Preparation of high-strength polyacrylamide carboxymethyl chitosan hydrogel

Abstract

This invention belongs to the field of materials science and provides a method for preparing a high-strength polyacrylamide carboxymethyl chitosan hydrogel. This invention introduces CMCs and PDA capsules into the PAAM hydrogel. The PDA capsules undergo a Schiff base reaction with PAAM and CMCs, which increases the crosslinking density of the hydrogel and promotes the formation of a second CMC network. Simultaneously, the deformability of the PDA capsules provides an energy dissipation mechanism for the PAAM / CMC hydrogel. Therefore, this invention provides a novel method for preparing high-mechanical-performance PAAM-based hydrogels, and the prepared high-strength PAAM / CMC hydrogel has high application potential in tissue engineering, biosensing, and other fields.

Description

Technical Field

[0001] This invention belongs to the field of materials, and specifically relates to the preparation of a high-strength polyacrylamide carboxymethyl chitosan hydrogel. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Polyacrylamide (PAAM)-based hydrogels are stable and non-toxic, making them widely used in tissue engineering, drug delivery, and sensors. Introducing functional polymers into PAAM hydrogels can unlock new applications; for example, introducing chitosan can create substrates for cell adhesion. However, due to PAAM's inherent softness and lack of energy dissipation mechanisms, PAAM hydrogels typically exhibit low mechanical strength, limiting their applications. Literature review has shown that strategies such as increasing acrylamide and crosslinking agent concentrations, adding nanomaterials, or introducing bilayer networks can improve the mechanical properties of PAAM hydrogels. Summary of the Invention

[0004] Therefore, this invention provides a method for preparing high-strength polyacrylamide carboxymethyl chitosan hydrogel, which is a new method for improving the mechanical properties of PAAM-based hydrogels and is of great significance to the increasing application demands.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a method for preparing a high-strength polyacrylamide carboxymethyl chitosan hydrogel, comprising:

[0007] Ammonia water is added to reverse osmosis (RO) water and mixed well. Then dimethyldiethoxysilane (DMDES) is added to obtain a mixed solution. The solution is vortexed and allowed to stand to form a DMDES emulsion template.

[0008] Dopamine hydrochloride was dissolved in a buffer solution, and then the DMDES emulsion template was added. The mixture was stirred until homogeneous and the reaction was carried out. After the reaction was completed, ethanol was added and stirred to remove the emulsion template. The supernatant was removed by centrifugation and washed multiple times with RO water to obtain polydopamine (PDA) capsules, and a PDA capsule suspension was prepared.

[0009] Acrylamide, carboxymethyl chitosan (CMCs), initiator, crosslinking agent, and catalyst are dissolved in a PDA capsule suspension;

[0010] At room temperature, aqueous solutions of initiator, crosslinking agent and catalyst containing PDA capsules were added sequentially to a mixed solution of acrylamide and CMCs containing PDA capsules and mixed well. After polymerization, PAAM / CMCs hydrogel containing hollow PDA capsules was formed.

[0011] In a second aspect, the present invention provides a PAAM / CMCs hydrogel containing a hollow PDA capsule prepared by the above method.

[0012] Beneficial effects of the present invention

[0013] (1) This invention introduces CMCs and PDA capsules into PAAM hydrogels. The PDA capsules undergo a Schiff base reaction with PAAM and CMCs, which increases the crosslinking density of the hydrogel and promotes the formation of a second CMC network. Simultaneously, the deformability of the PDA capsules provides an energy dissipation mechanism for the PAAM / CMCs hydrogel. Under the combined effects of these mechanisms, a high-strength PAAM / CMCs hydrogel was prepared.

[0014] (2) In this invention, CMCs and PDA capsules are introduced into PAAM hydrogel to form PDA capsule@PAAM / CMCs hydrogel. Under the same PAAM content, its tensile stress and strain at break are significantly increased compared with PAAM hydrogel and PAAM / CMCs hydrogel, reaching 95.4 kPa and 13.4 times, respectively.

[0015] (3) The preparation method of the present invention is simple, practical and easy to promote. Attached Figure Description

[0016] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. Exemplary embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0017] Figure 1 This is a transmission electron microscope image of the PDA capsule prepared in Example 2 of the present invention;

[0018] Figure 2 This is a scanning electron microscope image of the PAAM hydrogel prepared in Example 3 of the present invention after freeze-drying.

[0019] Figure 3 This is a scanning electron microscope image of the PAAM hydrogel containing PDA capsules prepared in Example 5 of the present invention after freeze-drying.

[0020] Figure 4 This is a scanning electron microscope image of the PAAM / CMCs hydrogel containing PDA capsules prepared in Example 6 of the present invention after freeze-drying.

[0021] Figure 5 The tensile stress and tensile strain curves of the hydrogels prepared in Examples 3, 4, 5, and 6 of this invention are shown. Detailed Implementation

[0022] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0023] A method for preparing a high-strength polyacrylamide carboxymethyl chitosan hydrogel, comprising:

[0024] Ammonia water was added to RO water and mixed well. Then DMDES was added to obtain a mixed solution. The solution was vortexed and allowed to stand to form a DMDES emulsion template.

[0025] Dopamine hydrochloride was dissolved in a buffer solution, and then the DMDES emulsion template was added. The mixture was stirred until homogeneous and the reaction was carried out. After the reaction was completed, ethanol was added and stirred to remove the emulsion template. The supernatant was removed by centrifugation and the product was washed multiple times with RO water to obtain PDA capsules. A PDA capsule suspension was then prepared.

[0026] Acrylamide, CMCs, initiators, crosslinking agents, and catalysts are dissolved in a PDA capsule suspension;

[0027] At room temperature, aqueous solutions of initiator, crosslinking agent and catalyst containing PDA capsules were added sequentially to a mixed solution of acrylamide and CMCs containing PDA capsules and mixed well. After polymerization, PAAM / CMCs hydrogel containing hollow PDA capsules was formed.

[0028] In order to provide a stable DMDES emulsion template, the present invention further explores the ratio of ammonia and DMDES and the mixing process conditions. In an embodiment with better results, the volume ratio of ammonia to DMDES is 1-1.5:1-1.5.

[0029] In a more effective implementation, the vortex mixing time is 1-2 minutes, followed by standing for 4-6 hours.

[0030] The present invention further provides a hollow PDA capsule. The results of numerous experiments conducted by the present invention show that the mass-to-volume ratio of the dopamine hydrochloride to the DMDES emulsion template is 2-4:0.3-0.8 mg / mL, so that there is enough dopamine hydrochloride in the system to form a polydopamine film on the surface of the DMDES emulsion template.

[0031] In some embodiments, the supernatant is removed by centrifugation at 8500-9000g for 5-10 minutes, and then washed with RO water at 5000-6000g 3-5 times, each time for 5-8 minutes.

[0032] In some embodiments, the reaction time between the dopamine hydrochloride solution and the DMDES emulsion template is 24–32 h to form a polydopamine film on the surface of the DMDES emulsion template, which facilitates the subsequent preparation of hollow PDA capsules.

[0033] In some embodiments, the mass ratio of acrylamide, CMCs, initiator, crosslinking agent, and catalyst is 5:0.1-0.2:0.1-0.15:0.01-0.015:0.031-0.035.

[0034] In some embodiments, the concentration of the PDA capsule suspension used to dissolve acrylamide, CMCs, initiator, crosslinking agent, and catalyst is 0.1–1 mg / mL, so that there are enough PDA capsules in the solvent system to undergo Schiff base reaction with the PAAM / CMCs hydrogel, thereby increasing the crosslinking density of the PAAM / CMCs hydrogel.

[0035] In some embodiments, the polymerization reaction time is 10 to 15 minutes to allow the PDA capsules to fully react with the PAAM / CMCs hydrogel, resulting in a PAAM / CMCs hydrogel containing PDA capsules with superior mechanical properties.

[0036] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are explanations of the present invention and not limitations thereof.

[0037] Example 1: Preparation of DMDES emulsion template

[0038] Add 0.4 mL of ammonia water to 19.2 mL of RO water and mix well. Then add 0.4 mL of DMDES. Mix the resulting mixture vigorously with a vortex mixer for 1 min and let it stand for 4 hours to form a DMDES emulsion template.

[0039] Example 2: Preparation of PDA Capsules

[0040] 4 mg of dopamine hydrochloride was dissolved in 1.4 mL of Tris buffer solution (10 mM, pH 8.5). After complete dissolution, 0.6 mL of the DMDES emulsion template from Example 1 was added, and the mixture was reacted in a rotary mixer for 24 hours. After 24 hours, 2 mL of ethanol was added to the mixture, and it was mixed by rotation for 2 min. The supernatant was then removed by centrifugation (8500 g × 5 min), followed by washing three times with 2 mL of RO water (5000 g × 5 min). Finally, the obtained PDA capsules were dispersed in RO water to prepare a PDA capsule suspension with a concentration of 5 mg / mL. Figure 1 As shown, hollow PDA capsules were successfully prepared through the above steps.

[0041] Example 3: Preparation of PAAM hydrogel

[0042] 2.5 g of acrylamide was dissolved in 7 mL of RO water, 0.05 g of initiator ammonium persulfate (APS) was dissolved in 1 mL of RO water, 5 mg of crosslinking agent N,N'-methylenebisacrylamide (BIS) was dissolved in 1 mL of RO water, and 20 μL of catalyst tetramethylethylenediamine (TMEDA) was dissolved in 1 mL of RO water. The aqueous solutions of APS, BIS, and TMEDA were added sequentially to the acrylamide aqueous solution at room temperature and mixed thoroughly. After 10 min, a PAAM hydrogel was formed. Figure 2 As shown, the surface of the freeze-dried PAAM hydrogel is smooth and non-porous.

[0043] Example 4: Preparation of PAAM / CMCs hydrogel

[0044] 2.5 g of acrylamide and 0.05 g of CMCs were dissolved in 7 mL of RO water, 0.05 g of APS was dissolved in 1 mL of RO water, 5 mg of crosslinking agent BIS was dissolved in 1 mL of RO water, and 20 μL of TMEDA was dissolved in 1 mL of RO water. The aqueous solutions of APS, BIS, and TMEDA were added sequentially to the mixed aqueous solution of acrylamide and CMCs at room temperature and mixed thoroughly. After polymerization for 10 min, a PAAM / CMCs hydrogel was formed.

[0045] Example 5: Preparation of PAAM hydrogel containing PDA capsules

[0046] A 5 mg / mL PDA capsule suspension was diluted with RO water to obtain a 0.3 mg / mL PDA capsule suspension. Then, 2.5 g of acrylamide was dissolved in 7 mL of the 0.3 mg / mL PDA capsule suspension, 0.05 g of APS was dissolved in 1 mL of the 0.3 mg / mL PDA capsule suspension, 0.005 g of crosslinking agent BIS was dissolved in 1 mL of the 0.3 mg / mL PDA capsule suspension, and 20 μL of TMEDA was dissolved in 1 mL of the 0.3 mg / mL PDA capsule suspension. At room temperature, aqueous solutions of APS, BIS, and TMEDA containing PDA capsules were sequentially added to an aqueous solution of acrylamide containing PDA capsules and mixed thoroughly. After polymerization for 10 min, a PAAM hydrogel containing PDA capsules was formed. Figure 3 As shown, the surface of the freeze-dried PAAM hydrogel containing PDA capsules has a large number of non-connected pores, indicating that the PDA capsules are uniformly dispersed in the PAAM hydrogel. The scanning electron microscope image of the freeze-dried PAAM hydrogel containing PDA capsules is shown below. Figure 3 As shown.

[0047] Example 6: Preparation of PAAM / CMCs hydrogel containing PDA capsules

[0048] 2.5 g of acrylamide and 0.05 g of CMCs were dissolved in 7 mL of a 0.3 mg / mL PDA capsule suspension; 0.05 g of APS was dissolved in 1 mL of a 0.3 mg / mL PDA capsule suspension; 0.005 g of crosslinking agent BIS was dissolved in 1 mL of a 0.3 mg / mL PDA capsule suspension; and 20 μL of TMEDA was dissolved in 1 mL of a 0.3 mg / mL PDA capsule suspension. At room temperature, aqueous solutions of APS, BIS, and TMEDA containing PDA capsules were sequentially added to a mixed solution of acrylamide and CMCs containing PDA capsules and mixed thoroughly. After polymerization for 10 min, a PAAM / CMCs hydrogel containing PDA capsules was formed. Figure 4 As shown, the PAAM / CMCs hydrogel containing PDA capsules exhibits a connected network structure.

[0049] The mechanical properties of the hydrogels prepared in Examples 3, 4, 5, and 6 above were tested, such as... Figure 5As shown, under the same PAAM content conditions, introducing 0.5 wt% CMCs into PAAM hydrogel to form PAAM / CMCs hydrogel resulted in lower tensile stress and fracture strain compared to PAAM hydrogel, indicating that the introduction of CMCs reduced the mechanical properties of PAAM hydrogel. Introducing PDA capsules into PAAM hydrogel to form PDA capsule@PAAM hydrogel increased both tensile stress and fracture strain, indicating that hollow PDA capsules can improve the mechanical properties of PAAM hydrogel. When PDA capsules were introduced into PAAM / CMCs hydrogel (i.e., PDA capsule@PAAM / CMCs hydrogel), the tensile stress and fracture strain significantly increased to 95.4 kPa and 13.4 times, respectively, far exceeding the tensile stress and fracture strain of PAAM / CMCs hydrogel, PAAM hydrogel, and PDA capsule@PAAM hydrogel, indicating that hollow PDA capsules significantly improved the mechanical properties of PAAM / CMCs hydrogel.

[0050] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a high-strength polyacrylamide carboxymethyl chitosan hydrogel, characterized by, include: Ammonia water was added to reverse osmosis water and mixed well. Then dimethyldiethoxysilane (DMDES) was added to obtain a mixed solution. The solution was vortexed and allowed to stand to form a DMDES emulsion template. Dopamine hydrochloride was dissolved in a buffer solution, and then the DMDES emulsion template was added. The mixture was stirred until homogeneous and the reaction was carried out. After the reaction was completed, ethanol was added and stirred until homogeneous to remove the emulsion template. The supernatant was removed by centrifugation and the capsules were washed multiple times with reverse osmosis water to obtain polydopamine PDA capsules and prepare a PDA capsule suspension. Acrylamide, carboxymethyl chitosan (CMCs), initiator, crosslinking agent, and catalyst were dissolved in a PDA capsule suspension. At room temperature, aqueous solutions of initiator, crosslinking agent and catalyst containing PDA capsules were added sequentially to a mixed solution of acrylamide and CMCs containing PDA capsules and mixed well. After polymerization, PAAM / CMCs hydrogel containing hollow PDA capsules was formed. The mass ratio of acrylamide, CMCs, initiator, crosslinking agent, and catalyst is 5:0.1~0.2:0.1~0.15:0.01~0.015:0.031~0.

035.

2. The method for preparing the high-strength polyacrylamide carboxymethyl chitosan hydrogel as described in claim 1, characterized in that, The volume ratio of ammonia to DMDES is 1~1.5:1~1.

5.

3. The method for preparing the high-strength polyacrylamide carboxymethyl chitosan hydrogel as described in claim 1, characterized in that, The vortex mixing time is 1~2 minutes, and the mixture is left to stand for 4~6 hours.

4. The method for preparing the high-strength polyacrylamide carboxymethyl chitosan hydrogel as described in claim 1, characterized in that, The mass-to-volume ratio of dopamine hydrochloride to DMDES emulsion template is 2~4:0.3~0.8 mg / mL.

5. The method for preparing the high-strength polyacrylamide carboxymethyl chitosan hydrogel as described in claim 1, characterized in that, Centrifuge at 8500-9000g for 5-10 minutes to remove the supernatant, then wash with RO water at 5000-6000g 3-5 times, 5-8 minutes each time.

6. The method for preparing the high-strength polyacrylamide carboxymethyl chitosan hydrogel as described in claim 1, characterized in that, The reaction time between the dopamine hydrochloride solution and the DMDES emulsion template is 24-32 h.

7. The method for preparing the high-strength polyacrylamide carboxymethyl chitosan hydrogel as described in claim 1, characterized in that, The concentration of the PDA capsule suspension used to dissolve acrylamide, carboxymethyl chitosan, initiator, crosslinking agent, and catalyst is 0.1~1 mg / mL; or the polymerization reaction time is 10~15 min.

8. PAAM / CMCs hydrogel containing hollow PDA capsules prepared by the method according to any one of claims 1-7.

9. The application of the PAAM / CMCs hydrogel containing hollow PDA capsules as described in claim 8, characterized in that, The PAAM / CMCs hydrogel containing hollow PDA capsules is used in tissue engineering and biosensing.

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