Novel metal oxide nanoparticles and compositions thereof for use as radiation enhancers or for visualizing biological tissues

Abstract

The present invention relates to nanoparticles (NPs) of the present invention, their compositions, and their use as therapeutic and / or imaging agents, particularly in the field of oncology. The NPs are composed of first nanoparticles of at least one high-Z metal oxide material, to which smaller second nanoparticles are covalently attached at the surface of the first nanoparticles. The second nanoparticles are composed of a) at least one noble metal or at least one metal oxide, metal sulfide, metal selenide, or metal sulfide / selenide that is a Fenton or Fenton-like reaction catalyst. The NPs of the present invention produce surprising therapeutic effects when exposed to ionizing radiation, such as X-rays, gamma rays, protons, neutrons, radioisotopes, and / or electron beams. Thus, the NPs can be used as radiation-enhancing agents in the field of oncology. The nanoparticles can also be used as contrast agents.

Description

[Technical Field]

[0001] The present invention relates to nanoparticles (NPs) of the present invention, their compositions, and their use as therapeutic agents, particularly in the fields of oncology and / or imaging agents. The NPs of the present invention produce surprising therapeutic effects when the therapeutic agent is exposed to ionizing radiation, such as X-rays, gamma rays, protons, neutrons, radioisotopes, and / or electron beams. Thus, the NPs may be used as radiation enhancers. They may also be used as contrast agents for visualizing biological tissues, preferably soft tissues, for example, for diagnostic purposes, typically to detect tumor cells in oncology settings, and for delineating tumor bed margins after tumor resection. The present invention also relates to an innovative method for synthesizing the NPs. [Background technology]

[0002] Radiation enhancers are beneficial in the medical field, especially in oncology. When exposed to ionizing radiation, they locally amplify the accumulated radiation dose (on-off activity). Present at the cancerous tumor cell level, when exposed to ionizing radiation, they increase tumor cell damage and destruction compared to radiation alone, without additional toxicity to surrounding healthy tissue. The basic principle of radiation enhancement by high-Z nanoparticle materials is the material's ability to release a large number of electrons in a nanoscale volume, thereby amplifying radiation-induced biological damage. Thus, a primary beam (e.g., photons from X-rays or fast ions) interacts with atoms of the high-Z radiation enhancer material to generate secondary particles (photons and electrons such as Auger electrons, photoelectrons, photons, k-fluorescence, Compton recoil electrons, Compton scattered photons, and delta electrons). In a dense medium, these secondary particles and photons continuously ionize surrounding biomolecules and nanoparticles, resulting in an enhanced radiation effect. The effectiveness of radiation enhancers can be measured as the "dose enhancement effect" (DEF) (Maggiorella et al. (2012) Nanoscale radiotherapy with hafnium oxide nanoparticles, Future Oncol. 8(9), 1167-1181).

[0003] Various high-Z metal-containing compositions have been identified as having radiation-enhancing capabilities, but to date, only one compound (densely crystalline hafnium oxide nanoparticles referred to by the applicant as "NBTXR3") has advanced into Phase 3 clinical trials (oncology-clinicaltrials.gov identifier NCT04892173 - for the treatment of solid tumor cancers in oncology).

[0004] Many approaches have been taken to identify radiation enhancer systems that exhibit efficacy and minimal toxic effects. For example, metal-organic frameworks (MOFs), metal-organic plates (MOPs), or metal-organic layers (MOLs) with high Z elements have been proposed as porous radiation enhancers (WO 2016061256, WO 2019028250). MOFs are generally constructed by assembling metal-oxo clusters of high Z elements using organic linkers. These porous systems carry small molecule drugs or other compounds for in vivo therapeutic applications.

[0005] However, the latter system has been reported to show in vivo (hydrolytic) cleavage between the organic linker and the metal-oxo cluster, indicating a high risk of structural degradation in vivo [Kathryn E. deKrafft et al. Zr- and Hf-based nanoscale metal-organic frameworks as contrast agents for computed tomography. J Mater Chem. 2012 Jan 1;22(35)].

[0006] Gold nanoclusters (AuNCs) have become promising materials for bioimaging detection due to their tunable photoluminescence, large Stokes shift, low photobleaching, and good biocompatibility. U.S. Patent No. 6,955,639 (Hainfeld et al.) describes a method for enhancing X-ray radiation effects using metal, specifically gold, nanoparticles. The size (diameter) of the metal core is preferably 0.8–3 nm for biodistribution reasons. While there is extensive literature on the potential of gold nanoparticle radiation enhancers, to our knowledge, this product has not been used clinically to date.

[0007] Achieving sufficient concentrations of gold atoms within tumors while limiting toxicity is a challenge. Chen et al. [Chen, Y. Set al. Assessment of the in vivo toxicity of gold nanoparticles, Nanoscale Res. Lett. 4(8)(2009)858-64] demonstrated that gold nanoparticles ranging in size from 8 to 37 nm induce severe disease when injected intraperitoneally into BALB / C mice at a dose of 8 mg / Kg / week (median survival = 21 days).

[0008] Patent application WO 2013087920(A1) describes gold nanoparticles coated with hafnium oxide. The purpose was to protect the surrounding biological environment from gold atom-induced toxicity. No biological data was published for these compositions.

[0009] Active research is being conducted in the development of novel materials useful for bioimaging and / or radiation therapy. There is an unmet need to provide stable, non-toxic, and effective products that can act as radiation enhancers for use as therapeutic agents in combination with ionizing radiation. Advantageously, for example, in the field of oncology, the product should also function as a bioimaging agent, allowing oncologists to visualize and treat cancerous tumors (in combination with ionizing radiation) using the same product, i.e., a "theranostic" product. These compounds should also demonstrate sustained efficacy and stability in vivo when exposed to (fractionated) radiation therapy (RT) sessions, as typically delivered to humans, regardless of the type of ionizing radiation used (e.g., photons, protons, electrons, etc.) and / or radiation technique used (e.g., 3D-CRT, IMRT, etc.).

[0010] In particular, there is a need to provide materials that can be used as radiation enhancers with improved effectiveness compared to the prior art.

[0011] Furthermore, there is a need to provide materials that can be used as bioimaging agents.

[0012] The present inventors have identified a series of novel and inventive nanoparticles composed of high-Z metal oxide nanoparticles decorated (supported on their surfaces) with smaller covalently bound high-Z noble metal nanoparticles and / or nanoparticles of at least one Fenton or Fenton-like reaction catalytic material selected from metal oxides, metal hydroxides, metal oxyhydroxides, metal peroxides, metal sulfides, metal selenides, or metal sulfides / selenides. The nanoparticles are stable, non-toxic, and exhibit surprisingly high efficacy as radiation enhancers. The nanoparticles can also be used as contrast agents for visualizing biological tissues, particularly soft tissues. Summary of the Invention [Means for solving the problem]

[0013] The subject of the present invention is to provide stable radiation enhancement agents with enhanced efficacy suitable for clinical use. Advantageously, nanoparticles ("NPs") can also be used as contrast agents, particularly for visualizing soft tissues. The nanoparticles are composed of at least one high-Z metal oxide material, to the surface of which are covalently attached smaller noble metal nanoparticles and / or nanoparticles composed of materials that are Fenton or Fenton-like reaction catalysts. The Fenton or Fenton-like reaction catalysts may preferably be selected from metal oxides, metal hydroxides, metal oxyhydroxides, metal peroxides, metal sulfides, metal selenides, or metal sulfide / selenides.

[0014] Described herein are nanoparticles (NPs) or aggregates of nanoparticles (NPs), wherein the NPs are composed of at least one high-Z metal oxide (M x O y ) (i.e., metal oxides with an atomic number Z of at least 40) or mixed high-Z metal oxides (M x M' z O y) (i.e., a mixed metal oxide having an atomic number Z of at least 40), the first nanoparticles having a density of 7 g / cm 3 or more (≧) and 15g / cm 3 and a second, smaller nanoparticle is covalently attached to its surface via a linker, the second nanoparticle having a density of less than (<) a. at least one noble metal selected from gold (Au), platinum (Pt), ruthenium (Ru), rhodium (Rh), palladium (Rd), osmium (Os), and iridium (Ir), and / or b. at least one metal oxide, metal hydroxide, metal oxyhydroxide, metal peroxide, metal sulfide, metal selenide, or metal sulfide / selenide that is a Fenton or Fenton-like reaction catalyst, wherein the metal is selected from the group consisting of Fe, Co, Ni, Cu, and Mn; and optionally a negatively charged or a neutrally charged biocompatible surface coating, wherein the ratio of first nanoparticle metal content to second nanoparticle metal content is less than 30 weight / weight (w / w).

[0015] In certain embodiments, high-Z metal oxides (M x O y ) is HfO2 or ZrO2.

[0016] In certain embodiments, the second nanoparticles are composed of gold (Au).

[0017] In another particular embodiment, the second nanoparticles are composed of iron oxide (Fe3O4).

[0018] In a particular embodiment, the ratio of first nanoparticle metal content / second nanoparticle metal content is 20-30 weight / weight (w / w).

[0019] In certain embodiments, the linker on the first nanoparticle is an aminosilane and the linker on the second nanoparticle is citrate.

[0020] In a specific embodiment, the first nanoparticles have a size of about 40 to 100 nm.

[0021] In certain embodiments, each of the second nanoparticles has a size between 2 and 15 nm.

[0022] Also described herein are nanoparticles (NPs) or aggregates of nanoparticles (NPs) for use in altering or destroying target cells in a mammal when the cells are exposed to ionizing radiation selected from X-rays and protons. In certain embodiments, the cells are exposed to ionizing radiation in the context of a radiotherapy regimen selected from conventional fractionation regimens, hyperfractionation regimens, (accelerated) hypofractionation regimens, and stereotactic body radiotherapy (SBAR) regimens. In another particular embodiment, the target cells are derived from a solid malignant tumor selected from skin cancer, central nervous system cancer, head and neck cancer, lung cancer, breast cancer, gastrointestinal cancer, male genitourinary cancer, gynecological cancer, adrenal and / or retroperitoneal cancer, sarcoma, and pediatric cancer.

[0023] Also described herein are nanoparticles (NPs) or aggregates of nanoparticles (NPs) for use in visualizing biological tissues, particularly soft tissues, in mammals, thereby enabling the detection of tumor cells and / or the diagnosis of cancer.

[0024] Further described herein are compositions comprising a) the nanoparticles (NPs) or aggregates (NPs) of the present invention, or mixtures thereof, and b) a pharmaceutically acceptable carrier, vehicle, or support.

[0025] Certain compositions of the present invention are for use in mammals, particularly humans, to alter or destroy target cells, particularly tumor cells, when the cells are exposed to ionizing radiation.

[0026] Another particular composition of the present invention is for use in visualizing biological tissues, particularly soft tissues, in mammals using CT scans, thereby enabling the detection of tumor cells and / or the diagnosis of cancer.

[0027] In one embodiment of the present invention, the composition comprising the NPs or aggregates thereof is for use in altering or destroying target cells, particularly tumor cells, in mammals, particularly humans, when the cells are exposed to ionizing radiation. [Brief explanation of the drawings]

[0028] [Figure 1A] Transmission electron microscopy (TEM) images of Example 2 (scale bar = 50 nm), JEOL2100Plus was used for image analysis. [Figure 1B] Transmission electron microscopy (TEM) image of Example 3B confirming the presence of gold nanoparticles on the HfO2 nanoparticles (scale bar = 20 nm). Image analysis was performed using a JEOL 2100Plus. [Figure 1C] Transmission electron microscopy (TEM) image of Example 3B, confirming the presence of gold nanoparticles on the HfO2 nanoparticles (scale bar = 100 nm). Image analysis was performed using a JEOL 2100Plus. [Figure 2] For example, viability values ​​after 4 Gy irradiation from the average of at least three independent experiments for Examples 1, 3B (800 μM), and 2 (32 μM) activated by X-rays in CT26 cells. Values ​​are expressed as SF mean ± SD (n≧3) at 4 Gy. * indicates p-value<0.05. [Figure 3A] Transmission electron microscopy (TEM) images of Example 5 (scale bar = 50 nm), JEOL 2100Plus was used for image analysis. [Figure 3B] Transmission electron microscopy (TEM) images of Example 6 confirming the presence of gold nanoparticles on the surface of HfO2 nanoparticles. Figure 3B: Scale bar = 20 nm; Figure 3C: Scale bar = 100 nm. Image analysis was performed using a JEOL 2100Plus. [Figure 3C] Transmission electron microscopy (TEM) images of Example 6 confirming the presence of gold nanoparticles on the surface of HfO2 nanoparticles. Figure 3B: Scale bar = 20 nm; Figure 3C: Scale bar = 100 nm. Image analysis was performed using a JEOL 2100Plus. DETAILED DESCRIPTION OF THE INVENTION

[0029] definition High Z (metal) elements are elements of Mendeleev's periodic table having an atomic number value (i.e., Z value) of at least 40, preferably greater than 45, 50, 55, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, or 81. In the context of the present invention, high Z metal oxides are oxides of high Z metals (M x O y ) or mixed metal oxides of high Z metals M x M' z O y wherein M and M' are metal elements, and M or M' has a Z value of at least 40. Typically, M or M' can be a lanthanide element, a zirconium (Zr) element, or a hafnium (Hf) element.

[0030] Noble metals are defined herein as metals selected from gold (Au), platinum (Pt), ruthenium (Ru), rhodium (Rh), palladium (Rd), osmium (Os), and iridium (Ir), in particular gold (Au), platinum (Pt), ruthenium (Ru), rhodium (Rh), palladium (Rd), osmium (Os), and iridium (Ir).

[0031] As used herein, the term "crystallite" refers to a crystalline product. The size of the crystallites as well as their structure and composition can be analyzed from an X-ray diffractogram.

[0032] The term "nanoparticle aggregate" refers to a collection of nanoparticles that are strongly, typically covalently, bound to each other. Similarly, the term "microcrystal aggregate" refers to a collection of microcrystals that are strongly, typically covalently, bound to each other. In the context of the present invention, the nanoparticles (NPs) of the present invention may be in the form of nanoparticles or nanoparticle aggregates. The NPs of the present invention themselves are each composed of a first nanoparticle decorated with a (smaller) second nanoparticle. To form the NPs of the present invention, the first and second nanoparticles are preferably not in the form of aggregates themselves. The first and second nanoparticles preferably have sufficient colloidal stability to ensure that aggregation does not occur. Those skilled in the art will understand that the colloidal stability of nanoparticle suspensions can be greatly affected by the nanoparticle surface charge potential, or zeta potential. For information on the relationship between surface charge and colloidal stability, reference may be made to Norm ASTM E 2865-2012. Aggregation of the first and / or second nanoparticles may prevent the second nanoparticles from binding to the surface of the first nanoparticle to form reactive NPs.

[0033] The term "treatment" or "therapy" refers to both therapeutic and prophylactic or preventative treatments or measures that can significantly slow disease progression (e.g., halt cancerous tumor growth), or increase / improve progression-free survival (PFS) or overall survival (OS), or cure cancer (i.e., convert the patient into a cancer survivor, as further defined herein below).

[0034] Such treatment or therapy is intended for a subject in need thereof, particularly a mammal, preferably a human, typically a human patient suffering from a malignant solid tumor.

[0035] In the context of the art and the present invention, the terms "treatment with curative intent", "curative treatment" or "curative therapy" refer to a treatment or therapy, in particular a treatment that includes a radiotherapy step, that provides the treated subject with a curative solution for treating the cancer from which the subject is suffering, i.e., for treating the subject as a whole (primary tumor and corresponding metastatic lesions).

[0036] As is well known to those skilled in the art, the term "palliative care," which specifically includes "palliative radiation therapy," is used for symptomatic relief and is distinct from "radiation therapy," i.e., radiation therapy delivered as a curative treatment (also identified herein as "curative radiation therapy"). Indeed, palliative care is considered by those skilled in the art to be an effective treatment for treating many of the symptoms caused by locally advanced or metastatic tumors, even in patients with a short life expectancy.

[0037] The "Fenton reaction" is a reaction reported by Fenton in 1894. 2+ was found to catalyze the oxidation of tartaric acid in H2O2-containing solutions. The general reaction mechanism of the Fenton reaction (shown in equations (1) and (2) below) was proposed by Haber and Weiss in 1934. (1) Iron 2+ +H2O2→Fe 3+ +OH · +OH - (2) Iron 3+ +H2O2→Fe 2+ +HOO · +H +

[0038] "Fenton-like reactions" are also known to occur when transition metal ions other than iron, e.g., Cu 2+ , Mn 2+ , and Co 2+ The latter metal ion acts as a catalyst to produce OH.

[0039] To avoid confusion, the abbreviation "NP" or "NPs" for the word nanoparticle is used herein only to refer to nanoparticles (or aggregates thereof) of the present invention that are comprised of at least one first nanoparticle of a high-Z metal oxide material, with smaller second nanoparticles covalently bonded to the surface of the first nanoparticle, the second nanoparticles being comprised of at least one noble metal and / or at least one Fenton or Fenton-like reaction catalyst material. "NP" is not used as an abbreviation for the first or second nanoparticles taken separately.

[0040] Detailed Description of the Invention The present inventors describe various aspects of the present invention. The nanoparticles (NPs) of the present invention are composed of a first nanoparticle, on the surface of which a second nanoparticle is bound. Thus, the NPs are composed of the first nanoparticles modified with the second nanoparticles.

[0041] First high-density high-Z metal oxide nanoparticles The first nanoparticles are composed of a high-Z metal oxide material. The metal oxides of interest described herein may be selected from the group consisting of oxides from the lanthanide elements and oxides from chemical (metal) elements of the periodic classification of the elements (Mendeleev's table), particularly oxides from metal elements with a Z of 40 or greater. The first nanoparticles have a density of 7 g / cm. 3 More than (≧)15g / cm 3 The first nanoparticles have a density of less than (<). Density is mass m per unit volume V. Patent application WO 2009 / 147214 shows that improved therapeutic efficacy can be obtained using nanoparticles having this density range. Thus, the first nanoparticles have a density of at least 7.5 g / cm 3 , preferably at least 8 g / cm 3 , even more preferably at least 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, or 14 g / cm 3The density of the nanoparticles or nanoparticle aggregates can be determined from about 1 g of dry powder using an Accupyc 1340 pycnometer instrument. Such nanoparticles are described in patent application WO 2009 / 147214.

[0042] Examples of suitable (high Z) metal oxides as described herein are as follows: suitable oxides from the lanthanide elements, which may be selected, for example, from the group consisting of Nd2O3, Sm2O3, Eu2O3, Gd2O3, Tb2O3, Dy2O3, Ho2O3, Er2O3, Tm2O3, Vb2O3, Lu2O3, and any mixtures thereof; -For example, HfO2, TaO2, Ta2O5, WO2, WO3, ReO2, OsO2, IrO2, PtO, PtO2, HgO, Hg2O, Tl2O3, B i2 a suitable oxide from a metallic element of the sixth period of the periodic table of the elements, which may be selected from the group consisting of O3, and any mixture thereof; - Suitable oxides from metallic elements of the fifth period of the periodic table of the elements, which may for example be selected from the group consisting of NbO, RuO2, Rh2O3, RhO2, PdO, Ag2O, AgO, CdO, In2O3, and any mixtures thereof.

[0043] Preferred nanoparticles are made from HfO2, ZrO2, PdO, or ReO2, or mixtures thereof. Particularly preferred nanoparticle materials are HfO2 and ZrO2. See WO 2009 / 147214 for further description of the synthesis of HfO2 nanoparticles and adjusting synthesis parameters to obtain a desired nanoparticle or nanoparticle aggregate density. The first nanoparticles are generally crystalline.

[0044] The synthesis of HfO2 primary nanoparticles according to one embodiment of the present invention is described in Example 3A below. It is noteworthy that the chemical properties of zirconium and hafnium cations in aqueous solution are similar [CF Baes and RS Mesmer: The Hydrolysis of Cations. John Wiley & Sons, New York, London, Sydney, Toronto 1976]. Therefore, zirconium cations can easily replace hafnium cations in the synthesis described below.

[0045] size: In the spirit of the present invention, the term "nanoparticles" refers to products, especially synthetic products, typically having a size of about 1 nm to about 1000 nm, preferably about 1 nm to about 500 nm.

[0046] The size of a particle can typically be measured by electron microscopy (EM) techniques such as transmission electron microscopy (TEM) or cryo-TEM, as is well known to those skilled in the art. The size of at least 100 particles is typically measured (typically considering the longest dimension of the particle), and the median size of the population of particles is reported as the size of the particle.

[0047] The (first) high-Z metal oxide nanoparticles have a size in the range of 20 to 150 nm, preferably 30 to 120 nm, more preferably 40 to 100 nm. As mentioned above, the nanoparticles may be in the form of microcrystals or aggregates of microcrystals.

[0048] The NPs of the present invention, which are composed of a first high-Z metal oxide nanoparticle having a second nanoparticle bound to its surface, can have a size ranging from 20 to 500 nm, preferably 40 to 200 nm, more preferably 40 to 120 nm, and even more preferably 40 to 100 nm. Similarly, the NPs may be in the form of microcrystals or aggregates of microcrystals.

[0049] The second nanoparticles typically have a size in the range of 2 to 15 nm, preferably 3 to 10 nm, and more preferably 3 to 6 nm.

[0050] Since the shape of particles can affect their biocompatibility, particles with a very uniform shape are preferred.Therefore, for pharmacokinetic reasons, particles that are essentially spherical, round, or oval in shape are preferred.Such shapes are also advantageous for the interaction of particles with cells or their uptake by cells.

[0051] Second metal nanoparticles As mentioned above, the NPs of the present invention comprise at least one high-Z metal oxide material (M x O y ) or mixed high-Z metal oxides (M x M' z O y ) first nanoparticles, to the surface of which are covalently attached smaller noble metal nanoparticles and / or materials capable of catalyzing Fenton or Fenton-like reactions, typically metal oxide, metal hydroxide, metal oxyhydroxide, metal peroxide, metal sulfide, metal selenide, or metal sulfide / selenide nanoparticles. The first nanoparticles, composed of high-Z metal oxide materials or mixed high-Z metal oxides, are typically in the range of 7-15 g / cm. 3 , preferably 7 g / cm 3 More than (≧)~15g / cm 3 having a density less than (<).

[0052] According to one embodiment of the present invention, the (second) nanoparticles covalently bound to the surface of the first nanoparticles consist of at least one noble metal.

[0053] According to one embodiment of the present invention, the (second) nanoparticles covalently bonded to the surface of the first nanoparticles consist of at least one Fenton or Fenton-like reaction catalytic material, which may be selected from at least one metal oxide, metal hydroxide, metal oxyhydroxide, metal peroxide, metal sulfide, metal selenide, or metal sulfide / selenide.

[0054] According to one embodiment of the present invention, the (second) nanoparticles covalently bonded to the surface of the first nanoparticles are a mixture of nanoparticles of at least one noble metal and nanoparticles of at least one Fenton and / or Fenton-like reaction catalytic material, which may be at least one metal oxide, metal hydroxide, metal oxyhydroxide, metal peroxide, metal sulfide, metal selenide, or metal sulfide / selenide capable of catalyzing a Fenton or Fenton-like reaction.

[0055] Nanoparticles of at least one precious metal material: Generally, the nanoparticle noble metal material can be gold (Au), platinum (Pt), ruthenium (Ru), rhodium (Rh), palladium (Rd), osmium (Os), or iridium (Ir), or any mixture thereof. A mixture of noble metals is known as an alloy. For example, the noble metal material can be an alloy of gold and platinum, or gold and palladium, or palladium and platinum. According to one embodiment of the present invention, the preferred noble metal material is gold, platinum, or palladium. A particularly preferred noble metal material is gold.

[0056] Any method known to those skilled in the art may be used to synthesize precious metal nanoparticles. The synthesis of gold nanoparticles according to one embodiment of the present invention is described in Example 2 below.

[0057] The size of the noble metal nanoparticles is in the range of 2 to 15 nm, preferably 3 to 10 nm, and more preferably 3 to 6 nm.

[0058] Therefore, for pharmacokinetic reasons, particles that are essentially spherical, round, or ovoid in shape are preferred.

[0059] High-Z metal oxide electronic cooperation with noble metal nanoparticle surface plasmons: Noble metal nanostructures exhibit unique and strongly enhanced optical properties due to the phenomenon of localized surface plasmon resonance (LSPR). In assemblies or complex noble metal nanostructures, individual plasmon oscillations on nearby particles can couple through their near-field interactions, resulting in coupled plasmon resonance modes that are very similar to exciton coupling in molecular aggregates or orbital hybridization in molecules [Jain and EL-Sayed (2010) "Plasmonic coupling in noble metal nanostructures," Chem. Phys. Lett., vol. 487, pp. 152-164]. Thus, plasmons in noble metal nanoparticles can be considered as mass-spring harmonic oscillators driven by energetic resonant light waves, with the electron cloud oscillating like a simple dipole in a direction parallel to the electric field of the electromagnetic radiation [Amendola et al., 2017) Surface plasmon resonance in gold nanoparticles: a review. J. Phys.: Condens. Matter 29 203002 (pp. 48)].

[0060] Without wishing to be bound by theory, we hypothesize that after irradiation with ionizing radiation, (i) the yield of low-energy electrons (LEEs), such as Auger electrons, emitted by high-Z metal oxide nanoparticles and / or (ii) the orbital distance of the LEEs are enhanced by the surface plasmons of the noble metal nanoparticles. Indeed, both Auger and plasmon electrons are confined on the nanoparticle surface, with Auger electrons exhibiting a very short range of less than 10 nm (Kuncic and Lacombe (2018) Nanoparticle radio-enhancement: principles, progress, and application to cancer treatment. Phys. Med. Biol. 63, 02TR01 (27pp)). The interaction between the noble metal surface plasmons and LEEs, such as Auger electrons, emitted by the metal oxide nanoparticles after irradiation is facilitated by the short distance (typically less than about 40 Å) between the surfaces of the first and second nanoparticles, particularly when the first and second nanoparticles are covalently linked via a relatively short linker (described below).

[0061] According to one embodiment of the present invention, at least one second nanoparticle of a noble metal is covalently bonded to the surface of each first nanoparticle. According to one embodiment of the present invention, at least 80% or 85%, more preferably at least 90% or 95%, of the surface of the noble metal nanoparticle is exposed to the surface, thereby maximizing the noble metal nanoparticle surface plasmon yield. In other words, according to one embodiment of the present invention, less than 20% or 15%, more preferably less than 10% or 5%, of the surface of the noble metal nanoparticle is embedded in the first nanoparticle (and therefore less accessible to the LEEs emitted from the high-Z metal oxide nanoparticles when irradiated with ionizing radiation).

[0062] The surface area of ​​the nanoparticles (NPs) of the present invention can be determined by BET (Brunauer, Emmett, and Teller) surface area analysis or by cetyltrimethylammonium bromide (CTAB) surface area analysis. CTAB surface area analysis is preferred. CTAB surface area analysis is based on the absorption of cetyltrimethylammonium bromide (CTAB) molecules on the surface of the nanoparticles (the nanoparticles are in solution). CTAB molecules are relatively large and therefore do not adsorb to micropores. Therefore, the CTAB surface area reflects only the surface of the nanoparticle available for interaction with ionizing radiation. Other molecules (such as proteins) can alternatively be used in the context of the present invention to estimate the nanoparticle surface area.

[0063] Second nanoparticles composed of a Fenton reaction catalyst material or a Fenton-like reaction catalyst material. According to one embodiment of the present invention, the second nanoparticles may be composed of metal oxides, metal hydroxides, metal oxyhydroxides, metal peroxides, metal sulfides, metal selenides, or metal sulfides / selenides, which act as Fenton or Fenton-like reaction catalysts. Fenton / Fenton-like reactions induced by the tumor microenvironment (TME) are generally considered the most representative of hemodynamic therapy (CDT). These generally use transition metal ions (e.g., Fe, Co, Ni, Cu, and Mn) to catalyze the decomposition of hydrogen peroxide (H2O2) with low activity, generating highly toxic hydroxyl radicals (·OH). Hydroxyl radicals can cause damage to cellular DNA, resulting in cell injury and / or death.

[0064] According to one embodiment of the present invention, the second nanoparticles are composed of a metal oxide, hydroxide, oxyhydroxide, or peroxide of Fe, Co, Ni, Cu, or Mn. According to one embodiment of the present invention, the second nanoparticles are composed of a mixed metal oxide of at least one of Fe, Co, Ni, Cu, or Mn.

[0065] According to one embodiment of the present invention, the second nanoparticle Fenton / Fenton-like reaction catalyst is comprised of at least one iron oxide, such as magnetite (Fe3O4), maghemite (γ-Fe2O3), or hematite (α-Fe2O3), an iron oxyhydroxide (FeOOH) such as goethite, copper oxide (CuO), copper peroxide (CuO2), manganese oxide (MnO), cobalt oxide (CoO), nickel oxide (NiO), or any mixture thereof.

[0066] According to a preferred embodiment, the second nanoparticles are composed of magnetite, also written as iron (II, III) oxide Fe3O4. 2+ ions and Fe 3+ It may contain both ions and be formulated as FeO·Fe2O3.

[0067] Suitable methods for synthesizing these metal salt nanoparticles are known to those skilled in the art. The synthesis of iron(II,III) oxide Fe3O4 nanoparticles according to one embodiment of the present invention is described in Example 5A herein below.

[0068] According to one embodiment of the present invention, the second nanoparticles are composed of a metal sulfide that acts as a Fenton or Fenton-like reaction catalyst. According to one embodiment of the present invention, the second nanoparticles are composed of FeS, FeS2, Fe3S4, CuS, Cu2S, MnS, NiS2, Ni3S2, CoS, CoS2, Co3S4, Co9S8, or any mixture thereof. Preferably, the second nanoparticles are composed of CuS, Cu2S, MnS, FeS, FeS2, or any mixture thereof. More preferably, the second nanoparticles are composed of FeS, FeS2, Fe3S4, or any mixture thereof.

[0069] According to one embodiment of the present invention, the second nanoparticles are composed of a metal selenide. According to one embodiment of the present invention, the second nanoparticles are composed of CuSe, Cu2Se, FeSe, FeSe2, Fe3Se4, MnSe, NiSe, NiSe2, Ni2Se3, CoSe, CoSe2, Co2Se4, or any mixture thereof. Preferably, the second nanoparticles are composed of CuSe, Cu2Se, MnSe, FeSe, FeSe2, Fe3Se4, or any mixture thereof. More preferably, the second nanoparticles are composed of FeSe, FeSe2, Fe3Se4, or any mixture thereof.

[0070] According to one embodiment of the present invention, the second nanoparticles of the Fenton / Fenton-like reaction catalyst material are composed of a mixture of metal sulfides and metal selenides (also identified herein as "metal sulfide / selenide" or "sulfide / selenide" catalysts). In the latter class of compounds, Se atoms may substitute for some of the sulfur atoms in the metal-sulfur structure. According to one embodiment of the present invention, the second nanoparticles are composed of FeSSe, Cu, x S / Cu x It consists of Se (where X is equal to 1 or 2), or mixed sulfide / selenide compounds of cobalt and / or nickel.

[0071] The size of the second nanoparticles made of a material that acts as a Fenton reaction catalyst or a Fenton-like reaction catalyst is generally in the range of 2 to 15 nm, preferably 3 to 10 nm, and more preferably 3 to 6 nm.

[0072] The second nanoparticles may be spherical, round, oval, or cubic in shape. The second nanoparticles may be nanocubes.

[0073] Therefore, for pharmacokinetic reasons, particles that are essentially spherical, round, or ovoid in shape are preferred.

[0074] Electronic Cooperation between High-Z Metal Oxide Nanoparticles and Fenton or Fenton-Like Reaction Catalyst Nanoparticles: Without being bound by theory, it is believed that the effectiveness of the NPs of the present invention may be due to cooperation between electron systems. Specifically, electrons generated by the interaction of the first nanoparticle, high-Z metal oxide nanoparticle, with ionizing radiation are coupled to the Fe 3+ Fe 2+ This creates a favorable electronic environment (including emitted photoelectrons and LEE electrons such as Auger electrons) for the reduction of Fe to Fe. 2+ can react with H2O2 to generate OH radicals, which cause DNA damage in cancerous tumor cells. 2+ / Fe 3+ When a mixture of ions is present on the surface of high-Z metal oxide (e.g., HfO2) nanoparticles, a larger amount of Fe is generated due to the electron-rich environment provided by the irradiated high-Z nanoparticles. 2+ Ions can be produced, which can lead to higher production of OH radicals and a local increase in the OH radical concentration (dose increase).

[0075] According to one embodiment of the present invention, Fe3O4 nanoparticles are covalently bonded to HfO2 nanoparticles. 2+ and Fe 3+ containing both (Fe 2+ Fe 3+ 2O4). Such an electronic environment is 2+ Furthermore, as has been shown in the prior art, the use of Fe3O4 (which gives an overall oxidation state of +2.5) has proven highly efficient in the decomposition of H2O2 into OH radicals [Xue, X. et al. (2009). Journal of hazardous materials, 166(1):407-414)].

[0076] Linker Typically, the second nanoparticle is covalently bonded to the surface of the first nanoparticle via a linker group. The linker group may be formed by the reaction of functional groups on the surfaces of the first and second nanoparticles. Thus, the first nanoparticle may be functionalized with a chemical group capable of reacting with the chemical group functionalized on the second nanoparticle. In the context of the present invention, the term "functionalized with" means strongly bonded, typically by a covalent bond, to the functional group. For example, the first nanoparticle may be functionalized with an amine group according to methods known to those skilled in the art. In that case, the second nanoparticle may be functionalized with a functional group reactive with the amine group, such as citrate, cysteine, or dopamine, resulting in the formation of a linker. The linker thus formed typically preferably has a bond length of up to 30 between both particles, thereby ensuring that electronic coordination between the two nanoparticles can be promoted. An amide linker may be mentioned as an example. Other linkers, such as disulfide-containing linkers or triazole linkers, may also be used.

[0077] Table 1 below provides a non-exhaustive list of examples of reactive groups and suitable agents that can be used to graft (chemically bond) the reactive groups onto the first nanoparticles of the present invention.

[0078] [Table 1]

[0079] Table 2 below provides a non-exhaustive list of examples of reactive groups and suitable agents that can be used to attach the reactive groups onto the second nanoparticles. The linker group is designated according to the type of second nanoparticle used.

[0080] [Table 2]

[0081] Table 3 below shows non-exhaustive examples of strategies that can be used to form covalent bonds between functionalized secondary particles and primary nanoparticles.

[0082] [Table 3]

[0083] Ratio of metal content of first / second nanoparticles The ratio of first nanoparticle metal content to second nanoparticle metal content is generally less than 35 weight / weight (w / w), preferably less than 30 (w / w), more preferably less than 25 (w / w). A ratio of first nanoparticle metal content to second nanoparticle metal content of 20 to 30 w / w is preferred.

[0084] In fact, the inventors identified a ratio of 20-30 based on the excellent efficacy results obtained herein and discussed below. The NPs have also been shown to be non-toxic. In previous experiments, the inventors observed that nanoparticles with Hf / Au ratios outside this range were less efficient. In Reference Example 7 below, a product was synthesized in which first and second nanoparticles were electrostatically bonded. The product had an Hf / Au ratio of 86, which is too high to achieve the synergistic electronic effect seen in the NPs of the present invention described herein. These experiments helped define a target ratio (w / w) of first nanoparticle metal content to second nanoparticle metal content, preferably less than 30.

[0085] The metal content of each of the nanoparticles can be measured using methods known to those skilled in the art. For example, the nanoparticle metal content may be determined using inductively coupled plasma optical emission spectroscopy (ICP-OES). According to one embodiment of the present invention, if the first nanoparticles are hafnium oxide (HfO) and the second nanoparticles are gold (Au), the Hf / Au ratio may be in the range of 20 to 30 (w / w), preferably in the range of 25 to 30 (w / w), for example, 25, 26, 27, 28, 29, or 30 (w / w).

[0086] According to one embodiment of the present invention, in which the first nanoparticles are hafnium oxide (HfO2) and the second nanoparticles are iron oxide (Fe3O4), the ratio of Hf / Fe is in the range of 20-30 (w / w), preferably in the range of 25-30 (w / w), for example 25, 26, 27, 28, 29, or 30 (w / w).

[0087] The present inventors have found that NPs having a ratio of first nanoparticle metal content / second nanoparticle metal content falling within the range of 20-30, preferably 25-30, have a radiation enhancer capacity greater than would be expected based on the measured radiation enhancer capacity of the first nanoparticle and the second nanoparticle, each measured separately. This synergistic or cooperative radiation enhancer effect has been demonstrated in the results of the applicant's experiments. The DEF of the NPs of the present invention is greater than the combined effect of the first (1°) and second (2°) nanoparticles taken separately. This effect can be expressed as follows: DEF 本発明NP >DEF 1°ナノ粒子 ×DEF 2°ナノ粒子

[0088] According to one embodiment of the present invention, the first nanoparticles are hafnium oxide first nanoparticles and the second nanoparticles are gold second nanoparticles. Example 3B below is an example of such an embodiment. The radiation enhancer effect of the latter NPs was tested in a clonogenic assay (see Example 4 below). The data in Example 4 below show that the DEF of the (first) hafnium oxide nanoparticles was measured to be 4.49 (±0.266) and the DEF of the (second) gold nanoparticles was measured to be 1.16 (±0.282). The DEF of the NPs of the present invention (hafnium oxide nanoparticles having gold nanoparticles covalently bound to their surface and a hafnium / gold ratio (w / w) of 27) was measured to be 7.88 (±0.736). 7.88 (±0.736) is greater than the combined DEF of the first and second nanoparticles taken separately (1.16 × 4.49 = 5.21). Using a margin of error, taking the highest DEF values ​​for the first and second nanoparticles and the lowest DEF value for the nanoparticles (NPs) of the present invention, the cooperative effect is still seen, i.e., (4.49 + 0.266) x (1.16 + 0.282) = 6.85 and 7.88 - 0.746 = 7.13, where 7.13 > 6.85.

[0089] We have thus identified a specific range of second nanoparticles that allow electronic "coordination" with electrons released after irradiation of the first metal oxide nanoparticle. Furthermore, NPs with metal / metal (w / w) ratios in the range of 20-30 show no additional toxicity compared to the first nanoparticle alone.

[0090] Any biocompatible coating In certain aspects herein, each NP comprised of the first and second nanoparticles of the present invention is coated with a biocompatible surface coating.

[0091] In a preferred embodiment, each NP used in the context of the present invention is coated with a biocompatible material, preferably with an agent exhibiting stealth properties. Indeed, when the NPs of the present invention are administered to a subject via the intravenous (IV) route, a biocompatible coating with an agent exhibiting stealth properties is particularly advantageous for optimizing the biodistribution of the NPs. Such a coating is responsible for the so-called "stealth properties" of the NPs. The agent exhibiting stealth properties may be an agent that exhibits steric hindrance on the NP surface. Such an agent may be selected from, for example, polyethylene glycol (PEG); polyethylene oxide; polyvinyl alcohol; polyacrylate; polyacrylamide (poly(N-isopropylacrylamide)); polycarbamide; biopolymers; polysaccharides such as dextran, xylan, and cellulose; collagen; and zwitterionic compounds such as polysulfobetaine.

[0092] In another preferred embodiment, the NPs can be coated with agents that allow nonspecific interactions with biological targets. Such agents typically result in a negative or neutral charge on the NP surface. This charge can be easily determined by zeta potential measurements, typically performed on NP suspensions whose concentrations vary between 0.2 and 10 g / L, with the particles suspended in an aqueous medium having a pH between 6 and 8.

[0093] Agents that form negative charges on the NP surface can be, for example, phosphates (e.g., polyphosphates, metaphosphates, pyrophosphates, etc.), carboxylates (e.g., citrates or dicarboxylic acids, especially succinic acid), or sulfates. Polyphosphates are preferred. Hexametaphosphates are particularly preferred.

[0094] A complete biocompatible coating of the NPs can be advantageous, especially for intravenous (IV) administration in human patients, to avoid interaction of the particle's surface with any recognition elements of the immune system (macrophages, opsonins, etc.). "Complete coating" refers to the presence of a very high density of biocompatible molecules that can create at least a complete monolayer on the particle's surface.

[0095] The biocompatible coating allows stability of the nanoparticles in biocompatible suspensions, especially in physiological fluids (blood, plasma, serum, etc.), any isotonic or physiological medium, for example, a medium containing glucose (5%) and / or NaCl (0.9%) required for pharmaceutical administration, between pH 6.5 and 7.5.

[0096] Such a biocompatible coating can be obtained by treating the nanoparticles with a surface treatment agent. Stability can be confirmed by dry extractables quantification, measured on nanoparticle suspensions before and after filtration through a 0.22 μm filter.

[0097] Advantageously, the coating ensures or improves the biocompatibility of the particle in vivo and facilitates its optional functionalization (e.g., with spacer molecules, biocompatible polymers, targeting agents, proteins, etc.).

[0098] Optional Targeting The NP can further comprise a targeting agent. Targeting agents typically recognize elements present on target cells, typically cancer cells. Such targeting agents typically act when the NPs of the present invention accumulate at the target site, typically a tumor site. The targeting agent can be any biological or chemical structure that exhibits affinity for a molecule present in the mammalian, particularly human, body. For example, it can be a peptide, oligopeptide or polypeptide, protein, nucleic acid (DNA, RNA, siRNA, tRNA, miRNA, etc.), hormone, vitamin, enzyme, ligand of a molecule expressed by diseased cells, particularly a ligand of a tumor antigen, hormone receptor, cytokine receptor, or growth factor receptor. The targeting agent can be selected, for example, from the group consisting of LHRH, EGF, folate, anti-B-FN antibody, E-selectin / P-selectin, anti-IL-2Rα antibody, and GHRH.

[0099] Route of administration The NPs of the present invention can be administered to a subject using different possible routes, such as local (e.g., intratumoral (IT)) or systemic (e.g., intra-arterial (IA)) administration. Administration may be, for example, subcutaneous, intradermal, intra-arterial (IA), intravenous (IV), airway (inhalation), intraperitoneal, intramuscular, intra-articular, intrathecal, intraocular, or oral route (oral). Preferably, administration is via IT, IV, or IA route. The intratumoral (IT) route is most preferred.

[0100] Repeated injections or administrations of NP can be administered as appropriate.

[0101] Cancer indications for treatment The NPs described herein are typically for use in altering or destroying target cells in mammals, particularly humans, when the cells are exposed to ionizing radiation.

[0102] The invention described herein can be applied to any target cell, particularly a tumor cell, typically in a human patient suffering from cancer.

[0103] The cancer may be, for example, skin cancer, in particular malignant neoplasms associated with AIDS; melanoma; squamous cell carcinoma; cancer of the central nervous system, for example cancer of the brain, cerebellum, pituitary gland, spinal cord, brainstem, eye, or orbit; gastrointestinal cancer such as head and neck cancer, lung cancer, breast cancer, liver or hepatobiliary cancer, colon, rectum, and / or anal cancer, stomach cancer, pancreatic cancer, esophageal cancer; cancer of the bladder or urethra, male genitourinary tract cancer, for example cancer of the prostate, testicles, or penis; gynecological cancer, for example cancer of the cervix, endometrium, ovary, fallopian tubes, vagina, and / or vulva; adrenal and / or retroperitoneal cancer; sarcoma of bone and soft tissue, regardless of its location; or childhood cancer, for example Wilms' cancer, neuroblastoma, central nervous system cancer, or Ewing's sarcoma.

[0104] In a particular embodiment of the invention, the target cells belong to a solid malignant tumor selected from skin cancer, central nervous system cancer, head and neck cancer, lung cancer, breast cancer, gastrointestinal cancer, male genitourinary cancer, gynecological cancer, adrenal and / or retroperitoneal cancer, sarcoma, and childhood cancer.

[0105] Radiation therapy sources In typical embodiments described herein, the NP of the present invention is administered to a subject to be treated, and then the subject is exposed to ionizing radiation. This ionizing radiation is typically selected from X-rays, gamma rays (γ-rays), protons, neutrons, radioisotopes, and / or electrons. Preferred ionizing radiations are X-rays and protons. Even more preferred ionizing radiations are X-rays.

[0106] In a preferred embodiment, the NPs of the invention, or the subjects administered the NPs of the invention, are exposed to ionizing radiation.

[0107] RT encompasses several different treatment modalities, including external beam therapy (including photons, electrons, protons, and other particles) and internal / surface treatments (brachytherapy and radiopharmaceuticals). In preferred embodiments described herein, the ionizing radiation is selected from X-rays, gamma rays, electrons, and protons. In preferred embodiments described herein, the ionizing radiation is selected from X-rays and protons.

[0108] As indicated herein above, suitable radiation is preferably ionizing radiation and can be advantageously selected from the group consisting of X-rays, gamma rays, electron beams (electrons), ion beams (such as protons), and radioisotopes or radioisotope emissions. X-rays are a particularly preferred ionizing radiation.

[0109] Ionizing radiation is standard of care. It is typically from about 2 KeV to about 25,000 KeV, particularly from about 2 KeV to about 6,000 KeV (i.e., 6 MeV) (LINAC sources).

[0110] Generally, and in a non-limiting manner, the following X-rays can be applied in different circumstances to excite the nanoparticles described herein: -2-50 keV surface X-rays: Excite nanoparticles near the skin surface (penetration of several millimeters); -50 to 150 keV X-rays: not only in diagnosis but also in therapy; - 200-500 keV X-rays (normal voltage) capable of penetrating 6 cm of biological tissue; X-rays between -1000 keV and 25000 keV (megavoltage).

[0111] Radioisotopes can alternatively be used as ionizing radiation (typically in the context of Curie therapy or brachytherapy). In particular, iodine I-125 (t = 60.1 days), palladium Pd-103 (t = 17 days), cesium Cs-137, strontium Sr-89 (t = 50.5 days), samarium Sm-153 (t = 46.3 hours), and iridium Ir-192 can be used advantageously.

[0112] Electron beams may also be used as ionizing radiation, typically having energies between 4 MeV and 25 MeV.

[0113] In certain embodiments, specific monochromatic radiation sources can be used to selectively generate X-ray radiation at energies near or corresponding to desired X-ray absorption edges of high-Z elements in particles selected for use in the context of the present invention.

[0114] Preferentially, the ionizing radiation is X-rays obtained from a linear accelerator (LINAC) or is protons.

[0115] In the context of the present invention, cells are exposed to ionizing radiation in the context of a radiotherapy regimen selected from a conventional fractionation regimen, a hyperfractionation regimen, an (accelerated) hypofractionation regimen, and a stereotactic body radiotherapy (SBAR) regimen.

[0116] The radiotherapy protocol for each patient is typically defined by the clinical team according to the characteristics of the patient's cancer, the patient's clinical stage, the patient's health status, etc. Thus, the radiotherapy protocol may correspond to curative treatment, palliative treatment, simultaneous or sequential systemic therapy / radiotherapy, preoperative radiotherapy or postoperative radiotherapy.

[0117] In a preferred embodiment, the radiation therapy regimen (also referred to as a radiation therapy schedule) is typically conventional fractionation comprising or consisting of 1.6 Gy to 2.25 Gy per fraction (e.g., 1.6, 1.8, 2.0, 2.12, 2.25 Gy per fraction) daily (Monday-Friday, i.e., 5 consecutive days per week) for 5 to 7 weeks.

[0118] In another embodiment, the radiation therapy regimen is typically multifractionated, comprising or consisting of 1.2 Gy per fraction twice daily for 7 weeks (e.g., 79.2 Gy to 81.6 Gy twice daily for 7 weeks).

[0119] In another embodiment, the radiotherapy regimen typically comprises or consists of greater than 2.5 Gy per fraction, typically 34 Gy delivered in 10 fractions, or 40 Gy delivered in 15 fractions, ideally hypofractionated over 2 weeks up to 4 weeks (accelerated).

[0120] In another embodiment, the radiation therapy regimen typically comprises or consists of 45-60 Gy delivered in 3 fractions, 48-50 Gy delivered in 4 fractions, or 50-55 Gy delivered in 5 fractions, typically over 2 weeks.

[0121] The nanoparticles of the present invention, or compositions comprising said nanoparticles, are suitable for use in the above clinical situations, particularly when fractionated radiotherapy is used, since in fractionated radiotherapy the radiation enhancer is repeatedly exposed to ionizing radiation, typically over a period of at least two weeks, preferably three or four weeks.

[0122] The nanoparticles of the present invention are effective and stable to ensure optimal radiation enhancement effects, thus ensuring an optimal risk-to-benefit ratio for the patient throughout the entire duration of the RT session.

[0123] The nanoparticles of the present invention are also useful in radioimmunotherapy, in which cancer patients undergo radiation therapy and immunotherapy. It has been published that HfO2 nanoparticles, when exposed to ionizing radiation, act as immunomodulators in the tumor environment (see International Publication Nos. 2016189125 and 2022096291). Thus, the NPs of the present invention, when exposed to ionizing radiation, can exploit the immune system in a manner similar to that described in the latter patent applications. In one embodiment of the present invention, the NPs may be administered in combination with at least one immunotherapeutic agent. Patients may receive the NPs (and radiation) before, simultaneously with, or after receiving immunotherapy.

[0124] Visualization of biological tissue, especially soft tissue In another preferred embodiment, the NPs described herein are intended for use in visualizing soft tissues in mammalian, preferably human, patients, particularly for diagnostic purposes, typically to detect tumor cells. For example, hafnium oxide, as a radiopaque material, can be used as a contrast agent for CT scan imaging, thereby enabling tumor cell detection. For example, NPs of the present invention composed of high-Z metal oxide materials that behave as radiopaque and radiation-enhancing materials can be used for tumor detection and post-surgical tumor bed delineation, both to visualize tumor bed volume and to enhance post-surgical radiation therapy that can be delivered to improve local control of cancer recurrence. Optionally, the NPs of the present invention may be embedded in a gel or hydrogel to aid their deposition in the tumor bed. Suitable gel formulations are described in U.S. Pat. No. 10,588,987 (B2).

[0125] Furthermore, noble metal nanoparticles, such as gold, excel in bioimaging detection due to their tunable photoluminescence, large Stokes shift, low photobleaching, and good biocompatibility. When excited by external light (UV-visible or infrared), excited surface plasmon electrons de-excite / decay through the photothermal effect. The photothermal effect generates thermal contrast during nonradiative plasmon decay. Recently, gold has been used for imaging plasmonic nanoparticles, a technique called photothermal imaging (PTI). Generally, PTI requires two beams: a heating beam and a probe beam. When the LSP of a nanoparticle is excited by the heating beam, the temperature of the nanoparticle and its surroundings increases, resulting in a change in refractive index. This photothermal effect-induced refractive index change can be detected using an additional nonresonant laser source, called the probe beam. In the field of using plasmonic nanoparticles for biomedical imaging, imaging modalities based on the photoacoustic effect (i.e., photoacoustic tomography, PAT) as well as direct thermal imaging via a thermographic camera can also be envisioned. Plasmonic nanoparticles may also be used in optical fluorescence or optical coherence tomography (OCT), especially for diagnostic purposes (skin cancer).

[0126] Photothermal therapy (activated by a laser and alternating magnetic field) In combination with radiotherapy (RT), the NPs of the present invention may also be used in photothermal therapy when the second nanoparticle is a noble metal NP, with a view to increasing the efficacy of killing cancer cells.

[0127] Indeed, when noble metal NPs are exposed to light (UV-visible or infrared), free electrons on the nanoparticle surface are excited, causing the conduction band electrons to oscillate collectively at the same frequency, constituting a localized surface plasmon resonance (LSPR). During the final relaxation process after localized surface plasmon (LSP) excitation of noble metal nanoparticles, typically by external light (UV-visible or infrared), the photoexcitation energy, exceeding the Fermi energy, is transferred to the metal lattice via electron-phonon collisions. This relaxation process induces heat dissipation, releasing thermal energy into the surrounding medium. This phenomenon constitutes the photothermal effect. When excited by a laser beam or laser pulse, the NPs of the present invention can locally increase the temperature of surrounding cancer cells, resulting in tumor cell death.

[0128] In the same vein, the NPs of the present invention can also be used for magnetic hyperthermia when the second NP is a metal oxide NP. Indeed, when exposed to low-frequency electromagnetic waves (alternating magnetic fields), small (<10 nm) iron oxide NPs begin to rotate due to their magnetic spin rotation, thus locally increasing the temperature of surrounding cancer cells and leading to tumor cell death.

[0129] composition The inventors also describe compositions comprising the NPs of the present invention (or aggregates thereof) that are composed of first nanoparticles of at least one high-Z metal oxide or mixed high-Z metal oxide material, where Z is 40 or greater, and the nanoparticles are present in a density of 7 g / cm 3 or more (≧) and 15g / cm 3 and have a density less than (<) and have covalently attached to their surfaces smaller second nanoparticles of at least one precious metal and / or nanoparticles of at least one material that is a Fenton or Fenton-like reaction catalyst, preferably selected from metal oxides, metal sulfides, metal selenides, or metal sulfide / selenides. The composition comprises a) NPs or aggregates thereof optionally coated with a biocompatible surface coating, and b) a pharmaceutically acceptable carrier, vehicle, or support.

[0130] The pharmaceutical compositions described herein, in preferred embodiments described herein, are for use in the prevention or treatment of cancer in a human patient.

[0131] In one aspect of the invention, a composition containing the particles is for use in altering or destroying target cells in a mammal, particularly a human, when the cells are exposed to ionizing radiation.

[0132] The composition may be in the form of a solid, liquid (NPs in suspension), aerosol, gel, paste, etc. Preferred compositions are in liquid or gel form. Particularly preferred compositions are in liquid form.

[0133] The carrier used may be any classical pharmaceutical support known to those skilled in the art, such as saline, isotonic, sterile, buffered solutions, or non-aqueous vehicle solutions.

[0134] The pharmaceutical compositions described herein may comprise a vehicle or support selected from liposomes, viral vectors, virus-like particles, albumin-containing carriers, inorganic polymers, and organic polymers known to those skilled in the art. The vehicle or support may also be any other suitable vehicle or support known to those skilled in the art.

[0135] The composition may also contain stabilizers, surfactants, polymers, etc. It may be formulated, for example, as an ampoule, an aerosol, a bottle, a tablet, or a capsule by using techniques of pharmaceutical formulation known to those skilled in the art.

[0136] Generally, the liquid or gel form of the composition contains from about 0.05 g / L to about 450 g / L of NP, for example, from about 0.05 g / L to about 250 g / L of NP, preferably at least about 10 g / L, 11 g / L, 12 g / L, 13 g / L, 14 g / L, 15 g / L, 16 g / L, 17 g / L, 18 g / L, 19 g / L, 20 g / L, 21 g / L, , 22g / L, 23g / L, 24g / L, 25g / L, 26g / L, 27g / L, 28g / L, 29g / L, 30g / L, 31g / L, 32g / L, 33g / L L, 34g / L, 35g / L, 36g / L, 37g / L, 38g / L, 39g / L, 40g / L, 41g / L, 42g / L, 43g / L, 44g / L, 45g / L, 46g / L, 47g / L, 48g / L, 49g / L, 50g / L, 51g / L, 52g / L, 53g / L, 54g / L, 55g / L, 56g / L, 57g / L, 58g / L, 59g / L, 60g / L, 61g / L, 62g / L, 63g / L, 64g / L, 65g / L, 66g / L, 67g / L, 68g / L, 69g / L, 70g / L, 71g / L, 72g / L, 73g / L, 74g / L, 75g / L, 76g / L, 77g / L, 78g / L, 79g / L, 80g / L, 85g / L, 90g / L, 95g / L, 100g / L, 150g / L, 200g / L, 250g / L, 300g / L, 350g / L, or 400g / L of NPs.

[0137] In certain embodiments, the composition further comprises or is used in combination with at least one additional therapeutic agent for treating cancer, for example, an immunotherapeutic agent or a cytotoxic agent.

[0138] The concentration of particles in a composition can be measured by dry extract, which is ideally measured after a drying step of a suspension containing the particles in a drying oven.

[0139] In another preferred embodiment, the pharmaceutical compositions described herein are for use in visualizing tissues, particularly soft tissues, of human patients, e.g., for diagnostic purposes, to allow visualization of tumor cells.

[0140] In one aspect of the invention, a composition containing the particles is for use in altering or destroying target cells in a mammal, particularly a human, when the cells are exposed to ionizing radiation.

[0141] The composition may be in the form of a solid, liquid (NPs in suspension), aerosol, gel, paste, etc. Preferred compositions are in liquid or gel form. Particularly preferred compositions are in liquid form.

[0142] The following examples are intended to illustrate the present invention but are not intended to limit the scope of the invention. [Example]

[0143] Reference Example 1: Sodium hexametaphosphate coated hafnium oxide nanoparticle suspension Hafnium oxide (HfO2) nanoparticles were synthesized by precipitating hafnium chloride (HfCl4) with tetramethylammonium hydroxide (TMAOH) at basic pH. The resulting precipitate was transferred to an autoclave and heated to 120-300 °C for crystallization. After cooling, the suspension was washed with deionized water and acidified. Sodium hexametaphosphate solution was added to the suspension to adjust the pH to 6.5-7.5.

[0144] Example 2: Gold nanoparticle synthesis In a 250 mL Erlenmeyer flask placed in an ice bath, 10 mL of 5 mM HAuCl4·3H2O (gold(III) chloride trihydrate - Sigma Aldrich, USA) was mixed with 25 mL of 10 mM sodium citrate (Sigma Aldrich, USA) and 65 mL of distilled water. When the solution temperature reached 4 °C, 1 mL of sodium borohydride, NaBH4 (0.1 mM) was rapidly introduced with vigorous stirring. The solution immediately turned red.

[0145] The nanoparticle suspension was reconcentrated and washed at RT using an Amicon® Ultra-15 centrifugal filter 30 kDa (700 G for 60 min).

[0146] The gold content of the suspension was determined using inductively coupled plasma optical emission spectroscopy (ICP-OES).

[0147] High-resolution transmission electron microscopy (TEM) micrographs were used to visualize the gold nanoparticles (Figure 1A). A high-resolution electron microscope, JEOL 2100 Plus, was used for image analysis. The average nanoparticle diameter was calculated over 208 nanoparticles and found to be 5.7 + / - 1.1 nm.

[0148] The zeta potential was determined by measuring the electrophoretic mobility of the nanoparticles (Zetasizer Nano ZS, Malvern) by diluting the nanoparticle suspension in 1 mM NaCl solution at pH 7 (final concentration 0.3 g / L). The zeta potential at pH 7 was found to be -29 mV.

[0149] Example 3.A: Functionalization of HfO2 Nanoparticles (with Amine Groups) Hafnium oxide (HfO2) nanoparticles were synthesized by precipitating hafnium chloride (HfCl4) with tetramethylammonium hydroxide (TMAOH) at basic pH. The resulting precipitate was transferred to an autoclave at temperatures between 120 °C and 300 °C for crystallization. After cooling, the suspension was washed with deionized water and acidified.

[0150] 3 mL of the HfO2 particle suspension was mixed with 15 mL of absolute ethanol (Fisher Scientific, UK). The pH was adjusted to 3.2, and (3-aminopropyl)triethoxysilane (APTES) (Sigma-Aldrich, USA) was added to the nanoparticle suspension at a ratio of 1:1. The resulting suspension was sonicated for 30 minutes and stirred overnight. The white product was collected and washed with ethanol. Then, sterile water / ethanol (v / v) (1:1) was used. Finally, the white product was dispersed in filtered water, and the pH was adjusted to 7.5.

[0151] The hydrodynamic diameter was determined by dynamic light scattering (DLS) using a Zetasizer Nano ZS (Malvern) DLS instrument with a scattering angle of 173° and a laser emitting at 633 nm. The nanoparticle suspension was diluted with water (final concentration 2 g / L). The hydrodynamic diameter of the nanoparticles in the suspension thus obtained was equal to 52 nm, and the polydispersity index (size distribution of the nanoparticle population) was 0.120.

[0152] The zeta potential (determined at a final concentration of 2 g / L using the conditions described in Example 2) was measured at 40 mV.

[0153] Example 3B: HfO2 nanoparticles modified with gold nanoparticles 5.8 mL of the gold nanoparticle suspension obtained in Example 2 was diluted with 40 mL of sterile water, and the pH was set to approximately 5.8. 150 μL of a solution of 1-ethyl-3-(3'-dimethylaminopropyl)carbodiimide, HCl (EDAC) (Merck) (6.5 mM) was added dropwise. The pH was adjusted to approximately 5.8. After stirring, the resulting mixture was washed three times with water and then dispersed in 40 mL of filtered water. The pH was adjusted to approximately 7.5, and the suspension was maintained at room temperature with stirring.

[0154] Then, 1 mL of the suspension of Example 3A (diluted to 15 g / L) was added with stirring. After 2 days of reaction, the resulting suspension was centrifuged to isolate the resulting nanoparticles, which were then redispersed in 4 mL of filtered water.

[0155] The surface coating process was then carried out using sodium hexametaphosphate (HMP - Univar, USA). HMP was added to the nanoparticle suspension at an acidic pH in a ratio of 0.1 (HMP / HfO2 w / w). After stirring, the pH was adjusted to around 7, and the solution was washed by centrifugation and dispersed in 2 mL of filtered water.

[0156] The hydrodynamic diameter was determined by DLS using the same conditions as described in Example 3A, for example, with a final concentration of 0.7 g / L. The hydrodynamic diameter of the nanoparticles thus obtained in suspension was equal to 51 nm, and the polydispersity index (dispersion of the nanoparticle population in size) was 0.185.

[0157] The zeta potential at pH 7 (determined at a final concentration of 0.7 g / L using the conditions described in Example 2) was found to be -38 mV.

[0158] The hafnium and gold content of the suspension was determined using inductively coupled plasma optical emission spectroscopy (ICP-OES). The Hf / Au ratio was 27 (w / w).

[0159] High-resolution transmission electron microscope (TEM) micrographs (Figure 1B and C) confirmed the presence of gold nanoparticles on the HfO particles. A Jeol 2100 Plus was used for the analysis.

[0160] Example 4: Evaluation of Radiation Enhancement of Example 3B The performance of the gold nanoparticle-modified HfO2 nanoparticles of Example 3B activated by ionizing radiation was evaluated by clonogenic survival assays to define the radiation sensitivity parameter (SF) and dose enhancement factor (DEF), as described below.

[0161] CT26 cells were seeded in 6-well plates at 100–1500 cells / well in triplicate. The culture medium was RPMI supplemented with 10% FCS and 1% penicillin-streptomycin to promote clone formation. A concentration of 800 μM HfO2 was tested in each experiment. After cells attached to the plate, each nanoparticle suspension was added overnight (15 h). Cells were irradiated 15–16 h after treatment using a 160 keV irradiator with a single dose delivery (0 Gy [sham control] and 4 Gy). Cells were cultured at 37°C in a 5% CO2 humidified atmosphere for up to 7 days to allow colony formation. Colonies were fixed, stained with crystal violet solution, and individual colonies were counted to assess plating efficiency and post-treatment viability. Only clones with more than 50 cells were considered viable.

[0162] Data Analysis: The plating efficiency (PE), which represents the ratio of the number of colonies formed to the number of cells plated, was calculated for the control and viability from each experiment as follows:

[0163]

number

[0164] Fraction survival (SF) is the number of viable cells after treatment, normalized to the control.

[0165]

number

[0166] For each experiment, the SF average from triplicates was estimated to calculate the enhancement factor (DEF) according to the following formula:

[0167]

number

[0168] Results: The data are shown in Figure 2. 4 Gy (SF 4Gy) survival rates are summarized in Table 4 below.

[0169] [Table 4]

[0170] HfO2 nanoparticles (HfO2NP in Figure 2) showed a radiation enhancer effect at a dose of 4 Gy, with an SF of 4.0 (±0.68) compared to 17.9 (±2.11) with radiation alone (vehicle in Figure 2). Treatment with the NPs of the present invention (HfO2@Au in Figure 2) from Example 3B above resulted in an SF of 2.3 (±1.70), which is significantly lower compared to the HfO2 nanoparticle group. The NPs of Example 3B showed an equivalent Hf +4 The nanoparticles of Example 3B have a significantly higher radiation-enhancing effect than HfO2 nanoparticles at a concentration of 1.5 (±2.82). Gold nanoparticles (shown as Au NPs in Figure 2) have an SF of 15.5 (±2.82), which is not significantly different from the vehicle. In this experiment, treatment of cells with the nanoparticles of Example 3B resulted in a greater radiation-enhancing effect than expected. In fact, the nanoparticles of Example 3B exhibited a synergistic radiation-enhancing effect that was greater than the combined radiation-enhancing effect observed for HfO2 nanoparticles and Au nanoparticles taken separately.

[0171] Example 5: Synthesis of Fe3O4 ultrasmall nanoparticles. The protocol was adapted from Shen (2013, One-step Synthesis of Monodisperse, Water-Soluble Ultra-small Fe3O4 Nanoparticles for Potential Bio-application. Nanoscale, 5(5), 2133-2141).

[0172] 2 mmol of anhydrous FeCl3 (Fisher Chemical, Fisher BioReagents, USA) was dissolved in 20 mL of diethylene glycol (Fluka, Sigma-Aldrich, Belgium), and 1.3 mmol of citric acid trisodium salt dihydrate 99% purity (ACROS ORGANIC, Sigma-Aldrich, Belgium) was added with vigorous stirring. The mixture was then heated at 80 °C with vigorous stirring to form a clear solution. 9 mmol of anhydrous sodium acetate (Sigma-Aldrich, Germany) was then added to the solution with vigorous stirring. The resulting solution was transferred to a Teflon-lined stainless steel autoclave (25 mL capacity) and placed in an oven preheated to 200 °C for 10 hours. After cooling to room temperature, the black product was collected by centrifugation and washed three times with ethanol. The black powder was redispersed in 30 mL of sterile water by sonication.

[0173] High-resolution transmission electron microscopy (TEM) micrographs (Figure 3A) showed ultrasmall Fe3O4 nanoparticles (Figure 3A). The average diameter was calculated over 300 nanoparticles and found to be equal to 5.6 + / - 2.2 nm.

[0174] The zeta potential of ultrasmall Fe3O4 at pH 7 was found to be equal to -44 mV.

[0175] Example 6: HfO2 nanoparticles modified with iron oxide nanoparticles An aqueous suspension of HfO2 nanoparticles modified with Fe3O4 nanoparticles was obtained by the assembly of both nanoparticles via amide bonds. 8.8 mL of the Fe3O4 ultrasmall nanoparticles obtained in Example 5 was diluted in 243 mL of sterile water, and the pH was adjusted to 5.8. 30 mL of a solution of 1-ethyl-3-(3'-dimethylaminopropyl)carbodiimide, HCl (EDAC) (Merck) (34 mM) was added dropwise. The pH was adjusted to approximately 5.8. After stirring for over 1 hour, the pH was adjusted again to approximately 5.8, and stirring was continued for another hour at room temperature. The resulting mixture was then washed three times by centrifugation and dispersed in 250 mL of sterile water using ultrasonication. The pH was then adjusted to 7.5, and the suspension was maintained under stirring at room temperature. 3.6 mL of the suspension from Example 3A was then added with stirring. After 2 hours of reaction, the suspension was centrifuged three times for 20 minutes at 3000 RPM, and finally redispersed in 10 mL of sterile water.

[0176] The surface coating process was then carried out using sodium hexametaphosphate (HMP - Univar, USA). HMP was added to the nanoparticle suspension at an acidic pH in a ratio of 0.03 (HMP / HfO2 w / w). The mixture was then sonicated for 5 minutes and centrifuged at 4000 rpm for 20 minutes. The product was finally dispersed in 10 mL of sterile water, and the pH was adjusted to approximately 7.

[0177] High-resolution transmission electron microscopy (TEM) micrographs (FIGS. 3B and 3C) were used to visualize HfO2 nanoparticles decorated with Fe3O4 nanoparticles.

[0178] The hydrodynamic diameter was equal to 77 nm and the polydispersity index (dispersion of the nanoparticle population in size) was 0.122.

[0179] The zeta potential was found to be equal to -30 mV.

[0180] The hafnium and iron content of the suspension was determined using inductively coupled plasma optical emission spectroscopy (ICP-OES). The Hf / Fe ratio was 27 (w / w).

[0181] Reference Example 7: Hafnium oxide primary nanoparticles with gold secondary nanoparticles bound to the surface by electrostatic interactions. A HAuCl solution (1 g / L, 4.2 mL) (gold III chloride trihydrate - Sigma Aldrich, USA) and a polyacrylic acid solution (1 wt%, 0.25 mL) (Sigma Aldrich, USA) were diluted to 62 mL with deionized water under vigorous stirring in an ice bath. After 15 minutes, a NaBH solution (0.1 mol / L, 0.5 mL) was added to the above solution, resulting in a deep brick-red solution, indicating the formation of Au colloids.

[0182] High-resolution transmission electron microscopy (TEM) micrographs were used to visualize the gold nanoparticles. The average nanoparticle diameter was calculated over 200 nanoparticles and found to be 5.3 + / - 1.3 nm.

[0183] Then, HfO2 suspension (120 g / L; 0.2 mL) was added. After stirring, the pH was adjusted to 7, and the solution was washed three times by centrifugation and dispersed in filtered water.

[0184] The hafnium and gold content of the suspension was determined using inductively coupled plasma optical emission spectroscopy (ICP-OES). The Hf / Au ratio was 86 (w / w).

[0185] The hydrodynamic diameter was determined by DLS at a final concentration of 0.1 g / L, using the same conditions as described, for example, in Example 3A. The hydrodynamic diameter of the nanoparticles in the suspension thus obtained was equal to 77 nm, and the polydispersity index (dispersion of the size of the nanoparticle population) was 0.114.

[0186] The Hf / Au ratio of 86 in this product is too high to obtain the synergistic electronic effect seen in the case of the inventive NPs described in Example 3B.

[0187] [Embodiment] (1) Nanoparticles (NP) or aggregates of nanoparticles (NP), wherein the NPs are composed of at least one metal oxide (M) having an atomic number Z of at least 40. x O y ) or mixed metal oxides (M x M' z O y ) first nanoparticles, and the first nanoparticles are 3 or more (≧) and 15g / cm 3 and a second, smaller nanoparticle having a density less than (<) is covalently attached to the surface of the first nanoparticle via a linker, the second nanoparticle comprising: a. at least one noble metal selected from gold (Au), platinum (Pt), ruthenium (Ru), rhodium (Rh), palladium (Rd), osmium (Os), and iridium (Ir), and / or b. at least one metal oxide, metal hydroxide, metal oxyhydroxide, metal peroxide, metal sulfide, metal selenide, or metal sulfide / selenide that is a Fenton or Fenton-like reaction catalyst, wherein the metal is selected from the group consisting of Fe, Co, Ni, Cu, and Mn; and optionally a negatively or neutrally charged biocompatible surface coating, wherein the ratio of the first nanoparticle metal content to the second nanoparticle metal content is less than 30 weight / weight (w / w). (2) The high-Z metal oxide (M x O y 2. The nanoparticle (NP) of embodiment 1, wherein ZnO is HfO2 or ZrO2. (3) The nanoparticle (NP) according to any one of the preceding claims, wherein the second nanoparticle is made of gold (Au). (4) The nanoparticles (NP) according to any one of the preceding claims, wherein the second nanoparticles are composed of iron oxide (Fe3O4). (5) The nanoparticles (NPs) according to any one of embodiments 1 to 4, wherein the ratio of the first nanoparticle metal content to the second nanoparticle metal content is 20 to 30 weight / weight (w / w).

[0188] (6) The nanoparticle (NP) according to any one of embodiments 1 to 5, wherein the linker on the first nanoparticle is an aminosilane and the linker on the second nanoparticle is citrate. (7) The nanoparticle NP according to any one of embodiments 1 to 6, wherein the first nanoparticle has a size of 40 to 100 nm. (8) The nanoparticles (NP) according to any one of embodiments 1 to 6, wherein each of the second nanoparticles has a size of 2 to 15 nm. (9) The nanoparticle (NP) or aggregate of nanoparticles (NP) according to any one of embodiments 1 to 8 for use in altering or destroying target tumor cells in a mammal when the cells are exposed to ionizing radiation selected from X-rays, gamma rays, and protons. (10) The nanoparticle (NP) or aggregate for use according to embodiment 9, wherein the cells are exposed to ionizing radiation in the context of a radiotherapy regimen selected from a conventional fractionation regimen, a hyperfractionation regimen, an (accelerated) hypofractionation regimen, and a Stereo Ablative Body Radiotherapy (SBAR) regimen.

[0189] (11) The nanoparticles (NPs) or aggregates for use according to any one of embodiments 9 to 10, wherein the target cells are derived from a solid malignant tumor selected from skin cancer, central nervous system cancer, head and neck cancer, lung cancer, breast cancer, gastrointestinal cancer, male genitourinary cancer, gynecological cancer, adrenal and / or retroperitoneal cancer, sarcoma, and childhood cancer. (12) A nanoparticle (NP) or an aggregate of nanoparticles (NP) according to any one of embodiments 1 to 8 for use in visualizing soft tissues and detecting tumor cells in a mammal. (13) A composition comprising: a) the nanoparticles (NPs) or aggregates thereof according to any one of embodiments 1 to 8, or a mixture thereof; and b) a pharmaceutically acceptable carrier, vehicle, or support. (14) The composition according to embodiment 13, for use in a mammal, particularly a human, to alter or destroy target tumor cells when the cells are exposed to ionizing radiation. (15) The composition according to embodiment 13, for use in visualizing soft tissues and detecting tumor cells in mammals using CT scans.

Claims

1. Nanoparticles (NP) or aggregates of nanoparticles (NP), wherein said NPs are composed of at least one metal oxide (M) having an atomic number Z of at least 40. ｘ O ｙ ) or mixed metal oxides (M ｘ M' ｚ O ｙ ) first nanoparticles, wherein the first nanoparticles are ３ or more (≧) and 15 g / cm ３ a second nanoparticle having a density less than (<) and smaller than (<) is covalently attached to the surface of the first nanoparticle via a linker, the second nanoparticle comprising: a. at least one noble metal selected from gold (Au), platinum (Pt), ruthenium (Ru), rhodium (Rh), palladium (Rd), osmium (Os), and iridium (Ir), and / or b. at least one metal oxide, metal hydroxide, metal oxyhydroxide, metal peroxide, metal sulfide, metal selenide, or metal sulfide / selenide that is a Fenton or Fenton-like reaction catalyst, wherein the metal is selected from the group consisting of Fe, Co, Ni, Cu, and Mn; and optionally a negatively or neutrally charged biocompatible surface coating, wherein the ratio of the first nanoparticle metal content to the second nanoparticle metal content is less than 30 weight / weight (w / w).

2. The high Z metal oxide (M ｘ O ｙ ) is HfO ２ or ZrO ２ The nanoparticle (NP) of claim 1,

3. The nanoparticle (NP) according to claim 1 or 2, wherein the second nanoparticle is made of gold (Au).

4. The second nanoparticles are iron oxide (Fe ３ O ４ 3. The nanoparticle (NP) according to claim 1 or 2, which is composed of:

5. 2. The nanoparticles (NP) of claim 1, wherein the ratio of the first nanoparticle metal content to the second nanoparticle metal content is 20-30 weight / weight (w / w).

6. The nanoparticle (NP) of claim 1 , wherein the linker on the first nanoparticle is an aminosilane and the linker on the second nanoparticle is citrate.

7. The nanoparticle NP according to claim 1, wherein the first nanoparticle has a size of 40 to 100 nm.

8. The nanoparticle (NP) of claim 1, wherein each of the second nanoparticles has a size of 2 to 15 nm.

9. 10. The nanoparticle (NP) or aggregate of nanoparticles (NP) of claim 1 for use in altering or destroying target tumor cells in a mammal when the cells are exposed to ionizing radiation selected from X-rays, gamma rays, and protons.

10. 10. The nanoparticle (NP) or aggregate for use according to claim 9, wherein the cells are exposed to ionizing radiation in the context of a radiotherapy regimen selected from a conventional fractionation regimen, a hyperfractionation regimen, an (accelerated) hypofractionation regimen, and a stereotactic body radiotherapy (SBAR) regimen.

11. 11. The nanoparticles (NPs) or aggregates for use according to claim 9 or 10, wherein the target cells are derived from a solid malignant tumour selected from skin cancer, central nervous system cancer, head and neck cancer, lung cancer, breast cancer, gastrointestinal cancer, male genitourinary cancer, gynecological cancer, adrenal and / or retroperitoneal cancer, sarcoma, and childhood cancer.

12. 10. The nanoparticle (NP) or aggregate of nanoparticles (NP) of claim 1 for use in visualizing soft tissue and detecting tumor cells in a mammal.

13. A composition comprising: a) the nanoparticles (NPs) of claim 1 or aggregates thereof, or a mixture thereof; and b) a pharmaceutically acceptable carrier, vehicle, or support.

14. 14. A composition according to claim 13 for use in altering or destroying target tumour cells in a mammal, particularly a human, when said cells are exposed to ionising radiation.

15. 14. The composition of claim 13 for use in visualizing soft tissue and detecting tumor cells in a mammal using CT scanning.

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