CN109651623B - Method for improving adhesion performance of polyacrylamide hydrogel and obtained polyacrylamide hydrogel - Google Patents

Abstract

The invention provides a method for improving the adhesive property of polyacrylamide hydrogel and the obtained polyacrylamide hydrogel. The method comprises the following steps of (1) uniformly mixing a modified product of grafted dopamine of hyaluronic acid or a salt thereof and soluble tetraborate in deionized water to form a first cross-linked network; (2) adding acrylamide and a cross-linking agent, then adding an initiator and tetramethylethylenediamine under an ice bath condition, uniformly mixing, and polymerizing at 0-4 ℃ to obtain a polyacrylamide hydrogel, wherein in the step (1), the dopamine grafting rate of the modifier is 30-32%, and the mass ratio of the modifier to tetraborate is 5 (2-1); the mass ratio of the acrylamide added in the step (2) to the modifier in the step (1) is (18-20): 1, and the hyaluronate is potassium salt or sodium salt. The method can greatly improve the adhesion performance of the prepared polyacrylamide hydrogel.

Description

Method for improving adhesion performance of polyacrylamide hydrogel and obtained polyacrylamide hydrogel

Technical Field

The invention relates to a biomedical material, in particular to a method for improving the adhesion property of polyacrylamide hydrogel and the obtained polyacrylamide hydrogel.

Background

Self-repairing hydrogels are a class of hydrogel materials that rapidly self-repair a fracture interface and restore initial performance after a structure is damaged. Because the material has good self-repairing performance, the service life of the material can be prolonged, and the safety performance of the material can be improved, so that the material is widely applied to the fields of biosensing, bionic electronic skin, wearable electronic equipment and the like.

Most of the self-repairing hydrogels reported at present can be completed only by certain external stimulation, and lack certain adhesion performance, and the adhesion effect needs to be achieved by other means. Research has shown that the foot gland cells of marine mussels can secrete a kind of byssus with adhesive properties, which is rich in dihydroxyphenylalanine and lysine. When the adhesive protein is contacted with the matrix, the catechol group and lysine which play the adhesion role can have certain reaction with the matrix, so that the mussel mucus can realize the adhesion from metal to the surface of different materials such as organic matters and the like. Inspired by the unique adhesiveness of mussels, dopamine is chemically grafted onto segments of some macromolecules to make them adhesive to mussels, so that the preparation of hydrogels with adhesive properties is a hot spot for researchers to study. Chinese patent document CN108264611A discloses a polyacrylamide hydrogel, which forms an interpenetrating network with dopamine-grafted and modified sodium hyaluronate, and improves the adhesion performance of the obtained polyacrylamide hydrogel.

In the process of implementing the invention, the inventor finds that at least the following problems exist in the prior art: the adhesion properties of polyacrylamide hydrogels are to be further improved.

Disclosure of Invention

In view of the above, the present invention provides a method for improving the adhesion property of polyacrylamide hydrogel and the obtained polyacrylamide hydrogel.

Specifically, according to a first aspect of the present invention, the embodiment of the present invention provides a method for improving the adhesion performance of polyacrylamide hydrogel, comprising the following steps:

(1) uniformly mixing a modified substance of grafted dopamine of hyaluronic acid or salt thereof and soluble tetraborate in deionized water to form a first cross-linked network;

(2) adding acrylamide and a cross-linking agent, then adding an initiator and tetramethylethylenediamine under an ice bath condition, uniformly mixing, polymerizing at 0-4 ℃ to obtain polyacrylamide hydrogel,

wherein the content of the first and second substances,

in the step (1), the dopamine grafting rate of the modifier is 30-32%, and the mass ratio of the modifier to tetraborate is 5 (2-1); the mass ratio of the acrylamide added in the step (2) to the modifier in the step (1) is (18-20): 1, and the hyaluronate is potassium salt or sodium salt.

Preferably, the modified substance is obtained by grafting dopamine by an amidation reaction of hyaluronic acid or a salt thereof.

As the prior art, hyaluronic acid or a salt thereof with a low molecular weight is helpful for dopamine to modify the hyaluronic acid or the salt thereof, and the molecular weight of the hyaluronic acid or the salt thereof is preferably in the range of 10kDa to 1000kDa, and more preferably 10kDa to 100kDa (e.g., 20kDa, 40kDa, etc.).

Specifically, the modified product is obtained by the following method:

weighing 1g of hyaluronic acid or a salt thereof at room temperature, adding 100-120 mL of 1mol/L PBS buffer solution, stirring until the hyaluronic acid or the salt thereof is completely dissolved, adjusting the pH value of the solution to 4-6, sequentially adding 0.47-0.50 g of 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide and 0.28-0.30 g of N-hydroxysuccinimide as catalysts, fully stirring for dissolving, and introducing N₂Removing air in the three-neck flask for 25-30 min to prevent dopamine from being oxidized, adding 0.47-0.56 g of dopamine hydrochloride under an ice bath condition, fully stirring and dissolving for 10-12 h at 0-4 ℃, wherein the molar ratio of the dopamine hydrochloride, the 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide and the N-hydroxysuccinimide is (1-1.2): 1:1, and purifying to obtain the modified substance.

Further specifically, the specific method for purifying comprises:

and putting the reacted solution into a dialysis bag, dialyzing with deionized water with the pH value of 4-6 to remove unreacted raw materials and byproducts, and freeze-drying the solution in the dialysis bag to obtain the modified substance. The molecular weight cut-off of the dialysis bag can be chosen by the person skilled in the art as the case may be, for example 14 kDa.

Preferably, in the step (2), the crosslinking agent is N, N-methylene bisacrylamide, and the initiator is ammonium persulfate.

More preferably, in step (2), 0.6-1 mg of N, N-methylene bisacrylamide, 0.02-0.05 g of ammonium persulfate, and 5-10. mu.L of tetramethylethylenediamine are added per 0.5g of acrylamide.

More preferably, the specific operation steps of step (2) are as follows:

adding acrylamide and N, N-methylene bisacrylamide and stirring; adding ammonium persulfate under the ice bath condition, after stirring and dissolving, adding tetramethylethylenediamine, stirring in the ice bath until dissolving, immediately transferring the mixed solution into a mold, and then placing the mold in a refrigerator at 0-4 ℃ for polymerization to obtain the polyacrylamide hydrogel.

According to a second aspect of the present invention, there is provided a polyacrylamide hydrogel obtained by the above method.

The technical scheme provided by the embodiment of the invention has the beneficial effects that at least:

the embodiment of the invention provides a polyacrylamide hydrogel and a preparation method thereof, and the adhesion performance of the polyacrylamide hydrogel is greatly improved.

The polyacrylamide hydrogel is composed of a first network and a second network of Polyacrylamide (PAM) which are obtained by crosslinking Dopamine (DA) modified linear high molecular hyaluronic acid or salt thereof with tetraborate (Borax). The method ingeniously avoids the defect that phenolic hydroxyl on dopamine molecules is consumed in the traditional adhesive hydrogel preparation engineering, and can achieve the purposes of improving the adhesion and enhancing the tensile property. Meanwhile, a large number of boroester bonds are formed between the tetraborate and hydroxyl on the sodium hyaluronate, so that the adhesive hydrogel has good self-repairing performance. More importantly, the adhesion performance of the hydrogel is greatly improved by introducing the tetraborate. The self-repairing adhesive hydrogel prepared by the method can be applied to intelligent wearable equipment (sensors) and directly attached to the skin of a human body, so that interface layering and friction between the strain sensor and the skin can be avoided, and the method is favorable for detecting biological signals and improving the detection accuracy.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

Fig. 1 is a uv-vis spectrum of the dopamine-modified sodium hyaluronate obtained in example 1.

Fig. 2 is a nuclear magnetic resonance spectrum of dopamine modified sodium hyaluronate prepared in example 1.

FIG. 3 is a scanning electron micrograph of the polyacrylamide hydrogel obtained in example 1.

FIG. 4 is a bar graph showing the adhesion strength of the hydrogels obtained in example 1, comparative example 1 and comparative example 2 to silica glass.

FIG. 5 is a graph showing the tensile strengths of the hydrogels obtained in example 1, comparative example 1 and comparative example 2.

Detailed Description

In order to make the technical solutions and advantages of the present invention clearer, the following will describe embodiments of the present invention in further detail with reference to the accompanying drawings.

According to a first aspect of the present invention, embodiments of the present invention provide a method for improving the adhesion performance of polyacrylamide hydrogel, comprising the following steps:

(1) uniformly mixing a modified substance of grafted dopamine of hyaluronic acid or salt thereof and soluble tetraborate in deionized water to form a first cross-linked network;

(2) adding acrylamide and a cross-linking agent, then adding an initiator and tetramethylethylenediamine under an ice bath condition, uniformly mixing, polymerizing at 0-4 ℃ to obtain polyacrylamide hydrogel,

wherein the content of the first and second substances,

in the step (1), the dopamine grafting rate of the modifier is 30-32%, and the mass ratio of the modifier to tetraborate is 5 (2-1); the mass ratio of the acrylamide added in the step (2) to the modifier in the step (1) is (18-20): 1, and the hyaluronate is potassium salt or sodium salt.

Preferably, the modified substance is obtained by grafting dopamine by an amidation reaction of hyaluronic acid or a salt thereof.

As the prior art, hyaluronic acid or a salt thereof with a low molecular weight is helpful for dopamine to modify the hyaluronic acid or the salt thereof, and the molecular weight of the hyaluronic acid or the salt thereof is preferably in the range of 10kDa to 1000kDa, and more preferably 10kDa to 100kDa (e.g., 20kDa, 40kDa, etc.).

Specifically, the modified product is obtained by the following method:

weighing 1g of hyaluronic acid or a salt thereof at room temperature, adding 100-120 mL of 1mol/L PBS buffer solution, stirring until the hyaluronic acid or the salt thereof is completely dissolved, adjusting the pH value of the solution to 4-6, sequentially adding 0.47-0.50 g of 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide and 0.28-0.30 g of N-hydroxysuccinimide as catalysts, fully stirring for dissolving, and introducing N₂Removing air in the three-neck flask for 25-30 min to prevent dopamine from being oxidized, adding 0.47-0.56 g of dopamine hydrochloride under an ice bath condition, fully stirring and dissolving for 10-12 h at 0-4 ℃, wherein the molar ratio of the dopamine hydrochloride, the 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide and the N-hydroxysuccinimide is (1-1.2): 1:1, and purifying to obtain the modified substance.

Further specifically, the specific method for purifying comprises:

and putting the reacted solution into a dialysis bag, dialyzing with deionized water with the pH value of 4-6 to remove unreacted raw materials and byproducts, and freeze-drying the solution in the dialysis bag to obtain the modified substance. The molecular weight cut-off of the dialysis bag can be chosen by the person skilled in the art as the case may be, for example 14 kDa.

Preferably, in the step (2), the crosslinking agent is N, N-methylene bisacrylamide, and the initiator is ammonium persulfate. The amount of crosslinking agent, initiator, etc. can be determined experimentally by one skilled in the art according to the strength, etc. required to be obtained by the hydrogel.

More preferably, in step (2), 0.6-1 mg of N, N-methylene bisacrylamide, 0.02-0.05 g of ammonium persulfate, and 5-10. mu.L of tetramethylethylenediamine are added per 0.5g of acrylamide.

More preferably, the specific operation steps of step (2) are as follows:

adding acrylamide and N, N-methylene bisacrylamide and stirring; adding ammonium persulfate under an ice bath condition, after stirring and dissolving, adding tetramethylethylenediamine, stirring in an ice bath until dissolving, immediately transferring the mixed solution into a mold, and then placing the mold in a refrigerator at 0-4 ℃ for polymerization (the time is determined according to the requirements of the strength of the target polyacrylamide hydrogel and the like, for example, 12 hours), thus obtaining the polyacrylamide hydrogel.

According to a second aspect of the present invention, there is provided a polyacrylamide hydrogel obtained by the above method.

The technical scheme provided by the embodiment of the invention has the beneficial effects that at least:

the embodiment of the invention provides a polyacrylamide hydrogel and a preparation method thereof, and the adhesion performance of the polyacrylamide hydrogel is greatly improved.

In the following examples, the reagent information used is as follows.

Experimental medicine	Specification of	Manufacturer of the product
			Acrylamide	≥98.0	SINOPHARM CHEMICAL REAGENT Co.,Ltd.
1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride	98％	ALADDIN REAGENT (SHANGHAI) Co.,Ltd.
			N-hydroxysuccinimide	98％	ALADDIN REAGENT (SHANGHAI) Co.,Ltd.
Dopamine hydrochloride	>98％	Sigma-Aldrich
			Low molecular weight sodium hyaluronate	36kDa	BLOOMAGE FREDA BIOPHARM Co.,Ltd.
N' N-methylenebisacrylamide	96％	Acros Organics
			Tetramethyl ethylene diamine	99％	ALADDIN REAGENT (SHANGHAI) Co.,Ltd.
Ammonium persulfate	AR	SINOPHARM CHEMICAL REAGENT Co.,Ltd.
			Dipotassium hydrogen phosphate	AR	SINOPHARM CHEMICAL REAGENT Co.,Ltd.
Potassium dihydrogen phosphate	AR	SINOPHARM CHEMICAL REAGENT Co.,Ltd.
			Sodium chloride	AR	SINOPHARM CHEMICAL REAGENT Co.,Ltd.
Potassium chloride	AR	SINOPHARM CHEMICAL REAGENT Co.,Ltd.

The test and characterization method of the experimental results is as follows:

ultraviolet spectral characterization of HAC

Measuring the UV-Vis spectrum of the HAC by using a Nippon Shimadzu UV 2550 UV-visible spectrophotometer within the range of 200 nm-500 nm, wherein the test sample is 0.5mg/mL HAC aqueous solution,

nuclear magnetic resonance hydrogen spectrum of HAC (¹H-NMR)

The hydrogen spectrum of the HAC was determined using an AVANCE 400 nuclear magnetic resonance apparatus. Dissolving HAC in neon water (D2O), transferring to nuclear magnetic tube, and testing to obtain HAC¹H-NMR spectrum.

3. Micro-topography characterization of hydrogels

The internal structure of the hydrogel was observed using a cold field emission scanning electron microscope (SU 8010). Before testing, the hydrogel is freeze-dried, then quenched in liquid nitrogen, and subjected to gold spraying treatment on the section of the sample so as to observe the internal micro-morphology of the sample.

4. Hydrogel tensile and adhesion Performance testing

And testing the stretching and adhesion performance of the hydrogel by adopting a Shenzhen New Sansi universal stretching machine (CMT6503), wherein zero setting is carried out before testing, the loading rate is 50mm/min, and the gauge length is 10 mm. The hydrogel samples used for tensile property testing were 50mm long, 10mm wide and 5mm thick, with 3 replicate samples per set. The specification of the hydrogel samples for viscosity property test was 20mm in length, 20mm in width and 5mm in thickness, and 3 replicate samples were set for each set of samples.

Example 1

0.01mol/L PBS buffer solution (1L) is prepared

Adding 800mL of deionized water, 7.9g of sodium chloride, 0.2g of potassium chloride, 0.24g of monopotassium phosphate and 1.8g of dipotassium hydrogen phosphate into a 1L volumetric flask in sequence, magnetically stirring and dissolving at normal temperature, adjusting the pH of the solution to 7.2-7.4 by using 1mol/L HCl, adding distilled water to a constant volume of 1L to obtain 0.01mol/L PBS buffer solution, and storing in a 4 ℃ refrigerator after the solution is prepared.

Preparation of dopamine modified sodium Hyaluronate (HAC)

1. Weighing 1g of sodium hyaluronate at room temperature, putting the sodium hyaluronate into a three-neck flask, adding 100mL of 1mol/L PBS buffer solution and a proper magneton, stirring the solution until the sodium hyaluronate is completely dissolved, adjusting the pH of the solution to be 5, adding 0.476g of 1- (3-dimethylaminopropyl) -3-Ethylcarbodiimide (EDC) and 0.286g of N-hydroxysuccinimide (NHS) into the solution in sequence, fully stirring the solution for dissolution, introducing N230 min to remove air in the three-neck flask to prevent dopamine from being oxidized, adding 0.566g of dopamine hydrochloride (DA) under an ice bath condition, fully stirring the solution for dissolution, and reacting the solution at 4 ℃ for 12 hours, wherein the molar ratio of N (DA) to N EDC (N NHS) is 1.2:1: 1.

2. Putting the reacted solution into a dialysis bag with the molecular weight cutoff of 14kDa, dialyzing by using deionized water with pH of 4-6 to remove unreacted raw materials and byproducts, and freeze-drying the solution in the dialysis bag.

Fig. 1 is an ultraviolet-visible spectrum of the obtained dopamine modified sodium hyaluronate, wherein a strong ultraviolet absorption peak at 280nm is a benzene ring structure in dopamine, which proves that grafting is successful, and no extra peak exists under the condition that the wavelength exceeds 300nm, which indicates that the conjugated catechol of HAC is not oxidized.

Fig. 2 is a nuclear magnetic resonance spectrogram of the obtained dopamine-modified sodium hyaluronate, and the grafting rate of dopamine is calculated to be 32% through the nuclear magnetic resonance spectrogram.

Preparation of Polyacrylamide hydrogel

(1) First, 0.01g of Borax is added into 2.0ml of deionized water, and after the Borax is completely dissolved, 0.025g of HAC is added and the stirring is continued for 30min to form a first cross-linked network.

(2) Then, 0.5g of acrylamide and 0.0006g N of N-methylenebisacrylamide were added thereto and stirred. Adding 0.03g of ammonium persulfate under the ice bath condition, after stirring and dissolving, adding 10 mu L of tetramethylethylenediamine, stirring and dissolving in the ice bath, immediately sucking the mixed solution by using a disposable dropper, transferring the mixed solution into a mold, and then placing the mold in a refrigerator at 4 ℃ for polymerization for 12h to obtain the polyacrylamide hydrogel (PAM-HAC-Borax hydrogel for short). The scanning electron micrograph is shown in FIG. 3.

Comparative example 1

0.025mg HAC, 0.5g acrylamide, 0.0006g N N-methylene bisacrylamide were added to 2ml deionized water and dissolved by stirring. Adding 0.03g of ammonium persulfate under the ice bath condition, after stirring and dissolving, adding 10 mu L of tetramethylethylenediamine, stirring in ice bath until dissolving, immediately sucking the mixed solution by using a disposable dropper, transferring the mixed solution into a mold, and then placing the mold in a refrigerator at 4 ℃ for polymerization for 12 hours to obtain the polyacrylamide hydrogel.

Comparative example 2

0.5g of acrylamide and 0.0006g N g of N-methylene bisacrylamide are added into 2ml of deionized water and stirred to be dissolved. Adding 0.03g of ammonium persulfate under the ice bath condition, after stirring and dissolving, adding 10 mu L of tetramethylethylenediamine, stirring in ice bath until dissolving, immediately sucking the mixed solution by using a disposable dropper, transferring the mixed solution into a mold, and then placing the mold in a refrigerator at 4 ℃ for polymerization for 12 hours to obtain the polyacrylamide hydrogel.

As shown in FIGS. 4 and 5, the adhesion strength of PAM-HAC-Borax hydrogel to quartz glass is 38.07KPa, which is 2.92 times that of HAC-PAM hydrogel and 4.21 times that of PAM; the PAM-HAC-Borax hydrogel had a tensile strength of about 42KPa, which was about 1.6 times that of pure PAM (26KPa), and 2 times that of HAC-PAM (20KPa) hydrogel.

The PAM-HAC-Borax hydrogel contains a cross-linking network of HAC and Borax in a polyacrylamide network, so that the cross-linking of HAC and Borax and the hydrogen bonding between HAC and PAM can effectively dissipate energy in the stretching process, the hydrogel has good ductility, and the elongation at break can reach 2600%.

Although free catechol groups in the HAC-PAM hydrogel can impart good stretchability to the hydrogel, the catechol groups consume a certain amount of initiator, which is disadvantageous in polymerization of acrylamide, and the tensile strength (20KPa) of the hydrogel is reduced. And the catechol group on the HAC in the hydrogel added into the Borax can form a boron ester bond with the Borax, so that the consumption of the catechol group by an initiator can be avoided. Pure polyacrylamide network energy is not easy to dissipate, and the elongation at break is only 1200%.

The above description is only for facilitating the understanding of the technical solutions of the present invention by those skilled in the art, and is not intended to limit the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (9)

1. A method for improving the adhesion property of polyacrylamide hydrogel is characterized by comprising the following steps:

(1) uniformly mixing a modified substance of grafted dopamine of hyaluronic acid or salt thereof and soluble tetraborate in deionized water to form a first cross-linked network;

(2) adding acrylamide and a cross-linking agent, then adding an initiator and tetramethylethylenediamine under an ice bath condition, uniformly mixing, polymerizing at 0-4 ℃ to obtain polyacrylamide hydrogel,

wherein the content of the first and second substances,

in the step (1), the dopamine grafting rate of the modifier is 30-32%, and the mass ratio of the modifier to tetraborate is 5 (2-1); the mass ratio of the acrylamide added in the step (2) to the modifier in the step (1) is (18-20): 1, and the hyaluronate is potassium salt or sodium salt.

2. The method of claim 1, wherein the modifier is derived from hyaluronic acid or a salt thereof by grafting dopamine via amidation.

3. The method of claim 2, wherein the hyaluronic acid or salt thereof has a molecular weight of 10kDa to 1000 kDa.

4. The method of claim 2, wherein the modification is obtained by:

weighing 1g of hyaluronic acid or salt thereof at room temperature, adding 100-120 mL of 1mol/L PBS buffer solution, stirring until the hyaluronic acid or salt thereof is completely dissolved, adjusting the pH of the solution to 4-6, and sequentially adding 0.47-0.50 g of catalyst 1- (3-dimethylamino)Propyl) -3-ethylcarbodiimide and 0.28-0.30 g of N-hydroxysuccinimide, sufficiently stirring and dissolving, and introducing N₂Removing air in the three-neck flask for 25-30 min to prevent dopamine from being oxidized, adding 0.47-0.56 g of dopamine hydrochloride under an ice bath condition, fully stirring and dissolving for 10-12 h at 0-4 ℃, wherein the molar ratio of the dopamine hydrochloride, the 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide and the N-hydroxysuccinimide is (1-1.2): 1:1, and purifying to obtain the modified substance.

5. The method of claim 4, wherein the specific method of purification is:

and putting the reacted solution into a dialysis bag, dialyzing with deionized water with the pH value of 4-6 to remove unreacted raw materials and byproducts, and freeze-drying the solution in the dialysis bag to obtain the modified substance.

6. The method of any one of claims 1-5, wherein the crosslinking agent in step (2) is N, N-methylenebisacrylamide and the initiator is ammonium persulfate.

7. The method according to claim 6, wherein 0.6 to 1mg of N, N-methylenebisacrylamide, 0.02 to 0.05g of ammonium persulfate, and 5 to 10. mu.L of tetramethylethylenediamine are added per 0.5g of acrylamide in the step (2).

8. The method of claim 6, wherein the specific operation of step (2) is:

adding acrylamide and N, N-methylene bisacrylamide and stirring; adding ammonium persulfate under the ice bath condition, after stirring and dissolving, adding tetramethylethylenediamine, stirring in the ice bath until dissolving, immediately transferring the mixed solution into a mold, and then placing the mold in a refrigerator at 0-4 ℃ for polymerization to obtain the polyacrylamide hydrogel.

9. Polyacrylamide hydrogel obtainable by the process according to any one of claims 1 to 8.

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