CN100577219C - A kind of pectin/polyvinyl alcohol hydrogel material and preparation method thereof - Google Patents

Abstract

The invention discloses a pectin/polyvinyl alcohol hydrogel material and a preparation method thereof, which comprises the following components and weight percentages: 1-10% of pectin and 1-50% of polyvinyl alcohol. The preferred ratio is 3-7% of pectin, 20-30% of polyvinyl alcohol, and the balance is water. Its preparation method includes swelling, heating, freezing and thawing and dehydration. The pectin/polyvinyl alcohol hydrogel of the present invention has good biological safety, and the swelling performance and viscoelastic properties at the time of swelling balance are all suitable for the human body, and the pectin/polyvinyl alcohol hydrogel suitable for the human body can be produced Artificial nucleus pulposus prosthesis is widely used to treat patients with low back and leg pain caused by lumbar disc degeneration, replaces the physiological function of the nucleus pulposus, reduces postoperative complications such as vertebral body collapse and prosthesis subsidence, and improves the quality of life of patients after surgery . It can also be used as other scaffold materials to replace and repair cervical disc nucleus pulposus, cartilage and other tissues.

Description

A kind of pectin/polyvinyl alcohol hydrogel material and preparation method thereof

technical field

The invention relates to the technical field of medical bionic materials, in particular to a pectin/polyvinyl alcohol hydrogel material and a preparation method thereof.

Background technique

Both the classic lumbar discectomy and spinal fusion have changed the normal physiological shape and biomechanical environment of the lumbar spine and aggravated the degeneration of the intervertebral disc; in order to solve the above problems, non-fusion technology came into being, its main advantages are Theoretically, it reduces the degeneration of adjacent segments and avoids the formation of pseudarthrosis. Among them, artificial nucleus pulposus (Prosthetic Disc Nucleus, PDN) is considered to be an alternative to spinal fusion, and has become one of the effective methods for treating low back pain or lumbago and leg pain caused by lumbar disc degeneration. Since the first PDN nucleus pulposus replacement in Germany in 1996 (Ray CD. The PDN prosthetic disc-nucleus device. Eur Spine J. 2002S2: S137-42.), up to now there have been more than 4600 cases worldwide. The postoperative lumbar ODI (Oswestry Disability Index) score of the patient dropped from 52.2% to 13.4%, and the intervertebral space height increased by an average of 19.5%. The mid-term (4-year) follow-up found that the lumbar spine activity was significantly better than that of the simple nucleus pulposus removal, but the prosthesis Shen reached 49.2%, and cartilage endplate damage reached 60.0%.

At present, the hydrogel materials used for forming nucleus pulposus prosthesis are: polyvinyl alcohol (USP 5047055.09/10/1991, USP 6280475.08/28/2001), polyacrylamide, polyacrylonitrile, polyurethane blend (USP 4772287.09 /20/1988.). The materials used for in situ injection type nucleus pulposus prosthesis are: polyacrylamide polyethylene glycol acrylate, dimethyl acrylamide (need to add acyl phosphorus oxide as photoinitiator, CN 1561185A, 01/05/2005.), silicon Rubber (CNZL95243809.708/07/1996.), protein hydrogel (BioDisc company).

Polyvinyl alcohol hydrogel has the following characteristics: (1) Biocompatibility is closer to the human nucleus pulposus than other hydrophobic elastomers and metals. (2) High compressive strength, can withstand large loads and restore intervertebral height. (3) Water and water-soluble substances are permeable. (4) Can be rehydrated after dehydration without changing the properties of the material. However, the elastic modulus of the polyvinyl alcohol hydrogel used in the formation of the nucleus pulposus prosthesis is 3Mpa (Wu Jingping, Chen Tongyi, Chen Zhongwei, etc. Biomechanical properties of the polyvinyl alcohol hydrogel nucleus pulposus, Fudan Journal (Medical Edition), 2004, 31(1): 55-58) or above 4Mpa (USP 6280475.08/28/2001), which is significantly greater than the pressure in the intervertebral disc in the supine resting position of 0.1MPa, and also greater than 2.3MPa when bending over to bear weight (Willke HJ, Neef P, Caimi, M, et al. New in vivo measurements of pressures in the intervertebral disc in daily life. Spine, 1999, 24(8): 755～62.), resulting in excessive rigidity of the nucleus pulposus prosthesis , is one of the causes of cartilage endplate fracture and collapse, so it is necessary to reduce the elastic modulus of the hydrogel used.

Contents of the invention

The purpose of the present invention is to overcome the shortcomings of the hydrogel used in the existing nucleus pulposus, and provide a pectin/polyvinyl alcohol hydrogel material whose elastic modulus is suitable for replacing the nucleus pulposus of the lumbar intervertebral disc.

Another object of the present invention is to provide a preparation method of the above-mentioned pectin/polyvinyl alcohol hydrogel material.

In order to achieve the above object, the present invention, on the basis of polyvinyl alcohol hydrogel research, selects another kind of material that also has hydrophilic properties and is relatively soft to organically combine with polyvinyl alcohol to prepare pectin/polyvinyl alcohol hydrogel. gel material. The material selected in the present invention is pectin.

The pectin/polyvinyl alcohol hydrogel material of the present invention is composed of the following components and weight percentages: 1-10% of pectin and 1-50% of polyvinyl alcohol. The preferred ratio is 3-7% of pectin, 20-30% of polyvinyl alcohol, and the balance is water.

In nature, cactus has a rich mass diameter and stores a large amount of water. Among them, protopectin plays a major role, and its refined product is pectin. The molecular formula is [C ₆ H ₁₀ O ₇ ·H ₂ O]n, which is A linear polymer material whose hydrogel has swelling ability and colloidal properties. The pectin used in the present invention is preferably pharmaceutical grade pectin, which is gray or white powder, and the particle diameter is less than 315 microns; it is extracted from citrus peels, its galacturonic acid content is 60-85%, and the degree of esterification is 50-80%. 80%, the pH of 1% aqueous solution is 3.0~4.0.

Polyvinyl alcohol is a linear polymer, its main chain contains -CH-CH(OH)-groups, and its molecular formula is [CH ₂ =CHOH]n. Since it was first synthesized in 1924, polyvinyl alcohol is widely used as an adhesive, suspending agent, coating material, and ointment base because it is a water-soluble polymer, safe and non-toxic, and is included in the Pharmacopoeia as a pharmaceutical excipient. The preferred method of the invention is analytically pure polyvinyl alcohol, milky white or white granular, with a polymerization degree of 1700-4500, preferably 2400-2500; alcoholysis degree greater than 95%.

The preparation method of pectin/polyvinyl alcohol hydrogel material of the present invention, comprises the steps:

(1) Swelling: Dissolve pectin and polyvinyl alcohol in water, and swell naturally for 6-24 hours at 15-30°C;

Considering that pectin and polyvinyl alcohol are both linear polymers, it takes a long time for the steric hindrance between molecular chains and water molecules to enter the polymer molecules, so the swelling time is relatively long.

(2) Heating: Heating until the viscosity of the solution exceeds 40-50×10 ^-3 Pa.s, and removing the bubbles generated during the heating process;

Since pectin can dissolve in cold water at a low concentration, the concentration and degree of polymerization of polyvinyl alcohol affect its dissolution in water, so heating is required to promote the dissolution of pectin and polyvinyl alcohol in water. The heating method of the present invention is preferably: heating to 90-95° C. under normal pressure, heating to 140° C. in a high-pressure reactor, or microwave oscillation heating.

Among them, microwave oscillation heating with low power and intermittent microwave oscillation heating method is the best, the specific method is as follows: use pectin and polyvinyl alcohol aqueous solution with low power of 100-300 watts, heat for 25-45 minutes in total, and need to be interrupted 5 times Above, preferably 8-12 times; after this process, the viscosity of the mixed solution exceeds 40-50×10 ^-3 Pa.s.

The method for removing air bubbles is preferably standing at 60-80°C for 1-4 hours or rotating at a low speed.

(3) Freezing and thawing: the pectin/polyvinyl alcohol hydrogel heated to a molten state was frozen at -20°C for 12 to 36 hours, and completely thawed at room temperature. This was a "freezing and thawing". In order to form a physical hydrogen bond between molecules, form a network cross-linked structure, and make the pectin/polyvinyl alcohol hydrogel have the mechanical properties suitable for replacing the nucleus pulposus of the lumbar intervertebral disc, it is necessary to repeatedly freeze and thaw more than three times.

(4) Dehydration to obtain the pectin/polyvinyl alcohol hydrogel material. Fully hydrated hydrogels are bulky and unsuitable for implantation in the body. Because the hydrogel can be rehydrated after dehydration without changing the properties of the material, the dehydration method of the present invention is preferably: use absolute alcohol with a purity greater than 99.8%, dry under low temperature vacuum, or in a constant temperature drying oven. Among them, the method of anhydrous alcohol is the best dehydration method to make the pectin/polyvinyl alcohol hydrogel material uniformly dehydrated, the shape shrinks uniformly, and the shape does not change. The details are as follows: the volume of the anhydrous alcohol used and the prosthesis The ratio should be greater than 1, preferably 2 to 8 times the volume of the material; the absolute alcohol should be replaced every 8 to 48 hours, preferably 24 hours, until constant weight.

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

1. The biosafety of the pectin/polyvinyl alcohol hydrogel of the present invention is better, according to the evaluation of the national medical device biological evaluation standard (GB T 16886), its in vitro cytotoxicity is no more than 1 grade, and the implantation test in vivo has no Exudation, suppuration and other reactions are suitable for implantation in the body.

2. The swelling properties of the pectin/polyvinyl alcohol hydrogel of the present invention and the viscoelastic properties during swelling balance are all suitable for the human body. Promote the transport of water and water-soluble substances under load; can manufacture pectin/polyvinyl alcohol hydrogel artificial nucleus pulposus prosthesis suitable for the human body, which is widely used in the treatment of patients with low back and leg pain caused by lumbar disc degeneration, replacing the nucleus pulposus Improve the physiological function of the patient, reduce postoperative complications such as vertebral body collapse and prosthesis subsidence, and improve the quality of life of patients after surgery.

3. The pectin/polyvinyl alcohol hydrogel of the present invention can also be used as other scaffold materials because of its viscoelastic properties, water and water-soluble substances can penetrate, and can be used to replace and repair cervical intervertebral disc nucleus pulposus, cartilage and other tissues .

Description of drawings

Fig. 1 is the mass swelling rate and the volume swelling rate figure of pectin/polyvinyl alcohol hydrogel material;

Fig. 2 is the stress-strain curve figure when pectin/polyvinyl alcohol hydrogel swelling equilibrium;

Figure 3 is a diagram of the strain hysteresis during the pectin/polyvinyl alcohol hydrogel swelling loading-unloading process.

Fig. 4 is the creep diagram when pectin/polyvinyl alcohol hydrogel swelling is continuously loaded at 600N;

Figure 5 is a graph showing the change in mass of pectin/polyvinyl alcohol hydrogel swelling with time after continuous loading at 600N for 30 minutes.

Detailed ways

Example 1:

Weigh 6.0g of pectin and 1.2g of polyvinyl alcohol respectively, stir evenly, add 16.8g of double distilled water, the ratio of "pectin: polyvinyl alcohol: water" is "5%: 25%: 70%", a total of 6 servings. After natural swelling at 25°C for 12 hours, use low-power, intermittent microwave oscillation heating, use 120 watts to heat for 10 minutes, then stir and stop for 1 minute, continue to use 120 watts to heat for 10 minutes, stir and stop for 1 minute; after that, heat for 3 minutes and stop for 1 minute. A total of 7 times; select one of them to test its Ubbelohde viscosity value, which is 50×10 ^-3 Pa·s, and stop heating. Spin at 1500rpm for 5 minutes to remove air bubbles, then freeze at minus 20°C for 24 hours, thaw at room temperature for 6 hours, and repeat this 4 times.

Measure the volume of the pectin/polyvinyl alcohol hydrogel cylinder respectively, add 23ml～25ml (2 times the volume of the test piece) 99.8% dehydrated alcohol in the test tube, measure its quality every 24h at room temperature, and Replace the same volume of absolute alcohol once until the mass loss is less than 20 mg in 24 hours, and it is considered as dehydration to constant weight.

Example 2

Weigh 4.0g of pectin and 1.0g of polyvinyl alcohol, stir well, add 15.0g of double distilled water, the ratio of "pectin: polyvinyl alcohol: water" is "5%: 20%: 75%", a total of 6 servings. After natural swelling at 25°C for 12 hours, use low-power, intermittent microwave oscillation heating, use 100 watts to heat for 10 minutes, then stir and stop for 1 minute, continue to use 100 watts to heat for 10 minutes, stir and stop for 1 minute; after that, heat for 4 minutes and stop for 1 minute. A total of 6 times; select one of them to test its Ubbelohde viscosity value, which is 45×10 ^-3 Pa·s, and stop heating. Spin at 2000rpm for 5 minutes to remove air bubbles, then freeze at minus 20°C for 24 hours, and thaw at room temperature for 6 hours, repeat this process 3 times. The pectin/polyvinyl alcohol hydrogel was air-dried in a constant temperature drying oven at 50°C, and its mass was measured regularly until the mass loss within 24 hours was less than 20 mg, which was regarded as dehydration to constant weight.

Example 3

Weigh 3.5g of pectin and 0.5g of polyvinyl alcohol, stir well, add 8.5g of double distilled water, the ratio of "pectin: polyvinyl alcohol: water" is "4%: 28%: 68%", a total of 8 servings. After natural swelling at 25°C for 12 hours, heat it to 95°C in a normal pressure water bath, select one of them to test its Ubbelohde viscosity value, which is 55×10 ^-3 Pa·s, and stop heating. Stand in a water bath at 60°C for 2 hours to remove air bubbles, then freeze at minus 20°C for 36 hours, thaw at room temperature for 8 hours, and repeat this 4 times. Take the pectin/polyvinyl alcohol hydrogel material out of the test tube, place it at minus 80°C and 5 millitorr, and freeze-dry it in a vacuum. Measure its mass regularly until the mass loss in 24 hours is less than 20 mg, which is considered as dehydration to a constant temperature. Heavy.

Embodiment 4 Performance experiment

(1) General physical properties: the pectin/polyvinyl alcohol hydrogel material of the present invention has a glass transition temperature of 16.9°C to 41.3°C in the low temperature zone and 106.4°C to 130.6°C in the high temperature zone under the fully dehydrated state. 37°C can be regarded as a high elastic state, and the deformation is relatively stable.

(2) Biocompatibility: According to the method required by the national medical device biological evaluation standard (GBT 16886), conduct in vitro cytotoxicity and in vivo implantation tests. After the patent pectin/polyvinyl alcohol hydrogel of the present invention is sterilized, it is soaked in 37 ℃, 10% (V/V) calf serum DMEM culture solution for 24h, and the obtained extract is mixed with 10% (V/V) The liquid obtained by 50% (volume ratio) of DMEM culture fluid of calf serum is used as the culture fluid of mouse fibroblasts (NTCC L929). The proliferation rate was close to 100%, indicating less than grade 1 cytotoxicity. In addition, the patented pectin/polyvinyl alcohol hydrogel of the present invention was made into sheets of 3mmX3mmX(0.5～1)mm and strips of 10mmX3mmX3mm, and implanted into the subcutaneous and gluteal muscles of SD rats after disinfection. Survival normally and the wound healed by first intention. Samples were collected at 1 week and 4 weeks, and no abnormal exudate or suppuration was found in the local area. The above shows that the pectin/polyvinyl alcohol hydrogel of the present invention is suitable for implantation in the body.

(3) Swelling performance: After dehydrating the pectin/polyvinyl alcohol hydrogel of the present invention to a constant weight, a cylindrical specimen with a diameter of 17.0 mm and a height of 17.0 mm is made, with a mass of 4.3-4.5 g. Soak it in 37°C physiological saline, measure its mass and size regularly, until its mass change is less than 50mg within 24 hours, that is, reach the swelling equilibrium, to test its swelling performance. The mass swelling rate of pectin/polyvinyl alcohol hydrogel 3d is 140-160%, accounting for 70-80% of the swelling equilibrium; the volume swelling rate of 3d is 180-210%, accounting for 75-85% of the swelling equilibrium ,As shown in Figure 1.

(4) Viscoelastic properties: The hydrogel with swelling balance is made into a cylindrical specimen with a ratio of diameter to height of 1:1, soaked in physiological saline, placed on an MTS material tester at room temperature, and the loading rate is 5N /s, cyclically load 5 times (maximum load 500N), return to zero and start loading to 600N, last for 30min, test its creep performance, and collect time, load and displacement in real time. The elastic modulus of the pectin/polyvinyl alcohol hydrogel calculated by the stress-strain curve is 1.6-2.4MPa, as shown in Figure 2; the pectin/polyvinyl alcohol hydrogel can absorb 10-35% of the cyclic load energy %, to buffer the external stress, as shown in Figure 3; in Figure 3, the area surrounded by the curve divided by the area surrounded by the rising curve and the abscissa is the energy ratio absorbed by the hydrogel specimen. The creep of pectin/polyvinyl alcohol hydrogel began to tend to equilibrium after 10 min, as shown in Figure 4.

(5) Permeability of water and its water-soluble substances: After pectin/polyvinyl alcohol hydrogel is loaded at 600N for 30 minutes, it decreases by 3.0-10.0%, and after unloading for 2 hours, the mass can recover by 55-70%, reaching the loading level. 98.8-99.5% of the former mass, as shown in Figure 5.

Claims (8)

1. pectin/polyvinyl alcohol hydrogel material is characterized in that being made up of following component and percetage by weight:

Pectin 1～10%, polyvinyl alcohol 1～50%, surplus is a water;

The molecular formula of described pectin is [C ₆H ₁₀O ₇H ₂O] n, its galacturonic acid content is 60%～85%, esterification degree 50%～80%;

The molecular formula of described polyvinyl alcohol is [CH ₂=CHOH] n, the degree of polymerization is 1700～4500, alcoholysis degree is greater than 95%.

2. pectin/polyvinyl alcohol hydrogel material as claimed in claim 1 is characterized in that being made up of following component and percetage by weight:

Pectin 3～7%, polyvinyl alcohol 20～30%, surplus is a water.

3. the preparation method of the described pectin/polyvinyl alcohol hydrogel material of claim 1 is characterized in that may further comprise the steps:

(1) swelling: pectin and polyvinyl alcohol is soluble in water, and natural swelling is 6～24 hours under 15～30 ℃ of environment;

(2) heating: the viscosity that is heated to solution surpasses 40～50 * 10 ^-3Pas removes the bubble that produces in the heating process;

(3) freeze thawing: the pectin/polyvinyl alcohol hydrogel that will be heated into molten condition places-20 ℃ of freezing 12～36h, thaws fully under the room temperature;

(4) dehydration.

4. preparation method as claimed in claim 3, the mode that it is characterized in that the described heating of step (2) are to be heated under the normal pressure to be heated to 140 ℃ or microwave oscillation heating in 90～95 ℃, autoclave.

5. preparation method as claimed in claim 3 is characterized in that the method for the described removal bubble of step (2) adopts 60～80 ℃ to leave standstill 1～4h or low speed rotation removal.

6. preparation method as claimed in claim 3 is characterized in that the described dehydration method of described step (4) is: adopt purity greater than 99.8% anhydrous alcohol, or under the cryogenic vacuum, or thermostatic drying chamber is air-dry.

7. preparation method as claimed in claim 3 is characterized in that the described freeze thawing of described step (3) need repeat 3 times at least.

8. preparation method as claimed in claim 4 is characterized in that the method for described microwave oscillation heating is: with pectin and polyvinyl alcohol water solution, select 100～300 watts of low-power for use, heated altogether 20～45 minutes, be interrupted 8～12 times.

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