A double-network pH-sensitive drug-releasing hydrogel and its preparation method and application

Abstract

The invention discloses a double-network pH-sensitive drug-releasing hydrogel and a preparation method thereof, which is applied to the carrier of intestinal drugs. The invention uses sodium alginate polyethylene glycol and a carboxyl-rich pH-sensitive monomer to form an interpenetrating network hydrogel for drug loading through polymerization and cross-linking reaction, and utilizes the hydrogel carboxyl protonation under low pH conditions to basically not release drugs, and the characteristics of carboxyl deprotonation release drugs at higher pH, thereby achieving the purpose of targeted drug release. And the present invention combines sodium alginate and polymethacrylic acid-co-polyethylene glycol to form an interpenetrating network structure inside the gel, which has excellent mechanical properties, prevents the sudden release caused by the rupture of the drug carrier, and controls the swelling of the drug carrier hydrogel at the same time, slows down the release of the drug, makes it targeted, achieves the purpose of directional treatment, and solves the problem that the existing carrier cannot efficiently and directional release drugs to the inflammatory site in the colon.

Description

Technical Field

[0001] The invention relates to the technical field of biomedical bionic material preparation, and more specifically to a preparation method and application of a double-network pH-sensitive drug-releasing hydrogel. Background Art

[0002] Ulcerative colitis is a disease whose pathogenic mechanism is still unclear. The lesions of this disease are located in the sigmoid colon and rectum, and can also extend to the descending colon and even the entire colon. The disease cycle is long and will recur. If it is not handled properly, it will be very dangerous. It may cause cancer or massive bleeding. Nowadays, with the rapid development of industrialization, people's pace of life is getting faster and faster. Eating habits have also changed greatly. As a result, the incidence of ulcerative colitis is getting higher and higher. And it is becoming younger. The current treatment methods include surgery, immunosuppressive therapy, and traditional drug therapy using aminosalicylic acid and steroids. However, due to the complex pathogenesis of ulcerative colitis, some of the above methods are expensive, some have poor universality or more serious side effects. Therefore, most of them are now treated with tablets or enemas. Sulfasalazine is the first-line drug for the treatment of ulcerative colitis so far. But the problem that comes with it is that the low bioavailability of traditional drug formulations can easily lead to drug resistance.

[0003] At present, colon targeted drug delivery systems have attracted widespread attention due to their ability to efficiently and directional release of drugs. As a three-dimensional hydrophilic network structure, hydrogels are favored because they have a structure very similar to human tissue, good biocompatibility and targeting. Often used as a carrier of drugs, hydrogels can achieve beneficial therapeutic effects by improving efficacy, reducing toxicity and required dosage. There are a large number of adsorption sites on the hydrogel that can provide attachment sites for drugs, so hydrogels are good drug carriers. The pH responsiveness of the hydrogel makes the hydrogel shrink under low pH conditions and the drug cannot be released, while under alkaline pH conditions, the hydrogel swells and the drug is slowly released from the hydrogel. Since the human intestine is a weakly alkaline environment, pH-sensitive hydrogels can achieve the purpose of intestinal targeted release. As disclosed in the preparation method of CN202110623275.0 pH-responsive carboxymethyl chitosan / sodium alginate hydrogel spheres, carboxymethyl chitosan and sodium alginate are cross-linked under the promotion of acid solution, which effectively reduces the release of protein in simulated gastric juice and releases after positioning to the intestine. However, ulcerative colitis occurs in the colon, and drug administration should not only not release the drug in the gastric juice, but also keep the drug in the colitis area after passing through the small intestinal fluid of the same environment, that is, the drug properties are still retained after staying in the small intestine for 3-8 hours. In addition, the mechanical properties of the drug-loaded hydrogel are an indispensable part of the drug-loaded gel. If the mechanical properties of the hydrogel are weak, the gel may be squeezed and ruptured in the stomach or small intestine, causing the premature release of the drug, thereby affecting the therapeutic effect of the drug on colitis. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing a double-network pH-sensitive drug-releasing hydrogel in view of the shortcomings that existing carriers cannot efficiently and directionally release drugs to inflammatory sites in the colon and that carriers are easily squeezed and released suddenly in the intestine.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A method for preparing a double-network pH-sensitive drug-releasing hydrogel, wherein the hydrogel is obtained by polymerization of polyethylene glycol, a pH-sensitive monomer, and sodium alginate, and the specific preparation steps include:

[0007] S1. Preparation of gel

[0008] Polyethylene glycol and sodium alginate are dissolved in an alkaline solution, a pH-sensitive monomer is added, and polymerization is carried out under the action of an initiator and a cross-linking agent to obtain a primary gel.

[0009] S2. Preparation of double network gel

[0010] The primary gel obtained in step S1 is placed in a salt solution for reaction to obtain a double network gel.

[0011] Furthermore, the alkaline solution is a sodium hydroxide solution, and the concentration of the solution is 0.1-0.3 mol / L.

[0012] Furthermore, the concentration of polyethylene glycol and sodium alginate in the alkaline solution is 0.01 g / mL.

[0013] Furthermore, the pH sensitive monomer includes one or more of acrylic acid, methacrylic acid, carboxymethyl chitosan, and modified cellulose.

[0014] Furthermore, the mass ratio of sodium alginate to polyethylene glycol is 3:1-9, preferably, the mass ratio of sodium alginate to polyethylene glycol is 1:3.

[0015] Furthermore, the mass ratio of the pH sensitive monomer to polyethylene glycol is 100:1-5.

[0016] Furthermore, the initiator is ammonium persulfate or potassium persulfate, and the concentration thereof is 0.1-1 mol%.

[0017] Furthermore, the cross-linking agent is divinylbenzene or N,N-methylenebisacrylamide, and the concentration thereof is 0.1-3 mol%.

[0018] Furthermore, the polymerization reaction temperature in step S1 is 50-80° C. and the reaction time is 1-3 h.

[0019] Furthermore, the salt solution in step S2 is calcium chloride solution, aluminum chloride solution or ferric chloride solution, and its concentration is 0.1 g / mL.

[0020] Furthermore, the reaction time of the primary gel in the salt solution in step S2 is 4-6 hours.

[0021] Furthermore, the solution described in step S3 contains a mass concentration of 3-10% of the mass drug, and the immersion time is 2-6 hours.

[0022] The double-network pH-sensitive drug-releasing hydrogel obtained according to the above method is used in the preparation of intestinal drug gel.

[0023] A method for preparing an intestinal drug-loaded gel comprises immersing the obtained double network gel in a solution containing an intestinal therapeutic drug, washing it, and drying it to obtain the drug-loaded gel.

[0024] Furthermore, the intestinal treatment drug is a drug for treating ulcerative colitis. Specifically, the drug is sulfasalazine.

[0025] Compared with the prior art, the beneficial effects are:

[0026] The present invention forms two interpenetrating network structures with opposite properties inside the gel by sodium alginate and polymethacrylic acid-co-polyethylene glycol, and the two network structures strengthen the internal electrostatic force in the form of a large number of positive and negative ion pairs, greatly improving the mechanical properties of the gel, and can well prevent the problem of sudden release caused by the rupture of the drug carrier. In addition, the present invention controls the swelling of the drug carrier hydrogel through the force of the hydrogel interpenetrating network, reduces and slows down the swelling of the gel, and thus delays the release of the drug.

[0027] The nitrogen-containing groups contained in the hydrogel of the present invention provide a large number of adsorption sites for drug molecules, and the pH sensitivity of methacrylic acid makes the hydrogel have good targeting. At low pH, the hydrogel is in a contracted state and basically does not release drugs, while in the alkaline environment of the intestine, the pH gel swells and slowly releases the drugs, so that it has the targeting of the colon and maintains the efficacy of the drugs for a long time, achieving the purpose of targeted treatment. The method of the present invention is simple to prepare, and the pH-sensitive double-network hydrogel has good biocompatibility, and the drug release rate is close to 100%, which can be used for the treatment of ulcerative colitis. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a comparison diagram of the double network pH sensitive gel prepared in Example 1 before and after swelling;

[0029] Figure 2 Schematic diagram of the preparation process and formation mechanism of the hydrogel of the present invention;

[0030] Figure 3 This is the in vitro drug release diagram of the carrier gel prepared in Example 1;

[0031] Figure 4 is a test diagram of the mechanical properties of the loaded gel prepared in Example 1;

[0032] Where a is p(MAA-co-PEG)SN hydrogel and SA / Ca 2+ / p(MAA-co-PEG)DN hydrogel mechanical properties comparison diagram; b and c are SA / Ca 2+ / p(MAA-co-PEG)DN hydrogel compression cycle diagram; d is the TGA test diagram of drug-loaded hydrogel and non-drug-loaded hydrogel;

[0033] Figure 5 This is the infrared absorption spectrum of the loaded gel prepared in Example 1;

[0034] Among them, a is a drug-loaded hydrogel, b is a non-drug-loaded hydrogel, c is sulfasalazine, d is methacrylic acid, e is sodium alginate, and f is polyethylene glycol;

[0035] Figure 6The XPS spectra of sulfasalazine, drug-loaded hydrogel and non-drug-loaded hydrogel;

[0036] Among them, a is the N1s spectrum of sulfasalazine, drug-loaded hydrogel and non-drug-loaded hydrogel, b is the C1s spectrum of sulfasalazine, drug-loaded hydrogel and non-drug-loaded hydrogel, c is the S 2p spectrum of sulfasalazine, drug-loaded hydrogel and non-drug-loaded hydrogel, d is the O 1s spectrum of sulfasalazine, drug-loaded hydrogel and non-drug-loaded hydrogel. DETAILED DESCRIPTION

[0037] The following further explains and illustrates with reference to the examples, but the specific examples do not limit the present invention in any form. Unless otherwise specified, the methods and equipment used in the examples are conventional methods and equipment in the art, and the raw materials used are conventional commercially available raw materials.

[0038] Example 1

[0039] A method for preparing a double-network pH-sensitive drug-releasing hydrogel, the specific preparation steps comprising:

[0040] S1. Preparation of gel

[0041] 0.01 g of polyethylene glycol and 0.03 g of sodium alginate were added to 4 g of 0.2 M NaOH solution to dissolve, and 1 g of refined methacrylic acid monomer was added to the above solution. 0.25 mol % of ammonium persulfate was added as an initiator, and 1.5 mol % of N,N-methylenebisacrylamide was added as a cross-linking agent. The reaction was carried out at 60° C. for 1 hour to complete free radical polymerization and obtain a primary gel.

[0042] S2. Preparation of double network gel

[0043] The primary gel obtained in step S1 was placed in 30 mL of a solution containing 3 g of calcium chloride and reacted for 5 hours to obtain a double network gel.

[0044] S3. Preparation of drug-loaded gel

[0045] The double network gel obtained in step S2 was immersed in a solution containing 5% sulfasalazine for 4 hours, the gel was rinsed with deionized water, and dried to obtain the drug-loaded gel.

[0046] Example 2

[0047] A method for preparing a double-network pH-sensitive drug-releasing hydrogel, the specific preparation steps comprising:

[0048] S1. Preparation of gel

[0049] 0.01 g of polyethylene glycol and 0.02 g of sodium alginate were added to 4 g of 0.2 M NaOH solution to dissolve, and then 1 g of refined methacrylic acid monomer was added to the above solution. 0.25 mol % of ammonium persulfate was added as an initiator, and 1.5 mol % of N,N-methylenebisacrylamide was added as a cross-linking agent. The reaction was carried out at 60° C. for 1 hour to complete free radical polymerization and obtain a primary gel.

[0050] S2. Preparation of double network gel

[0051] The primary gel obtained in step S1 was placed in 30 mL of a solution containing 3 g of calcium chloride and reacted for 5 hours to obtain a double network gel.

[0052] S3. Preparation of drug-loaded gel

[0053] The double network gel obtained in step S2 was immersed in a solution containing 5% sulfasalazine for 4 hours, the gel was rinsed with deionized water, and dried to obtain the drug-loaded gel.

[0054] Example 3

[0055] A method for preparing a double-network pH-sensitive drug-releasing hydrogel, the specific preparation steps comprising:

[0056] S1. Preparation of gel

[0057] 0.01 g of polyethylene glycol and 0.01 g of sodium alginate were added to 4 g of 0.2 M NaOH solution to dissolve, and 1 g of refined methacrylic acid monomer was added to the above solution. 0.25 mol % of ammonium persulfate was added as an initiator, and 1.5 mol % of N,N-methylenebisacrylamide was added as a cross-linking agent. The reaction was carried out at 60° C. for 1 hour to complete free radical polymerization and obtain a primary gel.

[0058] S2. Preparation of double network gel

[0059] The primary gel obtained in step S1 was placed in 30 mL of a solution containing 3 g of calcium chloride and reacted for 5 hours to obtain a double network gel.

[0060] S3. Preparation of drug-loaded gel

[0061] The double network gel obtained in step S2 was immersed in a solution containing 5% sulfasalazine for 4 hours, the gel was rinsed with deionized water, and dried to obtain the drug-loaded gel.

[0062] like Figure 1 As shown, the double network gel of the present invention has good swelling properties. Figure 2As shown, the present invention obtains a primary gel by polymerization reaction of sodium alginate, polyethylene glycol and a pH-sensitive monomer rich in carboxyl groups, and then cross-links the primary gel to form an interpenetrating network hydrogel for drug loading, and utilizes the protonation of carboxyl groups of the hydrogel under low pH conditions to cause gel shrinkage, thereby preventing the drug from diffusing out of the gel. At a higher pH, the deprotonation of the carboxyl groups of the double network gel of the present invention causes the gel to swell, and the drug slowly diffuses out of the gel, thereby achieving the purpose of targeted drug release.

[0063] Experimental Example 1

[0064] The hydrogels prepared in Examples 1-3 were subjected to drug loading detection. The specific detection steps were to dry the drug loaded hydrogels, weigh and grind them, add them into PBS buffer, and then measure their absorbance. The drug loading results are shown in Table 1 below:

[0065] Table 1

[0066] Drug loading rate (%) Example 1 2.35 Example 2 2.04 Example 3 1.57

[0067] Experimental Example 2

[0068] The drug-loaded gel prepared in Example 1 was placed in PBS buffer solutions with pH values ​​of 1.2 and 7.4 for drug release testing. 5 ml of the supernatant was taken at regular intervals and supplemented with an equal amount of PBS solution. The absorbance of the supernatant was measured at a wavelength of 359 nm using an ultraviolet spectrophotometer. The test results are shown in Table 2 and Figure 3 As shown:

[0069] Table 2

[0070]

[0071] As shown in the table above and Figure 3 As shown, the double network gel prepared by the present invention can achieve a drug release rate of nearly 100% under the environment of pH=7.2, and the drug release rate is about 30% under the condition of pH=1.2. Therefore, the double network hydrogel prepared by the present invention has pH-dependent drug release. Although the carrier gel of the present invention releases part of the drug in the early stage, it can still release most of the drug effect in 4-24 hours, and can stably and long-term release the drug to the colitis site.

[0072] Experimental Example 3

[0073] The mechanical properties and thermal stability of the double network hydrogel prepared in Example 1 and the single network hydrogel prepared in Comparative Example 1 were tested. Figure 4 As shown:

[0074] exist Figure 4 In a, SA / Ca 2+The stress of the p(MAA-co-PEG) double network hydrogel at 50% compressive stress is 2.4 MPa, while that of the p(MAA-co-PEG) single network hydrogel at 50% stress is only 0.2 MPa, indicating that the SA / Ca 2+ The mechanical properties of p(MAA-co-PEG)DN hydrogel were significantly higher than those of p(MAA-co-PEG)SN hydrogel, which could effectively avoid the sudden release of drugs in the hydrogel caused by gastrointestinal extrusion rupture.

[0075] exist Figure 4 b and Figure 4 In c, the mechanical stability of the double network hydrogel in the embodiment was tested using a continuous loading-unloading cycle method. After ten compression cycles, the peak stress of the double network hydrogel remained at 1.83Mpa, and the energy dissipation of the hydrogel was 15.95%. It can be seen that the hydrogel has good mechanical stability and is a stable drug carrier.

[0076] exist Figure 4 In d, the thermal stability of drug-loaded hydrogels and drug-free hydrogels was measured using TGA. The thermogravimetric curves of drug-loaded hydrogels and drug-free hydrogels almost overlapped, indicating that the effect of hydrogel drug loading on the thermal stability of hydrogels is negligible.

[0077] Experimental Example 4

[0078] The loaded gel prepared in Example 1 was subjected to infrared absorption spectrum detection, and the results were as follows: Figure 5 As shown in the figure, the Fourier transform infrared spectroscopy (FTIR) analysis of sulfapyridine shows that 1020cm -1 The peak at is -S=O peak. The hydrogel peak and monomer peak are at 3470, 3440, 1710, 1620, 1610 cm -1 The results of FTIR showed that the peak of the drug in the gel appeared at 1020 cm -1 This indicates that the original peak of the drug is not affected, an effective drug peak appears in the gel, and the hydrogel does not affect the therapeutic effect of the drug.

[0079] Experimental Example 5

[0080] The XPS of sulfasalazine, the drug-loaded hydrogel prepared in the example and the non-drug-loaded hydrogel were tested for N1s, C 1s, S 2p and O1s. Figure 6As shown in the spectrum, in the C1s spectrum of the drug-releasing hydrogel, the peak at 285.90 eV is considered to be the C atom connected to the N atom. In the S 2p spectrum, the peak of sulfasalazine at 167.13 eV is considered to be SN, and the peak at 168.34 eV is considered to be C-SOX. Comparing the high-resolution N1s of the drug-loaded hydrogel with the high-resolution N1s of the drug-loaded hydrogel, it can be seen that there is an increase of 0.18 eV at 401.89 eV and a decrease of 0.18 eV at 399.83 eV, while the binding energy of the high-resolution spectrum of the S 2p of the sulfasalazine drug-loaded hydrogel decreases by 0.88 eV and 0.87 eV at 167.13 eV and 168.34 eV, respectively, indicating that the -NH in the hydrogel is an active site and interacts with the drug. In other words, the nitrogen-containing groups in the hydrogel play a major role in drug loading. From the contrast changes of O1s high-resolution energy spectrum, it can be seen that oxygen-containing groups do not play a major role in drug loading. Therefore, the loading of sulfasalazine by drug-loaded hydrogel is attributed to the nitrogen-containing groups in the hydrogel.

[0081] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A method for preparing a double-network pH-sensitive drug-releasing intestinal drug-loaded gel, characterized in that: The specific preparation steps include: S1. Preparation of gel The polyethylene glycol and sodium alginate are dissolved in an alkaline solution, a pH-sensitive monomer is added, and polymerization is carried out under the action of an initiator and a cross-linking agent to obtain a primary gel; S2. Preparation of double network gel The primary gel obtained in step S1 is placed in a salt solution for reaction to obtain a double network gel; S3. Preparation of intestinal drug-loaded gel The double network gel is immersed in a solution containing sulfasalazine, washed, and dried to obtain a drug-loaded gel; The mass ratio of the sodium alginate to the polyethylene glycol is 3:1-3; the mass ratio of the pH sensitive monomer to the polyethylene glycol is 100:1-5.

2. The method for preparing the intestinal drug-loaded gel with double network pH-sensitive drug release according to claim 1, characterized in that: The pH sensitive monomer is one or more of acrylic acid, methacrylic acid, carboxymethyl chitosan, and modified cellulose.

3. The method for preparing the intestinal drug-loaded gel with double network pH-sensitive drug release according to claim 1, characterized in that: The initiator is ammonium persulfate or potassium persulfate, and the concentration of the initiator is 0.1-1 mol %; the crosslinking agent is divinylbenzene or N,N-methylenebisacrylamide, and the concentration of the crosslinking agent is 0.1-3 mol %.

4. The method for preparing the intestinal drug-loaded gel with double network pH-sensitive drug release according to claim 1, characterized in that: The polymerization reaction temperature in step S1 is 50-80°C and the reaction time is 1-3h; the salt solution in step S2 is one or more of calcium chloride solution, ferric chloride solution or aluminum chloride solution, and the reaction time is 4-6h.

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