CN109568657B

CN109568657B - Use of injectable hydrogels for the preparation of vitreous substitutes

Info

Publication number: CN109568657B
Application number: CN201710909206.XA
Authority: CN
Inventors: 刘文广; 崔春燕
Original assignee: Tianjin University
Current assignee: Tianjin University
Priority date: 2017-09-29
Filing date: 2017-09-29
Publication date: 2021-06-18
Anticipated expiration: 2037-09-29
Also published as: CN109568657A

Abstract

The invention discloses application of injectable hydrogel in preparation of vitreous substitutes, wherein N-acryloyl glycinamide and hydroxyethyl acrylamide with very good biocompatibility are used as reactants, and the injectable hydrogel with very good biocompatibility is formed through free radical copolymerization. The gel bubble water has higher swelling characteristic, when the gel reaches the swelling balance in water, the water content of the gel is up to 98.5 percent, the gel is completely transparent, and after the temperature of the gel is raised, the gel can be injected and cured through a needle, and experiments prove that the injectable hydrogel can be used as a substitute of a vitreous body.

Description

Use of injectable hydrogels for the preparation of vitreous substitutes

Technical Field

The invention belongs to the field of biomedical materials, and particularly relates to an injectable hydrogel and a preparation method and application thereof.

Background

A hydrogel is a three-dimensional network of polymers with high water content. The hydrogel has good biocompatibility and other excellent properties, such as environmental responsiveness, antibacterial property, self-repairing property, super water absorbability and the like. The characteristics lead the hydrogel to have wide application prospect in the aspects of biomedicine, sensors, self-repairing materials, water retention and drought resistance and the like.

With the increase of age or some accidents, when the eyes of people are wounded, the affected parts are often removed by operation, wherein diseases such as vitreous opacity and cataract account for a large proportion, so the vitreous body removal operation is also necessary. However, vitrectomy regret severely affects vision and presents additional diseases such as retinal detachment, and finding a vitreous substitute is also a necessity for the best filling of the vitreous cavity. The fillers commonly used at present are silicone oil, air, perfluorocarbons and the like, but the substitutes often permeate, cannot be used in the vitreous cavity for a long time, and can cause diseases such as glaucoma, retinal hemorrhage and the like. It is therefore necessary to develop a hydrogel that is biocompatible and has properties similar to those of natural vitreous as a long-term replacement for vitreous.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide an injectable hydrogel and a preparation method thereof, wherein N-acryloyl glycinamide (NAGA) and hydroxyethyl acrylamide (HEAA) with very good biocompatibility are used as reaction raw materials, a free radical polymerization method is adopted for preparation, a gel network crosslinked by covalent bonds and hydrogen bonds is formed, and then the injectable hydrogel is prepared after water bubbles reach swelling balance.

The technical purpose of the invention is realized by the following technical scheme:

an injectable hydrogel is prepared by dispersing N-acryloyl glycinamide and hydroxyethyl acrylamide in a water phase as monomers, initiating carbon-carbon double bonds on the two monomers to carry out free radical polymerization by using an initiator to obtain the hydrogel, and carrying out swelling balance on the hydrogel in a phosphate buffer solution to obtain the injectable hydrogel, wherein the mass ratio of the N-acryloyl glycinamide to the hydroxyethyl acrylamide is (1-10): 1, the solid content is 5-30%.

And the mass ratio of N-acryloyl glycinamide to hydroxyethyl acrylamide is (5-10): 1, the solid content is 10-25%.

A preparation method of injectable hydrogel comprises the following steps: dispersing N-acryloyl glycinamide and hydroxyethyl acrylamide serving as monomers in a water phase, initiating carbon-carbon double bonds on the two monomers by an initiator to carry out free radical polymerization to obtain hydrogel, and carrying out swelling balance on the hydrogel in a phosphate buffer solution, wherein the mass ratio of the N-acryloyl glycinamide to the hydroxyethyl acrylamide is (1-10): 1, the solid content is 5-30%.

And the mass ratio of N-acryloyl glycinamide to hydroxyethyl acrylamide is (5-10): 1.

furthermore, the solids content is from 10 to 25%, i.e.the mass of the two monomers/(sum of mass of the two monomers and water). times.100%.

The pH of the phosphate buffer solution was 7 to 7.5.

And the water phase is deionized water or tap water.

Furthermore, the amount of initiator is from 1 to 3%, preferably from 2 to 3%, based on the sum of the masses of the two monomers.

Moreover, the free radical provided by the initiator is used for initiating the reaction of the NAGA monomer and the HEAA monomer. Wherein the initiator can be selected from thermal initiator under water phase condition commonly used in polymer polymerization field, such as Ammonium Persulfate (APS) and potassium persulfate (KPS), or photoinitiator, such as 2-hydroxy-2-methyl-1-phenyl-1-acetone (Irgacure 1173). If a thermal initiator is selected, it is necessary to first remove oxygen from the reaction system by using an inert gas (such as nitrogen, argon or helium) to avoid inhibition of polymerization, and then, depending on the activity and amount of the initiator, to heat the reaction system to a temperature above the initiation temperature of the initiator used and for a considerable time (such as 1 hour or more or longer (1 to 5 hours)) to promote the initiator to generate enough radicals for a long time to initiate the reaction system for continuous radical polymerization, thereby finally preparing the hydrogel of the present invention. If a photoinitiator is selected, the photoinitiator is 2-hydroxy-2-methyl-1-phenyl-1-propanone (Irgacure 1173). A transparent closed reaction container can be selected for initiating free radical polymerization under the condition of ultraviolet irradiation, and because the photoinitiation efficiency is higher than that of thermal initiation, when the irradiation time is adjusted according to the activity and the dosage of the selected initiator, the irradiation time can be shorter than the heating time of thermal initiation, such as 20 minutes or longer (30min-1h), and compared with the thermal initiation, the experimental time can be greatly reduced.

In the preparation scheme, after the reaction is finished, the copolymer is taken out of the reaction container, the monomer, the initiator, the cross-linking agent and the solvent which do not participate in the reaction are removed, and then the copolymer is soaked in water until the swelling balance is achieved (for example, the water is replaced every 12 hours after the copolymer is soaked for 7 days, so that the swelling balance is achieved).

The hydrogel of the invention is realized at 50-60 ℃, the transformation of gel sol, namely the gel is injectable at 50-60 ℃, namely the application of the hydrogel of the invention in preparing injectable materials. The prepared hydrogel can be injected after being heated in water bath (50-60 ℃), and the injection can reduce the risk and the trauma to patients when a replacement operation is carried out. The vitreous was removed from the rabbit eye before the gel was injected, and during the injection, the amount of gel injected was the same as the amount of vitreous removed. The wound that the syringe produced will be sewed up after carrying out the vitreous body injection to the rabbit to the eye of rabbit all will be dripped eyedrops every day, adverse reactions such as preventing to take place inflammation. The rabbits which are subjected to vitreous body replacement are cultured and observed for four months, and the rabbits are subjected to various eye examinations regularly during the observation period, so that the rabbits show good replacement performance.

The invention has simple preparation method, wide material source, strong practicability and simple operation process, avoids large-scale vitrectomy and is beneficial to wound healing.

Drawings

FIG. 1 is H of monomeric acryloyl glycinamide (NAGA) of the invention¹-NMR spectrum.

FIG. 2 is the H of monomer hydroxyethyl acrylamide (HEAA) of the present invention¹-NMR spectrum.

FIG. 3 is H of an injectable hydrogel prepared according to the invention¹-NMR spectrum.

Figure 4 is a graph of rheological testing of injectable hydrogels prepared according to the present invention.

Fig. 5 is a diagram of a B-ultrasonic examination of rabbit eyes after vitreous substitution with the injectable hydrogel of the present invention.

Fig. 6 is a photograph of fundus examination of rabbit eyes after vitreous substitution with the injectable hydrogel of the present invention.

Fig. 7 is a photograph of an angiographic examination of a rabbit eye after vitreous replacement with the injectable hydrogel of the present invention.

Fig. 8 is a schematic view showing the electrophysiological dark adaptation results of rabbits four months after a vitreous substitution surgery using the injectable hydrogel of the present invention (1).

Fig. 9 is a graph showing the results of electrophysiological dark adaptation in rabbits four months after a vitrectomy procedure using the injectable hydrogel of the present invention (2).

Detailed Description

The technical scheme of the invention is further illustrated by combining the specific examples.

In the examples, a monomeric acryloyl glycinamide with two amide groups was prepared according to the reference (Bousta M, Colombo P E, Lengelet S, et al. versatile UCST-based thermoresponsive hydrogels for co-regional maintained drive [ J ]. Journal of Controlled Release,2014,174:1-6) starting from glycinamide hydrochloride and acryloyl chloride, the chemical structure of which is shown below:

first, 6.3g of glycylamine hydrochloride, 6mL of deionized water, 33.6mL of 2mol/L potassium carbonate, and 18mL of diethyl ether were mixed in a 100mL three-necked flask and subjected to ice-bath. Then 5.7g of acryloyl chloride was mixed with 24mL of diethyl ether and slowly added dropwise to the three-necked flask, and the time for the addition of the compound was about 1 hour. After the addition, the reaction was carried out for 4 hours in an ice bath. After the reaction, the pH was adjusted to about 2 with 6mol/L hydrochloric acid solution, and the mixture was washed three times with diethyl ether to remove the organic phase. The pH was adjusted to neutral with sodium hydroxide and the solution was lyophilized. Washing the freeze-dried powder with a mixed solution of ethanol and methanol in a ratio of 4:1, filtering out undissolved residual substances, and performing rotary evaporation on the residual solution to obtain white powder, and drying in a vacuum drying oven to obtain the product. The prepared product is subjected to nuclear magnetic resonance characterization, as shown in figure 1, peaks of hydrogen on three carbons of a, b and c exist in the figure, and all peaks accord with the molecular structure of NAGA, so that the successful preparation of NAGA monomer is demonstrated. The raw material monomer hydroxyethyl acrylamide is subjected to nuclear magnetic resonance characterization, as shown in figure 2, peaks of hydrogen on four carbons of a, b, c and d can be seen to exist in the figure, and all the peaks accord with the molecular structure of the HEAA, which indicates that no impurity exists in the HEAA monomer.

0.083g NAGA was weighed into a 10mL centrifuge tube using a tray balance, and then 17uL of HEAA and 2uL of photoinitiator Irgacure 1173 (2-hydroxy-2-methyl-1-phenyl-1-propanone) were each drawn into the centrifuge tube using a pipette gun, using deionized water as the aqueous phase and mixed well. Sealing, and placing into an ultraviolet crosslinking instrument for ultraviolet irradiation for 40min (the central wavelength of the ultraviolet irradiation is 365 nm). The gel formed after the illumination was removed and placed in a clean 100mL beaker and soaked with 50mL of deionized water. The deionized water was changed every 1 hour. The prepared product is subjected to nuclear magnetic resonance characterization, as shown in figure 3, the peaks of double bonds on the NAGA and HEAA monomers are seen to disappear, which indicates that no double bond exists in the system, namely all double bonds participate in free radical polymerization, and a required polymer network is formed.

After the gel was immersed in deionized water for 3 days to reach equilibrium, the gel was taken out and placed in a 5mL syringe, heated in a water bath at 60 ℃ for 10min, and then the syringe was taken out and the gel was injected into a 2mL clean vial, and the fluidity of the gel after injection was observed.

The instrument used for the rheological testing of the gel was a DHR rheometer, model DHR-2. Class number 03052207A gel was scanned for temperature at which the strain of the fixing material was 5% and the frequency was 1 Hz. The temperature is set to be 30-60 degrees and the temperature is raised at a rate of 1 degree per minute. The storage modulus of the gel gradually decreases with increasing temperature until the storage modulus and the loss modulus intersect to reach the gel sol transition point, i.e., the gel can be injected at this temperature. Referring to fig. 4, the graph of the rheological test of the injectable hydrogel prepared in the example shows that the storage modulus and the loss modulus of the gel meet at 55 degrees celsius, which indicates that the gel is transformed into gel sol at 55 degrees, i.e., the gel is injectable at 55 degrees.

Soaking the gel with balanced swelling in water in alcohol for two days, changing alcohol once within 12 hours, and performing ultraviolet irradiation during the alcohol soaking process to sterilize the gel. The alcohol soaked gel was re-soaked in sterile PBS solution and the solution was changed every 5 hours until the gel reached swelling equilibrium again. The obtained sterilized gel was put into a sterilized syringe and heated in a water bath at 60 ℃. The rabbit to be operated is anesthetized with L-ambam in an amount of 0.5 mL/kg. The sterilized syringe is inserted into the vitreous cavity of the right eye of the rabbit to extract the vitreous body of the right eye of the rabbit, then gas-liquid exchange is carried out, and gel which is about ten minutes after water bath is injected from a wound generated by extracting the vitreous body through the syringe, and the amount of the extracted vitreous body is kept consistent with the amount of the injected gel. After injection, the wounds caused by the injector for the right eye of the rabbit are sutured by surgical suture lines, eye drops are added to the eyes for vitreous body replacement at regular time every day, cultivation and observation are carried out for four months, and various examinations are carried out on the eyes regularly, as shown in attached figures 5-9.

The B-ultrasonic examination of the rabbit eye shows that the vitreous cavity of the rabbit is completely transparent and clean, and has no inflammation, cell aggregation and retinal detachment. Indicating that the injected gel does not cause diseases such as vitreous opacity and the like. The fundus photo examination of the rabbit eye can clearly see the main blood vessels and the peripheral small blood vessels in the rabbit eyeball, directly shows that the injected hydrogel as a substitute of the vitreous body does not damage the internal and peripheral tissues of the eye, and indirectly shows that the rabbit vision is normal and is not affected by the operation. Angiographic examination of the rabbit eye further demonstrated that the interior of the rabbit eye was intact and had no ocular disease. The electrophysiological examination of the rabbit eye is most objective to show that the gel material prepared is a long-term substitute for the vitreous. Electrophysiological observations of the eye were mainly observed from the peak of the b peak. Fig. 8 is the result of dark adaptation of the electrophysiological examination performed on rabbits four months after the operation, in which the sensitivity of the rod cells of the rabbits to light is mainly observed, and it is seen from the figure that the b-peak values of the right eye and the normal left eye, which have been subjected to the vitreous body replacement, are substantially identical, indicating that the rod cells of the right eye of the rabbits are normal. Fig. 9 shows the results of electrophysiological photopic examination performed four months after surgery on rabbits, in which the sensitivity of cones of the eyes to light is observed, and it can be seen from the figure that b peaks of the right eye and the normal left eye after surgery are also almost identical, which indicates that cones of rabbits are also normal, i.e., the perception of light of the eyes after vitreous body replacement is not damaged, i.e., the prepared injectable hydrogel can be used as a substitute for vitreous body, and can be used for preparing vitreous body replacement.

The preparation of the hydrogel of the invention can be realized by adjusting the preparation process parameters according to the content of the invention, and the hydrogel shows the performances basically consistent with the examples. The invention has been described in an illustrative manner, and it is to be understood that any simple variations, modifications or other equivalent changes which can be made by one skilled in the art without departing from the spirit of the invention fall within the scope of the invention.

Claims

1. The application of the injectable hydrogel in preparing a vitreous substitute is characterized in that the injectable hydrogel takes N-acryloyl glycinamide and hydroxyethyl acrylamide as monomers to be dispersed in a water phase, an initiator is used for initiating carbon-carbon double bonds on the two monomers to carry out free radical polymerization to obtain the hydrogel, and the hydrogel is swelled and balanced in a phosphate buffer solution to obtain the injectable hydrogel, wherein the mass ratio of the N-acryloyl glycinamide to the hydroxyethyl acrylamide is (1-10): 1, the solid content is 5-30%, and the gel generates gel sol transformation at 50-60 ℃.

2. Use of an injectable hydrogel according to claim 1 for the preparation of a vitreous substitute, characterized in that the mass ratio between N-acryloyl glycinamide and hydroxyethyl acrylamide is (5-10): 1, the solid content is 10-25%.

3. Use of the injectable hydrogel of claim 1 for the preparation of a vitreous substitute, wherein the aqueous phase is selected from deionized water, or tap water; the pH of the phosphate buffer solution was 7-7.5.

4. Use of an injectable hydrogel according to claim 1 for the preparation of a vitreous substitute, characterized in that the amount of initiator is between 1 and 3% of the sum of the masses of the two monomers.

5. Use of an injectable hydrogel according to claim 4 for the preparation of a vitreous substitute, characterized in that the amount of initiator is comprised between 2 and 3% of the sum of the masses of the two monomers.

6. Use of the injectable hydrogel of claim 1 in the preparation of a vitreous substitute, wherein the injectable hydrogel is injected in the same amount as the vitreous removed in the preparation of the vitreous substitute.