A preparation process and application of sodium dextran sulfate

Abstract

The present invention provides a preparation process and application of sodium dextran sulfate, and relates to the field of catalytic synthesis technology. The preparation process provided by the present invention comprises subjecting dextran and a sulfonation reagent to a sulfonation reaction under the co-action of an alkali promoter and a cobalt-based catalyst, to obtain dextran sulfate, and then reacting with a sodium salt and refining and separating to obtain sodium dextran sulfate; the cobalt-based catalyst comprises a porous carrier and cobalt nanoparticles grown in situ on the surface of the porous carrier, and the surface of the porous carrier is also coated with a melamine protective layer. The present invention uses an alkali promoter and a cobalt-based catalyst to synergize the sulfonation reaction, which helps the sulfonation reaction to be carried out more quickly and efficiently, reduces the waste of reaction time, and can effectively improve the purity of sodium dextran sulfate through the refining and separation process, which can not only improve production efficiency, but also improve purity and molecular weight stability by inhibiting side reactions.

Description

Technical Field

[0001] The invention relates to the technical field of catalytic synthesis, and in particular to a preparation process of sodium dextran sulfate and application thereof. Background Art

[0002] Dextran Sulfate Sodium (DSS), also known as dextran sulfate sodium, is a chemically synthesized polyanion compound. Its chemical composition is the introduction of sulfate ions on the basis of the molecular structure of dextran. First of all, dextran is a polysaccharide composed of multiple glucose units connected by glycosidic bonds. When preparing dextran sulfate sodium, sulfate ions are pre-connected to the hydroxyl groups of dextran through sulfonation reaction, and then sodium ions are introduced to obtain sodium sulfate groups, thereby giving it special activity.

[0003] In the fields of medicine and biology, sodium dextran sulfate plays an important role in the study of inflammatory bowel disease (IBD). It can induce pathological features similar to human ulcerative colitis (UC). When constructing animal models, when experimental animals ingest a certain concentration of sodium dextran sulfate solution, it causes intestinal inflammation by destroying the barrier function of the intestinal mucosa. This allows researchers to use this characteristic to conduct in-depth research on the pathogenesis and pathophysiological process of inflammatory bowel disease. At the same time, because sodium dextran sulfate has good hydrophilicity and can form a moisturizing film on the skin, adding sodium dextran sulfate to skin care products can produce skin care products with the effect of removing red blood streaks, which can inhibit the skin's inflammatory response to reduce skin inflammation, thereby achieving the effect of soothing the skin and reducing the appearance of red blood streaks.

[0004] In the prior art, when synthesizing sodium dextran sulfate, chlorosulfonic acid or oleum is mainly used as a sulfonating agent, and dextran of a suitable molecular weight is dissolved in a solvent, and then reacted with a sulfonating agent to react with a hydroxyl group in the dextran to obtain dextran sulfate, and then reacted with a sodium salt to generate sodium dextran sulfate. For example, a Chinese patent with publication number CN117624404A provides a synthesis process of sodium dextran sulfate, which uses silver sulfate as a catalyst to catalyze the sulfonation reaction of low molecular weight dextran and a sulfonating agent, thereby finally obtaining sodium dextran sulfate.

[0005] However, when synthesizing sodium dextran sulfate, the above-mentioned prior art easily produces a large amount of by-products due to the high reaction activity of the sulfonation reagent, and easily causes the molecular chain of dextran to break, thereby affecting the molecular weight distribution of sodium dextran sulfate. The use of silver sulfate as a sulfonation catalyst in the above-mentioned patent does not significantly affect the rate and positive equilibrium of the sulfonation reaction, making it difficult to improve the reaction yield and reaction rate. Therefore, it is urgent to provide a solution to improve the above-mentioned problems. Summary of the invention

[0006] The purpose of the present invention is to provide a preparation process of sodium dextran sulfate and application thereof.

[0007] In a first aspect, the present invention provides a preparation process of sodium dextran sulfate, comprising: subjecting dextran with a molecular weight of 40,000 to 45,000 to a sulfonation reaction with a sulfonating agent under the co-action of an alkali promoter and a cobalt-based catalyst to obtain dextran sulfate, and then reacting the dextran sulfate with a sodium salt in an alkaline environment to obtain sodium dextran sulfate after purification and separation; the cobalt-based catalyst comprises a porous carrier and cobalt nanoparticles in situ grown on the surface of the porous carrier, and the surface of the porous carrier is also coated with a melamine protective layer.

[0008] The preparation process provided by the present invention uses an alkali promoter and a cobalt-based catalyst to synergistically enhance the sulfonation reaction, which helps the sulfonation reaction to proceed more rapidly and efficiently, reduces the waste of reaction time, and can effectively improve the purity of sodium dextran sulfate through a refining and separation process, which can not only improve production efficiency, but also improve purity and molecular weight stability by inhibiting side reactions.

[0009] Optionally, the base promoter includes one of pyridine, triethylamine and dimethylaminopyridine.

[0010] Optionally, the sulfonating agent includes one of chlorosulfonic acid, aminosulfonic acid, and fuming sulfuric acid.

[0011] Optionally, the dextran is dissolved in a solvent environment and subjected to a sulfonation reaction with a sulfonation reagent, wherein the solvent comprises one of formamide, dimethyl sulfoxide, N,N-dimethylformamide and methanol.

[0012] Optionally, when the dextran is subjected to a sulfonation reaction with a sulfonating agent, the following steps are included: stirring and dissolving the dextran and an alkali promoter in a solvent environment to obtain a reaction liquid; ultrasonically dispersing a cobalt-based catalyst in the reaction liquid to obtain a reaction suspension; adding the sulfonating agent dropwise into the reaction suspension, reacting at a constant temperature of 25-30°C for 1-2h, separating and recovering the cobalt-based catalyst, and purifying and separating to obtain dextran sulfate.

[0013] Optionally, the mass ratio of the base promoter to the cobalt-based catalyst is 1:(2-3).

[0014] Optionally, the loading amount of the cobalt nanoparticles in the cobalt-based catalyst is 5-10%.

[0015] Optionally, the molar ratio of the dextran to the sulfonation reagent is 1:(3-5).

[0016] Optionally, the concentration of the glucan in the reaction solution is 70-90% of the saturation concentration.

[0017] Optionally, the cobalt-based catalyst is placed in the reaction solution and subjected to ultrasonic treatment at a frequency of 10-30 kHz for 10-15 min.

[0018] Optionally, the total dripping time of the sulfonation reagent is 1-2h.

[0019] Optionally, after isothermal reaction at 25-30° C. for 1-2 hours, the cobalt-based catalyst is recovered by filtration under reduced pressure, and the filtrate is evaporated to dryness to collect dextran sulfate.

[0020] Optionally, when dextran sulfate is reacted with sodium salt in an alkaline environment, the steps include: stirring and dissolving dextran sulfate in deionized water in a non-oxidizing atmosphere to obtain a dextran sulfate solution; stirring and dissolving sodium salt in the dextran sulfate solution and adjusting the pH to 10-14 and stirring the reaction at 30-40°C for 1-2h, purifying and separating, and spray-drying to obtain sodium dextran sulfate.

[0021] Optionally, the non-oxidizing atmosphere includes one of a nitrogen atmosphere and an inert gas atmosphere.

[0022] Optionally, the dextran sulfate solution is 80-90% of the saturation concentration of dextran sulfate.

[0023] Alternatively, dextran sulfate is dissolved in deionized water at 30-40°C with stirring.

[0024] Optionally, the sodium salt includes one of sodium hydroxide and sodium sulfate.

[0025] Optionally, after stirring at 30-40° C. for 1-2 hours, purification and separation are performed under the action of an ultrafiltration membrane, wherein the ultrafiltration membrane has a molecular weight cutoff of 40,000-45,000.

[0026] Optionally, the preparation method of the cobalt-based catalyst includes the following steps: modifying the surface of a porous carrier with titanate to obtain a modified carrier; stirring and impregnating the modified carrier in a cobalt salt solution and separating to obtain a loaded precursor; calcining the loaded precursor at 800-1000°C in an oxygen-containing atmosphere for 1-2 hours, cooling and acid washing to obtain a loaded intermediate; reducing the loaded intermediate at 400-500°C in a hydrogen atmosphere for 2-3 hours, and cooling to obtain a catalytic intermediate; stirring and mixing the catalytic intermediate in a melamine solution, and separating and drying to obtain a cobalt-based catalyst.

[0027] Optionally, the porous carrier includes one of activated carbon, carbon nitride, zeolite, mesoporous silica, and carbon nanotubes.

[0028] Optionally, the cobalt salt in the cobalt salt solution includes one of cobalt sulfate, cobalt nitrate, cobalt chloride and cobalt acetate.

[0029] Optionally, the volume fraction of oxygen in the oxygen-containing atmosphere is 20-100%.

[0030] In a second aspect, the present invention also provides an application of sodium dextran sulfate prepared by any of the above optional preparation processes, wherein the application includes skin care products and construction of animal models.

[0031] Optionally, the animal model comprises an animal model of colitis. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. 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. Unless otherwise defined, the technical terms or scientific terms used herein should be the common meanings understood by people with general skills in the field to which the present invention belongs.

[0033] The present invention provides a preparation process of sodium dextran sulfate, comprising the following steps:

[0034] S1, subjecting dextran having a molecular weight of 40,000 to 45,000 to a sulfonation agent under the co-action of an alkali promoter and a cobalt-based catalyst to a sulfonation reaction to obtain dextran sulfate;

[0035] S2. Releasing dextran sulfate with sodium salt in an alkaline environment and then refining and separating to obtain sodium dextran sulfate.

[0036] In fact, in step S1, dextran with a molecular weight of 40,000-45,000 is selected as the starting material to produce sodium dextran sulfate with stable molecular weight. In addition, sodium dextran sulfate with a molecular weight in the range of 40,000-45,000 is a better molecular weight range for establishing a colitis animal model, which can improve the animal modeling effect.

[0037] Specifically, the use of the base promoter and the cobalt-based catalyst in step S1 can achieve a synergistic effect, thereby effectively promoting the sulfonation reaction between dextran and the sulfonation reagent. In fact, during the sulfonation reaction, the base promoter can react with the sulfonation reagent and promote the reaction between sulfate ions and hydroxyl groups. In addition, the base promoter can also increase the nucleophilicity of the hydroxyl groups in dextran, which helps the reaction between sulfate ions and hydroxyl groups and can effectively improve the sulfonation efficiency.

[0038] At the same time, the cobalt-based catalyst can form an active intermediate with dextran and the sulfonation reagent, thereby effectively reducing the activation energy required for the sulfonation reaction. Specifically, the cobalt-based catalyst can act on the electron cloud outside the hydroxyl group in dextran, and by changing the electron cloud density around the hydroxyl group, promote the reaction of the sulfonation reagent with the hydroxyl group. At the same time, the cobalt-based catalyst can also enhance the reaction activity of the sulfonation reagent, which can not only improve the reaction efficiency but also improve the reaction selectivity, reduce the occurrence of side reactions, and help improve the purity and quality of dextran sodium sulfate.

[0039] In fact, in step S2, the hydrogen ions in dextran sulfate can be replaced with sodium ions to form sodium dextran sulfate. The alkaline environment is conducive to the dissociation of the sodium salt and improves the completeness of the replacement reaction to ensure the quality and purity of the sodium dextran sulfate in the product. Therefore, after refining and separation to remove impurities, unreacted raw materials and by-products generated during the reaction, the purity and quality of sodium dextran sulfate can be further improved.

[0040] Specifically, the cobalt-based catalyst used in step S1 includes a porous carrier and cobalt nanoparticles grown in situ on the surface of the porous carrier, and the surface of the porous carrier is also coated with a melamine protective layer. In fact, since the porous carrier has a rich pore structure, it can not only provide attachment sites for cobalt nanoparticles, but also promote dextran and sulfonation reagents to diffuse into the pores of the porous carrier during the sulfonation reaction, and weakly interact with the reactant molecules, so that the reactants are enriched in the pores of the porous carrier, and then the catalytic effect of the cobalt nanoparticles is used to catalyze the sulfonation reaction, thereby increasing the reaction rate.

[0041] In addition, melamine coated on the porous carrier can form chemical bonds and coordination bonds with cobalt nanoparticles, thereby fixing the cobalt nanoparticles on the surface of the porous carrier. At the same time, the melamine protective layer also has a certain steric hindrance effect on the surface of the porous carrier, thereby preventing the mutual agglomeration of cobalt nanoparticles, thereby improving the positional stability and dispersion uniformity of cobalt nanoparticles on the surface of the porous carrier.

[0042] In addition, since melamine has a certain polarity, when the cobalt-based catalyst is dispersed in dextran, it can form hydrogen bonds with the hydroxyl groups in the dextran molecules, so that the cobalt-based catalyst can be better dispersed in the dextran, improving the compatibility of the cobalt-based catalyst in the reaction system, thereby promoting the adsorption and reaction of dextran and sulfonated reagents on the surface of the cobalt-based catalyst. At the same time, since the melamine protective layer can form a protective barrier for cobalt nanoparticles on the surface of the porous carrier, it can protect the cobalt nanoparticles, thereby improving the integrity of the cobalt-based catalyst structure and effectively improving the stability of the catalytic activity of the cobalt-based catalyst during the cyclic reaction.

[0043] In some embodiments, when executing step S1, the following sub-steps are included:

[0044] S1.1, stirring and dissolving dextran and an alkali accelerator in a solvent environment to prepare a reaction solution;

[0045] S1.2, preparing a reaction suspension by ultrasonically dispersing the cobalt-based catalyst in the reaction solution;

[0046] S1.3 Add the sulfonation reagent dropwise into the reaction suspension, and react at a constant temperature of 25-30°C for 1-2 hours, then separate and recover the cobalt-based catalyst, and purify and separate to obtain dextran sulfate.

[0047] In fact, when executing step S1.1, the dextran and the alkali promoter are stirred and dissolved to form a uniform solution system, and the dispersion and dissolution efficiency of the dextran is improved by the stirring operation, so that the dextran molecules are evenly dispersed in the reaction liquid. At the same time, the alkali promoter can adjust the acidity and alkalinity of the reaction liquid and pre-enhance the nucleophilicity of the hydroxyl group in the dextran, providing a basis for the sulfonation reaction in step S1.3. Specifically, the solvent environment used includes one of formamide, dimethyl sulfoxide, N,N-dimethylformamide, and methanol.

[0048] Specifically, when performing step S1.1, the base promoter used includes one of pyridine, triethylamine, and dimethylaminopyridine. In fact, pyridine can interact well with the sulfonating agent in the reaction system, can effectively improve the electrophilicity of the sulfonating agent, and is conducive to the sulfonation reaction. At the same time, pyridine can be used as a solvent and evenly dispersed in the reaction liquid, and triethylamine and dimethylaminopyridine can significantly enhance the reaction activity of the sulfonating agent through electronic effects, and reduce the activation energy required for the reaction, and then can achieve a good synergistic effect with the cobalt-based catalyst, thereby increasing the reaction rate.

[0049] Specifically, when executing step S1.2, the cavitation effect of ultrasonic dispersion is used to promote the rapid formation, growth and collapse of tiny bubbles in the reaction liquid, thereby promoting the uniform dispersion of the cobalt-based catalyst in the reaction liquid and avoiding the agglomeration and sedimentation of the cobalt-based catalyst. At the same time, it can promote the rupture of cavities in the pore structure of the cobalt-based catalyst, thereby exposing more active sites to improve the catalytic activity of the cobalt-based catalyst.

[0050] Specifically, when executing step S1.3, by adding the sulfonation reagent drop by drop, the concentration of the sulfonation reagent in the reaction system can be accurately controlled to avoid excessive local concentration of the sulfonation reagent causing side reactions that reduce product purity. At the same time, conducting a constant temperature reaction can avoid heat release during the reaction that causes the temperature of the reaction system to rise and cause side reactions, and avoid molecular chain breakage of dextran in a high temperature environment that causes a decrease in molecular weight.

[0051] In fact, the sulfonating agent used in the step S1.3 includes one of chlorosulfonic acid, aminosulfonic acid and fuming sulfuric acid. Specifically, the sulfonating agent can be diluted with deionized water or other solvents so that the local concentration of the sulfonating agent will not be too high after it is added to the liquid to be reacted. Specifically, when the sulfonating agent is added dropwise to the liquid to be reacted in the step S1.3, the liquid to be reacted is stirred and mixed at 200-300 rpm to promote the rapid dispersion of the sulfonating agent in the liquid to be reacted.

[0052] In fact, when chlorosulfonic acid is selected as the sulfonating agent, since the sulfur atom in the chlorosulfonic acid molecule carries a partial positive charge and has a strong electrophilicity, when chlorosulfonic acid comes into contact with dextran, the hydroxyl group in the dextran attacks the sulfur atom as a nucleophilic reagent, so that the sulfonic acid group in the chlorosulfonic acid replaces the hydrogen atom on the hydroxyl group, and then the sulfate group is introduced into the dextran to form dextran sulfate.

[0053] In some embodiments, when executing step S1, the mass ratio of the base promoter to the cobalt-based catalyst is 1:(2-3). In fact, the use of base promoters and cobalt-based catalysts in this range helps to synergistically improve the reaction rate, wherein the base promoter can adjust the nucleophilicity of the hydroxyl group in the glucan in the reaction system, and the cobalt-based catalyst can reduce the reaction activation energy, thereby promoting the reaction to proceed in the forward direction.

[0054] In some embodiments, when performing step S1, the loading amount of the cobalt nanoparticles in the cobalt-based catalyst is 5-10%. This can provide sufficient reaction sites to promote the sulfonation reaction, and can ensure that the cobalt-based nanoparticles are uniformly loaded on the surface of the porous carrier, and there will be no agglomeration of the cobalt-based nanoparticles, which will reduce the utilization rate of the active sites. In addition, by selecting a suitable loading amount of cobalt nanoparticles and then coating and protecting them with a melamine protective layer, the cobalt nanoparticles can be prevented from falling off.

[0055] In some embodiments, when performing step S1, the molar ratio of dextran to sulfonation reagent is 1:(3-5). In fact, selecting a relatively excessive amount of sulfonation reagent can make the sulfonation molecules fully contact with the hydroxyl groups in dextran, which helps to improve the conversion rate of dextran and thus improve the degree of sulfonation reaction. At the same time, this molar ratio of dextran to sulfonation reagent can control the molecular weight distribution of the product, avoid the molecular weight difference of the product caused by incomplete reaction through sufficient sulfonation reaction, make the molecular weight distribution of the product more concentrated, and help to improve the quality of dextran sulfate sodium.

[0056] In some embodiments, when performing step S1.1, the concentration of dextran in the reaction solution is 70-90% of the saturation concentration. In fact, a higher concentration of dextran helps to increase the collision frequency between dextran and the sulfonated reagent, thereby increasing the reaction rate. At the same time, since the saturation concentration is not reached, the dextran still has a high fluidity and activity in the reaction solution, avoiding crystallization during the reaction process and causing the reaction to stagnate.

[0057] In some embodiments, when performing step S1.2, the cobalt-based catalyst is subjected to ultrasonic treatment at a frequency of 10-30 kHz for 10-15 minutes in the reaction solution. In fact, when ultrasonic treatment is performed at a frequency of 10-30 kHz, the ultrasonic cavitation effect can be effectively utilized to promote the uniform dispersion of the cobalt-based catalyst, while avoiding the influence of ultrasonic waves on the structural stability of the estimated catalyst itself.

[0058] In some embodiments, when executing step S1.3, the total dripping time of the sulfonation reagent is 1-2h. In fact, by slowly dripping the sulfonation reagent, it is possible to effectively avoid the side reactions caused by the local excessive concentration of the sulfonation reagent. At the same time, it is helpful to control the reaction temperature of the reaction system and avoid the temperature of the reaction system from rising sharply and being difficult to control after a large amount of sulfonation reagent is added.

[0059] In some embodiments, when performing step S1.3, after isothermal reaction at 25-30°C for 1-2h, the cobalt-based catalyst is recovered by filtration under reduced pressure, and the filtrate is evaporated to dryness to collect dextran sulfate. In fact, reacting at 25-30°C is conducive to inhibiting the side reaction, and the dropwise addition of the sulfonation reagent is helpful to control the temperature. Secondly, after the cobalt-based catalyst is recovered, it is conducive to the reuse of the cobalt-based catalyst to avoid waste and environmental pollution. After the filtrate is evaporated to dryness, purified dextran sulfate can be obtained.

[0060] In some embodiments, when executing step S2, the following sub-steps are included:

[0061] S2.1, dissolving dextran sulfate in deionized water under stirring in a non-oxidizing atmosphere to prepare a dextran sulfate solution;

[0062] S2.2, dissolving the sodium salt in the dextran sulfate solution with stirring, adjusting the pH to 10-14, and reacting with stirring at 30-40°C for 1-2h, purifying and separating, and spray-drying to obtain sodium dextran sulfate.

[0063] Specifically, when performing step S2.1, the dextran sulfate is stirred and dissolved in a non-oxidizing atmosphere, which can prevent the sulfate in the dextran sulfate from being oxidized and causing the purity of the product to decrease. In fact, the non-oxidizing atmosphere used can be one of a nitrogen atmosphere, a nitrogen atmosphere and an inert atmosphere, and the dextran sulfate solution is 80-90% of the saturated concentration of the dextran sulfate.

[0064] Specifically, when executing step S2.2, the dissociation of sodium salt is facilitated in an alkaline environment and sufficient sodium ions are provided to replace the hydrogen atoms in dextran sulfate, thereby generating sodium dextran sulfate. In addition, in an alkaline environment, it is beneficial to improve the activity and efficiency of the replacement reaction and avoid the hydrolysis of dextran sulfate. At the same time, by controlling the reaction temperature, it is beneficial to improve the reaction activity and avoid the occurrence of side reactions. In addition, when executing step S2.1, dextran sulfate is stirred and dissolved in deionized water at 30-40°C. Specifically, the sodium salt includes one of sodium hydroxide and sodium sulfate.

[0065] Specifically, when performing step S2.2, purification and separation can remove impurities and by-products generated during the reaction, which helps to improve the purity and molecular weight concentration of the generated sodium dextran sulfate. Specifically, purification and separation can be performed under the action of an ultrafiltration membrane, wherein the molecular weight cutoff of the ultrafiltration membrane is 40,000-45,000.

[0066] In some embodiments, the method for preparing a cobalt-based catalyst comprises the following steps:

[0067] G1. Modifying the porous carrier surface with titanate to obtain a modified carrier;

[0068] G2, stirring and impregnating the modified support in a cobalt salt solution and separating the supported precursor;

[0069] G3, calcining the loaded precursor at 800-1000°C in an oxygen-containing atmosphere for 1-2 hours, cooling and acid washing to obtain a loaded intermediate;

[0070] G4, reducing the loaded intermediate in a hydrogen atmosphere at 400-500° C. for 2-3 hours and then cooling to obtain a catalytic intermediate;

[0071] G5. Stir and mix the catalytic intermediate in the melamine solution, and then separate and dry to obtain a cobalt-based catalyst.

[0072] In fact, after the porous carrier surface is modified with titanate in advance, the titanate can react chemically with the active groups on the porous carrier surface, thereby increasing the richness of the functional groups on the porous carrier surface, and at the same time facilitating the adsorption of cobalt ions, which can effectively increase the loading amount and loading uniformity of cobalt ions on the porous carrier surface. In addition, after the porous carrier is modified with titanate, the dispersibility of the modified carrier can be improved, thereby avoiding the agglomeration and sedimentation of the porous carrier when the cobalt ion is loaded.

[0073] In fact, by stirring and immersing the modified support in the cobalt salt solution, it is helpful for the modified support to fully contact with the cobalt salt solution, thereby enabling the cobalt ions to be more evenly adsorbed onto the surface and pores of the modified support, which can effectively increase the loading amount and loading uniformity of the cobalt ions and provide a good foundation for the subsequent calcination oxidation and reduction processes.

[0074] In fact, calcining the loaded precursor in a high-temperature oxygen-containing atmosphere can promote the decomposition and oxidation reaction of the cobalt salt loaded on the surface of the modified carrier, so that the cobalt salt decomposes into cobalt oxide and sintered with the surface of the porous carrier, thereby improving the positional stability of the cobalt oxide on the surface of the porous carrier. At the same time, in a high-temperature environment, the titanate groups on the surface of the porous carrier can be converted into inorganic carbon chains, thereby further improving the surface stability of the cobalt oxide.

[0075] In fact, after the loaded intermediate is treated in a high-temperature hydrogen atmosphere, the cobalt oxide loaded on the surface of the porous carrier can be reduced to generate cobalt nanoparticles and attached to the surface of the porous carrier. At the same time, the reduction reaction is carried out at 400-500°C, which helps to ensure that the cobalt oxide is completely reduced while avoiding the mutual adsorption of the cobalt nanoparticles, thereby causing the particles to agglomerate and expand.

[0076] In fact, stirring and mixing the catalytic intermediate in the melamine solution is conducive to sufficient contact between melamine and the surface of the catalytic intermediate, and is conducive to forming a uniform and stable protective layer on the surface of the catalytic intermediate, thereby improving the position stability and dispersion performance of the cobalt nanoparticles. Specifically, after the catalytic intermediate is mixed with the melamine solution, ultrasonic mixing is used to promote uniform dispersion of the catalytic intermediate in the melamine solution.

[0077] In some embodiments, the porous carrier used in the execution of step G1 includes one of activated carbon, carbon nitride, zeolite, mesoporous silica, and carbon nanotubes; the cobalt salt in the cobalt salt solution used in the execution of step G2 includes one of cobalt sulfate, cobalt nitrate, cobalt chloride, and cobalt acetate; and the oxygen volume fraction in the oxygen-containing atmosphere in the execution of step G3 is 20-100%.

[0078] The present invention also provides an application of sodium dextran sulfate prepared by the preparation process in any of the above embodiments in constructing an animal model. Specifically, the animal model includes a colitis animal model. In fact, when constructing a colitis animal model, it includes inducing the construction of an acute colitis animal model and inducing the construction of a chronic colitis animal model.

[0079] In some embodiments, when constructing an acute colitis animal model, the method includes: selecting adult mice in advance to continuously drink a 3-5% sodium dextran sulfate solution for 5-6 days until symptoms of acute colitis appear.

[0080] In some embodiments, when constructing an animal model of chronic colitis, the method includes: selecting adult animals to drink a 2-3% sodium dextran sulfate solution for 3-5 days, and then drinking purified water for 2-3 days, and then repeating the cycle until symptoms of chronic colitis appear.

[0081] Preparation Example 1

[0082] This preparation example 1 provides a method for preparing a cobalt-based catalyst, comprising the following steps:

[0083] G1. Preheat the carbon nitride in a 50°C incubator for 1 hour, add the preheated carbon nitride into a 3% PN-130 titanate coupling agent (the mass ratio of carbon nitride to PN-130 is 1:0.02) methanol solution, ultrasonically treat at a frequency of 10 kHz for 10 minutes, filter under reduced pressure, rinse the solid with anhydrous ethanol and deionized water, and dry in a 40°C vacuum drying oven to constant weight to obtain a modified carrier;

[0084] G2, the modified carrier was stirred and mixed in a cobalt chloride solution with a concentration of 25 g / mL (the mass ratio of the modified carrier to cobalt chloride was 1:0.6), and then kept warm at 40°C and mechanically stirred at 200 rpm. After being kept warm and stirred for 5 hours, the carrier was filtered under reduced pressure and rinsed with deionized water, and then dried in a vacuum drying oven at 40°C to constant weight to obtain a loaded precursor;

[0085] G3, placing the loaded precursor in a tube furnace, heating the tube furnace from room temperature to 900°C at a rate of 5°C / min in an air atmosphere, and then keeping the temperature for 1.5 hours, cooling it to room temperature with the furnace, pickling it with a 20% hydrochloric acid solution, and drying it in a vacuum drying oven at 40°C to constant weight to obtain a loaded intermediate;

[0086] G4, placing the loaded intermediate in a tubular furnace, replacing the atmosphere in the tubular furnace with hydrogen three times, heating the tubular furnace from room temperature to 450°C at a rate of 5°C / min under an argon atmosphere and keeping the temperature for 2.5 hours, and then cooling the furnace to room temperature to obtain a catalytic intermediate;

[0087] G5. The catalytic intermediate is placed in a formic acid solution with a concentration of 5 g / L melamine (the mass ratio of the catalytic intermediate to melamine is 1:0.2) and stirred in a 40°C water bath for 2 hours. The mixture is then filtered under reduced pressure and rinsed with formic acid. The mixture is then dried in a vacuum environment to a constant weight to obtain a cobalt-based catalyst.

[0088] Preparation Example 2

[0089] This preparation example 2 provides a method for preparing a cobalt-based catalyst, comprising the following steps:

[0090] G1. Preheat the carbon nitride in a 50°C incubator for 1 hour, add the preheated carbon nitride into a 3% PN-130 titanate coupling agent (the mass ratio of carbon nitride to PN-130 is 1:0.02) methanol solution, ultrasonically treat at a frequency of 10 kHz for 10 minutes, filter under reduced pressure, rinse the solid with anhydrous ethanol and deionized water, and dry in a 40°C vacuum drying oven to constant weight to obtain a modified carrier;

[0091] G2, the modified carrier was stirred and mixed in a cobalt chloride solution with a concentration of 25 g / mL (the mass ratio of the modified carrier to cobalt chloride was 1:0.6), and then kept warm at 40°C and mechanically stirred at 200 rpm. After being kept warm and stirred for 5 hours, the carrier was filtered under reduced pressure and rinsed with deionized water, and then dried in a vacuum drying oven at 40°C to constant weight to obtain a loaded precursor;

[0092] G3, placing the loaded precursor in a tube furnace, heating the tube furnace from room temperature to 900°C at a rate of 5°C / min in an air atmosphere, and then keeping the temperature for 1.5 hours, cooling it to room temperature with the furnace, pickling it with a 20% hydrochloric acid solution, and drying it in a vacuum drying oven at 40°C to constant weight to obtain a loaded intermediate;

[0093] G4. The loaded intermediate was placed in a tubular furnace. The atmosphere in the tubular furnace was replaced three times with hydrogen. The temperature of the tubular furnace was raised from room temperature to 450°C at a rate of 5°C / min under an argon atmosphere and kept at that temperature for 2.5 hours. The cobalt-based catalyst was then obtained after the furnace was cooled to room temperature.

[0094] Example 1

[0095] This embodiment 1 provides a method for preparing sodium dextran sulfate, comprising the following steps:

[0096] S1. Dissolve dextran with an average molecular weight of 43,000 and pyridine in a mass ratio of 1:0.1 in 500 mL of dimethyl sulfoxide, and treat with ultrasound at a frequency of 10 kHz for 10 minutes to obtain a reaction solution, wherein the concentration of dextran in the reaction solution is 80% of its saturation concentration; add the cobalt-based catalyst prepared in Preparation Example 1 to the reaction solution, and treat with ultrasound at a frequency of 20 kHz for 15 minutes to obtain a reaction suspension; wherein the mass ratio of the cobalt-based catalyst to pyridine is 2.5:1; and keep the reaction suspension at 30°C. After keeping the temperature in the heating equipment for 10 minutes, chlorosulfonic acid (the molar ratio of dextran to chlorosulfonic acid is 1:3) and dimethyl sulfoxide are mixed at a volume ratio of 1:2 to prepare a chlorosulfonic acid dimethyl sulfoxide mixed solution, and then the chlorosulfonic acid dimethyl sulfoxide mixed solution is added dropwise into the reaction suspension, and the reaction suspension is mechanically stirred at 100 rpm, and the total dripping time of the chlorosulfonic acid dimethyl sulfoxide mixed solution is controlled to be 2 hours. After the dripping is completed, the reaction is carried out at a constant temperature for 0.5 hours, and the cobalt-based catalyst is recovered after filtration under reduced pressure, and the filtrate is evaporated to dryness and collected to obtain dextran sulfate;

[0097] S2. Stir and dissolve dextran sulfate in deionized water in a nitrogen atmosphere to obtain a dextran sulfate solution, wherein the concentration of dextran sulfate in the dextran sulfate solution is 85% of its saturated concentration; add a saturated aqueous solution of sodium hydroxide (the molar ratio of dextran sulfate to sodium hydroxide is 1:2) to the dextran sulfate solution, and adjust the pH to 12, and stir the reaction in a 35°C water bath environment for 2 hours, separate using an ultrafiltration membrane with a molecular weight cutoff of 45,000, and spray dry using a spray dryer at an inlet air temperature of 160°C to obtain dextran sulfate sodium.

[0098] Example 2

[0099] This embodiment 2 provides a preparation process of sodium dextran sulfate, comprising the following steps:

[0100] S1. Dissolve dextran with an average molecular weight of 43,000 and pyridine in a mass ratio of 1:0.1 in 500 mL of dimethyl sulfoxide, and treat with ultrasound at a frequency of 10 kHz for 10 min to obtain a reaction solution, wherein the concentration of dextran in the reaction solution is 80% of the saturated concentration; add the cobalt-based catalyst prepared in Preparation Example 2 to the reaction solution, and treat with ultrasound at a frequency of 20 kHz for 15 min to obtain a reaction suspension; wherein the mass ratio of the cobalt-based catalyst to pyridine is 2.5:1; and keep the reaction suspension at 30°C. After keeping the temperature in the heating equipment for 10 minutes, chlorosulfonic acid (the molar ratio of dextran to chlorosulfonic acid is 1:3) and dimethyl sulfoxide are mixed at a volume ratio of 1:2 to prepare a chlorosulfonic acid dimethyl sulfoxide mixed solution, and then the chlorosulfonic acid dimethyl sulfoxide mixed solution is added dropwise into the reaction suspension, and the reaction suspension is mechanically stirred at 100 rpm, and the total dripping time of the chlorosulfonic acid dimethyl sulfoxide mixed solution is controlled to be 2 hours. After the dripping is completed, the reaction is carried out at a constant temperature for 0.5 hours, and the cobalt-based catalyst is recovered after filtration under reduced pressure, and the filtrate is evaporated to dryness and collected to obtain dextran sulfate;

[0101] S2. Stir and dissolve dextran sulfate in deionized water in a nitrogen atmosphere to obtain a dextran sulfate solution, wherein the concentration of dextran sulfate in the dextran sulfate solution is 85% of the saturated concentration; add a saturated aqueous solution of sodium hydroxide (the molar ratio of dextran sulfate to sodium hydroxide is 1:2) to the dextran sulfate solution, and adjust the pH to 12, and stir the reaction in a 35°C water bath environment for 2 hours, separate using an ultrafiltration membrane with a molecular weight cutoff of 45,000, and spray dry using a spray dryer at an air inlet temperature of 160°C to obtain dextran sulfate sodium.

[0102] Comparative Example 1

[0103] This comparative example 1 provides a preparation process of sodium dextran sulfate, comprising the following steps:

[0104] S1. Mix dextran with an average molecular weight of 43,000 and pyridine in a mass ratio of 1:0.1 and dissolve them in 500 mL of dimethyl sulfoxide, and then treat them with ultrasound at a frequency of 10 kHz for 10 minutes to obtain a reaction solution, and the concentration of dextran in the reaction solution is 80% of the saturated concentration; add silver sulfate to the reaction solution, and treat it with ultrasound at a frequency of 20 kHz for 15 minutes to obtain a reaction suspension; wherein the mass ratio of silver sulfate to pyridine is 2.5:1; and heat the reaction suspension at a constant temperature of 30°C. After keeping warm for 10 minutes, chlorosulfonic acid (the molar ratio of dextran to chlorosulfonic acid is 1:3) and dimethyl sulfoxide are mixed at a volume ratio of 1:2 to prepare a chlorosulfonic acid dimethyl sulfoxide mixed solution, and then the chlorosulfonic acid dimethyl sulfoxide mixed solution is added dropwise into the reaction suspension, and the reaction suspension is mechanically stirred at 100 rpm, and the total dripping time of the chlorosulfonic acid dimethyl sulfoxide mixed solution is controlled to be 2 hours. After the dripping is completed, the reaction is carried out at a constant temperature for 0.5 hours, and then 2 volumes of isopropanol are added to the reaction suspension to precipitate dextran sulfate;

[0105] S2. Stir and dissolve dextran sulfate in deionized water in a nitrogen atmosphere to obtain a dextran sulfate solution, wherein the concentration of dextran sulfate in the dextran sulfate solution is 85% of the saturated concentration; add a saturated aqueous solution of sodium hydroxide (the molar ratio of dextran sulfate to sodium hydroxide is 1:2) to the dextran sulfate solution, and adjust the pH to 12, and stir the reaction in a 35°C water bath environment for 2 hours, separate using an ultrafiltration membrane with a molecular weight cutoff of 45,000, and spray dry using a spray dryer at an air inlet temperature of 160°C to obtain dextran sulfate sodium.

[0106] Comparative Example 2

[0107] This comparative example 2 provides a method for preparing sodium dextran sulfate, comprising the following steps:

[0108] S1. Dissolve dextran with an average molecular weight of 43,000 in 500 mL of dimethyl sulfoxide, and treat it with ultrasound at a frequency of 10 kHz for 10 minutes to obtain a reaction solution, wherein the concentration of dextran in the reaction solution is 80% of the saturated concentration; add the cobalt-based catalyst prepared in Preparation Example 1 to the reaction solution, and treat it with ultrasound at a frequency of 20 kHz for 15 minutes to obtain a reaction suspension; wherein the mass ratio of the cobalt-based catalyst to pyridine is 2.5:1; place the reaction suspension in a constant temperature device at 30°C After keeping the temperature for 10 minutes, chlorosulfonic acid (the molar ratio of dextran to chlorosulfonic acid is 1:3) and dimethyl sulfoxide are mixed at a volume ratio of 1:2 to prepare a chlorosulfonic acid dimethyl sulfoxide mixed solution, and then the chlorosulfonic acid dimethyl sulfoxide mixed solution is added dropwise into the reaction suspension, and the reaction suspension is mechanically stirred at 100 rpm, and the total dripping time of the chlorosulfonic acid dimethyl sulfoxide mixed solution is controlled to be 2 hours. After the dripping is completed, the reaction is carried out at a constant temperature for 0.5 hours, and then the filtrate is filtered under reduced pressure, and then the filtrate is evaporated to dryness and collected to obtain dextran sulfate;

[0109] S2. Stir and dissolve dextran sulfate in deionized water in a nitrogen atmosphere to obtain a dextran sulfate solution, wherein the concentration of dextran sulfate in the dextran sulfate solution is 85% of its saturated concentration; add a saturated aqueous solution of sodium hydroxide (the molar ratio of dextran sulfate to sodium hydroxide is 1:2) to the dextran sulfate solution, and adjust the pH to 12, and stir the reaction in a 35°C water bath environment for 2 hours, separate using an ultrafiltration membrane with a molecular weight cutoff of 45,000, and spray dry using a spray dryer at an inlet air temperature of 160°C to obtain dextran sulfate sodium.

[0110] Comparative Example 3

[0111] This comparative example 3 provides a method for preparing sodium dextran sulfate, comprising the following steps:

[0112] S1. Dissolve dextran with an average molecular weight of 43,000 and pyridine in a mass ratio of 1:0.1 in 500 mL of dimethyl sulfoxide, and treat with ultrasound at a frequency of 10 kHz for 10 minutes to obtain a reaction solution, in which the concentration of dextran in the reaction solution is 80% of its saturation concentration; add cobalt oxide to the reaction solution, treat with ultrasound at a frequency of 20 kHz for 15 minutes to obtain a reaction suspension; wherein the mass ratio of cobalt oxide to pyridine is 2.5:1; keep the reaction suspension in a constant temperature device at 30°C After warming for 10 minutes, chlorosulfonic acid (the molar ratio of dextran to chlorosulfonic acid is 1:3) and dimethyl sulfoxide are mixed at a volume ratio of 1:2 to prepare a chlorosulfonic acid dimethyl sulfoxide mixed solution, and then the chlorosulfonic acid dimethyl sulfoxide mixed solution is added dropwise into the reaction suspension, and the reaction suspension is mechanically stirred at 100 rpm, and the total dripping time of the chlorosulfonic acid dimethyl sulfoxide mixed solution is controlled to be 2 hours. After the dripping is completed, the reaction is carried out at a constant temperature for 0.5 hours, and then the dextran sulfate is collected after the filtration is reduced pressure and the cobalt oxide is recovered, and the filtrate is evaporated to dryness to collect the dextran sulfate;

[0113] S2. Stir and dissolve dextran sulfate in deionized water in a nitrogen atmosphere to obtain a dextran sulfate solution, wherein the concentration of dextran sulfate in the dextran sulfate solution is 85% of its saturated concentration; add a saturated aqueous solution of sodium hydroxide (the molar ratio of dextran sulfate to sodium hydroxide is 1:2) to the dextran sulfate solution, and adjust the pH to 12, and stir the reaction in a 35°C water bath environment for 2 hours, separate using an ultrafiltration membrane with a molecular weight cutoff of 45,000, and spray dry using a spray dryer at an inlet air temperature of 160°C to obtain dextran sulfate sodium.

[0114] Performance Testing

[0115] The sodium dextran sulfate prepared in Example 1, Example 2, Comparative Examples 1 to 3 and the blank example (DSS of Yishen Bio 60316ES) were used to model acute colitis in adult mice, including the following steps: 5% sodium dextran sulfate aqueous solutions were prepared respectively, and adult mice were selected and cultured normally for 7 days, and then randomly divided into groups and continuously fed with 5% sodium dextran sulfate aqueous solution for 5 days to observe whether acute colitis symptoms appeared as shown in Table 1 below.

[0116] After placing the sodium dextran sulfate prepared in Example 1, Example 2, and Comparative Examples 1 to 3 in an incubator at 25° C. and 40% humidity for 6 months, observe whether the surface changes in color, and model acute colitis in adult mice to observe whether symptoms of acute colitis appear within 5 days as shown in Table 1 below.

[0117] Table 1 Results of acute colitis modeling experiment

[0118] Is modeling successful? Is modeling successful after placement? Does the color change? Example 1 yes yes none Example 2 yes yes none Comparative Example 1 yes yes none Comparative Example 2 no no none Comparative Example 3 no no yes Blank example 1 yes yes none

[0119] The cobalt-based catalyst recovered in Example 1 and Example 2 was used to prepare sodium dextran sulfate for four cycles according to the processes in Example 1 and Example 2, respectively. After each recovery, the catalyst was rinsed with deionized water and dried. The yield change of dextran sulfate during each cycle test was recorded, and the yield attenuation rate compared with the first test was calculated, as shown in Table 2 below.

[0120] Table 2 Decrease rate of dextran sulfate yield during the cycle test

[0121] 1 2 3 4 5 Example 1 0 0.19 0.32 0.46 0.57 Example 2 0 1.16 1.67 3.25 4.52

[0122] Although the embodiments of the present invention are described in detail above, it is obvious to those skilled in the art that various modifications and variations can be made to these embodiments. However, it should be understood that such modifications and variations are within the scope and spirit of the present invention as described in the claims. Moreover, the present invention described herein may have other embodiments and may be implemented or realized in a variety of ways.

Claims

1. A process for preparing sodium dextran sulfate, characterized in that: include: Dextran with a molecular weight of 40,000 to 45,000 is subjected to a sulfonation reaction with a sulfonation agent under the co-action of an alkali promoter and a cobalt-based catalyst to obtain dextran sulfate, and then the dextran sulfate is reacted with a sodium salt in an alkaline environment and then purified and separated to obtain sodium dextran sulfate; The cobalt-based catalyst comprises a porous carrier and cobalt nanoparticles in situ grown on the surface of the porous carrier, and the surface of the porous carrier is also coated with a melamine protective layer; The preparation method of the cobalt-based catalyst comprises the following steps: modifying the surface of a porous carrier with titanate to obtain a modified carrier; stirring and impregnating the modified carrier in a cobalt salt solution and separating to obtain a loaded precursor; calcining the loaded precursor at 800-1000° C. in an oxygen-containing atmosphere for 1-2 hours, cooling and acid washing to obtain a loaded intermediate; reducing the loaded intermediate at 400-500° C. in a hydrogen atmosphere for 2-3 hours, and cooling to obtain a catalytic intermediate; stirring and mixing the catalytic intermediate in a melamine solution, and separating and drying to obtain a cobalt-based catalyst.

2. The preparation process according to claim 1, characterized in that: The base promoter includes one of pyridine, triethylamine, and dimethylaminopyridine; and / or, the sulfonation reagent includes one of chlorosulfonic acid, aminosulfonic acid, and fuming sulfuric acid; and / or, dextran is dissolved in a solvent environment to carry out a sulfonation reaction with the sulfonation reagent, and the solvent includes one of formamide, dimethyl sulfoxide, N,N-dimethylformamide, and methanol.

3. The preparation process according to claim 1, characterized in that: When dextran is subjected to sulfonation reaction with a sulfonation reagent, the method comprises the following steps: stirring and dissolving dextran and an alkali promoter in a solvent environment to obtain a reaction liquid; ultrasonically dispersing a cobalt-based catalyst in the reaction liquid to obtain a reaction suspension; dropwise adding the sulfonation reagent into the reaction suspension, reacting at a constant temperature of 25-30°C for 1-2h, separating and recovering the cobalt-based catalyst, and purifying and separating to obtain dextran sulfate.

4. The preparation process according to claim 3, characterized in that: The mass ratio of the base promoter to the cobalt-based catalyst is 1:(2-3); and / or the loading amount of the cobalt nanoparticles in the cobalt-based catalyst is 5-10%; and / or the molar ratio of the dextran to the sulfonation reagent is 1:(3-5); and / or the concentration of the dextran in the reaction liquid is 70-90% of the saturated concentration; and / or the cobalt-based catalyst is subjected to ultrasonic treatment at a frequency of 10-30 kHz for 10-15 min in the reaction liquid; and / or the total dripping time of the sulfonation reagent is 1-2 h; and / or, after isothermal reaction at 25-30° C. for 1-2 h, the cobalt-based catalyst is filtered under reduced pressure and the cobalt-based catalyst is recovered, and the filtrate is evaporated to dryness and the dextran sulfate is collected.

5. The preparation process according to claim 1, characterized in that: When dextran sulfate is reacted with sodium salt in an alkaline environment, the method comprises the following steps: stirring and dissolving dextran sulfate in deionized water in a non-oxidizing atmosphere to obtain a dextran sulfate solution; stirring and dissolving the sodium salt in the dextran sulfate solution, adjusting the pH to 10-14, stirring and reacting at 30-40° C. for 1-2 hours, purifying and separating, and spray-drying to obtain sodium dextran sulfate.

6. The preparation process according to claim 5, characterized in that: The non-oxidizing atmosphere is an inert gas atmosphere; and / or, the dextran sulfate solution is 80-90% of the saturated concentration of dextran sulfate; and / or, the dextran sulfate is stirred and dissolved in deionized water at 30-40°C; and / or, the sodium salt includes one of sodium hydroxide and sodium sulfate; and / or, after stirring at 30-40°C for 1-2h, purification and separation are carried out under the action of an ultrafiltration membrane, and the retention molecular weight of the ultrafiltration membrane is 40,000-45,000.

7. The preparation process according to claim 1, characterized in that: The porous carrier includes one of activated carbon, carbon nitride, zeolite, mesoporous silica, and carbon nanotubes; and / or the cobalt salt in the cobalt salt solution includes one of cobalt sulfate, cobalt nitrate, cobalt chloride, and cobalt acetate; and / or the volume fraction of oxygen in the oxygen-containing atmosphere is 20-100%.