A nano-heterojunction radiosensitizer for hypoxic tumors and a preparation method thereof

Abstract

This invention discloses a nano-heterojunction radiosensitizer suitable for hypoxic tumors and its preparation method. The radiosensitizer is a core-shell structured nanoparticle, comprising a core and a shell. The core is a high-valence bismuth-based nanomaterial, including at least one of sodium bismuthate, silver bismuthate, and potassium bismuthate. The shell coats the surface of the core and comprises a metal oxide. A Z-shaped heterojunction is formed between the inner core and the outer shell. Under X-ray excitation, this heterojunction forms a built-in electric field, promoting electron-hole separation. Electrons in the high-valence bismuth nanoparticle phase reduce high-valence bismuth (Bi). 5+ →Bi 3+ ) and releases highly reactive lattice oxygen, which then reacts with holes on the TiO2 phase to generate singlet oxygen ( 1 O2), while the holes on TiO2 oxidize water molecules to produce hydroxyl radicals (•OH).

Description

Technical Field

[0001] This invention belongs to the field of biomedical engineering and nanomaterials technology, specifically relating to a nano-heterojunction radiosensitizer suitable for hypoxic tumors and its preparation method; this invention utilizes the lattice oxygen migration mechanism to achieve oxygen-independent reactive oxygen generation in a nano-heterojunction radiosensitizer, as well as the preparation method of the sensitizer and its application in radiotherapy for hypoxic tumors. Background Technology

[0002] Radiotherapy is one of the three main clinical treatments for malignant solid tumors. It utilizes high-energy ionizing radiation to directly damage DNA structure or indirectly kill cells by ionizing water molecules within cells to generate reactive oxygen species such as hydroxyl radicals. Oxygen plays a crucial role in fixing DNA damage. However, solid tumors often develop a severe hypoxic microenvironment due to rapid cell proliferation and abnormal angiogenesis, with oxygen partial pressures far lower than in normal tissues. Hypoxia directly limits the efficacy of radiotherapy. The hypoxic environment induces the overexpression of hypoxia-inducible factor-1α (HIF-1α), activating downstream angiogenesis and metabolic reprogramming pathways, leading to acquired radiation resistance in tumor cells and causing radiotherapy failure in advanced and large tumors.

[0003] To overcome hypoxia limitations, researchers have developed various semiconductor heterojunction nanomaterials as radiosensitizers, attempting to enhance the catalytic efficiency of reactive oxygen species by promoting electron-hole separation. However, traditional heterojunction materials still suffer from serious mechanistic defects. Under X-ray excitation, the holes generated by charge separation utilize water molecules to generate hydroxyl radicals, but electrons in the conduction band must rely on oxygen in the environment as acceptors to generate superoxide anions or singlet oxygen. Under hypoxic conditions in tumors, the recombination rate of electrons and holes increases sharply due to the lack of oxygen to capture electrons, leading to the failure of the sensitization effect. Although strategies exist for oxygen delivery using perfluorocarbons or for oxygen production by decomposing endogenous hydrogen peroxide using catalase, these methods are limited by low delivery efficiency, poor deep tumor penetration, and limited endogenous hydrogen peroxide concentration. Simply improving oxygen supply is insufficient to fundamentally solve the radiotherapy resistance problem of large tumors.

[0004] High-valence metal compounds typically possess extremely strong oxidizing and electron affinity. For example, pentavalent bismuth in sodium bismuthate has a redox potential as high as 1.59 V, far exceeding the 0.695 V of oxygen. Theoretically, if high-valence bismuth compounds can be used as "endogenous electron scavengers" to replace oxygen in preferentially consuming electrons, and if the abundant oxygen atoms in their crystal structure can be used as a "lattice oxygen reservoir," with radiation triggering the migration and release of lattice oxygen to participate in the reaction, it is hoped that a radiosensitizer that can generate reactive oxygen species without consuming ambient oxygen can be constructed, thereby completely overcoming the limitations of hypoxic microenvironments on radiotherapy. Summary of the Invention

[0005] In view of the above-mentioned deficiencies in the prior art, this invention discloses a nano-heterojunction radiosensitizer suitable for hypoxic tumors and its preparation method. The core technical problem to be solved by this invention is that traditional semiconductor heterojunction radiosensitizers are highly dependent on dissolved oxygen in the tumor microenvironment as an electron acceptor when generating reactive oxygen species, resulting in low catalytic efficiency and limited therapeutic effect within severely hypoxic solid tumors. This invention aims to develop a radiosensitizing material that does not depend on ambient oxygen, utilizing the material's own lattice oxygen migration mechanism to efficiently generate singlet oxygen and hydroxyl radicals even under extremely hypoxic conditions, thereby significantly improving the efficacy of radiotherapy. Another objective of this invention is to provide a simple and controllable method for preparing the aforementioned nano-heterojunction radiosensitizer, capable of synthesizing core-shell nanomaterials with uniform morphology and stable structure.

[0006] To achieve the above objectives, the technical solution provided by the present invention is as follows:

[0007] <First Aspect> A nanoheterojunction radiosensitizer suitable for hypoxic tumors, wherein the radiosensitizer is a core-shell structured nanoparticle comprising: The core material is a high-valence bismuth-based nanomaterial, including at least one of sodium bismuthate (NaBiO3), silver bismuthate, and potassium bismuthate; An outer shell layer that covers the surface of the core, the outer shell layer being made of a metal oxide; The material of the core and the material of the outer shell form a Z-shaped heterojunction.

[0008] The metal oxide is selected from one or more of titanium dioxide (TiO2), hafnium oxide (HfO2), and gadolinium oxide.

[0009] That is, the outer shell layer is made of a narrow bandgap inorganic material that can be excited by X-rays, such as titanium oxide, hafnium oxide, gadolinium oxide, etc.

[0010] A Z-shaped semiconductor heterojunction is formed between the core material and the outer shell material, allowing electrons to flow from the core material to the outer shell material. When the Z-shaped heterojunction is excited by X-rays, the two semiconductor materials that make up the heterojunction each generate electrons and holes. Electrons with weaker reducing power in the conduction band (CB) of one semiconductor recombine with holes with weaker oxidizing power in the valence band (VB) of the other semiconductor through the contact interface. This allows the Z-shaped heterojunction to retain electrons with extremely strong reducing power and holes with extremely strong oxidizing power.

[0011] The core has a particle size of 80-120 nm; the overall particle size of the core-shell structured nanoparticles is 100-150 nm. The thickness of the outer shell layer is 5-50 nm.

[0012] The core-shell structured nanoparticles have a porous spherical nanoflower-like morphology.

[0013] The surface of the core-shell structured nanoparticles also has a hydrophilic polymer modification layer.

[0014] The hydrophilic polymer modification layer is connected to the surface of the outer shell layer by a coupling agent; the coupling agent includes at least one of sodium 1,2-dioleoyl-sn-glycerol-3-phosphate, dopamine, and silane coupling agents. The hydrophilic polymer includes at least one of polyethylene glycol, distearate phosphatidylethanolamine-methoxy polyethylene glycol, polyvinylpyrrolidone, and chitosan.

[0015] Preferably, the high-valence bismuth-based nanomaterial is sodium bismuthate (NaBiO3), and the metal oxide of the outer shell is titanium dioxide (TiO2) or hafnium dioxide (HfO2).

[0016] <Second aspect> The present invention also provides a method for preparing the radiosensitizer as described above, comprising the following steps: S1. Materials that provide bismuth-based nanomaterials with high valence and lattice oxygen as the core; S2. The core material is dispersed in an alcohol / water mixed solution containing a surfactant, and after ultrasonic treatment and centrifugal washing, it is redispersed in an alcohol solvent; an alkaline solution is added under stirring, and then a metal oxide precursor solution is added dropwise to carry out a hydrolysis reaction, so that the metal oxide precursor is hydrolyzed and deposited on the surface of the core material to form an outer shell layer covering the core; thus, core-shell structured nanoparticles are obtained.

[0017] In step S2, a narrow bandgap inorganic material shell that can be excited by X-rays is grown in situ on the core surface of the core through a hydrolysis reaction, resulting in Z-type heterojunction core-shell structured nanoparticles.

[0018] In step S2, the surfactant includes at least one of sodium dodecyl sulfate (SDS), sodium fatty acid salt, and sodium fatty alcohol sulfate; Preferably, the concentration of the surfactant in the alcohol / water mixed solution is 25-35 mg / mL.

[0019] In step S2, the metal oxide precursor is tetrabutyl titanate, tetraisopropyl titanate, or titanium tetrachloride. The metal oxide precursor is dissolved in a first solvent (ethanol / water mixture) to prepare a metal oxide precursor solution. The alkaline solution is ammonia. The reaction time is 5-30 minutes to obtain core-shell structured nanoparticles with a TiO2 outer shell. Alternatively, the metal oxide precursor is tetrabutyl hafnium oxide or hafnium tetrachloride. The metal oxide precursor is dissolved in a second solvent (ethanol) to prepare a metal oxide precursor solution. The reaction time is 0.5-2 hours to obtain core-shell structured nanoparticles with a HfO2 outer shell.

[0020] In step S2, the amount of the metal oxide precursor added is 20-200 μL; the concentration of the ammonia water is 25-28%, and the amount added is 20-80 μL.

[0021] In S1, the method for preparing the bismuth-based nanomaterial with high valence and lattice oxygen includes the following steps: S11. Mix the bismuth-containing compound with the polymer stabilizer to form a mixture; add this mixture to a high-boiling-point organic solvent solution containing a particle size control reagent, mix and stir evenly, and carry out a hydrothermal reaction at high temperature; centrifuge, wash, and collect the precipitate to obtain bismuth oxide nanoparticle templates; S12. Disperse the bismuth oxide nanoparticle template obtained in step S11 in a solvent to form a bismuth oxide nanoparticle solution; add the bismuth oxide nanoparticle solution and a strong oxidant dropwise into a strong alkaline solution and stir vigorously to react; after the reaction is completed, centrifuge, wash, and collect the precipitate to obtain a bismuth-based nanomaterial core with high valence state and lattice oxygen.

[0022] In step S11, the bismuth-containing compound includes one or more of bismuth nitrate, bismuth sulfate, bismuth chloride, and bismuth acetate; the polymer stabilizer includes one or more of polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), polyvinyl alcohol (PVA), and polyacrylic acid (PAA). The molecular weight of the polyvinylpyrrolidone is 10,000-50,000.

[0023] In step S11, the ratio of bismuth-containing compound to polymer stabilizer is 0.1-0.375 mmol: 0.3-0.5 g.

[0024] Further, in step S11, the solvent used to dissolve the bismuth-containing compound includes a nitric acid solution or a sulfuric acid solution with a concentration of 1 M. The ratio of the bismuth-containing compound, polymer stabilizer, and solvent is 0.1-0.375 mmol : 0.3-0.5 g : 4-6 mL, preferably 0.1-0.375 mmol : 0.3-0.5 g : 5 mL.

[0025] Further, in step S11, the particle size control reagent is sodium hydroxide (NaOH) or urea. The high-boiling-point organic solvent includes one or more of polyethylene glycol, ethylene glycol, glycerol, and diethylene glycol. The ratio of particle size control reagent to high-boiling-point organic solvent is 0.1-1.35 mmol: 10-40 mL.

[0026] Further, in step S11, the volume ratio of the mixture to the high-boiling-point organic solvent solution containing the particle size control reagent is 4-6 mL: 10-40 mL.

[0027] Furthermore, in step S11, the hydrothermal reaction is carried out in a stainless steel autoclave lined with a polytetrafluoroethylene gasket. The reaction conditions are: 150-200°C for 2-4 hours.

[0028] Furthermore, in step S11, the centrifugation conditions are: 9000-10000 rpm, centrifugation for 5-10 min. Deionized water is used for washing.

[0029] Further, in step S12, the strong oxidant includes one of sodium hypochlorite solution, sodium persulfate solution, and chlorine gas. Preferably, the strong oxidant is sodium hypochlorite solution, and its effective chlorine content is 8-10 wt%.

[0030] Further, in step S12, the strongly alkaline solution is a sodium hydroxide solution with a concentration of 10-18 M.

[0031] Further, in step S12, the volume ratio of the bismuth oxide nanoparticle solution, the strong oxidant, and the strong alkaline solvent is 1:2-3:5-10. The bismuth oxide nanoparticle solution is prepared by dissolving bismuth oxide nanoparticles in deionized water to prepare a bismuth oxide nanoparticle solution with a concentration of 20-30 mg / mL.

[0032] Furthermore, in step S12, the time for the bismuth oxide nanoparticle solution and the strong oxidant to be added together to the strong alkaline solvent is controlled within 2-30 seconds (for example, 1 mL of bismuth oxide nanoparticle solution and 2-3 mL of strong oxidant are added together to the strong alkaline solvent within 2-30 seconds).

[0033] Furthermore, in step S12, the conditions for vigorous stirring are: stirring at 400-500 rpm for 10-20 minutes at room temperature. The conditions for centrifugation are: centrifugation at 8000-9000 rpm for 5-10 minutes. Deionized water is used for washing.

[0034] Furthermore, following step S2, step S3 further includes modifying the core-shell structured nanoparticles with a hydrophilic polymer: The core-shell structured nanoparticles obtained in step S2 are dispersed in a second solvent, a coupling agent is added, and the mixture is separated. Then, a hydrophilic polymer is added to react with the mixture, and the solvent is evaporated to obtain hydrophilic polymer-modified core-shell structured nanoparticles.

[0035] Further, in step S3, the coupling agent includes at least one of sodium 1,2-dioleoyl-sn-glycerol-3-phosphate, dopamine, and a silane coupling agent. The hydrophilic polymer includes at least one of distearylphosphatidylethanolamine-methoxy polyethylene glycol, chitosan, and polydopamine.

[0036] In one specific embodiment of the present invention, step S3 includes: First, the core-shell structured nanoparticles obtained in step S2 are dispersed in an organic solvent (such as chloroform) to prepare a dispersion with a mass concentration of 20-30 mg / mL. Then, a coupling agent solution is added, which is a solution with a mass concentration of 2-5 mg / mL prepared by dissolving a coupling agent (such as sodium 1,2-dioleoyl-sn-glycerol-3-phosphate, DOPA) in an organic solvent (such as chloroform); the mixture is ultrasonically mixed and centrifuged and washed to remove unbound coupling agent; Finally, a hydrophilic polymer (such as distearylphosphatidylethanolamine-methoxy polyethylene glycol 5000, DSPE-mPEG5000) is added, the mixture is stirred for 8-12 hours, the solvent is evaporated, and the core-shell structured nanoparticles modified with hydrophilic polymers are obtained.

[0037] Furthermore, the mass ratio of the core-shell structured nanoparticles, coupling agent, and hydrophilic polymer is (2-10):1:(4-5), preferably 2:1:4 to 10:1:4.

[0038] Thirdly, the use of the radiosensitizer in the preparation of radiotherapy drugs for treating hypoxic tumors. The radiosensitizer is used to enhance the sensitivity of X-ray, gamma-ray, or electron beam radiotherapy.

[0039] This invention discloses a nano-heterojunction radiosensitizer suitable for hypoxic tumors. The radiosensitizer is a hydrophilic polymer-modified semiconductor heterojunction core-shell nanomaterial based on pentavalent bismuth.

[0040] The core material of the nano-heterojunction radiosensitizer is a pentavalent bismuth-based compound such as sodium bismuthate.

[0041] The outer shell material of the nano-heterojunction radiosensitizer is a common biocompatible shell material, including titanium oxide and hafnium oxide.

[0042] The nano-heterojunction radiosensitizer prepared by this invention is not prone to aggregation.

[0043] The technical solution disclosed in this invention prepares a uniformly sized and dispersed nano-heterojunction radiosensitizer through a novel synthetic route. Then, by modifying the surface of the radiosensitizer with hydrophilic polymer chains, a radiosensitizer material with low toxicity, high enrichment at tumor sites, and high performance in computed tomography imaging is prepared. Most importantly, this nano-heterojunction radiosensitizer, benefiting from an X-ray triggered lattice migration mechanism, still exhibits excellent tumor-killing effects under tumor hypoxic conditions.

[0044] This invention utilizes high-valence bismuth nanoparticles with lattice oxygen as electron scavengers and lattice oxygen reservoirs, with a narrow-bandgap inorganic material shell serving as a dense outer shell for bandgap matching. Under X-ray excitation, this heterojunction forms a built-in electric field, promoting electron-hole separation; electrons in the high-valence bismuth nanoparticle phase reduce high-valence bismuth (Bi) 5+ →Bi 3+ ) and releases highly reactive lattice oxygen, which then reacts with holes on the TiO2 phase to generate singlet oxygen ( 1 Simultaneously, the holes on TiO2 oxidize water molecules to generate hydroxyl radicals (•OH). This process does not depend on dissolved oxygen in the tumor microenvironment, effectively overcoming the resistance of hypoxic tumors to radiotherapy and significantly improving the efficacy of radiotherapy.

[0045] The technical solution disclosed in this invention has the following beneficial technical effects: (1) The nano-heterojunction radiosensitizer disclosed in this technical solution, which is suitable for hypoxic tumors, can maintain a high efficiency of reactive oxygen generation in deep or large solid tumors with severe hypoxia without consuming oxygen inside the tumor.

[0046] (2) The nano-heterojunction radiosensitizer disclosed in this technical solution, which is suitable for hypoxic tumors, can simultaneously generate singlet oxygen and hydroxyl radicals with high cytotoxicity under X-ray excitation, triggering a severe oxidative stress reaction in tumor cells.

[0047] (3) The nano-heterojunction radiosensitizer disclosed in this technical solution, which is suitable for hypoxic tumors, can significantly downregulate the expression level of hypoxia-inducible factor-1α (HIF-1α) in tumor cells, thereby disrupting the protective mechanism of tumor cells to adapt to the hypoxic environment.

[0048] (4) The nano-heterojunction radiosensitizer disclosed in this technical solution, which is suitable for hypoxic tumors, has extremely high stability under physiological conditions and can be effectively enriched in the tumor site. At the same time, the material itself has good biocompatibility, and the high atomic number bismuth element in the core endows it with CT imaging function, realizing precise tumor localization and visual monitoring of treatment effect. Attached Figure Description

[0049] The following will further explain the concept, specific structure, and technical effects of the present invention in conjunction with the accompanying drawings, so as to fully understand the purpose, features, and effects of the present invention.

[0050] Figure 1 This is a schematic diagram of the preparation route of the nano-heterojunction radiosensitizer suitable for hypoxic tumors disclosed in this invention; Figure 2 This is a transmission electron microscope image of the NaBiO3 / TiO2 core-shell heterojunction prepared in Example 2 of this invention; Figure 3 These are transmission electron microscope images of the product prepared in Comparative Example 1 of this invention; Figure 4 This is a transmission electron microscope image of the product prepared in Comparative Example 2; Figure 5 This is a transmission electron microscope image of the Bi2O3 / TiO2 heterojunction nanoparticles prepared in Comparative Example 3. Figure 6 This is a transmission electron microscope image of the NaBiO3 / SiO2 core-shell nanoparticles prepared in Comparative Example 4. Figure 7 The infrared Fourier transform spectrum of the hydrophilic polymer-modified NaBiO3TiO2 core-shell heterojunction of Example 2 is shown. Figure 8 This is a diagram illustrating the ability and mechanism of the hydrophilic polymer-modified NaBiO3 / TiO2 core-shell heterojunction (STHJ) prepared in Example 2 to release reactive oxygen species under different doses of X-rays in hypoxic conditions. Figure 9 This is a diagram showing the biocompatibility of the hydrophilic polymer-modified NaBiO3 / TiO2 core-shell heterojunction (STHJ) prepared in Example 2 in in vitro experiments. Figure 10 This is a diagram showing the antitumor effect of X-ray excitation on the hydrophilic polymer-modified NaBiO3 / TiO2 core-shell heterojunction (STHJ) prepared in Example 2.

[0051] Figure 11 This is a diagram showing the radiotherapy effect of the hydrophilic polymer-modified NaBiO3 / TiO2 core-shell heterojunction (STHJ) prepared in Example 2 on tumor-bearing mice. Figure 12 This is a computed tomography (CT) imaging result of the hydrophilic polymer-modified NaBiO3 / TiO2 core-shell heterojunction (STHJ) prepared in Example 2 on tumor-bearing mice. Detailed Implementation

[0052] The present invention will be described in detail below with reference to embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several adjustments and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0053] like Figure 1 The diagram shown is a schematic diagram of the preparation route of the nano-heterojunction radiosensitizer suitable for hypoxic tumors provided by the present invention. The preparation route and steps of the radiosensitizer disclosed in the present invention are illustrated in the form of a flowchart.

[0054] Example 1 Synthesis of NaBiO3 nanoparticles Step 1: Preparation of bismuth oxide nanoparticle templates 1.1 Dissolve 0.375 mmol of bismuth nitrate pentahydrate in 5 mL of nitric acid solution (1 M) to obtain a bismuth nitrate solution; mix the bismuth nitrate solution with 0.3 g of polymer stabilizer (polyvinylpyrrolidone; Mw=40000) to form a mixture; 1.2. Add the mixture from step 1.1 to 0.3 g sodium hydroxide and 25 mL polyethylene glycol solution. Then transfer the mixture to a 50 mL stainless steel autoclave lined with polytetrafluoroethylene (PTFE). Seal the autoclave and maintain it at 150°C for 3 hours. Centrifuge the resulting product at 9000 rpm for 5 minutes and wash it three times with deionized water to obtain bismuth oxide nanoparticle templates with a particle size of approximately 100 nm. In this step, the structure-directing properties of polyvinylpyrrolidone (PVP) can effectively prepare uniformly dispersed bismuth oxide nanoparticles as templates. Furthermore, the pH adjustment using sodium hydroxide can effectively control the particle size of the bismuth oxide nanoparticles.

[0055] Step 2: Synthesis of NaBiO3 nanoparticles 20 mg of the bismuth oxide nanoparticles used as templates in step 1 were weighed and dissolved in 1 mL of deionized water to form a bismuth oxide nanoparticle solution. The bismuth oxide nanoparticle solution and 3 mL of a strong oxidizing agent (sodium hypochlorite solution, available chlorine content 10 wt%) were rapidly added dropwise over 5 seconds to a polytetrafluoroethylene tube containing 5 mL of 10 M sodium hydroxide solution. The mixture was vigorously stirred at 400 rpm for 10 minutes at room temperature, then centrifuged with deionized water at 8000 rpm for 5 minutes and washed three times to obtain the NaBiO3 nanoparticle core. In this step, the strong oxidizing property of sodium hypochlorite and the weak oxidizing property of sodium bismuthate under strong alkaline conditions were utilized to rapidly oxidize the bismuth oxide nanoparticle template obtained in step 1 into NaBiO3 nanoparticles in a strong alkaline solution containing sodium hypochlorite.

[0056] Example 2 Synthesis of polyethylene glycol-modified NaBiO3 / TiO2 nanoparticles (STHJ) Step 1: Preparation of NaBiO3 / TiO2 core-shell heterojunction 20 mg of the NaBiO3 nanoparticles prepared in Example 1 as template were weighed and dissolved in 10 mL of an ethanol / water mixture (volume ratio 1:2) containing sodium dodecyl sulfate (SDS, 33 mg / mL), and sonicated for 20 minutes. The mixture was centrifuged at 8000 rpm for 5 minutes, washed once with ethanol, and redispersed in 10 mL of ethanol. 80 μL of concentrated ammonia was added with rapid stirring, followed by dropwise addition of 120 μL of an ethanol solution of tetrabutyl titanate (TBOT) (60 μL TBOT + 60 μL ethanol), and the reaction was allowed to proceed for 10 minutes. The mixture was centrifuged at 8000 rpm for 5 minutes, and washed three times with ethanol and water to obtain the NaBiO3 / TiO2 core-shell heterojunction.

[0057] The transmission electron microscope (TEM) image of the NaBiO3 / TiO2 core-shell heterojunction prepared in this step is shown below. Figure 2 As shown, it exhibits a core-shell structure and has high monodispersity, with a particle size of 100-150 nm.

[0058] Step 2: Preparation of PEG-modified NaBiO3 / TiO2 core-shell heterojunctions (STHJ) Weigh 20 mg of the NaBiO3 / TiO2 core-shell heterojunction prepared in step 1 and dissolve it in 1 mL of chloroform solution to prepare a NaBiO3 / TiO2 core-shell heterojunction dispersion. Add another 1 mL of chloroform solution of sodium 1,2-dioleoyl-sn-glycerol-3-phosphate at a concentration of 2 mg / mL and mix it under ultrasonic power at 120 W for 20 minutes to prepare a suspension. Centrifuge the suspension at 8000 rpm for 5 minutes, wash it three times and redisperse it in 1 mL of chloroform. Then add 4 mL of distearylphosphatidylethanolamine-methoxy polyethylene glycol at a concentration of 2 mg / mL and stir magnetically at 300 rpm for 8 hours. Finally, evaporate the chloroform to obtain the hydrophilic polymer-modified NaBiO3 / TiO2 core-shell heterojunction.

[0059] The hydrophilic polymer-modified NaBiO3 / TiO2 core-shell heterojunction prepared in this embodiment has the following infrared Fourier transform spectrum: Figure 3 As shown, compared to the unmodified NaBiO3 / TiO2 core-shell heterojunction, the hydrophilic polymer-modified NaBiO3 / TiO2 core-shell heterojunction exhibits higher performance at 2884 cm⁻¹. -1 It has a characteristic CH2 signal peak at 1278 cm⁻¹. -1 The presence of the -PO- characteristic signal peak indicates that the NaBiO3 / TiO2 core-shell heterostructure has achieved modification with hydrophilic polymers. Figure 7 The infrared Fourier transform spectrum of the hydrophilic polymer-modified NaBiO3TiO2 core-shell heterojunction of Example 2 is shown.

[0060] Example 3 Synthesis of PEG-modified NaBiO3 / HfO2 heterojunction Step 1: Preparation of NaBiO3 / HfO2 core-shell heterojunction Weigh 20 mg of the NaBiO3 nanoparticles used as templates prepared in Example 1 and dissolve them in 10 mL of ethanol. Stir the mixture thoroughly and immediately add 1.5 mL of C. 16 H 36 O4Hf (70% soluble in n-butanol). The stirring process was carried out at room temperature for 1 hour to obtain NaBiO3 / HfO2 core-shell heterojunctions. Subsequently, three centrifugations were performed, and the mixture was washed with ethanol and water after each centrifugation to obtain NaBiO3 / HfO2 core-shell heterojunctions.

[0061] Step 2: PEG modification of NaBiO3 / HfO2 core-shell heterojunction Weigh 20 mg of the NaBiO3 nanoparticle core prepared in step 1 and dissolve it in 1 mL of chloroform solution to prepare a NaBiO3 / HfO2 core-shell heterojunction dispersion. Prepare a suspension by ultrasonically mixing 1 mL of 2 mg / mL sodium 1,2-dioleoyl-sn-glycerol-3-phosphate at 120 W for 20 minutes. Centrifuge the suspension at 8000 rpm for 5 minutes, wash it three times, and redisperse it in 1 mL of chloroform. Then add 4 mL of 2 mg / mL distearate phosphatidylethanolamine-methoxy polyethylene glycol and magnetically stir at 300 rpm for 8 hours. Finally, evaporate the chloroform to obtain the hydrophilic polymer-modified NaBiO3 / HfO2 core-shell heterojunction.

[0062] Comparative Example 1 Weigh 20 mg of the NaBiO3 nanoparticles prepared in Example 1 as template and dissolve them in 10 mL of an ethanol / water mixture (volume ratio 1:2). Sonicate for 20 minutes. Centrifuge at 8000 rpm for 5 minutes, wash once with ethanol, and redisperse in 10 mL of ethanol. Add 80 μL of concentrated ammonia solution with rapid stirring, followed by dropwise addition of 120 μL of an ethanol solution of tetrabutyl titanate (TBOT) (60 μL TBOT + 60 μL ethanol). React for 10 minutes. Centrifuge at 8000 rpm for 5 minutes, wash three times with ethanol and water to obtain a light yellow powder, as shown in the figure. Figure 3 The NaBiO3 / TiO2 heterojunction nanoparticles with a core-shell structure could not be obtained.

[0063] Comparative Example 2 Weigh 20 mg of the NaBiO3 nanoparticles prepared in Example 1 as template and dissolve them in 10 mL of an ethanol / water mixture (volume ratio 1:2) containing polyvinylpyrrolidone (PVP, 20 mg / mL). Sonicate for 20 minutes. Centrifuge at 8000 rpm for 5 minutes, wash once with ethanol, and redisperse in 10 mL of ethanol. Add 80 μL of concentrated ammonia solution with rapid stirring, followed by dropwise addition of 120 μL of an ethanol solution of tetrabutyl titanate (TBOT) (60 μL TBOT + 60 μL ethanol). React for 10 minutes. Centrifuge at 8000 rpm for 5 minutes, wash three times with ethanol and water to obtain a light yellow powder, as shown in the figure. Figure 4 The diagram shows that core-shell structured NaBiO3 / TiO2 heterojunction nanoparticles cannot be obtained.

[0064] Comparative Example 3 Weigh 20 mg of the bismuth oxide nanoparticles prepared in Example 1 and dissolve them in 10 mL of an ethanol / water mixture (volume ratio 1:2) containing sodium dodecyl sulfate (SDS, 33 mg / mL). Sonicate for 20 minutes. Centrifuge at 8000 rpm for 5 minutes, wash once with ethanol, and redisperse in 10 mL of ethanol. Add 80 μL of concentrated ammonia solution with rapid stirring, followed by dropwise addition of 120 μL of an ethanol solution of tetrabutyl titanate (TBOT) (60 μL TBOT + 60 μL ethanol). React for 10 minutes. Centrifuge at 8000 rpm for 5 minutes, wash three times with ethanol and water to obtain a white powder, as shown below. Figure 5 The diagram shows core-shell structured Bi₂O₃ / TiO₂ heterojunction nanoparticles. Bi₂O₃ lacks the high-valence bismuth and lattice oxygen characteristics of NaBiO₃, therefore its active oxygen generation process again relies on external oxygen, failing to achieve the ROS generation mechanism under hypoxic conditions described in this invention. Figure 8 ).

[0065] Comparative Example 4 10 mg of the NaBiO3 nanoparticles prepared in Example 1 were weighed and dispersed in 8 mL of ethanol solution, and sonicated for 20 minutes. Then, under rapid stirring at 400 rpm, 2 mL of water and 120 μL of ammonia were added, followed by a slow dropwise addition of an ethanol solution of tetraethyl orthosilicate (TEOS) (4 μL of TEOS dissolved in 1 mL of ethanol). After the addition was complete, the reaction was continued at room temperature for 12 hours. After the reaction was completed, the mixture was centrifuged at 8000 rpm for 5 minutes and washed three times with ethanol and water to obtain NaBiO3 / SiO2 core-shell nanoparticles. Figure 6The diagram shows NaBiO3 / SiO2 core-shell nanoparticles with a core-shell structure. SiO2 itself is a wide-bandgap, low-activity insulating material, and unlike TiO2, it cannot effectively generate electron-hole pairs under X-ray excitation, nor can it form a heterojunction interface with NaBiO3 that facilitates charge separation and hole retention. Therefore, the ability of the obtained NaBiO3 / SiO2 core-shell nanoparticles to generate reactive oxygen species under X-ray irradiation is significantly lower than that of the NaBiO3 / TiO2 core-shell heterojunction. Figure 8 ).

[0066] Example 1: Test on the release of hydroxyl radicals and singlet oxygen. The hydrophilic polymer-modified NaBiO3 / TiO2 core-shell heterojunction prepared in Example 2 exhibits the following ability to generate hydroxyl radicals and singlet oxygen under hypoxic conditions by receiving different doses of X-rays: Figure 8 As shown, aminophenyl fluorescein (APF) and singlet oxygen sensor green fluorescence (SOSG) were used as specific probes for hydroxyl radicals and singlet oxygen. To assess the generation of hydroxyl radicals and singlet oxygen under hypoxia, the PBS solution was heated and bubbled with N2 (100°C, 30 min) to ensure that no dissolved O2 was present in the water. A hydrophilic polymer-modified NaBiO3 / TiO2 core-shell heterojunction (STHJ) was added to PBS buffer at pH 5.5, and the mixture was then transferred to 96-well plates. Next, APF or SOSG (final concentration to 10 μM) was added to the wells, and different doses of X-rays were applied. Fluorescence signals were then acquired using a multifunctional microscope. A continuous increase in fluorescence intensity was observed with increasing X-ray dose, indicating that the NaBiO3 / TiO2 core-shell heterojunction can continuously release hydroxyl radicals and singlet oxygen under hypoxic conditions.

[0067] Example 2: Biocompatibility and Antitumor Efficacy Test The hydrophilic polymer-modified NaBiO3 / TiO2 core-shell heterojunction (STHJ) prepared in Example 2 of this invention exhibits the following biocompatibility effect in in vitro experiments: Figure 9 As shown. Mouse colon cancer cells—CT26 cells—were cultured in 96-well plates (37°C, 5% CO2) at a density of 10,000 cells per well for 24 h, and then different concentrations of DMED medium (0, 25, 50, 100, 200, 400, and 600 μg / mL) were added. -1The NaBiO3 / TiO2 core-shell heterostructure was used to infect CT26 cells. After 24 h, the cells were washed three times with neutral PBS, and cell viability was detected using the Cell Counting Kit-8 (Yeasen) assay. The PBS group served as a control, and each group was repeated five times. The results showed that the NaBiO3 / TiO2 core-shell heterostructure exhibited good biocompatibility with CT26 cells even at the highest concentration of 600 μg / mL.

[0068] The hydrophilic polymer-modified NaBiO3 / TiO2 core-shell heterojunction (STHJ) prepared in Example 2 of this invention exhibits the following antitumor effect under X-ray excitation in in vitro experiments: Figure 10 As shown. CT26 cells were seeded at a density of 200-1,600 cells per well in 6-well plates, and deferoxamine solution (100 μM) was added to simulate tumor hypoxia. The plates were cultured for 12 h. Cell culture medium (100 μg / mL) was then added. -1 The hydrophilic polymer-modified NaBiO3 / TiO2 core-shell heterojunction (STHJ) was incubated for 4 h, and then subjected to 1 Gy min. -1 Cells were exposed to different X-ray doses (0, 2, 4, 6, and 8 Gy), followed by washing with PBS and incubation with fresh culture medium every 3 days for 14 days. Colonies were fixed with 4% paraformaldehyde and stained with 0.1% crystal violet dye. Only colonies containing at least 50 cells were counted, and the colony formation rate was calculated. The results show that the hydrophilic polymer-modified NaBiO3 / TiO2 core-shell heterostructure (STHJ) exhibits excellent radiosensitizing properties. The hydrophilic polymer-modified NaBiO3 / TiO2 core-shell heterojunction (STHJ) prepared in Example 2 of this invention showed the following radiotherapy effect on tumor-bearing mice: Figure 11 As shown. The tumor reached 100 mm. 3 CT26 tumor-bearing mice were randomly divided into four treatment groups, with five mice in each group as follows: PBS, STHJ, RT, and STHJ+X-ray. STHJ (6 mg mL⁻¹, 200 μL) was administered intravenously. Twenty-four hours later, mice requiring radiotherapy received 4 Gy (1 Gy min⁻¹). -1 X-ray therapy at a dose of 6 mg / mL. Intravenous injection of STHJ (6 mg / mL). -1 200 μL), and 24 hours later, the mice requiring radiotherapy were irradiated with X-rays at a dose of 4 Gy (1 Gy min). -1 On days 3 and 4, repeat the drug injection and radiotherapy as planned. Record the tumor size and body weight every two days, and measure the tumor volume using calipers. The volume is calculated as (length × width). 2 ) / 2 equation calculation.

[0069] The hydrophilic polymer-modified NaBiO3 / TiO2 core-shell heterojunction (STHJ) prepared in Example 2 of this invention showed the following imaging effect on computed tomography (CT) scans of tumor-bearing mice: Figure 12 As shown, when the polymer-modified NaBiO3 / TiO2 core-shell heterojunction was injected intravenously into tumor-bearing mice 24 hours later, a significant increase in contrast was observed at the tumor site in computed tomography imaging. This indicates that the hydrophilic polymer-modified NaBiO3 / TiO2 core-shell heterojunction (STHJ) can effectively accumulate at the tumor site and enable computed tomography imaging diagnosis of the tumor.

[0070] This invention discloses a nano-heterojunction radiosensitizer suitable for hypoxic tumors and its preparation method. The nanoparticle material is a monodisperse NaBiO3 / TiO2 core-shell heterojunction modified with a hydrophilic polymer, which can be released under X-rays, and the release of hydroxyl radicals and singlet oxygen does not require the participation of external oxygen. The NaBiO3 / TiO2 core-shell heterojunction obtained by the technical solution of this invention can effectively inhibit tumor formation in a mouse colon cancer tumor model. The NaBiO3 / TiO2 core-shell heterojunction can also be used for radiotherapy synergistic treatment in computed tomography imaging and breast cancer mouse models. It also possesses good biocompatibility, low long-term toxicity, and rapid metabolism, exhibiting extremely high clinical diagnostic and therapeutic benefits.

[0071] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A nanoheterojunction radiosensitizer suitable for hypoxic tumors, characterized in that, The radiosensitizer is a core-shell structured nanoparticle, comprising: The core material is a high-valence bismuth-based nanomaterial, including at least one of sodium bismuthate, silver bismuthate, and potassium bismuthate; An outer shell layer that covers the surface of the core, the outer shell layer being made of a metal oxide; The material of the core and the material of the outer shell form a Z-shaped heterojunction.

2. The nano-heterojunction radiosensitizer according to claim 1, characterized in that, The metal oxide is selected from one or more of titanium dioxide, hafnium oxide, and gadolinium oxide; And / or, the surface of the core-shell structured nanoparticles also has a hydrophilic polymer modification layer.

3. The nano-heterojunction radiosensitizer according to claim 2, characterized in that, The hydrophilic polymer modification layer is connected to the surface of the outer shell layer by a coupling agent; the coupling agent includes at least one of sodium salt of 1,2-dioleoyl-sn-glycerol-3-phosphate, dopamine, and silane coupling agent; the hydrophilic polymer includes at least one of polyethylene glycol, distearate phosphatidylethanolamine-methoxy polyethylene glycol, polyvinylpyrrolidone, and chitosan.

4. A method for preparing the nano-heterojunction radiosensitizer according to any one of claims 1-3, characterized in that, Includes the following steps: S1. Materials that provide bismuth-based nanomaterials with high valence and lattice oxygen as the core; S2. The core material is dispersed in an alcohol / water mixed solution containing a surfactant, and after ultrasonic treatment and centrifugal washing, it is redispersed in an alcohol solvent. An alkaline solution is added under stirring, followed by the dropwise addition of a metal oxide precursor solution to carry out a hydrolysis reaction. This hydrolyzes the metal oxide precursor and deposits it on the surface of the core material, forming an outer shell layer that covers the core. Core-shell structured nanoparticles were obtained.

5. The method according to claim 4, characterized in that, In step S2, the surfactant includes at least one of sodium dodecyl sulfate, sodium fatty acid salt, and sodium fatty alcohol sulfate, and its concentration in the alcohol / water mixed solution is 25-35 mg / mL; The metal oxide precursor is tetrabutyl titanate, tetraisopropyl titanate, or titanium tetrachloride; the metal oxide precursor is dissolved in a first solvent to prepare a metal oxide precursor solution, the alkaline solution being ammonia water, and the hydrolysis reaction time is 5-30 minutes to obtain core-shell structured nanoparticles with a TiO2 outer shell; or, the metal oxide precursor is tetrabutyl hafnium oxide or hafnium tetrachloride, the metal oxide precursor is dissolved in a second solvent to prepare a metal oxide precursor solution, and the hydrolysis reaction time is 0.5-2 hours to obtain core-shell structured nanoparticles with a HfO2 outer shell.

6. The method according to claim 4, characterized in that, In step S1, the preparation method of the bismuth-based nanomaterial with high valence state and lattice oxygen includes: S11, mixing a bismuth-containing compound with a polymer stabilizer to form a mixture; adding this mixture to a high-boiling-point organic solvent solution containing a particle size control reagent, mixing and stirring evenly, and carrying out a hydrothermal reaction at high temperature; centrifuging, washing, and collecting the precipitate to obtain bismuth oxide nanoparticle templates; S12. Disperse the bismuth oxide nanoparticle template obtained in step S11 in a solvent to form a bismuth oxide nanoparticle solution; add the bismuth oxide nanoparticle solution and a strong oxidant dropwise into a strong alkaline solution and stir vigorously to react; after the reaction is completed, centrifuge, wash, and collect the precipitate to obtain a bismuth-based nanomaterial core with high valence state and lattice oxygen.

7. The method according to claim 6, characterized in that, In step S11, the bismuth-containing compound includes one or more of bismuth nitrate, bismuth sulfate, bismuth chloride, and bismuth acetate, and the ratio of the bismuth-containing compound to the polymer stabilizer is 0.1-0.375 mmol: 0.3-0.5 g; the polymer stabilizer includes one or more of polyvinylpyrrolidone, polyethylene glycol, polyvinyl alcohol, and polyacrylic acid, and the molecular weight of the polyvinylpyrrolidone is 10,000-50,000; the particle size control agent is sodium hydroxide or urea, and the high-boiling-point organic solvent includes one or more of polyethylene glycol, ethylene glycol, glycerol, and diethylene glycol, and the ratio of the particle size control agent to the high-boiling-point organic solvent is 0.1-1.35 mmol: 10-40 mL.

8. The method according to claim 6, characterized in that, In step S12, the strong oxidant includes one of sodium hypochlorite solution and sodium persulfate solution, wherein the effective chlorine content of the sodium hypochlorite solution is 8-10 wt%; the strong alkaline solution is a 10-18 M sodium hydroxide solution; the volume ratio of the bismuth oxide nanoparticle solution, the strong oxidant, and the strong alkaline solution is 1:2-3:5-10; and the time for the bismuth oxide nanoparticle solution and the strong oxidant to be added dropwise to the strong alkaline solution is 2-30 seconds.

9. The method according to claim 4, characterized in that, Following step S2, step S3 further includes modifying the core-shell structured nanoparticles with a hydrophilic polymer: dispersing the core-shell structured nanoparticles obtained in step S2 in an organic solvent to prepare a dispersion with a mass concentration of 20-30 mg / mL; adding a coupling agent solution, ultrasonically mixing, centrifuging and washing to remove unbound coupling agent; then adding a hydrophilic polymer, stirring and reacting for 8-12 hours, evaporating the solvent to obtain hydrophilic polymer-modified core-shell structured nanoparticles.

10. The use of the nanoheterojunction radiosensitizer according to any one of claims 1-3 or the nanoheterojunction radiosensitizer prepared by the method according to any one of claims 4-9 in the preparation of a radiotherapy drug for treating hypoxic tumors.

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