Temperature-sensitive nanogel, preparation method thereof, temperature-sensitive nanogel enema and medicine for treating ulcerative colitis

Abstract

The invention relates to the technical field of biomedical materials, in particular to temperature-sensitive nanogel, a preparation method of the temperature-sensitive nanogel, temperature-sensitive nanogel enema liquid and a medicine for treating ulcerative colitis. The temperature-sensitive nanogel is formed by carrying out free radical copolymerization reaction on N-vinyl-epsilon-caprolactam and methylacryloyl gelatin; wherein the temperature-sensitive nanogel can be converted from a sol state to a hydrogel state along with temperature change, and the critical temperature of phase conversion is 33-37 DEG C. The temperature-sensitive nanogel is prepared by adjusting the ratio of NVCL to GelMA by adopting a free radical polymerization reaction method, the mechanical strength and mucous membrane adhesion of the gel are enhanced by introducing GelMA, the residence time of the medicine in local rectum is prolonged, excellent biocompatibility and controllable degradability are obtained, and the preparation method is suitable for industrial production. The tissue stimulation can be reduced; and the sustained release of the medicine is supported.

Description

Technical Field

[0001] The present invention relates to the technical field of biomedical materials, and specifically relates to thermosensitive nanogels, a preparation method thereof, a thermosensitive nanogel enema, and a therapeutic drug for ulcerative colitis. Background Art

[0002] Ulcerative colitis (UC) is a chronic and recurrent inflammatory bowel disease characterized by inflammation and ulcers in the mucosa of the colon and rectum. In recent years, its overall incidence and prevalence have been on the rise, and it now affects people of all age groups, posing a major challenge to public health. Drugs are the cornerstone of UC treatment, and a stratified treatment strategy is adopted according to the different degrees of disease activity. 5-Aminosalicylic acid (5-ASA), also known as mesalazine, has become the first-choice drug for the treatment of ulcerative colitis (UC) since the 1980s due to its excellent safety, efficacy, and tolerance. It is still the first-line drug for inducing remission of mild to moderate active UC and preventing the recurrence of disease activity in quiescent UC.

[0003] Currently, 5-ASA oral dosage forms (capsules, tablets, granules) and topical dosage forms (suppositories, foams, enemas) have emerged on the market. However, they still have limitations. Oral administration is easily affected by the complex physiological environment of the gastrointestinal tract, which may lead to unreliable delivery of the drug to the colon. While topical administration can directly deliver the drug to the inflamed site of the colon, its effect is limited by poor patient compliance and insufficient drug retention. For one type of topical dosage form - enema, which is a flowing suspension liquid, usually needs to be used daily, requires maintaining a fixed position during use, and needs to be retained in the intestine for at least half an hour to achieve the best effect. However, due to its free flow and insufficient adhesiveness, combined with the urgency of feces in UC patients, there are problems such as easy leakage after enema and limited retention time at the lesion site, which greatly reduce patient compliance and the therapeutic effect is difficult to guarantee. Therefore, developing a 5-ASA enema with enhanced adhesiveness and long retention time in the intestine is crucial for improving the clinical treatment effect and patient compliance. Summary of the Invention

[0004] The present invention is made to solve the above problems, and aims to provide a thermosensitive nanogel enema for delivering 5-aminosalicylic acid, a preparation method thereof, and an application.

[0005] In the first aspect of the present invention, a thermosensitive nanogel is provided, which is characterized in that the thermosensitive nanogel is formed by free radical copolymerization of N-vinyl-ε-caprolactam and methacrylated gelatin; wherein, the thermosensitive nanogel can be phase-transformed from a sol state to a hydrogel state with temperature change, and the critical phase transition temperature is 33°C to 37°C.

[0006] To solve the above problems, the present invention attempts to design a thermosensitive gel as a drug delivery matrix. Utilizing the unique temperature-responsive sol-gel transition of the thermosensitive gel, i.e., it is liquid at room temperature and rapidly transforms into a gel state at body temperature, which not only facilitates injection and operation, is easy to distribute evenly, but also can focus local drug exposure and serve as a drug release depot to extend the drug treatment time. In recent years, some studies have focused on selecting different thermosensitive materials such as poloxamer, N-isopropylacrylamide, etc. for preparing thermosensitive gels applied to different scenarios.

[0007] However, although the gelling temperature of poly(N-isopropylacrylamide) (PNIPAAM) is close to physiological temperature, due to its non-biodegradability itself and the compounds generated during hydrolysis having known neurotoxicity, its further application in biomedicine is limited. While the thermosensitive gel derived from poloxamer has good drug loading capacity, its drug release rate is relatively slow and its response to temperature is not sensitive enough.

[0008] Since the poly(N-vinylcaprolactam)-based gel (PNVCL) has a lower critical solution temperature close to physiological temperature, it can rapidly respond to the body temperature and undergo a sol-to-gel transition. At the same time, it has good biodegradability, biocompatibility and chemical stability, and is convenient to introduce various functional groups through chemical modification to achieve multifunctional applications, etc. Therefore, the present invention uses N-vinyl-ε-caprolactam as the main raw material of the thermosensitive nanogel and designs it on this basis to facilitate drug loading.

[0009] The thermosensitive nanogel designed by the present invention is formed by free radical copolymerization of N-vinyl-ε-caprolactam (NVCL) and methacrylated gelatin (GelMA). Compared with ordinary poly(N-vinylcaprolactam) (PNVCL), it has significant advantages in terms of being a rectal drug delivery carrier. First, the thermosensitivity of the copolymer gel can be optimized by adjusting the ratio of NVCL to GelMA, enabling it to more stably undergo a sol-gel transition at rectal temperature (about 37 °C) to achieve intelligent drug release. Second, the introduction of GelMA enhances the mechanical strength and mucosal adhesiveness of the gel, prolongs the retention time of the drug in the rectal region, and at the same time GelMA has excellent biocompatibility and controllable degradability, which can reduce tissue irritation and support the sustained release of the drug. In addition, the porous structure and hydrophilic groups of GelMA improve the drug loading capacity, while the thermosensitivity of NVCL avoids the burst release effect and makes the drug release more controllable. Therefore, the thermosensitive nanogel designed by the present invention combines multiple advantages such as thermosensitivity, biocompatibility, mechanical properties and drug controlled release, and is an efficient and safe rectal drug delivery carrier.

[0010] Furthermore, the thermosensitive nanogel designed by the present invention forms a hydrogel with a three-dimensional network structure at human physiological temperature. Therefore, it can effectively load 5-aminosalicylic acid, mediate drug sustained release, extend the treatment time, and is expected to reduce the number of drug administrations for patients. When used for local intestinal administration, it can form a stable biophysical barrier in the intestine to more effectively block the further invasion of pathogenic microorganisms into the inflamed area.

[0011] In some embodiments, the mass ratio of N-vinyl-ε-caprolactam to methacrylated gelatin is 1:(0.01 - 0.1).

[0012] In the examples, the thermosensitive nanogel designed by the present invention is formed by free radical copolymerization of N-vinyl-ε-caprolactam and methacrylated gelatin. Among them, methacrylated gelatin serves as the backbone of the crosslinked network, directly affecting the mechanical strength of the gel and the formation of the porous structure, while N-vinyl-ε-caprolactam serves as the thermosensitive monomer, and its proportion affects the lower critical solution temperature of the gel. The present invention controls the mass ratio of the two to balance the mechanical properties and thermosensitivity of the gel. On the one hand, the addition amount of methacrylated gelatin is controlled to avoid insufficient crosslinking due to insufficient addition of methacrylated gelatin, resulting in a loose gel structure; or an excessive addition amount that inhibits the mobility of molecular chains and reduces the thermosensitive response. On the other hand, by controlling the addition amount of N-vinyl-ε-caprolactam, the lower critical solution temperature is controlled to make the lower critical solution temperature close to the human body temperature, realizing intelligent response in the rectal environment.

[0013] In a second aspect, a method for preparing a thermosensitive nanogel is provided, which is characterized by including the following steps: Under the protection of an inert gas, into a mixture of N-vinyl-ε-caprolactam, disodium ethylenediaminetetraacetate, and sodium formate, methacrylated gelatin and an initiator are added, mixed, and heated to undergo a free radical copolymerization reaction to obtain a reaction product, and the reaction product is purified to obtain the thermosensitive nanogel.

[0014] In some embodiments, the mass ratio of N-vinyl-ε-caprolactam, disodium ethylenediaminetetraacetate, and sodium formate is 1:(0.001 - 0.005):(0.005 - 0.01).

[0015] In some embodiments, the methacrylated gelatin is added after being preheated in solution form. The concentration of the methacrylated gelatin solution is (10 - 15)% w / v. The preheating treatment of the methacrylated gelatin solution is: heating the methacrylated gelatin solution in a water bath at 40 - 50 °C for 1 - 2 h.

[0016] In the examples, by preheating the methacrylated gelatin solution, the GelMA molecular chains are promoted to stretch, ensuring uniform dispersion, increasing solubility, and removing air bubbles in the solution to reduce structural defects in the subsequent polymerization reaction.

[0017] In some examples, the reaction temperature is 60 - 70 °C and the reaction time is 3 - 5 h.

[0018] In the examples, the polymerization reaction temperature is controlled at 60 - 70 °C, slightly higher than the decomposition temperature of azobisisobutyramidine hydrochloride (about 50 °C), to ensure that the initiator decomposes sufficiently to generate free radicals, while avoiding side reactions (such as chain breakage) caused by too high a temperature. At the same time, the reaction time is controlled at 3 - 5 h: to ensure that the monomers are fully polymerized to form a stable crosslinked network, avoiding incomplete reaction due to too short a time or overcrosslinking caused by too long a time, and reducing the thermosensitivity.

[0019] Furthermore, the reaction product is purified by dialysis treatment to remove unreacted monomers, initiator fragments, and small molecule impurities, to avoid the influence of residual impurities on the biocompatibility and drug release behavior of the gel.

[0020] In some examples, the initiator is azobisisobutyramidine hydrochloride, and the mass ratio of azobisisobutyramidine hydrochloride to N - vinyl - ε - caprolactam is (0.005 - 0.01):1.

[0021] In the examples, azobisisobutyramidine hydrochloride is used as the initiator, and the addition amount is controlled to balance the reaction rate and the product homogeneity.

[0022] In the third aspect, a thermosensitive nanogel enema solution for delivering 5 - aminosalicylic acid is provided, which is characterized in that the thermosensitive nanogel described in the first aspect is used as the delivery matrix.

[0023] In some examples, after ball - milling 5 - aminosalicylic acid and mixing it with a thermosensitive nanogel solution with a concentration of 5 - 15% w / v and stirring for 5 - 24 h, the thermosensitive nanogel enema solution is obtained.

[0024] Compared with the currently commercially available 5 - aminosalicylic acid enema solution, in the present invention, 5 - aminosalicylic acid is fully ball - milled and then dispersed in the nanogel solution, so that its dispersion stability in the nanogel solution is good. At the same time, the mass of the thermosensitive nanogel in the enema solution is controlled to ensure good drug sustained - release stability of the thermosensitive nanogel.

[0025] In the fourth aspect, a therapeutic drug for ulcerative colitis is provided, which is characterized in that the therapeutic drug includes the thermosensitive nanogel enema solution described in any item of the third aspect, and the thermosensitive nanogel enema solution changes from the sol state to the hydrogel state in the colon.

[0026] When the thermosensitive nanogel prepared by the present invention is in the hydrogel state, it has good adhesion to biological tissues, is not easy to leak during enema use, and can reduce the requirement for the patient to maintain a specific position for a long time.

[0027] By implementing the above technical solutions, the present invention has the following beneficial effects:

[0028] The thermosensitive gel of the present invention is temperature-responsive and can undergo a phase change near body temperature (such as 33°C to 37°C). Without the need for additional cross-linking agents, it is a freely flowing liquid at room temperature. When injected into the colon in liquid form, it can transform from a liquid state to a gel state in the human body, accurately release drugs at the inflammatory site, trigger drug release through temperature changes, have good controllability and predictability, and the drug is evenly distributed and has good spreading properties. At the same time, since it is in a liquid state at room temperature, it is convenient to administer drugs through enema or rectal administration, and the operation is relatively simple.

[0029] The hydrogel formed by the sol-gel transition of the thermosensitive nanogel prepared by the present invention has uniform and smooth micron-sized pores, can effectively encapsulate 5-aminosalicylic acid, play a drug sustained-release role, and has a simple preparation process, controllable process, and convenient operation.

[0030] The thermosensitive nanogel prepared by the present invention by using the free radical polymerization reaction method and adjusting the ratio of NVCL to GelMA enhances the mechanical strength and mucosal adhesiveness of the gel by introducing GelMA, prolongs the residence time of the drug in the rectum locally, and obtains excellent biocompatibility and controllable degradability, which can reduce tissue irritation and support the sustained release of drugs. At the same time, due to its good adhesion performance and mechanical properties, it can also cope with the irregular peristalsis and fecal urgency of the intestines of UC patients. Description of the Drawings

[0031] Figure 1 Characterization of the nuclear magnetic resonance hydrogen spectrum of the P(NVCL-co-GelMA) thermosensitive nanogel prepared in Example 1;

[0032] Figure 2 Comparison of viscosity measurement data of the P(NVCL-co-GelMA) thermosensitive nanogel solution in Example 2, the commercially available Salof enema solution, and the 5-ASA-10% thermosensitive nanogel solution in Example 6;

[0033] Figure 3 Vial tilt test and rheological data of the P(NVCL-co-GelMA) thermosensitive nanogel and the formed hydrogel in Example 3;

[0034] Figure 4 Transmission electron microscope morphology photos of the P(NVCL-co-GelMA) thermosensitive nanogel in Example 4 and scanning electron microscope morphology photos of the formed hydrogel;

[0035] Figure 5 Schematic diagram of in vitro adhesion and test results of the hydrogel formed by the P(NVCL-co-GelMA) thermosensitive nanogel in Example 5;

[0036] Figure 6 In vitro cumulative release rate of the drug of the hydrogel formed by the 5-ASA-loaded thermosensitive nanogel in Example 6;

[0037] Figure 7 Therapeutic effect of the hydrogel formed by the 5-ASA-loaded thermosensitive nanogel in Example 7 on rats with ulcerative colitis. Detailed implementation manners

[0038] In order to make the technical means, creative features, achieved purposes and functions of the present invention easy to understand, the present invention will be specifically described below in conjunction with embodiments and drawings.

[0039] Example 1

[0040] Preparation and characterization of P(NVCL-co-GelMA) thermosensitive nanogel: First, 0.4 g of GelMA was added to 4 mL of deionized water, and the mixture was stirred in a water bath at 50 °C for 1 h until completely dissolved to obtain a GelMA solution. Then, 0.4 g of 2,2'-azobis(2-methylpropionamidine) dihydrochloride was dissolved in 5 mL of deionized water to obtain a 2,2'-azobis(2-methylpropionamidine) dihydrochloride solution. Next, 40 g of NVCL, 0.04 g of disodium ethylenediaminetetraacetate, and 0.2 g of sodium formate were added to a flask containing 600 mL of deionized water and dissolved with an ultrasonic disperser. Subsequently, a nitrogen protection reaction system was set up, the temperature was set to 65 °C, and the mixture was stirred at a mechanical rate of 250 r / min. When the temperature rose to 50 °C, the GelMA solution was quickly added, and when the temperature reached 60 °C, the 2,2'-azobis(2-methylpropionamidine) dihydrochloride solution was slowly dropped in. The reaction continued for 4 hours, the supernatant was removed, the precipitate was dissolved in deionized water and loaded into a dialysis bag (cut-off molecular weight of 3500), and dialyzed with a large amount of deionized water for 5 days. After freeze-drying for 2 days, a white solid was obtained, which was the P(NVCL-co-GelMA) thermosensitive nanogel. The structure was characterized by a nuclear magnetic resonance hydrogen spectrometer, and the results were as Figure 1 shown.

[0041] Example 2

[0042] Viscosity measurement of P(NVCL-co-GelMA) thermosensitive nanogels: The freeze-dried thermosensitive nanogels were added with appropriate deionized water to prepare uniform solutions with different concentrations, which were 7 wt%, 10 wt%, and 13 wt% respectively. The viscosities of the thermosensitive nanogel solutions with different concentrations were measured using a rotational viscometer, and the commercially available Salofalk enema was used as a control. Each sample was measured 3 times and the average value was taken. The results are as Figure 2 shown.

[0043] Example 3

[0044] Sol-gel transition of P(NVCL-co-GelMA) thermosensitive nanogels and rheological behavior test of hydrogels:

[0045] First, 5 mL of thermosensitive nanogel solutions with multiple concentrations such as 7 wt%, 10 wt%, and 13 wt% were respectively placed in 20 mL vials. After being placed in a 40 °C water bath, the vials were tilted to observe the flow of the solution and photographed for recording. The results are as Figure 3 shown in a of

[0046] Second, a rheometer was used to perform rheological characterization on thermosensitive nanogel solutions with different concentrations. The samples were placed on a 25 mm diameter plate, and the sample distance was 1000 μm.

[0047] (1) A 1% strain was applied at an angular frequency of 10 rad / s, and a time sweep was performed in the range of 25 °C to 40 °C for 200 s with a heating rate of 1 °C / min to study the gelation time. The results are as Figure 3 shown in b of

[0048] (2) A temperature sweep experiment was performed at an angular frequency of 10 rad / s. First, the temperature was increased from 25 °C to 40 °C, and then decreased from 40 °C to 25 °C with a temperature change rate of 1 °C / min to evaluate the reversible transition of the sol-gel state. The results are as Figure 3 shown in c of

[0049] (3) A strain sweep test was performed at 37 °C, and the strain was increased from 0.1% to 1000% to verify the linear viscoelastic region. The results are as Figure 3 shown in d of

[0050] (4) A frequency sweep test was performed at 37 °C, the angular frequency was increased from 0.1 to 100 rad / s, and the applied strain was 1% to study the relationship between the angular frequency and the modulus. The results are as Figure 3 shown in e of

[0051] Example 4

[0052] Microscopic morphology of P(NVCL-co-GelMA) thermosensitive nanogels / hydrogels

[0053] First, prepare a 1 wt% thermosensitive nanogel solution. Drop the solution onto the center of a copper mesh using a syringe, stain it with a 1 mg / mL phosphotungstic acid solution for 5 min, and then place it in the dark. Observe the morphology of the thermosensitive nanogel using a transmission electron microscope the next day. The results are shown as Figure 4 shown in a of

[0054] Second, place the prepared thermosensitive nanogel solution in a 40 °C water bath to form a hydrogel state, then quickly freeze it in liquid nitrogen. After freeze-drying the sample using a vacuum freeze dryer for 2 days, perform platinum sputtering and then observe the microscopic morphology of the thermosensitive hydrogel using a scanning electron microscope. The results are shown as Figure 4 shown in b of

[0055] Example 5

[0056] In vitro adhesion test of P(NVCL-co-GelMA) thermosensitive nanogel / hydrogel:

[0057] Use the lap-shear test of a universal testing machine to evaluate the adhesion to pig skin and colon. After carefully defatting fresh pig skin and pig colon, wash them clean in PBS and cut them into the same size (6 cm long, 2 cm wide). Adhere two pieces of colon to two identical-sized thin sheets that are not easily stretched and deformed using strong glue. Apply 1 mL of the thermosensitive nanogel solution (7, 10, 13 wt%) evenly on the mucosal layer of one piece of colon, immediately cover it with another piece of colon, and the overlapping area is 2*2 cm 2 , and expose it at 37 °C for 5 min to promote gelation. The temperature is kept at 37 °C throughout the test, and at least three samples are tested for each group. Determine the adhesion performance of the thermosensitive nanogel to pig skin using the same method. The results are shown as Figure 5 shown in

[0058] Example 6

[0059] In vitro release test of P(NVCL-co-GelMA) thermosensitive nanogel / hydrogel:

[0060] The dialysis method was used to determine the release of 5-ASA from the temperature-sensitive nanogels. Different concentrations of the temperature-sensitive nanogel solutions prepared in Example 2 were taken, and 5-ASA with a mass ratio of 6.7% was added thereto. After stirring in the dark for 10 h, the temperature-sensitive nanogel solutions loaded with 5-ASA were obtained. 2 mL of the nanogel solution was filled into a dialysis bag with a molecular weight cut-off of 3500. First, it was exposed in a 37 °C water bath until a hydrogel was formed, and then it was immersed in PBS at 37 °C (pH 7.4, 500 mL), and incubated in a constant temperature oscillator at a rate of 100 r / min in the dark. 4 mL of the supernatant was taken at 0, 1, 2, 4, 8, 12, 24, and 48 h, and an equal volume of PBS at pH 7.4 at 37 °C was supplemented at the same time. Subsequently, the supernatant was reasonably diluted and the absorbance of 5-ASA at 331 nm was measured under an ultraviolet-visible near-infrared spectrometer, and the cumulative release rate was calculated. The cumulative release rate of the commercially available Salofalk enema was used as a control in the experiment. The results are as Figure 6 shown.

[0061] Example 7

[0062] In vivo experiments of P(NVCL-co-GelMA) temperature-sensitive nanogels / hydrogels:

[0063] Animal grouping: Healthy SD rats, male, 6 weeks old, were randomly divided into 5 groups:

[0064] 1) TNBS group: Induced only with TNBS, without treatment;

[0065] 2) Pure hydrogel group: The rats induced by TNBS were treated with temperature-sensitive nanogels without loading 5-ASA;

[0066] 3) 5-ASA hydrogel group: The rats induced by TNBS were treated with temperature-sensitive nanogels loaded with 5-ASA;

[0067] 4) Salofalk enema group (Salofalk group): The rats induced by TNBS were treated with Salofalk enema;

[0068] 5) Healthy group (Normal): Enema with normal saline was used as a control.

[0069] Animal model establishment: Sprague-Dawley (SD) rats were used to induce ulcerative colitis with 2,4,6-trinitrobenzenesulfonic acid (TNBS). One day before model establishment, the rats were fasted but allowed to drink water. On the day of the experiment, the purchased TNBS solution was first diluted, and ethanol was added as a disruptor of the intestinal mucosal barrier. The preparation method was to vortex and mix a 5% TNBS solution (w / v), absolute ethanol, and normal saline in a volume ratio of 2:2:1. Then, all rats were weighed. After anesthesia with isoflurane, a 2.5-mm diameter enema tube was used to slowly perfuse the prepared TNBS solution from the anus to 8 cm from the anus at a dose of 100 mg / kg, and the tail was lifted and inverted for 2 minutes to reduce overflow. When the rats showed continuous weight loss, loose stools, and positive fecal occult blood for several days, the model was considered successfully established.

[0070] Evaluation indicators:

[0071] 1) Disease Activity Index (DAI) score: It includes three items: weight change rate, fecal consistency, and fecal occult blood. The results are shown as a and b in Figure 7 . The specific DAI scoring criteria are shown in the following table after referring to the literature and making appropriate adjustments:

[0072]

[0073]

[0074] Histological evaluation of colon tissue: After 12 days of treatment, all rats were anesthetized and decapitated by cervical dislocation. Then, the entire colon was dissected, and the colon was collected and fixed in 4% paraformaldehyde. Subsequently, paraffin sections were prepared according to the conventional procedure, and hematoxylin-eosin (HE) staining, Masson staining, and alcian blue-periodic acid Schiff (AB-PAS) staining were performed respectively. The results are shown as c in Figure 7 .

[0075] Comparative Example 1

[0076] Pure PNVCL gel, pure GelMA gel, and the P(NVCL-co-GelMA) gel prepared in Example 1 were selected for comparison of thermosensitivity, mechanical properties, and stability. The results are as follows:

[0077] Pure PNVCL gel: The lower critical solution temperature (LCST) is 32 - 34 °C, and the sol-gel transition occurs when it is close to the human body's physiological temperature. However, due to the lack of a cross-linked structure, the gel strength is insufficient, dominated by hydrophobic segments, with high gel brittleness and poor shear recovery ability, and it is easily disintegrated by external forces or body fluid flushing.

[0078] Pure GelMA gel: It has no thermosensitivity, depends on methacrylated cross-linking, has high mechanical strength, but lacks dynamic responsiveness and is difficult to adapt to the surface of irregular tissues.

[0079] P(NVCL-co-GelMA) gel: The phase transition temperature is 35-37 °C (close to the human body's physiological body temperature). The covalent cross-linked network of GelMA and the temperature-sensitive dynamic network of PNVCL act synergistically to significantly improve the gel strength, enabling it to adhere to the ulcerative colitis lesion site for a long time and being suitable for in vivo applications.

[0080] The above are only the preferred embodiments of the present invention. The protection scope of the present invention is not limited to the above embodiments. All technical solutions falling within the concept of the present invention belong to the protection scope of the present invention. It should be noted that for those of ordinary skill in the art in this technical field, several improvements and refinements made without departing from the principle of the present invention should be regarded as within the protection scope of the present invention.

Claims

1. A thermosensitive nanogel, characterized in that, The temperature-sensitive nanogel is formed by free radical copolymerization of N-vinyl-ε-caprolactam and methacrylated gelatin; wherein, the temperature-sensitive nanogel can be phase-transformed from a sol state to a hydrogel state with temperature change, and the critical phase transition temperature is 33°C to 37°C.

2. The thermosensitive nanogel according to claim 1, wherein The mass ratio of the N-vinyl-ε-caprolactam to the methacrylated gelatin is 1:(0.01 - 0.1).

3. A preparation method of a temperature-sensitive nanogel, characterized in that, It includes the following steps: Under the protection of inert gas, into the mixture of N-vinyl-ε-caprolactam, disodium ethylenediaminetetraacetate, and sodium formate, methacrylated gelatin and an initiator are added, mixed and heated to carry out free radical copolymerization reaction to obtain a reaction product, and the temperature-sensitive nanogel is obtained after purifying the reaction product.

4. The preparation method according to claim 3, wherein The mass ratio of the N-vinyl-ε-caprolactam, disodium ethylenediaminetetraacetate, and sodium formate is 1:(0.001 - 0.005):(0.005 - 0.01).

5. The preparation method according to claim 4, characterized in that, The methacrylated gelatin is added after being pre-heated in solution form, the concentration of the methacrylated gelatin solution is (10 - 15)% w / v, and the pre-heating treatment of the methacrylated gelatin solution is: heating the methacrylated gelatin solution in a water bath at 40 - 50°C for 1 - 2 h.

6. The preparation method according to claim 5, characterized in that, The reaction temperature is 60 - 70°C, and the reaction time is 3 - 5 h.

7. The preparation method according to claim 6, characterized in that, The initiator is 2,2'-azobis(2-methylpropionamidine) dihydrochloride, and the mass ratio of the 2,2'-azobis(2-methylpropionamidine) dihydrochloride to the N-vinyl-ε-caprolactam is (0.005 - 0.01):

1.

8. A thermosensitive nanogel enema solution for delivering 5-aminosalicylic acid, characterized in that, Using the temperature-sensitive nanogel described in claim 1 or 2 as a delivery matrix.

9. The thermosensitive nanogel enema solution according to claim 8, wherein After ball-milling 5-aminosalicylic acid and mixing it with a temperature-sensitive nanogel solution with a concentration of 5 - 15% w / v and stirring for 5 - 24 h, the temperature-sensitive nanogel enema solution is obtained.

10. A therapeutic drug for ulcerative colitis, characterized in that, The therapeutic drug includes the temperature-sensitive nanogel enema solution described in any one of claims 8 - 9, and the temperature-sensitive nanogel enema solution is phase-transformed from a sol state to a hydrogel state in the colon.

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