Citrus pectin-polyvinyl alcohol / chitosan composite hydrogel as well as preparation method and application thereof
By developing a method for preparing a composite hydrogel of citrus pectin and polyvinyl alcohol/chitosan, the problems of insufficient mechanical properties and biocompatibility of polyvinyl alcohol hydrogels were solved. A hydrogel with uniform pore structure, good water retention and stable mechanical properties was prepared and used as a wound dressing to promote wound healing.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ANHUI UNIV OF SCI & TECH
- Filing Date
- 2026-02-03
- Publication Date
- 2026-05-01
AI Technical Summary
Existing polyvinyl alcohol hydrogels have shortcomings in terms of mechanical properties and biocompatibility, making it difficult to meet the requirements of wound dressings, especially in terms of performance in promoting wound healing and environmental regulation.
A method for preparing a composite hydrogel of citrus pectin and polyvinyl alcohol/chitosan was adopted. Through freeze-thaw cycles and ultrasonic treatment, a stable composite hydrogel was formed. Citrus pectin molecules were uniformly loaded in the chitosan/polyvinyl alcohol gel, which enhanced mechanical properties and biocompatibility.
The prepared composite hydrogel has a uniform pore structure, good water retention, stable mechanical and chemical properties, and good biocompatibility, which can promote wound healing and improve the effect of wound dressings.
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Figure CN121944210A_ABST
Abstract
Description
Citrus pectin-polyvinyl alcohol / chitosan composite hydrogel, preparation method and application Technical Field
[0001] This invention relates to the field of hydrogel technology, and more particularly to citrus pectin-polyvinyl alcohol / chitosan composite hydrogels, their preparation methods, and applications. Background Technology
[0002] Disease or external factors can damage the skin, leading to wound infection, which can impact a patient's health and financial well-being. Wound infection and inflammation typically occur after surgical intervention, traumatic wounds, abrasions, or burns, and if left untreated, can result in life-threatening sepsis, multiple organ failure, and ultimately, death.
[0003] Hydrogels, as promising medical materials, are three-dimensional network structures formed by the intertwining of linear polymer chains, and are now widely used in biomedical research related to skin conditions. Hydrogels not only possess excellent biocompatibility, mechanical properties, and porous structure, but also have the ability to maintain a moist wound environment and promote gas exchange.
[0004] Polyvinyl alcohol (PVA) contains numerous hydroxyl groups in its molecules, enabling it to form hydrogen bonds with water and exhibiting excellent water solubility. Furthermore, the relatively small space occupied by the side hydroxyl groups gives PVA excellent breathability. PVA is a biodegradable polymer with virtually no toxicity, making it environmentally friendly and widely used as a major component of wound dressing hydrogels. Chitosan, derived from chitin, is a polycationic polymer. In blood, chitosan can bind to platelets through electrostatic interactions, promoting platelet adhesion, accelerating erythrocyte coagulation, and promoting blood clot formation, thus possessing excellent hemostatic properties and the ability to promote wound healing. In addition, chitosan has many properties beneficial to wound healing, such as biocompatibility, biodegradability, non-toxicity, adsorption, and anti-infective properties. Chitosan has good film-forming properties, making it one of the ideal materials for preparing functional hydrogels. Polyvinyl alcohol (PVA) is highly hydrophilic, easily swelling and even dissolving in water. It also exhibits weak mechanical properties and poor adhesion to biological tissues. Using PVA alone presents certain problems, limiting its applications. Therefore, to optimize its performance, it is often modified by adding other materials. Chitosan is an excellent blending material. Since PVA is rich in hydroxyl groups, blending it with the amino groups of chitosan to prepare a hydrogel weakens the hydrogen bonds in the chitosan molecular chain, thereby improving its water solubility and antibacterial activity. Simultaneously, it optimizes the mechanical and swelling properties of PVA, thus mitigating the performance shortcomings of both materials. Furthermore, PVA-chitosan composite hydrogels cannot meet the requirements of wound dressings as environmental regulators to accelerate wound healing. To address this issue, a composite hydrogel with better mechanical properties has been developed to further enhance wound healing capabilities, demonstrating significant social value. Summary of the Invention
[0005] Based on the technical problems existing in the background technology, this invention proposes a citrus pectin-polyvinyl alcohol / chitosan composite hydrogel, its preparation method and application. The prepared citrus pectin-polyvinyl alcohol / chitosan composite hydrogel has a uniform pore structure, good water retention, more stable mechanical and chemical properties, and good biocompatibility.
[0006] This invention proposes a method for preparing a citrus pectin-polyvinyl alcohol / chitosan composite hydrogel, comprising the following steps: S1: Mixing a polyvinyl alcohol solution and a chitosan solution evenly, and subjecting the mixture to a freeze-thaw cycle to obtain a polyvinyl alcohol / chitosan mixed gel; S2: Immersing the polyvinyl alcohol / chitosan mixed gel in a citrus pectin solution, subjecting it to ultrasonic treatment, and then filtering and drying to obtain the citrus pectin-polyvinyl alcohol / chitosan composite hydrogel.
[0007] Preferably, the mass ratio of polyvinyl alcohol solution to chitosan in S1 is 1:0.03-0.05.
[0008] Preferably, the mixing temperature in S1 is 36-38℃ and the time is 1.5-2.5h.
[0009] Preferably, the conditions for the freeze-thaw cycle in S1 are: freezing temperature -20°C, held for 17-19 hours, thawing temperature 20-30°C, and time 5-7 hours.
[0010] Preferably, the number of freeze-thaw cycles is 4-8.
[0011] Preferably, the concentration of the citrus pectin solution in S2 is 5-15 mg / ml; the mass ratio of citrus pectin to chitosan is 1:0.5-1.5.
[0012] Preferably, the ultrasonic treatment conditions in S2 are a frequency of 30-50 Hz and a time of 30-90 min.
[0013] Preferably, the drying conditions in S2 are a temperature of 36-38°C and a time of 1.5-2.5 hours.
[0014] The present invention proposes a citrus pectin-polyvinyl alcohol / chitosan composite hydrogel, which is prepared by the above-mentioned method.
[0015] The present invention proposes the application of the above-mentioned citrus pectin-polyvinyl alcohol / chitosan composite hydrogel in medical dressings.
[0016] The beneficial technical effects of this invention are as follows: Polyvinyl alcohol and chitosan molecules form a stable hydrogel through physical hydrogen bond entanglement, and citrus pectin molecules are uniformly loaded within the chitosan / polyvinyl alcohol gel. This results in a citrus pectin-polyvinyl alcohol / chitosan composite hydrogel with a uniform pore structure, good water retention, more stable mechanical and chemical properties, and good biocompatibility. After overall modification of the composite gel by ultrasound, the citrus pectin molecules are more densely and uniformly filled within the polyvinyl alcohol / chitosan mixed gel. This gives the modified citrus pectin-polyvinyl alcohol / chitosan composite gel a denser network pores, superior water retention, better mechanical properties, and a more stable gel system. Attached Figure Description
[0017] Figure 1 shows the infrared spectrum of the composite hydrogel proposed in this invention; where (a) is the composite hydrogel of Comparative Examples 1 and 2, and (b) is the composite hydrogel of Example 1 and Comparative Example 3. Figure 2 shows the scanning electron microscope image of the composite hydrogel proposed in this invention; where (a) is the composite hydrogel of Comparative Example 2, (b) is the composite hydrogel of Comparative Example 1, (c) is the composite hydrogel of Comparative Example 3, and (d) is the composite hydrogel of Example 1. Figure 3 shows the adhesion properties of the composite hydrogels of Example 1 and Comparative Examples 1-3 proposed in this invention. Figure 4 shows the elasticity of the composite hydrogels of Example 1 and Comparative Examples 1-3 proposed in this invention. Figure 5 shows the water content of the composite hydrogels of Example 1 and Comparative Examples 1-3 proposed in this invention. Figure 6 shows the tensile properties of the composite hydrogel proposed in this invention; where (a) is the composite hydrogel of Comparative Example 2, (b) is the composite hydrogel of Comparative Example 3, and (c) is the composite hydrogel of Comparative Example 1. (d) is the composite hydrogel of Example 1; Figure 7 is a macroscopic self-healing diagram of the composite hydrogel proposed in this invention; wherein (a) is the hydrogel of Example 1 stained with hematoxylin dye and Ponceau S dye respectively, and the mixed hydrogel after the two stainings; (b) is the hydrogel of Comparative Examples 2 and 3 stained with hematoxylin dye and Ponceau S dye respectively, and the hydrogel after the two stainings are mixed; (c) is the self-healing tensile effect of the composite hydrogel of Comparative Example 1 and Example 1; Figure 8 is a macroscopic adhesion diagram of the composite hydrogel proposed in this invention; (a) and (c) are the composite hydrogel of Comparative Example 2, (b) and (d) are the composite hydrogel of Comparative Example 3, (e), (g), (i) and (k) are the composite hydrogel of Comparative Example 1, (f), (h), (j) and (l) are the composite hydrogel of Example 1; Figure 9 is an animal experiment on the composite hydrogel of Example 1 proposed in this invention promoting skin wound healing. Detailed Implementation
[0018] The present invention will be further explained below with reference to specific embodiments.
[0019] Unless otherwise specified, all raw materials used in the embodiments of this invention can be obtained commercially. Chitosan (C804726) was purchased from Maclean's Biochemical Technology Co., Ltd.; polyvinyl alcohol (P139540) was purchased from Aladdin Biochemical Technology Co., Ltd.; citrus pectin (S11083) was purchased from Shanghai Yuanye Biotechnology Co., Ltd.; acetic acid solution (A885187) was purchased from Maclean's Biochemical Technology Co., Ltd.; and apple pectin (S11082) was purchased from Shanghai Yuanye Biotechnology Co., Ltd. Examples
[0020] Weigh 4.5g of polyvinyl alcohol and dissolve it in 30ml of ultrapure water. The ultrapure water needs to be preheated to 80℃. Stir with a glass rod until completely dissolved. Weigh 0.2g of chitosan and dissolve it in 10ml of 1% acetic acid solution. Mix the chitosan solution and polyvinyl alcohol solution evenly and stir with a magnetic stirrer for 2 hours. Then, place the mixture in a 37℃ water bath for 2 hours. After the water bath, place the polyvinyl alcohol / chitosan mixed gel in a -20℃ freezer and perform a freeze-thaw cycle 5 times. The freezing time is 18 hours, and the thawing temperature is room temperature for 6 hours.
[0021] Weigh 0.2g of citrus pectin and dissolve it in 20ml of ultrapure water (the ultrapure water needs to be preheated to 60℃). Then, immerse the polyvinyl alcohol / chitosan mixed gel in the citrus pectin solution and sonicate it at 40Hz for 1 hour. Discard the excess citrus pectin solution and place it in a 37℃ electric heating drying oven for 2 hours. After drying, allow the composite hydrogel to cool to room temperature to obtain the citrus pectin-polyvinyl alcohol / chitosan composite hydrogel. Example
[0022] Weigh 5g of polyvinyl alcohol and dissolve it in 30ml of ultrapure water. The ultrapure water needs to be preheated to 85℃. Stir with a glass rod until completely dissolved. Weigh 0.25g of chitosan and dissolve it in 10ml of 1% acetic acid solution. Mix the chitosan solution and polyvinyl alcohol solution evenly and stir with a magnetic stirrer for 2.5h. Then, place the mixture in a 38℃ water bath for 2.5h. After the water bath, place the polyvinyl alcohol / chitosan mixed gel in a -20℃ freezer and perform a freeze-thaw cycle 5 times. The freezing time is 19h, and the thawing temperature is room temperature with a thawing time of 7h.
[0023] 0.25g of citrus pectin was dissolved in 20ml of ultrapure water, which was preheated to 65℃. The polyvinyl alcohol / chitosan mixed gel was then immersed in the citrus pectin solution and sonicated at 50Hz for 1.5h. Excess citrus pectin solution was discarded, and the gel was placed in a 38℃ electric drying oven for 2.5h. After drying, the composite hydrogel was cooled to room temperature to obtain the citrus pectin-polyvinyl alcohol / chitosan composite hydrogel. Example
[0024] Weigh 4g of polyvinyl alcohol and dissolve it in 30ml of ultrapure water. The ultrapure water needs to be preheated to 75℃. Stir with a glass rod until completely dissolved. Weigh 0.15g of chitosan and dissolve it in 10ml of 1% acetic acid solution. Mix the chitosan solution and polyvinyl alcohol solution evenly and stir with a magnetic stirrer for 1.5h. Then, place the mixture in a 36℃ water bath for 1.5h. After the water bath, place the polyvinyl alcohol / chitosan mixed gel in a -20℃ freezer and perform a freeze-thaw cycle 5 times. The freezing time is 17h, and the thawing temperature is room temperature for 5h.
[0025] Weigh 0.15g of citrus pectin and dissolve it in 20ml of ultrapure water, which should be preheated to 55℃. Then, immerse the polyvinyl alcohol / chitosan mixed gel in the citrus pectin solution and sonicate it at 30Hz for 0.5h. Discard the excess citrus pectin solution and place it in a 36℃ electric hot air drying oven for 1.5h. After drying, allow the composite hydrogel to cool to room temperature to obtain the citrus pectin-polyvinyl alcohol / chitosan composite hydrogel.
[0026] Weigh 4.5g of polyvinyl alcohol and dissolve it in 30ml of ultrapure water. The ultrapure water needs to be preheated to 80℃. Stir with a glass rod until completely dissolved. Weigh 0.2g of chitosan and dissolve it in 10ml of 1% acetic acid solution. Mix the chitosan solution and polyvinyl alcohol solution evenly and stir with a magnetic stirrer for 2 hours. Then, place the mixture in a 37℃ water bath for 2 hours. After the water bath, place the polyvinyl alcohol / chitosan mixed gel in a -20℃ freezer and perform a freeze-thaw cycle 5 times. The freezing time is 18 hours, and the thawing temperature is room temperature for 6 hours.
[0027] Weigh 0.2g of citrus pectin and dissolve it in 20ml of ultrapure water, which needs to be preheated to 60℃. Then, soak the polyvinyl alcohol / chitosan mixed gel in the citrus pectin solution for 1 hour. After soaking, discard the excess citrus pectin solution and place it in a 37℃ electric hot air drying oven for 2 hours. After drying, wait for the composite hydrogel to cool to room temperature to obtain the citrus pectin-polyvinyl alcohol / chitosan composite hydrogel.
[0028] Weigh 4.5g of polyvinyl alcohol and dissolve it in 30ml of ultrapure water. The ultrapure water needs to be preheated to 80℃. Stir with a glass rod until completely dissolved. Weigh 0.2g of chitosan and dissolve it in 10ml of 1% acetic acid solution. Mix the chitosan solution and polyvinyl alcohol solution evenly and stir with a magnetic stirrer for 2 hours. Then, place the mixture in a 37℃ water bath for 2 hours. After the water bath, place the polyvinyl alcohol / chitosan mixed gel in a -20℃ freezer and perform a freeze-thaw cycle 5 times. The freezing time is 18 hours, and the thawing temperature is room temperature for 6 hours.
[0029] Weigh 0.2g of apple pectin and dissolve it in 20ml of ultrapure water, which needs to be preheated to 60℃. Then, immerse the polyvinyl alcohol / chitosan mixed gel in the apple pectin solution for 1 hour. After immersion, discard the excess apple pectin solution and place it in a 37℃ electric heating drying oven for 2 hours. After drying, wait for the composite hydrogel to cool to room temperature to obtain the apple pectin-polyvinyl alcohol / chitosan composite hydrogel.
[0030] Weigh 4.5g of polyvinyl alcohol and dissolve it in 30ml of ultrapure water. The ultrapure water needs to be preheated to 80℃. Stir with a glass rod until completely dissolved. Weigh 0.2g of chitosan and dissolve it in 10ml of 1% acetic acid solution. Mix the chitosan solution and polyvinyl alcohol solution evenly and stir with a magnetic stirrer for 2 hours. Then, place the mixture in a 37℃ water bath for 2 hours. After the water bath, place the polyvinyl alcohol / chitosan mixed gel in a -20℃ freezer and perform a freeze-thaw cycle 5 times. The freezing time is 18 hours, and the thawing temperature is room temperature for 6 hours.
[0031] Weigh 0.2g of apple pectin and dissolve it in 20ml of ultrapure water, which needs to be preheated to 60℃. Then, immerse the polyvinyl alcohol / chitosan mixed gel in the apple pectin solution and sonicate it at 40Hz for 1 hour. Discard the excess apple pectin solution and place it in a 37℃ electric heating drying oven for 2 hours. After drying, wait for the composite hydrogel to cool to room temperature to obtain the apple pectin-polyvinyl alcohol / chitosan composite hydrogel.
[0032] Figure 1 shows the Fourier transform infrared spectrum of the composite hydrogel; the effects of adding apple pectin and citrus pectin on the structural changes and intermolecular interactions of the polyvinyl alcohol / chitosan mixed gel can be studied from a molecular structure perspective. As shown in part (a) of Figure 1, the apple pectin-polyvinyl alcohol / chitosan composite hydrogel exhibits a high molecular weight distribution at 3310 cm⁻¹. -1 The citrus pectin-polyvinyl alcohol / chitosan mixed gel exhibits a broad and strong absorption peak associated with the stretching vibration of -OH, while the -OH absorption peak of the citrus pectin-polyvinyl alcohol / chitosan mixed gel appears at 3307 cm⁻¹. -1 The characteristic peak of -OH stretching increases from 3310 cm⁻¹ -1 Offset to 3307cm -1 Furthermore, the -OH absorption peak of the polyvinyl alcohol / chitosan mixed gel appears at 3338 cm⁻¹. -1 The characteristic peak of -OH stretching increases from 3338 cm⁻¹ -1 Offset to 3307cm -1 and 3310cm -1 This indicates that apple pectin and citrus pectin are bound to polyvinyl alcohol via hydrogen bonds. Furthermore, the -COOCH3 absorption peaks of both composite hydrogels appear at 1731 cm⁻¹. -1 At this location, compared to the polyvinyl alcohol / chitosan hybrid gel, the stretching vibration of -COOCH3 increased from 1738 cm⁻¹. -1 Offset to 1731cm -1 This indicates that apple pectin molecules and citrus pectin molecules were successfully introduced into the polyvinyl alcohol / chitosan mixed gel.
[0033] As shown in part (b) of Figure 1, this figure displays the infrared spectra of the apple and citrus composite hydrogels after ultrasonic modification. After ultrasonic modification, the apple pectin-polyvinyl alcohol / chitosan composite hydrogel, compared to the untreated apple pectin-polyvinyl alcohol / chitosan composite hydrogel, shows almost no shift in the C=O stretching vibration peak, indicating that the carboxyl groups (-COOH) of the apple pectin molecules do not interact ionicly with the amino groups (-NH2) in chitosan. The ultrasonically modified apple pectin-polyvinyl alcohol / chitosan composite hydrogel exhibits a peak at 3321 cm⁻¹. -1 The modified apple pectin-polyvinyl alcohol / chitosan composite gel exhibits an absorption peak at 3310 cm⁻¹, which is related to the stretching vibration of -OH. -1 The characteristic peak of -OH stretching increases from 3310 cm⁻¹ -1 Offset to 3321cm -1 This indicates that the hydrogen bonding between apple molecules and polyvinyl alcohol molecules weakens after ultrasonic treatment. After ultrasonic modification of the citrus pectin-polyvinyl alcohol / chitosan composite hydrogel, the peak of the C=O stretching vibration at 1654 cm⁻¹ is observed in the unmodified composite hydrogel. -1 The offset was 1610cm -1 This indicates that the carboxyl groups (-COOH) of citrus pectin molecules and the amino groups (-NH2) of chitosan undergo strong ionic interactions and hydrogen bonding, further proving that citrus pectin molecules have been successfully incorporated into the polyvinyl alcohol / chitosan hybrid gel. The characteristic peak of -OH stretching in the apple and citrus groups after ultrasonic treatment was 3321 cm⁻¹. -1 and 3332cm -1 This indicates that the citrus group formed more hydrogen bonds after ultrasonic treatment. Secondly, the peak value of the C=O stretching vibration in the ultrasonically treated apple and citrus groups was 1656 cm⁻¹. -1 and 1610cm -1 This indicates that citrus pectin and chitosan in the citrus group are linked together through ionic interactions and hydrogen bonds.
[0034] Figure 2 shows the scanning electron microscope (SEM) images of the composite hydrogels. As can be seen from the figures, the pores of the apple pectin-polyvinyl alcohol / chitosan composite gel are denser and more uniform compared to the citrus pectin-polyvinyl alcohol / chitosan composite gel, which is conducive to the formation of a more stable three-dimensional network system. After ultrasonic treatment, the pores and density of the apple pectin-polyvinyl alcohol / chitosan composite gel are not as good as the unmodified state. Under SEM, the pores of the ultrasonically modified apple pectin-polyvinyl alcohol / chitosan composite gel network are large and uneven. In contrast, the ultrasonically modified citrus pectin-polyvinyl alcohol / chitosan composite hydrogel exhibits a denser and more uniform network pores than the apple-modified group, due to the further tight binding of citrus pectin molecules with polyvinyl alcohol and chitosan molecules.
[0035] Figure 3 shows the adhesion properties of the composite hydrogels. As can be seen from the figure, the adhesion of the apple group is lower than that of the citrus group, and the citrus pectin-polyvinyl alcohol / chitosan composite hydrogel after ultrasonic modification exhibits the best adhesion. This is attributed to the fact that citrus pectin molecules not only regulate the hydrogen bond crosslinking density formed by polyvinyl alcohol and chitosan, but also promote the entanglement between pectin and polyvinyl alcohol molecules through ionic interactions, thereby enhancing the gel's adhesive properties. Furthermore, the adhesion of the composite hydrogel in the citrus group increased after ultrasonic modification. This is attributed to the further regulation of the hydrogen bond crosslinking network density formed by pectin, polyvinyl alcohol, and chitosan through ultrasound, and the promotion of entanglement between pectin and chitosan molecules through ionic interactions, thus enhancing the gel's adhesive properties. The overall adhesion of the apple group is lower than that of the citrus group, which may be attributed to the weaker entanglement and binding degree between apple pectin and the polyvinyl alcohol / chitosan mixed gel compared to citrus pectin. Because the entanglement strength between apple pectin and polyvinyl alcohol (PVA) molecules is lower than that between citrus pectin and PVA molecules, the adhesiveness of the apple pectin-PVA / chitosan composite gel is lower than that of the citrus pectin-PVA / chitosan composite gel. Secondly, the adhesiveness of the apple group after ultrasonic modification decreases. This is attributed to the reduction in the density of the hydrogen bond crosslinking network formed by apple pectin, PVA, and chitosan through ultrasound, thus decreasing the gel's adhesive properties.
[0036] Figure 4 shows the elasticity of the composite hydrogels. As can be seen from the figure, the apple group exhibits lower elasticity than the citrus group, and the ultrasonically modified citrus pectin-polyvinyl alcohol / chitosan composite hydrogel demonstrates the best elasticity. This is attributed to the fact that, compared to the unmodified group, the citrus pectin molecules in the ultrasonically treated citrus pectin-polyvinyl alcohol / chitosan composite hydrogel further bind with chitosan molecules, thereby reducing the crystallinity of polyvinyl alcohol / chitosan and resulting in a more uniform distribution of elastic modulus. Furthermore, the further introduction of citrus pectin molecules provides more additional cross-linking points, making the network structure of the ultrasonically modified composite hydrogel more compact and stable, thus further enhancing its elasticity. The elasticity of the ultrasonically treated apple pectin-polyvinyl alcohol / chitosan composite hydrogel is lower than that of the unmodified group. This is attributed to the weakened binding between apple pectin molecules and polyvinyl alcohol in the composite gel after ultrasonic treatment, making the network structure of the composite hydrogel loose and unstable, thereby increasing the crystallinity of polyvinyl alcohol / chitosan and resulting in an uneven distribution of elastic modulus, thus reducing the elastic properties of the composite gel. The lower overall elasticity of the apple group compared to the citrus group may be attributed to the lower binding strength of apple pectin with the polyvinyl alcohol / chitosan mixed gel and the lower molecular introduction amount compared to citrus pectin. This results in the less uniform elastic modulus of the composite hydrogel in the apple group compared to the citrus group, ultimately leading to a less stable network in the composite hydrogel of the apple group compared to the citrus group, thus reducing the elastic properties of the composite hydrogel in the apple group.
[0037] Figure 5 shows the water content of the composite hydrogels after 12h, 24h, and 36h. The figure shows that the ultrasonically modified citrus pectin-polyvinyl alcohol / chitosan composite hydrogel has the highest water content and the best water retention effect compared to other groups. This is attributed to the further entanglement of citrus pectin and chitosan molecules after ultrasonic treatment, allowing the composite gel network to capture more water molecules, and the increased density of the gel network through van der Waals forces, thus further improving the water-holding capacity of the composite hydrogel. In the apple group, the water content of the composite hydrogel after ultrasonic treatment decreased compared to the unmodified group. This is because the apple pectin-polyvinyl alcohol / chitosan composite gel network becomes looser after ultrasonic treatment, resulting in fewer water molecules captured by the gel network and thus reducing the water-holding capacity of the composite hydrogel. Because the network structure of the composite hydrogel in the apple group is less dense than that in the citrus group, the overall water content of the composite hydrogel in the apple group is lower than that in the citrus group.
[0038] Figure 6 shows the tensile properties of the composite hydrogels. As shown, the citrus group exhibits better tensile performance than the apple group, with the ultrasonically modified citrus pectin-polyvinyl alcohol / chitosan composite hydrogel showing the best tensile effect. This indicates that ultrasonic treatment further fills and distributes pectin molecules, improving the mechanical properties of the composite hydrogel. The superior performance of the citrus group compared to the apple group may be due to the greater entanglement of citrus pectin molecules with the polyvinyl alcohol / chitosan mixed gel compared to apple pectin, and the higher amount of citrus pectin introduced. In the apple group, the tensile properties of the ultrasonically modified apple pectin-polyvinyl alcohol / chitosan composite hydrogel are lower than those of the unmodified composite hydrogel, which is attributed to the reduced elasticity of the modified composite hydrogel.
[0039] Figure 7 shows the macroscopic self-healing properties of the composite hydrogels. Figure a shows the composite hydrogels stained with Ponceau S and hematoxylin respectively, resulting in red and blue composite gels. The red and blue composite gels were then placed together, and after a period of time, the interpenetration between them was observed to determine whether the composite hydrogels possess self-healing properties. Figure b shows the staining patterns of the apple pectin-polyvinyl alcohol / chitosan composite hydrogel and the ultrasonically modified apple pectin-polyvinyl alcohol / chitosan composite hydrogel, respectively. After a period of time, no interpenetration between the red and blue components was observed in the apple group, indicating that the composite hydrogel in the apple group lacked self-healing properties. Figure c shows the tensile diagram of the self-healing properties of the citrus pectin-polyvinyl alcohol / chitosan composite hydrogel (left) and the tensile diagram of the self-healing properties of the ultrasonically treated citrus pectin-polyvinyl alcohol / chitosan composite hydrogel (right). It can be seen that the blue and red composite hydrogels in the citrus group are tightly bonded together. This self-healing property is attributed to the unique amorphous structure of the composite gel, which makes it easy for polymer chains to diffuse and form hydrogen bonds or coordination interactions on new surfaces.
[0040] Figure 8 shows the macroscopic adhesion properties of the composite hydrogels. In the adhesion experiment, the apple group could only adhere to paper and tin foil, as shown in Figures abcd, where ac represents unmodified hydrogels and BD represents ultrasonically modified hydrogels. In contrast, the citrus group could adhere not only to paper and tin foil, as shown in Figures efgh, where eg represents unmodified hydrogels and fh represents ultrasonically modified hydrogels, but also to wood and plastic, as shown in Figures ijkl, where ik represents unmodified hydrogels and jl represents ultrasonically modified hydrogels. The results indicate that the citrus group exhibited superior adhesion compared to the apple group. This is because citrus pectin molecules not only modulate the hydrogen bond crosslinking density between polyvinyl alcohol and chitosan, but also promote the entanglement between pectin and polyvinyl alcohol molecules through ionic interactions, thereby enhancing the gel's adhesion properties. Furthermore, the adhesiveness of the composite hydrogels from both the apple and citrus groups increased after ultrasonic modification. This is attributed to the further modulation of the hydrogen bond crosslinking network density formed by pectin, polyvinyl alcohol, and chitosan through ultrasound, and the promotion of entanglement between pectin and chitosan molecules through ionic interactions, thus enhancing the gel's adhesion properties.
[0041] The performance of the composite hydrogel prepared in Example 1 in promoting skin wound healing was tested. As shown in Figure 9, after anesthetizing mice with isoflurane, a square hairless area of about 4 cm was cut out on the back of each mouse, and then disinfected with alcohol. After disinfection, a full-thickness wound of about 10 mm was cut on each mouse with ophthalmic scissors. The wound was then photographed on days 1, 3, 6, and 9 after modeling to observe the wound color and record the wound shape.
[0042] Wound healing results showed that, in the control group without any wound dressing, the wound healing was inferior to that of the group treated with ultrasound-modified citrus pectin-polyvinyl alcohol / chitosan composite hydrogel. This demonstrates that ultrasound-treated citrus pectin-polyvinyl alcohol / chitosan composite hydrogel can effectively promote skin wound healing.
[0043] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application. The scope of this application is defined by the appended claims and their equivalents, all of which should be included within the protection scope of this application.
Claims
1. A method for preparing a citrus pectin-polyvinyl alcohol / chitosan composite hydrogel, characterized in that, The method steps are as follows: S1: Mix the polyvinyl alcohol solution and chitosan solution evenly and perform a freeze-thaw cycle to obtain a polyvinyl alcohol / chitosan mixed gel; S2: Immerse the polyvinyl alcohol / chitosan mixed gel in a citrus pectin solution and perform ultrasonic treatment. After filtration and drying, a citrus pectin-polyvinyl alcohol / chitosan composite hydrogel is obtained.
2. The method for preparing the citrus pectin-polyvinyl alcohol / chitosan composite hydrogel according to claim 1, characterized in that, The mass ratio of polyvinyl alcohol solution to chitosan in S1 is 1:0.03-0.
05.
3. The method for preparing the citrus pectin-polyvinyl alcohol / chitosan composite hydrogel according to claim 1, characterized in that, The mixing temperature in S1 is 36-38℃, and the time is 1.5-2.5h.
4. The method for preparing the citrus pectin-polyvinyl alcohol / chitosan composite hydrogel according to claim 1, characterized in that, The conditions for the freeze-thaw cycle in S1 are: freezing temperature -20℃, held for 17-19 hours, thawing temperature 20-30℃, and time 5-7 hours.
5. The method for preparing the citrus pectin-polyvinyl alcohol / chitosan composite hydrogel according to claim 4, characterized in that, The freeze-thaw cycle is repeated 4-8 times.
6. The method for preparing the citrus pectin-polyvinyl alcohol / chitosan composite hydrogel according to claim 1, characterized in that, The concentration of the citrus pectin solution in S2 is 5-15 mg / ml; the mass ratio of citrus pectin to chitosan is 1:0.5-1.
5.
7. The method for preparing the citrus pectin-polyvinyl alcohol / chitosan composite hydrogel according to claim 1, characterized in that, The conditions for ultrasonic treatment in S2 are a frequency of 30-50 Hz and a time of 30-90 min.
8. The method for preparing the citrus pectin-polyvinyl alcohol / chitosan composite hydrogel according to claim 1, characterized in that, The drying conditions in S2 are a temperature of 36-38℃ and a time of 1.5-2.5h.
9. A citrus pectin-polyvinyl alcohol / chitosan composite hydrogel, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.
10. The application of the citrus pectin-polyvinyl alcohol / chitosan composite hydrogel as described in claim 9 in medical dressings.