A slow water-absorbing hydrogel for simulating a nerve compression model and a method for preparing the same

Abstract

The application discloses a slow water-absorbing hydrogel for simulating a nerve compression model and a preparation method thereof, and belongs to the technical field of high polymer materials. The SA-PAM-CSCL composite hydrogel is prepared by using an ultraviolet irradiation method, wherein monomer AM and a crosslinking agent are polymerized by free radicals under the action of a photoinitiator to prepare a PAM network, and a basic hydrogel skeleton is obtained; -NH2 in the PAM macromolecule and -COOH in the SA molecule are chemically crosslinked to form an amide bond; and SA and CSCL are electrostatically interacted to form an interpenetrating network structure between the macromolecules. The cyclic compression curves of the composite hydrogel almost overlap, and the composite hydrogel has good elastic performance and very excellent self-recovery performance; and the raw materials used have good biocompatibility, so that the composite hydrogel is an ideal material for constructing a simulating nerve compression model.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of high polymer materials, and particularly relates to a slow water-absorbing hydrogel for simulating a nerve compression model and a preparation method thereof. BACKGROUND

[0002] The hydrogel is a three-dimensional network structure polymer material formed by single or multiple homopolymers or copolymers through chemical cross-linking (through covalent bonds, etc.) or physical cross-linking (such as physical crystallization, coordination bonds and hydrogen bonds, etc.), and has the characteristics of hydrophilicity and hydrophobicity, and can be absorbed and swollen in an aqueous medium while not being dissolved. The slow water-absorbing hydrogel can be used for simulating a nerve compression model due to its slow water-absorbing property, strong compressibility and good biocompatibility.

[0003] Polyacrylamide (PAM) is a general term for homopolymers of acrylamide or polymers obtained by copolymerization with other monomers, and is one of the most widely used varieties of water-soluble polymers. However, the pure PAM hydrogel has a single network structure, which makes the water-absorbing rate very fast and the compression performance very poor, so it is difficult to be used for simulating a nerve compression model. Therefore, other monomers need to be added to form an interpenetrating network to achieve slow water absorption and strong compressibility for accurately simulating the chronic compression of nerves.

[0004] The prior art finds that the hydrogel for simulating nerve compression has a dense network structure, which results in good compression performance, but the water-absorbing rate is very fast and the equilibrium swelling time is very short. Therefore, there is an urgent need to develop a hydrogel with balanced compression performance and slow water-absorbing performance. SUMMARY

[0005] This section is intended to summarize some aspects of the embodiments of the present application and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of the specification to avoid obscuring the purpose of this section, the abstract and the title, and such simplifications or omissions cannot be used to limit the scope of the present application.

[0006] In view of the above and / or problems existing in the prior art, the present application is proposed.

[0007] Therefore, the purpose of the present application is to overcome the deficiencies in the prior art and provide a preparation method of a slow water-absorbing hydrogel for simulating a nerve compression model.

[0008] To solve the above technical problems, the present application provides the following technical solutions, comprising,

[0009] Mixing chitosan hydrochloride (CSCL) and deionized water to obtain solution A;

[0010] Mixing acrylamide and sodium alginate with deionized water to obtain solution B;

[0011] The photoinitiator and the crosslinking agent are added into the solution B and mixed uniformly to obtain a solution C;

[0012] The solution C and the solution A are stirred to obtain a SA-PAM-CSCL gel solution, and the SA-PAM-CSCL hydrogel is obtained after standing and irradiation under 365 nm ultraviolet light.

[0013] As a preferred solution of the preparation method of the slow water-absorbing hydrogel for simulating the nerve compression model, the mass fraction of the chitosan hydrochloride in the solution A is 4.8-5.2%.

[0014] As a preferred solution of the preparation method of the slow water-absorbing hydrogel for simulating the nerve compression model, the mass fraction of the acrylamide in the solution B is 12.0-12.5%, and the mass fraction of the sodium alginate is 1.8-2%.

[0015] As a preferred solution of the preparation method of the slow water-absorbing hydrogel for simulating the nerve compression model, the mass fraction of the photoinitiator in the solution C is 0.7-0.8%, and the mass fraction of the crosslinking agent is 0.04-0.06%.

[0016] As a preferred solution of the preparation method of the slow water-absorbing hydrogel for simulating the nerve compression model, the photoinitiator comprises 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, and the crosslinking agent comprises N,N'-methylenebisacrylamide.

[0017] As a preferred solution of the preparation method of the slow water-absorbing hydrogel for simulating the nerve compression model, the mass fraction of the chitosan hydrochloride in the SA-PAM-CSCL gel solution is 10-15%.

[0018] As a preferred solution of the preparation method of the slow water-absorbing hydrogel for simulating the nerve compression model, the stirring is performed at a stirring speed of 150-200 rpm, a stirring temperature of 20-30°C, and a stirring time of 5-15 min.

[0019] As a preferred solution of the preparation method of the slow water-absorbing hydrogel for simulating the nerve compression model, the ultraviolet light irradiation is performed for 35-45 min.

[0020] Another object of the present application is to provide a slow water-absorbing hydrogel.

[0021] The third object of the present application is to overcome the deficiencies in the prior art and provide a use of a slow water-absorbing hydrogel in a simulated nerve compression model.

[0022] The present application has the following advantages:

[0023] The present application creatively prepares the interpenetrating network composite hydrogel through chemical cross-linking and physical cross-linking by electrostatic interaction. The method is simple to operate, and the prepared hydrogel has excellent slow water-absorbing performance: the swelling equilibrium time is not less than 90 h, and the equilibrium swelling rate is not less than 300%; the compression performance is excellent: the compressive strength is not less than 20 MPa, the compression modulus is not less than 20 MPa, and the five compression cycle curves are basically overlapped. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor. Among them:

[0025] Figure 1 (A)~(E) are the unswollen comparative example 1 and examples 1~4; Figure 1 (a)~(e) are the swollen comparative example 1 and examples 1~4.

[0026] Figure 2 is the line graph of the swelling rate change and the equilibrium swelling rate change of the composite hydrogel of comparative example 1 and examples 1~4.

[0027] Figure 3 is the swelling equilibrium time column chart of the composite hydrogel of comparative example 1 and examples 1~4.

[0028] Figure 4 (a)~(e) are the five-cycle compression curve graphs of comparative example 1 and examples 1~4 under 80% strain. DETAILED DESCRIPTION

[0029] In order to make the above-mentioned objects, features and advantages of the present application more apparent and easy to understand, the specific embodiments of the present application will be described in detail in conjunction with the description of the present application.

[0030] In the following description, many specific details are set forth in order to provide a thorough understanding of the present application, but the present application can also be implemented in other ways different from those described herein, and those skilled in the art can make similar generalizations without departing from the connotation of the present application, therefore the present application is not limited to the specific embodiments disclosed below.

[0031] Second, the "one embodiment" or "an embodiment" referred to herein means a specific feature, structure, or characteristic under discussion. Thus, "an embodiment" appearing in one place does not necessarily mean the same embodiment as "an embodiment" appearing in other places, making this term or phrase connotes a specific feature, structure, or characteristic and does not require adherence to a single format or protocol, and can include single or multiple dependent or independent uses thereof. It should be noted that, as used in this specification and the appended claims, the singular forms "a," "an" and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a component" or "the component" can include several components unless the context clearly dictates otherwise.

[0032] The raw materials used in the present application are all commercially available.

[0033] The substances in the present application are abbreviated as follows:

[0034] Sodium alginate (SA), acrylamide (AM), polyacrylamide (PAM), chitosan hydrochloride (CSCL), 2-hydroxy-4'- (2-hydroxyethoxy)-2-methylpropiophenone (I2959), N, N'- methylenebisacrylamide (MBA).

[0035] The raw materials and specifications used in the embodiments of the present application are shown in the following table:

[0036]

[0037]

[0038] The materials prepared in the embodiments of the present application are tested for performance according to the following method:

[0039] Scanning electron microscope (SEM): The prepared hydrogel is divided into two groups, one group is directly pre-frozen, and the other group is pre-frozen after swelling for 2h, both groups are subjected to freeze-drying treatment, and the dried sample is quenched with liquid nitrogen, and the morphology characteristics are recorded by SEM, the gold is sprayed uniformly, and the acceleration voltage is 3.0kv.

[0040] Swelling performance test: The prepared hydrogel is placed at room temperature for 3h, and weighed to obtain the initial weight W0. The room temperature immersion method is used, the hydrogel sample is immersed and swelled in phosphate buffer solution (PBS) at room temperature, the hydrogel is taken out every 5h, the surface residual liquid is absorbed, and the sample is weighed to obtain the wet weight W s of the hydrogel sample. This is repeated until the mass of the hydrogel no longer changes, i.e. the swelling equilibrium is reached, and the swelling curve is obtained. The influence of the chemical composition and three-dimensional network structure of the hydrogel on its performance is analyzed by studying the swelling behavior of the hydrogel in the PBS buffer solution. The swelling rate (S%) of the hydrogel sample can be obtained by the following formula:

[0041]

[0042] wherein, W S is the mass of the hydrogel when swelling at 25℃; and W0 is the mass of the dry gel.

[0043] Compressive cyclic performance test: the computerized tensile-compressive tester (KJ-1065A, Dongguan, China) was used to evaluate the compressive cyclic performance of the hydrogel. The compression test of the hydrogel was carried out at room temperature with a compression speed of 5 mm / min. The stress-strain curve was obtained by using a cylindrical hydrogel with a diameter of 12 mm and a height of 10 mm, and each test was repeated 5 times.

[0044] Example 1

[0045] The present embodiment provides a preparation method of a slow water-absorbing hydrogel for simulating a nerve compression model, in particular to:

[0046] 1) Preparation of solution A: 2.63 g of chitosan hydrochloride was added to 50 mL of deionized water, stirred at 25°C for 50 min to mix uniformly, to obtain a chitosan hydrochloride solution with a mass fraction of 5%, denoted as solution A;

[0047] 2) Preparation of solution B: 6.025 g of acrylamide (AM) and 0.975 g of sodium alginate (SA) were mixed uniformly with 43 ml of deionized water to obtain an acrylamide-sodium alginate solution, denoted as solution B, wherein the mass fraction of acrylamide is 12.05%, and the mass fraction of sodium alginate is 1.95%;

[0048] 3) Preparation of solution C: 0.04 g of photoinitiator 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone (I2959) and 0.0025 g of crosslinking agent N,N′-methylenebisacrylamide (MBA) were added to 5 g of solution B to mix uniformly to obtain a SA-PAM solution, denoted as solution C;

[0049] 4) 0.26 g of solution A was added to 5 g of solution C to obtain a SA-PAM-CSCL gel solution, wherein the mass fraction of CSCL is 5%, and the gel solution was left to remove the bubbles in the gel solution; then the gel solution was poured into a culture dish and irradiated with 365 nm ultraviolet light for 40 min to obtain a SA-PAM-CSCL 5% hydrogel.

[0050] Example 2

[0051] The difference between the present embodiment and Example 1 is that the amount of solution A added in step 4) is adjusted to 0.56 g, so that the mass fraction of CSCL in the SA-PAM-CSCL gel solution is 10%, and the rest of the preparation process is the same as that of Example 1, to prepare a SA-PAM-CSCL 10% hydrogel.

[0052] Example 3

[0053] The difference between this example and Example 1 is that the amount of solution A added in step 4) is adjusted to 0.88 g, so that the mass fraction of CSCL in the SA-PAM-CSCL gel solution is 15%, and the rest of the preparation process is the same as that of Example 1, to obtain SA-PAM-CSCL 15% hydrogel.

[0054] Example 4

[0055] The difference between this example and Example 1 is that the amount of solution A added in step 4) is adjusted to 1.25 g, so that the mass fraction of CSCL in the SA-PAM-CSCL gel solution is 20%, and the rest of the preparation process is the same as that of Example 1, to obtain SA-PAM-CSCL 20% hydrogel.

[0056] Comparative Example 1

[0057] The difference between this comparative example and Example 1 is that the amount of solution A added in step 4) is adjusted to 0, and the rest of the preparation process is the same as that of Example 1, to obtain SA-PAM hydrogel.

[0058] The microstructure of the hydrogels prepared in the above examples and comparative examples is characterized, and the results are shown in Figure 1 .

[0059] Figure 1 (A) to (E) are respectively the unswollen comparative example 1, examples 1 to 4; Figure 1 (a) to (e) are respectively the swollen comparative example 1, examples 1 to 4. It can be seen from Figure 1 (A) that the surface morphology of comparative example 1 is honeycomb-shaped, indicating that the network structure formed by SA and PAM is distributed in order. From Figure 1 (B) to (E), it can be seen that after adding CSCL, the internal structure of the composite hydrogels of examples 1 to 4 also has a similar typical honeycomb shape, but compared with the comparative example, the pores are relatively small and the pore distribution is more uniform, which is mainly because the addition of CSCL to the SA and PAM composite hydrogel forms more uniform and dense interpenetrating structures among the three, making the pore size smaller, and Figure 1 From the pore distribution in (B) to (E), it can be seen that the pore size of the hydrogel decreases with the increase of the content of CSCL; the pore thickness increases with the increase of the content of CSCL; the pore distribution is averaged with the increase of the content of CSCL, but when the content of CSCL is 15%, the average of the pore distribution decreases with the increase of the content of CSCL, indicating that too much CSCL will destroy the regularity of the crosslinked network due to steric hindrance effect. Figure 1 It can be seen from (b) to (e) that the swollen hydrogel has larger pores than the unswollen hydrogel due to water absorption, and the pore size of the hydrogel decreases with the increase of the content of CSCL.

[0060] The hydrogels prepared in the above examples and comparative examples were subjected to swelling performance test, and the results are shown in Table 1 below.

[0061] Table 1

[0062]

[0063] Figure 2 is the influence of different CSCL contents on the swelling rate change and equilibrium swelling rate of the composite hydrogel; Figure 3 is the swelling equilibrium time of the composite hydrogel with different CSCL contents.

[0064] From Table 1 and Figure 2 It can be seen that the swelling rate of Comparative Example 1 is fast, the equilibrium swelling rate is large, but the swelling equilibrium time is short, and the swelling equilibrium time is 32 h, while the swelling equilibrium time of Examples 1-4 is higher than that of Comparative Example 1, because the CSCL will form hydrogen bond interaction with the SA-PAM crosslinking network, so that the system structure is more stable and not easy to be destroyed by swelling. The swelling performance of Example 3 is the best, the swelling equilibrium time is 116 h, and the equilibrium swelling rate is 324.90%; the swelling equilibrium time of Example 1 is 39 h, and the equilibrium swelling rate is 328.89%; the swelling equilibrium time of Example 2 is 54 h, and the equilibrium swelling rate is 298.12%; the swelling equilibrium time of Example 4 is 106 h, and the equilibrium swelling rate is 386.98%, the swelling equilibrium time is shorter than that of Example 3, because too much CSCL content will destroy the regularity of the crosslinking network due to steric hindrance effect, so that the gel structure becomes unstable, thereby affecting the swelling performance. From Figure 3 It can be seen that when the content of CSCL is less than 15%, increasing the content of CSCL can significantly increase the swelling equilibrium time of the hydrogel. But when the content of CSCL is greater than 15%, with the increase of the content of CSCL, the swelling rate gradually rises, and the equilibrium swelling rate also increases, but the swelling equilibrium time is shortened. This is consistent with the results of microstructure characterization, which shows that the swelling equilibrium time is related to the pore size and porosity, and the smaller the pore size and the more uniform the pore distribution, the longer the swelling equilibrium time. But when the content of CSCL is too much, the regularity of the crosslinking network will be destroyed due to steric hindrance effect, and the swelling equilibrium time will also be reduced.

[0065] The hydrogels prepared in Comparative Example 1 and Examples 1-4 were subjected to compression performance test.

[0066] Figure 4 (a)-(e) are the five-cycle compression curve graphs of Comparative Example 1 and Examples 1-4 at 80% strain. From Figure 4It can be seen that in the cyclic process, the stress-strain curve clearly shows different paths, giving a hysteresis loop. The hysteresis of the stress-strain curve throughout the process reflects the energy dissipation and viscoelasticity of the composite hydrogel. From Figure 4 (a) It can be seen that the hysteresis loop area of the first cycle of the comparative example is large, and the hysteresis loop area of the subsequent several cycles becomes smaller, and the stress also gradually decreases, indicating that energy is dissipated, and the five cycle curves almost do not overlap, indicating that the comparative example has irreversible deformation. From Figure 4 (b) to (e) can be seen that the hysteresis loops of examples 1 to 4 are smaller, and Figure 4 (d) can be seen that the five cycle curves of example 3 almost overlap, and the macrostructure of the gel does not appear to be damaged at 80% strain, which indicates that example 3 not only has good elastic properties, but also has very excellent self-recovery properties. The amide bond in the network can maintain the integrity of the hydrogel, and at the same time, the existence of weak hydrogen bonds also helps to dissipate energy during loading. However, when the content of CSCL is too high (content 20%), the Figure 4 (e) can be seen that example 4 will destroy the regularity of the crosslinked network due to steric hindrance effect, the overlap rate of the cycle curve decreases, indicating that the self-recovery performance has decreased.

[0067] Example 5

[0068] The difference between this example and example 3 is that the mass of the photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (I2959) is adjusted from 0.04 g (mass fraction 0.8%) to 0.035 g (mass fraction 0.7%), and the rest of the preparation process is the same as example 3, to prepare SA-PAM-CSCL hydrogel.

[0069] Example 6

[0070] The difference between this example and example 3 is that the mass of the photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (I2959) is adjusted from 0.04 g (mass fraction 0.8%) to 0.0375 g (mass fraction 0.75%), and the rest of the preparation process is the same as example 3, to prepare SA-PAM-CSCL hydrogel.

[0071] Comparative Example 2

[0072] The difference between this comparative example and example 3 is that the mass of the photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (I2959) is adjusted from 0.04 g (mass fraction 0.8%) to 0.045 g (mass fraction 0.9%), and the rest of the preparation process is the same as example 1, to prepare SA-PAM-CSCL hydrogel.

[0073] The materials prepared in the above examples were subjected to swelling performance test, and the comparison results with Example 3 are shown in Table 2.

[0074] Table 2

[0075]

[0076] As can be seen from the above table, adjusting the addition amount of the photoinitiator I2959 has a significant effect on the performance of the SA-PAM-CSCL hydrogel. When the content of the photoinitiator is less than 0.8%, the swelling equilibrium time gradually increases and the equilibrium swelling rate gradually decreases with the increase of the photoinitiator, because the increase of free radicals makes the polymerization and crosslinking reactions more perfect, the pore size of the composite hydrogel becomes smaller, and thus the water absorption is slow, meeting the requirement of slow water absorption. When the content of the photoinitiator is higher than 0.8%, the absorption rate is significantly reduced, and the possible reason is that the increase of the free radical concentration leads to excessive crosslinking between molecular chains due to chain transfer reaction, and thus the absorption rate decreases. In summary, the preferred mass fraction of the photoinitiator I2959 in the application is 0.8%.

[0077] Example 7

[0078] The difference between this example and Example 3 is that the ultraviolet light irradiation time of 40 min is adjusted to 35 min, and the rest of the preparation process is the same as that of Example 1, and the SA-PAM-CSCL hydrogel is prepared.

[0079] Example 8

[0080] The difference between this example and Example 3 is that the ultraviolet light irradiation time of 40 min is adjusted to 45 min, and the rest of the preparation process is the same as that of Example 1, and the SA-PAM-CSCL hydrogel is prepared.

[0081] The materials prepared in the above examples were subjected to performance test, and the comparison results with Example 3 are shown in Table 3.

[0082] Table 3

[0083]

[0084] As can be seen from the above table, adjusting the ultraviolet light irradiation time has a significant effect on the performance of the SA-PAM-CSCL hydrogel, because the shortening of the irradiation time affects the chain initiation and chain growth rate, leading to the decrease of the polymerization degree and crosslinking degree, and thus the hydrogel cannot be formed. When the irradiation time is too long, the formed crosslinking network is too dense, which can lead to the dense pore size of the hydrogel, rapid water absorption and swelling, and the decrease of the swelling equilibrium time. In summary, the preferred ultraviolet light irradiation time in the application is 40 min.

[0085] Comparative Example 3

[0086] A 10 wt% aqueous solution of polyvinyl alcohol was subjected to directional freezing-thawing three times using liquid nitrogen. The prepared hydrogel was immersed in an aqueous solution containing acrylamide (3.0 mol / L), and after sufficient swelling, the polymerization of acrylamide was initiated by 60Co γ-ray irradiation, thereby forming a second network. The dried double-network hydrogel was immersed in a 10 wt% aqueous glutaraldehyde solution for 30 s, and immediately after immersion, drying was performed. This process was repeated ten times.

[0087] Comparative Example 4

[0088] The difference between this comparative example and Example 3 is that the CSCL was adjusted to HACC (chitosan quaternary ammonium salt), and the rest of the preparation process was the same as Example 1, and the SA-PAM-HACC hydrogel was prepared.

[0089] The material prepared in the above comparative example was subjected to performance testing, and the comparison results with Example 3 are shown in Table 3.

[0090] Table 3

[0091]

[0092] As can be seen from the above table, Comparative Example 3 is a hydrogel currently used to simulate a nerve compression model, and its swelling equilibrium time is very short, which cannot meet the requirements of simulating a chronic animal model of nerve compression; the addition of HACC in Comparative Example 4 causes obvious entanglement of the macromolecular chains of the hydrogel, thereby affecting the swelling behavior of the hydrogel. In Example 3, the CSCL has Cl - present, thereby balancing the charges and avoiding the phenomenon of excessive entanglement of macromolecules.

[0093] Through the above examples and comparative examples, it is found that the hysteresis loops of Examples 1-4 are all smaller after five compression cycles, and the five-cycle curves of Example 3 almost overlap, and the macroscopic structure of the gel does not appear to be damaged at 80% strain, which indicates that Example 3 not only exhibits good elastic properties, but also has very excellent self-recovery properties. It is confirmed that Example 3 has produced excellent effects in improving the compression resistance of the hydrogel by combining CSCL in the SA-PAM system through a specific method.

[0094] In summary, the present application creatively prepares the interpenetrating network composite hydrogel through chemical cross-linking and physical cross-linking by electrostatic interaction, first prepares a chitosan hydrochloride (CSCL) aqueous solution with a specific concentration for standby, then prepares an acrylamide (AM) and sodium alginate (SA) solution with a specific ratio, then adds a specific ratio of a photoinitiator (I2959) and a cross-linking agent (N,N'-methylene bisacrylamide) and mixes uniformly, then adds a specific ratio of the chitosan hydrochloride (CSCL) solution, and finally transfers the solution to a culture dish, irradiates under 365 nm ultraviolet light at room temperature for 35-45 min, to obtain the SA-PAM-CSCL hydrogel.

[0095] The acrylamide (AM) and the cross-linking agent N,N'-methylene bisacrylamide (MBA) are prepared into a PAM network under the action of a photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (I2959) through free radical polymerization, to obtain a basic hydrogel skeleton. The sodium alginate (SA) is a natural anionic polysaccharide substance, which can be cross-linked with divalent or multivalent cations to form a hydrogel, and is concerned due to its abundant source and low price. The chitosan hydrochloride (CSCL) is a chitosan derivative, which is concerned due to its solubility and antibacterial property, and is one of the popular research directions in the field of modified chitosan. The chitosan is modified by salting, which not only retains the advantages of chitosan itself, but also further enhances the positive charge and the bactericidal and bacteriostatic effect. The -NH2 in the PAM and the -COOH in the SA molecule can be chemically cross-linked to form an amide bond, thereby constructing a new network structure. The SA and the CSCL perform mutual electrostatic interaction, thereby constructing an interpenetrating network structure between macromolecules, increasing the porosity and the cross-linking density of the hydrogel, and realizing the balance of the slow water absorption performance and the compression performance. The problems of fast water absorption and unstable structure of the traditional hydrogel are solved.

[0096] The present application finds that when the first layer network system is prepared by chemical cross-linking, the ratio of acrylamide and sodium alginate, and the mass fraction of the photoinitiator and the cross-linking agent will affect the morphology of the composite hydrogel and its stability in an aqueous solution. It is found that when the mass fraction of acrylamide in the acrylamide and sodium alginate aqueous solution is 12.0-12.5%, the mass fraction of sodium alginate is 1.5-2.0%, the mass fraction of the photoinitiator I2959 in the polyacrylamide-sodium alginate aqueous solution is 0.7-0.8%, and the mass fraction of the cross-linking agent MBA is 0.04-0.06%, the phenomenon of obvious macromolecular aggregation can be avoided, and the balance of the slow water absorption performance and the high compression resistance performance can be realized at the same time.

[0097] The present application researches and finds that, in the process of preparing the polyacrylamide-sodium alginate-chitosan hydrogel based on the polyacrylamide-sodium alginate solution under the foregoing optimized conditions, the slow water absorption performance and the compression resistance of the hydrogel are significantly improved when the mass fraction of the chitosan hydrochloride in the mixed system is 10-15%, and the concentration and solid content of the chitosan hydrochloride aqueous solution is 4.8-5.2 wt%; the SA-PAM-CSCL composite hydrogel obtained by adding the chitosan hydrochloride solution with a mass fraction of 15% into the SA-PAM solution can simultaneously achieve the following performances: (1) excellent slow water absorption performance: the swelling equilibrium time is not less than 90 h, and the equilibrium swelling rate is not less than 300%; (2) excellent compression performance: the compression strength is not less than 20 MPa, the compression modulus is not less than 20 MPa, and the five compression cycle curves are basically overlapped.

[0098] It should be noted that the above examples are only used to illustrate the technical solutions of the present application but not limit the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced equivalently without departing from the spirit and scope of the technical solutions of the present application, and all of them should be covered in the scope of the claims of the present application.

Claims

1. A method for preparing a slow water-absorbing hydrogel for simulating a nerve compression model, characterized by: Comprising, The chitosan hydrochloride and deionized water are mixed to obtain solution A; The acrylamide and sodium alginate are mixed with deionized water to obtain solution B; The photoinitiator and crosslinking agent are added into solution B and mixed to obtain solution C; Solution C and solution A are stirred to obtain a uniform solution, and SA-PAM-CSCL gel solution is obtained, which is irradiated by 365 nm ultraviolet light after standing to obtain SA-PAM-CSCL hydrogel; The hydrogel sample is placed into a phosphate buffer solution and swells at room temperature by using normal temperature water immersion method, the hydrogel is taken out every 5 h, the surface residual liquid is absorbed, and the process is repeated until the mass of the hydrogel does not change, the swelling equilibrium is reached, the swelling equilibrium time of the hydrogel is not less than 90 h, and the equilibrium swelling rate is not less than 300 %. The cylindrical hydrogel with a diameter of 12 mm and a height of 10 mm is compressed at a compression speed of 5 mm / min at room temperature, and the five-cycle compression stress-strain curves of the hydrogel at 80 % strain are substantially overlapped.

2. The preparation method of a slow water-absorbing hydrogel for simulating a nerve compression model according to claim 1, characterized by: The photoinitiator comprises 2-hydroxy-4'- (2-hydroxyethoxy) -2-methylpropiophenone, and the crosslinking agent comprises N, N'-methylene bisacrylamide.

3. The method for preparing a slow water-absorbing hydrogel simulating a neural compression model according to claim 1, wherein: The stirring is performed at a stirring speed of 150-200 rpm, a stirring temperature of 20-30 DEG C, and a stirring time of 5-15 min.

4. The slow water-absorbing hydrogel prepared by the preparation method of any one of claims 1-3.

5. The slow water-absorbing hydrogel of claim 4 in the application of a simulated nerve compression model.

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