Chitosan-based astaxanthin sustained-release microsphere and preparation method thereof

Abstract

The invention relates to the technical field of preparation of astaxanthin sustained-release microspheres, and discloses chitosan-based astaxanthin sustained-release microspheres and a preparation method thereof.The method comprises the steps that chitosan powder is dissolved in an acetic acid solution, the pH value is adjusted, and a chitosan solution is prepared; dissolving astaxanthin in ethanol, and then adding the chitosan solution; adding a cross-linking solution into the emulsified solution, and performing cross-linking under a magnetic stirring condition to form astaxanthin sustained-release microspheres; adding the astaxanthin sustained-release microspheres into a strengthening solution for strengthening treatment; carrying out coating treatment on the astaxanthin sustained release microspheres subjected to the strengthening treatment; carrying out centrifugal treatment on the solution subjected to coating treatment, and collecting astaxanthin sustained-release microspheres subjected to centrifugal separation; and washing the collected astaxanthin sustained-release microspheres with PBS (Phosphate Buffer Solution). According to the invention, chitosan is used as a carrier to prepare the astaxanthin sustained-release microspheres, so that the astaxanthin can be continuously and stably released in intestinal tracts, the antioxidant and anti-inflammatory activity of the astaxanthin can be fully exerted, and further, the astaxanthin sustained-release microspheres have an effective treatment effect on osteoarthritis.

Description

Technical Field

[0001] The present invention relates to the technical field of astaxanthin sustained-release microsphere preparation, and in particular to chitosan-based astaxanthin sustained-release microspheres and a preparation method thereof. Background Art

[0002] Osteoarthritis is a common degenerative joint disease characterized by cartilage degradation, synovial inflammation, and bone hyperplasia. As oxidative stress plays a key role in the development and progression of osteoarthritis, antioxidants are considered a potential therapeutic strategy. Astaxanthin is a potent antioxidant with anti-inflammatory, antioxidant, and cartilage-protective effects; however, its poor water solubility, low bioavailability, and rapid metabolism limit its application in the treatment of osteoarthritis. Chitosan, a natural cationic polysaccharide with excellent biocompatibility, degradability, and film-forming properties, can be used to prepare sustained-release microspheres to improve drug stability and sustained-release efficacy.

[0003] Existing technologies for preparing astaxanthin sustained-release microspheres are unable to meet the clinical application needs of osteoarthritis due to uncontrolled release, poor stability, and complex processes. Calcium alginate microspheres prepared using the traditional double-emulsion method suffer from uneven emulsification and low cross-linking density, leading to significant leakage of astaxanthin during washing and drying, significantly reducing the retention of the active ingredient in the final product. Furthermore, astaxanthin is susceptible to environmental degradation during processing and storage.

[0004] Therefore, there is an urgent need to develop an innovative microsphere system with high encapsulation efficiency, colon-targeted release ability, excellent stability and low-cost preparation to achieve the efficient application of astaxanthin in functional food and drug delivery. Summary of the Invention

[0005] The present invention provides a chitosan-based astaxanthin sustained-release microspheres and a preparation method thereof. The method uses chitosan as a carrier to prepare astaxanthin sustained-release microspheres, which can prolong the retention and release time of astaxanthin in the intestine, and effectively solve the technical difficulties in the treatment of osteoarthritis by continuously exerting antioxidant and anti-inflammatory effects.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions: The present invention provides a chitosan-based astaxanthin sustained-release microsphere and a preparation method thereof, comprising the following steps: S1, dissolving chitosan powder in acetic acid solution and adjusting the pH value to prepare a chitosan solution; S2, dissolving astaxanthin in ethanol and then adding chitosan solution, and using ultrasonic treatment to emulsify the solution uniformly; S3, adding a cross-linking solution to the emulsified solution, and cross-linking under magnetic stirring to form astaxanthin sustained-release microspheres; S4, adding the treated astaxanthin sustained-release microspheres into the enhanced solution, and promoting the enhanced solution to be embedded in the sustained-release microspheres by applying mechanical vibration; S5, coating the enhanced astaxanthin sustained-release microspheres to increase their wall thickness; S6, centrifuging the coated solution and collecting the astaxanthin sustained-release microspheres after centrifugation; S7, the collected astaxanthin sustained-release microspheres are first washed with PBS and then freeze-dried, and then stored after the freeze-drying process is completed.

[0007] The beneficial effects brought about by the technical solution provided by the present invention include at least: The present invention uses chitosan as a carrier and enhances the mechanical properties of sustained-release microspheres to achieve precise regulation of the intestinal release rate of astaxanthin, significantly improving its stability and bioavailability in the body. The present invention optimizes the particle size distribution and surface properties of astaxanthin sustained-release microspheres by coating astaxanthin, effectively prolonging their retention time in the joint cavity and further enhancing the therapeutic effect. At the same time, astaxanthin inhibits cartilage degradation through its dual antioxidant and anti-inflammatory effects, and chitosan can promote cartilage repair. The two form a synergistic mechanism, thereby achieving efficient treatment of osteoarthritis. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0009] Figure 1 The present invention provides a flowchart of a method for preparing chitosan-based astaxanthin sustained-release microspheres. DETAILED DESCRIPTION

[0010] To make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0011] Example A chitosan-based astaxanthin sustained-release microsphere and a preparation method thereof.

[0012] Please refer to Figure 1 , Figure 1 The present invention provides a flowchart of a method for preparing chitosan-based astaxanthin sustained-release microspheres.

[0013] S1, dissolving chitosan powder in acetic acid solution and adjusting the pH value to prepare a chitosan solution; S101, the molecular weight of the chitosan powder used is maintained at 50-200 kDa, the concentration of the acetic acid solution is 1%, and the acetic acid solution must be precooled to below 10°C before mixing with the chitosan powder; S102, adding a pH regulator composed of a weak acid-conjugate base buffer pair to the chitosan solution to stably maintain the pH value of the solution at 5.5, and adding a fat-soluble antioxidant to prevent astaxanthin from being oxidized in subsequent steps; It should be noted that the buffer pair is acetic acid-sodium acetate, and the buffer system replaces the strong base to eliminate the risk of gelation caused by local pH mutation.

[0014] S103, chitosan solution is obtained by introducing inert gas and keeping it in dark conditions, and using pulsed low-power ultrasonic treatment.

[0015] It should be noted that in the process of preparing the chitosan solution, a dilute acetic acid solution with a concentration of 1% is first gradually added dropwise to the chitosan powder, and a pH regulator composed of a weak acid-conjugate base buffer pair is added to the dissolved chitosan solution. At the same time, the antioxidant butylated hydroxytoluene with a concentration of 0.1% w / v is dissolved in anhydrous ethanol and then added to the chitosan solution. During this process, helium (inert gas) is continuously introduced at a flow rate of 0.1 L / min, and the solution is treated with pulsed low-power ultrasound at an ultrasonic power of 100 W and a pulse mode with an interval of 2s to finally obtain a chitosan solution with a concentration of 2%.

[0016] S2, dissolving astaxanthin in ethanol and then adding chitosan solution, and emulsifying the solution uniformly by ultrasonic treatment; S201, astaxanthin was first dissolved in anhydrous ethanol containing porphyrin zinc molecular cages, treated with pulsed strong light, and then precooled to below -15°C; It should be noted that the porphyrin zinc molecular cage has a tetraphenylporphyrin structure, the central zinc ion of which can coordinate with the terminal ketone group of astaxanthin, and the side chain phenyl group is modified with perfluorohexane.

[0017] S202, chitosan solution is maintained in a CO2 environment at a pressure of 10 bar, and astaxanthin solution is injected through a microfluidic Janus nozzle; It should be noted that the inner wall of the Janus nozzle is coated with a titanium dioxide coating with a thickness of 500 nm. In a CO2 environment, photocatalytic hydrophobic micro-regions can be generated on the surface of the titanium dioxide coating, thereby avoiding phase separation caused by the solution.

[0018] S203, ultrasonic treatment includes setting a rotating permanent magnet array on the outer wall of the reaction chamber and synchronously applying orthogonal dual-frequency ultrasonic waves.

[0019] It should be noted that astaxanthin was dissolved in anhydrous ethanol containing 0.3% w / v porphyrin zinc molecular cages and treated with pulsed intense light with a wavelength of 450 nm, an intensity of 5 J / cm², and a pulse width of 2 ms. The chitosan solution was injected into the treated astaxanthin solution through a Janus nozzle with a flow rate of 0.5 mL / min. The solution was uniformly emulsified by setting a rotating permanent magnet array with a rotation speed of 1000 rpm and a magnetic field strength of 0.4 T, combined with dual-frequency ultrasound consisting of axial waves of 8 kHz / 100 W and radial waves of 1.2 MHz / 15 W, to finally obtain an emulsified solution.

[0020] S3, adding a cross-linking solution to the emulsified solution, and performing cross-linking under magnetic stirring to form astaxanthin sustained-release microspheres; S301, the cross-linking solution consists of a sodium tripolyphosphate solution and a TA-CS solution. The emulsified solution needs to be maintained at a constant temperature of 5°C, and a dual-channel peristaltic pump is used to dropwise add the sodium tripolyphosphate solution and the TA-CS solution; It should be noted that the TA-CS solution was prepared by an enzymatic reaction: tannic acid and chitosan were dissolved in an acetate buffer solution with a pH of 4.5 at a mass ratio of 1:10, and 0.5 U / mg of laccase was added. The reaction was carried out at 25°C for 2 h, and then the solution was purified by ultrafiltration with a molecular weight cutoff of 10 kDa.

[0021] S302, the magnetic stirring conditions include stirring time and stirring speed. The stirring time is 30 minutes, and the stirring speed is calculated based on the parameters of the emulsified solution. The specific formula is as follows:

[0022] Where, Indicates stirring speed; Reynolds number, which is determined by the viscosity of the solution and is set to 1800 by default; Indicates the viscosity of the emulsified solution; Indicates the density of the emulsified solution; Indicates the diameter of the stirring blade.

[0023] It should be noted that the Reynolds number value of the emulsified solution corresponds to a viscosity range of 50-200 cP, with 1800 as the default reference and allowed to fluctuate within the range of ±100.

[0024] During the preparation process, a 0.3% w / v sodium tripolyphosphate solution and a 0.1% w / v tannic acid-chitosan complex (TA-CS) solution were simultaneously added dropwise to the emulsified solution through a dual-channel peristaltic pump. The addition rate of the sodium tripolyphosphate solution was 0.5 mL / min, and the addition rate of the tannic acid-chitosan complex (TA-CS) solution was 0.2 mL / min. The emulsified solution was maintained at a constant temperature of 5°C throughout the process. After the addition was completed, magnetic stirring was used for 30 minutes to finally form astaxanthin sustained-release microspheres.

[0025] S4, adding the treated astaxanthin sustained-release microspheres into the strengthening solution, and promoting the embedding of the astaxanthin sustained-release microspheres by applying mechanical vibration; S401, the strengthening solution is a sodium alginate solution with a concentration of ≤0.1% w / v, containing sodium alginate calcium microspheres with a particle size of 5 μm-10 μm; It should be noted that the preparation process of sodium alginate solution is as follows: 2% w / v sodium alginate solution is sucked into the syringe, connected to the dispensing needle and installed on the electrospinning instrument, 4% calcium chloride solution is poured into the receiving tray, and the injection pump is started at a flow rate of 1 mL / min. At the same time, a 5 kV high-voltage power supply is started to spray the sodium alginate droplets into the calcium chloride solution under the action of the electric field force, and sodium alginate calcium microspheres are formed after instant cross-linking.

[0026] S402, the mechanical vibration process is to maintain the cross-linked solution in a constant temperature environment of 25°C, and apply a composite vibration field to the solution using an electromagnetic-piezoelectric composite vibration table; S403, the composite vibration field includes low-frequency mechanical vibration and high-frequency sound field. The frequency of the low-frequency mechanical vibration is calculated based on the particle size of the sodium calcium alginate microspheres. The specific formula is as follows:

[0027] Where, Indicates vibration frequency; Indicates the elastic modulus of sodium calcium alginate microspheres, the default value is 1.2MPa; represents the density of sodium calcium alginate microspheres; represents the particle size of sodium calcium alginate microspheres; S404, the frequency of the high-frequency sound field is set according to the safety threshold of astaxanthin, and the default frequency is 1.2 MHz.

[0028] It should be noted that the actual strengthening operation process of astaxanthin sustained-release microspheres is: the cross-linked astaxanthin sustained-release microspheres are transferred to a sodium alginate solution with a concentration of 0.1% w / v (the sodium alginate solution contains 5μm-10μm sodium alginate calcium microspheres), and then a composite vibration field is applied to the solution through an electromagnetic-piezoelectric composite vibration table. A low-frequency mechanical vibration with a frequency of 22.5Hz and an amplitude of 1.0mm, and a high-frequency sound field with a frequency of 1.0±0.1MHz and a sound intensity of 0.5W / cm² are used to make the sodium alginate calcium microspheres in the solution migrate in a directional manner, thereby achieving precise pore filling and interface bonding of the astaxanthin sustained-release microspheres, thereby prolonging the disintegration time of the astaxanthin sustained-release microspheres in simulated gastrointestinal fluid.

[0029] S5, increasing the wall thickness of astaxanthin sustained-release microspheres by coating treatment.

[0030] S501, coating treatment: nitrogen is introduced into the strengthened solution to isolate the air, the coating solution is sprayed using a piezoelectric atomizer array, and visible light and near-infrared dual beam irradiation is simultaneously applied to achieve coating and molding of astaxanthin sustained-release microspheres; S502, the coating solution is composed of a mixture of ethanol solution, chitosan azidate, antioxidant and near-infrared absorber.

[0031] It should be noted that the preparation process of the coating solution is as follows: 0.5 g of chitosan azidate is dissolved in 50 mL of ethanol solution, and ultrasonic-assisted treatment is performed at a frequency of 40 kHz and a power of 100 W for 10 minutes to form a completely transparent base liquid. At the same time, 10 mg of tocopherol and 20 mg of ε-polylysine are added to 5 mL of hot ethanol, and vortex mixed for 1 minute to prepare an antioxidant transparent complex solution. The complex solution is then added dropwise to the base liquid, mixed and stirred for 30 minutes, and finally 50 mg of polyacrylate zinc microspheres (porogen) with a particle size of 150-200 nm are added to the mixed solution to obtain a coating solution.

[0032] The coating process can be repeated multiple times, and the actual coating thickness can be calculated using a thickness growth model. The specific formula is as follows:

[0033] Where, Indicates the total thickness after coating the nth layer; represents the initial diameter of astaxanthin sustained-release microspheres; Indicates the number of coating layers.

[0034] It should be noted that the specific steps of the coating treatment are: suspending the enhanced astaxanthin sustained-release microspheres in the aerosolized coating cavity, continuously introducing nitrogen at a flow rate of 5L / min, and spraying the coating solution through a piezoelectric atomization array with a pore size of 20μm and a driving frequency of 120kHz. At the same time, visible light with an intensity of 50W / cm² and near-infrared light with an intensity of 0.8W / cm² are used to heat the coating process, increase the activity of the astaxanthin sustained-release microspheres, and enable the coating solution to solidify quickly. By repeating the above steps, the astaxanthin sustained-release microspheres are coated multiple times so that the astaxanthin sustained-release microspheres can be slowly released. In actual preparation, the thickness of 15 coatings is the optimal value for the sustained release of the microspheres, and the number of coatings can be flexibly adjusted according to demand.

[0035] S6, centrifuging the coated solution and collecting the astaxanthin sustained-release microspheres after centrifugation.

[0036] S601, a centrifugal treatment operation is as follows: placing the solution in a nitrogen protection environment, using a centrifuge for centrifugal separation, and simultaneously applying near-infrared laser to achieve centrifugation under laser guidance; S602, the speed of the centrifuge is adjusted according to the exponential decay curve. The specific formula is as follows:

[0037] Where, represents the speed at time t; Indicates the speed at the initial moment; Represents time parameters; S603, astaxanthin sustained-release microspheres are collected through a microfluidic puncture needle, and targets with a particle size of 200nm-500nm are selected for collection.

[0038] It should be noted that the specific steps of solution centrifugation and collection of astaxanthin sustained-release microspheres are as follows: the solution is centrifuged in a centrifuge with an initial speed of 5000 rpm, the speed is adjusted according to an exponential decay curve, an 808 nm near-infrared laser is used during the centrifugation process, and nitrogen is continuously introduced at a flow rate of 5 L / min. Centrifugation is completed under inert gas protection and laser guidance to avoid the photothermal effect of astaxanthin and ensure the stability of astaxanthin. After centrifugation, a puncture needle with an inner diameter of 1 μm and a piezoelectric ceramic vibrator with an integrated frequency of 28 kHz and an amplitude of 5 μm are used to collect astaxanthin sustained-release microspheres with a particle size of 200 nm-500 nm.

[0039] S7, the collected astaxanthin sustained-release microspheres are first washed with PBS and then freeze-dried, and then stored after the freeze-drying process is completed.

[0040] S701, astaxanthin sustained-release microspheres were washed twice by centrifugation with PBS solution containing trehalose; It should be noted that the trehalose concentration in the PBS solution was 0.1%, and the centrifugal force was set to 800 × g.

[0041] S702, freeze-drying treatment step: pre-freeze the astaxanthin sustained-release microspheres after washing with PBS in a refrigerator for 2 hours, and then vacuum-dry them using a drying device for 24 hours before storage.

[0042] It should be noted that when the astaxanthin sustained-release microspheres are washed with PBS, trehalose can form a glassy protective layer, which inhibits the oxidation reaction by limiting the movement of astaxanthin molecules and ensures the stability of the microspheres. The washed astaxanthin sustained-release microspheres are placed in a -80°C refrigerator for 2 hours for pre-freezing to form glassy ice crystals inside the astaxanthin sustained-release microspheres. They are then transferred to a drying device and vacuum-dried at -40°C and 0.5Pa for 12 hours, and then heated to 25°C at a rate of 0.2°C / min and continued to dry for 12 hours to completely remove the free water and bound water in the astaxanthin microspheres. After freeze-drying, they are stored in nitrogen packaging.

[0043] A chitosan-based astaxanthin sustained-release microsphere is prepared by the preparation method of S1-S7.

[0044] Furthermore, it should be noted that the present invention may be provided as a method, apparatus, or computer program product. Thus, embodiments of the present invention may take the form of entirely hardware embodiments, entirely software embodiments, or embodiments combining software and hardware aspects. Furthermore, embodiments of the present invention may take the form of a computer program product embodied on one or more computer-usable storage media containing computer-usable program code.

[0045] The embodiments of the present invention are described with reference to the flowcharts and / or block diagrams of the methods, terminal devices (systems), and computer program products according to the embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of the processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, an embedded processor, or other programmable data processing terminal device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing terminal device generate instructions for implementing the process in the flowchart and / or block diagram. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0046] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing terminal device to operate in a specific manner, so that the instructions stored in the computer readable memory produce a manufactured product including an instruction device, which implements the process Figure 1a process or multiple processes and / or boxes Figure 1 These computer program instructions can also be loaded onto a computer or other programmable data processing terminal device, so that a series of operation steps are executed on the computer or other programmable terminal device to produce a computer-implemented process, thereby providing instructions for implementing the process in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0047] It should also be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. The terms "comprises," "includes," or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or terminal device that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or terminal device. In the absence of further restrictions, an element defined by the phrase "comprises a ..." does not exclude the presence of additional identical elements in the process, method, article, or terminal device that includes the element.

[0048] Finally, it should be noted that the above is a preferred embodiment of the present invention. It should be noted that although the preferred embodiment of the present invention has been described, it is clear that those skilled in the art, once they understand the basic inventive concept of the present invention, can make various improvements and modifications without departing from the principles of the present invention. Such improvements and modifications should also be considered as within the scope of protection of the present invention. Therefore, the appended claims are intended to be interpreted as including the preferred embodiment and all changes and modifications that fall within the scope of the embodiments of the present invention.

Claims

1. A method for preparing astaxanthin sustained-release microspheres based on chitosan, characterized in that: Here are the steps: S1, dissolving chitosan powder in acetic acid solution and adjusting the pH value to prepare a chitosan solution; S2, dissolving astaxanthin in ethanol and then adding chitosan solution, and using ultrasonic treatment to emulsify the solution uniformly; S3, adding a cross-linking solution to the emulsified solution, and cross-linking under magnetic stirring to form astaxanthin sustained-release microspheres; S4, adding the treated astaxanthin sustained-release microspheres into the enhanced solution, and promoting the enhanced solution to be embedded in the sustained-release microspheres by applying mechanical vibration; S5, coating the enhanced astaxanthin sustained-release microspheres to increase their wall thickness; S6, centrifuging the coated solution and collecting the astaxanthin sustained-release microspheres after centrifugation; S7, the collected astaxanthin sustained-release microspheres are first washed with PBS and then freeze-dried, and then stored after the freeze-drying process is completed.

2. The method for preparing chitosan-based astaxanthin sustained-release microspheres according to claim 1, characterized in that: The S1 specifically includes the following steps: S101, the molecular weight of the chitosan powder is maintained at 50-200 kDa, the concentration of the acetic acid solution is 1%, and the acetic acid solution is pre-cooled to below 10° C. before mixing with the chitosan powder; S102, adding a pH regulator composed of a weak acid-conjugate base buffer pair to the chitosan solution to maintain the pH value of the solution stable at 5.5, and adding a fat-soluble antioxidant to prevent astaxanthin oxidation in subsequent steps; S103, the chitosan solution is prepared by introducing an inert gas, maintaining a light-proof condition, and combining pulsed low-power ultrasonic treatment.

3. The method for preparing chitosan-based astaxanthin sustained-release microspheres according to claim 1, characterized in that: The S2 specifically includes the following steps: S201, the astaxanthin is dissolved in anhydrous ethanol containing porphyrin zinc molecular cage, and then pre-cooled to below -15°C after being treated with pulsed strong light; S202, the chitosan solution is maintained in a CO2 environment at a pressure of 10 bar, and the astaxanthin solution is injected through a microfluidic Janus nozzle; S203, the ultrasonic treatment includes setting a rotating permanent magnet array on the outer wall of the reaction chamber and synchronously applying orthogonal dual-frequency ultrasonic waves.

4. The method for preparing chitosan-based astaxanthin sustained-release microspheres according to claim 1, characterized in that: The S3 specifically includes the following steps: S301, the cross-linking solution is prepared by mixing a sodium tripolyphosphate solution and a TA-CS solution, the emulsified solution is maintained at a constant temperature of 5° C., and the sodium tripolyphosphate solution and the TA-CS solution are added dropwise using a dual-channel peristaltic pump; S302, the magnetic stirring conditions include stirring time and stirring speed. The stirring time is 30 minutes. The stirring speed is calculated based on the parameters of the emulsified solution. The specific formula is as follows: Where, Indicates stirring speed; Reynolds number, which is determined by the viscosity of the solution and is 1800 by default; Indicates the viscosity of the emulsified solution; Indicates the density of the emulsified solution; Indicates the diameter of the stirring blade.

5. The method for preparing chitosan-based astaxanthin sustained-release microspheres according to claim 1, characterized in that: The S4 specifically includes the following steps: S401, the strengthening solution is a sodium alginate solution with a concentration of ≤0.1% w / v, in which sodium alginate calcium microspheres with a particle size of 5 μm-10 μm are dispersed; S402, the mechanical vibration process is to place the cross-linked solution in a constant temperature environment of 25°C, and use an electromagnetic-piezoelectric composite vibration table to apply a composite vibration field to the strengthened solution; S403, the composite vibration field includes a low-frequency mechanical vibration and a high-frequency sound field. The frequency of the low-frequency mechanical vibration is calculated and determined based on the particle size of the sodium calcium alginate microspheres. The specific formula is as follows: Where, Indicates vibration frequency; Indicates the elastic modulus of sodium calcium alginate microspheres, the default value is 1.2MPa; represents the density of sodium calcium alginate microspheres; represents the particle size of sodium calcium alginate microspheres; S404, the frequency of the high-frequency sound field is set according to the safety threshold of astaxanthin, and the default frequency is 1.2 MHz.

6. The method for preparing chitosan-based astaxanthin sustained-release microspheres according to claim 1, characterized in that: The S5 specifically includes the following steps: S501, the coating treatment step comprises: introducing nitrogen into the strengthened solution to isolate the air, spraying the coating solution using a piezoelectric atomization array, and simultaneously applying visible light and near-infrared dual beam irradiation to achieve coating of the astaxanthin sustained-release microspheres; S502, the coating solution is composed of a mixture of ethanol solution, chitosan azidate, antioxidant and near-infrared absorber.

7. The method for preparing chitosan-based astaxanthin sustained-release microspheres according to claim 6, characterized in that: The coating process is repeated multiple times, and the actual coating thickness is calculated using a thickness growth model, as shown in the following formula: Where, Indicates the total thickness after coating the nth layer; represents the initial diameter of astaxanthin sustained-release microspheres; Indicates the number of coating layers.

8. The method for preparing chitosan-based astaxanthin sustained-release microspheres according to claim 1, characterized in that: The S6 specifically includes the following steps: S601, the centrifugal treatment operation is: placing the solution in a nitrogen protection environment, using a centrifuge for centrifugal separation, and simultaneously applying near-infrared laser to achieve centrifugation under laser guidance; S602: The speed of the centrifuge is adjusted according to an exponential decay curve. The specific formula is as follows: Where, represents the speed at time t; Indicates the speed at the initial moment; Represents time parameters; S603, the astaxanthin sustained-release microspheres are collected by a microfluidic puncture needle, and particles with a diameter of 200 nm to 500 nm are selected for collection.

9. The method for preparing chitosan-based astaxanthin sustained-release microspheres according to claim 1, characterized in that: The S7 specifically includes the following steps: S701, the astaxanthin sustained-release microspheres are washed twice by centrifugation using a PBS solution containing trehalose; S702, the freeze-drying step is: pre-freeze the sustained-release microspheres in a refrigerator for 2 hours, then vacuum-dry them using a drying device for 24 hours, and store them after drying.

10. A chitosan-based astaxanthin sustained-release microsphere, characterized in that: The astaxanthin sustained-release microspheres are prepared by the preparation method of chitosan-based astaxanthin sustained-release microspheres according to any one of claims 1 to 9.

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