Hexagonal boron nitride-polyvinylpyrrolidone nanoparticle coated with cell exosome as well as preparation method and application of hexagonal boron nitride-polyvinylpyrrolidone nanoparticle

Abstract

The invention discloses a cellular exosome-coated hexagonal boron nitride / polyvinylpyrrolidone nano-particle as well as a preparation method and application thereof, relates to the technical field of medicines, and aims to solve the problem that in the prior art, in BNCT tumor treatment, the BNCT treatment effect is poor. In order to solve the problems of poor targeting and biocompatibility of a boron carrying agent, insufficient in-vivo stability and tumor accumulation capacity of nanoparticles and the like, the boron carrying agent comprises hexagonal boron nitride-polyvinylpyrrolidone nanoparticles and cell exosomes wrapping the peripheries of the hexagonal boron nitride-polyvinylpyrrolidone nanoparticles, and cells are adherent cells. The targeting property and biocompatibility of the boron carrying agent and the in-vivo stability and tumor accumulation capacity of nanoparticles can be effectively enhanced, and the BNCT treatment effect of glioma is improved.

Description

Technical Field

[0001] The invention relates to a hexagonal boron nitride@polyvinyl pyrrolidone nanoparticle wrapped in cell exosomes and a preparation method and application thereof, belonging to the field of medical technology. Background Art

[0002] Boron neutron capture therapy (BNCT) uses alpha particles and 7 Li particles are charged particles with high linear energy transfer density (LET), which can have a killing effect on oxygen-rich or oxygen-deficient tumor cells. It has the advantages of high precision and high efficacy in the treatment of refractory cancers such as glioblastoma, recurrent head and neck tumors, and malignant melanoma. Clinical trials have also been carried out for other common tumors such as liver cancer, lung cancer, and prostate cancer, which also have good therapeutic effects. After nearly 70 years of development, BNCT was finally approved in Japan in 2020 for the clinical treatment of unresectable locally advanced or locally recurrent cancers.

[0003] When BNCT is used to treat tumors, the patient is first injected with a boron delivery agent to make it accumulate in the tumor site, and then the tumor site is irradiated with a thermal neutron beam. 10 The neutron capture cross section of B atom is 3 835 b (1 b=10 -28 m2), which is 3 orders of magnitude higher than other elements in the body. 10 B) Nuclear fission reaction occurs to produce alpha particles with high linear energy transfer (LET) and recoil lithium-7 ( 7 Li) nuclei, of which the penetration distance of α particles is very short, only 4 to 9 μm, which is close to the diameter of the cell. 10 B is selectively delivered to tumor cells to capture thermal neutrons, which can achieve specific killing of tumor cells and avoid damage to adjacent normal cells.

[0004] In May 2020, the Japanese Ministry of Health, Labor and Welfare approved the first boron drug for clinical treatment of BNCT, Borofalan [ 10 B], "Steboronine®"). Its main component is (L)-4-dihydroxyborylphenylalanine (boronophenylalanine, BPA), which is a derivative of the neutral amino acid phenylalanine. Because its structure is similar to tyrosine (Tyr), it can serve as a substrate for tyrosinase and synthesize macromolecules through the melanin metabolic pathway. Therefore, BPA-BNCT was first used to treat skin melanoma. In addition, because BPA can cross the BBB through LAT1, it is also widely used in BNCT for head and neck malignancies.

[0005] The key to successful BNCT treatment is to 10 B is selectively delivered to the tumor cells. However, compared with the delivery system of chemotherapy drugs, the boron delivery agent used in BNCT does not need to be delivered to the tumor cells. 10 B is released, and then 10 The nuclear reaction of boron with thermal neutrons produces a killing effect on tumor cells. Clinically, boron delivery agents are required to meet at least the following three conditions: ① low toxicity, the ability to be enriched in tumors and quickly cleared from normal tissues; ② 10 B content is greater than 20 µg / g (equivalent to at least 10 9 indivual 10 B atoms); ③ The ratio of boron concentration in tumor to normal tissue (T / N) and the ratio of boron concentration in tumor to blood (T / B) are greater than 3.

[0006] So far, there are only two boron-containing drugs that are recognized as the best and widely used in clinical practice, namely L-borylphenylalanine (BPA) and sodium mercaptoundecahydrocloso-dodecaborate (BSH).

[0007] BPA relies on LAT1 for selective transport into cells, but LAT1 has bidirectional transport capacity. In order to maintain the physiological needs and balance of cells, it will also exchange intracellular BPA with extracellular amino acids, resulting in the efflux of BPA. However, BNCT usually requires 30 to 60 minutes of thermal neutron irradiation, and the continuous decrease in the concentration of BPA in tumor cells affects the therapeutic effect. Therefore, in the clinical treatment of BNCT, continuous intravenous infusion is used to maintain a high intratumoral boron concentration. However, this also increases the potential risks of BNCT and affects the therapeutic effect.

[0008] Sodium mercaptoundecahydro-closo-dodecaborate (Na2B12H11SH, BSH) is a polyhedral borane structure rich in boron atoms with good chemical stability and biocompatibility. BSH can cross the BBB and accumulate in brain tumors, and has been used in clinical brain tumor BNCT treatment research. However, since BSH cannot enter tumor cells, the tumor targeting of BSH has been questioned, making it difficult to achieve precise BNCT of tumor cells using BSH.

[0009] With the booming development of nanotechnology, many nanomaterials have been widely studied and explored for tumor treatment. Hexagonal boron nitride nanoparticles have become potential excellent drug carriers due to their excellent physical and chemical properties, such as high specific surface area, good thermal stability and chemical inertness. However, these nanoparticles have shortcomings in terms of stability in the body, blood circulation time and targeting, which limits their application in tumor treatment.

[0010] Exosomes are lipid bilayer extracellular vesicles ranging from 30 to 150 nm that are released when multivesicular bodies (MVBs) fuse with the plasma membrane. The production of exosomes can be divided into four steps: 1) endocytosis and formation of early endosomes; 2) budding of the endosomal membrane to form intraluminal vesicles; 3) formation of multivesicular bodies (MVBs) or late endosomes; 4) release of exosomes from cells. Exosomes can show high cellular uptake efficiency by directly interacting with specific proteins outside target cells or directly fusing with target cells through integrins from specific sources or being internalized by target cells. Summary of the invention

[0011] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a kind of hexagonal boron nitride@polyvinyl pyrrolidone nanoparticles encapsulated by cell exosomes and its preparation method and application, which can effectively enhance the targeting and biocompatibility of boron carriers, the in vivo stability and tumor accumulation ability of nanoparticles, and improve the BNCT treatment effect of glioma.

[0012] To achieve the above object, the present invention is implemented by adopting the following technical solutions: In a first aspect, the present invention provides a cell exosome-encapsulated hexagonal boron nitride@polyvinyl pyrrolidone nanoparticle, comprising hexagonal boron nitride@polyvinyl pyrrolidone nanoparticles and cell exosomes encapsulated around the hexagonal boron nitride@polyvinyl pyrrolidone nanoparticles, wherein the cells are adherent cells.

[0013] Optionally, the hexagonal boron nitride@polyvinyl pyrrolidone nanoparticles have a particle size range of 10 to 30 nm, and are distributed in ultrapure water in the form of nanoparticles. The concentration of the boron element in the ultrapure water ranges from 0.5 to 1.5 mg / ml.

[0014] Optionally, the volume ratio of the exosomes to hexagonal boron nitride@polyvinyl pyrrolidone is 1-4:1; and / or the volume ratio of hexagonal boron nitride to polyvinyl pyrrolidone in the hexagonal boron nitride@polyvinyl pyrrolidone is 2-5:1.

[0015] In a second aspect, the present invention further provides a method for preparing the exosome-encapsulated hexagonal boron nitride@polyvinyl pyrrolidone nanoparticles as described in any one of the above, comprising: Extracting cell exosomes; Hexagonal boron nitride and polyvinyl pyrrolidone are used to synthesize hexagonal boron nitride@polyvinyl pyrrolidone; The cell exosomes are encapsulated in the periphery of hexagonal boron nitride@polyvinyl pyrrolidone by electroporation to obtain cell exosome-encapsulated hexagonal boron nitride@polyvinyl pyrrolidone nanoparticles.

[0016] Furthermore, the extraction of exosomes comprises: After the fetal bovine serum is centrifuged a, the upper suspension is taken to obtain exosome-free serum; Cells were cultured in medium prepared with exosome-free serum; The cell supernatant was collected and concentrated by centrifugation; Adding an exosome extractant to the cell supernatant after centrifugation and concentration, mixing evenly and refrigerating to obtain a mixed solution; The mixed solution was centrifuged to obtain the precipitate, which was then resuspended in PBS to obtain exosomes.

[0017] Furthermore, culturing cells with a medium prepared with exosome-free serum comprises: The cells were cultured in a DMEM high-glucose medium containing 5-15% exosome-free serum and 0.5-1.5% penicillin-streptomycin in an incubator; And / or, the centrifugal treatment a includes 1×10 5 ~1.4×10 5 Centrifuge at g for 10-18 hours; And / or, the centrifugation treatment b includes 8×10 3 ~1.2×10 4 Centrifuge at g centrifugal force for 0.5~1.5h; And / or, the centrifugal concentration comprises 3×10 3 ~5×10 3 The cell supernatant was concentrated to 1 / 60~1 / 20 of the original volume by centrifugal force; And / or, the standing time is 14 to 20 hours.

[0018] Furthermore, the method of synthesizing hexagonal boron nitride@polyvinyl pyrrolidone by using hexagonal boron nitride and polyvinyl pyrrolidone comprises: Take hexagonal boron nitride and polyvinyl pyrrolidone, add ultrapure water, and obtain a mixed solution after ultrasonication; The mixed solution is centrifuged and the supernatant is taken to obtain hexagonal boron nitride@polyvinyl pyrrolidone.

[0019] Furthermore, the ultrasonic parameters include using ice bath ultrasound for 6 to 10 hours; and / or the centrifugal treatment includes centrifugation at 2000 to 4000 rpm for 10 to 20 minutes.

[0020] Furthermore, the method of encapsulating the cell exosomes in the periphery of hexagonal boron nitride@polyvinyl pyrrolidone by electroporation to obtain hexagonal boron nitride nanoparticles encapsulated by the cell exosomes comprises: At 2-6°C, exosomes and hexagonal boron nitride@polyvinyl pyrrolidone were added to PBS buffer and mixed, and then incubated at 2-6°C after electroporation to obtain exosome-encapsulated hexagonal boron nitride nanoparticles. The electroporation parameters include an electroporation voltage range of 300-400 V, a pulse duration range of 80-120 us, a pulse interval range of 800-1200 ms, and a pulse number of 8-12 times.

[0021] In a third aspect, the present invention provides a drug for treating glioma by boron neutron capture, comprising hexagonal boron nitride@polyvinyl pyrrolidone nanoparticles encapsulated by cell exosomes as described in any of the above items.

[0022] Compared with the prior art, the present invention has the following beneficial effects: The present invention uses hexagonal boron nitride@polyvinyl pyrrolidone nanoparticles as a boron carrier, which overcomes the defects of using a simple boron-containing small molecule compound as a boron carrier, can maintain a high boron concentration in the tumor for a long time, significantly prolongs the half-life of the boron carrier in the blood circulation, can maintain an effective drug concentration for a long time, has a good tumor targeting enrichment effect, and realizes a continuous and stable supply of boron elements for BNCT, thereby improving the treatment effect; The present invention uses cell exosomes to encapsulate hexagonal boron nitride@polyvinyl pyrrolidone nanoparticles. Exosomes enable nanoparticles to penetrate tumor tissue more effectively, improve the uniformity of drug distribution inside the tumor, enhance the in vivo stability of nanoparticles, improve surface specificity, and be easily recognized by tumor cells, greatly improving the targeted enrichment ability of nanoparticles for glioma cells, ensuring that more boron elements accurately reach the tumor site and achieve effective accumulation at the tumor site, while significantly reducing side effects such as immune response caused by nanoparticles; The present invention extracts exosomes by a concentration and re-extraction method. Compared with the traditional ultracentrifugation method, the yield is increased by 20 times and it is simpler. The extracted exosomes are also more stable. The encapsulation rate of nanoparticles is also greatly optimized by encapsulation through electroporation drug loading. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a transmission electron microscopic diagram of macrophage exosomes in Example 1 of the present invention; Figure 2 This is a schematic diagram of detecting marker proteins of macrophage exosomes in Example 1 of the present invention; Figure 3 This is a schematic diagram of the DLS test of macrophage exosomes in Example 1 of the present invention; Figure 4 It is a schematic diagram of the uptake of macrophage exosomes by SNB19 cells after SNB19 cells were co-incubated with hexagonal boron nitride@polyvinyl pyrrolidone nanoparticles encapsulated by cell exosomes in Example 1 of the present invention for 2 hours; Figure 5 Schematic diagram of the preparation of hexagonal boron nitride@polyvinyl pyrrolidone nanoparticles encapsulated by cell exosomes in an embodiment of the present invention; Figure 6 This is a schematic diagram of the infrared spectrum of hexagonal boron nitride@polyvinyl pyrrolidone nanoparticles encapsulated by cell exosomes in Example 1 of the present invention; Figure 7 This is a transmission electron microscopic diagram of hexagonal boron nitride@polyvinyl pyrrolidone nanoparticles encapsulated by cell exosomes in Example 1 of the present invention. DETAILED DESCRIPTION

[0024] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention. Example 1

[0025] The embodiment of the present invention provides a method for preparing hexagonal boron nitride@polyvinyl pyrrolidone nanoparticles encapsulated by cell exosomes. In this embodiment, the cells are macrophages, and the method comprises the following steps: Extraction of exosomes Prepare exosome-free fetal bovine serum (FBS): Add fetal bovine serum into a sterilized sealed centrifuge tube in a sterile clean bench and place in an ultracentrifuge at 1.2×10 5 Centrifuge for 14 h, remove the centrifuge tube, and carefully aspirate the upper suspension in a sterile clean bench to obtain exosome-free serum.

[0026] Cell culture medium selection: DMEM high-glucose medium containing 10% exosome-free serum and 1% penicillin-streptomycin was used.

[0027] The GL261 cell line and the RAW264.7 cell line were placed at 37°C and 5% CO 2 When the cells were cultured to about 80% in the culture dish, the cell supernatant was collected.

[0028] 300 mL of cell supernatant was transferred to an ultrafiltration tube and concentrated to 9 mL at 4000 g centrifugal force. The supernatant was transferred to a new tube and one-third volume of exosome extractant was added. The sample was mixed by inversion until it was completely mixed and placed in a 4 °C refrigerator for 16 h.

[0029] The mixture was transferred to a centrifuge tube and incubated at 4 °C at 1 × 10 4 The mixture was centrifuged for 1 h, the supernatant was discarded, and PBS was added to resuspend the precipitate to obtain the exosomes.

[0030] 2. Synthesis of hexagonal boron nitride@polyvinyl pyrrolidone nanoparticles Preparation of hexagonal boron nitride (BN): Take 3.72 g of boric acid (H 3 BO 3 ) and 1.26 g melamine (C 3 H 6 N 6 ) into a grinding mortar and grind until completely mixed. After completely mixed, place it into a tube furnace and introduce nitrogen (N 2 ), and sinter at 900℃ for 3 hours to obtain hexagonal boron nitride.

[0031] Take 400 mg of hexagonal boron nitride and add 100 mg of polyvinyl pyrrolidone, transfer to a glass flask, add 50 mL of ultrapure water, and sonicate for 8 hours.

[0032] The mixed solution after ultrasound was transferred to a 50 mL centrifuge tube, centrifuged at 3000 rpm for 15 min, and the supernatant was taken. Finally, it was dialyzed and purified for 48 h to obtain hexagonal boron nitride@polyvinyl pyrrolidone nanoparticles (BN@PVP).

[0033] 3. Electroporation Packaging At 4°C, 800ug of the isolated exosomes with a concentration of 1mg / mL and 200ug of hexagonal boron nitride@polyvinyl pyrrolidone with a concentration of 1mg / mL were gently mixed in 100uL of PBS buffer pre-cooled at 4°C.

[0034] An Eppendorf electroporator was used with an electroporation voltage of 350 V, a pulse duration of 100 us, a pulse interval of 1000 ms, and 10 pulse times.

[0035] The electrically stimulated hexagonal boron nitride@polyvinyl pyrrolidone and exosome mixture was incubated at 37°C for 30 min to ensure that the exosome biofilm was fully restored, and hexagonal boron nitride@polyvinyl pyrrolidone nanoparticles (BN@PVP-Exos) encapsulated with cell exosomes were obtained. Example 2

[0036] The only difference between this example and Example 1 is that 400 μg of exosomes with a concentration of 1 mg / ml and 200 μg of BN@PVP with a boron concentration of 1 mg / mL are gently mixed in 1000 μL of PBS buffer precooled at 4°C. That is, the volume ratio of exosomes to hexagonal boron nitride nanoparticles in this example is 2:1. Example 3

[0037] The only difference between this example and Example 1 is that 200 μg of exosomes with a concentration of 1 mg / ml and 200 μg of BN@PVP with a boron concentration of 1 mg / mL are gently mixed in 1000 μL of PBS buffer precooled at 4°C. That is, the volume ratio of exosomes to hexagonal boron nitride nanoparticles in this example is 1:1.

[0038] The characteristics of the macrophage exosomes, hexagonal boron nitride@polyvinyl pyrrolidone nanoparticles (BN@PVP), and hexagonal boron nitride@polyvinyl pyrrolidone nanoparticles encapsulated by the macrophage exosomes obtained in Example 1 were analyzed.

[0039] The macrophage exosomes and retrograde electron microscopy observations, such as Figure 1 As shown, it can be clearly seen that the nanomaterials present a regular, nearly spherical structure or a quasi-round saucer-like / cup-shaped structure, are evenly distributed, have good dispersion, and mostly have a distinct membranous structure with clear boundaries. The overall particle size ranges from 50nm to 150nm, and most of them are around 100nm, which is consistent with the typical characteristics of exosomes.

[0040] Detection of marker proteins in macrophage exosomes, such as Figure 2 As shown, Western Blotting confirmed that the exosomes were positive for markers TSG101 and CD9, and negative for marker calnexin. CD9 and Tsg101 are transmembrane proteins, which are enriched on the surface of exosomes and are considered to be specific marker proteins of exosomes. High expression was observed in macrophage exosomes, indicating that the concentration of macrophage exosomes extracted in this experiment was high.

[0041] DLS detection of macrophage exosomes, such as Figure 3 As shown, it can be observed that the particle size of macrophage exosomes is about 90±25nm, the membrane surface is negatively charged, the average zeta potential is: -5.35±0.35 mv, and the dispersion coefficient (PDI) is 0.415. The stable particle size and low PDI indicate that the nanomaterial has good dispersibility in the solution and low aggregation tendency, which is conducive to long-term stable existence in the blood circulation after intravenous injection, increasing the probability of accumulation in the tumor site and improving the treatment effect.

[0042] Next, the exosomes were traced with Dil fluorescent dye and the cell nucleus was labeled with Hoechst dye, e.g. Figure 4 As shown, the results showed that after 2 hours of co-incubation with SNB19 cells, macrophage exosomes could have a good accumulation effect in the cells.

[0043] Infrared spectroscopy was performed on exosome-encapsulated hexagonal boron nitride@polyvinyl pyrrolidone nanoparticles (BN@PVP-Exos), such as Figure 6 As shown, compared with simple macrophage exosomes, characteristic peaks of hexagonal boron nitride at 1373,771 wavelengths can be observed, indicating that the coating does not damage the chemical structure of the material, maintains the original physical and chemical properties while imparting biological functions. Figure 7 ,Under transmission electron microscopy, obvious granular nanomaterials can be observed in macrophage exosomes, proving that BN@PVP can be well encapsulated by macrophage exosomes.

[0044] Next, a comparative analysis was performed on Examples 1 to 3, and a DLS test was performed on the hexagonal boron nitride@polyvinyl pyrrolidone nanoparticles encapsulated by the cell exosomes obtained in Examples 1 to 3. The test results were compared as follows: (1) Particle size and dispersion coefficient: The hydrated particle size of the boron nitride nanomaterials encapsulated by exosomes in Example 1 is distributed in the range of 50 to 130 nm, that of Example 2 is in the range of 20 to 150 nm, and that of Example 3 is in the range of 10 to 1500 nm. By comparison, it can be seen that the particle size distribution of Example 1 is relatively narrower, indicating that more hexagonal boron nitride@polyvinyl pyrrolidone nanoparticles are encapsulated by exosomes, and are more stable and effective during in vivo circulation and drug delivery. The polydispersity coefficient (PDI) of Example 1 is 0.267, compared with 0.334 of Example 2 and 0.423 of Example 3, indicating that the distribution of the nanomaterial is more uniform.

[0045] (2) Zeta potential has a larger absolute value: the Zeta potential in Example 1 is -8~-5mV, and its absolute value is greater than -6~-3mV in Example 2 and -6~-2mV in Example 3. The larger the absolute value of the Zeta potential, the higher the surface charge density of the nanoparticles and the stronger the electrostatic repulsion, thereby enhancing the colloidal stability and more effectively preventing aggregation and precipitation, which is beneficial to improving the stability of the nanoparticles during storage and application, and ensuring the quality and efficacy of the drug preparation.

[0046] In summary, the optimal volume ratio of exosomes to hexagonal boron nitride@polyvinyl pyrrolidone is 4:1.

[0047] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A hexagonal boron nitride@polyvinyl pyrrolidone nanoparticle encapsulated by cell exosomes, characterized in that: The invention comprises hexagonal boron nitride@polyvinyl pyrrolidone nanoparticles and cell exosomes wrapped around the hexagonal boron nitride@polyvinyl pyrrolidone nanoparticles, and the cells are adherent cells.

2. The exosome-encapsulated hexagonal boron nitride@polyvinyl pyrrolidone nanoparticles according to claim 1, characterized in that: The hexagonal boron nitride@polyvinyl pyrrolidone nanoparticles have a particle size range of 10-30 nm and are distributed in ultrapure water in the form of nanoparticles. The concentration of the boron element in the ultrapure water ranges from 0.5-1.5 mg / ml.

3. The exosome-encapsulated hexagonal boron nitride@polyvinyl pyrrolidone nanoparticles according to claim 1, characterized in that: The volume ratio of the exosomes to hexagonal boron nitride@polyvinyl pyrrolidone is 1-4:1; and / or the volume ratio of hexagonal boron nitride to polyvinyl pyrrolidone in the hexagonal boron nitride@polyvinyl pyrrolidone is 2-5:

1.

4. A method for preparing exosome-encapsulated hexagonal boron nitride@polyvinyl pyrrolidone nanoparticles according to any one of claims 1 to 3, characterized in that: include: Extracting cell exosomes; Hexagonal boron nitride and polyvinyl pyrrolidone are used to synthesize hexagonal boron nitride@polyvinyl pyrrolidone; The cell exosomes are encapsulated in the periphery of hexagonal boron nitride@polyvinyl pyrrolidone by electroporation to obtain cell exosome-encapsulated hexagonal boron nitride@polyvinyl pyrrolidone nanoparticles.

5. The method for preparing exosome-encapsulated hexagonal boron nitride@polyvinyl pyrrolidone nanoparticles according to claim 4, characterized in that: The method of extracting cell exosomes comprises: After the fetal bovine serum is centrifuged a, the upper suspension is taken to obtain exosome-free serum; Cells were cultured in medium prepared with exosome-free serum; The cell supernatant was collected and concentrated by centrifugation; Adding an exosome extractant to the cell supernatant after centrifugation and concentration, mixing evenly and refrigerating to obtain a mixed solution; The mixed solution was centrifuged to obtain the precipitate, which was then resuspended in PBS to obtain the exosomes.

6. The method for preparing exosome-encapsulated hexagonal boron nitride@polyvinyl pyrrolidone nanoparticles according to claim 5, characterized in that: The method of culturing cells using a medium prepared with exosome-free serum comprises: The cells were cultured in a DMEM high-glucose medium containing 5–15% exosome-free serum and 0.5–1.5% penicillin-streptomycin in an incubator; And / or, the centrifugal treatment a includes 1×10 5 ~1.4×10 5 Centrifuge at g for 10-18 hours; And / or, the centrifugation treatment b includes 8×10 3 ~1.2×10 4 Centrifuge at g centrifugal force for 0.5~1.5h; And / or, the centrifugal concentration comprises 3×10 3 ~5×10 3 The cell supernatant was concentrated to 1 / 60~1 / 20 of the original volume by centrifugal force; And / or, the standing time is 14 to 20 hours.

7. The method for preparing exosome-encapsulated hexagonal boron nitride@polyvinyl pyrrolidone nanoparticles according to claim 4, characterized in that: The method of synthesizing hexagonal boron nitride@polyvinyl pyrrolidone by using hexagonal boron nitride and polyvinyl pyrrolidone comprises: Take hexagonal boron nitride and polyvinyl pyrrolidone, add ultrapure water, and obtain a mixed solution after ultrasonication; The mixed solution is centrifuged and the supernatant is taken to obtain hexagonal boron nitride@polyvinyl pyrrolidone.

8. The method for preparing exosome-encapsulated hexagonal boron nitride@polyvinyl pyrrolidone nanoparticles according to claim 7, characterized in that: The ultrasonic parameters include using ice bath ultrasound for 6 to 10 hours; and / or the centrifugal treatment includes centrifugation at 2000 to 4000 rpm for 10 to 20 minutes.

9. The method for preparing exosome-encapsulated hexagonal boron nitride@polyvinyl pyrrolidone nanoparticles according to claim 4, characterized in that: The method of encapsulating macrophage exosomes in the periphery of hexagonal boron nitride@polyvinyl pyrrolidone by electroporation to obtain hexagonal boron nitride nanoparticles encapsulated by cell exosomes comprises: At 2-6°C, exosomes and hexagonal boron nitride@polyvinyl pyrrolidone were added to PBS buffer and mixed, and then incubated at 2-6°C after electroporation to obtain exosome-encapsulated hexagonal boron nitride nanoparticles. The electroporation parameters include an electroporation voltage range of 300-400 V, a pulse duration range of 80-120 us, a pulse interval range of 800-1200 ms, and a pulse number of 8-12 times.

10. A drug for treating glioma by boron neutron capture, characterized in that: It comprises hexagonal boron nitride@polyvinyl pyrrolidone nanoparticles encapsulated by cell exosomes as described in any one of claims 1 to 3.

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