CN114983928B

CN114983928B - Zinc alginate gel for oral administration of insulin and preparation method thereof

Info

Publication number: CN114983928B
Application number: CN202210514185.2A
Authority: CN
Inventors: 李井雷; 吴海山; 国婷; 程浩然; 南剑; 张温清
Original assignee: Hefei University of Technology
Current assignee: Hefei University of Technology
Priority date: 2022-05-11
Filing date: 2022-05-11
Publication date: 2023-07-18
Anticipated expiration: 2042-05-11
Also published as: CN114983928A

Abstract

The invention discloses an oral insulin zinc alginate gel and a preparation method thereof, belonging to the technical field of biological pharmacy. Wherein, the preparation method comprises the following steps: dissolving gel filler in sodium alginate solution, sufficiently dissolving, sequentially dripping zinc insulin hexamer solution and zinc chloride salt acid solution, completely dripping, and stirring to form gel. According to the invention, the zinc insulin hexamer is used for replacing insulin, and is embedded in a zinc alginate gel system through a charge adsorption effect, and the gel filler is used for reducing the network pore diameter of the zinc alginate hydrogel, so that the stability and the storage property of the zinc insulin hexamer are improved, and the bioavailability of insulin is greatly improved. The preparation method disclosed by the invention is simple, the natural biological material is used, toxic and harmful chemical reagents are avoided, the carrying efficiency of insulin is high, the insulin is well protected from being damaged by gastrointestinal digestive juice, the slow release effect in intestines and stomach is good, and the biological activity is not changed after slow release.

Description

Zinc alginate gel for oral administration of insulin and preparation method thereof

Technical Field

The invention belongs to the technical field of biological pharmacy, and particularly relates to zinc alginate gel for oral insulin and a preparation method thereof.

Background

The oral route of administration is a non-invasive route of administration and oral insulin mimics the pharmacokinetic profile of endogenous insulin. In addition, oral insulin overcomes the problems associated with treating type 1 and type 2 diabetics by insulin injection and insulin pump therapy. However, oral insulin action requires overcoming both the enzyme barrier (leading to rapid degradation of insulin) and the permeation barrier (limiting the absorption of insulin by the small intestine). In order to achieve effective oral insulin delivery, several strategies have been proposed, including absorption enhancers, enzyme inhibitors, enteric coating gums, and nanoparticles. However, there is still a lack of effective oral insulin delivery systems.

Insulin is a protein hormone secreted by islet beta cells within the pancreas by stimulation with endogenous or exogenous substances such as glucose, lactose, ribose, arginine, glucagon, and the like. Insulin is the only hormone in the body that can lower blood sugar, promote the availability of glucose by cells throughout the body, and inhibit glycogenolysis and gluconeogenesis. Under normal conditions, insulin monomer is the active form of insulin, but it is easily degraded and destroyed by enzymes in the gastric and intestinal fluids and forms amyloid fibrils, thereby reducing biological activity and stimulating immunogenicity. Unlike insulin monomer, zinc ion (Zn ²⁺⁾ Forms stable insulin hexamer (Zn-INS) with insulin, has stronger resistance to enzymatic degradation of trypsin, and does not degrade. In pharmaceutical formulations, insulin is usually complexed with zinc ions, in the form of hexamers. Zinc has also been used to develop nanoparticle-based oral insulin delivery systems. Therefore, compared with insulin monomer, zinc insulin hexamer is more stable and not easy to be decomposed, thus being an ideal pharmaceutical preparation of oral insulin.

The hydrogel is used as a functional polymer, and has good application prospect in the fields of controlled release of medicines, gene transfer, tissue engineering and the like due to good biocompatibility and safety. Hydrogels can be divided into two types: synthetic hydrogels and natural hydrogels. The common polymers used for synthesizing the hydrogel are polyacrylic acid and derivatives thereof, and although the high-stability hydrogel has good stability, the high-stability hydrogel has weak biodegradation and biocompatibility and can generate certain toxic and side effects on human bodies, so that the application of the high-stability hydrogel in the aspect of controlling slow-release medicaments is limited to a certain extent. The raw materials of the natural hydrogel mainly comprise chitosan, sodium alginate, cellulose, starch and the like. These natural polysaccharides have good biocompatibility and biodegradability, are inexpensive and readily available, and can be formed into gel systems by physical or chemical methods. The hydrogel has a three-dimensional network structure, so that not only is enough space provided for external medicines, but also slow release can be controlled. Therefore, the polymer substances contained in the hydrogel particles can be combined with water molecules, so that the hydrogel has strong water holding capacity, and a plurality of hydrogel biomolecules can be fixed in the system for a long time.

The sodium alginate can be extracted from brown algae such as herba Zosterae Marinae or Sargassum, and its molecular chain is formed by connecting beta-D-mannuronic acid and alpha-L-guluronic acid. The aqueous solution of sodium alginate has a high viscosity and has been widely used as a thickener, a stabilizer, an emulsifier, etc. for foods. The ionization degree of the sodium alginate is reduced under the acidic condition, the hydrophilicity is reduced, the molecular chain is contracted, when the pH value is increased, the hydrophilicity is increased, and the molecular chain is in an expanded state. Thus, sodium alginate has a pronounced pH response. Sodium alginate and Ca ²⁺ ，Zn ²⁺ The isodivalent cations crosslink to form a network structure, forming a hydrogel. The alginic acid gel has mild formation condition, and can avoid inactivation of sensitive substances such as medicines, proteins, cells, enzymes and the like. Because of these excellent properties, sodium alginate has been widely used in the food industry and in the pharmaceutical field.

The alginic acid gel is used as a delivery system for oral administration of insulin, has remarkable advantages and application prospects, and the oral insulin gel delivery system based on the alginic acid gel system is few at present, so that research and development of an efficient and stable oral insulin nano delivery system are necessary.

Disclosure of Invention

The invention aims to provide zinc alginate gel for oral administration of insulin, which solves the problems in the background technology.

A zinc alginate gel for oral administration of insulin and a preparation method thereof are provided, which are used for solving the technical problems that insulin is easy to be degraded and has low biological activity when insulin is orally administered. The preparation method provided by the invention adopts an ion gel method and a charge adsorption method, has the advantages of simple preparation process, no toxic or harmful reagent material, high insulin stability, stable high-level structure and biological activity of insulin, good slow release effect, long blood sugar control time and wide application prospect.

The aim of the invention can be achieved by the following technical scheme:

a zinc alginate gel for oral administration of insulin comprising the steps of:

dissolving gel filler in sodium alginate solution, sufficiently dissolving, sequentially dripping zinc insulin hexamer solution and zinc chloride solution, completely dripping, and stirring to form gel.

Further, the mass ratio of the gel filler to the sodium alginate is 10:5-9, and the preferential mass ratio is 10:6-8.

Further, the gel filler is maltodextrin or beta-cyclodextrin.

Further, the weight ratio of zinc chloride to sodium alginate is 1:6.

Further, the weight ratio of the zinc insulin hexamer to the hydrogel is 1:10-200, and the zinc insulin hexamer can be adjusted according to the actual required concentration.

Further, the zinc insulin hexamer is prepared by the following steps:

under magnetic stirring, slowly dripping insulin solution and zinc chloride solution into phosphate buffer solution (PBS pH 7.4) at the same time, and stirring for 60min to obtain zinc insulin hexamer, wherein the molar ratio of insulin to zinc chloride is 1:9.

Further, the insulin solution is prepared by the steps of: insulin is dissolved in dilute hydrochloric acid or ultrapure water, phosphate buffer, DMSO, preferably dilute hydrochloric acid (pH 2.0).

Further, the concentration of insulin in the insulin solution is 1-2mg/mL, preferably 2mg/mL.

Further, the zinc chloride solution is prepared by the following steps: zinc chloride was dissolved in ultrapure water, phosphate buffer, DMSO, dilute hydrochloric acid.

Further, the solvent is preferably diluted hydrochloric acid (pH 4.7).

Further, the concentration of zinc chloride in the zinc chloride solution is 0.5-2mg/mL, preferably 2mg/mL.

Compared with the prior art, the invention has the following advantages:

1. the invention adopts natural biological materials as raw materials, has high biocompatibility, adopts a mild preparation method, has no toxic or harmful reagent, is environment-friendly, does not relate to large-scale precise instruments, and has lower requirements on instruments and equipment;

2. according to the invention, zinc insulin hexamer is used for replacing insulin, so that the biological activity of insulin can be better protected, and the stability and bioavailability of the insulin are improved;

3. the addition of maltodextrin or beta-cyclodextrin facilitates the formation of a dense lattice structure of the hydrogel. Insulin can be successfully retained in the hydrogel and released slowly after entry into the intestine. The prepared hydrogel remarkably improves the stability of insulin to digestive enzymes.

4. The prepared zinc alginate is used as a carrier of zinc insulin hexamer, can smoothly pass through gastric digestive juice, has high insulin stability, promotes the release of insulin in intestinal tracts, has good protective effect on insulin by a zinc alginate gel system, improves the bioavailability of the insulin, and has higher blood sugar reducing effect.

5. The zinc alginate gel for oral administration of insulin prepared by the invention can be orally administered by patients, and compared with injection, the zinc alginate gel for oral administration of insulin has the advantages of less pain for patients, no need of repeated administration and stable blood sugar control; the nanoparticle solution has good blood glucose reducing effect, long blood glucose reducing duration, obvious effect and high insulin bioavailability.

Drawings

The invention is further described below with reference to the accompanying drawings.

A perspective electron microscope view in embodiment 3 of fig. 1;

FIG. 2 is an external view showing zinc alginate gel of oral insulin prepared in example 2-3;

FIG. 3 is a scanning electron microscope image in example 3;

FIG. 4 is an infrared absorption spectrum (FTIR) of a zinc alginate gel containing cyclodextrin and maltodextrin;

FIG. 5 shows the thermal properties of zinc alginate gel containing cyclodextrin and maltodextrin measured by Differential Scanning Calorimetry (DSC);

FIG. 6 shows cytotoxicity of zinc alginate containing zinc insulin hexamer against HT29 (a) and Caco-2 (b);

FIG. 7 is a graph showing the release profile of insulin from zinc insulin hexamer zinc alginate gel at various pH conditions;

FIG. 8 is a graph showing the protective effect of zinc insulin hexamer zinc alginate gel on insulin under simulated digestion conditions;

FIG. 9 shows the results of insulin absorption by the small intestine at various times;

FIG. 10 shows OGTT results for hyperglycemia model mice under different treatments;

fig. 11 a is a graph showing the results of in vivo blood glucose reduction, and b is a graph showing the results of blood glucose AUC values.

Detailed Description

The technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

Example 1

Preparation of zinc insulin hexamer:

while magnetically stirring, slowly dropping insulin solution and zinc chloride solution into the solvent according to the ratio (molar ratio of insulin to zinc chloride) shown in table 1, magnetically stirring for 60min, and standing for later use.

Wherein the concentration of insulin in the insulin solution is 2mg/mL, and the insulin solution is formed by configuring insulin and a solvent. The concentration of zinc chloride in the zinc chloride solution is 0.5mg/mL, and the zinc chloride solution is formed by configuring zinc chloride and a solvent.

TABLE 1 preparation conditions of Zinc insulin hexamer solution

Example 2

Preparation of zinc alginate gel for oral administration of insulin:

dissolving gel filler in sodium alginate solution, adding zinc chloride solution dropwise after dissolving fully, and stirring to form gel.

Wherein the concentration of sodium alginate in the sodium alginate solution is 14mg/mL;

the zinc chloride solution is formed by preparing zinc chloride and dilute hydrochloric acid with the pH of 4.7, the concentration of the zinc chloride is 4mg/mL, and the weight ratio of the zinc chloride to the sodium alginate is 1:6; the weight ratio of zinc insulin hexamer to the hydrogel is 1:20.

Example 2-1: preparation of hydrogel formed by gel filler: the gel is prepared by the steps of the method, wherein the gel filler is maltodextrin, and the mass ratio of the maltodextrin to the sodium alginate is 10:6.

Example 2-2: preparation of hydrogel formed by gel filler: the gel is prepared by the steps of the method, wherein the gel filler is maltodextrin, and the mass ratio of the maltodextrin to the sodium alginate is 10:7.

Examples 2-3: preparation of hydrogel formed by gel filler: the gel is prepared by the steps of the method, wherein the gel filler is maltodextrin, and the mass ratio of the maltodextrin to the sodium alginate is 10:8.

FIG. 2 is a physical view of zinc alginate gel of oral insulin obtained in example 2-3.

Examples 2 to 4: preparation of hydrogel formed by gel filler: the gel is prepared by the steps of the method, wherein the gel filler is maltodextrin, and the mass ratio of the maltodextrin to the sodium alginate is 10:9.

Examples 2 to 5: preparation of hydrogel formed by gel filler: the gel is prepared by adopting the method steps, wherein the gel filler is beta-cyclodextrin, and the mass ratio of maltodextrin to sodium alginate is 10:6.

Examples 2 to 6: preparation of hydrogel formed by gel filler: the gel is prepared by adopting the method steps, wherein the gel filler is beta-cyclodextrin, and the mass ratio of maltodextrin to sodium alginate is 10:7.

Examples 2 to 7: preparation of hydrogel formed by gel filler: the gel is prepared by adopting the method steps, wherein the gel filler is beta-cyclodextrin, and the mass ratio of maltodextrin to sodium alginate is 10:8.

Examples 2 to 8: preparation of hydrogel formed by gel filler: the gel is prepared by adopting the method steps, wherein the gel filler is beta-cyclodextrin, and the mass ratio of maltodextrin to sodium alginate is 10:9.

Comparative example 1

Preparation of unfilled zinc alginate hydrogel:

the gel filler was removed compared to examples 2-3, the remainder being the same.

Comparative example 2

Preparation of blank zinc alginate hydrogel:

the gel filler and zinc insulin hexamer were deleted compared to examples 2-3, the remainder being the same.

Comparative example 3

Preparation of zinc alginate hydrogels containing bulking agents:

in comparison with examples 2-3, zinc insulin hexamer was deleted, the remainder being the same.

Example 3

Particle size, polydispersity and morphology characterization:

DLS detection of zinc insulin hexamer solution particle size, polydispersity and morphology of the zinc insulin hexamer solution prepared in example 1 were characterized:

the results of the particle size and the polydispersion coefficient are shown in Table 2, the particle size of the zinc insulin hexamer solution is 32.57 +/-6.52-269.60 +/-21.94 nm, and the polydispersion coefficient is 0.30+/-0.04-0.88+/-0.15.

The morphological result of the perspective electron microscope characterization is shown in fig. 1, wherein a is a perspective electron microscope image of insulin, and b is a perspective electron microscope image of zinc insulin hexamer obtained in examples 1-4; FIG. 1 b illustrates that zinc insulin hexamer is irregularly shaped, with a diameter around 200nm, similar to the DLS assay results.

The hydrogel samples obtained in examples 2-3, comparative example 2 and comparative example 3 were lyophilized for 72 hours, and after gold plating under vacuum for 20 minutes, the pretreatment was completed, and then the morphology of insulin hydrogel was observed under a scanning electron microscope acceleration voltage of 10.0kV, and the results are shown in fig. 3. FIG. 3 a shows the results of a zinc alginate gel (hydrogel obtained in comparative example 2) without insulin hexamer and maltodextrin filler; b is the result of zinc alginate gel without insulin hexamer and with maltodextrin filler (hydrogel obtained in comparative example 3); c is the result of zinc alginate gel (hydrogel obtained in examples 2-3) containing insulin hexamer and maltodextrin filler; d is the result (enlarged) of a zinc alginate gel (hydrogel obtained in examples 2-3) containing insulin hexamer and maltodextrin filler, with surface particles of insulin hexamer.

As is evident from fig. 3, the zinc alginate gel without zinc insulin hexamer has smooth surface, and the gaps in the gel system are remarkably reduced due to the addition of maltodextrin, and after zinc insulin hexamer is added, the surface of the gel is provided with obvious granular substances, and the particle size of the zinc insulin hexamer is basically consistent with the result of DLS detection, which indicates that the whole system is successfully prepared.

TABLE 2 particle size, polydispersity index and Zeta potential results of Zinc insulin hexamer obtained in example 1

	Particle size (nm)	PDI	Zeta(mV)
				Example 1-1	146.87±4.08	0.39±0.06	-9.71±0.44
Examples 1 to 2	179.20±2.06	0.37±0.02	-9.35±2.07
				Examples 1 to 3	170.97±13.60	0.30±0.04	-8.71±1.10
Examples 1 to 4	269.60±21.94	0.51±0.06	-13.80±0.33

Example 4

Determination of hydrogel physical properties: physical property measurement of hydrogels prepared in example 2 and comparative example 1: the obtained hydrogels were subjected to characterization measurement of viscosity-related physical properties by a physical property meter, and the obtained results are shown in table 3. As can be seen from the data in Table 3, the physical properties of the gel system are increased compared with that of the pure alginic acid hydrogel, and the fillers (maltodextrin and beta-cyclodextrin) of different types and the addition amount of the fillers have a remarkable influence on the physical properties, and as can be seen from the comprehensive analysis of the data in Table 2, the gel filler is preferably maltodextrin, and the mass ratio of maltodextrin to sodium alginate is preferably 20:16.

TABLE 3 physical Property results of Zinc alginate hydrogels

Example 5

Differential thermal analysis: the zinc alginate gel for oral administration of insulin prepared in example 2 was subjected to the following treatment, and the hydrogel sample was first freeze-dried, and the prepared hydrogel material was tested using a differential scanning calorimeter at a temperature ranging from-30 to 210 c, a heating rate of 10 c/min, and a flow rate of N2 of 50 mL/min, and the results were shown in fig. 4.

From fig. 4, it can be seen that the zinc alginate gel has good compatibility with dextrin, and is combined into a more stable structure by electrostatic force in the process of forming the hydrogel system, so that no redundant phase transition peak occurs, the main phase transition temperature is slightly increased, and better heat resistance is presented.

Example 6

And (3) infrared spectrum analysis: the zinc alginate gel for oral administration prepared in example 2 was subjected to the following treatment, the insulin hydrogel sample was freeze-dried, and the sample was subjected to an infrared absorption spectrum (ATR-FTIR) test at normal temperature, the wave number range of which was 400-4000cm ^-1 The results are shown in FIG. 5.

From fig. 5, it is shown that sodium alginate and zinc chloride form gel through ionic interaction, and meanwhile, the filler and alginic acid molecules mainly act in the form of hydrogen bonds, so that the strength of a gel system is improved, and the pores existing in the gel are filled.

Example 7

Cytotoxicity test: the following tests were performed on the oral insulin zinc alginate gel prepared in example 2:

the cytotoxicity of zinc alginate gel of oral insulin was examined by MTT method, and Caco-2 cells and HT29 cells were selected as the subjects. The viability of both Caco-2 cells and HT29 cells exceeded 96% over a wide concentration range, 0.077625-10mg/mL, and the results are shown in FIG. 6.

The data in fig. 6 show that zinc alginate gel of oral insulin is not toxic to cells even at higher concentrations. The zinc alginate gel of the oral insulin has good biocompatibility and can be applied to oral drug delivery.

Example 8

Simulation of gastrointestinal insulin release:

a simulated gastric fluid (pH 1.2) and a simulated intestinal fluid (pH 6.8) were prepared, and the oral insulin zinc alginate gel prepared in examples 2-3 was placed in the simulated gastric fluid and the simulated intestinal fluid, kept at 37℃and magnetically stirred, and the insulin content released in the simulated digestive fluid was detected by HPLC at any time, and the results were shown in FIG. 7.

The results of fig. 7 show that the amount of insulin released in simulated gastric fluid is small, with less than 20% of the insulin released over 2 hours of simulated release. In simulated intestinal fluid, the amount of insulin released is very fast, with about 80% of the insulin released over 2 hours of simulated release. The prepared zinc alginate gel has obvious pH corresponding release characteristics, can protect insulin from being damaged by gastric juice, but can be rapidly released in small intestine parts, thereby being beneficial to insulin absorption.

Example 9

Insulin stability:

1. preparation of simulated digestive juice

According to the pharmacopoeia and references, simulated gastric fluid and intestinal digestive fluid were prepared, the simulated gastric fluid having a pH of 1.2 and containing 10IU/mL pepsin, the simulated intestinal fluid having a pH of 6.8 and containing 10IU/mL trypsin. The zinc alginate gel of oral insulin prepared in examples 2-3 and ordinary insulin were placed in simulated gastric fluid and simulated intestinal fluid, respectively, and magnetically stirred at 37 degrees for 2 hours.

2. Insulin content detection

The result of the RP-HPLC detection of the insulin content in the digestive juice is shown in figure 8, the Hydrogel SGF is the persistence rate of oral insulin zinc alginate gel in simulated gastric juice, the Hydrogel SIF is the persistence rate of oral insulin zinc alginate gel in simulated intestinal juice, the Pure insulin SGF is the persistence rate of Pure insulin in simulated gastric juice, and the Pure insulin SIF is the persistence rate of Pure insulin in simulated intestinal juice.

The results of FIG. 8 show that under the action of pepsin and trypsin, the content of ordinary insulin is rapidly reduced, only about 10% of the original content remains after 2 hours of enzymolysis, and the zinc alginate gel better protects insulin from degradation, and about 50% of insulin remains after 2 hours of enzymolysis, which indicates that the zinc alginate gel can slow down the enzymolysis of insulin.

Example 10

Small intestine absorption test:

preparation of FITC-modified insulin: the 1% FITC ethanol solution was reacted with insulin solution (1 mg/mL) in the dark for 24 hours, and the unreacted FITC was removed by dialysis.

(II) detection of in vitro small intestine absorption process: taking small intestine of rat, cleaning the content, respectively binding two ends, injecting insulin solution and oral insulin zinc alginate gel group, standing in water bath at pH 7.8 and 37deg.C in dark for 2 hr to obtain small intestine tissue slice, and detecting insulin absorption by fluorescence confocal microscope, wherein the obtained result is shown in figure 9. In fig. 9, the first row is a zinc alginate gel group for oral insulin, and the second row is pure FITC-stained insulin;

the results of fig. 9 show that zinc alginate gel for oral administration of insulin effectively promotes absorption of insulin by small intestine and significantly improves absorption efficiency, compared with pure insulin.

Example 11

Construction of an STZ-induced diabetes mellitus mouse model: ICR mice were fed acclimatively for one week, after which the STZ-induced diabetes model was intraperitoneally injected with fasting blood glucose concentrations higher than 16.7mmol/L as a modeling standard. Model mice were fasted for 4-6 hours and were subjected to OGTT testing.

The test method comprises the following steps: according to the preparation method in examples 2-3, two concentrations of oral insulin zinc alginate gel (MD/Alg zinc alginate gel containing maltodextrin) were prepared, with concentration values of 20IU/kg and 50IU/kg;

orally taking glucose solution into fasted diabetes model mice, and perfusing the glucose solution into the mice with gel of the two concentrations; injecting insulin into the abdominal cavity of a fasted diabetes model mouse; the blood glucose level change of the above group model mice was measured, and the results are shown in FIG. 10.

From FIG. 10, it can be seen that the mice in the blank group and the experimental group have no obvious trend of decreasing blood glucose after rising, and basically are larger than 15mmol/L, which indicates that the drug cannot improve the function of islet beta cells in regulating blood glucose level in vivo.

Example 12

In vivo hypoglycemic experiments:

according to the preparation method in examples 2-3, two concentrations of oral insulin zinc alginate gel (MD/Alg zinc alginate gel containing maltodextrin) were prepared, with concentration values of 20IU/kg and 50IU/kg;

then, injecting the saline physiological saline, insulin into the fasted diabetes model mice in the abdominal cavity; the results of examining diabetic model mice after gastric administration and fasting of MD/Alg maltodextrin-containing zinc alginate gel, zinc insulin hexamer-containing zinc alginate gel (Zn/Alg) without maltodextrin were shown in FIG. 11.

The results in FIG. 11 demonstrate that MD/Alg of zinc alginate gel containing maltodextrin (20 IU/kg body weight) entered the mice, started to exert a significant hypoglycemic effect at 6h, and after the effect continued for 12h, demonstrated a significant slow release effect. MD/Alg zinc alginate gel containing maltodextrin (50 IU/kg body weight) entered the body, started to exert significant hypoglycemic effect after 4h, and the effect continued until after 12 h. Compared with a positive control group (saline physiological saline, insulin intraperitoneal injection, zinc insulin hexamer-containing, maltodextrin-free zinc alginate gel (Zn/Alg)), the zinc alginate gel (20, 50 IU/kg) with MD/Alg containing maltodextrin has a remarkable hypoglycemic effect, can protect insulin from being destroyed by stomach and small intestine, and can be absorbed by small intestine to reduce blood sugar, and has the hypoglycemic effect for at least 6 hours. The oral islet slow-release hydrogel has obvious hypoglycemic effect and insulin release delaying effect on a hyperglycemia mouse model, and has good biocompatibility.

It is noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims

1. A method for preparing an oral insulin zinc alginate gel, comprising the steps of:

dissolving gel filler in sodium alginate solution, sequentially dripping zinc insulin hexamer solution and zinc chloride solution after dissolving, and stirring to form gel after dripping completely;

the mass ratio of the gel filler to the sodium alginate is 10:5-9;

the gel filler is maltodextrin or beta-cyclodextrin.

2. The method for preparing the zinc alginate gel for oral administration of insulin according to claim 1, wherein the mass ratio of the gel filler to the sodium alginate is 10:6-8.

3. A zinc alginate gel for oral administration of insulin prepared by the method of any one of claims 1 to 2.