High-porosity double-crosslinked sodium alginate-chitosan composite microsphere and preparation method thereof

Abstract

The invention discloses a high-porosity double-crosslinked sodium alginate-chitosan composite microsphere and a preparation method thereof, and belongs to the technical field of high polymer materials. The preparation method comprises the following steps: dissolving water-soluble chitosan and sodium alginate in an alkaline solution, carrying out homogeneous emulsification to form a W / O emulsion, carrying out Cacrosslinking on a sodium alginate network, adjusting the system to be acidic, triggering chitosan protonation and sodium alginate electrostatic adsorption to form a homogeneous interpenetrating structure, washing, and drying to obtain the sodium alginate-chitosan composite microspheres. The preparation method does not need to add an organic pore-foaming agent or depend on a freeze-drying process, and the prepared composite microspheres are uniform in pore distribution inside the microspheres, high in specific surface area and high in mechanical strength. The process is simple and environment-friendly, solves the problems of homogeneity and porosity of the composite microspheres, and is suitable for the fields of drug controlled release, adsorption separation and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high polymer materials, and particularly relates to a high-porosity double-crosslinked sodium alginate-chitosan composite microsphere and a preparation method thereof. BACKGROUND

[0002] Microsphere materials have wide application prospects in the fields of drug delivery systems, adsorption separation, tissue engineering scaffolds, etc. due to their unique physical and chemical properties. In recent years, natural polymer materials have become an ideal choice for constructing microsphere materials due to their good biocompatibility, biodegradability and low toxicity. Among them, sodium alginate and chitosan, as two important natural polysaccharides, are widely used in the field of microsphere preparation due to their excellent gelation performance and functional characteristics. At present, the methods for preparing sodium alginate-chitosan microspheres mainly include emulsion crosslinking method, spray drying method and microfluidic technology.

[0003] Chinese patent CN104434879B discloses a preparation method of chitosan-sodium alginate drug-loaded microcapsules. The steps of the preparation method are: (1) uniformly mix oleic acid, Span-80, Tween-80 and propylene glycol in proportion, then add 2% sodium alginate solution, and emulsify with an emulsifier at a stirring speed of 800 r / min for 3-5 min to prepare a latex. (2) Add the latex into 1.5% calcium chloride solution to prepare 80-60 μm small latex particles; (3) take the condensed particles and add them into 1.5% chitosan solution to undergo polyelectrolyte complexation reaction. After 3-4 h of polymerization reaction, chitosan-sodium alginate microcapsules are formed.

[0004] Chinese patent CN119606888A discloses a sodium alginate / chitosan microsphere for loading cells and a preparation method thereof. The preparation method comprises adding a porogen to a sodium alginate solution and stirring overnight to obtain a sodium alginate solution containing the porogen; dissolving chitosan in an acetic acid solution, then adding calcium chloride and stirring until completely dissolved to obtain a chitosan mixture; adding the sodium alginate solution containing the porogen into the chitosan mixture, then standing, filtering to obtain a microsphere precipitate; soaking the microsphere precipitate in a hydrochloric acid solution until no air bubbles overflow, filtering, then cleaning, drying.

[0005] However, the prior art mainly uses sodium alginate as the core and chitosan as the shell layer. The existing microsphere preparation method still has the following problems: (1) dissolution limitation: traditional chitosan needs to be dissolved in an acidic condition (such as acetic acid or oleic acid), and when mixed with sodium alginate, phase separation is easily caused due to charge repulsion, affecting the homogeneity of the microspheres. (2) insufficient porosity: conventional sodium alginate microspheres rely on single ion crosslinking (such as Ca²⁺), and need to add a pore-forming agent (such as polyethylene glycol) or a freeze-drying process, which is complex and poor in environmental protection, and the porosity of the product is insufficient. (3) difficulty in structure control: the existing method is difficult to simultaneously achieve the homogeneity and porosity of the microspheres, and the mechanical strength is low. SUMMARY

[0006] In view of the above problems, the purpose of the present application is to provide a high-porosity double-crosslinked sodium alginate-chitosan composite microsphere and a preparation method thereof.

[0007] In order to achieve the above-mentioned purpose, the present application provides the following technical scheme: a preparation method of a high-porosity double-crosslinked sodium alginate-chitosan composite microsphere, comprising the following steps: (1) Alkaline glue preparation: dissolving sodium alginate and water-soluble chitosan in a NaOH aqueous solution to obtain an alkaline glue; (2) Homogeneous emulsification: uniformly mixing the oil phase and the emulsifier, adding the alkaline glue, and homogeneously emulsifying to form a W / O emulsion; (3) Ion crosslinking: adding a CaCl2 aqueous solution to the W / O emulsion, stirring to form nascent microspheres, and obtaining a system containing the nascent microspheres; (4) pH regulation: adjusting the pH of the system containing the nascent microspheres to be acidic, stirring, forming sodium alginate-chitosan composite microspheres, and obtaining a system containing the composite microspheres; (5) Post-treatment: centrifuging the system containing the composite microspheres, collecting the microspheres, washing, drying, and obtaining the high-porosity double-crosslinked sodium alginate-chitosan composite microspheres.

[0008] More preferably, the concentration of the NaOH aqueous solution in step (1) is 0.1-0.2wt%.

[0009] Preferably, the mass ratio of sodium alginate to water-soluble chitosan in step (1) is 2: (0.5-2.0).

[0010] More preferably, the mass ratio of sodium alginate to water-soluble chitosan in step (1) is 2:1.0.

[0011] When the composite microspheres prepared under the specific mass ratio of sodium alginate to water-soluble chitosan have a more uniform internal pore distribution, and at the same time have a high specific surface area.

[0012] Preferably, the oil phase is selected from white oil.

[0013] Preferably, the emulsifier is selected from one of emulsifier EM90, Span 80.

[0014] More preferably, the emulsifier is selected from emulsifier EM90.

[0015] Preferably, the homogenization in step (2) is performed at 3000-4000 rpm for 5-15 min.

[0016] More preferably, the homogenization in step (2) is performed at 3500 rpm for 5 min.

[0017] Preferably, the volume ratio of the oil phase to the alkaline glue solution is 1:(0.2-0.3).

[0018] More preferably, the volume ratio of the white oil to the alkaline glue solution is 1:0.25.

[0019] It is found in the experiment that the uniformity of the composite microspheres can be improved by using specific oil phase and emulsifier, and by regulating the ratio between the emulsifier, the alkaline glue solution and the oil phase. Especially when the oil phase is selected from white oil and the emulsifier is selected from emulsifier EM90, the uniformity of the composite microspheres is better.

[0020] Preferably, the volume ratio of the oil phase to the emulsifier is 1:(0.05-0.2).

[0021] More preferably, the volume ratio of the oil phase to the emulsifier is 1:0.1.

[0022] Preferably, the method for adjusting the pH of the system containing nascent microspheres to be acidic is adding acetic acid to the system containing nascent microspheres.

[0023] Preferably, the volume of acetic acid added accounts for 10-100% of the volume of the alkaline glue solution.

[0024] More preferably, the volume of acetic acid added accounts for 10% of the volume of the alkaline glue solution.

[0025] Preferably, the concentration of the CaCl2 aqueous solution is 3-8 wt%, and the volume of the CaCl2 aqueous solution added is the same as the volume of the alkaline glue solution.

[0026] More preferably, the concentration of the CaCl2 aqueous solution is 3 wt%.

[0027] By controlling the concentration and amount of calcium chloride, the porosity of the composite microspheres can be improved. It is also found in the experiment that by regulating the concentration of sodium hydroxide in step (1) and the specific relationship between the amount of acetic acid and the amount of alkaline glue solution in step (4), the uniformity and specific surface area of the composite microspheres can be improved.

[0028] The second aspect of the present application provides the high porosity double crosslinked sodium alginate-chitosan composite microspheres prepared by the preparation method.

[0029] Preferably, the specific surface area of the sodium alginate-chitosan composite microspheres is greater than or equal to 324 m² / g.

[0030] Compared with the prior art, the present application has the following advantages and beneficial effects: 1. The present application provides a high porosity double crosslinked sodium alginate-chitosan composite microspheres and a preparation method thereof. By using an alkaline dissolution synergistic mechanism, using sodium alginate and carboxymethyl chitosan as raw materials, the traditional acid dissolution restriction is broken through, and the molecular level uniform mixing of sodium alginate-chitosan is realized in an alkaline environment. The preparation method of the present application avoids the use of organic solvents or freeze-drying steps, meets the requirements of green chemistry, and is suitable for drug carriers, adsorption materials or tissue engineering scaffolds. Especially for drugs such as bovine serum albumin, it has a large adsorption capacity; 2. The present application adopts a dynamic double crosslinking strategy. First crosslinking: Ca²⁺ is chelated with the carboxyl group of sodium alginate to form an ionic crosslinking network; second crosslinking: under acidic conditions, the chitosan amino group is protonated (-NH3⁺) and electrostatically combined with the sodium alginate carboxylate (-COO⁻). The present application first crosslinks sodium alginate with calcium ions to form a stable structure, then adjusts the pH to be acidic by adding acetic acid, so that the chitosan is positively charged and electrostatically adsorbed with the negatively charged sodium alginate, the network shrinks to produce pores, and the internal pores of the microspheres are uniformly distributed, and the specific surface area is high. At the same time, compared with traditional sodium alginate microspheres, the composite microspheres have a double crosslinked structure and higher mechanical strength; 3. The present application adopts an in-situ pore generation technology, which induces the difference in double network shrinkage by pH regulation to generate through pores, and the internal structure of the microspheres presents a three-dimensional interconnected pore structure, avoiding the use of exogenous pore-forming agents, simplifying the preparation process, reducing the cost, and having good application prospect and industrialization value; 4. The present application effectively solves the problems of difficult to balance the uniformity and porosity of the microspheres and low mechanical strength in the prior art by innovative preparation process and formula design. The composite microspheres prepared by the present application have a highly uniform spherical structure and internal porous network, significantly improving the specific surface area of the material and the mechanical strength of the microspheres. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The preparation method flow chart of the high porosity double crosslinked sodium alginate-chitosan composite microspheres of the present application; Figure 2 The preparation method device flow chart of the high porosity double crosslinked sodium alginate-chitosan composite microspheres of Example 1; Figure 3Scanning electron micrograph of high porosity double crosslinked sodium alginate-chitosan composite microspheres of Example 1. Figure 4 Scanning electron micrograph of high porosity double crosslinked sodium alginate-chitosan composite microspheres of Example 1. Figure 5 Scanning electron micrograph of high porosity double crosslinked sodium alginate-chitosan composite microspheres of Example 2. Figure 6 Scanning electron micrograph of high porosity double crosslinked sodium alginate-chitosan composite microspheres of Example 3. Figure 7 Scanning electron micrograph of high porosity double crosslinked sodium alginate-chitosan composite microspheres of Example 4. Figure 8 Scanning electron micrograph of high porosity double crosslinked sodium alginate-chitosan composite microspheres of Example 5. Figure 9 Results chart of physical adsorption characterization of high porosity double crosslinked sodium alginate-chitosan composite microspheres of Example 1. Figure 10 Pore size distribution chart of high porosity double crosslinked sodium alginate-chitosan composite microspheres of Example 1. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0033] The raw materials used in the following embodiments are all commercially available products.

[0034] White oil, brand Xinhua, No. 26 cosmetic grade white oil.

[0035] Water-soluble chitosan, brand Maikelin, molecular weight Mw 800-1000.

[0036] Emulsifier EM90, brand Yinchuang Degussa, ABIL EM90 water-in-oil emulsifier.

[0037] Example 1 Please refer to Figures 1-2 The present embodiment provides a high porosity double crosslinked sodium alginate-chitosan composite microsphere, and a preparation method thereof includes the following steps: (1) Alkaline glue preparation: dissolve sodium alginate and water-soluble chitosan in 0.1% NaOH aqueous solution to obtain an alkaline glue, the mass fraction of sodium alginate in the alkaline glue is 2%, and the mass fraction of chitosan in the alkaline glue is 1%; (2) Homogeneous emulsification: pour the alkaline glue into the mixed white oil and emulsifier EM90, the volume ratio of white oil to emulsifier EM90 is 1:0.1, and the volume ratio of white oil to alkaline glue is 1:0.25, homogenize and emulsify at 3500 rpm for 5 min to form a stable W / O emulsion; (3) Ionic crosslinking: add 3wt% CaCl2 aqueous solution to the emulsion of step (2), the volume of the calcium chloride aqueous solution is the same as that of the alkaline glue, and stir at 240 rpm for 3h to form primary microspheres; (4) pH regulation: continue to add acetic acid, the volume of acetic acid accounts for 10% of the volume of the alkaline glue, adjust the system to be acidic, continue to stir for 2h, and form sodium alginate-chitosan composite porous structure microspheres; (5) Post-processing: centrifugal collection of microspheres, sequentially washed with petroleum ether and ethanol, and dried at 60°C.

[0038] Example 2 The embodiment provides a high-porosity double-crosslinked sodium alginate-chitosan composite microsphere, and a preparation method thereof comprises the following steps: (1) Alkaline glue preparation: dissolve sodium alginate and water-soluble chitosan in 0.2% NaOH aqueous solution to obtain an alkaline glue, the mass fraction of sodium alginate in the alkaline glue is 2%, and the mass fraction of chitosan in the alkaline glue is 2%; (2) Homogeneous emulsification: pour the alkaline glue into the mixed white oil and emulsifier EM90, the volume ratio of white oil to emulsifier EM90 is 1:0.1, and the volume ratio of white oil to alkaline glue is 1:0.25, homogenize and emulsify at 3500 rpm for 10 min to form a stable W / O emulsion; (3) Ionic crosslinking: add 4wt% CaCl2 aqueous solution to the emulsion of step (2), the volume of the calcium chloride aqueous solution is the same as that of the alkaline glue, and stir at 240 rpm for 3h to form primary microspheres; (4) pH regulation: continue to add acetic acid, the volume of acetic acid accounts for 20% of the volume of the alkaline glue, adjust the system to be acidic, continue to stir for 2h, and form sodium alginate-chitosan composite porous structure microspheres; (5) Post-processing: centrifugal collection of microspheres, sequentially washed with petroleum ether and ethanol, and dried at 60°C.

[0039] Example 3 The embodiment provides a preparation method of high porosity double-crosslinked sodium alginate-chitosan composite microspheres, and comprises the following steps: (1) Alkaline glue solution preparation: sodium alginate and water-soluble chitosan are dissolved in 0.1% NaOH aqueous solution to obtain an alkaline glue solution, the mass fraction of sodium alginate in the alkaline glue solution is 2%, and the mass fraction of chitosan in the alkaline glue solution is 1.5%; (2) Homogeneous emulsification: the alkaline glue solution is poured into mixed white oil and emulsifier EM90, the volume ratio of white oil to emulsifier EM90 is 1:0.1, the volume ratio of white oil to the alkaline glue solution is 1:0.2, homogeneous emulsification is carried out at 3500 rpm for 10 min, and a stable W / O emulsion is formed; (3) Ionic crosslinking: 5wt% CaCl2 aqueous solution is added dropwise into the emulsion of step (2), the adding volume of the calcium chloride aqueous solution is the same as that of the alkaline glue solution, stirring is carried out at 240 rpm for 3h, and nascent microspheres are formed; (4) pH regulation: acetic acid is continuously added, the volume of the acetic acid accounts for 100% of the volume of the alkaline glue solution, the system is adjusted to be acidic, stirring is continuously carried out for 2h, and sodium alginate-chitosan composite porous structure microspheres are formed; (5) Post-treatment: the microspheres are collected by centrifugation, sequentially washed with petroleum ether and ethanol, and dried at 60 DEG C.

[0040] Example 4 The embodiment provides a preparation method of high porosity double-crosslinked sodium alginate-chitosan composite microspheres, and comprises the following steps: (1) Alkaline glue solution preparation: sodium alginate and water-soluble chitosan are dissolved in 0.1% NaOH aqueous solution to obtain an alkaline glue solution, the mass fraction of sodium alginate in the alkaline glue solution is 2%, and the mass fraction of chitosan in the alkaline glue solution is 1.5%; (2) Homogeneous emulsification: the alkaline glue solution is poured into mixed white oil and emulsifier EM90, the volume ratio of white oil to emulsifier EM90 is 1:0.2, the volume ratio of white oil to the alkaline glue solution is 1:0.2, homogeneous emulsification is carried out at 3500 rpm for 15 min, and a stable W / O emulsion is formed; (3) Ionic crosslinking: 5wt% CaCl2 aqueous solution is added dropwise into the emulsion of step (2), the adding volume of the calcium chloride aqueous solution is the same as that of the alkaline glue solution, stirring is carried out at 240 rpm for 3h, and nascent microspheres are formed; (4) pH regulation: acetic acid is continuously added, the volume of the acetic acid accounts for 100% of the volume of the alkaline glue solution, the system is adjusted to be acidic, stirring is continuously carried out for 2h, and sodium alginate-chitosan composite porous structure microspheres are formed; (5) Post-treatment: the microspheres are collected by centrifugation, sequentially washed with petroleum ether and ethanol, and dried at 60 DEG C.

[0041] Example 5 The embodiment provides a preparation method of high porosity double-crosslinked sodium alginate-chitosan composite microspheres, and comprises the following steps: (1) preparation of alkaline glue solution: sodium alginate and water-soluble chitosan are dissolved in 0.2% NaOH aqueous solution to obtain an alkaline glue solution, the mass fraction of sodium alginate in the alkaline glue solution is 2%, and the mass fraction of chitosan in the alkaline glue solution is 2%; (2) homogenization and emulsification: the alkaline glue solution is poured into mixed white oil and emulsifier EM90, the volume ratio of white oil to emulsifier EM90 is 1:0.1, the volume ratio of white oil to alkaline glue solution is 1:0.2, homogenization and emulsification are performed at 3500 rpm for 10 min to form a stable W / O emulsion; (3) ion crosslinking: 8wt% CaCl2 aqueous solution is added dropwise into the emulsion of step (2), the volume of the calcium chloride aqueous solution is the same as that of the alkaline glue solution, and stirring is performed at 240 rpm for 3 h to form nascent microspheres; (4) pH regulation: acetic acid is continuously added, the volume of the acetic acid accounts for 50% of the volume of the alkaline glue solution, the system is adjusted to be acidic, and stirring is continuously performed for 2 h to form sodium alginate-chitosan composite porous structure microspheres; (5) post-treatment: the microspheres are collected by centrifugation, sequentially washed with petroleum ether and ethanol, and dried at 60°C.

[0042] The high porosity double-crosslinked sodium alginate-chitosan composite microspheres prepared in Examples 1-5 are detected by using a scanning electron microscope, and it is found that Figures 3-10 It can be seen from the SEM that the composite microspheres have uniform pore distribution on the surface and inside, and have high specific surface area. Figures 9-10 It can be seen from the SEM that the composite microspheres have uniform pore distribution on the surface and inside, and have high specific surface area.

[0043] The above describes preferred embodiments of the present application, and it should be noted that, for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A method for preparing high-porosity, double-crosslinked sodium alginate-chitosan composite microspheres, characterized in that, Includes the following steps: (1) Preparation of alkaline adhesive solution: Sodium alginate and water-soluble chitosan are dissolved in NaOH aqueous solution to obtain alkaline adhesive solution; (2) Homogenization emulsification: Mix the oil phase and emulsifier evenly, add alkaline glue, and homogenize emulsify to form a W / O emulsion; (3) Ionic crosslinking: Add CaCl2 aqueous solution dropwise to W / O emulsion and stir to form primary microspheres to obtain a system containing primary microspheres; (4) pH control: Adjust the pH of the system containing the nascent microspheres to acidic, stir to form sodium alginate-chitosan composite microspheres, and obtain the system containing composite microspheres; (5) Post-processing: The system containing composite microspheres was centrifuged, the microspheres were collected, washed and dried to obtain high-porosity double cross-linked sodium alginate-chitosan composite microspheres.

2. The method for preparing high-porosity, double-crosslinked sodium alginate-chitosan composite microspheres according to claim 1, characterized in that, The concentration of the NaOH aqueous solution in step (1) is 0.1-0.2 wt%.

3. The method for preparing high-porosity, double-crosslinked sodium alginate-chitosan composite microspheres according to claim 1, characterized in that, In step (1), the mass ratio of sodium alginate to water-soluble chitosan is 2:(0.5-2.0).

4. The method for preparing high-porosity, double-crosslinked sodium alginate-chitosan composite microspheres according to claim 1, characterized in that, The oil phase in step (2) is selected from white oil.

5. The method for preparing high-porosity, double-crosslinked sodium alginate-chitosan composite microspheres according to claim 4, characterized in that, In step (2), the emulsifier is selected from at least one of emulsifiers EM90, Tween 80, Tween 20, and Span 80.

6. The method for preparing high-porosity, double-crosslinked sodium alginate-chitosan composite microspheres according to claim 5, characterized in that, The volume ratio of the oil phase to the emulsifier in step (2) is 1:(0.05-0.2).

7. The method for preparing high-porosity, double-crosslinked sodium alginate-chitosan composite microspheres according to claim 5, characterized in that, The method for adjusting the pH of the system containing the nascent microspheres to acidic in step (4) is as follows: add acetic acid to the system containing the nascent microspheres, and the volume of acetic acid added accounts for 10-100% of the volume of the alkaline gel.

8. The method for preparing high-porosity, double-crosslinked sodium alginate-chitosan composite microspheres according to claim 1, characterized in that, In step (3), the concentration of the CaCl2 aqueous solution is 3-8 wt%; the volume of the CaCl2 aqueous solution added is the same as the volume of the alkaline adhesive solution.

9. The method for preparing high-porosity, double-crosslinked sodium alginate-chitosan composite microspheres according to claim 1, characterized in that, The volume ratio of the oil phase to the alkaline adhesive is 1:(0.2-0.3).

10. A high-porosity, double-crosslinked sodium alginate-chitosan composite microsphere prepared by the preparation method according to any one of claims 1-9.

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