Oxidized sodium alginate as well as preparation, extraction and application thereof

Abstract

The invention discloses oxidized sodium alginate as well as preparation, extraction and application thereof. The extraction method of the oxidized sodium alginate comprises the following steps: dipping and washing an oxidized sodium alginate raw material in a first solution in a heterogeneous state to obtain an acidified oxidized sodium alginate precipitate, wherein the first solution comprises water, acid and a first organic solvent; dispersing the precipitate in a second solution for neutralization, wherein the second solution comprises water and a second organic solvent; and carrying out dipping dehydration and drying in a heterogeneous state by adopting a third organic solvent to obtain the oxidized sodium alginate. The method is carried out in a heterogeneous system, and the first solution containing low-concentration acid and an organic solvent is used for dipping and washing, so that impurities in the oxidized sodium alginate can be effectively removed, the extraction time is remarkably shortened to about 1 day, and the preparation efficiency is greatly improved; the sterile and high-quality oxidized sodium alginate with low endotoxin content can be obtained, large-scale rapid production can be realized, and the method has a wide application prospect.

Description

Technical Field

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

[0002] Sodium Alginate (SA) is a natural polysaccharide extracted from brown algae. It is mainly composed of β-D-mannuronic acid (M unit) and α-L-guluronic acid (G unit) connected by 1→4 glycosidic bonds. The viscosity of the aqueous solution of sodium alginate is stable at pH 6-9, and it is pH sensitive. 2+ It forms hydrogels in the presence of cations and is used as thickeners, stabilizers, emulsifiers, etc. in the food industry, and as drug carriers, cell carriers, etc. in the biomedicine field.

[0003] Oxidized sodium alginate (OSA) is the product of sodium alginate after oxidation treatment, and its characteristic is that some hydroxyl groups are oxidized to active aldehyde groups. Oxidized sodium alginate has a strong covalent cross-linking effect on proteins due to its dialdehyde structure, so it is widely used in drug release and tissue engineering. At present, there are very few oxidized sodium alginate products sold in the domestic and foreign markets, and the specifications are small (100mg-1g packaging), and the price is expensive. The approximate market price is between 500 yuan per gram and 20,000 yuan per gram. There is no 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 medical treatment, food, environmental protection, etc. At present, there are few biopharmaceutical products based on oxidized sodium alginate on the market. The main reason is that the raw materials of oxidized sodium alginate are difficult to prepare, the yield is low, the cost is high, and it is not conducive to large-scale commercial promotion. A low-cost, large-scale and rapid method for preparing oxidized sodium alginate is very important for its application in the biomedical field, and a feasible solution is urgently needed to prepare high-quality oxidized sodium alginate products with high purity and low endotoxin content. Summary of the invention

[0004] The present invention is based on the inventor's discovery and understanding of the following facts and problems: At present, there are mainly two methods for precipitation extraction after sodium alginate completes oxidation reaction to generate oxidized sodium alginate: (1) The oxidized sodium alginate product is dissolved in water, and dialyzed using a dialysis bag to remove small molecule inorganic salt impurities until iodate impurities can no longer be detected, and then dried using a vacuum freeze dryer to obtain a dry oxidized sodium alginate precipitate, which is then ground and pulverized to obtain oxidized sodium alginate powder. The disadvantage of this method is that the dialysis and freeze-drying operations are cumbersome and time-consuming, and a single production requires at least 7-10 days. In addition, the oxidized sodium alginate is in an aqueous solution environment for a long time, and its molecular chain and active aldehyde group are in an unstable state and are easily damaged, resulting in unstable product quality. Large-scale mass production is not possible, and high-quality oxidized sodium alginate products cannot be produced in multiple batches.

[0005] (2) The oxidized sodium alginate product is completely dissolved in water, and a certain proportion of ethanol is used to precipitate the sodium alginate (usually the ethanol concentration is above 50%), and then the precipitate is separated and the dissolution and precipitation are repeated according to the same operation until the oxidized sodium alginate solution cannot detect iodate impurities, and then the precipitate is ground and crushed to obtain oxidized sodium alginate powder. The disadvantages of this method are that repeated dissolution and precipitation of oxidized sodium alginate will cause serious damage to the oxidized sodium alginate molecular chain and its active aldehyde group, reduce the quality of the product, and also cause a certain amount of product to be lost and unable to 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 the solubility in ethanol above 50% is not high. This method consumes a large amount of anhydrous ethanol or other organic solvents of the same type, and the operation is cumbersome and the cost is high. It is also not suitable for large-scale industrial production.

[0006] Therefore, it is urgent to propose an industrial large-scale production method of oxidized sodium alginate with low cost, simple operation, short time consumption and low threshold, and to strive to improve the quality of the product oxidized sodium alginate, protect the molecular chain length and the number of active aldehyde groups of the oxidized sodium alginate, and ensure the sterility and cleanliness, so as to facilitate its application in the biomedical field.

[0007] The present invention aims to solve at least one of the technical problems in the related art to a certain extent. To this end, the embodiments of the present invention provide 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 immersion 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 obtain high-quality oxidized sodium alginate that is sterile and has a low endotoxin content. It can be produced quickly on a large scale and has broad application prospects.

[0008] The embodiment of the present invention provides a method for extracting oxidized sodium alginate, comprising the following steps: (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 precipitate; the first solution comprises water, an acid, and a first organic solvent; (2) dispersing the acidified oxidized sodium alginate precipitate in a second solution, neutralizing it with an alkali, 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; (3) The neutralized oxidized sodium alginate precipitate is immersed and dehydrated in a third organic solvent in a heterogeneous state; the solution and the precipitate are separated, and the precipitate is dried to obtain oxidized sodium alginate.

[0009] Advantages and technical effects of the extraction method of oxidized sodium alginate of the embodiment 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, and the first solution containing 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 the oxidized sodium alginate powder is obtained by immersion dehydration and drying. The method of the present invention can significantly shorten the extraction time to about 1 day, without the need for dialysis, freeze-drying, repeated dissolution and precipitation steps, is simple and easy, 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 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 achieve a higher sterility 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 biomedical material.

[0010] 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; and / or, the acid comprises at least one of acetic acid, hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid; and / or, the volume percentage of the acid in the first solution is 5%-20%; and / or, the first organic solvent comprises at least one of ethanol, methanol, ether, acetone, dichloromethane, and chloroform; and / or, the volume percentage of the first organic solvent in the first solution is 5%-20%; And / or, the pH of the first solution is 1-5; And / or, the immersion washing time is 1 min-4 h; And / or, multiple step-by-step immersion washing is used in the immersion washing process; the number of step-by-step immersion washing is 5-10 times; and the immersion time of a single immersion washing is 1-20 min.

[0011] In some embodiments, 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 comprises 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.

[0012] In some embodiments, in 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 alkali is an alkali solution; the concentration of the alkali in the alkali solution is 0.1-10M; the alkali solution comprises water and a fourth organic solvent, the fourth organic solvent comprises 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 neutralization time is 2-4 h; And / or, adjusting the pH value to 6.5-7.5.

[0013] In some embodiments, in step (3), the third organic solvent includes at least one of ethanol and acetone; And / or, the immersion and dehydration process includes multiple step-by-step immersion and dehydration; the number of step-by-step immersion and dehydration is 3-10 times; the time of a single immersion and dehydration is 10 min-2 h; And / or, the drying method includes at least one of standing volatilization, filtration volatilization, reduced pressure volatilization, drying or ventilation volatilization.

[0014] In some embodiments, during the multiple step-wise impregnation and dehydration processes, the third organic solvent used in each impregnation and dehydration is the same or different; And / or, using the third organic solvent for immersion dehydration in a heterogeneous state includes: first using anhydrous ethanol for preliminary immersion dehydration, and then using anhydrous acetone for secondary immersion dehydration.

[0015] In some embodiments, in step (1), the oxidized sodium alginate raw material is replaced with an oxidation product of a high molecular weight polysaccharide substance other than the oxidized sodium alginate raw material; 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.

[0016] The embodiment of the present invention provides a method for preparing oxidized sodium alginate, comprising the following steps: 1) subjecting sodium alginate and sodium periodate to a heterogeneous oxidation reaction in an aqueous solution of ethanol, terminating the oxidation reaction, separating the solution and the precipitate, and obtaining an oxidized sodium alginate precipitate; 2) The oxidized sodium alginate precipitate is used as a raw material for oxidized sodium alginate, and is extracted by the method for extracting oxidized sodium alginate described in an embodiment of the present invention to obtain oxidized sodium alginate.

[0017] 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.

[0018] In some embodiments, 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, ethylene glycol is added to terminate the oxidation reaction.

[0019] 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.

[0020] 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.

[0021] The embodiment of the present invention provides an application of oxidized sodium alginate, wherein the oxidized sodium alginate is used in biomedicine, food industry or environmental engineering. In the embodiment of the present invention, the oxidized sodium alginate can achieve a higher sterility level and a low endotoxin content, and as a new biomedical material, it has significant industrial application value and market prospects in the pharmaceutical industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The present invention is a flowchart of the preparation and extraction of oxidized sodium alginate in a laboratory environment according to an embodiment of the present invention.

[0023] Figure 2 This is a flow chart of large-scale preparation and extraction of oxidized sodium alginate in an industrial production environment in another embodiment of the present invention.

[0024] Figure 3 The present invention is a flow chart of preparing and rapidly extracting sterile, low-endotoxin, high-quality oxidized sodium alginate in another embodiment of the present invention.

[0025] Figure 4 1 is an appearance diagram of oxidized sodium alginate powder with different oxidation degrees prepared in the embodiments of the present invention.

[0026] Figure 5 This is an experimental diagram of the dissolution of iodate impurities in ethanol aqueous solutions of different concentrations.

[0027] Figure 6 This is an experimental diagram of the dissolution of iodate impurities in aqueous acetic acid solutions of different concentrations.

[0028] Figure 7 This is a state diagram of oxidized sodium alginate immersed in acetic acid or ethanol aqueous solution with different concentrations.

[0029] Figure 8 This is an experimental diagram of the iodate impurity test in Example 4 of the present invention. DETAILED DESCRIPTION

[0030] Embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0031] like Figure 5 As shown in the figure, the inventors have found that iodate has extremely low solubility in 80-90% organic solvents and is almost insoluble. If more sodium periodate is used, the removal of the reaction impurities may consume a large amount of organic solvent and take a lot of time, which is not economical. At the same time, experimental verification shows that even if the organic solvent is 50%, its solubility in iodate is extremely low. It is necessary to use an organic solvent in the range of 10-30% to have a good dissolution effect on iodate. However, at this concentration, if Figure 7 As shown, the solubility of oxidized sodium alginate is also improved, so the use of low concentration organic solvent for washing will lead to a large loss of oxidized sodium alginate product, which is not conducive to its preparation efficiency.

[0032] As used herein, the term "volume percentage" refers to the volume of a pure liquid divided by the sum of the volumes of the pure liquids of the components of the mixture.

[0033] A method for extracting oxidized sodium alginate according to an embodiment of the present invention comprises the following steps: (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 comprises water, an acid, and a first organic solvent; (2) dispersing the acidified oxidized sodium alginate precipitate in a second solution, neutralizing it with an alkali, 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; (3) The neutralized oxidized sodium alginate precipitate is immersed and dehydrated in a third organic solvent in a heterogeneous state; the solution and the precipitate are separated, and the precipitate is dried to obtain oxidized sodium alginate.

[0034] The extraction method of oxidized sodium alginate in the embodiment of the present invention is extracted and purified in a heterogeneous system, and 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 precipitation is neutralized in the second solution, and the oxidized sodium alginate powder is obtained by immersion dehydration and drying. The method of the present invention does not require dialysis, freeze-drying, repeated dissolution and precipitation, and can significantly shorten the extraction time from the original 7-10 days to about 1 day, greatly improving the preparation efficiency, lowering the production threshold, and improving the quality of the product oxidized sodium alginate. The molecular chain length and the number of active aldehyde groups of the oxidized sodium alginate are protected. 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 achieve a higher sterility 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 biomedical material.

[0035] 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.

[0036] 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.

[0037] In some embodiments, in step (1), the oxidized sodium alginate raw material is powder.

[0038] 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.

[0039] 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; Optionally, the oxidized sodium alginate raw material is a solid product separated after an oxidation reaction of sodium alginate; Optionally, the oxidized sodium alginate raw material includes partially oxidized sodium alginate; 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.

[0040] In some embodiments, in step (1), the acid comprises at least one of acetic acid, hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid, preferably acetic acid.

[0041] In the embodiment 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, which may cause severe damage to the molecular weight of oxidized sodium alginate, affecting the quality of the final product. When using, the concentration must be carefully selected, and the temperature and washing time must be strictly controlled; acetic acid is the best choice. Acetic acid is a weak acid, and the acidic environment provided 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 oxidized sodium alginate molecular chain from being excessively damaged. The overall environment is mild, which is conducive to the preparation of high-quality oxidized sodium alginate.

[0042] In some embodiments, in 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, 2-4. In the embodiment 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, improving the impurity removal effect, and achieving a higher cleanliness level.

[0043] In some embodiments, in 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%.

[0044] In an embodiment 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 requires multiple uses of organic solvents, ethanol can be selected as the oxidized sodium alginate dissolution inhibitor in the first solution in the washing step in order to reduce the complexity of the system, that is, ethanol is selected as the first organic solvent, which can effectively protect the oxidized sodium alginate and is conducive to the preparation of high-quality oxidized sodium alginate.

[0045] 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.

[0046] 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; 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.

[0047] 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.

[0048] In the embodiment 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 washing, but the stronger the solution acidity, the easier it is to destroy the molecular chain of oxidized sodium alginate, reduce the molecular weight, and reduce 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 washing, but at the same time, the solubility of inorganic salt impurities is also lower, and the efficiency of washing to remove inorganic salts becomes lower, and the amount of washing solution needs to be increased, and the number of washings is increased at the same time; 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 the rapid removal of impurities, but reduces the yield of oxidized sodium alginate, especially low molecular weight partially oxidized sodium alginate dissolves more and loses more.

[0049] In the embodiment of the present invention, the aqueous solution of acetic acid-ethanol is used as the washing reagent for the precipitate, and the 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 use the aqueous solution of acetic acid and the aqueous solution of ethanol separately for step-by-step washing, and the purpose of washing the precipitate cannot be achieved.

[0050] In some embodiments, in step (1), the immersion washing time 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; 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.

[0051] In the embodiment of the present invention, the time of immersion washing in the first solution needs to be controlled, and the time of immersion washing or the total duration of the washing process is controlled within 1 min-4 h. Under a low pH environment, the molecular chains of the oxidized sodium alginate will slowly break to a certain extent, and long-term immersion will lead to a decrease in product quality.

[0052] In some embodiments, multiple step-by-step immersion washing is used in the immersion washing process; the number of step-by-step immersion washing is 5-10 times, specifically, for example, 5 times, 6 times, 7 times, 8 times, 9 times, 10 times; the immersion time of a single immersion washing is 1-20 min, specifically, for example, 1 min, 2 min, 3 min, 4 min, 5 min, 10 min, 20 min; in a single immersion washing process, the first solution is used to disperse the oxidized sodium alginate raw material or precipitate in an amount of 5-10 times the volume of the oxidized sodium alginate raw material or precipitate for immersion 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 immersion washing, a centrifugation or filtration step is combined to separate the solution and the precipitate.

[0053] In the embodiment of the present invention, the washing process should be carried out by step washing rather than one-time large volume solution washing. The step-by-step multiple washing is conducive to reducing the content of inorganic salt impurities by exponential multiples, thereby achieving the purpose of cost saving. The amount of the first solution used in the washing process can be adjusted according to the amount of impurities in the oxidized sodium alginate raw material or the amount of sodium periodate added in the process of preparing oxidized sodium alginate by the oxidation reaction of sodium alginate during the preparation of oxidized sodium alginate.

[0054] In some embodiments, in step (1), the solution and the precipitate are separated by centrifugation; optionally, the centrifugal speed is 800-1000 rpm, and the centrifugal time is 3-5 minutes; And / or, separating the solution and the precipitate by suction filtration; optionally, using a non-oil pump vacuum machine for suction filtration.

[0055] In some embodiments, in step (1), the oxidized sodium alginate raw material is immersed and washed in the first solution in a heterogeneous state until iodate cannot be detected in the washing solution; optionally, a silver nitrate detection method is used. In the embodiment of the present invention, the oxidized sodium alginate raw material contains impurities such as iodate, and the immersion and washing process is terminated by detecting iodate.

[0056] In some embodiments, before step (2), the acidified oxidized sodium alginate precipitate is washed with an ethanol-water solution until no residual acid can be detected in the washing solution; optionally, the ethanol-water solution is an ethanol-water solution with a volume percentage of 80-95%, specifically, for example, 80%, 85%, 90%, 95%; the precipitate and the washing solution are separated by centrifugation or filtration; and the washing operation is repeated multiple times.

[0057] In some embodiments, in step (2), the acidified oxidized sodium alginate precipitate is dispersed in a second solution, 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 embodiment 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.

[0058] In some embodiments, in step (2), alkali is used for neutralization; optionally, the alkali includes at least one of sodium hydroxide, sodium carbonate, and sodium bicarbonate; the alkali is an alkali solution; the concentration of the alkali in the alkali solution is 0.1-10M, specifically, for example, 0.1M, 1M, 3M, 5M, 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%, specifically, for example, 30%, 40%, 50%, 60%, 70%, 80%.

[0059] In the embodiment of the present invention, a fourth organic solvent (e.g., ethanol)-water mixed solution of an alkali is used for neutralization, wherein the concentration of the fourth organic solvent can be selected to be 30%-80%, because the titration amount of the alkali solution is small and does not affect the overall environment of the solution. In industrial production, if the neutralization process needs to be accelerated, the concentration of sodium hydroxide can be increased to 10M, and can be 0.1-1M in a laboratory environment.

[0060] In some embodiments, in step (2), the neutralization time is 2-4 h, specifically, for example, 2 h, 3 h, 4 h.

[0061] In the embodiment of the present invention, the neutralization process of oxidized sodium alginate is relatively slow. The lower the degree of oxidation, the slower the neutralization speed of oxidized sodium alginate, and the higher the degree of oxidation, the faster the neutralization speed of oxidized sodium alginate. Since the molecular chain of oxidized sodium alginate is easily broken in an alkaline environment, the neutralization time of the alkaline solution needs to be controlled; the total duration of the neutralization process is controlled within 2-4 hours to ensure the quality of the oxidized sodium alginate product.

[0062] 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 embodiment 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 use of subsequent products. At the same time, excessive alkali will increase the solubility of oxidized sodium alginate and also destroy the structure of the molecule.

[0063] In some embodiments, in step (2), the neutralization is performed by titration neutralization, and optionally, the acidified oxidized sodium alginate precipitate is slowly titrated and neutralized.

[0064] In some embodiments, in step (2), the acidified oxidized sodium alginate precipitate is immersed and neutralized using a second solution.

[0065] In some embodiments, in step (2), the acidified oxidized sodium alginate precipitate is dispersed in a second solution, and an alkaline solution is added dropwise during stirring to perform titration neutralization; optionally, the second solution is a 90% ethanol aqueous solution; and the alkaline solution is a 50% ethanol-water mixed solution of 1M sodium hydroxide.

[0066] In some embodiments, in the step (2), stirring is performed during the neutralization process, and optionally, the stirring speed is 600-1000 rpm. In the embodiment of the present invention, stirring is conducive to the rapid dispersion of the alkaline solution added dropwise, so that the overall pH change of the system is relatively gentle, and the reaction is mild, and the oxidized alginate acidified during the pickling process is converted back into oxidized sodium alginate.

[0067] In some embodiments, in step (2), the endpoint of the neutralization process can be determined using a pH meter or an acid-base indicator; The second solution includes a second organic solvent, and the pH value cannot be monitored using an ordinary pH meter. Instead, a pH meter equipped with a probe suitable for organic solvents is required for monitoring, wherein the specific value of the neutral pH depends on the pH probe used; 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), and thymol blue (8.0-9.6); a combination of different indicators can also be used to enhance the significant phenomenon of the neutralization endpoint.

[0068] In the embodiment of the present invention, low concentration of bromothymol blue is considered to be non-biotoxic. When the pH value is neutral, the solution is green. According to experience, the color development range of bromothymol blue in aqueous solution and ethanol solution is similar. When it shows green, the final oxidized sodium alginate product aqueous solution is between 6.5-7.5. When the solution is light green and the green does not fade for 0.5-1 hour, it is the neutralization end point, and the neutralization process of oxidized sodium alginate is completed. The amount of bromothymol blue solution (the storage solution is 100 mg / mL of anhydrous ethanol solution, and the working solution is 1 mg / mL of 90% ethanol solution) added is 200 μL of working solution per 50 mL of total volume (final concentration is 4 μg / mL), and obvious color changes can be observed. Experiments show that bromothymol blue does not effectively bind to oxidized sodium alginate molecules. Due to the ultra-high solubility of bromothymol blue in organic solvents (such as ethanol), bromothymol blue can be completely removed without any residue in the subsequent washing process of organic solvents such as ethanol, and can be used as an effective neutralization endpoint indicator for the reaction system.

[0069] In some embodiments, before step (3), the neutralized oxidized sodium alginate precipitate is first washed with an aqueous solution of ethanol, and then step (3) is performed to immerse and dehydrate the precipitate in a heterogeneous state with a third organic solvent; Optionally, the ethanol aqueous solution is an ethanol aqueous solution with a volume percentage of 80-95%, specifically, for example, 80%, 85%, 90%, 95%; Optionally, the washing is performed by immersion washing; Optionally, the washing with an aqueous solution of ethanol includes washing the precipitate 3-5 times with an aqueous solution of ethanol having a volume percentage of 80-95% by volume, to fully remove impurities such as acid-base indicators and alkalis that may be generated or remain during the neutralization process; Optionally, the precipitate and the washing solution are separated by centrifugation or filtration; Optionally, the washing operation is repeated multiple times until no residual sodium hydroxide can be detected in the washing solution.

[0070] In some embodiments, in step (3), the third organic solvent includes at least one of ethanol and acetone; the immersion dehydration process includes multiple step-by-step immersion dehydration; the number of step-by-step immersion dehydration is 3-10 times, specifically, for example, 3 times, 4 times, 5 times, 6 times, 7 times, 8 times, 9 times, 10 times; the time of a single immersion dehydration is 10 min-2 h, specifically, for example, 10 min, 15 min, 20 min, 25 min, 30 min, 1 h, 1.5 h, 2 h; in the multiple step-by-step immersion dehydration processes, the third organic solvent used in each immersion dehydration is the same or different.

[0071] In the embodiment 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 process 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. In the extraction process, acetone can prevent the oxidation of polysaccharides, which is very important for maintaining the biological activity and stability of the sample. The volatility of acetone makes it easy to remove it during the drying process, thereby not leaving residues in the sample. Even if acetone has any residues that cannot be monitored during the treatment process, it can be completely dissolved in the aqueous solution during the use of oxidized sodium alginate, and its trace residues will not affect any characteristics or functions of oxidized sodium alginate.

[0072] In some embodiments, the neutralized oxidized sodium alginate precipitate is immersed and dehydrated with a third organic solvent in a heterogeneous state, comprising: firstly immersing and dehydrating with anhydrous ethanol, and then immersing and dehydrating with anhydrous acetone for a second time; Optionally, firstly use anhydrous ethanol 3-5 times the volume of the precipitate to disperse and wash the precipitate 3-5 times, immersing the precipitate for 10-30 minutes each time, so as to perform preliminary immersion dehydration treatment on the precipitate; Optionally, anhydrous acetone 3-5 times the volume of the precipitate is used to disperse and wash the precipitate 3-5 times, and the precipitate is immersed in it for 10-30 minutes each time, so as to dealcoholize and dehydrate the precipitate, that is, secondary immersion dehydration.

[0073] In some embodiments, in step (3), the solution and the precipitate are separated by centrifugation or filtration.

[0074] In some embodiments, in step (3), the drying method includes at least one of standing volatilization, filtration volatilization, reduced pressure volatilization, drying or ventilation volatilization; optionally, the filtration volatilization adopts reduced pressure filtration; optionally, there is no special restriction 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 that the organic solvent is completely removed. In the embodiment of the present invention, drying completely volatilizes the small amount of the third organic solvent remaining, completely removes the product water or organic solvent, and obtains high-purity and high-quality oxidized sodium alginate powder.

[0075] In some embodiments, in step (3), after drying, grinding can be performed to make the oxidized sodium alginate more delicate, which is conducive to rapid dissolution during the application process. In the embodiment of the present invention, since the entire process of the method of the present invention is carried out in a heterogeneous system, the oxidized sodium alginate retains the powder state of the original raw material to a large extent, and the form is relatively fine particles.

[0076] In some embodiments, each step can be performed under sterile conditions, using sterile grade reagents, and ultimately a sterile oxidized sodium alginate product can be produced.

[0077] In some embodiments, no bacterial or fungal flora expansion is observed under conventional culture conditions for oxidized sodium alginate for 2-7 days; and the endotoxin content is less than 0.5 EU / mL.

[0078] In some embodiments, the extraction method of oxidized sodium alginate does not require dialysis and / or freeze-drying.

[0079] In some embodiments, the oxidized sodium alginate raw material is replaced with an oxidation product of a high molecular weight polysaccharide substance other than the oxidized sodium alginate raw material; 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, starch substances and their derivatives; the oxidation product of the high molecular weight polysaccharide substance is prepared by an oxidation reaction of the high molecular weight polysaccharide substance; the oxidation reaction is a heterogeneous oxidation reaction; optionally, a sodium periodate heterogeneous oxidation reaction; the oxidation product of the high molecular weight polysaccharide substance includes impurities generated during the sodium periodate heterogeneous oxidation reaction, for example, unreacted sodium periodate and iodate derivatives after the sodium periodate oxidation reaction.

[0080] In the embodiment of the present invention, the rapid extraction method is mainly based on the solubility characteristics of sodium alginate / oxidized sodium alginate, that is, it is almost insoluble in all organic solvents and has extremely low solubility under acidic conditions; based on the solubility 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 combined with acidic conditions and organic solvent conditions can effectively achieve rapid washing and drying of the oxidized sodium alginate precipitate after the oxidation reaction; the method is suitable for the preparation of oxidation products of high molecular weight polysaccharide substances that also have the characteristics of (1) being insoluble in some common organic solvents (such as ethanol, acetone, dichloromethane, etc.), and (2) being insoluble 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; the specific organic solvent and acid can be further selected according to the characteristics of the specific high molecular weight raw material.

[0081] A method for preparing oxidized sodium alginate according to an embodiment of the present invention comprises the following steps: 1) subjecting sodium alginate and sodium periodate to a heterogeneous oxidation reaction in an aqueous solution of ethanol, terminating the oxidation reaction, separating the solution and the precipitate, and obtaining an oxidized sodium alginate precipitate; 2) The oxidized sodium alginate precipitate is used as a raw material for oxidized sodium alginate, and is extracted by the method for extracting oxidized sodium alginate described in an embodiment of the present invention to obtain oxidized sodium alginate.

[0082] 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.

[0083] 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.

[0084] In some embodiments, in step 1), the sodium alginate is sodium alginate powder.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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%.

[0089] 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.

[0090] In a specific embodiment, after testing and determination, the corresponding scheme of the amount of sodium periodate added and the final oxidation degree of oxidized sodium alginate is shown in Table 1. The oxidation degree refers to the percentage of the number of monomers with o-dialdehyde in the total number of sodium alginate monomers after the oxidation reaction, and the calculation formula is OD=(nCHO / 2) / (w sodium alginate / 198.11), where 198.11 is the approximate value of the molecular weight of the sodium alginate monomer.

[0091] Table 1

[0092] In Table 1, 5 g of sodium alginate is dispersed in 25 mL of anhydrous ethanol to obtain a sodium alginate suspension; sodium periodate is dissolved in 25 mL of water to obtain a sodium periodate solution; the sodium periodate solution is slowly added to the sodium alginate suspension under stirring at 600 rpm, and the reaction is carried out at 20 ° C in the dark for 6 hours; 5 mL of ethylene glycol is added to react for 30 minutes to completely consume sodium periodate and terminate the reaction; washing, neutralization and drying are performed using the steps of the extraction method described in the embodiment of the present invention. The degree of oxidation is determined by detecting the aldehyde content of the oxidized sodium alginate, and is mainly quantitatively calculated by the hydroxylamine hydrochloride method. The amount of HCl produced in the reaction is determined by the neutralization titration method, thereby inferring the content of aldehyde groups in the oxidized sodium alginate.

[0093] In some embodiments, in step 1), sodium alginate and sodium periodate are subjected to a heterogeneous oxidation reaction in an aqueous solution of ethanol; Optionally, first disperse sodium alginate in anhydrous ethanol to obtain a sodium alginate suspension; dissolve sodium periodate in water to obtain a sodium periodate solution; add the sodium periodate solution to the sodium alginate suspension under stirring; optionally, add dropwise slowly; optionally, the stirring speed is 600-800rpm; optionally, add the sodium periodate solution to the sodium alginate suspension to obtain an ethanol aqueous solution system with a final concentration of 50%.

[0094] In some embodiments, in step 1), in the heterogeneous oxidation reaction system, the ratio between the 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 an aqueous solution of ethanol, specifically, for example, the total volume of a 50% aqueous solution of ethanol.

[0095] In some embodiments, in step 1), the heterogeneous oxidation reaction is carried out under stirring; optionally, the stirring speed is 600-800 rpm, so that an oxidized sodium alginate precipitate with uniform oxidation reaction can be obtained.

[0096] In some embodiments, in step 1), ethylene glycol is added to terminate the oxidation reaction; optionally, the amount of ethylene glycol added is 1 / 10-1 / 3 of the total volume of the heterogeneous oxidation reaction system or the total volume of the ethanol aqueous solution; the time for terminating the reaction with ethylene glycol is 20-40 min, optionally, 30 min; the temperature of the system for terminating the reaction is maintained at room temperature or 20°C; a stirring device is used during the termination of the reaction, and the stirring speed is 600-800rpm. In the embodiment of the present invention, an excess of ethylene glycol is used to terminate the reaction, and the unreacted sodium periodate in the system is completely consumed.

[0097] In some embodiments, before step 2), the oxidized sodium alginate precipitate is washed with an ethanol-water solution; optionally, an ethanol-water solution with a volume percentage of 80-95%, specifically, for example, 80%, 85%, 90%, 95%; optionally, immersion washing; optionally, repeated multiple times.

[0098] 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; In an industrial production environment, the precipitate and the solution are separated by vacuum filtration or pressure filtration; alternatively, quantitative filter paper or an organic solvent-resistant filter membrane with a pore size of 0.22-20 μm is used for filtration.

[0099] In some embodiments, each step can be performed under sterile conditions, using sterile grade reagents, and ultimately a sterile oxidized sodium alginate product can be produced.

[0100] In some embodiments, the sodium alginate raw material is immersed in a 75% ethanol aqueous solution for 6-24 hours, and it can be detected that the sodium alginate solution is completely sterile, and no bacteria grow when placed at 37° C. for 3-7 days.

[0101] In some embodiments, if there is a requirement for the endotoxin level of oxidized sodium alginate, sodium alginate with a low endotoxin content can be used as a production raw material, or an endotoxin removal step can be added during the production process; Optionally, endotoxins can be effectively removed by immersing and washing the seaweed raw material or sodium alginate raw material with Triton X-114; Endotoxins can be effectively removed by soaking seaweed or sodium alginate raw materials for more than 4 hours or heating and boiling for more than 2 hours using 0.1M sodium hydroxide aqueous solution or 0.1M sodium hydroxide 75% ethanol solution. Endotoxins can be effectively removed by soaking seaweed raw materials or sodium alginate raw materials in 0.1M dilute hydrochloric acid for more than 4 hours or boiling them in acid for more than 2 hours.

[0102] In the embodiment of the present invention, due to the good stability of sodium alginate, the endotoxin removal step will not strongly destroy the structure of sodium alginate itself. If strong acid and alkali are used, attention should be paid to the treatment time, and the sodium alginate should be adjusted to neutrality at the end to facilitate the subsequent oxidation and extraction process. Similarly, in the subsequent treatment process, the strong oxidation reaction of sodium periodate and the washing process of acidic organic solvent are conducive to further sterilization and reduction of endotoxin levels. It has been verified experimentally that after the raw material is treated with endotoxin removal, the endotoxin content of the prepared oxidized sodium alginate product is low and controlled at a level of less than 0.5EU / mg; after strict endotoxin removal treatment, it can be controlled at a level of less than 0.03EU / mg.

[0103] In some embodiments, the organic solvents used, such as acetic acid, ethanol, acetone, etc., can be purified and recovered by distillation and fractionation. The operation is simple and can be reused in principle.

[0104] In some embodiments, the sodium periodate reaction derivatives produced in the process, such as sodium iodate, can be precipitated and extracted, collected as by-products of the reaction, and in principle can be recycled.

[0105] 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.

[0106] An oxidized sodium alginate according to an embodiment of the present invention is obtained by the method described in the embodiment of the present invention. According to the embodiment of 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.

[0107] In the embodiments of the present invention, low-cost high-purity oxidized sodium alginate and sterile, low-endotoxin high-quality oxidized sodium alginate are provided. Based on the raw materials, facilities, and manpower and time costs used, the following estimates are made: (1) small batches of high-purity oxidized sodium alginate are about 30-50 yuan / g; (2) small batches of sterile, low-endotoxin oxidized sodium alginate are about 150-300 yuan / g; (3) large batches of high-purity oxidized sodium alginate are about 4 yuan / g or 3500-4000 yuan / kg; (4) large batches of sterile, low-endotoxin oxidized sodium alginate are 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 and promotion of the use of oxidized sodium alginate.

[0108] In some embodiments, since the product oxidized sodium alginate powder is sensitive to heat, it should be stored in a dark environment at 4°C for short-term storage and in a dark environment at -20°C for long-term storage, away from strong acids, strong bases, strong oxidants, etc.

[0109] An application of oxidized sodium alginate in an embodiment of the present invention is used in biomedicine, food industry or environmental engineering. In the embodiment of the present invention, oxidized sodium alginate can achieve a higher sterility level and a low endotoxin content, and as a new biomedical material, it has significant industrial application value and market prospects in the pharmaceutical industry.

[0110] In some embodiments, the oxidized sodium alginate is used in biomedical materials.

[0111] In some embodiments, the oxidized sodium alginate is used for at least one of a degradable gel material, a drug controlled release material, a cell culture carrier, a tissue engineering scaffold, and a medical biological excipient. In the embodiments of the present invention, the preparation method of the oxidized sodium alginate 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 prepared high-sterility, high-cleanliness, high-quality oxidized sodium alginate can be used for a variety of applications such as a degradable gel material, a drug controlled release material, a cell culture carrier, a tissue engineering scaffold, and the like.

[0112] The present invention is described below with reference to specific embodiments. It should be noted that these embodiments are merely illustrative and do not limit the present invention in any way.

[0113] Example 1: Preparation and rapid extraction of oxidized sodium alginate in laboratory environment This embodiment adopts Figure 1 The process shown is for preparing and rapidly extracting oxidized sodium alginate in a laboratory environment, specifically, comprising the following steps: (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 anhydrous ethanol to obtain a sodium alginate suspension; take 0.6416 g, 1.604 g, and 2.887 g of sodium periodate (used to prepare oxidized sodium alginate with oxidation degrees of 20%, 50%, and 90%, respectively), dissolve them in 15 mL of pure water to obtain a sodium periodate solution; first add the sodium alginate suspension into a 50 mL beaker, and slowly add the sodium periodate solution to the sodium alginate suspension under stirring at 600 rpm, and react at 20°C in the dark for 6 hours; add 3 mL of ethylene glycol and react for 30 min to completely consume the sodium periodate and terminate the oxidation reaction; centrifuge the reaction product at 1000 rpm for 3 min, discard the supernatant, and obtain an oxidized sodium alginate precipitate; (2) Add 40 mL of 90% ethanol aqueous solution, use a vortex mixer to disperse the precipitate and wash; centrifuge at 1000 rpm for 3 min, discard the supernatant; repeat the ethanol aqueous solution washing for a total of 3 times; (3) Add 40 mL of 10% ethanol-10% acetic acid aqueous solution, use a vortex mixer to oscillate and disperse the precipitate, and immerse and wash for 5-10 minutes each time to dissolve iodate impurities; centrifuge at 1000 rpm for 5 minutes and discard the supernatant; repeat the acetic acid-ethanol aqueous solution washing for a total of about 5 times until iodate impurities can no longer be detected in the supernatant (silver nitrate detection method); (4) Add 40 mL of 90% ethanol aqueous solution, use a vortex mixer to disperse the precipitate, wash; centrifuge at 1000 rpm for 5 min, discard the supernatant; repeat the ethanol aqueous solution washing for a total of 5 times, at which point the supernatant acetic acid content is less than 10 -6 %; (5) Resuspend the precipitate in 40 mL of 90% ethanol solution and transfer it to a 50 mL beaker for sodium hydroxide neutralization reaction; add 200 μL of bromothymol blue (Bickman Bio, final concentration of 4 μg / mL) solution as an acid-base indicator while stirring at 800 rpm, slowly add 1 M sodium hydroxide in 50% ethanol aqueous solution, and adjust the pH value of the oxidized sodium alginate powder to neutral in the heterogeneous system until the solution turns light green and does not change color within 30 minutes. The neutralization time is about 3 hours. Use fine quantitative filter paper to filter the reaction product to separate the precipitate; after each filtration, add 40 mL of 90% ethanol aqueous solution to disperse the precipitate and filter again; repeat the filtration operation 5 times, at which time no sodium hydroxide can be detected in the filtrate; (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; (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).

[0114] 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.

[0115] 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.

[0116] 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.

[0117] Example 2: Verification of the feasibility of large-scale preparation and extraction of oxidized sodium alginate under industrial production environment 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: (1) Take 20g of sodium alginate powder from brown algae as a reaction raw material, disperse it in 100mL of anhydrous ethanol to obtain a sodium alginate suspension; take 10.693g of sodium periodate (for preparing oxidized sodium alginate with an oxidation degree of 50%), dissolve it in 100mL of pure water to obtain a sodium periodate solution; use a 250mL beaker as an oxidation reaction container, first add the sodium alginate suspension, and slowly add the sodium periodate solution to the sodium alginate suspension under stirring at 800rpm, and react at 20°C in the dark for 6 hours; add 20mL of ethylene glycol to react for 30min to completely consume the sodium periodate and terminate the oxidation reaction; transfer the reaction product to a suction filtration device (a sand core suction filtration device with a capacity of 300mL), use a rapid qualitative filter paper to perform suction filtration to separate the precipitate, and obtain an oxidized sodium alginate precipitate; (2) Add 200 mL of 90% ethanol aqueous solution, use a glass stirring rod to stir and disperse the precipitate, and wash; remove the washing solution by vacuum filtration; repeat the ethanol aqueous solution washing for a total of 3 times; (3) Add 200 mL of 10% ethanol-10% acetic acid aqueous solution, use a glass stirring rod to stir and disperse the precipitate, and immerse and wash for 5-10 minutes each time to dissolve the iodate impurities; remove the washing solution by vacuum filtration; repeat the acetic acid-ethanol aqueous solution washing for a total of about 5 times until the iodate impurities can no longer be detected in the supernatant; (4) Add 200 mL of 90% ethanol aqueous solution, use a glass stirring rod to stir and disperse the precipitate, and wash; remove the washing solution by vacuum filtration; repeat the ethanol aqueous solution washing for a total of 5 times; (5) Resuspend the precipitate in 200mL of 90% ethanol solution and transfer it to a 250mL beaker for sodium hydroxide neutralization reaction; add 1mL of bromothymol blue solution as an acid-base indicator while stirring at 1000rpm, slowly add 1M sodium hydroxide in 50% ethanol aqueous solution, and adjust the pH value of the oxidized sodium alginate powder to neutral in the heterogeneous system until the solution turns light green and does not change color within 30min. The neutralization time is about 3 hours. Transfer the reaction product to a filtration device and use fine quantitative filter paper to filter and separate the precipitate; after each filtration, add 200mL of 90% ethanol aqueous solution to disperse the precipitate and filter again; repeat the filtration operation 5 times, at which time no sodium hydroxide can be detected in the filtrate; (6) Transfer the precipitate to a 250 mL flask, add 200 mL of anhydrous ethanol and immerse for 2 hours to dehydrate. Repeat this operation three times; perform vacuum filtration to remove the liquid component; (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.

[0118] 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.

[0119] 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.

[0120] 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.

[0121] 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.

[0122] Example 3: Verification of the feasibility of sterile, low-endotoxin, high-quality oxidized sodium alginate preparation and rapid extraction 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: 3 g of sodium alginate powder (Sigma-Aldrich, 71238) from brown algae was used as the reaction raw material and endotoxin was removed by two methods: (1) Soak in 0.1 M dilute hydrochloric acid solution for 6 h (stirring at 600 rpm); (2) Use a 1% Triton X-114 aqueous solution, soak in an ice bath for 30 minutes (stirring at 600 rpm), heat to 37°C, and when obvious stratification appears in the solution, centrifuge at 12,000 rpm at room temperature for 5 minutes, remove the supernatant, and repeat twice; then wash five times with endotoxin-free water.

[0123] After the endotoxin removal treatment, sterilize by soaking in 75% ethanol for 6 hours (using a rotary mixer to continuously mix). The raw material sodium alginate can be treated to remove endotoxin and sterilize.

[0124] The endotoxin level of 2.5% sodium alginate solution was less than 0.5EU / mL using Xiamen Bioande microgel method horseshoe crab reagent (sensitivity 0.5EU / mL). A 2.5% sodium alginate solution containing 5% glucose was prepared and incubated at 37°C for 48 hours. No obvious bacterial or fungal flora was observed under the microscope.

[0125] In a heterogeneous solution, the pH value of the sodium alginate raw material is adjusted to neutral, and oxidized sodium alginate with 20%, 50%, and 90% oxidation degrees is prepared using the same operating steps according to the method in Example 1. The solution used throughout the process is filtered through a 0.22 μm sterile filter to ensure that no new sources of bacteria / fungi are introduced. After the preparation and rapid extraction of oxidized sodium alginate are completed, the endotoxin level and sterility of the oxidized sodium alginate product are monitored. The endotoxin level of the oxidized sodium alginate solution with a concentration of 10% was measured to be <0.5EU / mL. A 10% sodium alginate solution with 5% glucose was prepared and incubated at 37°C for 72 hours. No obvious bacterial or fungal flora was observed under a microscope. The effective control of endotoxin levels and the sterility of the prepared product can be demonstrated.

[0126] In an industrial production environment, endotoxin levels and fungi levels should be controlled starting from the raw materials. For example, in the process of extracting sodium alginate from brown algae, it is carried out in a sterile environment, and acidification, alkalization and other operations are performed to effectively reduce endotoxin levels and sterilize. In this way, the industrial production process is optimized to prepare high-quality oxidized sodium alginate products with high cleanliness (low endotoxin content, high sterility), making them suitable for biomedical applications.

[0127] This embodiment is only a typical example of the feasibility of verifying the preparation and rapid extraction of sterile, low-endotoxin, high-quality oxidized sodium alginate in a laboratory environment using low-cost raw material sources, simple consumables and experimental equipment. It does not represent the average and highest level of the final preparation effect of low-endotoxin, sterile, high-quality oxidized sodium alginate using this technical solution. After optimization and verification, better preparation results can be achieved.

[0128] Example 4: Verification of the feasibility of washing oxidized sodium alginate using the method of the present invention This embodiment adopts Figure 1 The process shown in the figure is used to prepare and quickly extract oxidized sodium alginate in a laboratory environment, and the effectiveness and reliability of the method are verified by relevant characterization.

[0129] According to the method in Example 1, oxidized sodium alginate with oxidation degrees of 20%, 50%, and 90% was prepared using the same operation steps. Figure 4 As shown, the prepared oxidized sodium alginate product is in the form of a fine powder. The low oxidation degree is slightly yellowish, and the higher the oxidation degree, the whiter the powder color.

[0130] Sodium periodate and its iodate derivatives (impurities) obtained by the reaction of sodium periodate and ethylene glycol are used to test the solubility of iodate impurities in aqueous solutions of organic solvents of different types and mass percentages (especially aqueous acetic acid and aqueous ethanol).

[0131] Figure 5 This is an experimental diagram of the dissolution of iodate derivatives (impurities) after the oxidation reaction of sodium periodate in ethanol aqueous solutions of different concentrations. Figure 5 It can be clearly seen that at higher concentrations of ethanol aqueous solution (50%, 75%, 100%), the solubility of iodate impurities is extremely low, making it difficult to effectively remove iodate impurities. Lower concentrations of ethanol aqueous solution (25%) can dissolve iodate impurities, but at the same time, the solubility of sodium alginate / oxidized sodium alginate is also high.

[0132] Figure 6 This is an experimental diagram of the dissolution of iodate derivatives (impurities) after the oxidation reaction of sodium periodate in aqueous acetic acid solutions of different concentrations. Figure 6 It can be clearly seen that under different concentrations of acetic acid solution (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, acidic conditions are conducive to minimizing the solubility of sodium alginate / oxidized sodium alginate.

[0133] Figure 7 This is a state diagram of the oxidation of sodium alginate when immersed in acetic acid or ethanol at different concentrations. Figure 7It can be found that the morphology of oxidized sodium alginate with a 50% oxidation degree will not change significantly when soaked in acetic acid and ethanol solutions of different concentrations. Oxidized sodium alginate soaked in acetic acid is partially acidified to oxidized alginic acid, which may present a certain degree of transparent colloidal precipitate under low concentration aqueous solution, and can be restored to an opaque powdery precipitate after neutralization with sodium hydroxide.

[0134] Figure 8 It is an experimental diagram of the iodate impurity test in Example 4 of the present invention. Silver nitrate is added dropwise to a sodium periodate solution, a solution of an iodate derivative impurity which is a reaction product of sodium periodate and ethylene glycol, an unwashed oxidized sodium alginate solution, and a washed oxidized sodium alginate solution, and the washed product is monitored by the precipitation reaction of silver nitrate to see whether the washed product contains sodium periodate or iodate impurity residues.

[0135] like Figure 8 As shown, the 50% oxidation degree oxidized sodium alginate aqueous solution obtained in step (1) with a mass percentage concentration of 10% without washing is titrated with a silver nitrate solution, and an obvious white precipitate appears (indicating that the solution contains iodate impurities), indicating that iodate impurities exist in the unwashed oxidized sodium alginate.

[0136] The oxidized sodium alginate aqueous solution (after washing) with a mass percentage concentration of 10% prepared and extracted in step (7) and with a degree of oxidation of 50% was titrated with a silver nitrate solution, and no obvious black precipitate (indicating that the solution contained sodium periodate) or white precipitate (indicating that the solution contained iodate impurities) appeared, which can prove that the iodate impurities were effectively removed.

[0137] This example is only a typical example of verifying the rationality and feasibility of the technical solution used in the invention in a laboratory environment using low-cost raw materials, simple consumables and experimental equipment. It does not represent the average or highest level of high-quality oxidized sodium alginate preparation and rapid extraction using this technical solution. After optimization and verification, better preparation results can be achieved.

[0138] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction 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 described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0139] Although the above embodiments have been shown and described, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. Changes, modifications, substitutions and variations of the above embodiments by those of ordinary skill in the art are all within the scope of protection of the present invention.

Claims

1. A method for extracting oxidized sodium alginate, characterized in that: The following steps are involved: (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 precipitate; the first solution comprises water, an acid, and a first organic solvent; (2) dispersing the acidified oxidized sodium alginate precipitate in a second solution, neutralizing it with an alkali, 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; (3) The neutralized oxidized sodium alginate precipitate is immersed and dehydrated in a third organic solvent in a heterogeneous state; the solution and the precipitate are separated, and the precipitate is dried to obtain oxidized sodium alginate.

2. The method for extracting oxidized sodium alginate according to claim 1, characterized in that: In the step (1), the oxidized sodium alginate raw material is an oxidized sodium alginate product prepared by an oxidation reaction of sodium alginate; and / or, the acid comprises at least one of acetic acid, hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid; and / or, the volume percentage of the acid in the first solution is 5%-20%; and / or, the first organic solvent comprises at least one of ethanol, methanol, ether, acetone, dichloromethane, and chloroform; and / or, the volume percentage of the first organic solvent in the first solution is 5%-20%; And / or, the pH of the first solution is 1-5; And / or, the immersion washing time is 1 min-4 h; And / or, multiple step-by-step immersion washing is used in the immersion washing process; the number of step-by-step immersion washing is 5-10 times; and the immersion time of a single immersion washing is 1-20 min.

3. The method for extracting oxidized sodium alginate according to claim 2, characterized in that: 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 comprises 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 method for extracting 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 alkali is an alkali solution; the concentration of the alkali in the alkali solution is 0.1-10M; the alkali solution comprises water and a fourth organic solvent, the fourth organic solvent comprises 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 neutralization time is 2-4 h; And / or, adjusting the pH value to 6.5-7.

5.

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

6. The method for extracting oxidized sodium alginate according to claim 5, characterized in that: During the multiple step-wise impregnation and dehydration processes, the third organic solvent used in each impregnation and dehydration is the same or different; And / or, using the third organic solvent for immersion dehydration in a heterogeneous state includes: first using anhydrous ethanol for preliminary immersion dehydration, and then using anhydrous acetone for secondary immersion dehydration.

7. The method for extracting oxidized sodium alginate according to claim 1, characterized in that: In the step (1), the oxidized sodium alginate raw material is replaced by an oxidation product of a high molecular weight polysaccharide substance other than the oxidized sodium alginate raw material; 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.

8. A method for preparing oxidized sodium alginate, characterized in that: The following steps are involved: 1) subjecting sodium alginate and sodium periodate to a heterogeneous oxidation reaction in an aqueous solution of ethanol, terminating the oxidation reaction, separating the solution and the precipitate, and obtaining an oxidized sodium alginate precipitate; 2) Using the oxidized sodium alginate precipitate as a raw material for oxidized sodium alginate, and extracting it using the method for extracting oxidized sodium alginate according to any one of claims 1 to 7 to obtain oxidized sodium alginate.

9. The method for preparing oxidized sodium alginate according to claim 8, characterized in that: In the 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, the sodium alginate is replaced by 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.

10. An oxidized sodium alginate, characterized in that: The method is obtained by the method of any one of claims 1 to 7 or by the method of claim 8 or 9.

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

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