CN111410753A

CN111410753A - Novel chitosan hydrogel and preparation method and application thereof

Info

Publication number: CN111410753A
Application number: CN202010231935.6A
Authority: CN
Inventors: 阮长晴; 康晓鸥; 邓丽莉; 易兰花; 曾凯芳
Original assignee: Southwest University
Current assignee: Southwest University
Priority date: 2020-03-27
Filing date: 2020-03-27
Publication date: 2020-07-14

Abstract

The invention discloses a novel chitosan hydrogel and a preparation method and application thereof, belonging to the technical field of macromolecules. The preparation method comprises the following steps: mixing the cellulose suspension with periodate, stirring for reaction under the condition of keeping out of the sun, centrifuging, and washing a precipitate to obtain the cellulose-containing water-soluble chitosan/chitosan composite material; under the condition of water bath, heating and stirring the precipitate until the precipitate is completely dissolved to obtain a transparent solution A; dissolving chitosan in acetic acid water solution, and stirring until the chitosan is completely dissolved to obtain transparent solution B; dropwise adding the transparent solution A into the transparent solution B until the gelation reaction is finished, and then washing with water to obtain the product. The preparation method of the novel chitosan hydrogel disclosed by the invention is simple in process and easy to operate, other reagents are not required to be added in the preparation process, the prepared novel chitosan hydrogel is environment-friendly and biodegradable, has antibacterial properties to escherichia coli and staphylococcus aureus, and has wide practical value in the aspects of biomedicine, food, chemical industry and the like.

Description

Novel chitosan hydrogel and preparation method and application thereof

Technical Field

The invention relates to the technical field of macromolecules, and particularly relates to a novel chitosan hydrogel and a preparation method and application thereof.

Background

Hydrogels are a class of polymeric materials having a three-dimensional network structure that can absorb a large amount of water without dissolving, and can maintain a certain shape and a certain strength. Because of the super-absorbent and flexible structure, the hydrogel has wide application prospect in the aspects of biomedicine, food, chemical industry and the like. Natural hydrogels are attracting more attention due to their green environmental protection, biodegradability, low cost and abundant resources. Chitosan (Chitosan, CS) is the only natural cationic polymer and is widely used due to its unique function. It is second only to cellulose, the second largest natural polysaccharide, abundant amino and hydroxyl groups available as cross-linking functional groups, react with cross-linking agents to undergo in situ chemical cross-linking, on the other hand, the presence of amino groups makes it soluble in acid solutions. In addition, it has various physiological functions of biodegradability, biocompatibility, nontoxicity, bacteriostasis and the like. These features make CS an ideal candidate for a new biomaterial, hydrogel.

Various chemical and physical crosslinking methods have been reported to produce CS-based hydrogels, but non-covalently bonded gel systems based on physical methods are generally unstable. On the one hand, certain chemical modifications may involve complicated synthetic processes and, on the other hand, although chemical crosslinkers have advantages in terms of improved mechanical properties, they may lead to a reduction in the biocompatibility of the material even after thorough purification, due to their potential toxicity. Furthermore, CS crosslinked hydrogels have poor mechanical properties and poor chemical stability, which severely limits the use of CS as a cheap and readily available material.

Disclosure of Invention

In view of the above, the present invention aims to provide a novel, green and antibacterial chitosan hydrogel, and a preparation method and an application thereof.

In order to achieve the above purpose, the inventor of the present invention has conducted long-term research and extensive practice to provide the technical solution of the present invention, and the specific implementation process is as follows;

1. a preparation method of novel chitosan hydrogel comprises the following steps:

1) mixing the cellulose suspension with periodate, stirring and reacting for 1-5 days under the condition of keeping out of the sun, centrifuging, and washing a precipitate to obtain dialdehyde cellulose (DAC);

2) heating and stirring dialdehyde cellulose to be completely dissolved in a water bath condition at 95-100 ℃ to obtain a transparent solution A;

3) dissolving Chitosan (CS) in an acetic acid aqueous solution, and stirring until the Chitosan (CS) is completely dissolved to obtain a transparent solution B;

4) dropwise adding the transparent solution A into the transparent solution B until the gelation reaction is finished, and then washing with water to obtain the novel chitosan hydrogel.

Wherein, in the step 1), under the condition of keeping out of the sun, the cellulose is oxidized by sodium periodate, the pyran ring of the cellulose is opened in the oxidation process, and the hydroxyl at the C2 and C3 positions is oxidized into aldehyde groups, so that the dialdehyde cellulose is obtained. Stirring and reacting for 1-5 days to obtain dialdehyde cellulose with the oxidation degree of 85-100%. In step 1), the precipitate is washed repeatedly with deionized water to purify the dialdehyde-based cellulose. In the step 2), the time for heating and stirring until complete dissolution is 0.5-2 h. In step 4), washing with water is preferably repeated with deionized water to purify the product.

Preferably, in the step 1), the mass percentage of the cellulose in the cellulose suspension is 0.5-5%.

Preferably, in the step 1), the periodate is sodium periodate, and the dosage of the periodate is 1-5 times of the molar quantity of the cellulose.

Preferably, in the step 3), the mass percentage of acetic acid in the acetic acid aqueous solution is 1-2%.

Preferably, in the step 3), the mass percentage of the chitosan in the transparent solution B is 0.5-2%.

Preferably, in the step 4), the concentration of the transparent solution A in the novel chitosan hydrogel is 2.5-10%.

Preferably, in the step 4), the concentration of the transparent solution a in the novel chitosan hydrogel is 10%.

2. The novel chitosan hydrogel prepared by the preparation method.

3. The novel chitosan hydrogel prepared by the preparation method is applied as a wound dressing in biomedicine.

The invention has the beneficial effects that:

1) according to the preparation method of the novel chitosan hydrogel, chitosan and dialdehyde cellulose are used as raw materials, abundant amino and hydroxyl in the chitosan are used as cross-linking functional groups, the chitosan and the dialdehyde cellulose cross-linking agent are subjected to in-situ chemical cross-linking, and meanwhile, the abundant amino in the chitosan and aldehyde groups in the dialdehyde cellulose form dynamic covalent bonds, so that the prepared novel hydrogel has strong mechanical properties and chemical stability;

2) the preparation method of the novel chitosan hydrogel disclosed by the invention is simple in process and easy to operate, and in the preparation process of the hydrogel, other reagents are not required to be added, and the raw materials are all natural high polymer materials which are green, low in price and rich in sources, so that the prepared novel chitosan hydrogel has the advantages of green environmental protection, biodegradability, good antibacterial property and biocompatibility;

3) the novel chitosan hydrogel disclosed by the invention has antibacterial property on escherichia coli and staphylococcus aureus, so that the novel chitosan hydrogel has wide practical value in the aspects of biomedicine, food, chemical industry and the like.

Drawings

FIG. 1 is a comparative image of the appearance of the novel chitosan hydrogel of the present invention;

FIG. 2 is an infrared spectrum of the novel chitosan hydrogel of the present invention;

FIG. 3 is a thermogravimetric plot of the novel chitosan hydrogel of the present invention;

FIG. 4 is a graph of the water content of the novel chitosan hydrogel of the present invention;

FIG. 5 is a graph showing the swelling of the novel chitosan hydrogel of the present invention at different pH values;

FIG. 6 is a graph of water retention at different temperatures for the novel chitosan hydrogel of the present invention;

FIG. 7 is a graph of gel strength of the novel chitosan hydrogel of the present invention;

FIG. 8 is a graph of storage modulus (G ') and loss modulus (G') of the novel chitosan hydrogel of the present invention;

FIG. 9 is a bacteriostatic diagram of the novel chitosan hydrogel of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention are clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the 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) mixing the cellulose suspension with the content of 1% with sodium periodate, stirring and reacting for 3 days under the condition of keeping out of the sun, centrifuging, and washing a precipitate to obtain dialdehyde cellulose (DAC);

2) heating and stirring dialdehyde cellulose to be completely dissolved in water bath at 100 ℃ to obtain transparent solution A;

3) dissolving Chitosan (CS) in acetic acid water solution, stirring until the Chitosan (CS) is completely dissolved to prepare transparent solution B with the chitosan content of 1%;

4) dropwise adding the transparent solution A into the transparent solution B until the gelation reaction is completed, and then washing with water to prepare the novel chitosan hydrogel with the concentration of the transparent solution A being 10%.

Through detection and analysis, in the step 1) of the example 1, after the reaction is stirred for 3 days under the condition of keeping out of the light, the oxidation degree of the obtained DAC is 90%.

Example 2

1) mixing the cellulose suspension with the content of 1% with sodium periodate, stirring and reacting for 3 days under the condition of keeping out of the sun, centrifuging, and washing a precipitate to obtain DAC;

2) heating and stirring the DAC to be completely dissolved in a water bath condition at 100 ℃ to obtain a transparent solution A;

3) dissolving Chitosan (CS) in an acetic acid aqueous solution, and stirring until the Chitosan (CS) is completely dissolved to obtain a transparent solution B with the chitosan content of 1%;

4) dropwise adding the transparent solution A into the transparent solution B till the gelation reaction is finished, and then washing with water to prepare the novel chitosan hydrogel with the concentration of the transparent solution A being 7.5%.

Example 3

1) mixing cellulose suspension with the content of 1% and sodium periodate, stirring and reacting for 3 days under the condition of keeping out of the sun, centrifuging, and washing a precipitate to obtain dialdehyde cellulose;

4) dropwise adding the transparent solution A into the transparent solution B until the gelation reaction is completed, and then washing with water to prepare the novel chitosan hydrogel with the concentration of the transparent solution A being 5%.

Example 4

4) dropwise adding the transparent solution A into the transparent solution B till the gelation reaction is finished, and then washing with water to prepare the novel chitosan hydrogel with the concentration of the transparent solution A being 2.5%.

1) Appearance observation and analysis

The appearance of the hydrogel prepared in examples 1 to 4 is shown in FIG. 1. Among them, D ═ C1, D ═ C2, D ═ C3, and D ═ C4 correspond to the novel chitosan hydrogels prepared in example 1, example 2, example 3, and example 4, respectively.

As can be seen from the observation and analysis in FIG. 1, in example 4, the concentration of the transparent solution A is the lowest, so that the prepared novel chitosan hydrogel has a lighter appearance color, better fluidity and poorer gel strength, which indicates that the concentration of DAC can influence the gel strength of the hydrogel, the differences in fluidity of the novel chitosan hydrogels prepared in examples 1 to 3 are not obvious, and indicates that the change of the gel strength observable by naked eyes is not large after DAC is increased to a certain concentration.

2) Infrared spectroscopy detection and analysis

The novel chitosan hydrogel obtained in this example 1 and the cellulose, dialdehyde cellulose and chitosan obtained in example 1 were subjected to infrared spectroscopy, and the results are shown in fig. 2.

In FIG. 2, curve (a) shows the IR spectrum of cellulose, curve (b) shows the IR spectrum of DAC, curve (c) shows the IR spectrum of CS, and curve (d) shows the IR spectrum of the novel chitosan hydrogel. From the analysis in FIG. 2, it can be seen that DAC was 1732cm in comparison with the spectrum of cellulose^-1The characteristic absorption peak of the strain is C ═ O tensile vibration at 882cm^-1Has a characteristic absorption peak of tensile vibration of hemiacetal of 1443cm^-1Characteristic absorption peaks of C-H stretching and bending vibration of methylene are shown. After cross-linking of DAC with CS at 1732cm^-1The absorption peak at the position is weakened and is 1643cm^-1The characteristic absorption peak of C ═ N bond appears, and the successful cross-linking of DAC and CS is proved.

3) Thermal stability detection and analysis

The thermal stability of the novel chitosan hydrogel prepared in example 1 and the cellulose, DAC and CS in example 1 was measured, and the results are shown in fig. 3.

In fig. 3, cellulose corresponds to cellulose, and D ═ C corresponds to the novel chitosan hydrogel. From the analysis in fig. 3, it is clear that cellulose shows a phase of weight loss at 336 ℃. The weight loss of DAC before 100 ℃ is related to the formation of its hemiacetal structure with some bound water molecules, and the reason that the thermal stability is lower than that of cellulose between 100 ℃ and 336 ℃ is that the oxidation process of sodium periodate breaks the ordered bonding of cellulose. Compared with DAC, the novel chitosan hydrogel has higher degradation starting temperature. In the temperature range of 30-150 ℃, the novel chitosan hydrogel is more stable than DAC and CS due to the existence of C-N bonds in the hydrogel, and the thermal stability is higher after the DAC and CS are successfully crosslinked.

4) Moisture content detection and analysis

The water content of the novel chitosan hydrogel prepared in the examples 1 to 4 was measured, and the results are shown in fig. 4.

In fig. 4, D ═ C1, D ═ C2, D ═ C3, and D ═ C4 correspond to the novel chitosan hydrogels prepared in example 1, example 2, example 3, and example 4, respectively. From the analysis in fig. 4, the overall water content of the novel chitosan hydrogel exceeded 96% and was not significantly different. The solids content of the hydrogel is a major factor affecting the water content of the hydrogel. Both CS and DAC contain a large number of hydrophilic groups (hydroxyl, amino and aldehyde groups) that can be readily hydrated with water molecules. From the analysis of the experimental results, it can be known that when the concentration of the dialdehyde-based cellulose is increased, more crosslinkable groups are formed, so that the water content of the novel chitosan hydrogel is gradually reduced. Therefore, when the concentration of the dialdehyde-based cellulose solution is increased, the network density of the novel chitosan hydrogel obtained by crosslinking is increased, the solid content is increased, and the water content is reduced.

5) Swelling property detection and analysis under different pH values

Swelling is one of the important characteristics of hydrogels. Due to the crosslinked structure, the hydrogel can swell and retain a large amount of water, and the degree of swelling is closely related to the degree of crosslinking, the higher the degree of crosslinking, the lower the degree of swelling. The swelling property of the novel chitosan hydrogel prepared in the examples 1 to 4 was tested in buffer solutions with different pH values (acidic, neutral and alkaline), and the results are shown in FIG. 5.

In fig. 5, D ═ C1, D ═ C2, D ═ C3, and D ═ C4 correspond to the novel chitosan hydrogels prepared in example 1, example 2, example 3, and example 4, respectively. From the analysis in fig. 5, it is understood that the swelling ratio gradually decreases as the concentration of the dialdehyde-based cellulose increases. The swelling ratio of the novel chitosan hydrogel prepared in example 4 is significantly higher than that of other gels, demonstrating that the degree of crosslinking is minimal, making the novel chitosan hydrogel prepared in example 4 a flowable semi-solid gel. The swelling ratio of the novel chitosan hydrogel prepared in examples 1 to 3 became irregular under alkaline conditions because the alkaline environment caused the degradation of the hydrogel. Under the condition of different pH values, the change of the swelling rate of the same novel chitosan hydrogel has no obvious linear rule, and the swelling property of the novel chitosan hydrogel is proved to have no obvious dependence on the pH value.

6) Water retention detection and analysis under different temperature conditions

Polymers having high absorbency also have excellent water retention. The water retention capacity can be determined by the hydrogen bonds and van der waals effects between water molecules and the hydrogel. The novel chitosan hydrogel prepared in the embodiments 1 to 4 was subjected to water retention detection at different temperatures, and the results are shown in fig. 6.

In fig. 6, D ═ C1, D ═ C2, D ═ C3, and D ═ C4 correspond to the novel chitosan hydrogels prepared in example 1, example 2, example 3, and example 4, respectively, and the water retention capacities at 4 ℃ and 25 ℃ were examined, respectively. From the analysis in fig. 6, it can be seen that the water retention capacity of the novel chitosan hydrogel decreases linearly with the increase of temperature and time, and the water retention rates after 10 hours of storage at 4 ℃ and 25 ℃ are respectively above 85% and above 38%, indicating that the water in the novel chitosan hydrogel is released faster with the increase of temperature. Among them, after storing at 4 ℃ and 25 ℃ for 10 hours, the novel chitosan hydrogel prepared in example 1 had the best water retention rates, 48% and 95%, respectively, demonstrating that as the concentration of dialdehyde cellulose increased, the degree of crosslinking increased, thereby consolidating the density and physical structure of the hydrogel network and improving the water retention performance.

7) Detection and analysis of gel strength

The novel chitosan hydrogel prepared in the examples 1 to 4 was subjected to gel strength test, the strength of the novel chitosan hydrogel was evaluated by a compression test, and the stress and strain thereof were recorded, and the results are shown in fig. 7.

In fig. 7, D ═ C1, D ═ C2, D ═ C3, and D ═ C4 correspond to the novel chitosan hydrogels prepared in example 1, example 2, example 3, and example 4, respectively. When the novel chitosan hydrogel was prepared in examples 1 to 4, the concentration of chitosan was constant, and thus the concentration of dialdehyde cellulose determined the degree of crosslinking of the hydrogel. From the analysis in fig. 7, the strength of the novel chitosan hydrogel increased with the concentration of dialdehyde-based cellulose, demonstrating that dialdehyde-based cellulose contributes to the formation of a dense polymer network.

8) Detection and analysis of rheological properties

Rheological property detection is carried out on the novel chitosan hydrogel prepared in the embodiment 1-4 and the pure chitosan, the rheological property can represent the relationship between hydrogel rheology and polymer chain interaction, the rheological property of the hydrogel is judged by detecting the storage modulus and the loss modulus of the hydrogel, and the result is shown in fig. 8.

In fig. 8, 0, 1, 2, 3 and 4 correspond to pure chitosan, example 1, example 2, example 3 and example 4, respectively, G' represents the storage modulus of the hydrogel, and G "represents the loss modulus of the hydrogel. From the analysis in fig. 8, it can be seen that pure chitosan is a viscous liquid, G "> G'. The overall G 'value of the novel chitosan hydrogel is higher than G' within 0.1-100 rad/s, which proves that the hydrogel has solid and elastic behaviors. The hydrogel is a dynamic network structure based on Schiff base bonds and hydrogen bonds, and analysis in the figure shows that G 'has small dependence on frequency, G' shows a trend of descending first and then ascending, and the formation of an elastic network of the hydrogel is proved. The high oscillatory shear may weaken the original structure of the hydrogel and relax its structure, but as the analysis in the figure shows, both G' and G "increase with increasing DAC concentration, demonstrating that the interaction formed after CS and DAC cross-linking plays an important role in improving rheology. Hydrogel strength is determined by the difference in modulus and properties of the G "and G' curves. The results demonstrate that the difference between G' and G "increases with increasing DAC concentration, and therefore, the rheology of the novel chitosan hydrogel increases with increasing DAC concentration.

9) Detection and analysis of bacteriostatic activity

The novel chitosan hydrogel prepared in the embodiments 1-4 is tested for its bacteriostatic activity. Specifically, the antibacterial activity of the novel chitosan hydrogel was evaluated using escherichia coli (e.coli) and staphylococcus aureus (s.aureus) as experimental models, and the results are shown in fig. 9.

In fig. 9, D ═ C1, D ═ C2, D ═ C3, and D ═ C4 correspond to the novel chitosan hydrogels prepared in example 1, example 2, example 3, and example 4, respectively. As can be seen from the observation and analysis in fig. 9, the novel chitosan hydrogels prepared in examples 1 to 4 all have antibacterial properties, and it is proved that the novel chitosan hydrogels exhibit antibacterial effects on e.coli and s.aureus due to the successful crosslinking of CS and DAC.

In conclusion, the novel chitosan hydrogel provided by the invention is successfully crosslinked by DAC and CS, and is simply stirred to react to obtain the novel biodegradable chitosan antibacterial hydrogel which is environment-friendly, safe and biodegradable. And further experiments prove that the prepared novel chitosan hydrogel has excellent thermal stability, water retention, swelling property, gel strength, rheological property and antibacterial property, so that the novel chitosan hydrogel has very important practical value in the aspects of biomedicine, food, chemical industry and the like.

The above-mentioned embodiments are merely preferred embodiments for fully illustrating the present invention, and the scope of the present invention is not limited thereto. The equivalent substitution or change made by the technical personnel in the technical field on the basis of the invention is all within the protection scope of the invention. The protection scope of the invention is subject to the claims.

Claims

1. A preparation method of novel chitosan hydrogel is characterized by comprising the following steps:

2. The method for preparing the novel chitosan hydrogel according to claim 1, wherein in the step 1), the cellulose suspension contains 0.5-5% by mass of cellulose.

3. The method for preparing a novel chitosan hydrogel according to claim 1, wherein in the step 1), the periodate is sodium periodate.

4. The method for preparing a novel chitosan hydrogel according to claim 1, wherein in the step 3), the chitosan content in the transparent solution B is 1% by weight.

5. The method for preparing the novel chitosan hydrogel according to claim 1, wherein in the step 4), the concentration of the transparent solution A in the novel chitosan hydrogel is 2.5-10%.

6. The method for preparing the novel chitosan hydrogel according to claim 5, wherein the concentration of the transparent solution A in the novel chitosan hydrogel in the step 4) is 10%.

7. A novel chitosan hydrogel prepared by the preparation method as claimed in any one of claims 1 to 6.

8. The use of the novel chitosan hydrogel prepared by the preparation method according to any one of claims 1 to 6 as a wound dressing in biomedicine.