An oral delivery system for cationic-based polypeptides bridged by calcium ions or borate ester bonds

Abstract

This invention discloses a cationic peptide oral delivery system bridged by calcium ions or borate ester bonds. The raw materials include a therapeutic peptide, a cationic polymer, a calcium salt, and an alginate polysaccharide, optionally with the addition of 4-[(trimethylamino)methyl]phenylboronic acid. The calcium ions of the calcium salt and / or 4-[(trimethylamino)methyl]phenylboronic acid bridge the therapeutic peptide and the cationic polymer to form a peptide-cationic polymer ion-pair complex, serving as the core. A shell formed by ion cross-linking of the alginate polysaccharide and the calcium ions of the calcium salt encapsulates the core. This cationic peptide oral delivery system possesses anti-aggregation stability, active absorption promotion, and pH-responsive protection functions.

Description

Technical Field

[0001] This invention relates to the field of pharmaceutical formulation technology, and more particularly to an oral delivery system for cationic polypeptides bridged by calcium ions or borate ester bonds. Background Technology

[0002] Diabetes mellitus (DM) is a multifactorial chronic health disease caused by various genetic and environmental factors, with type 2 diabetes mellitus (T2DM) accounting for more than 90% of all diabetes cases. Therefore, researching the pathological mechanisms and effective treatments for T2DM is of great significance and urgency.

[0003] Glucagon-like peptide-1 (GLP-1) analogues such as exenatide, liraglutide, and semaglutide have shown significant efficacy in the treatment of type 2 diabetes and obesity, and are mainly administered by injection in clinical practice.

[0004] Oral administration is a more convenient route of administration with higher patient compliance; however, the oral bioavailability of peptide drugs is extremely low, and their clinical application has long faced multiple physiological barriers. The main reasons are: (1) the highly acidic environment of the stomach leads to the inactivation of peptide drugs; (2) the abundant proteases in the intestine (such as trypsin) rapidly degrade peptides.

[0005] Core-shell hydrogel systems, as co-delivery carriers for oral peptide drugs, exhibit unique advantages in achieving time-sequential release and targeted protection, making them a promising research direction in this field. Currently, hydrogel carriers based on natural polymers (such as sodium alginate and chitosan) are widely studied for the delivery of oral peptide drugs due to their good biocompatibility, biodegradability, and pH-responsive properties. These systems mainly achieve intestinal targeted release through physical encapsulation and pH-triggered swelling / disintegration. However, existing technologies still have significant shortcomings: the carrier often swells rapidly in the intestinal environment due to pH changes, leading to drug "burst release."

[0006] In addition to challenges such as the adverse gastrointestinal environment and low absorption efficiency, the inherent aggregation tendency of GLP-1 analogues is another key bottleneck limiting their delivery efficiency. These peptides readily form oligomers and even higher-order aggregates in solution through hydrophobic interactions or hydrogen bonds. This not only reduces the effective concentration of the monomeric drug and weakens its biological activity but also hinders its absorption by the intestinal epithelium. Therefore, improving the dispersion state of GLP-1 analogues during delivery is one of the key prerequisites for enhancing their oral absorption efficiency.

[0007] Cationic polymers (such as chitosan and its derivatives, PAMAM (polyamide-amine dendritic polymer), and polylysine) are widely used in oral peptide delivery systems. Their mechanisms of action include: (1) binding to negatively charged peptides through electrostatic interactions, inhibiting the self-aggregation behavior between peptide molecules, maintaining their monodisperse state, thereby increasing the effective concentration of drugs on the intestinal epithelial surface; (2) cationic polymers can open the tight junctions between intestinal epithelial cells, promoting the cellular bypass transport of peptides. At the same time, some cationic materials also act as absorption promoters, interacting with cell membranes or providing mucosal adhesion properties, promoting the absorption efficiency of drugs in intestinal epithelial cells and prolonging the retention time. However, when cationic polymers are used alone, the stability of peptide-polymer complexes is often insufficient. They are easily dissociated under the complex ionic environment and enzymatic conditions of the gastrointestinal tract, leading to peptide reaggregation or degradation, which limits their protective and delivery efficacy. Summary of the Invention

[0008] To overcome the problems of easy aggregation and low transmembrane absorption efficiency of existing oral peptide delivery systems, this invention provides a cationic peptide oral delivery system bridged by calcium ions or borate ester bonds. The cationic peptide oral delivery system of this invention has the functions of anti-aggregation stability, active absorption promotion and pH-responsive protection.

[0009] The technical solution of the present invention is as follows: A cationic peptide oral delivery system, comprising therapeutic peptides, cationic polymers, calcium salts, and alginate polysaccharides; Calcium salts bridge therapeutic peptides with calcium ions, forming peptide-cationic polymer ion-pair complexes, which serve as the core. The outer shell formed by the ionic cross-linking of alginate polysaccharides and calcium ions of calcium salts covers the core.

[0010] In this invention, calcium salts play a dual crucial role, providing core support for the construction of the delivery system. On the one hand, calcium ions (Ca... 2+ The introduction of Ca can significantly enhance the stability of the interaction between therapeutic peptides and cationic polymers. 2+Calcium salts can bridge the carboxylic acid groups in peptide molecules with the amino or phosphate groups on cationic polymers, forming a tighter ion-coordination network that effectively inhibits peptide aggregation and premature release in acidic or enzymatic environments. On the other hand, calcium ions can undergo rapid ion cross-linking reactions with alginate polysaccharides (such as sodium alginate) to form a classic "egg-box" structure hydrogel. This characteristic integrates the dual function of calcium salts into oral peptide delivery systems based on cationic polymers and hydrogels. Calcium salts act as a stabilizer to enhance the anti-aggregation ability of peptide-cationic polymer complexes and as a cross-linking agent to bind with alginate polysaccharide solutions, forming a pH-responsive shell or monolithic hydrogel framework. This hydrogel system can protect therapeutic peptides from gastric acid degradation and allows for controlled swelling and drug release in the intestinal pH environment.

[0011] This invention achieves highly stable loading, time-sequential protection, and efficient delivery of therapeutic peptides through a multi-component synergistic design combining cationic polymers with calcium salt bridging and alginate-based hydrogels. First, the system binds negatively charged therapeutic peptides to the cationic polymers via electrostatic interactions, inhibiting peptide self-aggregation. The calcium ions in the calcium salts stabilize the interaction between the peptides and the cationic polymers while simultaneously forming a cross-linked, pH-responsive hydrogel framework with alginate polysaccharides. This framework remains intact in the strongly acidic environment of the stomach to protect the peptides from acid degradation, and upon entering the neutral or weakly alkaline environment of the intestines, it allows for controlled swelling and slow release of the peptide complex.

[0012] Preferably, in the cationic peptide oral delivery system, the mass ratio of therapeutic peptide, cationic polymer material, calcium salt, and alginate polysaccharide is 1:1~6:10~20:20~30, based on raw materials.

[0013] In a further preferred embodiment, based on raw materials, the mass ratio of therapeutic peptide, cationic polymer material, calcium salt, and alginate polysaccharide in the cationic peptide oral delivery system is 1:3~4:10~20:20~30.

[0014] More preferably, in the cationic peptide oral delivery system, the mass ratio of therapeutic peptide, cationic polymer material, calcium salt, and alginate polysaccharide is 1:3~4:15:25 based on raw materials.

[0015] Preferably, the therapeutic polypeptide is selected from at least one of exenatide, semaglutide, and liraglutide.

[0016] More preferably, the therapeutic polypeptide is selected from exenatide. Exenatide is the first GLP-1 receptor agonist approved for clinical use and is one of the first-line drugs for the treatment of type 2 diabetes. Currently, exenatide injection and sustained-release microspheres are available on the market.

[0017] Preferably, the cationic polymer material is selected from chitin-based polysaccharides or PAMAM (polyamide-amine dendritic polymer); the chitin-based polysaccharide is selected from at least one of chitosan, chitosan oligosaccharides, quaternary ammonium chitosan, hydroxyethyl chitosan, hydroxypropyl chitosan, carboxymethyl chitosan, mercapto chitosan, galactosylated chitosan, and polyethylene glycol-grafted chitosan; the PAMAM is selected from at least one of G1 PAMAM, G2 PAMAM, G3 PAMAM, and G4 PAMAM.

[0018] G1 PAMAM, G2 PAMAM, G3 PAMAM, and G4 PAMAM are different generations of PAMAM products.

[0019] More preferably, the cationic polymeric material is chitosan oligosaccharide.

[0020] Existing chitosan and calcium / sodium alginate formulations mainly focus on passive protection and active enzyme inhibition mechanisms to design oral peptide delivery. The key point of this invention is to overcome the oral barrier through multiple synergistic mechanisms of "inhibiting peptide self-aggregation, bridging to enhance stability and chitosan oligosaccharide promoting transmembrane absorption". In this invention, chitosan oligosaccharide is irreplaceable compared to chitosan: (1) Chitosan oligosaccharide has a small molecular weight and moderate charge density, which can form uniform nanoparticle pairs with GLP-1 peptide analogs such as exenatide and inhibit peptide self-aggregation. In contrast, chitosan has a large molecular weight and high viscosity, which can easily form heterogeneous complexes with peptides, leading to increased particle size and aggregation. (2) Chitosan dissolves only under acidic conditions, while chitosan oligosaccharide has excellent water solubility across the entire pH range. In the preparation process, insoluble calcium salts need to be introduced to load the ion pairs of peptide-cationic polymer materials. If chitosan is used, the insoluble calcium salt carrier will degrade, making it impossible to prepare the final formulation. Loading insoluble calcium salts is also a crucial step. On the one hand, it is used to avoid direct contact between the peptide-cationic polymer ion pairs and sodium alginate, which would lead to cross-linking of the cationic polymer and sodium alginate. On the other hand, it enables the ion pairs to enter the calcium salt channels and optimize the in vivo time-sequential release behavior.

[0021] Chitosan oligosaccharides can adhere to intestinal mucus, open tight junctions of intestinal epithelial cells, and interact with the phospholipid bilayer of cell membranes, thereby promoting drug uptake and absorption and improving oral bioavailability and efficacy.

[0022] More preferably, the molecular weight of the chitosan oligosaccharide is ≤2000 Da. Chitosan oligosaccharides in this molecular weight range have excellent water solubility, strong transepithelial transcellular ability, and moderate surface positive charge density, which can effectively bind to negatively charged therapeutic peptides, resulting in better safety and delivery efficiency.

[0023] More preferably, the cationic polymer material is G2 PAMAM dendrimer.

[0024] G2 PAMAM dendritic macromolecules have moderate nanoscale size, good hydrophilicity and low cytotoxicity, which facilitates penetration of the intestinal mucus barrier. At the same time, they can reversibly regulate the tight junctions of intestinal epithelial cells, promote drug transmembrane transport, and improve the oral bioavailability and efficacy of drugs.

[0025] Preferably, the calcium salt is selected from at least one of calcium carbonate, calcium phosphate, calcium hydrogen phosphate, calcium oxalate, calcium sulfate, calcium sulfite, calcium tartrate, and calcium citrate.

[0026] More preferably, the calcium salt is calcium carbonate.

[0027] As an insoluble calcium salt, calcium carbonate can slowly release calcium ions within the delivery system, avoiding the rapid and violent cross-linking of alginate polysaccharides caused by rapid release, thereby forming a hydrogel framework with a uniform structure and good stability. At the same time, the slowly released calcium ions can fully enhance the interaction between therapeutic peptides and cationic polymer materials.

[0028] Preferably, the alginate polysaccharide is selected from at least one of sodium alginate, potassium alginate, ammonium alginate, and propylene glycol sodium alginate.

[0029] More preferably, the alginate polysaccharide is sodium alginate. Alginate ions combine with calcium ions to form calcium alginate gel, protecting the formulation from damage by gastric acid and gastrointestinal proteases, improving the stability of the nano-formulation, and enhancing its biocompatibility.

[0030] More preferably, the viscosity of the sodium alginate is 100~1000 mPa·s.

[0031] The present invention also provides a method for preparing the aforementioned cationic peptide oral delivery system, comprising the following steps: (1) Dissolve the therapeutic polypeptide in the first solvent and adjust the pH to 6.0-6.5 to obtain the first solution; dissolve the cationic polymer in the second solvent and adjust the pH to 6.0-6.5 to obtain the second solution; dissolve the alginate polysaccharide in the third solvent to obtain the third solution; (2) The second solution is added dropwise to the first solution, and the reaction is stirred to obtain a solution of polypeptide-cationic polymer ion-pair complex; (3) Add calcium salt to the solution of polypeptide-cationic polymer ion-pair complex, mix evenly, and vacuum dry to obtain ion-pair complex-calcium salt preparation; (4) Add the ion-pair complex-calcium salt preparation to the third solution and stir evenly to obtain the ion-pair complex-calcium salt gel preparation, which is the cationic polypeptide oral delivery system.

[0032] In the first solution, the concentration of the therapeutic peptide is 1-10 mg / mL; in the second solution, the concentration of the cationic polymer is 1-5 mg / mL.

[0033] The first and third solvents are water. The second solvent is selected according to the type of cationic polymer: when the cationic polymer is at least one of chitosan, hydroxyethyl chitosan, and hydroxypropyl chitosan, the second solvent is preferably a 1% (v / v) acetic acid solution; when the cationic polymer is at least one of chitosan oligosaccharide, quaternary ammonium salt chitosan, carboxymethyl chitosan, and polyethylene glycol grafted chitosan, the second solvent is preferably water; when the cationic polymer is PAMAM, the second solvent is preferably water or methanol.

[0034] Preferably, in the polypeptide-cationic polymer ion-pair complex, the mass ratio of the therapeutic polypeptide to the cationic polymer is 1:1 to 6; more preferably, it is 1:3 to 4.

[0035] Preferably, in step (2), the stirring speed of the stirring reaction is 200~600 rpm and the stirring reaction time is 4~12h.

[0036] Preferably, in step (3), the vacuum drying temperature is 30~40℃, the vacuum drying time is 8~12h, and the vacuum degree is -0.1~-0.05MPa; more preferably, the vacuum drying temperature is 33℃, the vacuum drying time is 9h, and the vacuum degree is -0.09MPa.

[0037] Preferably, the concentration of alginate polysaccharides in the third solution is 1-10 mg / mL. This concentration of alginate polysaccharide solution has a moderate viscosity, which facilitates thorough mixing with the ion-pair complex-calcium salt preparation and allows for the formation of a hydrogel with a uniform structure and suitable mechanical strength under the action of calcium ions.

[0038] When adding calcium salt in step (3), you can choose to add the finished calcium salt directly, or add the corresponding soluble sodium salt and calcium chloride, and generate insoluble calcium salt in situ. Both methods can achieve the slow release and cross-linking function of the loaded polypeptide-cationic polymer material ion-pair complex and calcium ions.

[0039] In a preferred embodiment, the cationic peptide oral delivery system is prepared by loading an ion-pair complex of exenatide (EXE) and chitosan oligosaccharide (COS) or G2 PAMAM dendrimer onto calcium carbonate (CaCO3) and then dispersing it in a sodium alginate (ALG) solution. In the cationic peptide oral delivery system, the weight percentage of exenatide is 1% to 10%, the weight percentage of calcium carbonate is 10% to 50%, the molecular weight of chitosan oligosaccharide is 1 to 2000 Da, and the viscosity of sodium alginate is 100 to 1000 mPa·s.

[0040] The present invention also provides a preferred technical solution: A cationic peptide oral delivery system, comprising therapeutic peptides, cationic polymers, 4-[(trimethylamino)methyl]phenylboronic acid, calcium salts, and alginate polysaccharides; 4-[(trimethylamino)methyl]phenylboronic acid bridges therapeutic peptides and cationic polymers to form peptide-cationic polymer ion-pair complexes, serving as the core; The outer shell formed by the ionic cross-linking of alginate polysaccharides and calcium ions of calcium salts covers the core.

[0041] The structure of 4-[(trimethylamino)methyl]phenylboronic acid is shown in formula (I): .

[0042] 4-[(trimethylamino)methyl]phenylboronic acid possesses both a cationic quaternary ammonium group and a phenylboronic acid recognition group, serving as a dual-function linker. Its positively charged quaternary ammonium structure can bind to anionic therapeutic peptides through electrostatic interactions, inhibiting peptide aggregation and improving their dispersibility and structural stability. Simultaneously, the phenylboronic acid group can specifically interact with the ortho-hydroxyl structures on the surface of some cationic polymers (such as chitosan and chitosan oligosaccharides), achieving directional bridging between peptides and polymer carriers. This bifunctional small molecule, possessing both electrostatic binding and specific recognition capabilities, can effectively enhance the binding strength between peptides and cationic polymer carriers.

[0043] The delivery system of this invention incorporates a novel bifunctional small molecule compound, 4-[(trimethylamino)methyl]phenylboronic acid, to enhance the binding strength between peptides and cationic polymeric material carriers. The cationic polymeric material promotes absorption in the intestinal epithelium by increasing cell membrane fluidity, reversibly regulating tight junctions in the intestinal epithelium, and providing mucosal adhesion. This facilitates peptide absorption and transport, prolongs retention time, and ultimately systematically overcomes multiple barriers to oral delivery, significantly improving the oral bioavailability of therapeutic peptides.

[0044] Preferably, the molar ratio of 4-[(trimethylamino)methyl]phenylboronic acid to the therapeutic peptide is 5-7:1.

[0045] Preferably, in the cationic peptide oral delivery system, the mass ratio of therapeutic peptide, cationic polymer material, 4-[(trimethylamino)methyl]phenylboronic acid, calcium salt, and alginate polysaccharide is 1:1~6:5~7:10~20:20~30, based on raw materials.

[0046] In a further preferred embodiment, based on raw materials, the mass ratio of therapeutic peptide, cationic polymer material, 4-[(trimethylamino)methyl]phenylboronic acid, calcium salt, and alginate polysaccharide in the cationic peptide oral delivery system is 1:3~4:5~7:10~20:20~30.

[0047] More preferably, in the cationic peptide oral delivery system, the mass ratio of therapeutic peptide, cationic polymer material, 4-[(trimethylamino)methyl]phenylboronic acid, calcium salt, and alginate polysaccharide is 1:3~4:5~7:15:25 based on raw materials.

[0048] In the preferred technical solution, the preparation method of the cationic peptide oral delivery system includes the following steps: (1) Dissolve the therapeutic polypeptide in the first solvent and adjust the pH to 6.0-6.5 to obtain the first solution; dissolve the cationic polymer in the second solvent and adjust the pH to 6.0-6.5 to obtain the second solution; dissolve the alginate polysaccharide in the third solvent to obtain the third solution; dissolve 4-[(trimethylamino)]methylphenylboronic acid in the fourth solvent and adjust the pH to 6.0-6.5 to obtain the fourth solution; (2) Add the fourth solution dropwise to the first solution and stir to react, to obtain the reaction solution of the therapeutic polypeptide and 4-[(trimethylamino)methyl]phenylboronic acid; (3) The second solution was added dropwise to the reaction solution of the therapeutic peptide and 4-[(trimethylamino)]methylphenylboronic acid, and the reaction was stirred to obtain a solution of peptide-cationic polymer material ion pair complex; (4) Add calcium salt to the solution of polypeptide-cationic polymer ion-pair complex, mix well, and vacuum dry to obtain ion-pair complex-calcium salt preparation; (5) Add the ion-pair complex-calcium salt preparation to the third solution and stir evenly to obtain the ion-pair complex-calcium salt gel preparation, which is the cationic polypeptide oral delivery system.

[0049] Preferably, the preparation method of 4-[(trimethylamino)methyl]phenylboronic acid includes the following steps: (i) Dissolve 4-[(dimethylamino)-methyl]phenylboronic acid in dichloromethane, then add iodomethane, and stir the reaction at room temperature for 1-5 h; The mass ratio of iodomethane to 4-[(dimethylamino)-methyl]phenylboronic acid is 1~3:1; (ii) The product of step (i) is collected and recrystallized to obtain the 4-[(trimethylamino)methyl]phenylboronic acid.

[0050] 4-[(trimethylamino)methyl]phenylboronic acid was prepared by N-alkylation quaternization reaction of 4-[(dimethylamino)-methyl]phenylboronic acid with iodomethane in an organic solvent. This preparation method is mild, highly selective, and simple to operate, and can efficiently obtain the target bifunctional small molecule.

[0051] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention constructs and synthesizes a novel bridging small molecule compound, which has both cationic quaternary ammonium groups and phenylboronic acid recognition groups, and can be used as a dual-function linking unit. This overcomes the non-specific electrostatic interaction that the binding of peptides and cationic polymers in the prior art relies on, and provides a new molecular strategy for the binding of peptides and cationic polymers. (2) This invention effectively inhibits peptide self-aggregation and improves peptide dispersibility and complex stability through the synergistic effect of cationic polymer materials and optional novel bridging small molecules. (3) This invention utilizes the slow calcium release characteristics of insoluble calcium salts to achieve the dual effects of improving the stability of peptide-cationic polymer material ion pair complex and the mild cross-linking of hydrogel, while constructing a pH-responsive protective barrier. (4) The cationic polymer material in this invention has the functions of mucosal adhesion, tight junction regulation and cell membrane fluidity regulation, and promotes the absorption of polypeptides across the intestinal epithelium through multiple pathways. (5) The excipients used in this invention have excellent safety and biocompatibility, ensuring the safety of the drug delivery system and human tolerance, and are suitable for long-term use; (6) The preparation process of this invention is simple, the conditions are mild, the cost is low, no complicated equipment is required, it is easy to achieve large-scale production, and it has good clinical translation potential. Attached Figure Description

[0052] Figure 1 Transmission electron microscopy images of exenatide-chitosan oligosaccharide ion-pair complexes with different composition ratios prepared in Example 1, where (a)-(g) correspond to formulations 1-7, respectively; Figure 2 Transmission electron microscopy images of exenatide-G2 PAMAM ion-pair complexes with different composition ratios prepared in Example 2, where (a)-(g) correspond to formulations 8-14, respectively. Figure 3 The exenatide-chitosan oligosaccharide prepared in Example 1 and the exenatide-chitosan oligosaccharide-CaO prepared in Example 3 2+ Molecular simulation characterization results of ion-pair complexes; where (a) and (b) are exenatide-chitosan oligosaccharide and exenatide-chitosan oligosaccharide-Ca, respectively. 2+ The molecular dynamics simulation results are shown in (c) and (d), which are the curves of the Coulomb short-range potential (Coul-SR) and Lanner-Jones short-range potential (LJ-SR) changing with time during the simulation process, respectively. Figure 4 Particle size distribution diagrams of the exenatide-chitosan oligosaccharide@calcium carbonate and exenatide-chitosan oligosaccharide@calcium carbonate / sodium alginate preparations prepared in Example 4; Figure 5 Transmission electron microscopy images of the exenatide-chitosan oligosaccharide@calcium carbonate and exenatide-chitosan oligosaccharide@calcium carbonate / sodium alginate preparations prepared in Example 4; Figure 6 The in vitro release results of the exenatide-chitosan oligosaccharide@calcium carbonate / sodium alginate preparation, exenatide-chitosan oligosaccharide@calcium carbonate, and exenatide prepared in Example 4 are shown in the figure. Figure 7 The intraday pharmacodynamic results are shown in the figure for the exenatide-chitosan oligosaccharide@calcium carbonate / sodium alginate preparation prepared in Example 4 and the exenatide@calcium carbonate / sodium alginate complex preparation prepared in Comparative Example 1. Figure 8 The 1H NMR spectra of 4-[(trimethylamino)methyl]phenylboronic acid, 4-[(dimethylamino)methyl]phenylboronic acid, and iodomethane prepared in Example 5 are shown below. Figure 9 Confocal fluorescence microscopy images of exenatide-chitosan oligosaccharide, exenatide-4-[(trimethylamino)methyl]phenylboronic acid-chitosan oligosaccharide, and exenatide uptake by cells; Figure 10 The graph shows the intraday pharmacodynamic results of the exenatide-4-[(trimethylamino)methyl]phenylboronic acid-chitosan oligosaccharide@calcium carbonate / sodium alginate formulation prepared in Example 6. Detailed Implementation

[0053] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer.

[0054] the term The term "mixing" refers to the process of uniformly distributing two or more components in a solution using stirring or heating methods known in the pharmaceutical field.

[0055] The term "w / v" refers to the mass concentration of a solute, expressed in grams, in 100 mL of water. 1% (w / v) means that the mass concentration of the solute is 1 g / 100 mL.

[0056] The term "release rate" refers to the rate and extent at which a drug is released from a sustained-release or controlled-release formulation in a specified solvent.

[0057] The term "particle size distribution" refers to the number of particles in a formulation solution within different particle size ranges, as measured using a laser particle size analyzer.

[0058] Example 1 Preparation of exenatide-chitosan oligosaccharide ion pair complex 1. Prescription Table 1. Composition and ratio of exenatide-chitooligosaccharide ion-pair complex

[0059] 2. Preparation of exenatide-chitosan oligosaccharide ion pair complex (1) Weigh exenatide and chitosan oligosaccharide in different proportions according to the dosage in Table 1, and dissolve them in deionized water respectively; (2) Under stirring at 400 rpm, chitosan oligosaccharide solutions of different proportions were added dropwise to exenatide solution, and the mixture was stirred at 400 rpm for 10 hours to obtain exenatide-chitosan oligosaccharide ion pair complex (EXE-COS).

[0060] Transmission electron microscopy (TEM) was performed on the exenatide-chitosan oligosaccharide ion-paired complex in Example 1. Figure 1 In formulations 1 and 2, the samples exhibited linear aggregated structures, indicating low binding efficiency between exenatide and chitosan oligosaccharide at this ratio, leading to peptide self-aggregation. Formulations 3-7 formed exenatide-chitosan oligosaccharide ion-pair complex nanoparticles. Among them, the ion-pair complex of formulation 5 consisted of uniform, near-spherical nanoparticles with a consistent particle size distribution and no obvious aggregation or fusion, indicating that the electrostatic binding between exenatide and chitosan oligosaccharide was most complete at this ratio, effectively inhibiting peptide self-aggregation and forming a stable complex with good monodispersity. Therefore, the composition ratio of formulation 5 (exenatide to chitosan oligosaccharide mass ratio of 1:4) was selected as the optimal condition for the subsequent delivery system construction.

[0061] Example 2 Preparation of exenatide-G2 PAMAM ion pair complex 1. Prescription Table 2 Composition ratio of exenatide-G2 PAMAM ion pair complex

[0062] 2. Preparation of exenatide-G2 PAMAM (Maclean, PAMAM dendrimer, ethylenediamine core, generation 2.0) ion-pair complex (1) Weigh exenatide and G2 PAMAM in different proportions according to the dosage in Table 2, and dissolve them in deionized water respectively; (2) Under stirring at 400 rpm, G2 PAMAM solutions of different proportions were added dropwise to exenatide solution and stirred at 400 rpm for 10 hours to obtain exenatide-G2 PAMAM ion pair complex (EXE-G2 PAMAM).

[0063] Transmission electron microscopy was performed on the exenatide-G2 PAMAM ion-paired complex in Example 2. Figure 2 In formulations 8 and 9, the samples exhibited linear aggregated structures, indicating low binding efficiency of exenatide and G2 PAMAM at this ratio, with the peptide undergoing self-aggregation. Formulations 12-14, with their high proportion of G2 PAMAM, showed increased size or secondary aggregation. Formulations 10-11 formed exenatide-G2 PAMAM ion-pair complex nanoparticles. Formulation 10 showed a wider particle size distribution, while formulation 11 exhibited uniformity and good dispersibility. Therefore, formulation 11 (exenatide to G2 PAMAM mass ratio of 1:3) was preferred as the optimal ratio for the binding of the exenatide-G2 PAMAM ion-pair complex.

[0064] Example 3 Exenatide-Chitosan Oligosaccharide-Ca 2+ Preparation of ion-pair complexes 1. Prescription Table 3. Exenatide-Chitosan Oligosaccharide-Ca 2+ Ion-pair complex composition ratio

[0065] 2. Exenatide-Chitosan Oligosaccharide-Ca 2+ Preparation of ion-pair complexes (1) Weigh out the corresponding proportions of exenatide, chitosan oligosaccharide and calcium chloride according to the dosage in Table 3, and dissolve them in deionized water respectively; (2) Under stirring at 400 rpm, the chitosan oligosaccharide solution was added dropwise to the exenatide solution, and the mixture was stirred at 400 rpm for 10 hours to obtain the exenatide-chitosan oligosaccharide ion pair complex. Then, calcium chloride solution was added dropwise and mixed thoroughly to obtain the exenatide-chitosan oligosaccharide-Ca complex. 2+ Ion-pair complexes.

[0066] The exenatide-chitosan oligosaccharide ion pair complex (Formulation 5) preferred in Example 1 and the exenatide-chitosan oligosaccharide-Ca complex in Example 3 2+Molecular simulation of ion-paired complexes. For example... Figure 3 As shown, when exenatide and chitosan oligosaccharide bind electrostatically, some polypeptide molecules remain in a free state. The introduction of calcium ions promotes the formation of an exenatide-chitosan oligosaccharide-CaO with a stoichiometric ratio of 4:16. 2+ Ion-pair complexes. Changes in the interaction energies of LJ-SR (Lanna-Jones short-range interaction potential) and Coul-SR (Coulomb short-range interaction potential) indicate that the introduction of calcium ions significantly improves the binding affinity between the two and the structural stability of the complex.

[0067] Example 4 Preparation of exenatide-chitosan oligosaccharide@calcium carbonate / sodium alginate formulation (EXE-COS@CaCO3 / ALG) (1) Weigh 1 mg of exenatide, dissolve it in deionized water, adjust the pH to 6.0, and prepare an exenatide solution with a concentration of 5 mg / mL; (2) Weigh 4 mg of chitosan oligosaccharide, dissolve it in deionized water, adjust the pH to 6.0, and prepare a chitosan oligosaccharide solution with a concentration of 2.75 mg / mL; (3) Add the chitosan oligosaccharide solution dropwise to the exenatide solution according to the mass ratio of exenatide to chitosan oligosaccharide 1:4 (w / w), and stir for 10 hours under magnetic stirring at 400 rpm; (4) Add 15 mg of calcium carbonate powder to the exenatide-chitosan oligosaccharide solution obtained in step (3) and continue stirring to ensure thorough mixing; (5) The exenatide-chitosan oligosaccharide@calcium carbonate preparation obtained in step (4) was vacuum dried in a vacuum drying oven at 33 °C and -0.09 MPa for 9 hours; (6) Weigh 25 mg of sodium alginate, dissolve it in deionized water, and prepare a sodium alginate solution with a concentration of 5 mg / mL; (7) The exenatide-chitosan oligosaccharide@calcium carbonate preparation obtained in step (5) was dispersed in 1 mL of deionized water and added dropwise to sodium alginate solution. After stirring for 8 hours, the exenatide-chitosan oligosaccharide@calcium carbonate / sodium alginate preparation was finally obtained.

[0068] The particle size distribution of the exenatide-chitosan oligosaccharide@calcium carbonate and exenatide-chitosan oligosaccharide@calcium carbonate / sodium alginate formulations in Example 4 was investigated using a laser particle size analyzer. Figure 4 The average particle sizes of the exenatide-chitosan oligosaccharide@calcium carbonate and exenatide-chitosan oligosaccharide@calcium carbonate / sodium alginate formulations were 4.4 μm and 4.8 μm, respectively.

[0069] TEM observation was performed on the exenatide-chitosan oligosaccharide@calcium carbonate and exenatide-chitosan oligosaccharide@calcium carbonate / sodium alginate formulations in Example 4, such as... Figure 5 As shown, the results indicate that the formulation is spherical with a diameter of approximately 4 μm, consistent with the results obtained by the laser particle size analyzer.

[0070] The free exenatide solution, as well as the exenatide-chitosan oligosaccharide@calcium carbonate and exenatide-chitosan oligosaccharide@calcium carbonate / sodium alginate formulations from Example 4, were divided into nine 2 mL portions, each added to a centrifuge tube containing 4 mL of pH 1.2 simulated gastric fluid. All centrifuge tubes were incubated in a 37 °C incubator with shaking. Samples were taken at 0, 0.5, 1, and 2 hours, and centrifuged at 10,000 rpm for 5 minutes. The supernatant was collected. At the 2-hour time point, the exenatide-chitosan oligosaccharide@calcium carbonate / sodium alginate formulation was transferred to a centrifuge tube containing 4 mL of pH 6.8 simulated intestinal fluid. The tubes were incubated in a 37 °C incubator with shaking. Samples were taken at 3, 4, 6, 8, and 12 hours, and centrifuged at 10,000 rpm for 5 minutes. The supernatant was collected. Three parallel experiments were conducted, and the concentration of exenatide was determined by high performance liquid chromatography (HPLC) to investigate the release of the formulation in simulated gastric and intestinal fluids.

[0071] The results are as follows Figure 6 As shown, exenatide solution and exenatide-chitosan oligosaccharide@calcium carbonate were almost completely released during incubation in simulated gastric fluid at pH 1.2. Under the same conditions, no significant exenatide release was detected in the exenatide-chitosan oligosaccharide@calcium carbonate / sodium alginate formulation. However, exenatide was gradually released after the formulation was transferred to simulated intestinal fluid at pH 6.8, indicating that the formulation has excellent pH-responsive release characteristics.

[0072] Comparative Example 1 Preparation of exenatide@calcium carbonate / sodium alginate formulation (EXE@CaCO3 / ALG) (1) Weigh 1 mg of exenatide, dissolve it in deionized water, adjust the pH to 6.0, and prepare an exenatide solution with a concentration of 0.6 mg / mL; (2) Add 15 mg of calcium carbonate powder to the exenatide solution and continue stirring to ensure thorough mixing; (3) The exenatide@calcium carbonate preparation obtained in step (2) was vacuum dried in a vacuum drying oven at 33 °C and -0.09 MPa for 9 hours; (4) Weigh 25 mg of sodium alginate, dissolve it in deionized water, and prepare a sodium alginate solution with a concentration of 5 mg / mL; (5) The exenatide@calcium carbonate preparation obtained in step (3) was rapidly dispersed in 1 mL of ultrapure water, and the preparation was added dropwise to sodium alginate solution. After stirring for 8 hours, the exenatide@calcium carbonate / sodium alginate preparation was finally obtained.

[0073] Twenty db / db mice were randomly divided into four groups of five each. The mice were fasted overnight but allowed free access to water. The groups were labeled as follows: blank control group, subcutaneous exenatide solution injection group, oral exenatide-chitosan oligosaccharide@calcium carbonate / sodium alginate preparation group (EXE-COS@CaCO3 / ALG), and oral exenatide@calcium carbonate / sodium alginate compound preparation group (EXE@CaCO3 / ALG). The blank control group did not receive exenatide treatment but received an equal volume of saline orally. The subcutaneous exenatide injection group received exenatide at a dose of 40 µg / kg. The oral exenatide preparation group received exenatide via gavage at a dose of 400 µg / kg. Tail tip blood samples were collected at 0, 0.5, 1, 2, 3, 4, 6, and 8 hours after administration to measure blood glucose changes and plot blood glucose-time curves (e.g., [image missing]). Figure 7 (As shown in the image). The results showed that the exenatide-chitosan oligosaccharide@calcium carbonate / sodium alginate preparation group exhibited a significant hypoglycemic effect, with a statistically significant difference compared to the blank control group. Compared to the exenatide@calcium carbonate / sodium alginate compound preparation group, the exenatide-chitosan oligosaccharide@calcium carbonate / sodium alginate preparation group showed a more significant hypoglycemic effect. This is because after chitosan oligosaccharide binds to exenatide, it can inhibit the self-aggregation behavior between polypeptide molecules, maintain its monodisperse state, and increase the effective concentration of the drug on the intestinal epithelial surface. Chitosan oligosaccharide can also adhere to small intestinal mucus, opening the tight junctions of small intestinal epithelial cells, promoting drug uptake and absorption, thereby improving the oral bioavailability and efficacy of the drug. Furthermore, compared to the subcutaneous exenatide injection group, this oral preparation not only has a significant hypoglycemic effect but also a more sustained hypoglycemic effect.

[0074] Example 5 Synthetic method of 4-[(trimethylamino)methyl]phenylboronic acid (TMMPBA) (1) Weigh 393.87 mg of 4-[(dimethylamino)-methyl]phenylboronic acid (CAS: 70799-12-1) and dissolve it in dichloromethane, then place it in a 20 mL reaction flask; (2) Weigh 936.80 mg of potassium iodide using a syringe and refrigerate overnight. Add iodomethane to the 4-[(dimethylamino)-methyl]phenylboronic acid solution in one injection using a syringe, and stir the reaction at room temperature for 4 hours; (3) After the reaction is complete, filter to obtain the white precipitate obtained in step (2), and wash the precipitate with cold dichloromethane (3×5 mL); (4) Collect the product from step (3), dry it under vacuum, dissolve it in a small amount of methanol, and recrystallize it in pre-cooled diethyl ether to obtain the 4-[(trimethylamino)methyl]phenylboronic acid.

[0075] 1H NMR spectrum of 4-[(trimethylamino)methyl]phenylboronic acid ( 1 H NMR characterization Iodomethane, 4-[(dimethylamino)]methylphenylboronic acid, and 4-[(trimethylamino)methyl]phenylboronic acid from Example 5 were dissolved in deuterated methanol, respectively, for further processing. 1 H-NMR analysis. For example... Figure 8 As shown, the characteristic peak of iodomethane is at 2.16 ppm; in the NMR spectrum of 4-[(dimethylamino)methyl]phenylboronic acid, five characteristic peaks appear: 7.62 ppm and 7.28 ppm correspond to two sets of non-equivalent aromatic hydrogens (total 4H) on the benzene ring, respectively; 3.78 ppm is the methylene group (-CH2-N, 2H) directly bonded to the nitrogen atom, showing a single peak, consistent with the structural characteristics; 2.48 ppm is the two methyl groups (-N(CH3)2, 6H) on the dimethylamino group, also showing a single peak; the hydroxyl group (B-OH) bonded to the boron atom overlaps with the deuterated methanol solvent peak, appearing around 4.87 ppm; in the NMR spectrum of 4-[(trimethylamino)methyl]phenylboronic acid, five characteristic peaks appear, with the two sets of non-equivalent aromatic hydrogens on the benzene ring located at 7.78 ppm and 7.53 ppm, respectively. ppm, influenced by the strong electron-withdrawing inductive effect of quaternary ammonium cations, the methylene group (-CH2-N) attached to nitrogen. + The chemical shift of (CH3)3,2H) is significantly lower field shifted to 4.55 ppm, exhibiting a singlet. The peak at 3.08 ppm is due to the nine equivalent methyl groups (-N) on the trimethylamino group. + (CH3)3,9H). Above. 1 H-NMR analysis confirmed the structure of the target compound and proved that 4-[(trimethylamino)methyl]phenylboronic acid was successfully synthesized.

[0076] Example 6 Preparation of exenatide-4-[(trimethylamino)methyl]phenylboronic acid (TMMPBA)-chitosan oligosaccharide@calcium carbonate / sodium alginate (EXE-TMMPBA-COS@CaCO3 / ALG) (1) Weigh 1 mg of exenatide, dissolve it in deionized water, adjust the pH to 6.0, and prepare an exenatide solution with a concentration of 6.5 mg / mL; (2) Weigh 0.4 mg of the 4-[(trimethylamino)methyl]phenylboronic acid described in Example 3, dissolve it in deionized water, adjust the pH to 6.0, and prepare a 4-[(trimethylamino)methyl]phenylboronic acid solution with a concentration of 8.66 mg / mL; (3) According to the molar ratio of exenatide to 4-[(trimethylamino)methyl]phenylboronic acid of 1:6, the 4-[(trimethylamino)methyl]phenylboronic acid solution was added dropwise to the exenatide solution and stirred for 2 hours under magnetic stirring at 400 rpm; (4) Weigh 4 mg of chitosan oligosaccharide, dissolve it in deionized water, adjust the pH to 6.0, and prepare a chitosan oligosaccharide solution with a concentration of 2.75 mg / mL; (5) Add the chitosan oligosaccharide solution dropwise to the mixed solution of exenatide and 4-[(trimethylamino)methyl]phenylboronic acid according to the mass ratio of exenatide to chitosan oligosaccharide 1:4 (w / w), and stir for 10 hours under magnetic stirring at 400 rpm. (6) Add 15 mg of calcium carbonate powder to the exenatide-4-[(trimethylamino)methyl]phenylboronic acid-chitosan oligosaccharide obtained in step (5) and continue stirring to ensure thorough mixing; (7) The exenatide-4-[(trimethylamino)methyl]phenylboronic acid-chitosan oligosaccharide@calcium carbonate preparation obtained in step (6) was vacuum dried in a vacuum drying oven at 33 °C and -0.09 MPa for 9 hours; (8) Weigh 25 mg of sodium alginate, dissolve it in deionized water, and prepare a sodium alginate solution with a concentration of 5 mg / mL; (9) The exenatide-4-[(trimethylamino)methyl]phenylboronic acid-chitosan oligosaccharide@calcium carbonate preparation obtained in step (7) was rapidly dispersed in 1 mL of ultrapure water and added dropwise to sodium alginate solution. After stirring for 8 hours, the exenatide-4-[(trimethylamino)methyl]phenylboronic acid-chitosan oligosaccharide@calcium carbonate / sodium alginate preparation was finally obtained.

[0077] To further verify the promoting effects of exenatide-chitosan oligosaccharide and exenatide-TMMPBA-chitosan oligosaccharide disclosed in the invention on intestinal epithelial absorption, fluorescence confocal microscopy was used to observe exenatide (EXE) labeled with fluorescein isothiocyanate. FITC The uptake of Caco-2 in the intestinal epithelial cell model.

[0078] The experimental protocol was as follows: Caco-2 cells in the logarithmic growth phase were harvested and processed at a rate of 2 × 10⁻⁶ cells / year. 5 Caco-2 cells were seeded at a density of [number] cells / mL onto a confocal microscope slide. The cells were cultured at 37°C and 5% CO2 for 5 days. After culture, the culture medium was removed, and the Caco-2 cells were washed three times with PBS buffer. Then, EXE with the same FITC fluorescence intensity was added to each cell. FITC ,EXE FITC -COS and EXE FITC Incubate in TMMPBA-COS solution for 2 hours. After incubation, remove the drug-containing medium and wash three times with PBS. Then, fix the cells with 4% paraformaldehyde at room temperature for 15 minutes and wash three times with PBS. Finally, add anti-fluorescence quenching mounting medium (containing DAPI) and observe the cells under a laser confocal microscope.

[0079] like Figure 9 As shown, exenatide-chitosan oligosaccharide and exenatide-TMMPBA-chitosan oligosaccharide can significantly promote the uptake of exenatide by intestinal epithelial cells.

[0080] Figure 9 In the cellular uptake results, compared with the exenatide-chitosan oligosaccharide group, the fluorescence signal of the exenatide-TMMPBA-chitosan oligosaccharide group was more enriched on the cell membrane surface. The reason for this may be that after modification with 4-[(trimethylamino)methyl]phenylboronic acid (TMMPBA), the phenylboronic acid group carried by the carrier can specifically covalently bind to sialic acid highly expressed on the intestinal epithelial cell membrane surface and the cis-diol structure in membrane glycoproteins. Although this did not further enhance the endocytic uptake efficiency, the specific interaction between phenylboronic acid and glycosyl groups makes it easier for the formulation to anchor on the intestinal epithelial cell membrane surface, effectively prolonging the retention time of the formulation in the intestinal mucosa. Simultaneously, the electrostatic adsorption of quaternary ammonium cations to the cell membrane can further enhance the mucosal adhesion effect, providing a structural basis for achieving long-acting sustained release of exenatide into the intestine and prolonging its in vivo duration of action. Fifteen db / db mice were randomly divided into three groups of five each. They underwent overnight fasting treatment, with no food but no water restriction. The experimental groups were as follows: a blank control group, a subcutaneous exenatide solution injection group, and an oral exenatide-TMMPBA-chitosan oligosaccharide@calcium carbonate / sodium alginate preparation group. The blank control group did not receive exenatide treatment but received an equal volume of normal saline orally; the subcutaneous exenatide injection group received a subcutaneous injection of 40 µg / kg; and the oral exenatide preparation group received a gavage dose of 400 µg / kg. Following administration, blood glucose levels were measured at 0, 0.5, 1, 2, 3, 4, 6, and 8 hours via tail tip sampling, and blood glucose-time curves were plotted (e.g., ...). Figure 10 (As shown in the image). Experimental results showed that the oral exenatide-TMMPBA-chitosan oligosaccharide@calcium carbonate / sodium alginate formulation exhibited a significant hypoglycemic effect, with a statistically significant difference compared to the blank control group. Furthermore, compared to the subcutaneous exenatide injection group, the oral exenatide-TMMPBA-chitosan oligosaccharide@calcium carbonate / sodium alginate formulation not only showed a significant hypoglycemic effect but also a more sustained glycemic regulation effect. The exenatide-TMMPBA-chitosan oligosaccharide@calcium carbonate / sodium alginate formulation may potentially endow the carrier with mucosal-specific anchoring and long-lasting retention capabilities, which is beneficial for improving the intestinal retention characteristics and long-acting drug delivery effect of orally delivered exenatide.

[0081] in conclusion This invention successfully constructs a cationic oral GLP-1 peptide delivery system bridged by calcium ions or borate ester bonds. This system effectively addresses the problems of peptide aggregation, poor stability, and low transmembrane absorption efficiency in existing oral delivery technologies through the synergistic effect of cationic polymers, calcium salts, and alginate polysaccharides, combined with an optional novel bifunctional bridging small molecule, 4-[(trimethylamino)methyl]phenylboronic acid. The delivery system inhibits peptide self-aggregation through electrostatic binding, enhances complex stability using calcium ions, and constructs a pH-responsive hydrogel framework, achieving gastric protection and controlled intestinal drug release. Simultaneously, the cationic polymers promote peptide absorption across the intestinal epithelium by regulating tight junctions, cell membrane interactions, and mucosal adhesion, significantly improving oral bioavailability. The preparation process of this invention is simple and mild, and the materials used have good biocompatibility, demonstrating excellent clinical translational potential and application prospects, providing a highly efficient and stable solution for oral peptide delivery.

[0082] The embodiments described above provide a detailed explanation of the technical solutions and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, and equivalent substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A cationic peptide oral delivery system, characterized in that, The raw materials include therapeutic peptides, cationic polymers, calcium salts, and alginate polysaccharides; Calcium salts bridge therapeutic peptides with calcium ions, forming peptide-cationic polymer ion-pair complexes, which serve as the core. The outer shell formed by the ionic cross-linking of alginate polysaccharides and calcium ions of calcium salts covers the core.

2. The cationic polypeptide oral delivery system according to claim 1, characterized in that, Based on raw materials, in the cationic peptide oral delivery system, the mass ratio of therapeutic peptide, cationic polymer, calcium salt, and alginate polysaccharide is 1:1~6:10~20:20~30.

3. The cationic polypeptide oral delivery system according to claim 1, characterized in that, The therapeutic polypeptide is selected from at least one of exenatide, semaglutide, and liraglutide; the cationic polymer is selected from chitin-based polysaccharides or PAMAM; the calcium salt is selected from at least one of calcium carbonate, calcium phosphate, calcium hydrogen phosphate, calcium oxalate, calcium sulfate, calcium sulfite, calcium tartrate, and calcium citrate; and the alginate polysaccharide is selected from at least one of sodium alginate, potassium alginate, ammonium alginate, and propylene glycol sodium alginate.

4. The cationic polypeptide oral delivery system according to claim 3, characterized in that, The cationic polymer material is chitosan oligosaccharide, and the molecular weight of the chitosan oligosaccharide is ≤2000 Da; the calcium salt is calcium carbonate; the alginate polysaccharide is sodium alginate, and the viscosity of the sodium alginate is 100~1000 mPa·s.

5. The cationic peptide oral delivery system according to claim 1 or 2, characterized in that, The raw materials also include 4-[(trimethylamino)methyl]phenylboronic acid; 4-[(trimethylamino)methyl]phenylboronic acid bridges therapeutic peptides and cationic polymers to form peptide-cationic polymer ion-pair complexes, serving as the core; The outer shell formed by the ionic cross-linking of alginate polysaccharides and calcium ions of calcium salts covers the core.

6. The cationic polypeptide oral delivery system according to claim 5, characterized in that, The molar ratio of 4-[(trimethylamino)methyl]phenylboronic acid to the therapeutic peptide is 5~7:

1.

7. A method for preparing a cationic polypeptide oral delivery system according to any one of claims 1 to 4, characterized in that, Includes the following steps: (1) Dissolve the therapeutic polypeptide in the first solvent and adjust the pH to 6.0-6.5 to obtain the first solution; dissolve the cationic polymer in the second solvent and adjust the pH to 6.0-6.5 to obtain the second solution; dissolve the alginate polysaccharide in the third solvent to obtain the third solution; (2) The second solution is added dropwise to the first solution, and the reaction is stirred to obtain a solution of polypeptide-cationic polymer ion-pair complex; (3) Add calcium salt to the solution of polypeptide-cationic polymer ion-pair complex, mix evenly, and vacuum dry to obtain ion-pair complex-calcium salt preparation; (4) Add the ion-pair complex-calcium salt preparation to the third solution and stir evenly to obtain the ion-pair complex-calcium salt gel preparation, which is the cationic polypeptide oral delivery system.

8. A method for preparing the cationic polypeptide oral delivery system according to claim 5 or 6, characterized in that, Includes the following steps: (1) Dissolve the therapeutic polypeptide in the first solvent and adjust the pH to 6.0-6.5 to obtain the first solution; dissolve the cationic polymer in the second solvent and adjust the pH to 6.0-6.5 to obtain the second solution; dissolve the alginate polysaccharide in the third solvent to obtain the third solution; dissolve 4-[(trimethylamino)methyl]phenylboronic acid in the fourth solvent and adjust the pH to 6.0-6.5 to obtain the fourth solution; (2) Add the fourth solution dropwise to the first solution and stir to react, to obtain the reaction solution of the therapeutic polypeptide and 4-[(trimethylamino)methyl]phenylboronic acid; (3) The second solution was added dropwise to the reaction solution of the therapeutic peptide and 4-[(trimethylamino)methyl]phenylboronic acid, and the reaction was stirred to obtain a solution of peptide-cationic polymer material ion pair complex; (4) Add calcium salt to the solution of polypeptide-cationic polymer ion-pair complex, mix well, and vacuum dry to obtain ion-pair complex-calcium salt preparation; (5) Add the ion-pair complex-calcium salt preparation to the third solution and stir evenly to obtain the ion-pair complex-calcium salt gel preparation, which is the cationic polypeptide oral delivery system.

9. The method for preparing the cationic polypeptide oral delivery system according to claim 7 or 8, characterized in that, In the third solution, the concentration of alginate polysaccharides is 1~10 mg / mL.

10. The method for preparing the cationic polypeptide oral delivery system according to claim 8, characterized in that, The preparation method of 4-[(trimethylamino)methyl]phenylboronic acid includes the following steps: (i) Dissolve 4-[(dimethylamino)-methyl]phenylboronic acid in dichloromethane, then add iodomethane, and stir the reaction at room temperature for 1-5 h; The mass ratio of iodomethane to 4-[(dimethylamino)-methyl]phenylboronic acid is 1~3:1; (ii) The product of step (i) is collected and recrystallized to obtain the 4-[(trimethylamino)methyl]phenylboronic acid.

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