An oxidized sodium alginate and its preparation, extraction and application

Abstract

The present invention discloses an oxidized sodium alginate and its preparation, extraction and application. The extraction method of oxidized sodium alginate includes: impregnating and washing the oxidized sodium alginate raw material in a heterogeneous state in a first solution to obtain an acidified oxidized sodium alginate precipitate, the first solution comprising water, an acid and a first organic solvent; dispersing the precipitate in a second solution for neutralization, the second solution comprising water and a second organic solvent; impregnating and dehydrating in a heterogeneous state using a third organic solvent, and drying to obtain oxidized sodium alginate. The method of the present invention is carried out in a heterogeneous system, and the first solution containing a low concentration of acid and an organic solvent is used for impregnating and washing, which can effectively remove impurities in the oxidized sodium alginate, significantly shorten the extraction time to about 1 day, greatly improve the preparation efficiency, and can obtain high-quality oxidized sodium alginate with sterile and low endotoxin content, and can be mass-produced rapidly, having a wide application prospect.

Description

Technical Field

[0001] The present invention relates to the field of organic polymer materials. Specifically, the present invention relates to an oxidized sodium alginate and its preparation, extraction and application. Background Art

[0002] Sodium Alginate (SA) is a natural polysaccharide extracted from brown algae, mainly composed of β-D-mannuronic acid (M unit) and α-L-guluronic acid (G unit) connected by 1→4 glycosidic bonds. The aqueous solution of sodium alginate has a stable viscosity at pH 6-9, has pH sensitivity, and can form hydrogels in the presence of cations such as Ca 2+ etc., and is used as a thickener, stabilizer, emulsifier, etc. in the food industry, and as a drug carrier, cell carrier, etc. in the biomedical field.

[0003] Oxidized Sodium Alginate (OSA) is a product obtained by oxidizing sodium alginate, and its characteristic is that some hydroxyl groups are oxidized into active aldehyde groups. Due to its dialdehyde structure, oxidized sodium alginate has a strong covalent cross-linking effect on proteins, so it has a wide range of applications in the fields of drug release and tissue engineering. At present, there are very few oxidized sodium alginate products sold on the domestic and foreign markets, and the specifications are small (100mg-1g level packaging), and the price is expensive, with a rough market price between 500 yuan per gram and 20,000 yuan per gram. There has not yet been an oxidized sodium alginate product that can be prepared and sold on a large scale. As a new type of green natural polymer material derivative, oxidized sodium alginate has been widely studied and recognized in the field of biomedical related materials, and has extremely broad application prospects in the fields of medicine, food, environmental protection, etc. At present, there are few biomedical products based on oxidized sodium alginate on the market. The main reason is still that the preparation of oxidized sodium alginate raw materials is difficult, the yield is low, and the cost is high, which is not conducive to large-scale commercial promotion. A method for preparing oxidized sodium alginate quickly at low cost on a large scale and preparing high-quality oxidized sodium alginate products with high cleanliness and low endotoxin content is very important for its application in the biomedical field, and a feasible solution is urgently needed. Summary of the Invention

[0004] The present invention is made based on the inventor's discovery and recognition of the following facts and problems: At present, there are mainly the following two methods for precipitation extraction after the oxidation reaction of sodium alginate to generate oxidized sodium alginate:

[0005] (1) Dissolve the oxidized sodium alginate product in water, perform dialysis using a dialysis bag to remove small molecule inorganic salt impurities. After no iodate impurities can be detected anymore, dry it using a vacuum freeze dryer to obtain a dried oxidized sodium alginate precipitate, and then perform operations such as grinding and pulverizing to prepare oxidized sodium alginate powder. The disadvantage of this method is that the operations of dialysis and freeze-drying are cumbersome and extremely time-consuming. Single production requires at least 7 - 10 days. Moreover, when oxidized sodium alginate is in an aqueous solution environment for a long time, its molecular chain and active aldehyde groups are both in an unstable state and are easily damaged, resulting in unstable product quality. It cannot be produced on a large scale and in large quantities, nor can it produce high-quality oxidized sodium alginate products in multiple batches.

[0006] (2) Completely dissolve the oxidized sodium alginate product in water, use ethanol in a certain proportion to precipitate sodium alginate (usually the ethanol concentration is above 50%), then separate the precipitate, and repeatedly dissolve and precipitate according to the same operation until no iodate impurities can be detected in the oxidized sodium alginate solution. Then perform operations such as grinding and pulverizing on the precipitate to prepare oxidized sodium alginate powder. The disadvantage of this method is that repeatedly dissolving and precipitating oxidized sodium alginate will cause serious damage to the molecular chain and its active aldehyde groups of oxidized sodium alginate, reducing the product quality. At the same time, a certain amount of the product will also be lost and cannot precipitate smoothly; the dissolution process of oxidized sodium alginate is relatively difficult and time-consuming; at the same time, iodate impurities are also insoluble in organic solvents and have a low solubility in ethanol above 50%. This method consumes a large amount of absolute ethanol or other similar organic solvents, with cumbersome operations and high costs, and is also not suitable for large-scale industrial production.

[0007] Therefore, there is an urgent need to propose an industrialized large-scale production method for oxidized sodium alginate that is low-cost, simple to operate, time-consuming, and has a low threshold. And it is committed to improving the quality of the product oxidized sodium alginate, protecting the molecular chain length and the number of active aldehyde groups of oxidized sodium alginate, and ensuring sterility and cleanliness, making it conducive to applications in the biomedical field.

[0008] The present invention aims to solve at least one of the technical problems in the related art to some extent. For this reason, an embodiment of the present invention proposes an oxidized sodium alginate and its preparation, extraction, and application. The method of the present invention is carried out in a heterogeneous system, and a first solution containing a low concentration of acid and an organic solvent is used for impregnation and washing, which can effectively remove impurities in oxidized sodium alginate, significantly shorten the extraction time to about 1 day, greatly improve the preparation efficiency, and can obtain high-quality oxidized sodium alginate with sterility and low endotoxin content. It can be produced on a large scale and quickly, and has broad application prospects.

[0009] An embodiment of the present invention provides an extraction method for oxidized sodium alginate, including the following steps:

[0010] (1) Immerse and wash the oxidized sodium alginate raw material in the first solution in a heterogeneous state; separate the solution and the precipitate to obtain the acidified oxidized sodium alginate precipitate; the first solution includes water, an acid, and a first organic solvent;

[0011] (2) Disperse the acidified oxidized sodium alginate precipitate in the second solution, neutralize it with a base, and adjust the pH value in a heterogeneous state; separate the solution and the precipitate to obtain the neutralized oxidized sodium alginate precipitate; the second solution includes water and a second organic solvent;

[0012] (3) Immerse and dehydrate the neutralized oxidized sodium alginate precipitate with a third organic solvent in a heterogeneous state; separate the solution and the precipitate, and dry the precipitate to obtain oxidized sodium alginate.

[0013] The advantages and technical effects brought by the extraction method of oxidized sodium alginate in the embodiments of the present invention: The extraction method of oxidized sodium alginate is carried out in a heterogeneous system. The oxidized sodium alginate is always in a granular precipitate or gel state. The immersion washing is carried out with the first solution containing an acid to effectively remove impurities in the oxidized sodium alginate; then the heterogeneous precipitate is neutralized in the second solution, and after immersion dehydration and drying, oxidized sodium alginate powder is obtained. The method of the present invention can significantly shorten the extraction time to about 1 day, without going through steps such as dialysis, freeze-drying, repeated dissolution and precipitation, etc. It is simple and easy to operate, greatly improves the preparation efficiency, reduces the production threshold, improves the quality of the product oxidized sodium alginate, and protects the molecular chain length and the number of active aldehyde groups of oxidized sodium alginate. The method of the present invention can achieve aseptic operation throughout the process. The oxidized sodium alginate treated by acidification, organic solvent immersion, and drying can reach a higher aseptic level and low endotoxin content, and can produce high-quality oxidized sodium alginate on a large scale and rapidly, and has significant industrial application value and market prospects in the pharmaceutical industry as a new type of biomedical material.

[0014] In some embodiments, in the step (1), the oxidized sodium alginate raw material is an oxidized sodium alginate product prepared by oxidizing sodium alginate;

[0015] And / or, the acid includes at least one of acetic acid, hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid;

[0016] And / or, the volume percentage of the acid in the first solution is 5% - 20%;

[0017] And / or, the first organic solvent includes at least one of ethanol, methanol, ether, acetone, dichloromethane, and chloroform;

[0018] And / or, the volume percentage of the first organic solvent in the first solution is 5% - 20%;

[0019] And / or, the pH of the first solution is 1 - 5;

[0020] And / or, the time of the impregnation washing is 1 min - 4 h;

[0021] And / or, multiple-step impregnation washing is adopted during the impregnation washing process; the number of times of the stepwise impregnation washing is 5 - 10 times; the impregnation time for a single impregnation washing is 1 - 20 min.

[0022] In some embodiments, the oxidized sodium alginate raw material is an oxidized sodium alginate product prepared by heterogeneous oxidation reaction of sodium alginate;

[0023] And / or, the first solution includes water, acetic acid and ethanol;

[0024] And / or, the volume percentage of acetic acid in the first solution is 5% - 20%;

[0025] And / or, the volume percentage of ethanol in the first solution is 5% - 20%;

[0026] And / or, the pH of the first solution is 2 - 4.

[0027] In some embodiments, in the step (2), the second organic solvent includes at least one of ethanol, methanol, isopropanol, n-butanol, chloroform, acetone or ether;

[0028] And / or, the volume percentage of the second organic solvent in the second solution is 80% - 95%;

[0029] And / or, the base includes at least one of sodium hydroxide, sodium carbonate, sodium bicarbonate;

[0030] And / or, the base is used in the form of an alkali solution; the concentration of the base in the alkali solution is 0.1 - 10 M; the alkali solution includes water and a fourth organic solvent, and the fourth organic solvent includes at least one of ethanol, methanol, isopropanol, n-butanol, chloroform, acetone or ether; the volume percentage of the fourth organic solvent in the alkali solution is 30% - 80%;

[0031] And / or, the time of the neutralization is 2 - 4 h;

[0032] And / or, the pH value is adjusted to 6.5 - 7.5.

[0033] In some embodiments, in the step (3), the third organic solvent includes at least one of ethanol and acetone;

[0034] And / or, the impregnation and dehydration process includes multiple-step impregnation and dehydration; the number of steps of the stepwise impregnation and dehydration is 3-10 times; the time for single impregnation and dehydration is 10 min-2 h;

[0035] And / or, the drying method includes at least one of static volatilization, suction filtration volatilization, reduced-pressure volatilization, drying, or ventilation volatilization.

[0036] In some embodiments, in the multiple-step impregnation and dehydration process, the third organic solvents used in each impregnation and dehydration are the same or different;

[0037] And / or, performing impregnation and dehydration in a heterogeneous state using a third organic solvent includes: first performing preliminary impregnation and dehydration with absolute ethanol, and then performing secondary impregnation and dehydration with anhydrous acetone.

[0038] In some embodiments, in step (1), the sodium alginate raw material is replaced with an oxidation product of a high molecular polysaccharide substance other than the sodium alginate raw material; the high molecular polysaccharide substance includes at least one of cellulose and its derivatives, agarose and its derivatives, hyaluronic acid and its derivatives, chitosan and its derivatives, and starch substances and their derivatives.

[0039] An embodiment of the present invention provides a method for preparing sodium alginate oxide, including the following steps:

[0040] 1) Performing a heterogeneous oxidation reaction on sodium alginate and sodium periodate in an aqueous solution of ethanol, terminating the oxidation reaction, separating the solution and the precipitate, and obtaining a sodium alginate oxide precipitate;

[0041] 2) Using the sodium alginate oxide precipitate as the sodium alginate oxide raw material and performing extraction using the extraction method of sodium alginate oxide described in the embodiment of the present invention to obtain sodium alginate oxide.

[0042] In an embodiment of the present invention, the preparation method of oxidized sodium alginate is carried out in a heterogeneous system, and sodium alginate or oxidized sodium alginate is always in a granular precipitate or gel state, and partially aldehyde-modified oxidized sodium alginate is prepared by a sodium periodate oxidation method in a heterogeneous system. The heterogeneous oxidized sodium alginate precipitate is impregnated and washed with a first solution containing an acid to effectively remove reaction impurities in the oxidized sodium alginate; then the heterogeneous precipitate is neutralized in a second solution, and the oxidized sodium alginate powder is obtained by impregnation, dehydration and drying. The method of the present invention can significantly shorten the preparation time to 1-2 days, without the need for dialysis, freeze-drying, repeated dissolution and precipitation steps, is simple and easy, greatly improves the preparation efficiency, lowers the production threshold, improves the quality of the product oxidized sodium alginate, and protects the molecular chain length and the number of active aldehyde groups of the oxidized sodium alginate. The method of the present invention can achieve aseptic operation throughout the process. Oxidized sodium alginate that has been acidified, impregnated with organic solvents, and dried can achieve a higher level of sterility and a lower endotoxin content. High-quality oxidized sodium alginate can be produced rapidly on a large scale. As a new type of biomedical material, it has significant industrial application value and market prospects in the pharmaceutical industry.

[0043] In some embodiments, in step 1), the reaction time of the heterogeneous oxidation reaction is 2-12 h;

[0044] And / or, the reaction temperature of the heterogeneous oxidation reaction is 4-37°C;

[0045] And / or, the volume percentage of ethanol in the aqueous solution of ethanol is 40-60%;

[0046] And / or, the mass ratio of sodium alginate to sodium periodate is 5:0.01-10;

[0047] And / or, ethylene glycol is added to terminate the oxidation reaction.

[0048] In some embodiments, in step 1), the sodium alginate is replaced with a high molecular weight polysaccharide substance other than sodium alginate; the high molecular weight polysaccharide substance includes at least one of cellulose and its derivatives, agarose and its derivatives, hyaluronic acid and its derivatives, chitosan and its derivatives, and starch substances and their derivatives.

[0049] The present invention provides an oxidized sodium alginate, which is obtained by the method described in the present invention. In the present invention, the oxidized sodium alginate can achieve a higher sterility level and a low endotoxin content, and as a new biomedical material, has significant industrial application value and market prospects in the pharmaceutical industry.

[0050] An embodiment of the present invention provides an application of oxidized sodium alginate, which is used in biomedical, food industry or environmental engineering. In the embodiment of the present invention, the oxidized sodium alginate can achieve a higher sterility level and low endotoxin content, and has significant industrial application value and market prospects in the pharmaceutical industry as a new type of biomedical material. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 is a flow chart of the preparation and extraction of oxidized sodium alginate under laboratory conditions in an embodiment of the present invention.

[0052] Figure 2 is a flow chart of the large-scale preparation and extraction of oxidized sodium alginate under industrial production conditions in another embodiment of the present invention.

[0053] Figure 3 is a flow chart of the preparation and rapid extraction of high-quality oxidized sodium alginate with sterility and low endotoxin in still another embodiment of the present invention.

[0054] Figure 4 is an appearance diagram of oxidized sodium alginate powder with different degrees of oxidation prepared in the embodiment of the present invention.

[0055] Figure 5 is an experimental diagram of the dissolution of iodate impurities in aqueous ethanol solutions with different concentrations.

[0056] Figure 6 is an experimental diagram of the dissolution of iodate impurities in aqueous acetic acid solutions with different concentrations.

[0057] Figure 7 is a state diagram of oxidized sodium alginate soaked in aqueous acetic acid or ethanol solutions with different concentrations.

[0058] Figure 8 is an experimental diagram of the iodate impurity test in Example 4 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0059] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the drawings. The embodiments described below by referring to the drawings are exemplary and are intended to explain the present invention, but should not be construed as limiting the present invention.

[0060] As Figure 5 shown, the inventors have found through research that iodate has extremely low solubility in 80 - 90% organic solvents and is almost insoluble. If a large amount of sodium periodate is used, the removal of reaction impurities may consume an extremely large amount of organic solvents and also take a lot of time, which is not economically viable. At the same time, experimental verification shows that even for 50% organic solvents, the solubility of iodate is also extremely low. Organic solvents in the range of 10 - 30% are required to have a good dissolution effect on iodate. But at this concentration, asFigure 7 As shown, the solubility of oxidized sodium alginate also increases. Therefore, washing with a low concentration of organic solvent will result in a large loss of the oxidized sodium alginate product, which is not conducive to its preparation efficiency.

[0061] In this article, the term: "volume percentage" refers to the volume of a pure liquid substance divided by the sum of the volumes of the pure liquid substances of each component in the mixture.

[0062] An extraction method of oxidized sodium alginate according to an embodiment of the present invention includes the following steps:

[0063] (1) Immersing and washing the oxidized sodium alginate raw material in a first solution in a heterogeneous state; separating the solution and the precipitate to obtain an acidified oxidized sodium alginate (oxidized alginic acid) precipitate; the first solution includes water, an acid, and a first organic solvent;

[0064] (2) Dispersing the acidified oxidized sodium alginate precipitate in a second solution, neutralizing with a base, and adjusting the pH value in a heterogeneous state; separating the solution and the precipitate to obtain a neutralized oxidized sodium alginate precipitate; the second solution includes water and a second organic solvent;

[0065] (3) Immersing and dehydrating the neutralized oxidized sodium alginate precipitate with a third organic solvent in a heterogeneous state; separating the solution and the precipitate, and drying the precipitate to obtain oxidized sodium alginate.

[0066] The extraction method of oxidized sodium alginate according to the embodiment of the present invention is carried out for extraction and purification in a heterogeneous system. The oxidized sodium alginate is always in a granular precipitate or gel state. The first solution containing an acid is used for immersion washing to effectively remove impurities in the oxidized sodium alginate; then the heterogeneous precipitate is neutralized in the second solution, and after immersion dehydration and drying, oxidized sodium alginate powder is obtained. The method of the present invention does not need to go through steps such as dialysis, freeze-drying, repeated dissolution and precipitation, etc. It can significantly shorten the extraction time from the original 7 - 10 days to about 1 day, greatly improving the preparation efficiency, reducing the production threshold, improving the quality of the product oxidized sodium alginate, and protecting the molecular chain length and the number of active aldehyde groups of the oxidized sodium alginate. The method of the present invention can achieve aseptic operation throughout the process. The oxidized sodium alginate treated by acidification, organic solvent immersion, and drying can reach a higher aseptic level and low endotoxin content, and can produce high-quality oxidized sodium alginate on a large scale and quickly, which has significant industrial application value and market prospects in the pharmaceutical industry as a new type of biomedical material.

[0067] In the embodiment of the present invention, in the process of washing the preliminary product of oxidized sodium alginate with a low concentration organic solvent, the loss of oxidized sodium alginate is minimized, the quality of oxidized sodium alginate is improved, and the impurity removal effect is improved to achieve a higher cleanliness level. That is, the solubility of oxidized sodium alginate is extremely low under acidic conditions, the solubility is extremely low in organic solvents at some concentrations, and the dissolution is inhibited in organic solvents at other concentrations. By combining acid and organic solvent, impurities such as iodate can be removed quickly, effectively and at a low dosage, and the dissolution of oxidized sodium alginate molecules in aqueous solutions can be avoided as much as possible.

[0068] In the embodiment of the present invention, the method of the present invention does not need to involve dialysis operation (dialysis for 3-7 days in an aqueous solution state), so that the free aldehyde group of the oxidized sodium alginate is protected, and the breakage of the molecular chain and the instability in the solution state are avoided as much as possible; there is no need to involve freeze-drying operation (1-7 days), so that the oxidized sodium alginate molecules avoid the freeze-thaw process and the dissolution and precipitation process, further improving the quality of the oxidized sodium alginate product; compared with the traditional dialysis, freeze-drying extraction method, or the washing and extraction method of repeated ethanol precipitation, the product quality is greatly improved.

[0069] In some embodiments, in step (1), the oxidized sodium alginate raw material is powder.

[0070] In some embodiments, the entire process of the extraction method of oxidized sodium alginate is carried out in a heterogeneous system, the oxidized sodium alginate is always in a granular precipitate or gel state, and the oxidized sodium alginate precipitate obtained by final drying also presents a fine powder state.

[0071] In some embodiments, in step (1), the oxidized sodium alginate raw material is an oxidized sodium alginate product prepared by an oxidation reaction of sodium alginate;

[0072] Optionally, the oxidized sodium alginate raw material is a solid product separated after an oxidation reaction of sodium alginate;

[0073] Optionally, the oxidized sodium alginate raw material includes partially oxidized sodium alginate;

[0074] Optionally, the oxidized sodium alginate raw material is an oxidized sodium alginate product prepared by a heterogeneous oxidation reaction of sodium alginate; optionally, an oxidized sodium alginate product prepared by a heterogeneous oxidation reaction of sodium periodate; the oxidized sodium alginate raw material includes impurities generated during the heterogeneous oxidation reaction of sodium periodate, for example, unreacted sodium periodate and iodate derivatives after the oxidation reaction of sodium periodate. In the embodiment of the present invention, the extraction method of the present invention can completely remove impurities such as sodium periodate and its reaction products remaining in the oxidation reaction.

[0075] In some embodiments, in the step (1), the acid includes at least one of acetic acid, hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid. Preferably, it is acetic acid.

[0076] In the embodiments of the present invention, the acid in the first solution can be acetic acid, dilute hydrochloric acid, dilute sulfuric acid, dilute nitric acid, phosphoric acid, etc. Among them, hydrochloric acid and sulfuric acid are strong acids. Strong acids may cause relatively severe damage to the molecular weight of oxidized sodium alginate, affecting the quality of the final product. When using them, the concentration needs to be carefully selected, and the temperature and washing time need to be strictly controlled. Acetic acid is the optimal choice. Acetic acid is a weak acid. The acidic environment it provides can effectively avoid the dissolution of oxidized sodium alginate, but does not affect the dissolution of inorganic salt impurities. Its proton dissociation strength can effectively protect the molecular chain of oxidized sodium alginate from being overly damaged. The overall environment is mild, which is conducive to the preparation of high-quality oxidized sodium alginate.

[0077] In some embodiments, in the step (1), the volume percentage of the acid in the first solution is 5% - 20%. Specifically, for example, 5%, 7%, 10%, 12%, 15%, 18%, 20%. The pH of the first solution is 1 - 5. Specifically, for example, 1, 2, 3, 4, 5. Preferably, it is 2 - 4. In the embodiments of the present invention, the solubility of sodium alginate / oxidized sodium alginate in water under the acidic conditions is extremely low, which is conducive to further reducing the loss of oxidized sodium alginate, improving the quality of oxidized sodium alginate, enhancing the impurity removal effect, and achieving a higher cleanliness level.

[0078] In some embodiments, in the step (1), the first organic solvent includes at least one of ethanol, methanol, ether, acetone, dichloromethane, and chloroform. The volume percentage of the first organic solvent in the first solution is 5% - 20%. Specifically, for example, 5%, 7%, 10%, 12%, 15%, 18%, 20%.

[0079] In the embodiments of the present invention, the first organic solvent in the first solution can be ethanol, methanol, ether, acetone, dichloromethane, chloroform, etc. The first organic solvent can change the polarity of the aqueous solution, thereby further reducing the solubility of oxidized sodium alginate in the aqueous solution. 5% - 20% of the first organic solvent inhibits the dissolution of oxidized sodium alginate. When the first organic solvent is not added, the loss of oxidized sodium alginate will increase. Since the oxidized sodium alginate extraction system needs to use organic solvents multiple times, in view of reducing the complexity of the system, ethanol can be selected as the inhibitor for the dissolution of oxidized sodium alginate in the first solution in this washing step, that is, ethanol is selected as the first organic solvent, which can effectively protect oxidized sodium alginate and is conducive to the preparation of high-quality oxidized sodium alginate.

[0080] In the embodiment of the present invention, the feasibility of using 80-90% organic solvent to wash iodate impurities is denied. Although the solubility of sodium alginate / oxidized sodium alginate in 80-90% of the organic solvent is extremely low, the solubility of sodium alginate / oxidized sodium alginate and iodate in organic solvents is highly similar, so it is almost impossible to achieve effective and efficient washing (dissolution removal) of iodate impurities under high concentration organic solvent conditions. Without adding an acidic solvent, it is difficult to wash the precipitate alone with a specific concentration of organic solvent to achieve effective iodate impurity removal and at the same time ensure a high retention rate of oxidized sodium alginate.

[0081] In some embodiments, in step (1), the first solution comprises water, acetic acid and ethanol; optionally, the volume percentage of acetic acid in the first solution is 5%-20%, specifically, for example, 5%, 7%, 10%, 12%, 15%, 18%, 20%; the volume percentage of ethanol in the first solution is 5%-20%, specifically, for example, 5%, 7%, 10%, 12%, 15%, 18%, 20%; optionally, a 10% acetic acid-10% ethanol aqueous solution;

[0082] Optionally, the preparation of the first solution comprises: adding anhydrous ethanol and anhydrous acetic acid to an aqueous solution respectively, and mixing them thoroughly to make the acetic acid and ethanol dissolve in the aqueous solution at the same time to form an acetic acid-ethanol aqueous solution.

[0083] In the embodiment of the present invention, the precipitate washing is performed using an acetic acid-ethanol aqueous solution, which is further beneficial to remove inorganic salt impurities. In the process of washing the oxidized sodium alginate preliminary product with a low concentration organic solvent, the method of reducing the loss of oxidized sodium alginate as much as possible, that is, utilizing the extremely low solubility of sodium alginate / oxidized sodium alginate in water under acidic conditions (pH=1-5), the extremely low solubility in an organic solvent at a certain concentration (50-100%), and the characteristics of being inhibited in dissolving in an organic solvent at a certain concentration (5-20%), combining low concentration acetic acid and ethanol, can not only quickly, effectively, and with low dosage remove impurities such as iodate, but also can avoid the dissolution of oxidized sodium alginate molecules in an aqueous solution as much as possible, making it an effective washing agent.

[0084] In the embodiments of the present invention, the acetic acid concentration is 5%-20%, which is further conducive to obtaining high-quality oxidized sodium alginate. The higher the acetic acid concentration, the lower the solubility of oxidized sodium alginate during the washing process. However, the stronger the acidity of the solution, the easier it is to break the molecular chain of oxidized sodium alginate, reduce the molecular weight, and lower the viscosity of the final product. The ethanol concentration is 5%-20%, which is further conducive to obtaining high-quality oxidized sodium alginate. The higher the ethanol concentration, the lower the solubility of oxidized sodium alginate during the washing process. However, the solubility of inorganic salt impurities is also lower, and the efficiency of washing and removing inorganic salts becomes lower. It is necessary to increase the amount of washing solution and the number of washing times. The lower the ethanol concentration, the higher the solubility of oxidized sodium alginate, and the higher the solubility of inorganic salt impurities, which is conducive to quickly removing impurities, but reduces the yield of oxidized sodium alginate. In particular, more low-molecular-weight partially oxidized sodium alginate dissolves and more is lost.

[0085] In the embodiments of the present invention, an aqueous solution of acetic acid-ethanol is used as the washing reagent for the precipitate. Acetic acid and ethanol need to be dissolved in the aqueous solution at the same time to wash the precipitate. It is not possible to separately use an aqueous solution of acetic acid and an aqueous solution of ethanol for stepwise washing, and the purpose of precipitate washing cannot be achieved.

[0086] In some embodiments, in step (1), the time for immersion washing is 1 min - 4 h. Specifically, for example, 1 min, 5 min, 6 min, 10 min, 20 min, 40 min, 1 h, 2 h, 3 h, 4 h;

[0087] Optionally, the total duration of the immersion washing process is 1 min - 4 h. Specifically, for example, 1 min, 5 min, 6 min, 10 min, 20 min, 40 min, 1 h, 2 h, 3 h, 4 h.

[0088] In the embodiments of the present invention, it is necessary to control the time for immersion washing with the first solution. The time for immersion washing or the total duration of the washing process is controlled within 1 min - 4 h. In a low pH environment, the molecular chain of oxidized sodium alginate will slowly break to a certain extent, and long-term immersion will lead to a decrease in product quality.

[0089] In some embodiments, multiple-step dip washing is employed during the dip washing process; the number of steps of dip washing is 5 - 10 times. Specifically, for example, 5 times, 6 times, 7 times, 8 times, 9 times, 10 times; the dip time for a single dip washing is 1 - 20 min. Specifically, for example, 1 min, 2 min, 3 min, 4 min, 5 min, 10 min, 20 min; during a single dip washing process, the first solution is dispersed with the sodium alginate raw material or the precipitate in an amount 5 - 10 times the volume of the sodium alginate raw material or the precipitate for dip washing. Specifically, for example, 5 times the volume, 6 times the volume, 7 times the volume, 8 times the volume, 9 times the volume, 10 times the volume; after a single dip washing, a centrifugation or suction filtration step is combined to separate the solution and the precipitate.

[0090] In the embodiments of the present invention, the washing process should adopt step-by-step washing instead of one-time washing with a large volume of solution. Step-by-step multiple washing is beneficial to exponentially reduce the content of inorganic salt impurities, thereby achieving the purpose of cost savings. The amount of the first solution used during the washing process can be adjusted according to the amount of impurities in the sodium alginate raw material or the addition amount of sodium periodate during the preparation of sodium alginate by oxidation reaction to prepare sodium alginate.

[0091] In some embodiments, in the step (1), the solution and the precipitate are separated by centrifugation; optionally, the centrifugation speed is 800 - 1000 rpm, and the centrifugation time is 3 - 5 minutes.

[0092] And / or, the solution and the precipitate are separated by suction filtration; optionally, a non-oil pump vacuum machine is used for suction filtration.

[0093] In some embodiments, in the step (1), the sodium alginate raw material is subjected to dip washing in the first solution in a heterogeneous state until iodate cannot be detected in the washing solution; optionally, a silver nitrate detection method is adopted. In the embodiments of the present invention, the sodium alginate raw material contains impurities such as iodate, and the dip washing process is terminated by detecting iodate.

[0094] In some embodiments, before the step (2), the acidified sodium alginate precipitate is washed with an ethanol aqueous solution until residual acid cannot be detected in the washing solution; optionally, the ethanol aqueous solution is an ethanol aqueous solution with a volume percentage of 80 - 95%. Specifically, for example, 80%, 85%, 90%, 95%; the precipitate and the washing solution are separated by methods such as centrifugation or filtration; the washing is repeated multiple times.

[0095] In some embodiments, in step (2), the acidified oxidized sodium alginate precipitate is dispersed in a second solution and neutralized with a base, and the pH value is adjusted in a heterogeneous state; the second organic solvent includes at least one of ethanol, methanol, isopropanol, n-butanol, chloroform, acetone or ether; the volume percentage of the second organic solvent in the second solution is 80%-95%, specifically, for example, 80%, 85%, 90%, 95%. In the embodiments of the present invention, the acidified oxidized sodium alginate precipitate is dispersed in the second solution and the pH value is adjusted in a heterogeneous state.

[0096] In some embodiments, in step (2), neutralization is carried out with a base; optionally, the base includes at least one of sodium hydroxide, sodium carbonate, and sodium bicarbonate; the base is used as an alkaline solution; the concentration of the base in the alkaline solution is 0.1-10 M, specifically, for example, 0.1 M, 1 M, 3 M, 5 M, 10 M; the alkaline solution includes water and a fourth organic solvent, and the fourth organic solvent includes at least one of ethanol, methanol, isopropanol, n-butanol, chloroform, acetone or ether; the volume percentage of the fourth organic solvent in the alkaline solution is 30%-80%, specifically, for example, 30%, 40%, 50%, 60%, 70%, 80%.

[0097] In the embodiments of the present invention, neutralization is carried out using a mixed solution of a fourth organic solvent (such as ethanol)-water of the base, and the concentration of the fourth organic solvent can be selected from 30%-80%. Since the titration amount of the alkaline solution is small, it does not affect the overall environment of the solution. In industrial production, if it is necessary to accelerate the neutralization process, the concentration of sodium hydroxide can be increased to 10 M, and it can be 0.1-1 M in the laboratory environment.

[0098] In some embodiments, in step (2), the time for neutralization is 2-4 h, specifically, for example, 2 h, 3 h, 4 h.

[0099] In the embodiments of the present invention, the neutralization process of oxidized sodium alginate is relatively slow. The lower the oxidation degree of oxidized sodium alginate, the slower the neutralization speed, and the higher the oxidation degree of oxidized sodium alginate, the faster the neutralization speed. Since the molecular chain of oxidized sodium alginate is easily broken in an alkaline environment, it is necessary to control the time for neutralization with the alkaline solution; the total duration of the neutralization process is controlled within 2-4 hours to ensure the quality of the oxidized sodium alginate product.

[0100] In some embodiments, in step (2), the pH value is adjusted to 6.5-7.5, specifically, for example, 6.5, 6.8, 6.9, 7.0, 7.1, 7.2, 7.5. In the embodiments of the present invention, the pH value of the precipitate is adjusted to neutral in a heterogeneous state in the second solution. Adjusting the pH value to neutral facilitates the subsequent use of the product. At the same time, excessive base will increase the solubility of oxidized sodium alginate and also damage the molecular structure.

[0101] In some embodiments, in the step (2), the neutralization is carried out by titration neutralization. Optionally, the acidified oxidized sodium alginate precipitate is slowly titrated and neutralized.

[0102] In some embodiments, in the step (2), the acidified oxidized sodium alginate precipitate is impregnated and neutralized with a second solution.

[0103] In some embodiments, in the step (2), the acidified oxidized sodium alginate precipitate is dispersed in a second solution, and an alkali solution is added dropwise during stirring for titration neutralization; optionally, the second solution is an aqueous solution of 90% ethanol; the alkali solution is a 50% ethanol-water mixed solution of 1M sodium hydroxide.

[0104] In some embodiments, in the step (2), stirring is carried out during the neutralization process. Optionally, the stirring speed is 600 - 1000 rpm. In the embodiments of the present invention, stirring is beneficial to quickly disperse the added alkali solution, making the overall pH change of the system relatively gentle and the reaction mild, and converting the acidified oxidized alginic acid during the pickling process back into sodium alginate.

[0105] In some embodiments, in the step (2), the end point of the neutralization process can be judged by a pH meter or an acid-base indicator;

[0106] The second solution contains a second organic solvent, and it is impossible to monitor the pH value with an ordinary pH meter. It is necessary to use a pH meter equipped with a probe suitable for organic solvents for monitoring. The specific neutral pH value depends on the pH probe used;

[0107] Optionally, the acid-base indicator includes at least one of bromothymol blue (6.0 (yellow) - 7.6 (blue)), methyl red (4.4 - 6.2), neutral red (6.8 - 8.0), phenol red (6.8 - 8.0), cresol red (7.2 - 8.8), thymol blue (8.0 - 9.6); Combinations between different indicators can also be used to enhance the significant phenomenon of the neutralization end point.

[0108] In the embodiments of the present invention, bromothymol blue at a low concentration is considered to have no biological toxicity. When the pH value is slightly neutral, the solution is green. According to experience, the color display range of bromothymol blue in aqueous solution and ethanol solution is similar. When it shows green, the pH value of the finally obtained sodium alginate oxide product aqueous solution is between 6.5 and 7.5. When the solution is light green and the green color does not fade for 0.5 - 1 hour, it is the neutralization end point, and the neutralization process of sodium alginate oxide is completed. The addition amount of the bromothymol blue solution (the stock solution is an anhydrous ethanol solution of 100 mg / mL, and the working solution is a 90% ethanol solution of 1 mg / mL) is 200 μL of the working solution per 50 mL of the total volume (the final concentration is 4 μg / mL), and obvious color changes can be observed. Experiments show that bromothymol blue does not effectively bind to sodium alginate oxide molecules. Due to the extremely high solubility of bromothymol blue in organic solvents (such as ethanol), it can be completely removed without any residue during the subsequent washing process with organic solutions such as ethanol, and can be used as an effective neutralization end point indicator for the reaction system.

[0109] In some embodiments, before the step (3), the sodium alginate oxide precipitate after neutralization is first washed with an aqueous solution of ethanol, and then the step (3) is carried out, and impregnation dehydration is carried out in a heterogeneous state with a third organic solvent.

[0110] Optionally, the aqueous solution of ethanol is an aqueous solution of ethanol with a volume percentage of 80 - 95%, specifically, for example, 80%, 85%, 90%, 95%.

[0111] Optionally, the washing is carried out by impregnation washing.

[0112] Optionally, the washing with the aqueous solution of ethanol includes washing the precipitate 3 - 5 times with an aqueous solution of ethanol with a volume percentage of 80 - 95% and a volume 3 - 5 times that of the precipitate to fully remove impurities such as acid-base indicators and alkali that may be generated or remain during the neutralization process.

[0113] Optionally, the precipitate and the washing solution are separated by methods such as centrifugation or filtration.

[0114] Optionally, the washing is repeated multiple times until no residual sodium hydroxide can be detected in the washing solution.

[0115] In some embodiments, in step (3), the third organic solvent includes at least one of ethanol and acetone; the impregnation dehydration process includes multiple-step impregnation dehydration; the number of steps of the stepwise impregnation dehydration is 3 to 10 times, specifically, for example, 3 times, 4 times, 5 times, 6 times, 7 times, 8 times, 9 times, 10 times; the time for single impregnation dehydration is 10 min to 2 h, specifically, for example, 10 min, 15 min, 20 min, 25 min, 30 min, 1 h, 1.5 h, 2 h; in the process of multiple-step impregnation dehydration, the third organic solvents used in each impregnation dehydration may be the same or different.

[0116] In the embodiments of the present invention, acetone is a powerful dehydrating agent that can quickly remove moisture from the sample, which is very important for the drying treatment of polysaccharides. By using acetone, the moisture content of the sample can be effectively reduced, thereby preventing the growth of microorganisms and the degradation of the sample. During the extraction process, acetone can prevent the oxidation of polysaccharides, which is crucial for maintaining the biological activity and stability of the sample. The volatility of acetone makes it easy to remove during the drying process, so that no residue will be left in the sample. Even if there is any undetected residue of acetone during the treatment process, it can be completely dissolved in the aqueous solution during the use of oxidized sodium alginate, and its trace residue will not affect any properties or functions of oxidized sodium alginate.

[0117] In some embodiments, subjecting the neutralized oxidized sodium alginate precipitate to impregnation dehydration in a heterogeneous state using a third organic solvent includes: first performing preliminary impregnation dehydration with absolute ethanol, and then performing secondary impregnation dehydration with anhydrous acetone;

[0118] Optionally, first use absolute ethanol with a volume 3 to 5 times that of the precipitate, disperse and wash the precipitate 3 to 5 times, and impregnate the precipitate for 10 to 30 minutes each time to perform preliminary impregnation dehydration treatment on the precipitate;

[0119] Optionally, then use anhydrous acetone with a volume 3 to 5 times that of the precipitate, disperse and wash the precipitate 3 to 5 times, and impregnate the precipitate for 10 to 30 minutes each time to perform alcohol removal and dehydration treatment on the precipitate, that is, secondary impregnation dehydration.

[0120] In some embodiments, in step (3), the solution and the precipitate are separated by methods such as centrifugation or filtration.

[0121] In some embodiments, in the step (3), the drying method includes at least one of static volatilization, suction filtration volatilization, reduced-pressure volatilization, drying, or ventilation volatilization; optionally, the suction filtration volatilization adopts reduced-pressure suction filtration; optionally, there is no special limitation on the drying time. For example, the drying time can be more than 10 hours, more than 12 hours, or more than 24 hours to ensure complete removal of the organic solvent. In the embodiments of the present invention, drying completely volatilizes the remaining small amount of the third organic solvent, completely removes the moisture or organic solvent of the product, and obtains high-purity and high-quality sodium alginate oxide powder.

[0122] In some embodiments, after the drying in the step (3), grinding can be performed to make the sodium alginate oxide finer, which is beneficial to rapid dissolution during the application process. In the embodiments of the present invention, since the method of the present invention is carried out in a heterogeneous system throughout the whole process, to a great extent, the sodium alginate oxide retains the powder state of the original raw material, and the morphology is relatively fine particles.

[0123] In some embodiments, each step can be operated under sterile conditions, using sterile-grade reagents, and finally a sterile sodium alginate oxide product can be produced.

[0124] In some embodiments, within 2 - 7 days under conventional culture conditions of sodium alginate oxide, no amplification of bacterial or fungal flora is observed; the endotoxin content is less than 0.5 EU / mL.

[0125] In some embodiments, the extraction method of the sodium alginate oxide does not need to go through dialysis and / or lyophilization.

[0126] In some embodiments, the sodium alginate oxide raw material is replaced with the oxidation product of a high-molecular polysaccharide substance other than the sodium alginate oxide raw material; the high-molecular polysaccharide substance includes at least one of cellulose and its derivatives, agarose and its derivatives, hyaluronic acid and its derivatives, chitosan and its derivatives, starch substances and their derivatives; the oxidation product of the high-molecular polysaccharide substance is prepared by an oxidation reaction of the high-molecular polysaccharide substance; the oxidation reaction is a heterogeneous oxidation reaction; optionally, a heterogeneous oxidation reaction with sodium periodate; the oxidation product of the high-molecular polysaccharide substance includes impurities generated during the heterogeneous oxidation reaction with sodium periodate, for example, unreacted sodium periodate and iodate derivatives after the sodium periodate oxidation reaction.

[0127] In the embodiments of the present invention, the rapid extraction method is mainly based on the dissolution characteristics of sodium alginate / sodium alginate oxide, that is, it is almost insoluble in all organic solvents and has extremely low solubility under acidic conditions; based on the dissolution characteristics of sodium periodate and its reaction products, that is, it is insoluble in most organic solvents but soluble in aqueous solutions; therefore, the rapid extraction method in combination with acidic conditions and organic solvent conditions can effectively achieve rapid washing and drying of the sodium alginate oxide precipitate after the oxidation reaction; this method is applicable to the preparation of oxidation products of high molecular polysaccharide substances that also have (1) insolubility in some common organic solvents (such as ethanol, acetone, dichloromethane, etc.) and (2) insolubility in acidic solutions (such as acetic acid, dilute hydrochloric acid, dilute sulfuric acid, etc.), such as cellulose and its derivatives, agarose and its derivatives, hyaluronic acid and its derivatives, chitosan and its derivatives, and some starch substances and their derivatives, etc.; specific organic solvents and acids can be further selected according to the characteristics of specific high molecular raw materials as needed.

[0128] A method for preparing sodium alginate oxide according to an embodiment of the present invention includes the following steps:

[0129] 1) Perform a heterogeneous oxidation reaction on sodium alginate and sodium periodate in an aqueous solution of ethanol, terminate the oxidation reaction, separate the solution and the precipitate, and obtain a sodium alginate oxide precipitate;

[0130] 2) Use the sodium alginate oxide precipitate as the sodium alginate oxide raw material, and perform extraction using the extraction method of sodium alginate oxide described in the embodiments of the present invention to obtain sodium alginate oxide.

[0131] In the embodiments of the present invention, the method for preparing sodium alginate oxide is carried out in a heterogeneous system. Sodium alginate or sodium alginate oxide is always in a granular precipitate or gel state. The sodium periodate oxidation method under the heterogeneous system is used to prepare partially aldehyde-grouped sodium alginate oxide. The heterogeneous sodium alginate oxide precipitate is impregnated and washed with a first solution containing an acid to effectively remove the reaction impurities in the sodium alginate oxide; then the heterogeneous precipitate is neutralized in a second solution, and after impregnation dehydration and drying, sodium alginate oxide powder is obtained. The method of the present invention can significantly shorten the preparation time to 1-2 days, without going through steps such as dialysis, freeze-drying, repeated dissolution and precipitation, etc. It is simple and easy to operate, greatly improves the preparation efficiency, reduces the production threshold, improves the quality of the product sodium alginate oxide, and protects the molecular chain length and the number of active aldehyde groups of sodium alginate oxide. The method of the present invention can achieve aseptic operation throughout the process. The sodium alginate oxide treated by acidification, organic solvent impregnation, and drying can reach a higher aseptic level and low endotoxin content, and can mass-produce high-quality sodium alginate oxide rapidly. As a new type of biomedical material, it has significant industrial application value and market prospects in the pharmaceutical industry.

[0132] In some embodiments, the entire process of the preparation method of oxidized sodium alginate is carried out in a heterogeneous system, and sodium alginate or oxidized sodium alginate is always in a granular precipitate or gel state, and the oxidized sodium alginate precipitate obtained by final drying also presents a fine powder.

[0133] In some embodiments, in step 1), the sodium alginate is sodium alginate powder.

[0134] In some embodiments, in step 1), there is no particular limitation on the source of the sodium alginate. For example, the sodium alginate may be derived from brown algae. Optionally, the pH value of the sodium alginate is neutral.

[0135] In some embodiments, in step 1), the reaction time of the heterogeneous oxidation reaction is 2-12 h, specifically, for example, 2 h, 6 h, 8 h, 12 h; the reaction temperature of the heterogeneous oxidation reaction is 4-37 ° C, specifically, for example, 4 ° C, 15 ° C, 20 ° C, 25 ° C, 30 ° C, 37 ° C; the heterogeneous oxidation reaction is carried out in the dark; the heterogeneous oxidation reaction is carried out under stirring.

[0136] In the embodiment of the present invention, oxidized sodium alginate with high oxidation reaction quality, high molecular weight and high viscosity can be obtained. Increasing the reaction temperature can improve the oxidation efficiency and reaction degree, but the molecular chain is severely damaged and the molecular weight is greatly reduced; lowering the reaction temperature can avoid molecular chain breakage and obtain high molecular weight and high viscosity oxidation products, but the reaction time needs to be extended.

[0137] In some embodiments, in step 1), the volume percentage of ethanol in the ethanol aqueous solution is 40-60%, specifically, for example, 40%, 45%, 50%, 55%, 60%.

[0138] In some embodiments, in step 1), the mass ratio of sodium alginate to sodium periodate is 5:(0.01-10); specifically, for example, 5:0.01, 5:0.1, 5:0.5, 5:1, 5:2, 5:5, 5:10. In the embodiments of the present invention, the amount of periodate added can be adjusted as needed to prepare oxidized sodium alginate with different degrees of aldehyde formation, and the degree of oxidation mainly depends on the amount of sodium periodate added, the temperature and time of the oxidation reaction, etc.

[0139] In a specific embodiment, through experiments and measurements, the corresponding solutions of the addition amount of sodium periodate and the final oxidation degree of oxidized sodium alginate are shown in Table 1. The oxidation degree refers to the percentage of the number of monomers with o-dialdehyde after the oxidation reaction in the total number of monomers of sodium alginate. The calculation formula is OD = (nCHO / 2) / (w sodium alginate / 198.11), where 198.11 is the approximate value of the molecular weight of sodium alginate monomers.

[0140] Table 1

[0141]

[0142] In Table 1, 5 g of sodium alginate was dispersed in 25 mL of absolute ethanol to obtain a sodium alginate suspension; sodium periodate was dissolved in 25 mL of water to obtain a sodium periodate solution; under stirring at 600 rpm, the sodium periodate solution was slowly added to the sodium alginate suspension, and the reaction was carried out in the dark at 20 °C for 6 hours; 5 mL of ethylene glycol was added and reacted for 30 min to completely consume sodium periodate and terminate the reaction; the washing, neutralization, and drying were carried out using the steps of the extraction method described in the examples of the present invention. The oxidation degree was determined by detecting the aldehyde group content of oxidized sodium alginate, and quantitative calculation was mainly carried out by the hydroxylamine hydrochloride method. The amount of HCl generated in the reaction was determined by neutralization titration, and thus the aldehyde group content in oxidized sodium alginate was deduced.

[0143] In some embodiments, in step 1), the heterogeneous oxidation reaction of sodium alginate and sodium periodate is carried out in an aqueous solution of ethanol.

[0144] Optionally, first disperse sodium alginate in absolute ethanol to obtain a sodium alginate suspension; dissolve sodium periodate in water to obtain a sodium periodate solution; under stirring, add the sodium periodate solution to the sodium alginate suspension; optionally, add it dropwise slowly; optionally, the stirring speed is 600 - 800 rpm; optionally, adding the sodium periodate solution to the sodium alginate suspension to obtain an ethanol aqueous solution system with a final concentration of 50%.

[0145] In some embodiments, in step 1), in the heterogeneous oxidation reaction system, the ratio between sodium alginate and the total volume of the system can be 1 g per 5 mL; optionally, the total volume of the system is the total volume of the aqueous solution of ethanol, specifically, for example, the total volume of 50% ethanol aqueous solution.

[0146] In some embodiments, in step 1), the heterogeneous oxidation reaction is carried out under stirring; optionally, the stirring speed is 600 - 800 rpm, and oxidized sodium alginate precipitate with uniform oxidation reaction can be obtained.

[0147] In some embodiments, in step 1), ethylene glycol is added to terminate the oxidation reaction; optionally, the addition amount of ethylene glycol is 1 / 10 - 1 / 3 of the total volume of the heterogeneous oxidation reaction system or the total volume of the aqueous ethanol solution; the time for using ethylene glycol to terminate the reaction is 20 - 40 min, optionally 30 min; the temperature of the reaction-terminating system is maintained at room temperature or 20 °C; a stirring device is used during the reaction termination process, and the stirring speed is 600 - 800 rpm. In the embodiments of the present invention, an excessive amount of ethylene glycol is used to terminate the reaction, and the unreacted sodium periodate in the system is completely consumed.

[0148] In some embodiments, before step 2), the oxidized sodium alginate precipitate is washed with an aqueous ethanol solution; optionally, an aqueous ethanol solution with a volume percentage of 80 - 95% is used, specifically, for example, 80%, 85%, 90%, 95%; optionally, impregnation washing is used; optionally, it is repeated multiple times.

[0149] In some embodiments, in a laboratory environment, the precipitate and the solution are separated by centrifugation; the centrifugation speed is 800 - 1000 rpm; the centrifugation time is 3 - 5 minutes;

[0150] In an industrial production environment, the precipitate and the solution are separated by vacuum filtration or pressure filtration; optionally, quantitative filter paper or an anti-organic solvent filter membrane with a pore size of 0.22 - 20 μm is used for suction filtration.

[0151] In some embodiments, each step can be operated under sterile conditions, and sterile-grade reagents are used, and finally a sterile oxidized sodium alginate product can be produced.

[0152] In some embodiments, the sodium alginate raw material is impregnated in a 75% aqueous ethanol solution for 6 - 24 hours, and it can be detected that the sodium alginate solution is completely sterile, and no bacterial colonies grow after being placed in a 37 °C environment for 3 - 7 days.

[0153] In some embodiments, if there are requirements for the endotoxin level of oxidized sodium alginate, sodium alginate with a low endotoxin content can be used as the production raw material, or an endotoxin removal step can be added during the production process;

[0154] Optionally, Triton X-114 is used to impregnate and wash the seaweed raw material or the sodium alginate raw material, and endotoxin can be effectively removed;

[0155] Using a 0.1 M aqueous sodium hydroxide solution or a 75% ethanol solution of 0.1 M sodium hydroxide to soak the seaweed raw material or the sodium alginate raw material for more than 4 hours or heat and boil with alkali for more than 2 hours can effectively remove endotoxin;

[0156] Soaking the seaweed raw material or sodium alginate raw material in 0.1M dilute hydrochloric acid for more than 4 hours or heating and acid-boiling for more than 2 hours can effectively remove endotoxins.

[0157] In the embodiments of the present invention, due to the good stability of sodium alginate, the step of removing endotoxins will not strongly damage the structure of sodium alginate itself. If strong acids or bases are used, attention should be paid to the treatment time, and finally the sodium alginate should be adjusted to neutrality to facilitate the subsequent oxidation and extraction processes. Similarly, during the subsequent treatment process, the strong oxidation reaction of sodium periodate and the washing process with acidic organic solvents are beneficial to further sterilization and reduction of the endotoxin level. It has been verified by experiments that after the raw materials are treated to remove endotoxins, the endotoxin content of the prepared sodium alginate oxide product is relatively low, controlled at a level less than 0.5 EU / mg; after strict endotoxin removal treatment, it can be controlled at a level less than 0.03 EU / mg.

[0158] In some embodiments, the organic solvents used, such as acetic acid, ethanol, acetone, etc., can be purified and recovered by distillation or fractional distillation, with simple operation and can be reused in principle.

[0159] In some embodiments, the reaction derivatives of sodium periodate generated during the process, such as sodium iodate, can be precipitated and extracted, collected as by-products of the reaction, and can be recycled in principle.

[0160] In some embodiments, in step 1), the sodium alginate is replaced with a high molecular polysaccharide substance other than sodium alginate; the high molecular polysaccharide substance includes at least one of cellulose and its derivatives, agarose and its derivatives, hyaluronic acid and its derivatives, chitosan and its derivatives, and starch substances and their derivatives.

[0161] A sodium alginate oxide according to an embodiment of the present invention is obtained by the method described in the embodiment of the present invention. In the embodiment of the present invention, the sodium alginate oxide can reach a higher sterility level and a low endotoxin content, and has significant industrial application value and market prospects in the pharmaceutical industry as a new type of biomedical material.

[0162] In the embodiments of the present invention, high-purity sodium alginate oxide with lower cost and high-quality sodium alginate oxide with sterility and low endotoxin content are provided. According to the raw materials, facilities, and labor and time costs used, the estimation is as follows: (1) For small-batch high-purity sodium alginate oxide, it is about 30 - 50 yuan / g; (2) For small-batch sterile and low-endotoxin sodium alginate oxide, it is about 150 - 300 yuan / g; (3) For large-batch high-purity sodium alginate oxide, it is about 4 yuan / g or 3500 - 4000 yuan / kg; (4) For large-batch sterile and low-endotoxin sodium alginate oxide, it is about 40 yuan / g or 35000 - 40000 yuan / kg. The estimated price is much lower than the current market price (the lowest is about 500 - 700 yuan / g), which plays an important role in the commercialization of sodium alginate oxide and the promotion of its usage scenarios.

[0163] In some embodiments, since the product sodium alginate oxide powder is heat-sensitive, it should be stored in a light-proof environment at 4°C for short-term storage and at -20°C for long-term storage, away from strong acids, strong alkalis, strong oxidants, etc.

[0164] An application of sodium alginate oxide in the embodiments of the present invention, wherein the sodium alginate oxide is used in biomedical, food industry, or environmental engineering. In the embodiments of the present invention, sodium alginate oxide can achieve a higher sterility level and low endotoxin content, and has significant industrial application value and market prospects in the pharmaceutical industry as a new type of biomedical material.

[0165] In some embodiments, the sodium alginate oxide is used as a biomedical material.

[0166] In some embodiments, the sodium alginate oxide is used in at least one of degradable gel materials, drug controlled-release materials, cell culture carriers, tissue engineering scaffolds, and medical biological adjuvants. In the embodiments of the present invention, the preparation method of sodium alginate oxide is simple and easy to control, the raw materials are easily available, the cost is low, it can be mass-produced, and it is easy to promote and apply; the obtained sodium alginate oxide with high sterility, high cleanliness, and high quality can be used in various applications such as degradable gel materials, drug controlled-release materials, and cell culture carriers.

[0167] The following describes the present invention with reference to specific embodiments. It should be noted that these embodiments are only descriptive and do not limit the present invention in any way.

[0168] Example 1: Preparation and rapid extraction of sodium alginate oxide in a laboratory environment

[0169] This example adopts the process shown in Figure 1 to carry out the preparation and rapid extraction of sodium alginate oxide in a laboratory environment. Specifically, it includes the following steps:

[0170] (1) Take 3 g of sodium alginate powder from brown algae (Sigma-Aldrich, 71238) as the reaction raw material, disperse it in 15 mL of absolute ethanol to obtain a sodium alginate suspension; respectively take 0.6416 g, 1.604 g, and 2.887 g of sodium periodate (for preparing oxidized sodium alginate with oxidation degrees of 20%, 50%, and 90% respectively), dissolve them in 15 mL of pure water to obtain sodium periodate solutions; first add the sodium alginate suspension into a 50 mL beaker, and under stirring at a speed of 600 rpm, slowly add the sodium periodate solution into the sodium alginate suspension, and react for 6 hours in the dark at 20 °C; add 3 mL of ethylene glycol and react for 30 min to completely consume sodium periodate and terminate the oxidation reaction; centrifuge the reaction product at a speed of 1000 rpm for 3 min, discard the supernatant to obtain oxidized sodium alginate precipitate;

[0171] (2) Add 40 mL of 90% ethanol aqueous solution, use a vortex mixer to oscillate and disperse the precipitate for washing; centrifuge at a speed of 1000 rpm for 3 min, discard the supernatant; repeat the washing with ethanol aqueous solution for a total of 3 times;

[0172] (3) Add 40 mL of 10% ethanol - 10% acetic acid aqueous solution, use a vortex mixer to oscillate and disperse the precipitate for impregnation washing, and the single impregnation washing time is 5 - 10 minutes to dissolve iodate impurities; centrifuge at a speed of 1000 rpm for 5 min, discard the supernatant; repeat the washing with acetic acid - ethanol aqueous solution for about 5 times until iodate impurities cannot be detected in the supernatant (silver nitrate detection method);

[0173] (4) Add 40 mL of 90% ethanol aqueous solution, use a vortex mixer to oscillate and disperse the precipitate for washing; centrifuge at a speed of 1000 rpm for 5 min, discard the supernatant; repeat the washing with ethanol aqueous solution for a total of 5 times, and at this time the mass content of acetic acid in the supernatant < 10 -6 %;

[0174] (5) Resuspend the precipitate in 40 mL of 90% ethanol solution, transfer it to a 50 mL beaker for sodium hydroxide neutralization reaction; under stirring at a speed of 800 rpm, add 200 μL of bromothymol blue (Bicman Biotech, final concentration of 4 μg / mL) solution as an acid - base indicator, and slowly drip 50% ethanol aqueous solution of 1 M sodium hydroxide to adjust the pH value of the oxidized sodium alginate powder to neutral in a heterogeneous system until the solution shows light green and does not change color within 30 min, and the neutralization time is about 3 hours. Separate the precipitate by suction filtration of the reaction product using a fine quantitative filter paper; each time after suction filtration, add 40 mL of 90% ethanol aqueous solution to disperse the precipitate and perform suction filtration again; repeat the suction filtration operation 5 times, and at this time sodium hydroxide cannot be detected in the filtrate;

[0175] (6) Transfer the precipitate to a 50 mL centrifuge tube, add 40 mL of anhydrous ethanol and soak for 2 hours to dehydrate. Repeat this operation 3 times; centrifuge at 1000 rpm for 5 minutes and discard the supernatant;

[0176] (7) Add 20 mL of anhydrous acetone and immerse for 2 hours to dehydrate, repeat this operation 3 times; centrifuge at 1000 rpm for 5 minutes, discard the supernatant; place in a fume hood to evaporate the acetone to completely remove the residual acetone components; finally obtain dry oxidized sodium alginate precipitate (powder).

[0177] After testing, the oxidation degree of the obtained oxidized sodium alginate is consistent with the theoretical value, which is 20.7%, 49.5% and 88.7% respectively. The yield / feed ratio of the three oxidized sodium alginate with different oxidation degrees are: 2.5724g / 3.0014g, 2.4912g / 2.9998g, 2.3554g / 3.0008g respectively. The preparation time used is 6-8 hours for oxidation reaction, 3-5 hours for washing and neutralization, and about 24 hours for dehydration and drying, and the total time does not exceed 48 hours.

[0178] In Example 1, an aqueous solution of 10% acetic acid-10% ethanol is used as a washing solvent, which can not only remove impurities such as iodate quickly, effectively and at a low dosage, but also avoid the dissolution of oxidized sodium alginate molecules in the aqueous solution as much as possible, thereby reducing the loss of oxidized sodium alginate, improving the quality of oxidized sodium alginate, and achieving a higher cleanliness level.

[0179] Example 1 is only a typical example of preparing and rapidly extracting oxidized sodium alginate with different oxidation degrees using low-cost raw material sources, simple consumables and experimental equipment in a laboratory environment, and does not represent the average or highest level of the final preparation effect of high-quality oxidized sodium alginate using this technical solution. After optimization and verification, better preparation results can be achieved.

[0180] Example 2: Verification of the feasibility of large-scale preparation and extraction of oxidized sodium alginate under industrial production environment

[0181] This embodiment adopts Figure 2 The process shown is scaled up for production to verify the feasibility of large-scale preparation and extraction of oxidized sodium alginate in an industrial production environment. Specifically, the following steps are included:

[0182] (1) Take 20 g of sodium alginate powder from brown algae as the reaction raw material, disperse it in 100 mL of absolute ethanol to obtain a sodium alginate suspension; take 10.693 g of sodium periodate (for preparing sodium alginate with an oxidation degree of 50%), dissolve it in 100 mL of pure water to obtain a sodium periodate solution; use a 250 mL beaker as the oxidation reaction container, first add the sodium alginate suspension, and while stirring at a speed of 800 rpm, slowly add the sodium periodate solution to the sodium alginate suspension, and react under light avoidance at 20 °C for 6 hours; add 20 mL of ethylene glycol and react for 30 min to completely consume sodium periodate and terminate the oxidation reaction; transfer the reaction product to a suction filtration device (a sintered glass suction filtration device with a capacity of 300 mL), and use fast qualitative filter paper for suction filtration operation to separate the precipitate to obtain a sodium alginate precipitate;

[0183] (2) Add 200 mL of 90% ethanol aqueous solution, use a glass stirring rod to stir and disperse the precipitate for washing; perform suction filtration under reduced pressure to remove the washing solution; repeat the washing with ethanol aqueous solution for a total of 3 times;

[0184] (3) Add 200 mL of an aqueous solution of 10% ethanol - 10% acetic acid, use a glass stirring rod to stir and disperse the precipitate for impregnation washing, and the single impregnation washing time is 5 - 10 minutes to dissolve iodate impurities; perform suction filtration under reduced pressure to remove the washing solution; repeat the washing with an aqueous solution of acetic acid - ethanol for a total of about 5 times until iodate impurities cannot be detected in the supernatant;

[0185] (4) Add 200 mL of 90% ethanol aqueous solution, use a glass stirring rod to stir and disperse the precipitate for washing; perform suction filtration under reduced pressure to remove the washing solution; repeat the washing with ethanol aqueous solution for a total of 5 times;

[0186] (5) Resuspend the precipitate in 200 mL of 90% ethanol solution, transfer it to a 250 mL beaker for sodium hydroxide neutralization reaction; while stirring at a speed of 1000 rpm, add 1 mL of bromothymol blue solution as an acid - base indicator, and slowly drip 50% ethanol aqueous solution of 1 M sodium hydroxide to adjust the pH value of the sodium alginate powder to neutral in a heterogeneous system until the solution shows light green and does not change color within 30 min, and the neutralization time is about 3 hours. Transfer the reaction product to a suction filtration device, and use fine quantitative filter paper for suction filtration operation to separate the precipitate; each time after suction filtration, add 200 mL of 90% ethanol aqueous solution to disperse the precipitate and perform suction filtration again; repeat the suction filtration operation 5 times, and at this time, sodium hydroxide cannot be detected in the filtrate;

[0187] (6) Transfer the precipitate to a 250 mL flask, add 200 mL of absolute ethanol for impregnation for 2 hours for dehydration, and repeat this operation 3 times; perform suction filtration under reduced pressure to remove the liquid component;

[0188] (7) Add 100 mL of anhydrous acetone and soak for 2 hours for dehydration, repeat this operation 3 times; perform vacuum filtration to remove the liquid component; place in a vacuum drying device to volatilize the acetone, slowly adjust the pressure to about -0.1 MPa, so that the residual acetone component is completely removed; finally, obtain a dry oxidized sodium alginate precipitate.

[0189] After testing, the oxidation degree of the prepared oxidized sodium alginate is close to the theoretical value, and the oxidation degree is 53.5%; the yield / feed ratio is 17.65g / 20.00g. The preparation time is 6-8 hours for oxidation reaction, 3-5 hours for washing and neutralization, and 24-48 hours for dehydration and drying, and the total time does not exceed 72 hours.

[0190] In Example 2, impurities such as iodate can be removed quickly, effectively and at a low dosage, and the dissolution of oxidized sodium alginate molecules in the aqueous solution can be avoided as much as possible, thereby reducing the loss of oxidized sodium alginate, improving the quality of oxidized sodium alginate, and achieving a higher cleanliness level.

[0191] Example 2 is only an experimental example of preparing and rapidly extracting oxidized sodium alginate in a laboratory environment using low-cost raw material sources, simulating raw materials used in an industrial environment, and possible industrial production equipment. It does not represent the average and maximum levels of the final preparation effect of high-quality oxidized sodium alginate using this technical solution in an industrial environment, nor does it represent the batch output and production efficiency after scaled-up production.

[0192] In an industrial environment, the reaction vessel can be replaced with a large-capacity reactor, and the single raw material feeding amount should be able to be enlarged to at least 10-100kg; the suction filtration device can be replaced with a large-volume filter press device, and the single filtration liquid volume can be enlarged to at least 10-100L; the acid-base indicator can be replaced with a pH monitor to achieve real-time monitoring and fine control of the pH value; the vacuum drying device can be replaced with a blast drying device to accelerate the volatilization of acetone; the product precipitate can be ground by a grinder to achieve a more delicate sodium periodate powder preparation; the organic solvents such as acetic acid, ethanol and acetone used in the preparation process can be recovered by simple distillation and fractionation operations, and can be reused to reduce costs and increase efficiency. After optimization and verification, better large-scale production effects can be achieved.

[0193] Example 3: Verification of the feasibility of sterile, low-endotoxin, high-quality oxidized sodium alginate preparation and rapid extraction

[0194] This embodiment adopts Figure 3 The process shown in the figure is to prepare and quickly extract sterile, low-endotoxin, high-quality oxidized sodium alginate in a laboratory environment. Specifically, it includes the following steps:

[0195] Take 3 g of sodium alginate powder from brown algae (Sigma-Aldrich, 71238) as the reaction raw material, and perform endotoxin removal treatment in two ways respectively:

[0196] (1) Immerse in 0.1 M dilute hydrochloric acid solution for 6 h (under stirring at 600 rpm);

[0197] (2) Use an aqueous solution of 1% Triton X-114, soak in an ice bath for 30 min (under stirring at 600 rpm), heat up to 37 °C, after obvious stratification appears in the solution, centrifuge at 12000 rpm for 5 min at room temperature, aspirate the supernatant, and repeat 2 times; repeat washing 5 times with endotoxin-free water.

[0198] After endotoxin removal treatment, perform sterilization by soaking in 75% ethanol for 6 h (continuously mixing with a rotary mixer). Thus, endotoxin removal and sterilization of the raw material sodium alginate can be carried out.

[0199] Use the Xiamen Bai'ande Limulus amebocyte lysate microgel method reagent (sensitivity 0.5 EU / mL) for detection, and the endotoxin level of the 2.5% sodium alginate solution was measured to be <0.5 EU / mL. Prepare a 2.5% sodium alginate solution with 5% glucose, incubate at 37 °C for 48 hours, and no obvious bacterial or fungal flora was observed under the microscope.

[0200] In a heterogeneous solution, adjust the pH value of the sodium alginate raw material to neutral, and then use the method in Example 1. Subsequently, prepare sodium alginate oxide with oxidation degrees of 20%, 50%, and 90% using the same operation steps. The solutions used throughout the process are filtered through a 0.22 μm sterile filter to ensure no new bacterial / fungal sources are introduced. After the preparation and rapid extraction of sodium alginate oxide, monitor the endotoxin level and sterility of the sodium alginate oxide product. The endotoxin level of the 10% sodium alginate oxide solution was measured to be <0.5 EU / mL. Prepare a 10% sodium alginate solution with 5% glucose, incubate at 37 °C for 72 hours, and no obvious bacterial or fungal flora was observed under the microscope. It can prove the effective control of the endotoxin level and the sterility of the prepared product.

[0201] In an industrial production environment, control of endotoxin level and bacterial level should be carried out starting from raw materials. For example, during the process of extracting sodium alginate from brown algae, it should be carried out in a sterile environment, and through operations such as acidification and alkalization, the purpose of reducing endotoxin level and sterilization can be effectively achieved, so as to optimize the industrial production process, thereby preparing high-quality sodium alginate oxide products with high cleanliness (low endotoxin content, high sterility) suitable for biomedical applications.

[0202] This example is only a typical case for verifying the feasibility of preparing and rapidly extracting high-quality oxidized sodium alginate with sterility and low endotoxin under laboratory environment, using low-cost raw material sources, as well as simple consumables and experimental equipment. It does not represent the average and highest levels of the final preparation effect of high-quality oxidized sodium alginate with low endotoxin and sterility using this technical solution. Through optimization and verification, better preparation results can be achieved.

[0203] Example 4: Verifying the Feasibility of Washing Oxidized Sodium Alginate Using the Method of the Present Invention

[0204] This example adopts the process as shown in Figure 1 to prepare and rapidly extract oxidized sodium alginate under laboratory environment. And the effectiveness and reliability of the method are verified through relevant characterization methods.

[0205] According to the method in Example 1, oxidized sodium alginate with oxidation degrees of 20%, 50%, and 90% is prepared with the same operation steps. As shown in Figure 4 , the prepared oxidized sodium alginate product is in the form of fine-textured powder. The one with low oxidation degree shows a certain light yellow color, and the higher the oxidation degree, the whiter the powder color.

[0206] Sodium periodate and its iodate derivatives (impurities) after oxidation reaction are obtained by the reaction of sodium periodate and ethylene glycol, and are used to test the solubility of iodate impurities in organic solvent aqueous solutions of different types and different mass percentage concentrations (especially acetic acid aqueous solution and ethanol aqueous solution).

[0207] Figure 5 is the experimental diagram of the dissolution of iodate derivatives (impurities) after the oxidation reaction of sodium periodate in ethanol aqueous solutions of different concentrations. It can be clearly seen from Figure 5 that under higher concentration ethanol aqueous solutions (50%, 75%, 100%), the solubility of iodate impurities is extremely low, and it is difficult to effectively remove iodate impurities. Ethanol aqueous solution with a lower concentration (25%) can dissolve iodate impurities, but at the same time, the solubility of sodium alginate / oxidized sodium alginate is also relatively high.

[0208] Figure 6 is the experimental diagram of the dissolution of iodate derivatives (impurities) after the oxidation reaction of sodium periodate in acetic acid aqueous solutions of different concentrations. It can be clearly seen from Figure 6 that under acetic acid solutions with different concentrations (25%, 50%, 75%), the solubility of iodate impurities is extremely high, and almost a small amount of acetic acid solution can effectively remove iodate impurities. At the same time, the acidic condition is beneficial to reducing the solubility of sodium alginate / oxidized sodium alginate to the greatest extent.

[0209] Figure 7 is the state diagram of oxidized sodium alginate soaked in acetic acid or ethanol with different concentrations. It can be seen fromFigure 7 It can be found that by soaking the oxidized sodium alginate product with 50% oxidation degree in acetic acid and ethanol solutions with different concentrations, the morphology of the oxidized sodium alginate does not change significantly. The oxidized sodium alginate soaked in acetic acid is partially acidified to oxidized alginic acid, which may present a certain degree of transparent colloidal precipitate in a low-concentration aqueous solution and can be restored to an opaque powdery precipitate after neutralization with sodium hydroxide.

[0210] Figure 8 It is the experimental diagram of the iodate impurity test in Example 4 of the present invention. Silver nitrate was added dropwise to the sodium periodate solution, the solution of the iodate derivative impurity which is the reaction product of sodium periodate and ethylene glycol, the unwashed oxidized sodium alginate solution, and the washed oxidized sodium alginate solution respectively. The precipitation reaction of silver nitrate was used to monitor whether the washed product contains residual sodium periodate or iodate impurities.

[0211] As Figure 8 shown, for the 50% oxidized sodium alginate aqueous solution with a mass percentage concentration of 10% obtained in step (1) that was unwashed, after titration with silver nitrate solution, obvious white precipitates (indicating that the solution contains iodate impurities) appeared, indicating that iodate impurities exist in the unwashed oxidized sodium alginate.

[0212] For the 50% oxidized sodium alginate aqueous solution with a mass percentage concentration of 10% prepared and extracted in step (7) (washed), after titration with silver nitrate solution, no obvious black precipitates (indicating that the solution contains sodium periodate) or white precipitates (indicating that the solution contains iodate impurities) appeared, which can prove that the iodate impurities have been effectively removed.

[0213] This example is only a typical example for verifying the rationality and feasibility of the technical solution used in the present invention under a laboratory environment, using low-cost raw material sources, as well as simple consumables and experimental equipment, and does not represent the average or highest level of the preparation and rapid extraction effects of high-quality oxidized sodium alginate using this technical solution. Through optimization and verification, better preparation results can be achieved.

[0214] In the present invention, the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0215] Although the above embodiments have been shown and described, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions, and variations made by those of ordinary skill in the art to the above embodiments are within the scope of protection of the present invention.

Claims

1. A method for extracting oxidized sodium alginate, characterized in that, It includes the following steps: (1) Immerse and wash the oxidized sodium alginate raw material in a heterogeneous state in the first solution; separate the solution and the precipitate to obtain an acidified oxidized sodium alginate precipitate; the first solution includes water, an acid, and a first organic solvent; The oxidized sodium alginate raw material is an oxidized sodium alginate product prepared by the oxidation reaction of sodium alginate with sodium periodate; the volume percentage of the acid in the first solution is 5%-20%; the volume percentage of the first organic solvent in the first solution is 5%-20%; (2) Disperse the acidified oxidized sodium alginate precipitate in the second solution, neutralize it with a base, and adjust the pH value in a heterogeneous state; separate the solution and the precipitate to obtain a neutralized oxidized sodium alginate precipitate; the second solution includes water and a second organic solvent; (3) Immerse and dehydrate the neutralized oxidized sodium alginate precipitate in a heterogeneous state with a third organic solvent; separate the solution and the precipitate, and dry the precipitate to obtain oxidized sodium alginate.

2. The extraction method of oxidized sodium alginate according to claim 1, wherein, In the step (1), the acid includes at least one of acetic acid, hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid; and / or, the first organic solvent includes at least one of ethanol, methanol, ether, acetone, dichloromethane, and chloroform; and / or, the pH of the first solution is 1-5; and / or, the time of the immersion washing is 1 min-4 h; and / or, multiple-step immersion washing is adopted during the immersion washing; the number of times of the step-by-step immersion washing is 5-10 times; the immersion time for a single immersion washing is 1-20 min.

3. The extraction method of oxidized sodium alginate according to claim 2, wherein The oxidized sodium alginate raw material is an oxidized sodium alginate product prepared by a heterogeneous oxidation reaction of sodium alginate; and / or, the first solution includes water, acetic acid, and ethanol; and / or, the volume percentage of acetic acid in the first solution is 5%-20%; and / or, the volume percentage of ethanol in the first solution is 5%-20%; and / or, the pH of the first solution is 2-4.

4. The extraction method of oxidized sodium alginate according to claim 1, characterized in that, In the step (2), the second organic solvent includes at least one of ethanol, methanol, isopropanol, n-butanol, chloroform, acetone, or ether; and / or, the volume percentage of the second organic solvent in the second solution is 80%-95%; and / or, the base includes at least one of sodium hydroxide, sodium carbonate, and sodium bicarbonate; and / or, the base is used in the form of an alkali solution; the concentration of the base in the alkali solution is 0.1-10M; the alkali solution includes water and a fourth organic solvent, and the fourth organic solvent includes at least one of ethanol, methanol, isopropanol, n-butanol, chloroform, acetone, or ether; the volume percentage of the fourth organic solvent in the alkali solution is 30%-80%; and / or, the time of the neutralization is 2-4 h; and / or, adjust the pH value to 6.5-7.

5.

5. The extraction method of oxidized sodium alginate according to claim 1, characterized in that, In the step (3), the third organic solvent includes at least one of ethanol and acetone; and / or, the immersion dehydration process includes multiple-step immersion dehydration; the number of times of the step-by-step immersion dehydration is 3-10 times; the immersion time for a single immersion dehydration is 10 min-2 h; And / or, the drying method includes at least one of static volatilization, suction filtration volatilization, reduced-pressure volatilization, drying, or ventilation volatilization.

6. The extraction method of oxidized sodium alginate according to claim 5, wherein, In the multiple-step impregnation dehydration process, the third organic solvents used in each impregnation dehydration may be the same or different; And / or, the impregnation dehydration using the third organic solvent in a heterogeneous state includes: first performing preliminary impregnation dehydration with absolute ethanol, and then performing secondary impregnation dehydration with anhydrous acetone.

7. The extraction method of oxidized sodium alginate according to claim 1, characterized in that, In step (1), the sodium alginate raw material is replaced with an oxidation product of a high molecular polysaccharide substance other than the sodium alginate raw material; the oxidation product of the high molecular polysaccharide substance is prepared by the sodium periodate oxidation reaction of the high molecular polysaccharide substance; the high molecular polysaccharide substance includes at least one of cellulose and its derivatives, agarose and its derivatives, hyaluronic acid and its derivatives, chitosan and its derivatives, and starch substances and their derivatives.

8. A preparation method of oxidized sodium alginate, characterized in that, It includes the following steps: 1) Performing a heterogeneous oxidation reaction on sodium alginate and sodium periodate in an aqueous solution of ethanol, terminating the oxidation reaction, separating the solution and the precipitate, and obtaining a sodium alginate oxidation precipitate; 2) Using the sodium alginate oxidation precipitate as the sodium alginate raw material, and extracting it by using the extraction method of sodium alginate oxidation according to any one of claims 1-7 to obtain sodium alginate oxidation.

9. The preparation method of oxidized sodium alginate according to claim 8, characterized in that, In step 1), the reaction time of the heterogeneous oxidation reaction is 2-12 h; And / or, the reaction temperature of the heterogeneous oxidation reaction is 4-37 °C; And / or, the volume percentage of ethanol in the aqueous solution of ethanol is 40-60%; And / or, the mass ratio of sodium alginate to sodium periodate is 5:0.01-10; And / or, adding ethylene glycol to terminate the oxidation reaction; And / or, replacing the sodium alginate with a high molecular polysaccharide substance other than sodium alginate; the high molecular polysaccharide substance includes at least one of cellulose and its derivatives, agarose and its derivatives, hyaluronic acid and its derivatives, chitosan and its derivatives, and starch substances and their derivatives.

10. An oxidized sodium alginate, characterized in that, Obtained by using the method according to any one of claims 1-7 or obtained by using the method according to claim 8 or 9.

11. Use of the oxidized sodium alginate according to claim 10, characterized in that, The sodium alginate oxidation is used in biomedicine, the food industry, or environmental engineering.

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