Application of selenium-rich composition in medicine for preventing bone marrow suppression of dogs after chemotherapy

Abstract

The invention relates to the technical field of veterinary chemical drugs, and provides an application of a selenium-rich composition in a drug for preventing bone marrow suppression after chemotherapy of dogs, and the selenium-rich composition comprises nano-selenium-beta-glucan chelate and L-selenium-methyl selenocysteine, the mass ratio of the nano-selenium-beta-glucan chelate to the L-selenium-methyl selenocysteine is 1: (0.3-0.6), and the mass ratio of the nano-selenium-beta-glucan chelate to the L-selenium-methyl The molar ratio of the astragaloside IV to the cobamamide is (5 to 8): 1. Through the synergistic effect of the nano-selenium-beta-glucan chelate and the L-selenium-methyl selenocysteine and in combination with the loading technology of the silicon dioxide mesoporous carrier, the absorption rate of selenium is greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of veterinary chemical drugs, and specifically, to the application of a selenium-rich composition in a drug for preventing myelosuppression after chemotherapy in dogs. Background Art

[0002] At present, in the treatment of canine tumors, although the use of chemotherapy drugs can significantly relieve tumor symptoms, the myelosuppression problem caused by them severely limits the treatment effect and safety. Data shows that the incidence of myelosuppression in dogs after chemotherapy is as high as 65 - 80%. This complication not only seriously affects the quality of life of patients, but may even increase the risk of infection due to granulocytopenia, thereby endangering life;

[0003] Among the existing treatment methods, although conventional methods such as recombinant granulocyte colony-stimulating factor have certain curative effects, there are significant problems such as immunogenic risk and induction of tolerance, which are difficult to meet clinical needs. In addition, selenium, as an important trace element, has a unique role in anti-tumor, antioxidant and immune enhancement, and has been widely used in the field of chemotherapy adjuvant treatment. However, currently available selenium supplements generally have the problem of low bioavailability (the conversion rate of inorganic selenium is less than 30%), and lack targeted design for the canine bone marrow microenvironment. In view of this, the present invention proposes the application of a selenium-rich composition in a drug for preventing myelosuppression after chemotherapy in dogs. Summary of the Invention

[0004] The present invention proposes the application of a selenium-rich composition in a drug for preventing myelosuppression after chemotherapy in dogs, and solves the problem of low bioavailability of selenium supplements in the prior art.

[0005] The technical solution of the present invention is as follows: the application of a selenium-rich composition in a drug for preventing myelosuppression after chemotherapy in dogs, wherein the selenium-rich composition comprises:

[0006] Nanoselenium-β-glucan chelate and L-selenomethylselenocysteine, and the mass ratio of the nanoselenium-β-glucan chelate to L-selenomethylselenocysteine is 1:(0.3 - 0.6);

[0007] Astragaloside IV and cobamamide, and the molar ratio of astragaloside IV to cobamamide is (5 - 8):1.

[0008] Preferably, the selenium-rich composition uses silica mesoporous nanoparticles as a mesoporous carrier, and the pore diameter of the silica mesoporous particles is 4 - 6 nm.

[0009] Preferably, the selenium-rich composition is in the form of oral pellets, and the dosing dose is 0.5 - 1.5 mg Se / kg / day, and it is fed within 24 hours before and after chemotherapy.

[0010] Preferably, the selenium-rich composition adopts a thermosensitive-enteric double-controlled release coating:

[0011] The outer enteric coating material is L100-55, with a thickness of 15-20 μm;

[0012] The inner layer is thermosensitive hydroxypropyl methylcellulose, and its lower critical solution temperature is 34 °C.

[0013] Preferably, the specific implementation process of the thermosensitive-enteric double-controlled release coating of the selenium-rich composition is as follows:

[0014] A1. Mix the nano-selenium-β-glucan chelate and L-seleno-methylselenocysteine according to the mass ratio, and then add astragaloside IV and cobamamide according to the molar ratio and dissolve them in a pH 7.0 phosphate buffer solution to obtain a drug solution;

[0015] A2. Immerse the mesoporous carrier and the drug solution in a ratio of 1:3 (w / v), and then load them by ultrasonic assistance;

[0016] A3. Centrifuge and separate, vacuum dry at 50 °C, and screen to obtain the drug-loaded pellets;

[0017] A4. Disperse hydroxypropyl methylcellulose and PEG6000 in pure water according to the ratio, and stir at 50 °C until completely dissolved to obtain a thermosensitive coating solution;

[0018] A5. The thermosensitive coating solution forms a thermosensitive layer on the surface of the drug-loaded pellets through a fluidized bed. Among them, the inlet air temperature is 40 °C, the spraying rate is 3-5 mL / min, the atomization pressure is 0.8-1.2 bar, and hot air circulation drying is carried out at 40 °C for 2 hours to form a continuous thermosensitive film;

[0019] A6. Mix L100-55 and TEC are dissolved in an ethanol-water mixed solvent according to the ratio, and magnetically stirred until transparent to obtain an enteric coating solution;

[0020] A7. The enteric coating solution forms an enteric layer on the surface of the thermosensitive film of the pellets through a fluidized bed, and is dried at 45 °C for 4 hours to completely form the enteric film, and the qualified pellets are screened and sorted.

[0021] Preferably, the preparation process of the nano-selenium-β-glucan chelate is as follows:

[0022] B1. Dissolve β-glucan in deionized water to prepare a 2-4% (w / v) β-glucan solution, heat to 50-60 °C and stir until completely dissolved, and filter to remove impurities;

[0023] B2. Dissolve sodium selenite in deionized water, stir and mix to prepare a 0.1-0.3 mol / L sodium selenite solution;

[0024] B3. Add the β-glucan solution and sodium selenite solution into a reaction kettle protected from light and under nitrogen protection, and stir and mix them.

[0025] B4. Add vitamin C into the reaction kettle in three portions, with an interval of 10 minutes each time, and adjust the pH to 6.8 - 7.2.

[0026] B5. Under nitrogen protection, react the mixed solution in an ultrasonic reactor with an ultrasonic power density of 35 - 40 W / cm 2 for 2 - 4 hours.

[0027] B6. After the reaction is completed, centrifuge at 8000 - 10000 rpm for 15 minutes to remove the unreacted precipitate. The supernatant is filtered through a 0.22 - μm filter membrane to obtain a nano - selenium - β - glucan chelate colloidal solution, and then continue freeze - drying to obtain nano - selenium - β - glucan chelate powder.

[0028] Preferably, in the preparation process of the nano - selenium - β - glucan chelate: the volume percentage of the β - glucan solution in the mixed solution is 60 - 70%, and the molar ratio of sodium selenite solution to vitamin C is 1:5.

[0029] Preferably, the preparation process of the L - seleno - methylselenocysteine is as follows:

[0030] C1. Inoculate the preserved yeast strain Se - 18 into a selenium - containing culture medium and ferment at 30°C and pH 6.5 for 48 hours.

[0031] C2. Collect the thallus by centrifugation, wash it and then break the cells.

[0032] C3. Mix the broken solution with L - cysteine and a methyl donor, and react in a 37°C and pH 7.4 buffer system for 6 - 8 hours.

[0033] C4. Promote the methylation of selenocysteine by genetically engineering the yeast metabolic pathway.

[0034] C5. Separate L - seleno - methylselenocysteine by ion - exchange chromatography and reverse - phase HPLC.

[0035] C6. Obtain high - purity L - seleno - methylselenocysteine crystals after freeze - drying.

[0036] Preferably, in the preparation process of the L - seleno - methylselenocysteine: the genetic engineering regulation of the yeast metabolic pathway is achieved by overexpressing cystathionine β - synthase CBS and methyltransferase.

[0037] Preferably, the efficacy of the selenium - rich composition is verified by the following method:

[0038] (1) Detect canine bone marrow CD34 and cell viability by flow cytometry, with a processing time ≤ 2 hours;

[0039] (2) Replace the selenium in the selenium-rich composition with 75 Se isotope to track the metabolism of the drug in dogs in real time.

[0040] The working principle and beneficial effects of the present invention are as follows:

[0041] 1. Through the synergistic effect of nano-selenium-β-glucan chelate and L-seleno-methylselenocysteine in the composition of the present invention, combined with the loading technology of silica mesoporous carrier, the absorption rate of selenium is increased to 85.4% (only 71.6% for traditional inorganic selenium), and bone marrow targeted delivery is achieved, reducing the burden on the liver and kidneys (the urine excretion rate is only 5.2%);

[0042] 2. The composition of the present invention adopts thermosensitive-enteric double coating to ensure drug release in the intestinal pH environment. While ensuring precise drug release in the ileum, it avoids damage to the gastric mucosa by irritating components. At the same time, the thermosensitive layer responds to body temperature to trigger controlled release, prolonging the action time and maintaining a stable blood selenium concentration for 48 hours, ensuring an extended continuous action time of the drug in the body, thereby achieving a better therapeutic effect;

[0043] 3. The composition of the present invention can simultaneously regulate the NF-κB and Notch signaling pathways, effectively inhibit the overexpression of pro-inflammatory factors (such as IL-6, TNF-α), reduce the damage of inflammatory response to hematopoietic stem cells, and at the same time promote the repair of the hematopoietic microenvironment, enhancing the + number and activity of CD34

[0044] 4. Astragaloside IV and cobamamide in the composition of the present invention promote the proliferation of CD34+ hematopoietic stem cells and inhibit apoptosis by regulating the bone marrow microenvironment. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0046] Figure 1 It is a schematic diagram of the plasma selenium content of each group at different time periods in Experimental Test Example 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0047] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of the present invention.

[0048] Example 1:

[0049] This example presents the application of a selenium-rich composition in a drug for preventing myelosuppression in dogs after chemotherapy. The selenium-rich composition contains:

[0050] Nanoselenium-β-glucan chelate and L-selenomethylselenocysteine, and the mass ratio of nanoselenium-β-glucan chelate to L-selenomethylselenocysteine is 1:0.3;

[0051] Astragaloside IV and cobamamide, and the molar ratio of astragaloside IV to cobamamide is 5:1.

[0052] Among them, the selenium-rich composition uses silica mesoporous nanoparticles as a mesoporous carrier, and the pore diameter of the silica mesoporous particles is 4 nm.

[0053] Among them, the selenium-rich composition is in the form of oral pellets, and the dosing dose is 0.5 Se / kg / day, and it is fed within 24 hours before and after chemotherapy.

[0054] Among them, the selenium-rich composition uses a temperature-sensitive - enteric double-controlled release coating: the outer enteric coating material is L100-55, with a thickness of 15 μm; the inner layer is temperature-sensitive hydroxypropyl methylcellulose, and its lower critical solution temperature (LCST) is 34 °C.

[0055] Through the synergistic effect of nanoselenium-β-glucan chelate and L-selenomethylselenocysteine, combined with the loading technology of the silica mesoporous carrier, the absorption rate of selenium is increased, and bone marrow targeted delivery is achieved, reducing the burden on the liver and kidneys.

[0056] Example 2:

[0057] This example presents the application of a selenium-rich composition in a drug for preventing myelosuppression in dogs after chemotherapy. The selenium-rich composition contains:

[0058] Nanoselenium-β-glucan chelate and L-selenomethylselenocysteine, and the mass ratio of nanoselenium-β-glucan chelate to L-selenomethylselenocysteine is 1:0.5;

[0059] Astragaloside IV and cobamamide, and the molar ratio of astragaloside IV to cobamamide is 6:1.

[0060] Among them, the selenium-rich composition uses silica mesoporous nanoparticles as a mesoporous carrier, and the pore diameter of the silica mesoporous particles is 5 nm.

[0061] Among them, the selenium-rich composition is in the form of oral pellets, and the dosing dose is 1 mg Se / kg / day, and it is fed within 24 hours before and after chemotherapy.

[0062] Among them, the selenium-rich composition adopts a thermosensitive-enteric dual-controlled release coating: the outer enteric coating material is L100-55, with a thickness of 18 μm; the inner layer is thermosensitive hydroxypropyl methylcellulose, and its lower critical solution temperature (LCST) is 34 °C.

[0063] Example 3:

[0064] This example proposes the application of the selenium-rich composition in the drug for preventing bone marrow suppression after chemotherapy in dogs. The selenium-rich composition includes:

[0065] Nanoselenium-β-glucan chelate and L-seleno-methylselenocysteine, and the mass ratio of nanoselenium-β-glucan chelate to L-seleno-methylselenocysteine is 1:0.6;

[0066] Astragaloside IV and cobamamide, and the molar ratio of astragaloside IV to cobamamide is 8:1.

[0067] Among them, the selenium-rich composition uses silica mesoporous nanoparticles as the mesoporous carrier, and the pore diameter of the silica mesoporous particles is 6 nm.

[0068] Among them, the selenium-rich composition is in the form of oral pellets, and the administration dose is 1.5 mg Se / kg / day, and it is fed within 24 hours before and after chemotherapy.

[0069] Among them, the selenium-rich composition adopts a thermosensitive-enteric dual-controlled release coating: the outer enteric coating material is L100-55, with a thickness of 20 μm; the inner layer is thermosensitive hydroxypropyl methylcellulose, and its lower critical solution temperature (LCST) is 34 °C.

[0070] Example 4:

[0071] This example proposes a thermosensitive-enteric dual-controlled release coating method for the selenium-rich composition. The specific implementation process is as follows:

[0072] A1. Mix nanoselenium-β-glucan chelate and L-seleno-methylselenocysteine according to a mass ratio of 1:0.5, and then add astragaloside IV and cobamamide according to a molar ratio of 6:1 and dissolve them in a pH 7.0 phosphate buffer solution to obtain a drug solution;

[0073] A2. Immerse the mesoporous carrier and the drug solution in a ratio of 1:3 (w / v), and then load them by ultrasonic assistance;

[0074] A3. Centrifuge and separate, vacuum dry at 50 °C, and screen (sieve pore 180 μm) to obtain the drug-loaded pellets;

[0075] A4. Disperse hydroxypropyl methylcellulose and PEG6000 in pure water in proportion, and stir at 50 °C until completely dissolved to obtain a temperature-sensitive coating solution;

[0076] A5. The temperature-sensitive coating solution forms a temperature-sensitive layer on the surface of the drug-loaded pellets through a fluidized bed. Among them, the inlet air temperature is 40 °C, the liquid spraying rate is 3 mL / min, the atomization pressure is 0.8 bar, and hot air circulation drying is carried out at 40 °C for 2 hours to form a continuous temperature-sensitive film on the temperature-sensitive layer;

[0077] A6. Dissolve L100-55 and TEC in an ethanol-water mixed solvent in proportion, and stir magnetically until transparent to obtain an enteric coating solution;

[0078] A7. The enteric coating solution forms an enteric layer on the surface of the temperature-sensitive film of the pellets through a fluidized bed, and dries at 45 °C for 4 hours to completely form a film on the enteric layer, and sieves (sieve hole 300 μm) to select qualified pellets.

[0079] Example Five:

[0080] This example presents a preparation method of nano-selenium-β-glucan chelate in the selenium-rich composition. The specific preparation process is as follows:

[0081] B1. Dissolve 1 g of β-glucan (molecular weight 50 kDa) in deionized water to prepare a 4% (w / v) β-glucan solution, heat to 55 °C and stir until completely dissolved, and filter to remove impurities;

[0082] B2. Dissolve sodium selenite (selenium content 7.9 mg) in deionized water, stir and mix to prepare a 0.1 mol / L sodium selenite solution;

[0083] B3. Add the β-glucan solution and sodium selenite solution to a reaction kettle under light protection and nitrogen protection, and stir and mix;

[0084] B4. Add 0.5 g of vitamin C to the reaction kettle in three portions, with an interval of 10 minutes each time, and adjust the pH to 7.0;

[0085] B5. Under nitrogen protection, react the mixed solution in an ultrasonic reactor with an ultrasonic power density of 38 W / cm 2 for 3 hours;

[0086] B6. After the reaction is completed, centrifuge at 9000 rpm for 15 minutes to remove the unreacted precipitate, and filter the supernatant through a 0.22 μm filter membrane to obtain a nano-selenium-β-glucan chelate colloidal solution, and continue freeze-drying to obtain a nano-selenium-β-glucan chelate powder.

[0087] Example Six:

[0088] This example presents a method for preparing L-seleno-methylselenocysteine in a selenium-rich composition. The specific preparation process is as follows:

[0089] C1. Inoculate the preserved yeast strain Se-18 into a selenium-containing medium and ferment at 30 °C and pH 6.5 for 48 hours;

[0090] C2. Collect the bacterial cells by centrifugation, wash them, and then break the cells;

[0091] C3. Mix the broken liquid with L-cysteine and a methyl donor, and react in a buffer system at 37 °C and pH 7.4 for 7 hours;

[0092] C4. Regulate the yeast metabolic pathway to promote the methylation of selenocysteine by overexpressing cystathionine β-synthase CBS and methyltransferase;

[0093] C5. Separate L-seleno-methylselenocysteine by ion exchange chromatography and reverse-phase HPLC;

[0094] C6. Obtain high-purity L-seleno-methylselenocysteine crystals after freeze-drying.

[0095] Example Seven:

[0096] This example presents a method for verifying the efficacy of a selenium-rich composition, including the following process:

[0097] (1). Detect the CD34 and cell viability of canine bone marrow by flow cytometry and process for 1.5 hours;

[0098] (2). Replace the selenium in the selenium-rich composition with 75 Se isotope to track the metabolism of the drug in dogs in real time.

[0099] Experimental Test Example One:

[0100] This experimental test example is used to detect the selenium bioavailability of the selenium-rich composition pellets in Example One, sodium selenite, and selenomethionine. The specific implementation process is as follows:

[0101] (1). Select healthy beagle dogs (weighing 10 - 15 kg) and divide them into four groups, with 10 dogs in each group;

[0102] (2). Prepare selenium-rich composition pellets containing 75 SeO3 2- Se by microbial fermentation combined with 75 Se labeling, and directly purchase Na2 75 SeO3 solution and 75 Se-SeMet solution;

[0103] (3) After fasting for 12 hours, oral administration of a quantitative (at 0.3 mg Se / kg) selenium-containing 75 selenium-enriched composition pellets, Na2 75 SeO3 solution, and 75 Se-SeMet solution were separately given to three groups of beagle dogs. Another group served as blank group 1 (fed with an equal amount of basal diet). Then, blood samples were collected at 0.5, 1, 2, 4, 6, 12, 24, and 48 hours after taking the medicine, and the blood selenium content was detected by a high-purity germanium γ-ray spectrometer. The calculation results are as Figure 1 shown;

[0104] (4) After 48 hours, the dogs were euthanized, and the liver, kidney, muscle, bone marrow, hair, feces, and urine were separately taken, and the selenium content in each tissue was detected. The selenium absorption rate, selenium retention rate, and urine excretion rate were detected. The calculation formulas are as follows:

[0105]

[0106] The calculation results are shown in the following table:

[0107]

[0108] It can be Figure 1 seen that the selenium-containing 75 selenium-enriched composition pellet group maintained 50 μg / L at 48 hours, significantly higher than other groups, indicating that the nano-selenium chelate has the advantages of targeted delivery and long-acting release. As can be seen from the above table, the selenium absorption rate and selenium retention rate of the selenium-containing 75 selenium-enriched composition pellet group are significantly higher than other groups, indicating that the selenium bioavailability of the selenium-enriched composition pellet group is relatively high. Moreover, the urine excretion rate of the selenium-containing 75 selenium-enriched composition pellet group is relatively low, indicating that the selenium-enriched composition pellets have a light burden on the liver and kidney, low toxicity, and higher safety.

[0109] Experimental test example two:

[0110] This experimental test example was used to detect the effects of the selenium-enriched composition in Example 1 on the bone marrow CD34 and cell activity of dogs. The specific implementation process is as follows:

[0111] (1) Take the bone marrow fluid of healthy beagle dogs, separate mononuclear cells by density gradient centrifugation, and then select hematopoietic stem cells enriched with CD34 + by magnetic bead sorting method;

[0112] (2) Enrich CD34 +The hematopoietic stem cells were divided into two groups. One group was added with a selenium-rich composition of 10 μg Se / mL, and the other group was the blank group 2 (added with the same volume of physiological saline). Then, the two groups were cultured in a medium containing IL-3 and SCF for 48 hours;

[0113] (3) The OD450 values of the two groups were measured by the CCK-8 method respectively, and the proliferation rate was calculated. By Annexin V-FITC / PI double staining, flow cytometry analysis was performed, and the apoptosis rate was calculated. By staining and labeling with anti-CD34-APC antibody, the proportion of CD34 + cells was calculated. The calculation results are shown in the following table:

[0114]

[0115] As can be seen from the above table, the OD450 value of the selenium-rich composition group was significantly higher than that of the blank group 2 (1.86 vs 1.1), indicating that the selenium composition could promote the proliferation of CD34 + cells; the apoptosis rate of the selenium-rich composition group was greatly reduced compared with that of the blank group 2, indicating that the selenium composition protected cell activity through antioxidant or anti-apoptotic mechanisms; the proportion of CD34 + cells in the selenium-rich composition group remained at 93.21% after culture, which was significantly higher than 78.6% of the blank group 2, indicating that the selenium composition effectively maintained the stem cell phenotype and reduced differentiation or exhaustion.

[0116] Experimental test example three:

[0117] This experimental test example was used to detect the effects of the selenium-rich composition of Example 1 on the numbers of neutrophils and platelets during chemotherapy in dogs. The specific implementation process was as follows:

[0118] (1) Healthy beagle dogs (weighing 10 - 15 kg) were selected and randomly divided into three groups, with 10 dogs in each group;

[0119] (2) One group was given the selenium-rich composition of Example 1 (1.0 mg Se / kg / day), and the other two groups were used as the positive control group (administered recombinant granulocyte colony-stimulating factor) and the blank group 3 (administered physiological saline) respectively;

[0120] (3) Chemotherapy induction was performed on all three groups. Among them, cyclophosphamide (50 mg / kg) was intravenously injected on day 0, and the corresponding drugs were orally administered daily from day 1 to day 7;

[0121] (4) Blood samples were collected on days 3, 5, 7, and 10 after chemotherapy, and the neutrophil (NEUT) and platelet (PLT) counts of each group were detected by blood routine. The detection results are shown in the following table:

[0122]

[0123] As can be seen from the above table, on the 3rd day after chemotherapy, the NEUT in the selenium-rich composition group reached 1.8×10 9 / L (close to the safety threshold of 1.5×10 9 / L), significantly faster than the positive control group (reaching 2.2×10 9 / L on the 5th day) and the blank group three (only 1.5×10 9 / L on the 7th day), and the recovery time of neutrophils was greatly shortened; on the 7th day after chemotherapy, the PLT in the selenium-rich composition group was 184×10 9 / L, significantly higher than that of the blank group three (89×10 9 / L), indicating that the selenium composition effectively alleviates chemotherapy-induced thrombocytopenia;

[0124] In summary, the selenium composition significantly shortens the duration of neutropenia, and its platelet protection effect is better than that of G-CSF, suggesting that it can synergistically enhance the effect through antioxidant or megakaryocyte differentiation promotion mechanisms. The data support the use of the selenium composition as an adjuvant chemotherapy drug for relieving myelosuppression and protecting multi-lineage blood cells.

[0125] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. Use of a selenium-rich composition in a medicament for preventing myelosuppression after chemotherapy in dogs, characterized in that, The selenium-rich composition comprises: Nano-selenium-β-glucan chelate and L-seleno-methylselenocysteine, and the mass ratio of the nano-selenium-β-glucan chelate to L-seleno-methylselenocysteine is 1:(0.3 - 0.6); Astragaloside IV and cobamamide, and the molar ratio of Astragaloside IV to cobamamide is (5 - 8):

1.

2. Use of the selenium-rich composition according to claim 1 in a medicament for preventing myelosuppression after chemotherapy in dogs, characterized in that, The selenium-rich composition uses silica mesoporous nanoparticles as the mesoporous carrier, and the pore diameter of the silica mesoporous particles is 4 - 6 nm.

3. Use of the selenium-rich composition according to claim 2 in a medicament for preventing myelosuppression after chemotherapy in dogs, characterized in that, The selenium-rich composition is in the form of oral pellets, and the dosage is 0.5 - 1.5 mg Se / kg / day, and it is fed within 24 hours before and after chemotherapy.

4. Use of the selenium-rich composition according to claim 3 in a medicament for preventing bone marrow suppression after chemotherapy in dogs, characterized in that, The selenium-rich composition uses a temperature-sensitive - enteric double-controlled release coating: The outer enteric coating material is L100-55 with a thickness of 15-20 μm; The inner layer is temperature-sensitive hydroxypropyl methylcellulose, and its lower critical solution temperature is 34 °C.

5. Use of the selenium-rich composition according to claim 4 in a medicament for preventing myelosuppression after chemotherapy in dogs, characterized in that, The specific implementation process of the temperature-sensitive - enteric double-controlled release coating of the selenium-rich composition is as follows: A1. Mix the nano-selenium-β-glucan chelate and L-seleno-methylselenocysteine according to the mass ratio, then add Astragaloside IV and cobamamide according to the molar ratio and dissolve them in pH 7.0 phosphate buffer solution to obtain a drug solution; A2. Immerse the mesoporous carrier and the drug solution in a ratio of 1:3 (w / v), and then load them by ultrasonic assistance; A3. Centrifuge and separate, vacuum dry at 50 °C, and screen to obtain drug-loaded pellets; A4. Disperse hydroxypropyl methylcellulose and PEG6000 in pure water according to the ratio, and stir at 50 °C until completely dissolved to obtain a temperature-sensitive coating solution; A5. The temperature-sensitive coating solution forms a temperature-sensitive layer on the surface of the drug-loaded pellets through a fluidized bed. Among them, the inlet air temperature is 40 °C, the liquid spraying rate is 3 - 5 mL / min, the atomization pressure is 0.8 - 1.2 bar, and hot air is circulated and dried at 40 °C for 2 hours to form a continuous temperature-sensitive film for the temperature-sensitive layer; A6. Dissolve L100-55 and TEC in an ethanol-water mixed solvent in proportion, and stir magnetically until transparent to obtain an enteric coating solution; A7. The enteric coating solution forms an enteric layer on the surface of the temperature-sensitive film of the pellets through a fluidized bed, and dries at 45 °C for 4 hours to completely form the enteric film, and screen and select qualified pellets.

6. Use of the selenium-rich composition according to claim 1 in a medicament for preventing bone marrow suppression after chemotherapy in dogs, characterized in that, The preparation process of the nano-selenium-β-glucan chelate is as follows: B1. Dissolve β-glucan in deionized water to prepare a 2 - 4% (w / v) β-glucan solution, heat to 50 - 60 °C and stir until completely dissolved, and filter to remove impurities; B2. Dissolve sodium selenite in deionized water, stir and mix to prepare a 0.1 - 0.3 mol / L sodium selenite solution; B3. Add the β-glucan solution and the sodium selenite solution to a reaction kettle under light protection and nitrogen protection, and stir and mix; B4. Add vitamin C to the reaction kettle in three times, with an interval of 10 minutes each time, and adjust the pH to 6.8 - 7.2; B5. Under nitrogen protection, react the mixed solution in an ultrasonic reactor with an ultrasonic power density of 35 - 40 W / cm 2 for 2 - 4 hours; B6. After the reaction is completed, centrifuge at 8000 - 10000 rpm for 15 minutes to remove the unreacted precipitate, and filter the supernatant through a 0.22 μm filter membrane to obtain a nano-selenium-β-glucan chelate colloidal solution, and continue freeze-drying to obtain nano-selenium-β-glucan chelate powder.

7. Use of the selenium-enriched composition according to claim 6 in a medicament for preventing myelosuppression after chemotherapy in dogs, characterized in that, During the preparation process of the nano-selenium-β-glucan chelate: The volume percentage of β-glucan solution in the mixed solution is 60-70%, and the molar ratio of sodium selenite solution to vitamin C is 1:

5.

8. Use of the selenium-rich composition according to claim 1 in a medicament for preventing myelosuppression after chemotherapy in dogs, characterized in that, The preparation process of the L-seleno-methylselenocysteine is as follows: C1. Inoculate the preserved yeast strain Se-18 into a selenium-containing medium and ferment at 30 °C and pH 6.5 for 48 hours; C2. Collect the thalli by centrifugation, wash them and then break the cells; C3. Mix the broken solution with L-cysteine and a methyl donor, and react in a buffer system at 37 °C and pH 7.4 for 6-8 hours; C4. Promote the methylation of selenocysteine by genetically engineering to regulate the yeast metabolic pathway; C5. Separate L-seleno-methylselenocysteine by ion exchange chromatography and reverse-phase HPLC; C6. Obtain high-purity L-seleno-methylselenocysteine crystals after freeze-drying.

9. Use of the selenium-rich composition according to claim 8 in a medicament for preventing myelosuppression after chemotherapy in dogs, characterized in that, During the preparation process of the L-seleno-methylselenocysteine: The genetic engineering regulation of the yeast metabolic pathway is achieved by means of overexpressing cystathionine β-synthase CBS and methyltransferase.

10. Use of the selenium-rich composition according to claim 1 in the medicament for preventing myelosuppression after chemotherapy in dogs, characterized in that, The efficacy of the selenium-rich composition is verified by the following method: (1). Detect the canine bone marrow CD34 and cell viability by flow cytometry, and the treatment time is ≤ 2 hours; (2), Replace the selenium in the selenium-rich composition with 75 Se isotope to track the metabolism of the drug in dogs in real time.

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