derived from lignocellulosic biomass (such as wood, crop straw, etc.). These biomass materials are widely distributed and renewable in nature. In the present invention, instead of antibiotics, it is possible to avoid the development of drug resistance in wound pathogens and reduce adverse reactions. In addition, the gel preparation method of the present invention has the advantages of simple process steps and low cost, while also avoiding the problems such as poor biocompatibility and increased toxicity that may result from the introduction of antibacterial additives in the gel. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is the PVA fiber length distribution diagram;

[0020] Figure 2 is a scanning electron micrograph of PVA gel;

[0021] Figure 3 is the pore size distribution diagram of LCC-PVA gel;

[0022] Figure 4 is the scanning electron microscopy image of LCC-PVA gel;

[0023] Figure 5 is the pore size distribution diagram of LCC AcOH-PVA gel;

[0024] Figure 6 is the scanning electron microscopy image of LCC AcOH-PVA gel;

[0025] Figure 7 Comparison of the effects of swelling time on the swelling behavior of PVA, LCC-PVA and LCC AcOH-PVA gels;

[0026] Figure 8 TGA comparison of PVA, LCC-PVA and LCC AcOH-PVA gels;

[0027] Figure 9 Comparison of DPPH radical scavenging efficiency of PVA, LCC-PVA and LCC AcOH-PVA gels;

[0028] Figure 10 Comparison of OH radical scavenging rates of PVA, LCC-PVA, and LCC AcOH-PVA gels;

[0029] Figure 11Comparison of the antibacterial ability of PVA, LCC-PVA, LCC AcOH-PVA gel, LCC, and LCC-AcOH, where: a and b show the inhibition zones formed by each sample against Staphylococcus aureus in the culture dish; c and d show the inhibition zones formed by each sample against Escherichia coli. Specific implementation plan

[0030] The technical solution of the invention is further described below in conjunction with specific embodiments.

[0031] Example 1

[0032] Preparation of polyvinyl alcohol-lignin-carbohydrate complex gel (LCC-PVA) gel.

[0033] 1) Boric acid, ascorbic acid, and N,N-methylenebisacrylamide were added to deionized water and heated in a 40°C water bath while stirring to fully dissolve to obtain Solution A;

[0034] 2) Add polyvinyl alcohol (PVA) to solution A, heat in a water bath at 80°C for 50 minutes to fully dissolve it, and then allow the solution to stand at room temperature to cool naturally to room temperature, thereby obtaining solution B.

[0035] 3) Dissolve lignin-carbohydrate complex (LCC) and ammonium persulfate in deionized water, mix thoroughly until the solution is homogeneous, and then slowly add to solution B. Heat in a 60°C water bath for 30 minutes to allow for sufficient reaction to obtain LCC-PVA gel.

[0036] In each of the above steps, the addition ratios of the raw materials are as follows by mass: the amounts of boric acid and ascorbic acid are 10% and 5% of the amount of polyvinyl alcohol, respectively; the amounts of N,N-methylenebisacrylamide, LCC and ammonium persulfate are all 3.5% of the amount of polyvinyl alcohol, by mass.

[0037] In addition, the LCC in step 3 above is prepared by the following steps:

[0038] a. Filter the eucalyptus pre-hydrolyzate and concentrate it by rotary evaporation to 1 / 4 of its original volume.

[0039] b. After the concentrate has cooled, extract it with a 96:4 (v / v) 1,4-dioxane-water solution for 24 hours. Centrifuge the extracted liquid and store the supernatant at 4°C. Repeat the same extraction and centrifugation procedures twice for the precipitate obtained by centrifugation.

[0040] c. The precipitate obtained after the third extraction and centrifugation in step b was dissolved in 50% acetic acid aqueous solution and then centrifuged for 24 hours. This was repeated three times, and the supernatant obtained each time was collected. After rotary evaporation to dryness, the supernatant obtained was extracted with N,N-dimethylformamide; the extract was centrifuged and the supernatant obtained was added dropwise to ether and centrifuged. The precipitate obtained was vacuum-dried and then dissolved in 50% acetic acid aqueous solution and centrifuged. The supernatant was added dropwise to acetone and centrifuged again. The precipitate obtained was vacuum-dried to obtain LCC.

[0041] Example 2

[0042] Preparation of polyvinyl alcohol-lignin-carbohydrate complex gel (LCC-AcOH-PVA) gel.

[0043] The preparation method is exactly the same as in Example 1, except that LCC is replaced by LCC-AcOH. LCC-AcOH is prepared by the following steps:

[0044] a. Filter the eucalyptus pre-hydrolyzate and concentrate it by rotary evaporation to 1 / 4 of its original volume.

[0045] b. After the concentrate has cooled, extract it with a 96:4 (v / v) 1,4-dioxane-water solution for 24 hours. Centrifuge the extracted liquid and store the supernatant at 4°C. Repeat the same extraction and centrifugation procedures twice for the precipitate obtained by centrifugation.

[0046] c. Combine the supernatants obtained by three centrifugations in step b, evaporate to dryness, dissolve in 90% acetic acid aqueous solution, centrifuge, add the obtained supernatant dropwise to water, centrifuge again, and evaporate the obtained supernatant to dryness; repeat three times to obtain LCC-AcOH.

[0047] Examples 3 to 7 are for the determination of the physical and chemical properties of gel samples, and the measurement objects are the LCC-PVA gel obtained in Example 1, the LCC-AcOH-PVA gel obtained in Example 2, and the PVA gel (control).

[0048] The PVA gel used as a control was prepared by adding boric acid and ascorbic acid to deionized water, heating in a 40°C waterbath with stirring until fully dissolved. PVA was then added and heated in an 80°C waterbath for 40-60 minutes until completely dissolved, then allowed to stand at room temperature. The PVA gel was obtained after the solution cooled to room temperature. The amounts of boric acid and ascorbic acid used were 10% and 5% of the PVA weight, respectively.

[0049] Example 3

[0050] Morphological observation of gel: The three gel samples were freeze-dried and then cut. The cross-section surface was sprayed with gold and then observed under a scanning electron microscope (SEM) with an accelerating voltage of 5.0 to 10.0 kV.

[0051] The results are as follows Figures 1 to 6 As shown in Figure 2, compared with PVA gel, LCC-PVA and LCC-AcOH-PVA show obvious differences in overall structure, density and pore size. Figure 1 、 2 It can be seen that most of the PVA gel exists in the form of fibers, with slightly different lengths. Considering the overall number, the structure is slightly compact. The reason for the formation of this structure is that the hydrogen bonds between the boric acid molecules are partially broken, the polar groups are separated, and hydrogen bonds are generated with water molecules, which to a certain extent enhances the stability of the PVA gel. Figure 3 、 4 It can be seen that the LCC-AcOH-PVA gel curve is steep, mostly with large pore size and compact structure. Figure 5 、 6 The LCC-PVA gels exhibit a uniform porous structure, with a normal distribution curve, a small overall pore size variation, and a compact structure. This structural characteristic is consistent with the swelling performance analysis results. This indicates that the LCC-PVA and LCC-AcOH-PVA gels transform from the fibrous structure of PVA gels to a porous structure. The abundant hydroxyl groups in PVA and LCC / LCC-AcOH contribute to the strong hydrogen bonding between these hydroxyl groups, resulting in a mesh-like structure with high strength and elasticity on the surface of the gel. This morphology ensures both bonding strength and overall tightness.

[0052] Example 4

[0053] Gel Swelling Properties: The effect of swelling time on the swelling behavior of the three gels was investigated using the equilibrium swelling ratio (SRe) as an indicator. The equilibrium swelling ratio (SRe) of the gel at 25°C was calculated according to Equation 1.

[0054]

[0055] In formula (1): m 25 is the mass of the dry gel at 25°C (g), and m0 is the mass of the dry gel used in the test (g).

[0056] The results of the test are as follows Figure 7As shown, at 25°C, over the same time period, the swelling rate of the blank PVA dressing was significantly higher than that of LCC-PVA and LCC-AcOH-PVA. Over time, the swelling of the PVA, LCC-PVA, and LCC-AcOH-PVA gels gradually reached equilibrium. At equilibrium, the swelling rates of the three gels ranked as PVA > LCC-AcOH-PVA > LCC-PVA. This process manifests itself as water gradually infiltrating the gel, causing the internal network to expand and water to migrate into the spaces between pre-existing or dynamically formed hydrogel chains, leading to gel swelling. The swelling of the hydrogel results in greater segmental motion, ultimately increasing the distance between hydrogel chains. The reason for this swelling is primarily related to the degree of cross-linking: a higher degree of cross-linking results in a tighter hydrogel network and a lower swelling rate. The swelling rates of all three gel dressings exceeded 450%, demonstrating excellent swelling properties. The gel products of the present invention exhibit high swelling rates, slow degradation, excellent tissue adhesion and cytocompatibility, and can promote matrix regeneration and inhibit scar formation.

[0057] Example 5

[0058] Thermal stability testing: Thermogravimetric analysis (TGA) was used to analyze the thermal decomposition of the dry rubber. A Hitachi 7200 thermogravimetric analyzer was used. The dry rubber sample was 3-5 mg. The main measurement conditions were as follows: a heating rate of 10°C / min over a temperature range of 25-700°C. High-purity nitrogen was used as the carrier gas at a flow rate of 25 mL / min.

[0059] The results of the test are as follows Figure 8 As shown in the figure, the DTGmax of LCC-PVA, LCC-AcOH-PVA and PVA are 430℃, 406℃ and 417℃ respectively. All three gels have good thermal stability.

[0060] Example 6

[0061] Antioxidant performance determination: including the determination of DPPH free radical and hydroxyl free radical scavenging rate.

[0062] DPPH radical scavenging rate determination: Using DMSO as the solvent, gel samples of varying concentrations (0.08, 0.16, 0.24, 0.32, and 0.40 mg / mL) were prepared. 2 mL of each sample solution was placed in a 10 mL test tube. 2 mL of DPPH-DMSO solution (0.2 mmol / L) was then added. The mixture was mixed thoroughly and allowed to react in the dark for 30 minutes. The absorbance at 517 nm was then measured. The DPPH radical scavenging rate of the sample was calculated according to formula (2).

[0063]

[0064] Where AS —Absorbance of the sample solution being tested;

[0065] A X —Absorbance of the control solution (2 mL DMSO solution was used instead of 0.2 mmol / L DPPH-DMSO solution);

[0066] A O —Absorbance of blank solution (2 mL of 0.2 mmol / L DPPH-DMSO solution was used instead of sample solution).

[0067] Determination of hydroxyl radical scavenging rate: Gel samples of varying concentrations (0.34, 0.68, 1.02, 1.36, and 1.70 mg / mL) were prepared using deionized water as the solvent. One mL of each sample solution was mixed with 1 mL of a 2 mmol / L FeSO4·7H2O solution and 1 mL of a 2 mmol / L salicylic acid-ethanol solution. 1 mL of 0.3% H2O2 (v / v) was then added to the mixture. After mixing, the mixture was reacted in a 37°C water bath in the dark for 30 minutes. After completion of the reaction, the absorbance at 510 nm was measured. The hydroxyl radical scavenging rate of the sample was calculated according to formula (3).

[0068]

[0069] Where, A1 is the absorbance of the sample solution being tested;

[0070] A2—absorbance of the control solution (1 mL of deionized water was used instead of 1 mL of 0.3% H2O2 solution);

[0071] A0—Absorbance of blank solution (1 mL of deionized water is used instead of sample solution).

[0072] The results of DPPH free radical scavenging rate determination are as follows Figure 9 As shown in the figure, PVA only exhibited very low DPPH radical scavenging ability. In contrast, LCC-PVA and LCC-AcOH-PVA both showed certain DPPH radical scavenging ability, and the scavenging ability increased with the increase of component concentration. Among them, LCC-AcOH-PVA had the highest scavenging rate.

[0073] The results of hydroxyl radical scavenging rate were similar to those of DPPH radical scavenging rate ( Figure 10 As shown in the figure, compared with PVA, both LCC-PVA and LCC-AcOH-PVA have higher hydroxyl radical scavenging ability, among which LCC-PVA has the highest hydroxyl radical scavenging rate. When the concentration is 1.70 mg / mL, the corresponding scavenging rate reaches more than 20%.

[0074] The above results show that both LCC-PVA and LCC-AcOH-PVA have good antioxidant properties.

[0075] Example 7

[0076] Antibacterial performance test: The cotton swab coating method was used to determine the antibacterial effects of the three gels, LCC, and LCC-AcOH against Staphylococcus aureus and Escherichia coli.

[0077] The results are as follows Figure 11 As shown in the figure, compared with the blank, LCC, LCC-AcOH, LCC-PVA and LCC-AcOH-PVA all showed obvious antibacterial effects, and PVA showed weaker antibacterial ability because of its components containing boric acid and ascorbic acid. Figure 11 a and Figure 11 b shows the antibacterial effect on Staphylococcus aureus. As can be seen from the figure, LCC, LCC-AcOH, LCC-PVA and LCC-AcOH-PVA have significant inhibitory ability against Staphylococcus aureus, which is manifested by the formation of large inhibition zones around the samples. Among them, LCC-PVA and LCC-AcOH-PVA have the largest inhibition zone diameters, which are 17 mm and 19 mm, respectively. LCC, LCC-AcOH, LCC-PVA and LCC-AcOH-PVA also have significant inhibitory ability against Escherichia coli ( Figure 11 c, 11d). Among them, LCC-PVA and LCC-AcOH-PVA had the largest inhibition zone diameters, both 18 mm.

Claims

1. A method for preparing a polyvinyl alcohol-lignin-carbohydrate composite gel, characterized in that The steps include: 1) Adding boric acid, ascorbic acid, and N,N-methylenebisacrylamide to deionized water and heating to fully dissolve them to obtain solution A; 2) Add polyvinyl alcohol to solution A, heat until fully dissolved, and then cool the solution to room temperature to obtain solution B; 3) Dissolving the lignin-carbohydrate complex and ammonium persulfate in deionized water, mixing thoroughly until the solution is uniform, and then slowly adding the mixture to solution B. The mixture is heated to allow for a full reaction to obtain a polyvinyl alcohol-lignin-carbohydrate complex gel.

2. The method for preparing gel according to claim 1, wherein: The amounts of boric acid and ascorbic acid are 10-20% and 5-10% of the amount of polyvinyl alcohol, respectively, by mass ratio; the amounts of N,N-methylenebisacrylamide, lignin-carbohydrate complex and ammonium persulfate are all 2-5% of the amount of polyvinyl alcohol, by mass ratio.

3. The method for preparing a gel according to claim 1 or 2, wherein: The heating method in step 1) is water bath heating at a temperature of 40 to 50° C.; the heating method in step 2) is water bath heating at a temperature of 80 to 90° C., and the heating duration is 40 to 60 minutes; the heating method in step 3) is water bath heating at a temperature of 55 to 65° C., and the heating duration is 30 to 40 minutes.

4. The method for preparing gel according to claim 3, wherein: The lignin-carbohydrate complex is an acetic acid-treated lignin-carbohydrate complex (LCC-AcOH), or contains an acetic acid-treated lignin-carbohydrate complex.

5. The method for preparing gel according to claim 4, wherein: The lignin-carbohydrate complex is prepared by the following steps: a. Filter the eucalyptus pre-hydrolyzate and concentrate it by rotary evaporation to 1 / 4 of its original volume; b. After the concentrate has cooled, extract it with a 96:4 (v / v) 1,4-dioxane-water solution for 24 hours. Centrifuge the extracted liquid and store the supernatant at 4°C. Repeat the same extraction and centrifugation procedures twice for the precipitate obtained by centrifugation. c. Combine the supernatants obtained by three centrifugation in step b, evaporate to dryness, dissolve in 90% acetic acid aqueous solution, centrifuge, add the obtained supernatant dropwise to water, centrifuge again, and evaporate the obtained supernatant to dryness; After repeating this process three times, the acetic acid-treated lignin-carbohydrate complex was obtained; d. The precipitate after the third extraction and centrifugation in step b was dissolved in a 50% acetic acid aqueous solution and then centrifuged for 24 hours. This was repeated three times, and the supernatant obtained each time was collected, rotary evaporated to dryness, and then extracted with N,N-dimethylformamide; the supernatant obtained after centrifugation of the extract was added dropwise to ether and centrifuged. The obtained precipitate was vacuum-dried and then dissolved in a 50% acetic acid aqueous solution and centrifuged. The supernatant was added dropwise to acetone and centrifuged again. The obtained precipitate was vacuum-dried to obtain a lignin-carbohydrate complex.

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