Modified boron carbide particles and neutron capture therapy drugs containing the same

Abstract

To provide a new boron preparation.SOLUTION: A modified boron carbide particle powder contains boron carbide particles, wherein at least part of the surface of at least some of the boron carbide particles in the boron carbide particles is modified with polyglycerol. The polyglycerol-modified boron carbide particle powder is inherently less toxic and can be administered in a shorter time, and can be suitably used in boron neutron capture therapy applications.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to modified boron carbide particles and a neutron capture therapy drug containing the same, and more particularly to boron carbide particles in which at least a portion of the surface of the boron carbide particles has been modified with polyglycerol, and a neutron capture therapy drug containing the same. [Background technology]

[0002] Boron Neutron Capture Therapy (BNCT) is a method of ionizing radiation by combining neutrons and boron ( 10 BNCT is a non-invasive cancer treatment with few side effects, based on particle beams generated by nuclear reactions with boron (B) (see, for example, Non-Patent Document 1). With the recent spread of hospital-based neutron generators, insurance coverage began in May 2020, and BNCT is becoming a more familiar cancer treatment (see, for example, Non-Patent Documents 2 and 3). However, the boron formulations used in BNCT still lack dispersibility and tumor accumulation, and the development of new boron formulations is needed to popularize BNCT.

[0003] Two types of formulations have been used for BNCT: BSH (mercaptoundecahydrododecaborate), a boron cage cluster, and BPA (p-boronophenylalanine), an amino acid (phenylalanine) to which boron has been introduced (see Non-Patent Documents 4 and 5). The former (BSH) has the problem of low tumor selectivity, while the latter (BPA) has the problem of low water solubility. BPA is manufactured and sold by Stella Pharma Corporation under the trade name Borofalan. However, due to its low water solubility, tens of grams of BPA are currently administered by intravenous infusion over several hours. Furthermore, BPA is known to be taken up by cancer cells via LAT1 (L-amino acid transporter 1), limiting its applicability to certain cancers. Therefore, the future development of BNCT strongly demands the development of new boron formulations designed from a completely new perspective.

[0004] Patent Document 1 discloses particles capable of being selectively taken up by tumor cells, in which the surfaces of boron carbide particles having a particle size of 200 nm to 1000 nm are coated with polylysine and then polyglutamic acid, and the surfaces are then modified with transferrin, with the polyglutamic acid and the transferrin being bound to each other via crosslinking via carboxyl groups of the polyglutamic acid, and a drug for neutron capture therapy comprising such particles. Patent Document 1 discloses that boron carbide particles of the above particle size can be efficiently taken up by cancer cells by modifying them with transferrin (see paragraphs 0009, 0013, 0027 to 0035, etc. of Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6142994 specification [Non-patent literature]

[0006] [Non-Patent Document 1] MA Dymova, SY Taskaev, VA Richter, EV Kuligina, Cancer Commun. 2020, 40, 406. [Non-patent document 2] M. Suzuki, Int. J. Clin. Oncol. 2020, 25, 43. [Non-patent document 3] RF Barth, JC Grecula, Appl. Radiat. Isot. 2020, 160, 109029. [Non-patent document 4] Haritz, D., et al., Int. J. Radiat. Oncol. Biol Phys., 28 1175-1181(1994). [Non-Patent Document 5] Ryynanen, PM, et al., Int. J. Radiat. Oncol. Biol. Phys., 48,1145-1154(2000). [Non-patent document 6] Y. Ishikawa, Q. Feng, N. Koshizaki, Appl. Phys. A 2010, 99, 797. [Non-Patent Document 7] T. Kobayashi, K. Kanda, Nucl. Instrument. Methods 1983, 204, 525. Summary of the Invention [Problem to be solved by the invention]

[0007] New drugs for boron neutron capture therapy are expected to have the following properties: (1) inherently low toxicity, (2) shorter administration time (higher water solubility or water dispersibility), and (3) higher boron accumulation in tumors (higher boron concentration in tumor cells). 10 (4) be able to persist in the tumor for a long time but be rapidly removed from the blood (e.g., the B concentration is more preferably 20 ppm (wt / wt) or more); and (5) be able to persist in the tumor for a long time but be rapidly removed from the blood (e.g., the B concentration in the tumor 10 B concentration and blood 10 The ratio to the B concentration (T / B ratio) is more preferably 3 or more). [Means for solving the problem]

[0008] As a result of extensive research, the present inventors have discovered that modified boron carbide particles, at least a portion of whose surface is modified with polyglycerol, can be obtained by reacting boron carbide particles with glycidol. Furthermore, they have discovered that such modified boron carbide particles are suitable for boron neutron capture therapy because they are inherently less toxic, can be administered in a shorter time, can accumulate boron at higher concentrations in tumors, and can persist in tumors for a long time while being rapidly removed from the blood. Based on this discovery, the present invention has been completed.

[0009] This specification includes the following forms. 1. A boron carbide particle powder comprising boron carbide particles, at least a portion of the surface of at least some of the boron carbide particles being modified with polyglycerol. 2. The modified boron carbide particles according to 1 above, having a median diameter of more than 0.5 nm and not more than 1000 nm. 3. The modified boron carbide particle powder according to 1 or 2 above, wherein the polyglycerol content is 0.1% by mass or more and 99.9% by mass or less, based on the modified boron carbide particles (100% by mass). 4. The modified boron carbide particle powder according to any one of 1 to 3 above, wherein the boron carbide particles have an average particle size of less than 1000 nm. 5. The modified boron carbide particles according to any one of 1 to 4 above, which have a spherical shape. 6. A drug for neutron capture therapy, comprising the modified boron carbide particle powder according to any one of 1 to 5 above. 7. Reacting boron carbide particles with glycidol 1. A method for producing modified boron carbide particles, at least a portion of whose surface is modified with polyglycerol, comprising: 8. Producing boron carbide particles using pulsed laser melting 8. A method for producing modified boron carbide particles according to claim 7, comprising: [Effects of the Invention]

[0010] The modified boron carbide particle powder according to an embodiment of the present invention comprises boron carbide particles, at least some of which have at least a portion of their surfaces modified with polyglycerol. Therefore, the modified boron carbide particle powder according to an embodiment of the present invention exhibits inherently low toxicity, can be administered in a shorter time (having better water solubility or water dispersibility), can accumulate boron at a higher concentration in tumors, can persist in tumors for a long time but can be rapidly removed from the blood, and is therefore suitable for use in boron neutron capture therapy. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 shows an SEM image of the polyglycerol-unmodified boron carbide (10B4C) nanoparticles of Comparative Example 1. [Figure 2] FIG. 2 shows the FTIR spectra of the 10B4C-PG nanoparticles of Example 1 and the 10B4C nanoparticles of Comparative Example 1. [Figure 3] FIG. 3 shows the mass change with temperature (TGA) for the 10B4C-PG nanoparticles of Example 1 and the 10B4C nanoparticles of Comparative Example 1. [Figure 4] FIG. 4 shows the concentration of 10B4C-PG nanoparticles of Example 3 in major tissues, tumor, and blood, versus time from injection of 10B4C-PG nanoparticles. [Figure 5] Figure 5 shows the 10B concentration in the tumor (T), the 10B concentration in the blood (B), and the ratio of the 10B concentration in the tumor (T) to the 10B concentration in the blood (B) (T / B ratio) for the 10B4C-PG nanoparticles of Example 3 versus time from 10B4C-PG nanoparticle injection. [Figure 6] FIG. 6 shows the in vivo BCNT results (tumor size) for the 10B4C-PG nanoparticles of Example 1. [Figure 7] FIG. 7 shows the in vivo BCNT results (mouse body weight) for the 10B4C-PG nanoparticles of Example 1. [Figure 8] Figure 8 shows the 10B concentration in the tumor (T), the 10B concentration in the blood (B), and the ratio of the 10B concentration in the tumor (T) to the 10B concentration in the blood (B) (T / B ratio) for the 10B4C-PG nanoparticles of Example 1 versus time from 10B4C-PG nanoparticle injection. [Figure 9] FIG. 9 shows images of sections of tumor tissue taken 24 or 48 hours after injection of the 10B4C-PG nanoparticles of Example 1, observed using a transmission electron microscope (TEM). DETAILED DESCRIPTION OF THE INVENTION

[0012] In one aspect, the present specification provides a boron carbide particle powder comprising boron carbide particles, at least some of the surfaces of which are modified with polyglycerol. Note that in this specification, the term "particle powder" refers to an aggregate of particles (a powder or a plurality of particles) and may also be simply referred to as "particles." In this specification, "boron carbide particles" refers to an inorganic material made of carbon and boron, and its composition formula is generally expressed as BC, and is not particularly limited as long as the modified boron carbide particle powder intended by the present invention can be obtained.

[0013] The boron in boron carbide is mainly 10 B and 11 The boron in the particles consists of B and comes from natural boron carbide. 11 B is approximately 80.1%, 10 As long as the modified boron carbide particle powder and the neutron capture therapy drug containing the same that are the object of the present invention can be obtained, natural boron carbide can be used as the boron carbide, and the amount of boron in the boron carbide can be 10 The B content may be, for example, about 19.9%. 10 The content of B is preferably 50% or more, more preferably 75% or more, even more preferably 90% or more, and even more preferably 98% or more. 10 When the B content is 50% or more, when used for boron neutron capture therapy, 10 The higher B content provides better neutron capture capability, enabling more efficient boron neutron capture therapy.

[0014] The average particle size of the boron carbide particles is, for example, less than 1000 nm, less than 900 nm, less than 800 nm, less than 700 nm, less than 600 nm, preferably less than 500 nm, preferably less than 400 nm, more preferably less than 300 nm, more preferably less than 250 nm, even more preferably less than 200 nm, even more preferably less than 150 nm, and even more preferably less than 100 nm.

[0015] The average particle size of the boron carbide particles may be, for example, less than 0.5 nm, or may be 0.5 nm or more, preferably 1.0 nm or more, preferably 1.5 nm or more, preferably 2.0 nm or more, more preferably 2.5 nm or more, more preferably 3.0 nm or more, more preferably 3.5 nm or more, even more preferably 4.0 nm or more, even more preferably 5.0 nm or more, even more preferably 6.0 nm or more, even more preferably 7.0 nm or more, even more preferably 8.0 nm or more, and even more preferably 10 nm or more.

[0016] The average particle size of the boron carbide particles is, for example, 0.5 nm or more and less than 1000 nm, preferably 1.0 nm or more and less than 500 nm, more preferably 2.5 nm or more and less than 300 nm, even more preferably 5.0 nm or more and less than 200 nm, even more preferably 5.0 nm or more and less than 150 nm, and even more preferably 10 nm or more and less than 100 nm. When the average particle size of the boron carbide particles is less than 1000 nm, the particles have lower toxicity and better water solubility or water dispersibility, and when the average particle size is 2.5 nm or more but less than 300 nm, the particles have an excellent balance of lower toxicity, better water solubility or water dispersibility, a relatively longer retention time in the blood, and easier uptake by tumor tissue. The average particle size of the boron carbide particles can be measured, for example, by SEM observation as described in the Examples. More specifically, the major and minor diameters of 100 particles in the SEM image were measured to obtain the average values ​​of the major and minor diameters. The average major and minor diameters were then averaged to obtain the average particle size.

[0017] The boron carbide particles have at least a portion of their surface modified with polyglycerol. As used herein, the term "polyglycerol" refers to a substance having many "glycerol (or glycerin)" units and many hydroxyl groups, and is not particularly limited as long as the modified boron carbide particle powder intended by the present invention can be obtained. Since the boron carbide particles have at least a portion of their surface modified with polyglycerol, they are essentially less toxic, more water-soluble or water-dispersible, can accumulate boron at higher concentrations within tumors, and can persist in tumors for a long time while being rapidly removed from the blood, making them suitable for use in boron neutron capture therapy.

[0018] An example of a "glycerol (or glycerin)" unit is the chemical structure shown in the following chemical formula (I).

[0019] Chemical formula 1: [-CH2-CH(CH2OH)-O-] [-O-CH2-CH(CH2OH)-], and [-CH2-CH(OH)-CH2-O-]

[0020] The polyglycerol may contain other units, such as, but not necessarily, ethyleneoxy, propyleneoxy, etc., as long as the modified boron carbide particle powder desired by the present invention can be obtained. The polyglycerol may also contain other substances, such as, but not necessarily, hydrophilic substances, such as, but not necessarily, polyethylene glycol, polypropylene glycol, and polyethylene glycol / polypropylene glycol copolymers, as long as the modified boron carbide particle powder desired by the present invention can be obtained.

[0021] The polyglycerol content is preferably 0.1% by mass or more and 99.9% by mass or less, more preferably 1% by mass or more and 99% by mass or less, even more preferably 5% by mass or more and 90% by mass or less, even more preferably 7% by mass or more and 85% by mass or less, and even more preferably 10% by mass or more and 80% by mass or less, based on the modified boron carbide particle powder (100% by mass). When the amount of polyglycerol is 0.1% by mass or more and 99.9% by mass or less, based on the modified boron carbide particle powder (100% by mass), the modified boron carbide particle powder can have the advantageous effect of having suitable water solubility and size.

[0022] The median diameter of the modified boron carbide particles according to an embodiment of the present invention is, for example, preferably 1000 nm or less, preferably 900 nm or less, preferably 800 nm or less, preferably 700 nm or less, preferably 600 nm or less, more preferably 500 nm or less, more preferably 400 nm or less, even more preferably 300 nm or less, even more preferably 250 nm or less, even more preferably 200 nm or less, even more preferably 150 nm or less, and even more preferably 100 nm or less.

[0023] The median diameter of the modified boron carbide particles is, for example, preferably greater than 0.5 nm, more preferably greater than 1.0 nm, more preferably greater than 1.5 nm, more preferably greater than 2.0 nm, even more preferably greater than 2.5 nm, even more preferably greater than 3.0 nm, even more preferably greater than 3.5 nm, even more preferably greater than 4.0 nm, even more preferably greater than 5.0 nm, even more preferably greater than 6.0 nm, even more preferably greater than 7.0 nm, even more preferably greater than 8.0 nm, and even more preferably greater than 10 nm.

[0024] The median diameter of the modified boron carbide particles according to an embodiment of the present invention is preferably greater than 0.5 nm and less than 1000 nm, more preferably greater than 1.0 nm and less than 500 nm, even more preferably greater than 2.5 nm and less than 300 nm, even more preferably greater than 5.0 nm and less than 200 nm, even more preferably greater than 5.0 nm and less than 150 nm, and even more preferably greater than 10 nm and less than 100 nm. When the median diameter of the modified boron carbide particle powder is greater than 0.5 nm and less than 1000 nm, it has lower toxicity and better water solubility or water dispersibility, and when the median diameter is greater than 2.5 nm and less than 300 nm, it has lower toxicity and better water solubility or water dispersibility, and the modified boron carbide particle powder has an excellent balance of being more easily taken up by tumor tissue. The median diameter of the modified boron carbide particles can be measured, for example, using dynamic light scattering (DLS) as described in the Examples.

[0025] The modified boron carbide particles of the present invention preferably have a spherical shape. The shape can be observed, for example, using a TEM as described in the Examples. When the modified boron carbide particles have a spherical shape, the surface chemical modification is more uniform, which has the advantageous effect of improving water solubility or water dispersibility. The ratio of the length of the longest axis (major axis) to the length of the shortest axis (minor axis) of a particle in a TEM image (major axis length / minor axis length) is preferably 10 or less, more preferably 5 or less, even more preferably 3 or less, and even more preferably 2 or less. When the ratio (major axis length / minor axis length) is 10 or less, the surface chemical modification is more uniform and the water solubility or water dispersibility is superior, and when the ratio is 3 or less, the surface chemical modification is even more uniform and the water solubility or water dispersibility is even superior, which is an advantageous effect.

[0026] In another aspect, the present invention provides a neutron capture therapy drug containing the modified boron carbide particle powder according to an embodiment of the present invention. The drug can have various forms, and the form is not particularly limited, as long as it can be used for neutron capture therapy. Examples of the form include a suspension in water, a dispersion in water, a suspension in phosphate buffered saline, a dispersion in phosphate buffered saline, other suspensions and dispersions, a solid, a gel, etc.

[0027] The drug may contain various additives in addition to the modified boron carbide particles according to an embodiment of the present invention, as long as the drug can be used in neutron capture therapy. The additives are not particularly limited. Examples of such additives include anticancer drugs, photosensitizers, solubilizing agents, surfactants, lipids, carbohydrates, proteins, polymers, and biomaterials.

[0028] The drug preferably contains 0.1 to 100 mass %, more preferably 1 to 80 mass %, even more preferably 5 to 60 mass %, and even more preferably 10 to 50 mass % of the modified boron carbide particles of the present invention. When the drug contains 0.1 to 100 mass % of the modified boron carbide particles of the present invention, the drug can be injected in a more stable dispersed state. When the drug contains 5 to 60 mass %, the drug can be injected in a more stable dispersed state and other functions can be added by adding various additives such as those described above. When the drug contains 10 to 50 mass %, the drug can be injected in a more stable dispersed state and other functions can be added and improved by adding various additives such as those described above, resulting in an excellent balance of these.

[0029] The neutron capture therapy drug according to an embodiment of the present invention has the advantageous effects of being inherently less toxic, being able to be administered in a shorter time (having better water solubility or water dispersibility), being able to accumulate boron at a higher concentration within the tumor, and being able to remain in the tumor for a long period of time while being quickly removed from the blood.

[0030] The neutron capture therapy drug according to an embodiment of the present invention comprises: 10The B concentration may be, for example, 0.1 mg / mL or more, preferably 0.5 mg / mL or more, more preferably 1 mg / mL or more, even more preferably 2 mg / mL or more, and even more preferably 5 mg / mL or more. 10 It can be used as a drug with a relatively high concentration of B. Therefore, the administration time can be shortened.

[0031] The neutron capture therapy drug of the embodiment of the present invention may contain, for example, 0.01 mg [ 10 B] / kg or more, and 0.1 mg [ 10 B] / kg, and 0.5 mg [ 10 B] / kg, and 1 mg [ 10 It is more preferred to use it at a dosage of [B] / kg.

[0032] The neutron capture therapy drug of the embodiment of the present invention can accumulate boron at a higher concentration in tumors, and 10 The B concentration (wt / wt) 24 hours after drug injection can be, for example, 1 ppm or more, preferably 3 ppm or more, more preferably 6 ppm or more, even more preferably 10 ppm or more, and even more preferably 20 ppm or more. 10 The B concentration can be measured by the method described in the Examples.

[0033] The neutron capture therapy drugs of the present invention can persist in tumors for a long time, but can be rapidly cleared from the blood, resulting in tumor growth. 10 B concentration (T) and blood 10 The ratio to the B concentration (B) (T / B ratio) 24 hours after drug injection is, for example, 0.5 or more, preferably 1 or more, more preferably 2 or more, even more preferably 3 or more, and even more preferably 4 or more. The T / B ratio can be measured by the method described in the Examples.

[0034] The method for producing the modified boron carbide particles according to an embodiment of the present invention is not particularly limited as long as it is possible to produce the particles. In a preferred aspect, the present invention relates to a method for producing a boron carbide particle by reacting glycidol with the boron carbide particle. The present invention provides a method for producing modified boron carbide particles, at least a portion of whose surface is modified with polyglycerol, comprising: (a) reacting the boron carbide particles with glycidol in a reaction system in which the boron carbide particles react ...

[0035] [ka]

[0036] The reaction between boron carbide particles and glycidol is not particularly limited as long as the reaction is actually possible and at least a portion of the boron carbide particles can be modified with polyglycerol. Examples of the reaction include ultrasonic irradiation, using an epoxy ring polymerization catalyst, appropriate heating, UV light irradiation, using a solvent, and dropping glycidol. For example, reaction conditions such as reaction time, reaction temperature, and reaction concentration can be appropriately selected.

[0037] In the method for producing modified boron carbide particles according to an embodiment of the present invention, the method for producing the boron carbide particles by reacting with glycidol is not particularly limited, as long as the desired modified boron carbide particles can be obtained. For example, the boron carbide particles can be produced using pulsed laser melting, chemical vapor deposition, arc discharge, coprecipitation (liquid phase synthesis), ball mill (solid phase synthesis), etc. It is preferable to produce the boron carbide particles using pulsed laser melting. The boron carbide particles may be used after adjusting the particle size, and the particle size can be adjusted using, for example, elutriation, chromatography, centrifugation, or other methods.

[0038] The method for producing modified boron carbide particles according to an embodiment of the present invention can be used as is as a method for producing a powder of boron carbide particles, which contains the above-described boron carbide particles, and in which at least a portion of the surface of at least some of the boron carbide particles is modified with polyglycerol. Reacting boron carbide particles with glycidol The present invention also provides a boron carbide particle powder containing boron carbide particles, at least some of which have at least a portion of the surface modified with polyglycerol, and a method for producing the modified boron carbide particles. The above descriptions regarding the method for reacting the boron carbide particles with glycidol, the reaction conditions, the method for producing the boron carbide particles, etc. can be referenced.

[0039] The present invention can provide neutron capture therapy using the neutron capture therapy agent of the embodiment of the present invention. [Example]

[0040] EXAMPLES Hereinafter, the present invention will be specifically and in detail explained using examples and comparative examples, but these examples are merely one embodiment of the present invention, and the present invention is not limited to these examples in any way. In the examples, unless otherwise specified, parts by weight and percentages by weight are based on the parts not taking into account the solvent.

[0041] Example 1. Polyglycerol-modified boron carbide ( 10 B 4 Preparation of C-PG nanoparticles in ethyl acetate 10 From B, using pulsed laser melting method, 10 B4C is synthesized and 10 By centrifuging B4C, 10 Separating nanoparticles of BC and boron carbide ( 10Centrifugation was performed using Avanti JE (trade name) manufactured by Beckman Coulter. SEM observation confirmed spherical nanoparticles with an average particle size of approximately 60 nm (see Figure 1). SEM observation was performed using an S-4800 scanning electron microscope manufactured by Hitachi High-Technologies Corporation. Note that this polyglycerol-unmodified boron carbide ( 10 The B4C) nanoparticles are also referred to as boron carbide nanoparticles of Comparative Example 1.

[0042] Boron carbide ( 10 Glycidol (10 mL) per 50 mg of B4C nanoparticles was added to a round-bottom flask, mixed, and bath sonicated for 15-30 minutes until the nanoparticles were uniformly dispersed. Bath sonication was performed using a Branson 5800 (trade name) at 20°C. The mixture was then stirred at 140°C for 2 hours to obtain a suspension. The resulting suspension was centrifuged at 50400g for 30 minutes to obtain particles. The particles were washed 3-4 times with MiliQ water until the supernatant was clear and transparent without any Tyndall phenomenon, and the resulting polyglycerol-modified boron carbide (B4C) nanoparticles of Example 1 were obtained. 10 The chemical reaction is shown in the following formula: Hyperbranched polyglycerol (PG) was obtained by ring-opening polymerization of glycidol. 10 Schematic of surface modification of B4C.

[0043] [ka]

[0044] Example 1 10 The dispersibility of B4C-PG nanoparticles in water and phosphate buffered saline was investigated. First, the dispersibility in water was investigated by measuring 15 mg of B4C-PG nanoparticles in water and phosphate buffered saline. 10BC-PG nanoparticles were added to 1.00 mL of water, ultrasonicated, and left to stand for two days. After confirming that no precipitate had formed, the dispersibility in water was determined to be 15 mg / mL. Next, 0.11 mL of 10x concentrated phosphate buffered saline was added to the aqueous dispersion, ultrasonicated, and left to stand for two days. After confirming that no precipitate had formed, the dispersibility in phosphate buffered saline was determined to be 13 mg / mL.

[0045] The nanoparticles of Example 1 were analyzed using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and dynamic light scattering (DLS) to determine the structure of the nanoparticles, the amount of polyglycerol layer, and the hydrodynamic diameter, respectively. IR measurements were performed using an IR Prestige-21 (trade name) manufactured by Shimadzu Corporation. -1 4cm in the wave number range -1 The FTIR spectrum was obtained by collecting 32 scans at a resolution of 1000 s.p.m. FIG. 2 shows the structure of Example 1. 10 B4C-PG nanoparticles and Comparative Example 1 10 The FTIR spectrum of B4C nanoparticles is shown. 10 The BC nanoparticles exhibited a peak at 1130 cm, which is attributed to icosahedral BC. -1 and 1612cm -1 The peak of 10 On the surface of B4C 10 1415 cm for BO vibration -1 The peaks near 10 B and 11 Compared with B4C, which contains B (natural abundances of 19% and 81%, respectively), 10 Because the atomic weight of B in BC is lighter, 10 All peaks of B4C are shifted to higher wavenumbers. This indicates that the nanoparticles used in Example 1 10 B indicates that it is enriched (enhanced). 10 The FTIR spectrum of BC-PG nanoparticles shows the peaks at 1140 cm, which correspond to C-O-C, C-H, and C-H stretching, respectively. -1 , 2900cm -1 and 3500 cm-1 A typical peak of polyglycerol appears around this area. 10 Polyglycerol coating on the B4C surface.

[0046] TGA was performed using a Q-50 analyzer manufactured by TA Instruments under a nitrogen atmosphere, heating from room temperature to 600°C at a heating rate of 20°C / min. FIG. 3 shows the structure of Example 1. 10 B4C-PG nanoparticles and Comparative Example 1 10 The mass change with temperature for B4C nanoparticles is shown. 10 The polyglycerol layer in the B4C-PG nanoparticles was approximately 73% by mass.

[0047] DLS was performed five times on each sample using a Microtrac Nanotrac UPA-UT151 system in number mode. 10 The median diameter (d50) of the B4C nanoparticles was 62.1 nm, 10 The median diameter of the B4C-PG nanoparticles increased to 72.5 nm. 10 The thickness of the polyglycerol layer of the B4C-PG nanoparticles is estimated to be 5.2 nm.

[0048] Polyglycerol-modified boron carbide ( 10 B 4 Preparation of C-PG nanoparticles Using the same method as described in Example 1, the same methods as in Examples 2 to 4 were used. 10 B4C-PG nanoparticles were produced. The results are shown in Table 1 below together with the results of Example 1. 10 The polyglycerol layer was removed from the B4C-PG nanoparticles. 10 BC nanoparticles are shown.

[0049] [Table 1]

[0050] Polyglycerol-modified boron carbide ( 10 B 4 Pharmacokinetics of C-PG nanoparticles From the perspective of application to in vivo BNCT, which will be described later, 10 Pharmacokinetic studies of B4C-PG nanoparticles were carried out as follows. Animal and tumor models Eight to 11-week-old female BALB / c mice were housed in the KUR Animal Care Facility (Kyoto University, Kumatori Campus) with free access to water and standard food. All animal experiments were conducted in accordance with standards approved by the Kyoto University Ethics Committee. Approximately 1 × 10 6 CT26 cells were implanted subcutaneously into the right leg of BALB / c mice 7–9 days before injection of the nanoformulation. Mice were maintained, handled, and housed in pathogen-free conditions in accordance with the guidelines of the Science Council of Japan. All animal experiments were performed in accordance with the standards of the Experimental Animal Center of Kyoto University.

[0051] Pharmacokinetic experiments After the tumor's long axis exceeds 10 mm, 10 A PBS dispersion (200 μL) of B4C-PG nanoparticles was injected into tumor-bearing BALB / c mice via the tail vein. After a certain period of time, the mice were euthanized, and the boron content in the blood, tumor, and organs (liver, spleen, and kidney) was evaluated. The samples were placed in Teflon tubes, and the boron content of each sample was measured. 10 The B concentration was measured by a rapid gamma-ray microanalysis system and was expressed as ppm-order concentrations (μg[ 10 B] / g [biomaterial]) was obtained (see Non-Patent Document 7).

[0052] Example 3 10 B 4 Pharmacokinetics of C-PG nanoparticles Example of 10Pharmacokinetics experiments of B4C-PG nanoparticles 10 A PBS dispersion of B4C-PG nanoparticles (200 μL) was added to 30.9 mg [ 10 The injection was performed at a dose of [B] / kg[mouse]. Figure 4 shows the results of Example 3 in major tissues, tumors, and blood. 10 The concentration of BC-PG nanoparticles was 10 The results are shown against time after injection of B4C-PG nanoparticles in the spleen, liver, and blood. 10 B concentrations in the kidney and tumor 10 B concentrations were much higher in the spleen and liver at an early stage. 10 The B concentration remained almost constant up to 48 hours, but the tumor 10 The B concentration gradually increased, reached a maximum at 24 hours (36.7 ppm), and remained above 20 ppm up to 48 hours. Figure 5 shows the tumor (T) 10 B concentration in blood (B) 10 B concentration and tumor (T) 10 B concentration and blood (B) 10 The ratio of the B concentration (T / B ratio) is 10 The graph shows the time from injection of B4C-PG nanoparticles. In BNCT for cancer, the tumor (T) 10 It is more preferable that the B concentration is 20 ppm or more, and in FIG. 5, this condition was met for a fairly long period of time, from 18 to 48 hours. Furthermore, no mice (n=6) died over the 48 hours, so the results of Example 3 were 10 B4C-PG nanoparticles did not exhibit acute toxicity.

[0053] Adequate for BNCT 10 B concentration levels were maintained in the tumor for 30 hours between 18 and 48 hours, while in the blood 10 The B concentration gradually decreased with a half-life of 7.3 hours. Therefore, the T / B ratio increased over time and reached 4.4 at 48 hours, which satisfied the T / B ratio of 3 or more, which is considered preferable in BNCT. 10From the time showing the B concentration (36.7 ppm) and the time showing the maximum T / B ratio, 10 It was decided to irradiate the B4C-PG nanoparticles with neutrons at 24 and 48 hours after injection.

[0054] Polyglycerol-modified boron carbide ( 10 B 4 In vivo BNCT of C-PG nanoparticles 10 In vivo BNCT of B4C-PG nanoparticles was performed as follows. Using the same method as described in the pharmacokinetics study, 10 B4C-PG nanoparticles were injected into mice. 10 24 or 48 hours after injection of B4C-PG nanoparticles, the mice were placed in an acrylic holder with a circular hole in the center and irradiated with neutrons. 6 LiF (96% 6 The tumor-bearing thigh was stretched over the hole to block neutrons at 5 × 10 9 cm -2 s -1 for 12 minutes at a fluence of 6.5 x 10 8 cm -2 s -1 The mice were irradiated with neutrons at a fluence of 1000 keV for 60 minutes in a Kyoto University research reactor (KUR). The day of neutron irradiation was designated as day 0. The tumor volumes of all mice were continuously measured by the same observer using the same caliper throughout the experiment. Tumor volumes were calculated according to the following formula 1 and statistically analyzed.

[0055] Tumor volume calculation Tumor volume was calculated based on the following formula 1. Formula 1: Volume = (major axis x minor axis) 2 ) / 2 The same balance was used to measure the weight changes of the mice. When the tumor growth data were statistically analyzed, all data were normalized using the following formula 2: Formula 2:V Relative = (Volume[Group x, Day n]) / (Volume[Group x, Day 0])

[0056] Analysis of Pharmacokinetic Data Data analysis was performed using Graphpad Prism 9 (Graphpad Software, Inc., San Diego, CA). Blood concentration data were fitted using a one-phase decay model, which considers the concentration curve as the sum of exponential decays. The decay of nanoparticle blood concentration was approximated by the following equation (3): Formula 3:C t = (C0 - Plateau) × e -kt + Plateau [t is time (h), C t is the concentration (μg[ 10 B] / g[blood]), k is the rate constant (h -1 ) indicates.

[0057] Example 1 10 B 4 In vivo BNCT of C-PG nanoparticles 34.3mg[ 10 B] / kg [mouse], 10 B4C-PG nanoparticles were injected intravenously into each mouse. 10 24 or 48 hours after injection of B4C-PG nanoparticles, neutrons were irradiated at 3.6 × 10 12 cm -2 After neutron irradiation, tumor size and body weight were monitored for 29 days. In parallel, the same method as described in the pharmacokinetics experiment above was used to measure the intratumoral 10 B concentration and blood 10 B concentration, 10 Measurements were taken 8, 24 and 48 hours after injection of B4C-PG nanoparticles.

[0058] 6 and 7 show the results of Example 1. 10 In vivo BCNT results for B4C-PG nanoparticles are shown. BCNT24h and BCNT48h in FIG. 6 are the same as those in Example 1. 10 Neutron irradiation was performed 24 or 48 hours after the injection of B4C-PG nanoparticles, and the relative tumor size versus the number of days from that time point is shown. 10 The hot control, which was not injected with B4C-PG nanoparticles and not irradiated with neutrons, was the same as in Example 1. 10 The injection control was the same as in Example 1, in which no B4C-PG nanoparticles were injected but neutrons were irradiated. 10 The condition is shown below: B4C-PG nanoparticles are injected but neutrons are not irradiated. The suppression of tumor growth by neutron irradiation can be seen by comparing the cold control, injection control, and hot control. It can be seen that 24h and 48h BNCT suppressed tumor size more efficiently than the hot control. After 29 days, 24h and 48h BNCT suppressed tumor size by 13% and 12%, respectively, compared to the cold control. After 29 days, 24h and 48h BNCT suppressed tumor size by 20% and 19%, respectively, compared to the hot control.

[0059] BCNT24h and BCNT48h in FIG. 7 are the same as those in Example 1. 10 The mice were irradiated with neutrons 24 or 48 hours after injection of B4C-PG nanoparticles, and the relative weights of the mice over the number of days since that time are shown. The cold control, hot control, and injection control are experimental conditions similar to those in Figure 6. It can also be seen in Figure 7 that neutron irradiation suppresses weight change. As in Figure 6, BNCT 24h and BNCT 48h showed that tumor growth was more efficiently suppressed than the hot control.

[0060] FIG. 8 shows the first embodiment. 10 B4C-PG nanoparticles were injected into mice, and the tumor (T) was measured 8, 24, and 48 hours later. 10 B concentration in blood (B)10 B concentration and tumor (T) 10 B concentration and blood (B) 10 The ratio of the T / B concentration to the B concentration (T / B ratio) is shown. 10 The B4C-PG nanoparticles were prepared as in Example 3 shown in FIG. 10 The pharmacokinetics of B4C-PG nanoparticles was similar to that of B4C-PG nanoparticles. 10 The B concentration was 20 ppm or more from 24 to 48 hours after injection. Furthermore, no mice (n=7) died over the 48 hours. 10 It was concluded that BC-PG nanoparticles were not acutely toxic.

[0061] Example 2 10 B 4 In vivo BNCT of C-PG nanoparticles 27.9mg[ 10 B] / kg [mouse], 10 B4C-PG nanoparticles were injected intravenously into each mouse. 10 24 or 48 hours after injection of B4C-PG nanoparticles, neutrons were irradiated at 2.3 × 10 12 cm -2 After neutron irradiation, tumor size and body weight were monitored for 20 days. In parallel, the same method as described in the pharmacokinetics experiment above was used to measure the intratumoral 10 B concentration and blood 10 B concentration, 10 Measurements were taken 8, 24 and 48 hours after injection of B4C-PG nanoparticles.

[0062] The same trends as those shown in Figs. 6 and 7 were observed in Example 2. 10This was also observed in in vivo BNCT of B4C-PG nanoparticles. Here, experiments were conducted under the same conditions as in Figures 6 and 7, with cold control, injection control, hot control, BNCT24, and BNCT48. The hot control suppressed tumor size more than the cold control and injection control. BNCT24h and BNCT48h suppressed tumor size even more than the hot control. After 20 days, BNCT24h and BNCT48h suppressed tumor size by 52% and 39%, respectively, compared to the cold control. After 20 days, BNCT24h and BNCT48h suppressed tumor size by 63% and 48%, respectively, compared to the hot control.

[0063] Example 1 10 B 4 TEM observation of tumors 24 and 48 hours after injection of C-PG nanoparticles into mice 10 To further understand the BCNTs based on BC-PG nanoparticles, 10 Sections of tumor tissues taken 24 or 48 hours after injection of B4C-PG nanoparticles were observed using a transmission electron microscope (TEM). FIG. 9a shows the structure of Example 1. 10 9b shows a TEM image of a tumor tissue section taken 24 hours after injection of B4C-PG nanoparticles, and FIG. 9c shows a TEM image of a tumor tissue section taken 24 hours after injection of B4C-PG nanoparticles. 10 TEM images of tumor tissue sections taken 48 hours after injection of B4C-PG nanoparticles are shown. In both Figures 9a and 9b, numerous particles were observed as black dots. This indicates that B4C-PG nanoparticles were present in the tumor tissue, as confirmed by the pharmacokinetics experiment. 10 It supports the accumulation of B. [Industrial Applicability]

[0064] The modified boron carbide particle powder of an embodiment of the present invention comprises boron carbide particles, at least some of the surfaces of which have been modified with polyglycerol. Therefore, a drug comprising the modified boron carbide particle powder of an embodiment of the present invention exhibits advantageous effects such as inherently low toxicity, shorter administration time (superior water solubility or water dispersibility), higher boron accumulation in tumors, and long-term persistence in tumors while being rapidly removed from the blood, making it suitable for use in boron neutron capture therapy.

Claims

1. A boron carbide particle powder comprising boron carbide particles, at least a portion of the surface of at least some of the boron carbide particles being modified with polyglycerol by a chemical reaction.

2. 2. The modified boron carbide particle powder of claim 1, wherein the median diameter is greater than 0.5 nm and less than or equal to 1000 nm.

3. 3. The modified boron carbide particle powder according to claim 1, wherein the polyglycerol content is 0.1% by mass or more and 99.9% by mass or less, based on the modified boron carbide particles (100% by mass).

4. 4. The modified boron carbide particle powder according to claim 1, wherein the average particle size of the boron carbide particles is less than 1000 nm.

5. The modified boron carbide particles powder according to any one of claims 1 to 4, which have a spherical shape.

6. A neutron capture therapy drug comprising the modified boron carbide particle powder according to any one of claims 1 to 5.

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