CN112625269B

CN112625269B - Preparation method of high-strength self-lubricating polyvinyl alcohol hydrogel

Info

Publication number: CN112625269B
Application number: CN202011617780.6A
Authority: CN
Inventors: 李巧玲; 范泽文; 韩昕; 张雨
Original assignee: North University of China
Current assignee: North University of China
Priority date: 2020-12-31
Filing date: 2020-12-31
Publication date: 2022-04-05
Anticipated expiration: 2040-12-31
Also published as: CN112625269A

Abstract

The invention belongs to the field of functional polymer material tissue engineering materials, and particularly relates to a preparation method of polyvinyl alcohol hydrogel with high strength and self-lubrication; the raw material comprises polyvinyl alcohol (PVA), hydroxypropyl cellulose (HPC), L-tryptophan (FT), etc.; the PVA long chains are crosslinked through physical entanglement and form multi-stage hydrogen bonds with the short-chain HPC and the FT, and the hydrogen bond network is tighter under the freezing and thawing action, so that the hydrogel with high strength and self-lubricating property is finally prepared; in the method, FT molecules are dispersed in the gel through hydrogen bond action, and are accumulated and self-assembled into a supermolecular network through pi-pi action, and sol-gel transformation can occur under the action of external force, so that the self-lubricating property of the hydrogel is realized; short-chain HPC is introduced into PVA to construct a porous structure for hydrogel, and after FT is converted into sol under external force, the enriched porous structure provides a large amount of space for the flow of FT-enabled sol, so that the self-lubricating characteristic of quick response is realized.

Description

Preparation method of high-strength self-lubricating polyvinyl alcohol hydrogel

Technical Field

The invention belongs to the field of functional polymer material tissue engineering materials, and particularly relates to a preparation method of a high-strength self-lubricating polyvinyl alcohol hydrogel.

Background

The human cartilage joint tissue is often subjected to friction tests, once abrasion occurs, the joint can be damaged, so that great pain can be brought to the human body, the human tissue structure is actually a hydrogel with a macromolecular cross-linked network structure consisting of smaller repeating units, and the synthetic hydrogel has high water content and is matched with the mechanical property of human soft tissue, so that the synthetic hydrogel can simulate a biological system to be used as the tissue structure. Polyvinyl alcohol (PVA) hydrogel is a two-phase three-dimensional network polymer material having both liquid and solid phases, is rich in a large amount of water in the network, has many excellent properties such as chemical stability, usability and molding cost, high elasticity and good biocompatibility, has been considered as a potential cartilage tissue substitute material having desirable characteristics and has attracted interest in many applications and medicine. Actually, the lubrication of cartilage is a dynamic self-lubricating process capable of releasing lubricating fluid according to different loads of various activities of human body, and the simple material composite technology and substrate surface treatment are difficult to meet the lubricating requirement caused by environmental complexity. Designing and preparing an intelligent lubricating material with a controllable lubricating mode system is a great challenge.

Disclosure of Invention

The invention provides a preparation method of polyvinyl alcohol hydrogel with high strength and self-lubrication, aiming at solving the problems that the existing hydrogel preparation process is complex, the material mechanical strength is low, and the self-lubrication characteristic capable of rapidly responding to environmental recognition is unavailable.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows:

a preparation method of polyvinyl alcohol hydrogel with high strength and self-lubrication comprises the following steps:

step 1), weighing HPC (hydroxypropyl cellulose) and adding the HPC into a mixed solution of deionized water and DMSO (dimethyl sulfoxide), and then pouring a liquid mixture into a three-neck flask and stirring at a constant speed for 10 minutes;

step 2) heating the mixture of step (1) to 70 ℃ by using a water bath kettle water bath, and further stirring until all hydroxypropyl cellulose is completely dissolved;

step 3) adding PVA (polyvinyl alcohol) into the step 2), heating the mixture to 90 ℃ again until all polyvinyl alcohol powder is dissolved, and then continuing heating and stirring for 3 hours;

step 4) subsequently dissolving FT (L-tryptophan) in batch portions in the mixture solution obtained in step 3) at 70 ℃ and then sonicating for 3 minutes, and then cooling to room temperature to form a HPC/PVA-FT solution;

step 5) pouring the formed HPC/PVA-FT solution into a prepared mould to cool to room temperature for 12 hours;

step 6) freezing the HPC/PVA-FT solution in a refrigerator at-20 ℃; freezing for 12 hours, then placing the mixture at room temperature and automatically thawing for 3 hours; after three freeze-thaw cycles, a solid HPC/PVA-FT hydrogel was obtained.

The PVA long chains are crosslinked through physical entanglement, and form multi-stage hydrogen bonds with the short chain HPC and FT, and the hydrogen bond network is tighter under the freezing and thawing action, so that the hydrogel with high strength and self-lubricating property is finally prepared.

The preparation method has the advantages that 1) a supermolecule FT with thixotropy is introduced, FT molecules are dispersed in gel through the action of hydrogen bonds, and are stacked and self-assembled into a supermolecule network through pi-pi action, and sol-gel transformation can occur under the action of external force, so that the self-lubricating property of hydrogel is realized; 2) short-chain HPC is introduced into PVA to construct a porous structure for hydrogel, and after FT is converted into sol under external force, the enriched porous structure provides a large amount of space for the flow of FT-enabled sol, so that the self-lubricating characteristic of quick response is realized.

Further, the mass fraction of the hydroxypropyl cellulose in the mixture in the step 1) is 2.4%; the volume ratio of the deionized water to the dimethyl sulfoxide is 10: 3.

Further, the mass fraction of polyvinyl alcohol in the mixture obtained in the step 3) is 13.5%.

Further, the adding amount of the L-tryptophan in the step 4) accounts for 0.0-0.6% of the total mass of the HPC/PVA-FT solution.

Further, the stirring process in step 3) for 3 hours is as follows: stirring at high speed for 2.5h, and then stirring at lower speed for 30 min. The purpose is to reduce bubbles. The high-speed stirring speed and the low-speed stirring speed are relative concepts, namely the stirring speed of the first 2.5 hours is larger than the stirring speed of the next 30 min.

The detection method of the prepared high-strength self-lubricating HPC/PVA-FT hydrogel comprises the following steps:

1) morphological observations of HPC/PVA-FT hydrogels:

the hydrogel is dried by a freeze dryer and then sampled for testing, the surface appearance of the sample is observed by an SU-1500 scanning electron microscope, and the accelerating voltage is 20 KV.

2) Mechanical testing of HPC/PVA-FT hydrogels:

the mechanical properties of the hydrogels were tested by a universal tester, shearing the HPC-PVA hydrogel to 8 cm x 1 cm x 0.5 cm, setting the test load of the extensometer at 100N, setting the extension speed at 100 mm min^-1. The mean was taken by three repeated measurements.

3) Friction Performance testing of HPC/PVA-FT hydrogels:

the hydrogel is formed into a cylinder with the diameter of 10cm and the thickness of 2cm, a reciprocating friction tester is adopted to test the friction performance, the set parameter is loading load 5N, the test time is 5min, the test sliding speed is 300mm/min, and the stroke length is 5 cm.

The HPC/PVA-FT hydrogel prepared by the method has an ultra-low friction coefficient (0.05), high mechanical strength (2.6 MPa) and self-lubricating property with quick response. The HPC/PVA-FT hydrogel prepared by the method has an ultra-low friction coefficient (0.05), high mechanical strength (2.6 MPa) and self-lubricating property with quick response.

In addition, the polyvinyl alcohol hydrogel prepared by the preparation method has excellent mechanical property and quick response self-lubricating property, and can be used as an artificial cartilage lubricating material and has potential application value in the field of human tissue engineering.

Compared with the prior art, the invention has the following beneficial effects:

according to the invention, a hydrogel with high strength and self-lubricating property is prepared, a porous structure is provided for the hydrogel by introducing HPC, and on the other hand, a hydrogen bond can be formed between hydroxyl on short-chain HPC and PVA, and the hydrogen bond can be used as a sacrificial bond and can effectively dissipate certain energy under the external stress of the hydrogel, so that high mechanical property is realized. On the other hand, FT molecules can be stacked and self-assembled into a supermolecular network through pi-pi action, when the hydrogel is not subjected to external stress, FT exists in a hydrogel network system in a supermolecular network structure, the mechanical property of the hydrogel is further enhanced, after the hydrogel is subjected to the external stress, FT undergoes gel-sol transformation and is rapidly transformed into flowable molecules from the supermolecular network, and the pore structure enriched by the hydrogel can rapidly flow to the surface of the hydrogel subjected to the stress through pores for lubrication.

The hydrogel with high strength and self-lubricating property prepared by the method can be applied to human cartilage tissue materials, and has wide application prospects in the field of tissue engineering.

Drawings

FIG. 1 is an SEM of an HPC/PVA-FT hydrogel, where a is an SEM of a neat PVA hydrogel, b is an SEM of example 1 after the introduction of HPC, and c is an SEM of the HPC/PVA-FT hydrogel prepared in example 3.

FIG. 2 is a mechanical property test chart of HPC/PVA-FT hydrogels, which are stress-strain plots of HPC/PVA-FT hydrogels at different FT contents for examples 1-4.

FIG. 3 is a graph of friction performance measurements for HPC/PVA-FT hydrogels, which are plots of friction coefficient versus time for HPC/PVA-FT hydrogels of examples 1-4 at different FT contents.

Detailed Description

The present invention is further illustrated by the following specific examples.

Example 1

A method for preparing cellular polyvinyl alcohol hydrogel with high strength comprises the following steps:

step 1) 30mL of deionized water was first measured in a 100mL graduated cylinder, and 9mL of DMSO (dimethyl sulfoxide) was measured in a 50mL graduated cylinder. The two liquids were mixed together, then 1g of HPC (hydroxypropyl cellulose) was added, and the liquid mixture was subsequently poured into a three-necked flask and stirred at constant speed for 10 minutes.

Step 2) the mixture was next heated to 70 ℃ using a water bath and further stirred until all HPC was completely dissolved.

Step 3) 6.4g of PVA was added and the mixture was heated again to 90 ℃ until all PVA (polyvinyl alcohol) powder was dissolved, and then heating and stirring were continued for 3 hours (stirring at high speed for 2.5h and then at lower speed for 30min in order to reduce air bubbles).

Step 4) the resulting HPC/PVA solution was then poured into a previously prepared mold (5 cm diameter and 0.5mm thickness) to cool to room temperature for 12 hours. At the same time, the cooling process eliminates the visible bubbles in the solution due to agitation.

Step 5) the HPC/PVA solution was frozen in a refrigerator at-20 ℃. After freezing for 12 hours, it was left at room temperature and thawed by itself for 3 hours. After three freeze-thaw cycles, a solid HPC/PVA hydrogel was obtained.

Example 2:

Step 4) the specified amount of 100mg of FT was then dissolved in the mixture solution at 70 ℃ and then sonicated for 3 minutes, which was then cooled to room temperature.

Step 5) the resulting HPC/PVA-FT solution was then poured into a previously prepared mold (5 cm diameter and 0.5mm thickness) to cool to room temperature for 12 hours. At the same time, the cooling process eliminates the visible bubbles in the solution due to agitation.

Step 6) the HPC/PVA-FT solution was frozen in a freezer at-20 ℃. After freezing for 12 hours, it was left at room temperature and thawed by itself for 3 hours. After three freeze-thaw cycles, a solid HPC/PVA-FT hydrogel was obtained.

Example 3:

Step 4) the specified amount of 200mg of FT was then dissolved in the mixture solution at 70 ℃ and then sonicated for 3 minutes, which was then cooled to room temperature.

Example 4:

Step 4) the specified amount of 300mg of FT was then dissolved in the mixture solution at 70 ℃ and then sonicated for 3 minutes, which was then cooled to room temperature.

Detection of HPC/PVA-FT hydrogel;

morphological Observation of HPC/PVA-FT hydrogels

The hydrogels of examples 1 to 4 were dried by a freeze dryer and sampled for testing, and the surface morphology of the samples was observed with a SU-1500 scanning electron microscope at an acceleration voltage of 20 KV. From the results, it can be seen (as shown in FIG. 1) that the SEM of the pristine PVA hydrogel (FIG. a) is relatively flat and does not show a distinct pore structure, whereas the hydrogel has an enriched and larger pore size pore structure after the addition of HPC (FIG. b). This indicates that the introduction of HPC provides a hydrogel with a large number of pore structures.

2) Mechanical property test of HPC/PVA-FT hydrogel

Mechanical Properties of the hydrogels were tested by a universal tester, shearing the hydrogels of examples 1-4 to 8 cm x 1 cm x 0.5 cm, respectively, setting the test load of the extensometer at 100N and the extension speed at 100 mm. min^-1. The mean was taken by three repeated measurements. It can be seen from the results (as shown in FIG. 2) that the mechanical properties of the hydrogel are significantly improved after FT is added, the stress reaches 2.6MPa at the maximum when the FT content is 0.4wt%, and the mechanical properties are significantly reduced when the FT content exceeds 0.4wt%, which is probably due to the fact that the formation of hydrogen bonding network between HPC and PVA is inhibited to some extent after the FT content is increased, thus resulting in a reduction in mechanical properties.

3) Friction Performance testing of HPC/PVA-FT hydrogels

The hydrogels of examples 1 to 4 were each formed into a cylindrical shape having a radius of 5cm and a height of 2cm, and friction performance was measured using a reciprocating friction tester with a set parameter of a load of 5N, a test time of 5min, a test sliding speed of 300mm/min, and a stroke length of 5 cm. As can be seen from the results (as shown in FIG. 3), the PVA hydrogel with FT added has a significantly improved frictional property compared with the hydrogel without FT, and the coefficient of friction COF is changed from 3.5 to 2.5. And the COF value is greatly reduced along with the increase of the FT content, and reaches 0.05 at the lowest when the FT content is 0.6 wt%. This is because as the FT content increases, the FT molecules that can flow into the interior of the hydrogel to lubricate the friction surface increase, and the friction coefficient greatly decreases.

Claims

1. A preparation method of polyvinyl alcohol hydrogel with high strength and self-lubrication is characterized by comprising the following steps:

step 1), weighing hydroxypropyl cellulose, adding the hydroxypropyl cellulose into a mixed solution of deionized water and dimethyl sulfoxide, and then pouring a liquid mixture into a three-neck flask to stir at a constant speed for 10 minutes;

step 2) heating the mixture of step 1) to 70 ℃ by using a water bath kettle water bath, and further stirring until all hydroxypropyl cellulose is completely dissolved;

step 3) adding polyvinyl alcohol into the step 2), heating the mixture to 90 ℃ again until all polyvinyl alcohol powder is dissolved, and then continuing heating and stirring for 3 hours;

step 4) subsequently dissolving L-tryptophan in a batch portion in the mixture solution obtained in step 3) at 70 ℃ and then sonicating for 3 minutes and then cooling to room temperature to form a HPC/PVA-FT solution;

2. The method for preparing a high-strength self-lubricating polyvinyl alcohol hydrogel according to claim 1, wherein the method comprises the following steps: the mass fraction of the hydroxypropyl cellulose in the mixture in the step 1) is 2.4 percent; the volume ratio of the deionized water to the dimethyl sulfoxide is 10: 3.

3. The method for preparing a high-strength self-lubricating polyvinyl alcohol hydrogel according to claim 1, wherein the mass fraction of polyvinyl alcohol in the mixture obtained in the step 3) is 13.5%.

4. The method for preparing a high-strength self-lubricating polyvinyl alcohol hydrogel according to claim 1, wherein the L-tryptophan added in step 4) accounts for 0.2 to 0.6 mass percent of the total weight of the HPC/PVA-FT solution.

5. The method for preparing a high-strength self-lubricating polyvinyl alcohol hydrogel according to claim 1, wherein the stirring in step 3) for 3 hours is performed by: stirring at high speed for 2.5h, and then stirring at lower speed for 30 min.

6. Use of the polyvinyl alcohol hydrogel prepared by the method according to claim 1 in the field of tissue engineering.

7. Use of the polyvinyl alcohol hydrogel prepared by the preparation method according to claim 1 in a human cartilage tissue material.