JP7619787B2 - Cell killing agents, disinfecting compositions and methods for physically destroying target cells in vitro - Google Patents

Description

The present invention relates to cell killing agents , germicidal compositions and methods for physically destroying target cells in vitro.

Chemotherapy is the most common conventional cancer treatment. In chemotherapy, anticancer drugs are administered to cancer cells that are dividing and proliferating, but they also affect fast-dividing normal cells, which can easily cause side effects such as nausea, hair loss, and a decrease in white blood cells.

In addition, antibiotics and antiviral drugs are used to treat infectious diseases against pathogenic bacteria and viruses. However, genetic mutations occur frequently in these pathogenic bacteria and viruses, and there is a risk that antibiotics and antiviral drugs will lose their effectiveness if drug-resistant strains emerge.

As an alternative to the above-mentioned drug-based treatments, photocatalytic treatments are being considered. For example, Patent Document 1 discloses an antitumor agent that contains titanium oxide particles and a nonionic water-soluble polymer bound to the surface of the titanium oxide particles via various functional groups. Patent Document 1 proposes a mechanism in which the titanium oxide particles are activated to generate radical species by irradiating the antitumor agent with ultrasound or ultraviolet light after administration to a cancer patient, and the generated radical species kill cancer cells.

JP 2008-201797 A

The present invention has been made in consideration of the above circumstances, and provides a cell killing agent that suppresses side effects and the emergence of drug-resistant bacteria, and can more effectively and efficiently kill cancer cells and various pathogenic bacteria. It also provides a pharmaceutical composition, a supplement composition, a sterilization composition, and a method for physically destroying target cells in vitro, which use the cell killing agent.

That is, the present invention includes the following aspects.
(1) Particles that are photocatalysts;
A substance provided on the surface of the particle that specifically recognizes a target cell;
A modifying substance provided on the surface of the particle and having cell permeability to the target cell,
the particles are made of a compound semiconductor;
the compound semiconductor includes a first semiconductor and a second semiconductor;
the particle has a core-shell structure in which one of the first semiconductor and the second semiconductor is a core and the other is a shell,
The band structure of the grain is type II,
the highest energy level in the valence band of the first semiconductor is more positive than the oxidation potential of water;
A cell-killing agent, wherein the lowest energy level in the conduction band of said second semiconductor is more negative than the reduction potential of water.
(2) The cell-killing agent according to (1), wherein a portion of the core is exposed at the surface of the particle.
(3) The cell killing agent according to (1) or (2), wherein the compound semiconductor is at least one selected from the group consisting of metal oxides, metal nitrides, metal oxynitrides, metal carbonitrides, II-VI group semiconductors, and III-V group semiconductors.
(4) The cell killing agent according to any one of (1) to (3), wherein the optical absorption edge of the first semiconductor is 700 nm or more and 1000 nm or less.
(5) The cell killing agent according to any one of (1) to (4), wherein the average particle size of the particles is more than 1 nm and not more than 1000 nm.
(6) The cell killing agent according to any one of (1) to (5), wherein the average particle diameter of the core of the particle is 1 nm or more and 20 nm or less.
( 7 ) A sterilizing composition comprising the cell killing agent according to any one of (1) to (6).
( 8 ) A method for physically destroying target cells in vitro, comprising:
Contacting a target cell with the cell killing agent according to any one of (1) to (6) above, and allowing the cell killing agent to be incorporated into the target cell;
Irradiating the target cells into which the cytotoxic agent has been taken with light, causing a photocatalyst contained in the cytotoxic agent to decompose water contained within the target cells by the energy of the light, generate hydrogen and oxygen, and then expanding the target cells with the hydrogen and oxygen, thereby physically destroying them;
The method includes:
( 9 ) The method according to ( 8 ), wherein the target cell is a pathogenic bacterium.

The cell killing agent of the above embodiment can suppress side effects and the emergence of drug-resistant bacteria, and can provide a cell killing agent that can kill cancer cells and various pathogenic bacteria more effectively and efficiently.

FIG. 1 is a diagram showing the structure of a photocatalyst according to a first embodiment of the present invention. FIG. 2 is a diagram showing the band structure of the photocatalyst according to the first embodiment of the present invention. FIG. 4 is a diagram showing the structure of a photocatalyst according to a second embodiment of the present invention. FIG. 4 is a diagram showing the band structure of a photocatalyst according to a second embodiment of the present invention. FIG. 4 is a diagram showing the structure of a photocatalyst according to a third embodiment of the present invention. FIG. 11 is a diagram showing the structure of a photocatalyst according to a fourth embodiment of the present invention.

The cell killing agent, pharmaceutical composition, supplement composition, sterilizing composition, and method for physically destroying target cells in vitro according to one embodiment of the present invention (hereinafter abbreviated as "this embodiment") are described in detail below.

<Cell Killing Agents>
The cell killing agent of the present embodiment contains photocatalyst particles as an active ingredient.

As used herein, "containing as an active ingredient" means containing a therapeutically effective amount of photocatalyst. As used herein, "therapeutically effective amount" means an amount of photocatalyst, or an amount of a combination of photocatalyst and one or more active agents, that, when administered in accordance with a desired therapeutic regimen, induces the biological or medical effect or response desired by a physician, clinician, veterinarian, researcher, or other appropriate professional. A preferred therapeutically effective amount is an amount that ameliorates the symptoms of the disease of interest. A "therapeutically effective amount" also includes a prophylactically effective amount, i.e., an amount suitable for preventing a disease state.

The particles are composed of a compound semiconductor. In this context, "compound semiconductor" means a semiconductor formed by combining two or more elements.

The band structure of the particles is type II.
The type II band structure is composed of a second semiconductor, which is a compound semiconductor having a conduction band located at a level where the probability of electrons generated by light absorption is high, and a first semiconductor, which is a compound semiconductor having a valence band located at a level where the probability of holes generated by light absorption is high. In this embodiment, the compound semiconductor constituting the particle includes the first semiconductor and the second semiconductor. The electrons and holes generated by light absorption are separated between different semiconductors, thereby extending the carrier lifetime. In other words, the type II band structure of the particle can enhance the activity of the photocatalyst.

In the particle, from the highest energy level (quantum level) there is the lowest energy level of the conduction band of the first semiconductor, the lowest energy level of the conduction band of the second semiconductor, the highest energy level of the valence band of the first semiconductor, and the highest energy level of the valence band of the second semiconductor.

The particles have a core-shell structure with either the first or second semiconductor as the core and the other as the shell. Of these, it is preferable to have a core-shell structure with the first semiconductor as the core and the second semiconductor as the shell. This allows cells to expand efficiently.

The first semiconductor constituting the particles is not particularly limited as long as the highest energy level in the valence band is more positive than the oxidation potential of water. The second semiconductor is not particularly limited as long as the lowest energy level in the conduction band is more negative than the reduction potential of water. By using the first semiconductor and the second semiconductor that satisfy such a relationship, the electrons in the conduction band generated by light absorption are used to reduce water (specifically, reduce hydrogen ions derived from water) to generate hydrogen, and the holes in the valence band generated by light absorption are used to oxidize water to generate oxygen. That is, a photocatalyst useful for water decomposition can be configured.
Specific examples of such compound semiconductors include metal oxides, metal nitrides, metal oxynitrides, metal carbonitrides, II-VI group semiconductors, and III-V group semiconductors.
Examples of metal oxides include titanium oxides such as _TiO2 and _SrTiO3 ; tantalum oxides such as _{Ta2O5 and KTaO3} ; ZnO, ZnGaO, _ZrO2 , _Nb2O5 , and the _like .
Examples of metal nitrides include Ta ₃ N ₅ and Nb ₃ N ₅ .
Examples of metal oxynitrides include NbON and TaON.
An example of the metal carbonitride is TaCN.
Examples of II-VI group semiconductors include CdTe, CdSe, ZnSe, and CdS.
Examples of III-V semiconductors include GaN, InGaN, GaP, InP, and GaAs.
Among them, preferred materials for the first semiconductor include _Ta3N5 , _Nb3N5 , TaON, NbON, TaCN, _CdSe , CdS _, and InGaN.
Also, preferred materials for the second semiconductor include metal oxides such as TiO ₂ , SrTiO ₃ , and ZnO.

In the particles, among the compound semiconductors exemplified above, the second semiconductor is preferably formed from a metal oxide. By being formed from a metal oxide, the stability of the particles is improved, and when used in an environment where water is present (i.e., inside the cells of the target cells), deterioration of the semiconductor material can be suppressed, and the durability of the photocatalyst can be improved.

When the cytocidal agent of this embodiment is administered to the body of a subject, it is preferable that the optical absorption edge of the first semiconductor constituting the particles is 700 nm or more, since visible light is easily absorbed by components in the living body and ultraviolet light causes significant damage to cells. By using a photocatalyst composed of a compound semiconductor that absorbs light in the near-infrared region of 700 nm or more, the efficiency of light utilization in the living body is high and damage to normal cells can be minimized. On the other hand, it is preferable that the optical absorption edge of the first semiconductor is 1000 nm or less, since the energy required for water decomposition can be obtained.
Examples of compound semiconductors having an optical absorption edge in the range of 700 nm to 1000 nm include InGaN, NbON, and TaCN.

Among these, in the particles, the combination of the first semiconductor and the second semiconductor (first semiconductor/second semiconductor) is preferably InGaN/TiO ₂ , NbON/TiO ₂ , or TaCN/TiO ₂ .

The average particle size of the particles is not particularly limited as long as it is a size that can be taken up by target cells, but is preferably more than 1 nm and not more than 1000 nm, more preferably more than 1 nm and not more than 500 nm, even more preferably more than 1 nm and not more than 300 nm, and particularly preferably more than 1 nm and not more than 100 nm.
When the average particle size of the particles is equal to or larger than the lower limit, deterioration of the photocatalytic properties due to crystal defects can be suppressed, whereas when the average particle size is equal to or smaller than the upper limit, the particles are easily taken up by target cells.

In addition, the average particle diameter of the core of the particles is not particularly limited as long as the average particle diameter of the particles falls within the above range, but is preferably 1 nm or more and 20 nm or less, more preferably 1 nm or more and 15 nm or less, and even more preferably 1 nm or more and 10 nm or less.
When the average particle size of the core is not less than the above lower limit, deterioration of the photocatalytic properties due to crystal defects can be suppressed, whereas when it is not more than the above upper limit, it is easily taken up by target cells.

The average particle size of the particles can be measured, for example, from a transmission electron microscope (TEM) image, and is obtained by calculating the average value of the measured particle size values of a plurality of particles (for example, about 100 to 500 particles) using known image analysis software. At this time, all particles included in one field of view are measured, and the plurality of fields of view are measured until the number of measurements exceeds a lower limit, and then the measurement is set to end when the lower limit is exceeded.
Alternatively, the average particle size can be estimated by measuring the particle size by dynamic light scattering, analyzing the particle size by photon correlation analysis, or measuring the particle size by small angle scattering, and analyzing the scattering curve using NANO-Solver.
In this specification, the particle size is a circle equivalent diameter.

The average particle size of the cores can be measured, for example, using a dispersion of core particles produced as an intermediate during the production of the photocatalyst, using a method similar to the method for measuring the average particle size of the particles described above.
Alternatively, since the core and shell of a particle are made of different compound semiconductors, if the densities of the materials in these compound semiconductors are different, the particle diameter of the core and the particle diameter of the entire particle can be measured simultaneously based on the difference in electron transmittance.

The particle has a cell-permeable modifying substance (hereinafter sometimes simply referred to as a "modifying substance") and a substance that specifically recognizes target cells (hereinafter sometimes simply referred to as a "specific recognition substance") on its surface. The provision of a cell-permeable modifying substance on the surface of the particle allows the particle to penetrate the cell membrane of the target cell. Furthermore, the provision of a substance that specifically recognizes target cells on the surface of the particle allows the cell killing agent of this embodiment to be efficiently taken up only by the target cells. Note that one or more types of modifying substance and one or more types of specific recognition substance may be used, or one or more types of substance that combines cell permeability and the property of specifically recognizing target cells may be used.

The cell-permeable modifying substance and the substance that specifically recognizes the target cell may be supported on the surface of the particle. Note that, as used herein, "supported" means that the particle and the cell-permeable modifying substance, and the particle and the substance that specifically recognizes the target cell are directly or indirectly bound to each other and are not separated from each other. For example, the cell-permeable modifying substance and the substance that specifically recognizes the target cell can be supported on the surface of the particle via chemical bonding by functional groups such as carboxyl groups, amino groups, thiol groups, and hydroxyl groups, or by physical adsorption.
Alternatively, at least one of the cell-permeable modifying substance and the substance that specifically recognizes a target cell may be in a state in which the entire surface of the particle is covered.

Cells that are targeted by the cell killing agent of this embodiment are not particularly limited, but examples include cancer cells, pathogenic bacteria, etc.

Cancer cells are cells that derive from somatic cells and acquire the ability to proliferate indefinitely, and are malignant neoplasms that invade surrounding tissues or cause metastasis. Examples of cancers from which cancer cells originate include breast cancer (e.g., invasive ductal carcinoma, non-invasive ductal carcinoma, inflammatory breast cancer, etc.), prostate cancer (e.g., hormone-dependent prostate cancer, hormone-independent prostate cancer, etc.), pancreatic cancer (e.g., pancreatic ductal carcinoma, etc.), gastric cancer (e.g., papillary adenocarcinoma, mucinous adenocarcinoma, adenosquamous carcinoma, etc.), lung cancer (e.g., non-small cell lung cancer, small cell lung cancer, malignant mesothelioma, etc.), colon cancer (e.g., gastrointestinal stromal tumor, etc.), rectal cancer (e.g., gastrointestinal stromal tumor, etc.), and large intestine cancer (e.g., cancer, such as familial colorectal cancer, hereditary nonpolyposis colorectal cancer, gastrointestinal stromal tumor, etc.), small intestine cancer (e.g., non-Hodgkin's lymphoma, gastrointestinal stromal tumor, etc.), esophageal cancer, duodenal cancer, tongue cancer, pharyngeal cancer (e.g., nasopharyngeal cancer, oropharyngeal cancer, hypopharyngeal cancer, etc.), head and neck cancer, salivary gland cancer, brain tumors (e.g., pineal astrocytoma, pilocytic astrocytoma, diffuse astrocytoma, anaplastic astrocytoma, etc.), neurilemmoma, liver cancer (e.g., primary liver cancer, extrahepatic bile duct cancer, etc.), kidney cancer (e.g., renal cell carcinoma, transitional cell carcinoma of the renal pelvis and ureter, etc.), gallbladder cancer, pancreatic cancer, endometrial cancer, cervical cancer, ovarian cancer (e.g., epithelial ovarian cancer, extragonadal germ cell tumor, ovarian germ cell tumor, ovarian low malignant potential tumor, etc.), bladder cancer, urethral cancer, skin cancer (e.g., intraocular (eye) melanoma, Merkel cell carcinoma, etc.), hemangioma, malignant lymphoma (e.g., reticulum cell sarcoma, lymphosarcoma, Hodgkin's disease, etc.), melanoma, thyroid cancer (e.g., medullary thyroid carcinoma, etc.), parathyroid cancer, nasal cavity cancer, paranasal sinus cancer, bone tumors (e.g., These include, but are not limited to, osteosarcoma, Ewing's tumor, uterine sarcoma, soft tissue sarcoma, metastatic medulloblastoma, angiofibroma, dermatofibrosarcoma protuberans, retinal sarcoma, penile cancer, testicular tumor, pediatric solid tumor (e.g., Wilms' tumor, pediatric renal tumor, etc.), Kaposi's sarcoma, Kaposi's sarcoma caused by AIDS, maxillary sinus tumor, fibrous histiocytoma, leiomyosarcoma, rhabdomyosarcoma, chronic myeloproliferative disease, leukemia (e.g., acute myeloid leukemia, acute lymphoblastic leukemia, etc.), etc.

Pathogenic bacteria are bacteria that infect humans and animals, such as pets such as dogs and cats, and cause diseases and pathological symptoms. Specific examples of pathogenic bacteria include pathogenic Escherichia coli (including enteropathogenic E. coli, enteroinvasive E. coli, enterotoxigenic E. coli, enterohemorrhagic E. coli, and enteroaggregative E. coli), bacteria of the genus Salmonella, bacteria of the genus Listeria, bacteria of the genus Campylobacter, Staphylococcus aureus, and Clostridium perfringens, but are not limited to these.

Specific examples of cell-permeable modifying substances include polyethylene glycol, membrane-permeable peptides, sugar chains, liposomes, etc.

The substance that specifically recognizes a target cell may be any substance that specifically recognizes a target cell, and specific examples include ligands, antibodies, antibody fragments, aptamers, and the like for receptors present on the surface of the target cell. Antibodies can be produced, for example, by immunizing animals such as mice with antigens, receptors, or fragments thereof present on the surface of the target cell as antigens. Alternatively, antibodies can be produced, for example, by screening a phage library. Examples of antibody fragments include Fv, Fab, and scFv. The above-mentioned antibodies are preferably monoclonal antibodies. Alternatively, they may be commercially available antibodies.

An aptamer is a substance that has a specific binding ability to a target substance. Examples of aptamers include nucleic acid aptamers and peptide aptamers. Nucleic acid aptamers that have a specific binding ability to a target peptide can be selected, for example, by the systematic evolution of ligand by exponential enrichment (SELEX) method. Peptide aptamers that have a specific binding ability to a target peptide can be selected, for example, by the two-hybrid method using yeast.

The cell killing agent of this embodiment contains a photocatalyst having the above-mentioned configuration, and thus can selectively incorporate the photocatalyst into target cells. The incorporated photocatalyst breaks down water in the cells by irradiating light energy, generating hydrogen and oxygen. The generated hydrogen and oxygen become bubbles. The volume of the generated hydrogen and oxygen expands to about 1200 times the volume of the water before decomposition. Since this expanding force is stronger than the force maintaining the cell membrane or cell wall, the target cells can be physically destroyed (burst) by the expanding force.

The amount of hydrogen and oxygen generated in the living body by the photocatalyst (cytotoxic agent) is extremely small, so there is little impact on the human body. In addition, the cytotoxic agent remains in the blood for a certain period of time after administration, and is then excreted from the body. Therefore, it is presumed that the cytotoxic agent of this embodiment suppresses the occurrence of side effects in subjects more than conventional anticancer drugs. In addition, unlike drugs, the cytotoxic agent of this embodiment is less likely to cause drug-resistant bacteria.
Furthermore, the photocatalyst, which is the active ingredient of the cell killing agent of the present embodiment, has a type II band structure and can decompose water more efficiently than a conventional photocatalyst made of titanium oxide, so that the cell killing agent of the present embodiment can kill cancer cells and various pathogenic bacteria more effectively and efficiently.

The cell killing effect of the cell killing agent of this embodiment on target cells can be controlled by the efficiency of the photocatalyst, the number of photocatalysts taken up into the target cell, the intensity of the irradiated light energy, and the speed at which water is decomposed by the photocatalyst.

The efficiency of the photocatalyst and the speed at which water is decomposed by the photocatalyst can be controlled by appropriately selecting the above-mentioned compound semiconductor. Among them, a photocatalyst having a particle core/shell combination of InGaN/ _TiO2 is efficient and can decompose water quickly.

The number of photocatalysts taken up into one target cell can be adjusted as appropriate depending on the average particle size of the particles, but for example, when the average particle size of the particles is greater than 1 nm and less than or equal to 100 nm, the number can be between 1 and 100,000, preferably between 100 and 50,000, and more preferably between 1,000 and 30,000. When the number of photocatalysts taken up is equal to or greater than the lower limit, a more sufficient cell killing effect can be achieved, while when the number is equal to or less than the upper limit, the photocatalysts can be taken up more easily by the target cell.

The intensity of the irradiated light energy can be, for example, 0.01 mW/ ^cm2 or more, preferably 0.1 mW/cm2 or ^more , and more preferably 1 mW/cm2 or ^more . By irradiating the light energy intensity at or above the lower limit, the activity of the photocatalyst can be more fully expressed. On the other hand, the stronger the intensity of the light energy, the higher the activity of the photocatalyst, so the upper limit is not particularly limited.

The photocatalyst may further comprise a labeling substance. By further comprising a labeling substance in the photocatalyst, it is possible to confirm that the excitation light is being irradiated as intended. As the labeling substance, a fluorescent substance that emits fluorescence when exposed to excitation light of the same wavelength as the excitation light of the photocatalyst can be appropriately selected and used. Specific examples of fluorescent substances include known quantum dots, indocyanine green (ICG), protoporphyrin, porphyrin analogues (photosensitizers such as Photofrin and Laserphyrin), 5-aminolevulinic acid (5-ALA; metabolite protoporphyrin IX (PP IX)), near-infrared fluorescent dyes (e.g., Cy5.5, Cy7, AlexaFluor, rhodamine, etc.), and other known fluorescent dyes (e.g., GFP, FITC (Fluorescein), TAMRA, etc.).

[Photocatalyst structure]
The structure of the photocatalyst is described below. In the following description, in a comparison between two types of semiconductors, the semiconductor with the higher energy levels of the valence band and the conduction band is the "first semiconductor" and the semiconductor with the lower energy levels of the valence band and the conduction band is the "second semiconductor."

First Embodiment
Fig. 1A is a diagram showing the structure of a photocatalyst according to a first embodiment of the present invention. As shown in Fig. 1A, a particle 10 is composed of a core 11, a shell 12 covering the core 11, a modifier substance (modifier substance) 13 having cell permeability bound to the particle surface, i.e., the shell, and a substance (specific recognition substance) 14 that specifically recognizes a target cell. The core 11 is formed from a second semiconductor, and the shell 12 is formed from a first semiconductor.

Fig. 1B is a diagram showing the band structure of the photocatalyst according to the first embodiment of the present invention. In Fig. 1B, " _H2 / _H2O " represents the reduction potential of water, " _O2 / _H2O " represents the oxidation potential of water, and "Eg" represents the band gap. In Fig. 1B and subsequent figures, " _H2 / _H2O ", " _O2 / _H2O ", and "Eg" have the same meanings.
In FIG. 1B, particle 10 has a band structure that allows for a charge-separated state with a high probability of electrons being present in the core.

As shown in FIG. 1B, the particle 10 has a type II band structure. When light having an energy equal to or greater than the energy corresponding to the band gap is absorbed in the particle 10, electrons (e ⁻ ) in the valence band are excited to the conduction band in at least one of the first semiconductor and the second semiconductor, generating holes (h ⁺ ) in the valence band and electrons (e ⁻ ) in the conduction band. Then, the electrons in the conduction band of the first semiconductor move to the conduction band of the second semiconductor, and the holes in the valence band of the second semiconductor move to the valence band of the first semiconductor. As a result, the holes (h ⁺ ) are present in large numbers in the valence band of the first semiconductor, i.e., in the shell 12, and the electrons (e ⁻ ) are present in large numbers in the conduction band of the second semiconductor, i.e., in the core 11. The holes (h ⁺ ) are used in an oxidation reaction of water to generate oxygen (O ₂ ), and the electrons (e ⁻ ) are used in a reduction reaction of water to generate hydrogen (H ₂ ).

In the particle 10, the generated holes (h ⁺ ) and electrons (e ^- ) are located in different semiconductors and spatially separated, so that recombination of carriers is suppressed. Therefore, the carrier life is increased, and the energy conversion efficiency in the photocatalyst can be improved. In addition, holes (h ⁺ ) and electrons (e ^- ) are generated in the particle 10, and the distance between the generated holes (h ⁺ ) and electrons (e-) and the surface of the particle 10, which is the active surface of the photocatalyst, is short, so that the holes (h ⁺ ) and electrons (e ^- ) can be efficiently used in the oxidation reaction or reduction reaction of water. In addition, the oxygen (O ₂ ) and hydrogen (H ₂ ) generated by these reactions can effectively kill target cells.

Second Embodiment
Fig. 2A is a diagram showing the structure of a photocatalyst according to a second embodiment of the present invention. As shown in Fig. 2A, a particle 20 is composed of a core 21, a shell 22 covering the core 21, and a modifier substance 23 and a specific recognition substance 24 bound to the particle surface, i.e., the shell. The core 21 is formed of a first semiconductor, and the shell 22 is formed of a second semiconductor.

Figure 2B is a diagram showing the band structure of a photocatalyst according to a second embodiment of the present invention. In Figure 2B, particle 20 has a band structure that allows for a charge separation state in which there is a high probability of holes being present in the core.

As shown in FIG. 2B, the particle 20 has a type II band structure. When light having an energy equal to or greater than the energy corresponding to the band gap is absorbed in the particle 20, electrons (e ⁻ ) in the valence band are excited to the conduction band in at least one of the first semiconductor and the second semiconductor, generating holes (h ⁺ ) in the valence band and electrons (e ⁻ ) in the conduction band. Then, the electrons in the conduction band of the first semiconductor move to the conduction band of the second semiconductor, and the holes in the valence band of the second semiconductor move to the valence band of the first semiconductor. As a result, the holes (h ⁺ ) are present in large numbers in the valence band of the first semiconductor, i.e., in the shell 22, and the electrons (e ⁻ ) are present in large numbers in the conduction band of the second semiconductor, i.e., in the core 21. The holes (h ⁺ ) are used in an oxidation reaction of water to generate oxygen (O ₂ ), and the electrons (e ⁻ ) are used in a reduction reaction of water to generate hydrogen (H ₂ ).

In the particle 20, the generated holes (h ⁺ ) and electrons (e ⁻ ) are located in different semiconductors and are spatially separated, so that recombination of carriers is suppressed. Therefore, the carrier life is increased, and the energy conversion efficiency in the photocatalyst can be improved. In addition, holes (h ⁺ ) and electrons (e ⁻ ) are generated in the nanoparticle 20, and the distance between the generated holes (h ⁺ ) and electrons (e ⁻ ) and the surface of the nanoparticle 20, which is the active surface of the photocatalyst, is short, so that the holes (h ⁺ ) and electrons (e ⁻ ) can be efficiently used in the oxidation reaction or reduction reaction of water. In addition, the oxygen (O ₂ ) and hydrogen (H ₂ ) generated by these reactions can effectively kill target cells.

Third Embodiment
3 is a diagram showing the structure of a photocatalyst according to a third embodiment of the present invention. As shown in FIG. 3, the particle 30 is composed of a core 31, a partial shell 32 partially covering the core 31, and a particle surface, i.e., a modifier 33 and a specific recognition substance 34 bound to the shell. The core 31 is formed of a first semiconductor, and the partial shell 32 is formed of a second semiconductor. The particle 20 in the second embodiment differs only in that the partial shell 32 is formed so as to partially cover the core 31, and the shell 22 is not formed so as to cover the entire core 21. The relationship between the band structure of each semiconductor and the band structure of the nanoparticle 30 is the same as that of the second embodiment shown in FIG. 2B, so a description thereof will be omitted.

In the particle 30, a part of the core 31 is exposed on the surface of the nanoparticle 30, so that the distance between the positive holes (h ⁺ ) present in large numbers in the core 31 and the catalytically active surface becomes closer, and the generated positive holes (h ⁺ ) can be used more efficiently in the oxidation reaction of water. In other words, oxygen (O ₂ ) can be released more efficiently, and a higher cell killing effect can be achieved.

As with the present embodiment, the particle 10 in the first embodiment can also be configured so that the shell covers only a part of the core, rather than the entire core. With this configuration, the distance between the electrons (e ⁻ ) present in large amounts in the core and the catalytically active surface becomes closer, and the generated electrons (e ⁻ ) can be used more efficiently in the reduction reaction of water. In other words, hydrogen (H ₂ ) can be released more efficiently, and a higher cell killing effect can be achieved.

Fourth Embodiment
FIG. 4 is a diagram showing the structure of a photocatalyst according to a fourth embodiment of the present invention. As shown in FIG. 4, the particle 40 is composed of a core 41, a partial shell 42 partially covering the core 41, and a modifier 43 and a specific recognition substance 44 bound to the particle surface, i.e., the shell. The core 41 is formed of a first semiconductor, and the partial shell 42 is formed of a second semiconductor. The particle 30 in the third embodiment differs only in that the modifier 43 is formed so as to cover the entire shell, and further, the specific recognition substance 44 is bound to the modifier 43. The relationship between the band structure of each semiconductor and the band structure of the nanoparticle 40 is the same as that of the second embodiment shown in FIG. 2B, so the description will be omitted. The modifier 43 is a liposome having a lipid bilayer structure.

In the case of particle 40, since the modifying substance 43 is a liposome, the particle 40 can be taken up into the target cell by endocytosis or phagocytosis, or by fusion of the liposome membrane with the cell membrane.

As with the present embodiment, the particle 10 in the first embodiment and the particle 20 in the second embodiment are also formed so that the modifier 13 or modifier 23 covers the entire shell, and it is also possible to configure the specific recognition substance 44 to bind to the modifier 43. With this configuration, the particle 10 or particle 20 can be taken up into the target cell by endocytosis or phagocytosis, or fusion of the liposome membrane with the cell membrane.

[Photocatalyst manufacturing method]
In this embodiment, the photocatalyst can be produced, for example, by first producing intermediate particles made of a compound semiconductor that forms a core, and then coating the surface of the intermediate particles with a compound semiconductor that forms a shell, and then supporting a modifier and a specific recognition substance on the surface of the particles, or by further coating the particles with a modifier and then binding a specific recognition substance onto the modifier.

The compound semiconductor that forms the core is charged into the reaction solvent and mixed, and then the mixed solution is held in a temperature-controllable reaction vessel such as an autoclave vessel at a temperature of about 200° C. to about 400° C. for about 30 minutes to about 3 hours to grow the crystals of the core particles. Note that the particle size of the particles can be appropriately adjusted by changing the heating temperature and heating time.
The reaction solvent can be appropriately selected depending on the type of compound semiconductor used to form the core, and examples thereof include diphenyl ether.
The obtained core may be used as it is for the reaction with the compound semiconductor that forms the subsequent shell, but from the viewpoint of obtaining a photocatalyst with high purity, it is preferable to purify the core and remove unreacted raw materials, etc. Examples of the method for purifying the core include a method of washing the core with a mixed solvent of a solvent capable of dispersing the particles and a solvent for dissolving and removing unreacted raw materials, etc.

Then, a layer made of the compound semiconductor that forms the shell is formed on the surface of the core to cover it. For example, a sol-gel method can be used to form a layer made of the compound semiconductor that forms the shell, in which a metal oxide shell is formed by hydrolyzing a metal alkoxide on the core particles. Specifically, a metal alkoxide and a reaction promoter such as a surfactant or aqueous ammonia are added to a dispersion of core particles, and the mixture is stirred at about room temperature for several hours to grow crystals made of the compound semiconductor that forms the shell on the surface of the core particles, thereby obtaining a photocatalyst.

The extent to which the shell covers the core can be controlled by changing the heating temperature and heating time during shell formation, the amount of shell material added, etc. For example, by shortening the heating time, the growth of the compound semiconductor that forms the shell can be interrupted before it completely covers the core particle, and it is possible to obtain a particle 30 in which the shell 32 partially covers the core 31, as in the particle 30 in the third embodiment described above.

The modifier and specific recognition substance can be supported on the particle surface by physical or chemical bonding, either directly or via a linker. Examples of bonding modes include coordinate bonds, covalent bonds, hydrogen bonds, hydrophobic interactions, and physical adsorption, and known bonding methods can be used.

Pharmaceutical Compositions
The pharmaceutical composition of this embodiment is a pharmaceutical composition used for the prevention or treatment of cancer, and contains the above-mentioned cell killing agent.

The pharmaceutical composition of this embodiment can effectively prevent or treat cancer while suppressing side effects and the emergence of drug-resistant bacteria.

The pharmaceutical composition of this embodiment may further contain a pharma- ceutically acceptable carrier.

As the pharma- ceutically acceptable carrier, those usually used in the preparation of pharmaceutical compositions can be used without any particular restrictions. More specifically, examples include binders such as gelatin, corn starch, gum tragacanth, and gum arabic; excipients such as starch and crystalline cellulose; swelling agents such as alginic acid; solvents for injections such as water, ethanol, and glycerin; and adhesives such as rubber-based adhesives and silicone-based adhesives.

The pharmaceutical composition of this embodiment may further contain additives. Examples of additives include lubricants such as calcium stearate and magnesium stearate; sweeteners such as sucrose, lactose, saccharin, and maltitol; flavorings such as peppermint and saffron oil; stabilizers such as benzyl alcohol and phenol; buffers such as phosphates and sodium acetate; solubilizers such as benzyl benzoate and benzyl alcohol; antioxidants; preservatives, etc.

The pharmaceutical composition of this embodiment can be formulated by appropriately combining the above-mentioned cell killing agent with the above-mentioned pharma- ceutical acceptable carriers and additives, and mixing them in a unit dose form required for generally accepted pharmaceutical practice.

When the pharmaceutical composition of this embodiment is a dispersant containing water, it is preferable to store it in a light-blocking container or the like in order to suppress the activity of the photocatalyst. Alternatively, it is preferable to prepare it just before use.

The pharmaceutical composition of this embodiment may be in a dosage form for oral use or a dosage form for parenteral use, but is preferably in a dosage form for oral use. Examples of dosage forms for oral use include tablets, capsules, elixirs, microcapsules, etc. Examples of dosage forms for parenteral use include injections, ointments, patches, etc.

The pharmaceutical composition of the present embodiment may be used in combination with a therapeutic agent for another disease. For example, the cell killing agent may be used in combination with an anticancer agent, an antibiotic, or the like, to more effectively prevent or treat the target disease.
The cytocidal agent and the other drug may be in the same formulation or in separate formulations. Each formulation may be administered by the same administration route or by separate administration routes. Furthermore, each formulation may be administered simultaneously, sequentially, or separately at a certain time or period. In one embodiment, the cytocidal agent and the other drug may be in the form of a kit containing them.

The pharmaceutical composition of the present embodiment may be used in combination with a labeling substance. For example, the cell killing agent may be used in combination with a labeling substance to visualize the delivery of the photocatalyst to the affected area of the disease.
Examples of labeling substances include radioisotopes and fluorescent substances.
As the radioisotope, a positron-emitting nuclide can be used, specifically, for example, ⁵⁵ Co, ⁶⁴ Cu, ⁶⁶ Ga, ⁶⁸ Ga, ⁷⁶ Br, ⁸⁹ Zr, ¹²⁴ I, etc. A known method can be used to label the photocatalyst with these positron-emitting nuclides.

Fluorescent substances include those exemplified above as cell killing agents.

[Administration Method]
Subjects to which the antibody is administered include, but are not limited to, humans, monkeys, dogs, cows, horses, sheep, pigs, rabbits, mice, rats, guinea pigs, hamsters, and cells thereof. Among these, mammals or mammalian cells are preferred, and humans or human cells are particularly preferred.

Administration to patients or animals can be performed by methods known to those skilled in the art, such as intrathecal injection, intraarterial injection, intravenous injection, subcutaneous injection, local injection, intranasal injection, transbronchial injection, intramuscular injection, transdermal injection, or oral injection. The dosage varies depending on the patient's weight and age, the patient's symptoms, the method of administration, etc., but those skilled in the art can select an appropriate dosage.

[Light irradiation method]
The light source for irradiating the patient or animal with light after administration of the pharmaceutical composition of this embodiment may be any light source that irradiates light with an energy level equal to or greater than that required for the photocatalyst to decompose water, i.e., light with a wavelength shorter than about 1000 nm (>about 1.23 eV), and examples of such light include sunlight, LED, xenon lamp, mercury lamp, laser, etc.
That is, after administration of the pharmaceutical composition of this embodiment, the photocatalyst can be activated by exposing the body surface to sunlight. Alternatively, for the purpose of active treatment, light can be irradiated from the body surface using the above-mentioned light source (excluding sunlight), or light can be irradiated to the affected area using a catheter or the like equipped with the above-mentioned light source (excluding sunlight). When a catheter equipped with a laser is used, it can be said to be a phototherapy that combines a laser and a photocatalyst.

<Preventive and therapeutic methods>
In one embodiment, the present invention provides a method for preventing cancer, comprising administering to a subject an effective amount of the cell-killing agent.
Examples of cancers that are the target of the cancer prevention method of this embodiment include the same cancer types exemplified in the above "Cell Killing Agent". The subject may be a healthy individual, a cancer patient, or a person who may develop cancer. In addition, the subject is not limited to humans, and includes various mammals exemplified in the above "Pharmaceutical Composition".

In one embodiment, the present invention provides a method for treating cancer, comprising administering an effective amount of the cell killing agent to a patient or animal in need of treatment.

Alternatively, in one embodiment, the present invention provides a method for treating a cancer, comprising administering to a human or animal patient in need of treatment an effective amount of the cell killing agent;
Irradiating a tumor site of the subject with light;
The present invention provides a method for treating cancer, comprising:

As described above, the cytotoxic agent has high catalytic activity, and after administration of the cytotoxic agent, exposure to sunlight alone can be sufficient to exert a cytotoxic effect, but in order to perform treatment more effectively, light can also be actively irradiated. Examples of light sources and irradiation methods include those exemplified in the above "pharmaceutical composition".
Examples of cancers that can be treated by the cancer prevention method of this embodiment include the same types of cancers as those exemplified in the above "cell killing agent." Furthermore, examples of animals to be treated include various mammals other than humans exemplified in the above "pharmaceutical composition."

In one embodiment, the present invention also provides use of the cell-killing agent for the prevention or treatment of cancer.
In one embodiment, the present invention also provides use of the cell-killing agent for the manufacture of a pharmaceutical composition for use in the prevention or treatment of cancer.

Supplement Composition
The supplement composition of this embodiment is a supplement composition used for preventing cancer and contains the above-mentioned cell killing agent.

The supplement composition of this embodiment can effectively prevent cancer while suppressing side effects and the emergence of drug-resistant bacteria. As described above, the photocatalyst of this embodiment generates only minute amounts of hydrogen and oxygen in the body, so it has little effect on the human body, and remains in the blood for a certain period of time after administration and is then excreted from the body. Therefore, it is considered that there are few problems with taking it every day from a safety standpoint.

The supplement composition of this embodiment may further contain known additives that are commonly used in foods and beverages. Examples of additives include sweeteners such as sugar, fructose, isomerized liquid sugar, glucose, aspartame, and stevia, acidulants such as citric acid, malic acid, and tartaric acid, excipients such as dextrin and starch, binders, diluents, flavorings, buffers, thickeners, gelling agents, colorants, stabilizers, emulsifiers, dispersants, suspending agents, and preservatives.

The supplement composition of this embodiment may be in a solid form such as a powder or gel, in a semi-solid form such as a sol tablet, or in a liquid form such as a dispersion.

When the supplement composition of this embodiment is a dispersant containing water, it is preferable to store it in a light-blocking container or the like to suppress the activity of the photocatalyst.

The supplement composition of this embodiment can be incorporated as a food additive into special purpose foods, functional foods, nutritional supplements, health foods, foods for specified health uses, and foods with functional claims.

The amount of photocatalyst in the supplement composition of this embodiment may be any amount that can exert its cell killing effect, and taking into consideration the oral dosage in the above-mentioned pharmaceutical composition and the general intake of the target food and beverage, the daily intake per adult can usually be about 0.01 μg to 1 g, preferably about 0.05 μg to 100 mg, and more preferably about 0.1 μg to 10 mg. For example, in the case of a solid form, it can be 0.5% by mass to 50% by mass, and in the case of a liquid form, it can be 0.1 w/v% to 10 w/v%.

<Sterilizing Composition>
The sterilizing composition of the present embodiment contains the above-mentioned cell killing agent.

The sterilizing composition of this embodiment can effectively sterilize bacteria, particularly pathogenic bacteria, while suppressing the emergence of drug-resistant bacteria.

The sterilizing composition of this embodiment has a sufficient sterilizing effect even with the cell killing agent alone, but may further contain an additive having sterilizing and antibacterial effects. Examples of additives having antibacterial effects include sodium sulfite, sodium benzoate, sorbic acid, potassium sorbate, sodium dehydroacetate, butyl paraoxybenzoate, propionic acid, ethylparaben, propylparaben, butylparaben, polyphosphate, polylysine, milt protein extract, ethanol, glycine, glycerin fatty acid ester, sodium acetate, thiamine lauryl sulfate, licorice oil extract, chitosan, moso bamboo extract, lysozyme, rosemary extract, cationic surfactants (benzalkonium chloride, benzethonium chloride, cetylpyridinium chloride, etc.), etc.

The sterilizing composition of this embodiment can contain other components that are generally blended into sterilizing compositions, for example, powders such as inorganic pigments and extender pigments, anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, esters of fatty acids and polyhydric alcohols such as higher fatty acid alkanolamides and fatty acid monoglycerides, moisturizers, lower alcohols, thickeners, chelating agents, preservatives, colorants, fragrances, and other known additives, within the scope of not impairing the effect of the sterilizing composition of this embodiment.

The sterilization composition of this embodiment may be in a solid form such as a powder or gel, a semi-solid form such as a sol tablet, or a liquid form such as a dispersion using water or alcohol (ethanol, etc.) as a solvent.

When the sterilization composition of this embodiment is a dispersant containing water, it is preferable to store it in a light-blocking container or the like to suppress the activity of the photocatalyst.

The amount of photocatalyst in the sterilization composition of this embodiment may be any amount that can exert its cell killing effect, and can be appropriately adjusted taking into consideration the number of photocatalysts that are taken up into the target cells in the above-mentioned cell killing agent. For example, in the case of a solid, the amount can be 0.5% by mass or more and 50% by mass or less, and in the case of a liquid, the amount can be 0.1% by mass or more and 10% by mass or less.

[Sterilization method using sterilizing composition]
As a sterilization method using the sterilizing composition, sterilization can be performed by contacting the sterilizing composition of the present embodiment with an object to be sterilized and then irradiating the object with light.

There are no particular limitations on the objects to be sterilized, but since the sterilization method using the sterilizing composition of this embodiment does not involve heating, it is suitable for objects made of heat-sensitive materials or objects that are difficult to sterilize by heating.

Examples of methods for contacting the sterilizing composition with the target include spraying, misting, immersion (dipping, soaking, etc.), etc. Alternatively, the liquid sterilizing composition can be contacted with the target in the form of a wet wiper impregnated with a base fabric such as paper, nonwoven fabric, absorbent cotton, rayon stable cotton, or a combination of these with a plastic film, etc.
Among these, spraying or atomizing is preferred.

In addition, examples of the light source include the same ones as those exemplified for the pharmaceutical composition above.
The intensity of the light to be irradiated may be the same as those exemplified for the cell killing agent above.

Methods for physically destroying target cells in vitro
The method of the present embodiment is a method for physically destroying target cells in vitro, comprising:
contacting the cell killing agent with a target cell to allow the cell killing agent to be incorporated into the target cell;
irradiating the target cells into which the cell killing agent has been incorporated with light;
Includes.

According to the method of the present embodiment, the target cells into which the cytotoxic agent has been taken up are irradiated with light, and the photocatalyst contained in the cytotoxic agent decomposes the water contained within the target cells by the energy of the light, generating hydrogen and oxygen. The target cells are then expanded by the hydrogen and oxygen, and the target cells can be effectively physically destroyed in vitro.
When the target cells are bacteria, the method of this embodiment can also be called a bactericidal method.

Target cells include those exemplified in the above cell killing agents, but among them, pathogenic bacteria are preferred.

Methods for contacting the cell killing agent with the target cells include the same methods as those exemplified for the above-mentioned sterilizing composition.
In addition, examples of the light source include the same ones as those exemplified for the pharmaceutical composition above.
The intensity of the light to be irradiated may be the same as those exemplified for the cell killing agent above.

The present invention will be described below with reference to examples, but the present invention is not limited to the following examples.

[Example 1]
(Cancer cell destruction test)
1. Formation of the cell killing agent After adding diphenyl ether, GaI ₃ , InI ₃ and NaNH ₂ as a reaction solvent, they were mixed and the mixed solution was kept at a temperature of 300° C. for 1 hour. This allowed the growth of core particles of photocatalytic crystals made of In ₆₀ Ga ₄₀ N (first semiconductor) with an average particle size of 5 nm. The average particle size of the core particles was measured by TEM and dynamic light scattering.
Thereafter, the core particles were purified by repeating a centrifugation process using alternately toluene to disperse the core particles and ethanol to remove unnecessary raw materials from the particles, and then dispersed in cyclohexane.
Next, titanium tetraisopropoxide, octylphenol ethoxylate as a surfactant, and ammonia water were added to the obtained dispersion of core particles, and hydrolysis was performed to form TiO ₂ (second semiconductor) with an average particle size of 0.3 nm around the core particles made of In ₆₀ Ga ₄₀ N, thereby obtaining type II core-shell type InGaN (core)/TiO ₂ (shell) particles. The average particle size of TiO ₂ was measured by TEM and dynamic light scattering.
Next, a methanol solution of sodium 3-mercaptopropionate and tetramethylammonium hydroxide was added to the resulting chloroform dispersion of InGaN/TiO ₂ particles and reacted at 70° C. to modify the carboxyl groups.
Furthermore, in order to impart cell permeability and the ability to specifically recognize target cells, a membrane-permeable peptide, arginine peptide (R8), and thiol-terminated folic acid-modified polyethylene glycol, which selectively binds to cancer cells, were mixed with the carboxyl group-modified particles to obtain a photocatalyst for destroying cancer cells.

2. Cancer cell destruction test The dispersion of the photocatalyst (200 nmol/L) obtained in "1." above was sprayed onto HeLa cells, and the cells were taken up by endocytosis. The number of photocatalysts taken up per cell was measured by light absorption, and was about 20,000. The method for measuring the number of photocatalysts taken up per cell by light absorption was as follows: First, a dispersion of a photocatalyst with a known concentration was sprayed onto the culture medium of HeLa cells to allow the photocatalyst to be taken up, and the remaining dispersion of the photocatalyst was collected. Next, the difference between the concentration of the dispersion of the photocatalyst before spraying and the concentration of the dispersion of the photocatalyst collected was compared in terms of the amount of light absorption to calculate the amount of the photocatalyst taken up. Next, infrared light with a wavelength of 700 nm (energy density 0.1 mW/cm ² ) was irradiated for 10 minutes. This caused the water in the cells to be decomposed by the photocatalyst, generating hydrogen and oxygen. The cells expanded due to the bubbles of hydrogen and oxygen, and the cell membrane was physically destroyed, resulting in the death of the cancer cells. The death of the cancer cells was confirmed by visual observation using an optical microscope.

The cell killing agent of this embodiment can suppress side effects and the emergence of drug-resistant bacteria, and can kill cancer cells and various pathogenic bacteria more effectively and efficiently.

10, 20, 30, 40...particles (photocatalyst)
11, 21, 31, 41 ... core 12, 22, 32, 42 ... shell 13, 23, 33, 43 ... cell-permeable modifying substance (modifying substance)
14, 24, 34, 44...Substances that specifically recognize target cells (specific recognition substances)

Claims (9)

Particles that are photocatalysts;
A substance provided on the surface of the particle that specifically recognizes a target cell;
A modifying substance provided on the surface of the particle and having cell permeability to the target cell,
the particles are made of a compound semiconductor;
the compound semiconductor includes a first semiconductor and a second semiconductor;
the particle has a core-shell structure in which one of the first semiconductor and the second semiconductor is a core and the other is a shell,
The band structure of the grain is type II,
the highest energy level in the valence band of the first semiconductor is more positive than the oxidation potential of water;
A cell-killing agent, wherein the lowest energy level in the conduction band of said second semiconductor is more negative than the reduction potential of water. The cell killing agent according to claim 1, wherein a portion of the core is exposed from the shell at the surface of the particle. The cell killing agent according to claim 1 or 2, wherein the compound semiconductor is at least one selected from the group consisting of metal oxides, metal nitrides, metal oxynitrides, metal carbonitrides, II-VI semiconductors, and III-V semiconductors. The cell killing agent according to any one of claims 1 to 3, wherein the optical absorption edge of the first semiconductor is 700 nm or more and 1000 nm or less. The cell killing agent according to any one of claims 1 to 4, wherein the average particle size of the particles is greater than 1 nm and less than or equal to 1000 nm. The cell killing agent according to any one of claims 1 to 5, wherein the average particle diameter of the core of the particles is 1 nm or more and 20 nm or less. A sterilizing composition comprising the cell killing agent according to any one of claims 1 to 6. 1. A method for physically disrupting target cells in vitro, comprising:
Contacting a target cell with the cell killing agent according to any one of claims 1 to 6 to allow the cell killing agent to be incorporated into the target cell;
and irradiating the target cells into which the cell-killing agent has been incorporated with light. The method of claim 8 , wherein the target cell is a pathogenic bacterium.

Images