Dual-network gel microspheres with pH response as well as preparation method and application of dual-network gel microspheres

Abstract

The invention discloses a dual-network gel microsphere with pH response as well as a preparation method and application of the dual-network gel microsphere. The preparation method comprises the following steps: under the catalytic action of EDC and NHS, enabling indolepropionic acid to react with 2-hydroxyethyl vinyl ether, so as to prepare an indolepropionic acid-2-hydroxyethyl vinyl ether polymer; under the catalytic action of p-toluene sulfonamide, enabling the indolepropionic acid-2-hydroxyethyl vinyl ether polymer to react with high amylose starch, so as to prepare indolepropionic acid grafted starch; the indolepropionic acid grafted starch, sodium alginate and water are mixed to serve as a dispersion phase; a solution at least containing a surfactant is used as a continuous phase, and then the dual-network gel microspheres with pH response are prepared by adopting a microfluidic technology. The dual-network gel microspheres with pH response prepared by the invention have good thermal stability and pH responsiveness, and can realize processing of indolepropionic acid and polyphenol and stability of oral delivery.

Description

Technical Field

[0001] The invention belongs to the fields of food, biomaterials, microfluidics and embedding delivery technology, and specifically relates to a double-network gel microsphere with pH response and a preparation method and application thereof. Background Art

[0002] Tryptophan is found in high concentrations in many foods, including cruciferous vegetables and meat, and can be broken down into a series of metabolites by intestinal microorganisms in the colon. Indolepropionic acid, as a metabolite of tryptophan, has multiple health benefits, including regulating plant growth and participating in the balance of human intestinal flora. Indolepropionic acid acts by binding to aryl hydrocarbon receptors and regulating intestinal immune homeostasis by inhibiting proinflammatory cytokine levels and inflammatory responses. It has been reported that the concentration of indolepropionic acid in the feces of patients with colitis is reduced. Therefore, increasing the content of indolepropionic acid in the colon can effectively prevent and alleviate the symptoms of intestinal inflammation. However, the stability and bioavailability of indolepropionic acid in the body are limited, and an effective delivery system is needed to enhance its efficacy.

[0003] Dietary polyphenols not only have anti-inflammatory and anti-cancer effects, and can prevent the occurrence of chronic non-communicable diseases such as cardiovascular and cerebrovascular diseases, type II diabetes, and cognitive dysfunction, but can also regulate intestinal flora and improve immunity. They are a recognized functional factor of healthy foods. However, dietary polyphenols are generally sensitive to light and heat, and are easily decomposed and oxidized during processing, resulting in insufficient daily intake. In addition, polyphenols are easily destroyed by the upper digestive tract in the human body and are difficult to be absorbed and utilized by the intestines, which makes it difficult for them to fully exert their efficacy.

[0004] In the field of biomaterials, high-amylose starch and sodium alginate have been widely studied and applied due to their unique physicochemical properties and biocompatibility. High-amylose starch is used to prepare oral matrices for controlled drug release due to its high resistant starch content and excellent barrier properties. High-amylose starch is a resistant starch that can resist the destruction of gastric acid and enzymes and produce short-chain fatty acids through intestinal microbial decomposition. Therefore, high-amylose starch can not only promote intestinal peristalsis as a dietary fiber, but also release short-chain fatty acids to promote the proliferation of intestinal probiotics. In view of the resistance of high-amylose starch to small intestinal digestion, grafting indolepropionic acid with high-amylose starch may be an effective method for stable delivery of indolepropionic acid. Sodium alginate, as a natural polysaccharide, is often used to prepare hydrogels for drug delivery and tissue engineering due to its good biocompatibility and gelation properties. However, the mechanical strength of a single sodium alginate gel is low, and it is easy to deform, defect or even collapse when squeezed or sheared, resulting in premature exposure of the embedded material. Summary of the invention

[0005] The main purpose of the present invention is to provide a double-network gel microsphere with pH response and a preparation method and application thereof, so as to overcome the shortcomings of the prior art.

[0006] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention includes:

[0007] The embodiment of the present invention provides a method for preparing double-network gel microspheres with pH response, which comprises:

[0008] Under the catalytic action of EDC and NHS, indolepropionic acid reacts with 2-hydroxyethyl vinyl ether to prepare indolepropionic acid-2-hydroxyethyl vinyl ether polymer;

[0009] Under the catalytic action of p-toluenesulfonamide, the indolepropionic acid-2-hydroxyethyl vinyl ether polymer is reacted with high-amylose starch to prepare indolepropionic acid grafted starch;

[0010] Furthermore, the indolepropionic acid grafted starch, sodium alginate and water are mixed as a dispersed phase; a solution containing a surfactant is used as a continuous phase, and then microfluidic technology is used to prepare double-network gel microspheres with pH response.

[0011] The embodiment of the present invention also provides pH-responsive double-network gel microspheres prepared by the aforementioned preparation method.

[0012] The embodiment of the present invention also provides the use of the aforementioned double-network gel microspheres with pH response in a drug delivery system.

[0013] The present invention also provides a method for preparing a pH-responsive drug delivery system, which comprises:

[0014] Under the catalytic action of EDC and NHS, indolepropionic acid reacts with 2-hydroxyethyl vinyl ether to prepare indolepropionic acid-2-hydroxyethyl vinyl ether polymer;

[0015] Under the catalytic action of p-toluenesulfonamide, the indolepropionic acid-2-hydroxyethyl vinyl ether polymer is reacted with high-amylose starch to prepare indolepropionic acid grafted starch;

[0016] Furthermore, the indolepropionic acid grafted starch, sodium alginate and water are mixed as a dispersed phase; an oil solution containing at least a surfactant and polyphenols is used as a continuous phase, and then a pH-responsive drug delivery system is prepared using microfluidic technology.

[0017] The embodiment of the present invention also provides a pH-responsive drug delivery system prepared by the aforementioned preparation method.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The present invention effectively solves the problem of low oral bioavailability of indolepropionic acid and polyphenols by co-delivering indolepropionic acid and polyphenols, thereby improving their absorption and utilization efficiency in the body, thereby improving bioavailability;

[0020] (2) The indolepropionic acid grafted starch polymer prepared by the present invention has pH responsiveness and can respond under a specific pH environment to achieve controlled release of the drug, thereby improving the efficacy of the drug and reducing side effects;

[0021] (3) The present invention introduces acetal bonds and calcium ion induction to prepare pH-responsive double-network gel microspheres and pH-responsive drug delivery systems, thereby enhancing the mechanical strength and stability of the gel microspheres;

[0022] (4) The present invention utilizes microfluidic technology to accurately control the size and uniformity of gel microspheres, providing a more precise and controllable carrier for drug delivery;

[0023] (5) The present invention prepares a novel grafted starch polymer by grafting indolepropionic acid onto high-amylose starch, thereby broadening the application field of starch-based materials;

[0024] (6) The preparation method of the present invention is simple to operate, easy to scale up production, and conducive to industrial application;

[0025] (7) Through the optimized preparation process, the present invention achieves efficient embedding of indolepropionic acid and polyphenols, thereby increasing the drug loading capacity;

[0026] (8) The present invention uses high-amylose starch and sodium alginate as main raw materials, and the prepared gel microspheres and drug delivery systems have good biocompatibility and are suitable for oral drug delivery;

[0027] (9) The raw materials and solvents used in the preparation process of the present invention are easily degradable, environmentally friendly, and meet the requirements of green chemistry;

[0028] (10) The drug delivery system prepared by the present invention can not only be used for the delivery of indolepropionic acid and polyphenols, but can also be extended to the delivery of other drugs or active ingredients, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1is a schematic diagram of a microfluidic device in a typical embodiment of the present invention;

[0031] Figure 2 is a graph of the release rate of indolepropionic acid of the indolepropionic acid grafted high-amylose starch prepared in Examples 1-4 of the present invention in solutions with different pH values;

[0032] Figure 3 is a particle size diagram of the indolepropionic acid grafted high-amylose starch / sodium alginate gel microspheres prepared in Examples 1-4 of the present invention;

[0033] Figure 4 is a cytotoxicity graph of the indolepropionic acid grafted high amylose starch / sodium alginate solution prepared in Examples 1-4 of the present invention;

[0034] Figure 5 is a graph showing the release rate of gallic acid under different pH conditions in the indolepropionic acid grafted high-amylose starch / sodium alginate / gallic acid gel microspheres prepared in Example 4 of the present invention;

[0035] Figure 6 is a graph showing the release rate of gallic acid in the indolepropionic acid grafted high-amylose starch / sodium alginate / gallic acid gel microspheres prepared in Example 4 of the present invention under different temperature conditions;

[0036] Figure 7 The present invention is a typical embodiment of the reaction flow chart of the process of preparing indolepropionic acid grafted high amylose starch. DETAILED DESCRIPTION

[0037] In view of the defects of the prior art, the inventors of this case have proposed the technical solution of the present invention after long-term research and extensive practice. The technical solution mainly uses high-amylose starch and sodium alginate as raw materials, introduces acetal bonds to prepare pH-responsive indolepropionic acid grafted starch polymers, and then mixes them with sodium alginate aqueous solution. Finally, microfluidic technology is used to prepare oral microgel beads for co-delivering indolepropionic acid and polyphenols, so as to solve the problem of low oral bioavailability of indolepropionic acid and polyphenols.

[0038] The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] Specifically, as one aspect of the technical solution of the present invention, a method for preparing a double-network gel microsphere with pH response includes:

[0040] Under the catalytic action of EDC and NHS, indolepropionic acid reacts with 2-hydroxyethyl vinyl ether to prepare indolepropionic acid-2-hydroxyethyl vinyl ether polymer;

[0041] Under the catalytic action of p-toluenesulfonamide, the indolepropionic acid-2-hydroxyethyl vinyl ether polymer is reacted with high-amylose starch to prepare indolepropionic acid grafted starch;

[0042] Furthermore, the indolepropionic acid grafted starch, sodium alginate and water are mixed as a dispersed phase; a solution containing a surfactant is used as a continuous phase, and then microfluidic technology is used to prepare double-network gel microspheres with pH response.

[0043] In some preferred embodiments, the preparation method specifically comprises: mixing indolepropionic acid, EDC, NHS and a solvent and stirring at room temperature for 8-12 hours to form a mixed solution, then adding 2-hydroxyethyl vinyl ether (HEVE) and stirring the mixture at 40-60° C. for 18-24 hours, and then dialyzing, centrifuging, washing and freeze-drying to obtain an indolepropionic acid-2-hydroxyethyl vinyl ether polymer.

[0044] Specifically, the preparation method of the indolepropionic acid-2-hydroxyethyl vinyl ether polymer (indolepropionic acid-HEVE polymer) includes: 5% (w / v) indolepropionic acid, 2.5% (w / v) EDC and 1% (w / v) NHS are dissolved in DMF, stirred at 300 rpm for 12 hours at room temperature to obtain a uniform transparent solution, 1% (v / v) 2-hydroxyethyl vinyl ether (HEVE) is added to the solution, magnetically stirred in a 40°C water bath for 24 hours, dialyzed for three days, centrifuged and washed the precipitate three times, and freeze-dried to obtain indolepropionic acid-HEVE polymer powder.

[0045] In some preferred embodiments, the preparation method specifically includes: mixing high-amylose starch, indolepropionic acid-2-hydroxyethyl vinyl ether polymer, p-toluenesulfonamide (p-TSA) and a solvent and stirring the mixture at room temperature for 48 hours, followed by dialysis, centrifugation, washing and freeze-drying to obtain indolepropionic acid grafted starch.

[0046] Specifically, the preparation method of the indolepropionic acid grafted starch includes: adding 4% (w / v) high-amylose starch, 2% (w / v) indolepropionic acid-HEVE and 0.1% (w / v) p-TSA to a DMF solution, stirring at room temperature for 48 hours, placing the mixture in a dialysis bag with a molecular weight cutoff of 8k-14kDa, dialyzing in distilled water for one week, centrifuging and washing the precipitate 3 times, and freeze-drying to obtain the indolepropionic acid grafted high-amylose starch.

[0047] The reaction flow chart of the preparation process of indolepropionic acid grafted high amylose starch in the present invention is as follows: Figure 7 shown.

[0048] In some preferred embodiments, the preparation method specifically comprises:

[0049] Mixing indolepropionic acid grafted starch, sodium alginate and water to form a first mixed solution;

[0050] forming a second mixed solution from a solution containing a surfactant;

[0051] Furthermore, using microfluidic technology, the first mixed solution is passed into the first channel (microfluidic chip channel 1) as a dispersed phase, and the second mixed solution is passed into the second channel of the microfluidic chip (microfluidic chip channel 2) as a continuous phase. The generated microspheres are then allowed to stand and solidify in a calcium chloride solution to obtain double-network gel microspheres with pH response.

[0052] Furthermore, the inner diameter of the circular capillary used in the microfluidic chip channel 1 is 180-260 μm.

[0053] Furthermore, the inner diameter of the circular capillary of the microfluidic chip channel 2 is 120-200 μm.

[0054] Specifically, the preparation method of the pH-responsive double-network gel microspheres includes:

[0055] Sodium alginate and indolepropionic acid grafted starch were mixed in a mass ratio of 10:1, 5:1 and 1:1 and dissolved in distilled water to prepare a 1% (w / v) mixed solution;

[0056] The mixed solution was passed into channel 1 of the microfluidic chip as the dispersed phase, and the mixed solution containing 2% surfactant was passed into channel 2 of the microfluidic chip as the continuous phase. After the microspheres were uniformly generated, they could be collected into centrifuge tubes and the collected microspheres were allowed to stand in calcium chloride for 30 minutes to solidify.

[0057] In some more specific embodiments, the method for preparing the pH-responsive double-network gel microspheres comprises:

[0058] Step 1: Preparation of indolepropionic acid-HEVE polymer: indolepropionic acid and 2-hydroxyethyl vinyl ether (HEVE) were used as raw materials to prepare indolepropionic acid-HEVE under the catalysis of EDC and NHS, and the precipitate was washed by centrifugation for 3 times after dialysis for 3 days, and the indolepropionic acid-HEVE polymer powder was obtained by freeze drying;

[0059] Step 2: preparing indolepropionic acid grafted starch: mixing the indolepropionic acid-HEVE prepared in step 1.1 with high-amylose starch, combining the indolepropionic acid-HEVE with the high-amylose starch under the catalysis of p-toluenesulfonamide (p-TSA), and preparing indolepropionic acid grafted starch with pH response;

[0060] Step 3: preparing an indolepropionic acid grafted starch / sodium alginate mixed solution: mixing sodium alginate and indolepropionic acid grafted starch at a mass ratio of 10:1, 5:1 and 1:1, and dissolving them in distilled water to prepare a 1% (w / v) mixed solution;

[0061] Step 4. Preparation of indolepropionic acid grafted starch / sodium alginate gel microspheres: Pass the solution prepared in step 3 into channel 1 of the microfluidic chip as the dispersed phase, and pass a 2% surfactant solution into channel 2 of the microfluidic chip as the continuous phase. After the microspheres are uniformly generated, they can be collected into a centrifuge tube and the collected microspheres are allowed to stand in calcium chloride for 30 minutes to solidify.

[0062] Another aspect of the embodiments of the present invention further provides double-network gel microspheres with pH response obtained by the aforementioned preparation method.

[0063] Another aspect of the embodiments of the present invention further provides the use of the aforementioned double-network gel microspheres with pH response in a drug delivery system.

[0064] Another aspect of the embodiments of the present invention further provides a method for preparing a pH-responsive drug delivery system, comprising:

[0065] Under the catalytic action of EDC and NHS, indolepropionic acid reacts with 2-hydroxyethyl vinyl ether to prepare indolepropionic acid-2-hydroxyethyl vinyl ether polymer;

[0066] Under the catalytic action of p-toluenesulfonamide, the indolepropionic acid-2-hydroxyethyl vinyl ether polymer is reacted with high-amylose starch to prepare indolepropionic acid grafted starch;

[0067] Furthermore, the indolepropionic acid grafted starch, sodium alginate and water are mixed as a dispersed phase; an oil solution containing at least a surfactant and polyphenols is used as a continuous phase, and then a pH-responsive drug delivery system is prepared using microfluidic technology.

[0068] In some preferred embodiments, the preparation method specifically includes: mixing indolepropionic acid, EDC, NHS and a solvent and stirring at room temperature for 8-12 hours to form a mixed solution, then adding 2-hydroxyethyl vinyl ether and stirring at 40-60°C for 18-24 hours, and then dialyzing, centrifuging, washing, and freeze-drying to obtain indolepropionic acid-2-hydroxyethyl vinyl ether polymer.

[0069] Specifically, the preparation method of the indolepropionic acid-2-hydroxyethyl vinyl ether polymer (indolepropionic acid-HEVE polymer) includes: 5% (w / v) indolepropionic acid, 2.5% (w / v) EDC and 1% (w / v) NHS are dissolved in DMF, stirred at 300 rpm for 12 hours at room temperature to obtain a uniform transparent solution, 1% (v / v) 2-hydroxyethyl vinyl ether (HEVE) is added to the solution, magnetically stirred in a 40°C water bath for 24 hours, dialyzed for three days, centrifuged and washed the precipitate three times, and freeze-dried to obtain indolepropionic acid-HEVE polymer powder.

[0070] In some preferred embodiments, the preparation method specifically includes: mixing high-amylose starch, indolepropionic acid-2-hydroxyethyl vinyl ether polymer, p-toluenesulfonamide and a solvent and stirring the mixture at room temperature for 48 hours, followed by dialysis, centrifugation, washing and freeze-drying to obtain indolepropionic acid grafted starch.

[0071] Specifically, the preparation method of the indolepropionic acid grafted starch includes: adding 4% (w / v) high-amylose starch, 2% (w / v) indolepropionic acid-HEVE and 0.1% (w / v) p-TSA to a DMF solution, stirring at room temperature for 48 hours, placing the mixture in a dialysis bag with a molecular weight cutoff of 8k-14kDa, dialyzing in distilled water for one week, centrifuging and washing the precipitate 3 times, and freeze-drying to obtain the indolepropionic acid grafted high-amylose starch.

[0072] In some preferred embodiments, the preparation method specifically comprises:

[0073] mixing indolepropionic acid grafted starch, sodium alginate and water to form a third mixed solution;

[0074] forming a fourth mixed solution from an oil solution containing a surfactant and polyphenols;

[0075] In addition, using microfluidic technology, the third mixed solution is introduced into the first channel of the microfluidic chip (microfluidic chip channel 1) as a dispersed phase, and the fourth mixed solution is introduced into the second channel of the microfluidic chip (microfluidic chip channel 2) as a continuous phase. The generated microspheres are then allowed to stand and solidify in a calcium chloride solution to obtain double-network gel microspheres with pH response.

[0076] Furthermore, the inner diameter of the circular capillary used in the microfluidic chip channel 1 is 180-260 μm.

[0077] Furthermore, the inner diameter of the circular capillary of the microfluidic chip channel 2 is 120-200 μm.

[0078] In some preferred embodiments, the high-amylose starch includes any one or more combinations of high-amylose corn starch, high-amylose wheat starch, and isoamylase-hydrolyzed corn starch, but is not limited thereto.

[0079] In some preferred embodiments, the polyphenolic substances include any one or more combinations of gallic acid, ursolic acid, ferulic acid, berberine, magnolol, and coumarin, but are not limited thereto.

[0080] In some preferred embodiments, the surfactant includes any one or more combinations of Tween 80, Span 20, Span 40, and Span 60, but is not limited thereto.

[0081] In some preferred embodiments, the solvent includes DMF and / or DMSO, but is not limited thereto.

[0082] In some preferred embodiments, the oil solution includes any one or more combinations of corn oil, soybean oil, palm oil, and sunflower oil, but is not limited thereto.

[0083] In some more specific embodiments, the method for preparing the pH-responsive drug delivery system comprises:

[0084] S1. Preparation of indolepropionic acid-HEVE polymer: Using high-amylose corn starch, indolepropionic acid and 2-hydroxyethyl vinyl ether (HEVE) as raw materials, indolepropionic acid-HEVE was first prepared under the catalysis of EDC and NHS. After dialysis for three days, the precipitate was washed by centrifugation three times and freeze-dried to obtain indolepropionic acid-HEVE polymer powder.

[0085] S2. Preparation of indolepropionic acid grafted starch: The indolepropionic acid-HEVE prepared in S1 is mixed with high-amylose starch, and the indolepropionic acid-HEVE and high-amylose starch are combined under the catalysis of p-toluenesulfonamide (p-TSA) to prepare indolepropionic acid grafted starch with pH response.

[0086] S3. Prepare an indolepropionic acid grafted starch / sodium alginate mixed solution: Sodium alginate and indolepropionic acid grafted starch are mixed in mass ratios of 10:1, 5:1 and 1:1, and dissolved in distilled water to prepare a 1% (w / v) mixed solution.

[0087] S4. Preparation of indolepropionic acid grafted starch / sodium alginate gel microspheres (i.e., double-network gel microspheres with pH response): the solution prepared in S3 is passed into channel 1 of the microfluidic chip as the dispersed phase, and the oil solution prepared containing 2% of a surfactant is passed into channel 2 of the microfluidic chip as the continuous phase. After the microspheres are uniformly generated, they can be received into a centrifuge tube in channel 3, and the collected microspheres are allowed to stand in calcium chloride for 30 minutes to solidify.

[0088] S5. Preparation of indolepropionic acid grafted starch / sodium alginate / polyphenol gel microspheres (i.e., a drug delivery system with pH response): the indolepropionic acid grafted starch / sodium alginate aqueous solution prepared in S4 is introduced into channel 1 of the microfluidic chip as the dispersed phase, and an oil solution containing 2% of a surfactant and 1% (w / v) of polyphenols is introduced into channel 2 of the microfluidic chip as the continuous phase. After the microspheres are uniformly generated, they can be collected into a centrifuge tube and the collected microspheres are allowed to stand in calcium chloride for 30 minutes to solidify.

[0089] As a further technical solution, the polyphenols described in step S5 are gallic acid, ursolic acid, ferulic acid, berberine, magnolol and coumarin.

[0090] As a further technical solution, the preparation method of the indolepropionic acid-HEVE polymer described in step S1 includes the following steps: 5% (w / v) indolepropionic acid, 2.5% (w / v) EDC and 1% (w / v) NHS are dissolved in DMF, stirred at 300rpm for 12 hours at room temperature to obtain a uniform transparent solution, 1% (v / v) 2-hydroxyethyl vinyl ether (HEVE) is added to the solution, and magnetic stirring is performed in a water bath at 40°C for 24 hours. The mixed solution is placed in a dialysis bag with a molecular weight cutoff of 8k-14kDa, and indolepropionic acid-EGVE is obtained after dialysis in distilled water for three days. The supernatant is removed after centrifugation, and the bottom is washed with distilled water for 3 times and then stored in a refrigerator at -20°C for 12 hours, and vacuum freeze-dried at -50°C and a vacuum degree of 20Pa for 24 hours to obtain indolepropionic acid-EVGE complex powder.

[0091] As a further technical solution, the preparation method of indolepropionic acid grafted high-amylose starch described in step S2 comprises the following steps: 4% (w / v) high-amylose starch, 2% (w / v) indolepropionic acid-HEVE and 0.1% (w / v) p-TSA are added to a DMF solution, stirred at room temperature for 48 hours, and then the mixture is placed in a dialysis bag with a molecular weight cutoff of 8k-14kDa, and dialyzed in distilled water for one week. The liquid inside the dialysis bag is centrifuged, and the precipitate is washed with distilled water 3 times and then stored in a refrigerator at -20°C for 12 hours, and vacuum freeze-dried at -50°C and a vacuum degree of 20Pa for 24 hours to obtain indolepropionic acid grafted starch.

[0092] As a further technical solution, the preparation method of the indolepropionic acid grafted starch / sodium alginate gel microspheres described in step S4 includes the following steps: adding 1% (w / v) of the mixed solution of sodium alginate and indolepropionic acid grafted starch prepared in step S3 to the dispersed phase reservoir through channel 1 of the microfluidic chip, and adding an oil solution containing 2% (w / v) surfactant and 1% (w / v) polyphenols to the continuous phase reservoir through channel 2 of the microfluidic chip.

[0093] Furthermore, the pressure of channel 1 (dispersed phase, 250 mbar) and the pressure of channel 2 (continuous phase, 250 mbar) were set to exhaust the air in the pipeline and the chip.

[0094] Furthermore, after the pipeline and the chip are filled with liquid, the entire system is switched from pressure control to flow rate control, and the flow rates of channel 1 (2 mL / h) and channel 2 (2 mL / h) are set.

[0095] Furthermore, after the microspheres are generated uniformly and stably, the microspheres can be received in channel 3; the collection is stopped after a period of time, the microspheres are sealed in a centrifuge tube, and allowed to stand in a 2% calcium chloride solution for 10 minutes to solidify.

[0096] Furthermore, the inner diameter of the circular capillary of the mobile phase selected in the microfluidic chip is 240 μm, and the inner diameter of the circular capillary of the continuous phase is 180 μm.

[0097] As a further technical solution, the preparation of indolepropionic acid grafted starch / sodium alginate / polyphenol gel microspheres described in step S5 includes the following steps: the indolepropionic acid grafted starch / sodium alginate aqueous solution prepared in S4 is introduced into channel 1 of the microfluidic chip as a dispersed phase, and an oil solution containing 2% surfactant and 1% (w / v) polyphenol is introduced into channel 2 of the microfluidic chip as a continuous phase. After the microspheres are uniformly generated, they can be received into a centrifuge tube, and the collected microspheres are allowed to stand in calcium chloride for 30 minutes to solidify.

[0098] Furthermore, the pressure of channel 1 (dispersed phase, 250 mbar) and the pressure of channel 2 (continuous phase, 250 mbar) were set to exhaust the air in the pipeline and the chip.

[0099] Furthermore, after the pipeline and the chip are filled with liquid, the entire system is switched from pressure control to flow rate control, and the flow rates of channel 1 (2 mL / h) and channel 2 (2 mL / h) are set.

[0100] Furthermore, after the microspheres are generated uniformly and stably, the microspheres can be received in channel 3; the collection is stopped after a period of time, the microspheres are sealed in a centrifuge tube, and allowed to stand in a 2% calcium chloride solution for 10 minutes to solidify.

[0101] Furthermore, the inner diameter of the circular capillary of the mobile phase selected in the microfluidic chip is 240 μm, and the inner diameter of the circular capillary of the continuous phase is 180 μm.

[0102] The schematic diagram of the microfluidic device used in the present invention is as follows Figure 1 shown.

[0103] Another aspect of the embodiments of the present invention further provides a pH-responsive drug delivery system prepared by the aforementioned preparation method.

[0104] The pH-responsive drug delivery system prepared by the present invention has the advantages of improving drug efficacy, reducing side effects, and accurately controlling release, and is of great significance for improving the oral bioavailability of drugs.

[0105] The present invention provides a double network gel microsphere with pH response and a preparation method and application thereof, wherein the method introduces a pH response bond (acetal bond) into indolepropionic acid and high-amylose starch, prepares a grafted starch polymer with indolepropionic acid specifically cleaved and released at pH 5-7, crosslinks the indolepropionic acid grafted starch with sodium alginate through calcium ions, and prepares a double network gel microsphere for co-delivering indolepropionic acid and polyphenols through microfluidic technology. The introduction of the acetal bond gives the gel microsphere pH responsiveness, avoiding the damage of indolepropionic acid and polyphenols by the oral and gastric environments. Indolepropionic acid, as a prebiotic, can regulate intestinal flora, promote the decomposition of short-chain fatty acids in the intestine, improve the intestinal flora microenvironment and prevent intestinal inflammation. The double network gel microspheres with pH response release of indolepropionic acid grafted starch / sodium alginate prepared by the present invention have good thermal stability and pH responsiveness, and can achieve the processing of indolepropionic acid and polyphenols and the stability of oral delivery.

[0106] The technical solution of the present invention is further described in detail below in conjunction with several preferred embodiments and drawings. This embodiment is implemented on the premise of the technical solution of the invention, and a detailed implementation method and specific operation process are given, but the protection scope of the present invention is not limited to the following embodiments.

[0107] Unless otherwise specified, the experimental materials used in the following examples can be purchased from conventional biochemical reagent companies.

[0108] Example 1

[0109] A preparation method and application of pH-responsive indolepropionic acid grafted starch / sodium alginate double network gel microspheres, comprising the following steps:

[0110] S1. Preparation of indolepropionic acid-HEVE polymer: 5% (w / v) indolepropionic acid, 2.5% (w / v) EDC and 1% (w / v) NHS were dissolved in DMF, stirred at 300rpm for 12 hours at room temperature to obtain a uniform transparent solution, 1% (v / v) 2-hydroxyethyl vinyl ether (HEVE) was added to the solution, and magnetic stirring was performed in a water bath at 40°C for 24 hours. The mixed solution was placed in a dialysis bag with a molecular weight cutoff of 8k-14kDa, and indolepropionic acid-HEVE was obtained after dialysis in distilled water for three days. The supernatant was removed after centrifugation, and the bottom was washed with distilled water for 3 times and stored in a refrigerator at -20°C for 12 hours, and vacuum freeze-dried at -50°C and a vacuum degree of 20Pa for 24 hours to obtain indolepropionic acid-HEVE polymer powder;

[0111] S2. Preparation of indolepropionic acid grafted starch: 4% (w / v) high amylose starch, 2% (w / v) indolepropionic acid-HEVE and 0.1% (w / v) p-TSA were added to the DMF solution, stirred at room temperature for 48 hours, and then the mixture was placed in a dialysis bag with a molecular weight cutoff of 8k-14kDa and dialyzed in distilled water for one week. The liquid inside the dialysis bag was centrifuged, and the precipitate was washed with distilled water 3 times and stored in a refrigerator at -20°C for 12 hours, and vacuum freeze-dried at -50°C and a vacuum degree of 20Pa for 24 hours to obtain indolepropionic acid grafted starch;

[0112] S3, preparing an indolepropionic acid grafted starch / sodium alginate mixed solution: mixing sodium alginate and indolepropionic acid grafted starch in a mass ratio of 10:1, dissolving in distilled water to prepare a 1% (w / v) mixed solution, and stirring at room temperature until the powders are evenly dispersed;

[0113] S4, preparation of indolepropionic acid grafted starch / sodium alginate gel microspheres: add 1% (w / v) of sodium alginate and indolepropionic acid grafted starch mixed solution prepared in step S3 to the dispersed phase reservoir through channel 1 of the microfluidic chip, add a mixed oil solution containing 2% (w / v) surfactant Tween 80 to the continuous phase reservoir, and pass through channel 2 of the microfluidic chip. The microfluidic chip is connected to a peristaltic pump through a capillary glass tube, wherein the inner diameter of the circular capillary of the mobile phase is 240 μm, and the inner diameter of the circular capillary of the continuous phase is 180 μm. Set the pressure of channel 1 (dispersed phase, 250 mbar) and the pressure of channel 2 (continuous phase, 250 mbar) to exhaust the air in the pipeline and chip. After the pipeline and the chip are filled with liquid, switch the entire system from pressure control to flow rate control, and set the flow rate of channel 1 (2 mL / h) and the flow rate of channel 2 (2 mL / h). After the microspheres are uniformly generated, they can be collected into 1.5 mL centrifuge tubes; after a period of time, stop collecting, seal the tubes, and place them in a 2% calcium chloride solution for 10 minutes to solidify.

[0114] Example 2

[0115] S1. Preparation of indolepropionic acid-HEVE polymer: 5% (w / v) indolepropionic acid, 2.5% (w / v) EDC and 1% (w / v) NHS were dissolved in DMF, stirred at 300rpm for 12 hours at room temperature to obtain a uniform transparent solution, 1% (v / v) 2-hydroxyethyl vinyl ether (HEVE) was added to the solution, and magnetic stirring was performed in a water bath at 40°C for 24 hours. The mixed solution was placed in a dialysis bag with a molecular weight cutoff of 8k-14kDa, and indolepropionic acid-HEVE was obtained after dialysis in distilled water for three days. The supernatant was removed after centrifugation, and the bottom was washed with distilled water for 3 times and stored in a refrigerator at -20°C for 12 hours, and vacuum freeze-dried at -50°C and a vacuum degree of 20Pa for 24 hours to obtain indolepropionic acid-HEVE complex powder;

[0116] S2. Preparation of indolepropionic acid grafted starch: 4% (w / v) high amylose starch, 2% (w / v) indolepropionic acid-HEVE and 0.1% (w / v) p-TSA were added to the DMF solution, stirred at room temperature for 48 hours, and then the mixture was placed in a dialysis bag with a molecular weight cutoff of 8k-14kDa and dialyzed in distilled water for one week. The liquid inside the dialysis bag was centrifuged, and the precipitate was washed with distilled water 3 times and stored in a refrigerator at -20°C for 12 hours, and vacuum freeze-dried at -50°C and a vacuum degree of 20Pa for 24 hours to obtain indolepropionic acid grafted starch;

[0117] S3, preparing an indolepropionic acid grafted starch / sodium alginate mixed solution: mixing sodium alginate and indolepropionic acid grafted starch in a mass ratio of 5:1, dissolving in distilled water to prepare a 1% (w / v) mixed solution, and stirring at room temperature until the powders are evenly dispersed;

[0118] S4, preparation of indolepropionic acid grafted starch / sodium alginate gel microspheres: add 1% (w / v) of sodium alginate and indolepropionic acid grafted starch mixed solution prepared in step S3 to the dispersed phase reservoir through channel 1 of the microfluidic chip, add a mixed oil solution containing 2% (w / v) surfactant Tween 80 to the continuous phase reservoir, and pass through channel 2 of the microfluidic chip. The microfluidic chip is connected to a peristaltic pump through a capillary glass tube, wherein the inner diameter of the circular capillary of the mobile phase is 240 μm, and the inner diameter of the circular capillary of the continuous phase is 180 μm. Set the pressure of channel 1 (dispersed phase, 250 mbar) and the pressure of channel 2 (continuous phase, 250 mbar) to exhaust the air in the pipeline and chip. After the pipeline and the chip are filled with liquid, switch the entire system from pressure control to flow rate control, and set the flow rate of channel 1 (2 mL / h) and the flow rate of channel 2 (2 mL / h). After the microspheres are uniformly generated, they can be collected into 1.5 mL centrifuge tubes; after a period of time, stop collecting, seal the tubes, and place them in a 2% calcium chloride solution for 10 minutes to solidify.

[0119] Example 3

[0120] S1. Preparation of indolepropionic acid-HEVE polymer: 5% (w / v) indolepropionic acid, 2.5% (w / v) EDC and 1% (w / v) NHS were dissolved in DMF, stirred at 300rpm for 12 hours at room temperature to obtain a uniform transparent solution, 1% (v / v) 2-hydroxyethyl vinyl ether (HEVE) was added to the solution, and magnetic stirring was performed in a water bath at 40°C for 24 hours. The mixed solution was placed in a dialysis bag with a molecular weight cutoff of 8k-14kDa, and indolepropionic acid-HEVE was obtained after dialysis in distilled water for three days. The supernatant was removed after centrifugation, and the bottom was washed with distilled water for 3 times and stored in a refrigerator at -20°C for 12 hours, and vacuum freeze-dried at -50°C and a vacuum degree of 20Pa for 24 hours to obtain indolepropionic acid-HEVE complex powder;

[0121] S2. Preparation of indolepropionic acid grafted starch: 4% (w / v) high amylose starch, 2% (w / v) indolepropionic acid-HEVE and 0.1% (w / v) p-TSA were added to the DMF solution, stirred at room temperature for 48 hours, and then the mixture was placed in a dialysis bag with a molecular weight cutoff of 8k-14kDa and dialyzed in distilled water for one week. The liquid inside the dialysis bag was centrifuged, and the precipitate was washed with distilled water 3 times and stored in a refrigerator at -20°C for 12 hours, and vacuum freeze-dried at -50°C and a vacuum degree of 20Pa for 24 hours to obtain indolepropionic acid grafted starch;

[0122] S3. Prepare an indolepropionic acid grafted starch / sodium alginate mixed solution: mix sodium alginate and indolepropionic acid grafted starch in a mass ratio of 1:1, dissolve in distilled water to prepare a 1% (w / v) mixed solution, and stir thoroughly at room temperature until the powders are evenly dispersed.

[0123] S4, preparation of indolepropionic acid grafted starch / sodium alginate gel microspheres: add 1% (w / v) of sodium alginate and indolepropionic acid grafted starch mixed solution prepared in step S3 to the dispersed phase reservoir through channel 1 of the microfluidic chip, add a mixed oil solution containing 2% (w / v) surfactant Tween 80 to the continuous phase reservoir, and pass through channel 2 of the microfluidic chip. The microfluidic chip is connected to a peristaltic pump through a capillary glass tube, wherein the inner diameter of the circular capillary of the mobile phase is 240 μm, and the inner diameter of the circular capillary of the continuous phase is 180 μm. Set the pressure of channel 1 (dispersed phase, 250 mbar) and the pressure of channel 2 (continuous phase, 250 mbar) to exhaust the air in the pipeline and chip. After the pipeline and the chip are filled with liquid, switch the entire system from pressure control to flow rate control, and set the flow rate of channel 1 (2 mL / h) and the flow rate of channel 2 (2 mL / h). After the microspheres are uniformly generated, they can be collected into 1.5 mL centrifuge tubes; after a period of time, stop collecting, seal the tubes, and place them in a 2% calcium chloride solution for 10 minutes to solidify.

[0124] Example 4

[0125] S1. Preparation of indolepropionic acid-HEVE polymer: 5% (w / v) indolepropionic acid, 2.5% (w / v) EDC and 1% (w / v) NHS were dissolved in DMF, stirred at 300rpm for 12 hours at room temperature to obtain a uniform transparent solution, 1% (v / v) 2-hydroxyethyl vinyl ether (HEVE) was added to the solution, and magnetic stirring was performed in a water bath at 40°C for 24 hours. The mixed solution was placed in a dialysis bag with a molecular weight cutoff of 8k-14kDa, and indolepropionic acid-HEVE was obtained after dialysis in distilled water for three days. The supernatant was removed after centrifugation, and the bottom was washed with distilled water for 3 times and stored in a refrigerator at -20°C for 12 hours, and vacuum freeze-dried at -50°C and a vacuum degree of 20Pa for 24 hours to obtain indolepropionic acid-HEVE complex powder;

[0126] S2. Preparation of indolepropionic acid grafted starch: 4% (w / v) high amylose starch, 2% (w / v) indolepropionic acid-HEVE and 0.1% (w / v) p-TSA were added to the DMF solution, stirred at room temperature for 48 hours, and then the mixture was placed in a dialysis bag with a molecular weight cutoff of 8k-14kDa and dialyzed in distilled water for one week. The liquid inside the dialysis bag was centrifuged, and the precipitate was washed with distilled water 3 times and stored in a refrigerator at -20°C for 12 hours, and vacuum freeze-dried at -50°C and a vacuum degree of 20Pa for 24 hours to obtain indolepropionic acid grafted starch;

[0127] S3. Prepare an indolepropionic acid grafted starch / sodium alginate mixed solution: Sodium alginate and indolepropionic acid grafted starch are mixed in a mass ratio of 5:1 and dissolved in distilled water to prepare a 1% (w / v) mixed solution, and stirred at room temperature until the powders are evenly dispersed.

[0128] S4. Preparation of indolepropionic acid grafted starch / sodium alginate / gallic acid gel microspheres: the solution prepared in S3 is passed into channel 1 of the microfluidic chip as the dispersed phase, and the mixed oil solution containing 2% surfactant Tween 80 and 1% (w / v) gallic acid is passed into channel 2 of the microfluidic chip as the continuous phase. After the microspheres are uniformly generated, they can be received into a centrifuge tube in channel 3, and the collected microspheres are allowed to stand in calcium chloride for 30 minutes to solidify.

[0129] Comparative Example 1

[0130] The preparation method is substantially the same as that of Example 1, except that indolepropionic acid is not added in step S2, and high-amylose corn starch and sodium alginate are used to prepare double-network gel microspheres in steps S3 and S4.

[0131] Comparative Example 2

[0132] The preparation method is substantially the same as that of Example 1, except that the indolepropionic acid grafted starch in step S3 is replaced by a physical mixture of indolepropionic acid and high-amylose starch.

[0133] Figure 2 It is a graph of the release rate of indolepropionic acid of indolepropionic acid grafted high-amylose starch in different pH solutions prepared in Examples 1-4 and Comparative Example 2 of the present invention; Figure 2 In Examples 1-3 under the same pH conditions, as the amount of indolepropionic acid grafted starch added gradually increases, the amount of indolepropionic acid released gradually increases, and the release rate at pH 5 is the largest. This is because the chemical bonds introduced in indolepropionic acid and high-amylose starch are pH-responsive and are more easily broken to release indolepropionic acid under pH 5. Among them, the release rate of Example 2 is the highest. This is because when the mass ratio is 5:1, the double network gel microsphere structure formed by sodium alginate and indolepropionic acid grafted starch is more compact, which can better protect indolepropionic acid from damage in a low acid environment. In Example 4, the release rate of indolepropionic acid is reduced. This is because the addition of polyphenols makes the system of gel microspheres more compact and limits the release of indolepropionic acid. The release rate of indolepropionic acid in Comparative Example 2 under pH 3 is significantly higher than that in Example 1. This is because sodium alginate is easy to form a gel network under low pH conditions to limit the overflow of indolepropionic acid, but the release of free indolepropionic acid is increased compared with Example 1, which is covalently connected to starch through acetal bonds. In addition, the IPA release rate increased at pH 5 and pH 7, but there was no significant pH-sensitive trend, which was due to the disintegration of the gel network of sodium alginate above pH 5, resulting in the overflow of the entrapped IPA. Figure 3 It is a particle size diagram of indolepropionic acid grafted high amylose starch / sodium alginate gel microspheres prepared in Examples 1-4 of the present invention; in Examples 1-3, as the content of indolepropionic acid grafted high amylose starch increases, the particle size gradually increases, because the formation of double network gel will increase the complexity of solvent fusion, resulting in an increase in solutes in the solution system and an increase in particle size. The particle size of Example 4 is smaller than that of Example 3 but larger than that of Example 2. This is because the addition of gallic acid makes the structure of the double network gel more compact, so the particle size is smaller than that of Example 3, but the addition of gallic acid makes the solution system more complex, so the particle size of the particles finally formed is slightly larger than that of Example 2. The particle size of Comparative Examples 1 and Comparative Examples 2 is significantly smaller than that of Examples 1-4, because compared with the chemically modified starch in the examples, the starch that has not been grafted with indolepropionic acid retains the physical and chemical properties of high amylose corn starch, and its swelling rate and gelatinization recovery performance are not changed, so the particle size of the prepared gel microspheres is smaller. Figure 4The cytotoxicity of the indolepropionic acid grafted high-amylose starch / sodium alginate solution in Examples 1-4 prepared by the present invention; Caco-2 cells were selected as model cells to measure the toxicity of the indolepropionic acid grafted high-amylose starch / sodium alginate solution. As the added concentration increased, the cell viability decreased slightly, but even when the concentration increased to 100 μ g / mL, the cell viability was still above 90%, with good cell safety. The cell viability of Example 4 at a concentration of 100 μ g / mL was 87.2%, which was due to the cytotoxicity of the release of gallic acid, resulting in reduced cell viability. In Comparative Examples 1 and 2, the effect on cytotoxicity as the concentration increased was negligible, with good cell safety.

[0134] Figure 5 This is a graph showing the release rate of gallic acid under different pH conditions in the indolepropionic acid grafted high-amylose starch / sodium alginate / gallic acid gel microspheres prepared in Example 4 of the present invention; the release rate of gallic acid is highest under a pH 5 environment, because gallic acid is encapsulated in the double-network gel microspheres composed of indolepropionic acid grafted starch and sodium alginate, and at pH 5, the acetal bond breaks, and the gel structure cleaves to release a large amount of gallic acid.

[0135] Figure 6 The figure is a graph showing the release rate of gallic acid in the indolepropionic acid grafted high amylose starch / sodium alginate / gallic acid gel microspheres prepared in Example 4 of the present invention under different temperature conditions. As the temperature increases, the amount of gallic acid released gradually increases, which is because the structure of the gel is unstable at high temperature, and the gelatinization of starch leads to the disintegration of the double network structure, thereby causing a large amount of gallic acid to be released.

[0136] In addition, the inventors of this case also referred to the aforementioned embodiments and conducted experiments with other raw materials, process operations, and process conditions described in this specification, and obtained relatively ideal results.

[0137] It should be understood that the technical solution of the present invention is not limited to the above-mentioned specific implementation cases. Any technical deformation made according to the technical solution of the present invention without departing from the scope of protection of the purpose of the present invention and the claims shall fall within the protection scope of the present invention.

Claims

1. A method for preparing double-network gel microspheres with pH response, characterized in that: include: Under the catalytic action of EDC and NHS, indolepropionic acid reacts with 2-hydroxyethyl vinyl ether to prepare indolepropionic acid-2-hydroxyethyl vinyl ether polymer; Under the catalytic action of p-toluenesulfonamide, the indolepropionic acid-2-hydroxyethyl vinyl ether polymer is reacted with high-amylose starch to prepare indolepropionic acid grafted starch; Furthermore, the indolepropionic acid grafted starch, sodium alginate and water are mixed as a dispersed phase; a solution containing a surfactant is used as a continuous phase, and then microfluidic technology is used to prepare double-network gel microspheres with pH response.

2. The preparation method according to claim 1, characterized in that: Specifically include: Indolepropionic acid, EDC, NHS and solvent are mixed and stirred at room temperature for 8-12 hours to form a mixed solution, and then 2-hydroxyethyl vinyl ether is added and stirred at 40-60° C. for 18-24 hours, and then dialyzed, centrifuged, washed and freeze-dried to obtain indolepropionic acid-2-hydroxyethyl vinyl ether polymer.

3. The preparation method according to claim 1, characterized in that: Specifically include: The high-amylose starch, indolepropionic acid-2-hydroxyethyl vinyl ether polymer, p-toluenesulfonamide and solvent were mixed and reacted at room temperature for 48 hours under stirring, and then dialyzed, centrifuged, washed and freeze-dried to obtain indolepropionic acid grafted starch.

4. The preparation method according to claim 1, characterized in that: Specifically include: Mixing indolepropionic acid grafted starch, sodium alginate and water to form a first mixed solution; forming a second mixed solution from a solution containing a surfactant; And, using microfluidic technology, the first mixed solution is passed into the first channel of the microfluidic chip as a dispersed phase, and the second mixed solution is passed into the second channel of the microfluidic chip as a continuous phase, and then the generated microspheres are allowed to stand and solidify in a calcium chloride solution to obtain double-network gel microspheres with pH response; Preferably, the inner diameter of the circular capillary used in the first channel of the microfluidic chip is 180-260 μm; preferably, the inner diameter of the circular capillary used in the second channel of the microfluidic chip is 120-200 μm.

5. Double-network gel microspheres with pH response prepared by the preparation method according to any one of claims 1 to 4.

6. Use of the pH-responsive double-network gel microspheres according to claim 5 in a drug delivery system.

7. A method for preparing a pH-responsive drug delivery system, characterized in that: include: Under the catalytic action of EDC and NHS, indolepropionic acid reacts with 2-hydroxyethyl vinyl ether to prepare indolepropionic acid-2-hydroxyethyl vinyl ether polymer; Under the catalytic action of p-toluenesulfonamide, the indolepropionic acid-2-hydroxyethyl vinyl ether polymer is reacted with high-amylose starch to prepare indolepropionic acid grafted starch; Furthermore, the indolepropionic acid grafted starch, sodium alginate and water are mixed as a dispersed phase; an oil solution containing at least a surfactant and polyphenols is used as a continuous phase, and then a pH-responsive drug delivery system is prepared using microfluidic technology.

8. The preparation method according to claim 7, characterized in that: Specifically comprising: mixing indolepropionic acid, EDC, NHS and a solvent and stirring at room temperature for 8-12 hours to form a mixed solution, then adding 2-hydroxyethyl vinyl ether and stirring at 40-60° C. for 18-24 hours, and then dialyzing, centrifuging, washing, and freeze-drying to obtain an indolepropionic acid-2-hydroxyethyl vinyl ether polymer; And / or, the preparation method specifically comprises: mixing high amylose starch, indolepropionic acid-2-hydroxyethyl vinyl ether polymer, p-toluenesulfonamide and a solvent and stirring the mixture at room temperature for 48 hours, followed by dialysis, centrifugation, washing and freeze-drying to obtain indolepropionic acid grafted starch; And / or, the preparation method specifically comprises: mixing indolepropionic acid grafted starch, sodium alginate and water to form a third mixed solution; forming a fourth mixed solution from an oil solution containing a surfactant and polyphenols; And, using microfluidic technology, the third mixed solution is passed into the first channel of the microfluidic chip as a dispersed phase, and the fourth mixed solution is passed into the second channel of the microfluidic chip as a continuous phase, and then the generated microspheres are allowed to stand and solidify in a calcium chloride solution to obtain double-network gel microspheres with pH response; Preferably, the inner diameter of the circular capillary used in the first channel of the microfluidic chip is 180-260 μm; preferably, the inner diameter of the circular capillary used in the second channel of the microfluidic chip is 120-200 μm.

9. The preparation method according to claim 7, characterized in that: The high-amylose starch includes any one or more combinations of high-amylose corn starch, high-amylose wheat starch, and isoamylase-hydrolyzed corn starch; And / or, the polyphenolic substances include any one or more combinations of gallic acid, ursolic acid, ferulic acid, berberine, magnolol, and coumarin; And / or, the surfactant includes any one or more combinations of Tween 80, Span 20, Span 40, and Span 60; And / or, the solvent comprises DMF and / or DMSO. And / or, the oil solution includes any one or more combinations of corn oil, soybean oil, palm oil, and sunflower oil.

10. A pH-responsive drug delivery system prepared by the preparation method according to any one of claims 7 to 9.

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