Preparation method of high-stability NMN nano-microspheres

Abstract

The invention provides a preparation method of NMN nano microspheres with high stability, and belongs to the technical field of NMN. The preparation method comprises the steps of NMN pretreatment, primary microsphere preparation, functional microsphere preparation and mixing. The preparation method of the primary microspheres comprises the following steps: adding epsilon-polylysine and glutathione into an ethanol solution, uniformly stirring, adding 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-hydroxysuccinimide, and stirring for 28-32 minutes to obtain a mixed solution; adding the pretreated NMN solution into the chitosan solution, then adding the mixed solution, and carrying out heat preservation at 44-50 DEG C for 2.8-3.2 h to obtain primary microspheres; the NMN nano-microsphere prepared by the method disclosed by the invention is good in stability and good in slow release performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of NMN, and specifically relates to a method for preparing NMN nanoparticles with high stability. Background Art

[0002] NMN, the full name of which is β-nicotinamide mononucleotide, is also known as nicotinamide mononucleotide. It is a naturally occurring biologically active nucleotide that exists in various organisms and is also a cosmetic raw material. It is white to slightly yellow in color, a crystalline powder, and has no obvious odor. NMN is the precursor of the coenzyme NAD+ in the human body. NAD+ plays a vital role in many key physiological processes such as cellular energy metabolism, DNA repair, and gene expression regulation. With the deepening of research, NMN has shown great application potential in delaying aging, improving metabolic diseases, neuroprotection, and cardiovascular disease treatment. It has received widespread attention and application in the fields of health care products and pharmaceuticals.

[0003] However, NMN is sensitive to light and oxygen, has poor stability, cannot be stored for a long time, has low oral bioavailability, and is easily affected by the gastrointestinal environment, which limits its scope of application. Preparing NMN into nanospheres can significantly improve its stability and bioavailability, and can protect NMN from damage by external factors such as pH and enzymatic hydrolysis, thereby improving its stability and enabling it to better exert its efficacy.

[0004] At present, the preparation methods of NMN nanoparticles mainly include emulsion polymerization, solvent volatilization and spray drying; however, the emulsion polymerization method usually uses more surfactants, which easily introduces impurities and affects the safety performance of NMN nanoparticles; the solvent volatilization method has a long preparation cycle, and the solvent is difficult to completely remove, which not only easily leads to NMN inactivation, but also poses a danger to human health; the nanoparticles prepared by the spray drying method have uneven particle size distribution, and are easily inactivated by NMN under high temperature conditions, affecting its efficacy.

[0005] CN113559082A discloses a method for preparing NMN nanoparticles and their application, the method comprising the following steps: (1) dispersing NMN particles in a coating material and stirring uniformly to obtain a mixed powder, wherein the coating material includes corn ethanol, shellac ethanol, gelatin, konjac glucomannan, and nano bone powder; (2) Adding a wetting agent and a binder to the mixed powder, stirring evenly, and drying to obtain NMN nanoparticles with a core-shell structure.

[0006] This patent encapsulates NMN nanoparticles in a coating layer of special ingredients, which can protect NMN from being easily decomposed by environmental influences. It remains in simulated gastric fluid for 2 hours with a release rate of 24.3%-33.2%; its release rate in simulated gastric fluid is still relatively fast and cannot play a good sustained-release role. Summary of the invention

[0007] In order to solve the technical problems existing in the prior art, the present invention provides a method for preparing NMN nanoparticles with high stability, excellent sustained-release performance and good long-term effect.

[0008] In view of the above technical problems, the present invention adopts the following technical solutions: A method for preparing NMN nanoparticles with high stability, comprising NMN pretreatment, preparation of primary microparticles, preparation of functionalized microparticles and mixing steps, and the specific operations are as follows: 1. NMN pretreatment Put NMN into anhydrous ethanol, stir evenly, add L-ascorbic acid and tea polyphenols, raise the temperature to 32-38°C, and perform ultrasonic treatment. The ultrasonic time is 26-35 minutes, the ultrasonic power is 110-130W, and the ultrasonic frequency is 24-28kHz. After the ultrasonic treatment, a pretreated NMN solution is obtained; The mass volume ratio of the NMN, anhydrous ethanol, L-ascorbic acid and tea polyphenols is 8-12g:140-160mL:0.14-0.16g:0.10-0.13g.

[0009] 2. Preparation of primary microspheres Add chitosan to the acetic acid solution, stir evenly to obtain a chitosan solution; add ε-polylysine and glutathione to the ethanol solution, stir evenly, add 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide, stir for 28-32 minutes to obtain a mixed solution; add the pretreated NMN solution to the chitosan solution, stir at 140-160 rpm for 18-22 minutes, add the mixed solution, increase the temperature to 44-50°C, keep warm and stir for 2.8-3.2 hours, filter, wash and dry to obtain primary microspheres; The mass ratio of chitosan to acetic acid solution is 4.5-5.5:95-106; The mass concentration of the acetic acid solution is 2.2-2.7%; The mass ratio of the ε-polylysine, glutathione, ethanol solution, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide is 3.2-3.8:2.2-2.7:95-105:2.3-2.8:2.5-3.0; The mass concentration of the ethanol solution is 22-28%; The mass ratio of the pretreated NMN solution, the chitosan solution and the mixed solution is 146-155:34-38:26-30.

[0010] 3. Preparation of Functionalized Microspheres Adding primary microspheres to the ethanol solution, stirring evenly, adding functional konjac glucomannan, keeping warm at 36-40°C for 2.8-3.2h, then adding sodium alginate and carrageenan, stirring evenly, filtering, washing and drying to obtain functionalized microspheres; The mass ratio of the ethanol solution, the primary microspheres, the functional konjac glucomannan, the sodium alginate and the carrageenan is 180-220:9.5-10.4:2.0-2.3:0.5-0.8:0.3-0.5; The mass ratio of the ethanol solution is 30-34%; The preparation method of the functional konjac glucomannan is as follows: placing the konjac glucomannan in deionized water, stirring and dissolving at 38-42° C., then adding sodium periodate, reacting for 5.8-6.2 hours under light-proof conditions, then adding ethylene glycol to terminate the reaction, and drying to obtain the functional konjac glucomannan; The mass volume ratio of the konjac glucomannan, deionized water, sodium periodate and ethylene glycol is 4.8-5.2 g: 380-420 mL: 3.0-3.4 g: 0.8-1.2 mL.

[0011] 4. Mix The functionalized microspheres were mixed evenly with polyvinyl pyrrolidone and microcrystalline cellulose, and then added to the ethanol solution. After continuing to stir evenly, starch solution was added for homogenization. The homogenization times were 2 times, the homogenization pressure was 5.8-6.3 MPa, and the homogenization time was 1.5-2.5 min each time. After the homogenization treatment was completed, the mixture was filtered and washed, freeze-dried for 22-25 h, and crushed to obtain NMN nano-microspheres. The mass ratio of the functionalized microspheres, polyvinyl pyrrolidone, microcrystalline cellulose, ethanol solution, and starch solution is 10.3-10.8:0.30-0.34:1.2-1.6:20-24:18-22; The mass concentration of the ethanol solution is 68-72%; The starch solution is prepared by mixing corn starch and deionized water, stirring evenly, raising the temperature to 63-66° C., and keeping the temperature for 0.8-1.2 hours; The mass ratio of the corn starch to deionized water is 8-12:62-67.

[0012] Compared with the prior art, the present invention has achieved the following beneficial effects: 1. The method for preparing NMN nano-microspheres of the present invention comprises the following steps: firstly, pre-treating NMN, using L-ascorbic acid and tea polyphenols as antioxidants to prevent NMN from being oxidized, thereby enhancing the stability of NMN; then, preparing NMN nano-microspheres by a three-step method, firstly, preparing primary microspheres, specifically, using natural high molecular weight polysaccharides as the skeleton material of the microspheres, combining ε-polylysine and glutathione, and under the action of an activator, cross-linking the carboxyl groups of ε-polylysine and glutathione with the amino groups of chitosan, thereby obtaining primary microspheres; then, cross-linking with the primary microspheres through the functionalization of konjac glucomannan, which can maintain a relatively stable form in gastric juice and intestinal juice, preventing the nano-microspheres from rapidly disintegrating in gastric juice, thereby achieving slow release. The sustained-release function is formed by combining sodium alginate and carrageenan to form a more stable network structure, and the adhesion of the functionalized microspheres is enhanced, which helps to form a stable and tight gel structure. It can act as a barrier in gastric juice and intestinal juice, not only blocking NMN from direct contact with light and oxygen, improving the stability of NMN itself, but also preventing the water in the digestive juice from quickly entering the interior of the nano-microspheres, slowing down the dissolution and release of the effective ingredients of NMN, thereby achieving better sustained-release performance; combined with the mixing step, polyvinyl pyrrolidone has good solubility and stability, microcrystalline cellulose can enhance the hardness and stability of the nano-microspheres, and the starch liquid has good adhesion and thickening effects. After drying and crushing processes, NMN nano-microspheres with high stability are finally prepared; 2. The NMN nanospheres prepared by the method of the present invention were irradiated by a 150W fluorescent lamp in a closed oxygen environment, the temperature was controlled at 26°C, the irradiation time was 24.0h, and the mass change rate was 0.54-0.61%; 3. The NMN nanoparticles prepared by the method of the present invention were digested in simulated gastric fluid for 2.0 h, and the NMN release rate was 0.54-0.58%; 4. The NMN nanoparticles prepared by the method of the present invention were digested in simulated gastric fluid for 2.0 h to obtain digestive fluid, 0.8 wt % NaOH solution was added to the digestive fluid, the pH was adjusted to 6.8, and the mixture was oscillated at 100 rpm for 12 h at 37 ° C. The release rate was 0 at the 0th hour of oscillation, the release rate was 8.7-10.4% at the 2nd hour of oscillation, the release rate was 20.4-23.1% at the 4th hour of oscillation, the release rate was 48.6-50.6% at the 8th hour of oscillation, and the release rate was 82.3-84.5% at the 12th hour of oscillation. DETAILED DESCRIPTION

[0013] In order to more clearly understand the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described.

[0014] Example 1 1. NMN pretreatment 8 g of NMN was added into 140 mL of anhydrous ethanol, stirred evenly, and then 0.14 g of L-ascorbic acid and 0.10 g of tea polyphenols were added. The temperature was raised to 32 °C and ultrasonic treatment was performed. The ultrasonic time was 26 min, the ultrasonic power was 110 W, and the ultrasonic frequency was 24 kHz. After the ultrasonic treatment, a pretreated NMN solution was obtained.

[0015] 2. Preparation of primary microspheres Add 4.5 g of chitosan to 95 g of 2.2 wt% acetic acid solution, stir evenly to obtain a chitosan solution; add 3.2 g of ε-polylysine and 2.2 g of glutathione to 95 g of 22 wt% ethanol solution, stir evenly, add 2.3 g of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and 2.5 g of N-hydroxysuccinimide, stir for 28 min to obtain a mixed solution; add 146 g of pretreated NMN solution to 34 g of chitosan solution, stir at 140 rpm for 18 min, add 26 g of the mixed solution, raise the temperature to 44 ° C, keep stirring for 3.2 h, filter, wash and dry to obtain primary microspheres.

[0016] 3. Preparation of Functionalized Microspheres 9.5 g of primary microspheres were added to 180 g of 30 wt% ethanol solution, and after stirring, 2.0 g of functional konjac glucomannan was added, and the mixture was kept warm at 36° C. for 3.2 h, and then 0.5 g of sodium alginate and 0.3 g of carrageenan were added. After stirring, the mixture was filtered, washed and dried to obtain functionalized microspheres. The preparation method of the functional konjac glucomannan is as follows: 4.8 g of konjac glucomannan is placed in 380 mL of deionized water, stirred and dissolved at 38° C., then 3.0 g of sodium periodate is added, reacted for 5.8 hours under light-proof conditions, then 0.8 mL of ethylene glycol is added to terminate the reaction, and the functional konjac glucomannan is obtained after drying.

[0017] 4. Mix 10.3 g of functionalized microspheres were mixed evenly with 0.30 g of polyvinyl pyrrolidone and 1.2 g of microcrystalline cellulose, and then added to 20 g of 68 wt% ethanol solution. After continuing to stir evenly, 18 g of starch solution was added for homogenization. The homogenization times were 2 times, the homogenization pressure was 5.8 MPa, and the homogenization time was 2.5 min each time. After the homogenization treatment was completed, it was filtered and washed, freeze-dried for 25 h, and crushed to obtain NMN nano-microspheres; The starch solution is prepared by mixing 8g corn starch with 62g deionized water, stirring evenly, raising the temperature to 63°C, and keeping the temperature for 1.2h.

[0018] Example 2 1. NMN pretreatment 12 g of NMN was added into 160 mL of anhydrous ethanol, stirred evenly, and then 0.16 g of L-ascorbic acid and 0.13 g of tea polyphenols were added. The temperature was raised to 38 °C and ultrasonic treatment was performed. The ultrasonic time was 35 min, the ultrasonic power was 130 W, and the ultrasonic frequency was 28 kHz. After the ultrasonic treatment, a pretreated NMN solution was obtained.

[0019] 2. Preparation of primary microspheres 5.5 g of chitosan was added to 106 g of 2.7 wt% acetic acid solution, and stirred to obtain a chitosan solution; 3.8 g of ε-polylysine and 2.7 g of glutathione were added to 105 g of 28 wt% ethanol solution, and stirred to obtain a mixed solution; 2.8 g of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and 3.0 g of N-hydroxysuccinimide were added, and stirred for 32 min to obtain a mixed solution; 155 g of pretreated NMN solution was added to 38 g of chitosan solution, and stirred at 160 rpm for 22 min, and then 30 g of the mixed solution was added, the temperature was raised to 50 ° C, and the mixture was stirred for 2.8 h. After filtering, washing, and drying, primary microspheres were obtained.

[0020] 3. Preparation of Functionalized Microspheres 10.4 g of primary microspheres were added to 220 g of 34 wt% ethanol solution, and after stirring, 2.3 g of functional konjac glucomannan was added, and the mixture was kept warm at 40° C. for 2.8 h, and then 0.8 g of sodium alginate and 0.5 g of carrageenan were added. After stirring, the mixture was filtered, washed and dried to obtain functionalized microspheres. The preparation method of the functional konjac glucomannan is as follows: 5.2 g of konjac glucomannan is placed in 420 mL of deionized water, stirred and dissolved at 42° C., then 3.4 g of sodium periodate is added, reacted for 6.2 h under light-proof conditions, then 1.2 mL of ethylene glycol is added to terminate the reaction, and the functional konjac glucomannan is obtained after drying.

[0021] 4. Mix 10.8 g of functionalized microspheres were mixed with 0.34 g of polyvinyl pyrrolidone and 1.6 g of microcrystalline cellulose, and then added to 24 g of 72 wt% ethanol solution. After stirring evenly, 22 g of starch solution was added for homogenization. The homogenization times were 2 times, the homogenization pressure was 6.3 MPa, and the homogenization time was 1.5 min each time. After the homogenization treatment was completed, it was filtered and washed, freeze-dried for 22 h, and crushed to obtain NMN nano-microspheres; The starch solution is prepared by mixing 12g corn starch and 67g deionized water, stirring evenly, raising the temperature to 66°C, and keeping the temperature for 0.8h.

[0022] Example 3 1. NMN pretreatment 10 g of NMN was added into 150 mL of anhydrous ethanol, stirred evenly, and then 0.15 g of L-ascorbic acid and 0.12 g of tea polyphenols were added. The temperature was raised to 35°C and ultrasonic treatment was performed. The ultrasonic time was 30 min, the ultrasonic power was 120 W, and the ultrasonic frequency was 26 kHz. After the ultrasonic treatment, a pretreated NMN solution was obtained.

[0023] 2. Preparation of primary microspheres 5.0 g of chitosan was added to 100 g of 2.5 wt% acetic acid solution, and stirred to obtain a chitosan solution; 3.5 g of ε-polylysine and 2.5 g of glutathione were added to 100 g of 25 wt% ethanol solution, and stirred to obtain a mixed solution; 2.5 g of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and 2.7 g of N-hydroxysuccinimide were added, and stirred for 30 min to obtain a mixed solution; 150 g of pretreated NMN solution was added to 36 g of chitosan solution, and stirred at 150 rpm for 20 min, and then 28 g of the mixed solution was added, the temperature was raised to 46 ° C, and the mixture was stirred for 3.0 h. After filtering, washing, and drying, primary microspheres were obtained.

[0024] 3. Preparation of Functionalized Microspheres 10.0 g of primary microspheres were added to 200 g of 32 wt% ethanol solution, and after stirring, 2.1 g of functional konjac glucomannan was added, and the mixture was kept warm at 38° C. for 3.0 h, and then 0.6 g of sodium alginate and 0.4 g of carrageenan were added. After stirring, the mixture was filtered, washed and dried to obtain functionalized microspheres. The preparation method of the functional konjac glucomannan is as follows: 5.0 g of konjac glucomannan is placed in 400 mL of deionized water, stirred and dissolved at 40° C., then 3.2 g of sodium periodate is added, reacted for 6.0 h under light-proof conditions, then 1.0 mL of ethylene glycol is added to terminate the reaction, and the functional konjac glucomannan is obtained after drying.

[0025] 4. Mix 10.5 g of functionalized microspheres were mixed with 0.32 g of polyvinyl pyrrolidone and 1.4 g of microcrystalline cellulose, and then added to 22 g of 70 wt% ethanol solution. After stirring evenly, 20 g of starch solution was added for homogenization. The homogenization times were 2 times, the homogenization pressure was 6.0 MPa, and the homogenization time was 2.0 min each time. After the homogenization treatment was completed, the mixture was filtered and washed, freeze-dried for 24 h, and crushed to obtain NMN nano-microspheres. The starch solution is prepared by mixing 10 g corn starch with 65 g deionized water, stirring evenly, raising the temperature to 65° C., and keeping the temperature for 1.0 h.

[0026] Example 3.1 1. Omit the NMN pretreatment step; 2. Omit the step of preparing primary microspheres; 3. Preparation of Functionalized Microspheres 10.0 g NMN was added to 200 g 32 wt% ethanol solution, and after stirring, 2.1 g functional konjac glucomannan was added, and the mixture was kept warm at 38 ° C for 3.0 h, and then 0.6 g sodium alginate and 0.4 g carrageenan were added. After stirring, the mixture was filtered, washed and dried to obtain functionalized microspheres. The preparation method of the functional konjac glucomannan is exactly the same as that in Example 3; 4. The mixing steps are exactly the same as in Example 3.

[0027] Example 3.2 1. The NMN pretreatment steps are exactly the same as those in Example 3; 2. The steps for preparing primary microspheres are exactly the same as those in Example 3; 3. Omit the step of preparing functionalized microspheres; 4. Mix 10.5 g of primary microspheres were mixed with 0.32 g of polyvinyl pyrrolidone and 1.4 g of microcrystalline cellulose, and then added to 22 g of 70 wt% ethanol solution. After stirring evenly, 20 g of starch solution was added for homogenization. The homogenization times were 2 times, the homogenization pressure was 4.0 MPa, and the homogenization time was 2.0 min each time. After the homogenization treatment was completed, it was filtered and washed, freeze-dried for 24 h, and crushed to obtain NMN nano-microspheres; The starch solution is prepared by mixing 10 g corn starch with 65 g deionized water, stirring evenly, raising the temperature to 65° C., and keeping the temperature for 1.0 h.

[0028] Example 4.1 The NMN nano-microspheres prepared in Examples 1-3, Example 3.1, and Example 3.2 were placed in a closed oxygen environment, respectively, and irradiated with a 150W fluorescent lamp, the temperature was controlled at 26°C, and the irradiation time was 24.0 h. After the irradiation treatment, the mass change rate of the NMN nano-microspheres was calculated, and the results are shown in Table 1:

[0029] Example 4.2 The preparation method of the simulated gastric fluid is as follows: 3.2 g of pepsin and 2.0 g of NaCl are added to 1 L of deionized water, and after complete dissolution, a 1.0 mol / L hydrochloric acid solution is added to adjust the pH value to 1.2; 1.0 g of the NMN nanoparticles prepared in Examples 1-3, Example 3.1, and Example 3.2 are added to 15 mL of simulated gastric fluid, respectively, and shaken at 37° C. and 100 rpm for 2.0 h to obtain a digestive fluid; the NMN release rate is recorded when the shaking is 2.0 h, and the recorded results are shown in Table 2:

[0030] 0.8wt% NaOH solution was added to the digestive fluid to adjust the pH to 6.8. The mixture was shaken at 100 rpm for 12 h at 37°C. The NMN release rates at 0, 2, 4, 8, and 12 h of shaking were recorded. The results are shown in Table 3:

[0031] The method for preparing NMN nano-microspheres of the present invention comprises the following steps: firstly, pre-treating NMN, using L-ascorbic acid and tea polyphenols as antioxidants to prevent NMN from being oxidized, thereby enhancing the stability of NMN; then, preparing NMN nano-microspheres by a three-step method, firstly, preparing primary microspheres, specifically, using natural high molecular weight polysaccharides as the skeleton material of the microspheres, combining ε-polylysine and glutathione, and under the action of an activator, cross-linking the carboxyl groups of ε-polylysine and glutathione with the amino groups of chitosan, thereby obtaining primary microspheres; then, cross-linking with the primary microspheres through the functionalization of konjac glucomannan, which can maintain a relatively stable form in gastric juice and intestinal juice, preventing the rapid disintegration of the nano-microspheres in gastric juice, thereby achieving sustained release Function, combined with sodium alginate and carrageenan to form a more stable network structure, and enhance the adhesion of the functionalized microspheres, which is helpful to form a stable and tight gel structure, which can act as a barrier in gastric juice and intestinal juice, not only blocking NMN from direct contact with light and oxygen, improving the self-stability of NMN, but also preventing the moisture of the digestive juice from quickly entering the interior of the nano-microspheres, slowing down the dissolution and release of the effective ingredients of NMN, thereby achieving better sustained-release performance; combined with the mixing step, polyvinyl pyrrolidone has good solubility and stability, microcrystalline cellulose can enhance the hardness and stability of the nano-microspheres, the starch liquid has good adhesion and thickening effect, and after drying and crushing processes, NMN nano-microspheres with high stability are finally obtained.

[0032] Example 3.1: NMN was directly used to prepare functionalized microspheres. NMN and functional konjac glucomannan, sodium alginate and carrageenan could not form a dense network structure, resulting in an unstable and unevenly distributed spatial network inside the functionalized microspheres. This resulted in a larger contact area with the simulated gastric fluid and a smoother channel for material diffusion, thereby accelerating the release rate of NMN. In addition, since NMN did not undergo a pretreatment step, its antioxidant effect was poor. Under light and oxygen conditions, NMN was easily oxidized and escaped from the reaction system, resulting in a large change in quality. Example 3.2 omits the step of preparing functionalized microspheres, and uses primary microspheres to prepare nanospheres, which lack functional konjac glucomannan, sodium alginate and carrageenan as a physical barrier protective layer, allowing gastric juice to penetrate into the microspheres faster and accelerate the release of NMN. In addition, under light and oxygen conditions, the NMN components encapsulated in the primary microspheres are more vulnerable to attack, resulting in oxidation and decomposition, reducing the stability of the NMN nanospheres.

[0033] Unless otherwise specified, all ratios and percentages described in the present invention are by mass ratios and percentages are by mass percentages.

[0034] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention is described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing NMN nanoparticles with high stability, characterized in that: It includes NMN pretreatment, preparation of primary microspheres, preparation of functionalized microspheres and mixing steps; The steps of preparing the primary microspheres are: adding ε-polylysine and glutathione to an ethanol solution, stirring evenly, adding 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide, stirring for 28-32 minutes, and obtaining a mixed solution; adding the pretreated NMN solution to the chitosan solution, and then adding the mixed solution, and keeping warm at 44-50° C. for 2.8-3.2 hours to obtain the primary microspheres; The steps of preparing the functionalized microspheres are as follows: adding the primary microspheres to the ethanol solution, stirring evenly, adding the functional konjac glucomannan, keeping the temperature at 36-40° C. for reaction for 2.8-3.2 hours, then adding sodium alginate and carrageenan, stirring evenly, filtering, washing and drying to obtain the functionalized microspheres.

2. The method for preparing NMN nanoparticles with high stability according to claim 1, characterized in that: In the step of preparing the primary microspheres, the chitosan solution is obtained by adding chitosan to an acetic acid solution and stirring evenly; The mass ratio of chitosan to acetic acid solution is 4.5-5.5:95-106; The mass concentration of the acetic acid solution is 2.2-2.7%.

3. The method for preparing NMN nanoparticles with high stability according to claim 1, characterized in that: In the step of preparing the primary microspheres, the mass ratio of the ε-polylysine, glutathione, ethanol solution, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide is 3.2-3.8:2.2-2.7:95-105:2.3-2.8:2.5-3.0; The mass concentration of the ethanol solution is 22-28%; The mass ratio of the pretreated NMN solution, the chitosan solution and the mixed solution is 146-155:34-38:26-30.

4. The method for preparing NMN nanoparticles with high stability according to claim 1, characterized in that: In the step of preparing functionalized microspheres, the mass ratio of the ethanol solution, the primary microspheres, the functional konjac glucomannan, the sodium alginate and the carrageenan is 180-220:9.5-10.4:2.0-2.3:0.5-0.8:0.3-0.5; The mass ratio of the ethanol solution is 30-34%.

5. The method for preparing NMN nanoparticles with high stability according to claim 1, characterized in that: In the step of preparing functionalized microspheres, the preparation method of the functional konjac glucomannan is as follows: placing the konjac glucomannan in deionized water, stirring and dissolving at 38-42° C., then adding sodium periodate, reacting for 5.8-6.2 hours under light-proof conditions, then adding ethylene glycol to terminate the reaction, and drying to obtain the functional konjac glucomannan; The mass volume ratio of the konjac glucomannan, deionized water, sodium periodate and ethylene glycol is 4.8-5.2 g: 380-420 mL: 3.0-3.4 g: 0.8-1.2 mL.

6. The method for preparing NMN nanoparticles with high stability according to claim 1, characterized in that: The NMN pretreatment step is to put NMN into anhydrous ethanol, stir evenly, add L-ascorbic acid and tea polyphenols, raise the temperature to 32-38°C, and perform ultrasonic treatment. The ultrasonic time is 26-35min, the ultrasonic power is 110-130W, and the ultrasonic frequency is 24-28kHz. After the ultrasonic treatment, a pretreated NMN solution is obtained; The mass volume ratio of the NMN, anhydrous ethanol, L-ascorbic acid and tea polyphenols is 8-12g:140-160mL:0.14-0.16g:0.10-0.13g.

7. The method for preparing NMN nanoparticles with high stability according to claim 1, characterized in that: The mixing step comprises: uniformly mixing the functionalized microspheres with polyvinyl pyrrolidone and microcrystalline cellulose, then adding them into the ethanol solution, continuing to stir evenly, adding the starch solution for homogenization, the homogenization times are 2 times, the homogenization pressure is 5.8-6.3 MPa, and the homogenization time for each time is 1.5-2.5 minutes. After the homogenization treatment is completed, after filtering and washing, freeze-drying for 22-25 hours, and crushing to obtain NMN nano-microspheres.

8. The method for preparing NMN nanoparticles with high stability according to claim 7, characterized in that: The mass ratio of the functionalized microspheres, polyvinyl pyrrolidone, microcrystalline cellulose, ethanol solution, and starch solution is 10.3-10.8:0.30-0.34:1.2-1.6:20-24:18-22; The mass concentration of the ethanol solution is 68-72%.

9. The method for preparing NMN nanoparticles with high stability according to claim 7, characterized in that: The starch solution is prepared by mixing corn starch and deionized water, stirring evenly, raising the temperature to 63-66° C., and keeping the temperature for 0.8-1.2 hours; The mass ratio of the corn starch to deionized water is 8-12:62-67.

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