Preparation method of selenium-enriched nanoparticles

Abstract

This invention discloses a method for preparing selenium-enriched nanoparticles. Selenium tetrachloride powder is uniformly dispersed in anhydrous ethanol, followed by the addition of vitamin C powder. The anhydrous ethanol solution containing selenium tetrachloride and vitamin C is homogenized using microfluidic jetting to prepare an anhydrous ethanol solution containing nanoscale particles. The reaction is then carried out under nitrogen protection with stirring. After the reaction is complete, low-ester pectin nanoparticles are dropwise added to the anhydrous ethanol solution containing the nanoscale particles under nitrogen protection and stirred. After the reaction is complete, the precipitate is obtained by filtration. The precipitate is washed with ethanol solutions of different gradients in descending order of concentration to obtain low-ester pectin nanoparticles with strong antioxidant capacity and rich in selenium elements of different valence states. This invention features a simple process, high selenium conversion rate, low energy consumption, environmental friendliness, low production cost, and short cycle time. The obtained selenium-enriched nanoparticles have strong antioxidant capacity and are rich in selenium elements of different valence states.

Description

Technical Field

[0001] This invention relates to a method for preparing selenium nanoparticles. Background Technology

[0002] Selenium is an essential trace element for the human body, possessing various bioactive functions. A certain amount of selenium intake daily helps maintain normal bodily functions and reduces the risk of disease. However, due to the extremely uneven distribution of selenium in the Earth's crust, the amount of selenium naturally accumulated by crops is generally insufficient. The Chinese Nutrition Society recommends a daily selenium intake of 50-200 μg per person. Currently, some people's daily selenium intake falls far short of this recommendation. Diseases caused by insufficient selenium intake pose a significant threat to human health, such as Kashin-Beck disease, Keshan disease, malignant tumors, and weakened immunity. Therefore, increasing selenium intake through supplements rich in selenium can address the problem of insufficient selenium intake and promote human health.

[0003] Selenium exists in nature in two main forms: inorganic selenium and organic selenium. Inorganic selenium is highly toxic and unsuitable for use as a nutritional fortifier. Compared to inorganic selenium, organic selenium has advantages such as lower toxicological safety risks, higher physiological activity, and higher absorption rates. Organic selenium is the ideal form for supplementing selenium. Converting inorganic selenium into organic selenium is currently a hot topic and a challenging area of ​​research in the industry.

[0004] There are currently numerous reports on the preparation of organic selenium from inorganic selenium.

[0005] Analysis reveals that reported methods for converting inorganic selenium into organic selenium primarily use inorganic sodium selenite as a raw material, transforming it into organic selenium through methods such as encapsulation, complexation, and biotransformation.

[0006] For example, patent number 111759822A discloses a nano-selenium-zein composite nanoparticle comprising elemental selenium and zein coated with elemental selenium. Its preparation method includes the following steps: (1) pouring sodium selenite solution into a zein solution and mixing evenly; (2) adding ascorbic acid to the solution obtained in step (1), and stirring or ultrasonically treating to obtain nano-selenium-zein composite nanoparticles. This is the first time that zein has been used to prepare nano-selenium particles. The prepared nano-selenium composite particles have the advantages of good pH response and controllable particle size, solving the problem of relatively simple nano-selenium particles and limited application scenarios in the prior art. This patent discloses a selenium-zein composite nanoparticle, in which selenium is elemental selenium in a zero oxidation state. Elemental selenium is obtained by using sodium selenite in an aqueous solution as a raw material, and ascorbic acid as a reducing agent to reduce iron selenium oxide to elemental selenium, which is then adsorbed into zein to prevent the oxidation of elemental selenium. This method still uses selenite as a raw material to encapsulate elemental selenium to prepare selenium nanoparticles. It suffers from the drawback of low selenium loading. Furthermore, elemental selenium is essentially inorganic selenium and has high toxicity. In addition, the entire reaction process is carried out in a solution containing a mixture of water and ethanol, using water as a medium, which has the disadvantages of conventional organic selenium preparation methods. The selenium enrichment method disclosed in this patent introduces zein, increasing the risk of protein sensitization during the use of nano-selenium.

[0007] In summary, existing methods all involve using aqueous solutions as a medium and supplementing them with strong acids, strong alkalis, or organic macromolecule encapsulation to convert inorganic selenium into organic selenium. These methods suffer from low selenium conversion rates, high energy consumption, and significant environmental pollution risks, and cannot meet the needs of a green, energy-saving, and environmentally friendly organic selenium industry. Summary of the Invention

[0008] The purpose of this invention is to solve the above-mentioned technical problems and provide a method for preparing selenium-enriched nanoparticles that is simple in process, has a high selenium conversion rate, low energy consumption, is environmentally friendly, has low production cost, and a short cycle. The resulting selenium-enriched nanoparticles have strong antioxidant capacity and are rich in selenium elements of different valence states.

[0009] The preparation method of the selenium-enriched nanoparticles of the present invention is as follows: selenium tetrachloride powder is uniformly dispersed in anhydrous ethanol, vitamin C powder is added, and the anhydrous ethanol solution containing selenium tetrachloride and vitamin C is homogenized by microfluidic jet to prepare an anhydrous ethanol solution containing nano-sized particles, and the reaction is carried out under nitrogen protection.

[0010] After the reaction was completed, under nitrogen protection, the low-ester pectin nanoparticles were dropped into an anhydrous ethanol solution of the nanoparticles and stirred. After the reaction was completed, the precipitate was filtered and washed with ethanol solutions of different gradients in order of concentration from high to low to obtain low-ester pectin nanoparticles with strong antioxidant capacity and rich in selenium elements of different valence states.

[0011] The content of selenium tetrachloride in the anhydrous ethanol solution is controlled to be 6-12 mg / 100g.

[0012] The vitamin C content in the anhydrous ethanol solution is controlled to be 0.7–1.4 g / 100 g.

[0013] The particle size range of the nanoparticles in the anhydrous ethanol solution containing nanoparticles is controlled to be between 40 and 75 nm.

[0014] The stirring reaction time of the anhydrous ethanol solution containing nano-sized particles under nitrogen protection was controlled to be 1-2 hours, and the stirring speed was 260-460 r / min.

[0015] The low-ester pectin nanoparticles contain low-ester pectin with a degree of esterification of 10–25% and a molecular weight of 0.9 × 10⁻⁶. 5 ~1.4×10 5 The particle size is between 400 and 800 nm.

[0016] The content of low-ester pectin nanoparticles in the anhydrous ethanol solution of the nanoparticles is controlled to be 1.5 g / 100 g.

[0017] The low-ester pectin nanoparticles were added dropwise to the anhydrous ethanol solution of the nanoparticles and the reaction was continued with stirring for 1 hour.

[0018] The washing concentrations of the ethanol solutions, from highest to lowest, were 97%, 94%, 91%, 88%, 85%, 83%, and 80%.

[0019] To address the problems existing in the background technology, the inventors abandoned the conventional method of preparing organic selenium using aqueous solution as a medium and sodium selenite as a raw material. Instead, they adopted a method combining nanoparticles and microfluidic homogenization technology. Using selenium chloride as the source of selenium, low-ester pectin nanoparticles as a carrier, anhydrous ethanol as a medium, and vitamin C as a selenium valence state regulator, the tetravalent selenium element in inorganic selenium chloride was converted into divalent selenium element and then transferred to low-ester pectin nanoparticles through ion exchange to prepare organic selenium nanoparticles with low-ester pectin as a carrier. This achieved the conversion of inorganic selenium to organic selenium and endowed the low-ester pectin nanoparticles with strong antioxidant capacity.

[0020] This invention regulates the valence state of selenium in low-ester pectin nanoparticles by adjusting the amount of vitamin C added, thereby regulating the antioxidant capacity of the low-ester pectin nanoparticles. Moreover, the selenium-rich low-ester pectin nanoparticles belong to the category of organic polysaccharides and have no risk of "protein sensitization", making them an ideal raw material for studying the physiological activity of selenium.

[0021] Specifically, selenium tetrachloride is an inorganic powdery selenium-containing substance that is insoluble in ethanol. Therefore, it needs to be prepared into nanoparticles and suspended in an ethanol solution through microfluidic processing to increase the contact area between selenium ions and vitamin C, thereby changing the valence state of selenium. Furthermore, this treatment can also increase the selenium ion loading in the low-ester pectin nanoparticles. The amount of selenium tetrachloride added to anhydrous ethanol is between 6 and 12 mg / 100g, and the amount of vitamin C powder added is between 0.7 and 1.4 g / 100g. Too low a concentration of selenium tetrachloride is detrimental to the selenium ion loading in the low-ester pectin nanoparticles, while too high a concentration results in incomplete selenium loading, poses safety hazards, and is not conducive to microfluidic operation. Ultimately, the particle size of the selenium tetrachloride nanoparticles in ethanol is controlled between 40 and 75 nm.

[0022] In a further preferred embodiment, in order to enhance the contact between selenium and vitamin C and thus reduce some tetravalent selenium to divalent selenium, after homogenizing the anhydrous ethanol solution containing selenium tetrachloride and vitamin C using microfluidic jet, the mixture is stirred for 2 hours under nitrogen protection to further improve the reaction efficiency.

[0023] In this invention, it was discovered that when the degree of esterification of low-ester pectin is 10–25% and the molecular weight is controlled between 0.9 × 10⁵ and 1.4 × 10⁵, nanoparticles can be formed, which possess hydrophobic cavities. When these nanoparticles are added to anhydrous ethanol containing selenium in different valence states, the selenium ions of different valence states exchange with cations on the micelle surface, adsorbing selenium atoms into the structure of the low-ester pectin nanoparticles, thus achieving selenium ion loading. Ethanol, being a non-polar liquid, disrupts the force balance system maintaining the low-ester pectin nanoparticles, thereby exposing the hydrophobic groups in the nanoparticle cavities, which in turn destroys the nanoparticle structure and forms new nanoparticles. The outer surface of the new nanoparticles is covered with a large number of hydrophobic groups, thus preventing the re-exchange of selenium ions with other cations within the pectin nanoparticles.

[0024] Preferably, the amount of low-ester pectin nanoparticles added is 1.5g / 100g. Adding too much will result in too low selenium loading in the low-ester pectin nanoparticles, while adding too little will result in waste of inorganic selenium.

[0025] By controlling the washing concentration of the ethanol solution from high to low, the aim is to remove inorganic selenium and unloaded selenium low-ester pectin nanoparticles.

[0026] The microfluidic jet described in this invention refers to homogenization under ultra-high pressure conditions using a microfluidic high-pressure homogenizing device, with the control conditions being commonly used high-pressure homogenization conditions.

[0027] Beneficial effects: This invention directly uses tetravalent inorganic selenium as the source of selenium. By controlling the ratio of selenium tetrachloride, vitamin C, and sodium-rich low-ester pectin nanoparticles, the valence state of selenium, the conversion rate of organic selenium, and its antioxidant capacity are regulated. The preparation process does not involve the use of highly corrosive materials and does not require heat treatment. The process is simple, has low production cost, is green and environmentally friendly, and is easy to operate. It solves the problem of converting inorganic selenium to organic selenium while also allowing for adjustment of its antioxidant capacity and the content of selenium with different valence states as needed. This provides material for further research on the physiological effects of organic selenium and promotes the expansion of the application scope of organic selenium. Detailed Implementation

[0028] Example 1

[0029] Selenium tetrachloride was dispersed in anhydrous ethanol to prepare a solution of 12 mg / 100 g, and then vitamin C powder was added to make the vitamin C content 1.40 g / 100 g. The above mixed solution was homogenized using a microfluidic high-pressure homogenizer, and the particle size of the nanoparticles in the homogenized ethanol solution was 40-60 nm. Nitrogen gas was continuously introduced as a protective gas, and the solution was stirred for 2 h at 300 rpm. A solution with an esterification degree of 14 ± 4% and a molecular weight of (1.2-1.4) × 10⁻⁶ was added dropwise. 5 Low-ester pectin nanoparticles with a g / mol content and a particle size range of 600–800 nm were stirred for 1 hour at room temperature under nitrogen protection and then filtered to obtain a precipitate.

[0030] The precipitate was washed with ethanol solutions of different concentrations in descending order of concentration: 97%, 94%, 91%, 88%, 85%, 83%, and 80% (volume ratio). After washing, nanoparticles containing selenium in different valence states were collected. The yield of selenium-rich nanoparticles was determined to be 85.41%, with a total selenium content of 9.28 mg / kg. Divalent selenium accounted for 57.14% of the total selenium content. The ABTS free radical scavenging rate was 69.10%, the DPPH free radical scavenging rate was 79.12%, and the hemolysis rate was reduced by 80.65%.

[0031] Example 2

[0032] Unlike Example 1:

[0033] The amount of vitamin C powder used was 1.1g / 100g. After microfluidic homogenization, the particle size range in anhydrous ethanol was 50-70nm. The yield of selenium-rich nanoparticles was determined to be 83.59%, with a total selenium content of 9.17mg / kg, of which divalent selenium accounted for 49.91%. The ABTS free radical scavenging rate was 55.56%, the DPPH free radical scavenging rate was 71.34%, and the hemolysis rate of blood cells was reduced by 75.17%.

[0034] Example 3

[0035] Unlike Example 1:

[0036] The amount of vitamin C powder used was 0.7g / 100g. After microfluidic homogenization, the particle size range in anhydrous ethanol was 55-75nm. The yield of selenium-rich nanoparticles was determined to be 82.16%, with a total selenium content of 9.20mg / kg, of which divalent selenium accounted for 43.15%. The ABTS free radical scavenging rate was 47.33%, the DPPH free radical scavenging rate was 66.46%, and the hemolysis rate of blood cells was reduced by 69.18%.

[0037] Example 4

[0038] Unlike Example 1:

[0039] The low-ester pectin nanoparticles used have a degree of esterification of 22±3% and a molecular weight of (1.0~1.2)×10⁻⁶. 5 The nanoparticles, with a g / mol content and a particle size range of 500–700 nm, were found to have a selenium-rich nanoparticle yield of 79.66% and a total selenium content of 9.19 mg / kg. Divalent selenium accounted for 55.65% of the total selenium content. The nanoparticles exhibited an ABTS free radical scavenging rate of 66.40%, a DPPH free radical scavenging rate of 78.15%, and a 79.46% reduction in hemolysis rate.

[0040] Example 5

[0041] The difference from Example 4 is:

[0042] The low-ester pectin nanoparticles used have a low-ester pectin molecular weight of (0.9~1.0)×10⁻⁶. 5 The nanoparticles, with a g / mol content and a particle size range of 400–500 nm, were found to have a selenium-rich nanoparticle yield of 78.91% and a total selenium content of 8.83 mg / kg. Divalent selenium accounted for 56.14% of the total selenium content. The nanoparticles exhibited an ABTS free radical scavenging rate of 67.96%, a DPPH free radical scavenging rate of 77.43%, and a 79.55% reduction in hemolysis rate.

[0043] Example 6

[0044] Unlike Example 1:

[0045] The concentration of selenium tetrachloride was 9.00 mg%. The yield of selenium-rich nanoparticles was determined to be 77.41%, the total selenium content in the particles was 7.93 mg / kg, of which divalent selenium accounted for 65.14%. The ABTS free radical scavenging rate was 71.55%, the DPPH free radical scavenging rate was 83.44%, and the hemolysis rate of blood cells was reduced by 85.92%.

[0046] Example 7

[0047] The difference from Example 6 is:

[0048] The dosage of vitamin C was 1.1 g / 100 g. After microfluidic homogenization, the particle size range of the nanoparticles in anhydrous ethanol was 50–70 nm. The yield of selenium-rich nanoparticles was determined to be 72.17%, with a total selenium content of 7.83 mg / kg, of which divalent selenium accounted for 44.48%. The ABTS free radical scavenging rate was 55.17%, the DPPH free radical scavenging rate was 62.43%, and the hemolysis rate of blood cells was reduced by 69.54%.

[0049] Example 8

[0050] The difference from Example 6 is:

[0051] The dosage of vitamin C was 0.7 g / 100 g. After microfluidic homogenization, the particle size range of nanoparticles in anhydrous ethanol was 55–75 nm. The yield of selenium-rich nanoparticles was determined to be 71.96%, with a total selenium content of 7.75 mg / kg, of which divalent selenium accounted for 38.15%. The ABTS free radical scavenging rate was 45.66%, the DPPH free radical scavenging rate was 53.27%, and the hemolysis rate of blood cells decreased by 58.26%.

[0052] Example 9

[0053] The difference from Example 6 is:

[0054] The low-ester pectin nanoparticles used have a degree of esterification of 22±3% and a molecular weight of (1.0~1.2)×10⁻⁶. 5 The nanoparticles, with a g / mol content and a particle size range of 500–700 nm, were found to have a selenium-rich nanoparticle yield of 75.35% and a total selenium content of 7.45 mg / kg. Divalent selenium accounted for 55.93% of the total selenium content. The nanoparticles exhibited an ABTS free radical scavenging rate of 64.72%, a DPPH free radical scavenging rate of 66.59%, and a 70.18% reduction in hemolysis rate.

[0055] Example 10

[0056] The difference from Example 9 is:

[0057] The low-ester pectin nanoparticles used have a molecular weight of (0.9~1.0)×10⁻⁶. 5 The nanoparticles, with a g / mol content and a particle size range of 400–500 nm, were found to have a selenium-rich nanoparticle yield of 74.69% and a total selenium content of 7.34 mg / kg. Divalent selenium accounted for 53.19% of the total selenium content. The nanoparticles exhibited an ABTS free radical scavenging rate of 62.15%, a DPPH free radical scavenging rate of 65.94%, and a 68.77% reduction in hemolysis rate.

[0058] Example 11

[0059] Unlike Example 1:

[0060] The concentration of selenium tetrachloride was 6.00 mg / 100g. The yield of selenium-rich nanoparticles was determined to be 67.18%, with a total selenium content of 6.55 mg / kg, of which divalent selenium accounted for 68.98%. The ABTS free radical scavenging rate was 55.43%, the DPPH free radical scavenging rate was 65.77%, and the hemolysis rate of blood cells was reduced by 69.88%.

[0061] Example 12

[0062] The difference from Example 11 is:

[0063] The dosage of vitamin C was 1.1 g / 100 g. After microfluidic homogenization, the particle size range of the nanoparticles in anhydrous ethanol was 50–70 nm. The yield of selenium-rich nanoparticles was determined to be 65.84%, with a total selenium content of 6.53 mg / kg, of which divalent selenium accounted for 45.16%. The ABTS free radical scavenging rate was 50.17%, the DPPH free radical scavenging rate was 52.43%, and the hemolysis rate of blood cells was reduced by 55.16%.

[0064] Example 13

[0065] The difference from Example 12 is:

[0066] The dosage of vitamin C was 0.7 g / 100 g. After microfluidic homogenization, the particle size range of the nanoparticles in anhydrous ethanol was 55–75 nm. The yield of selenium-rich nanoparticles was determined to be 61.76%, with a total selenium content of 6.35 mg / kg, of which divalent selenium accounted for 33.57%. The ABTS free radical scavenging rate was 42.62%, the DPPH free radical scavenging rate was 49.18%, and the hemolysis rate of blood cells was reduced by 50.60%.

[0067] Example 14

[0068] The difference from Example 11 is:

[0069] The low-ester pectin nanoparticles used have a degree of esterification of 22±3% and a molecular weight of (1.0~1.2)×10⁻⁶. 5 The nanoparticles, with a g / mol content and a particle size range of 500–700 nm, were found to have a selenium-rich nanoparticle yield of 65.35%, a total selenium content of 5.45 mg / kg, of which divalent selenium accounted for 63.93%. The nanoparticles exhibited an ABTS free radical scavenging rate of 44.72%, a DPPH free radical scavenging rate of 56.30%, and a 53.17% reduction in hemolysis rate.

[0070] Example 15

[0071] The difference from Example 14 is:

[0072] The low-ester pectin nanoparticles used have a low-ester pectin molecular weight of (0.9~1.0)×10⁻⁶. 5 The nanoparticles, with a g / mol content and a particle size range of 400–500 nm, were found to have a selenium-rich nanoparticle yield of 64.70% and a total selenium content of 5.54 mg / kg. Divalent selenium accounted for 52.82% of the total selenium content. The nanoparticles exhibited an ABTS free radical scavenging rate of 42.15%, a DPPH free radical scavenging rate of 53.67%, and a 57.43% reduction in hemolysis rate.

[0073] Comparative Example 1

[0074] Unlike Example 1, no vitamin C powder was added. The yield of selenium-rich nanoparticles was determined to be 47%, the total selenium content in the particles was 4.14 mg / kg, and no divalent selenium was found. The ABTS free radical scavenging rate was 1.19%, the DPPH free radical scavenging rate was 3.87%, and the hemolysis rate of blood cells showed virtually no decrease.

[0075] Comparative Example 2

[0076] The difference from Example 1 is that: an esterification degree of 30±3% and a molecular weight of (0.5~0.8)×10 were used. 5 Nanoparticles prepared from low-ester pectin (g / mol) were used as carriers of organic selenium. The yield of selenium-rich nanoparticles was determined to be 43.17%, with a total selenium content of 2.33 mg / kg. Of this, divalent selenium accounted for only 5.11%. The ABTS free radical scavenging rate was 1.34%, the DPPH free radical scavenging rate was 1.99%, and the hemolysis rate of blood cells showed virtually no decrease.

[0077] Comparative Example 3

[0078] Unlike Comparative Example 2, an anhydrous ethanol solution rich in selenium tetrachloride and vitamin C powder was homogenized into nanoparticles with a particle size range of 200–300 nm. The yield of selenium-rich nanoparticles was determined to be 32.52%, with a total selenium content of 1.77 mg / kg. Of this, divalent selenium accounted for only 3.48%. The ABTS free radical scavenging rate was 1.19%, the DPPH free radical scavenging rate was 1.79%, and the hemolysis rate of blood cells showed virtually no decrease.

[0079] The above embodiments are merely examples. Those skilled in the art can adjust the dosage of selenium tetrachloride and vitamin C, as well as the degree of esterification, molecular weight, and particle size range of the low-ester pectin used to prepare low-ester pectin nanoparticles, based on the principles and control conditions described in this invention, to obtain selenium-enriched nanoparticles with different yields, different antioxidant capacities, and controllable hemolysis rates.

Claims

1. A method for preparing selenium-rich nanoparticles, characterized in that, after uniformly dispersing selenium tetrachloride powder in anhydrous ethanol, vitamin C powder is added, the anhydrous ethanol solution containing selenium tetrachloride and vitamin C is subjected to homogenization treatment by micro-flow shooting to prepare an anhydrous ethanol solution containing nanoscale particles, and stirring reaction is carried out under nitrogen protection; the content of selenium tetrachloride in the anhydrous ethanol solution is controlled to be 6-12 mg / 100 g, and the content of vitamin C is controlled to be 0.7-1.4 g / 100 g; After the reaction is completed, the low-ester pectin nanoparticles are dropped into the anhydrous ethanol solution containing the nanoscale particles under nitrogen protection and stirred to react, and after the reaction is completed, the precipitate is obtained by filtration, and the precipitate is washed with different gradient ethanol solutions in the order of high to low concentration to obtain low-ester pectin nanoparticles with strong antioxidant capacity and rich in selenium elements of different valence states; the degree of esterification of the low-ester pectin in the low-ester pectin nanoparticles is 10-25%, the molecular weight is 0.9×10 5 ~1.4×10 5 , and the particle size is between 400-800 nm.

2. The method for preparing selenium-enriched nanoparticles as described in claim 1, characterized in that, the particle size of the nanoparticles in the anhydrous ethanol solution containing nanoscale particles is controlled to be in the range of 40-75 nm.

3. The method for preparing selenium-rich nanoparticles according to claim 1 or 2, wherein, the stirring reaction time of the anhydrous ethanol solution containing nanoscale particles under nitrogen protection is controlled to be 1-2 hours, and the stirring speed is controlled to be 260-460 r / min.

4. The method for preparing selenium-enriched nanoparticles as described in claim 1, characterized in that, the content of low-ester pectin nanoparticles in the anhydrous ethanol solution containing nanoscale particles is controlled to be 1.5 g / 100 g.

5. The method for preparing selenium-enriched nanoparticles as described in claim 1, characterized in that, after the low-ester pectin nanoparticles are dropped into the anhydrous ethanol solution containing nanoscale particles, stirring reaction is continued for 1 hour.

6. The method for preparing selenium-enriched nanoparticles as described in claim 1, characterized in that, the washing concentration sequence of the ethanol solution from high to low is 97%, 94%, 91%, 88%, 85%, 83% and 80% respectively.