Surface-modified gadolinium- and terbium-fluoride nanoparticles, preparation thereof, and use thereof in imaging and treatment of a tumour

Abstract

The invention relates to nanoparticles of GdaTbbF3, where a = 0.50 to 0.95, b = 0.05 to 0.50 and a + b = 1, which are surface-modified by at least one biocompatibility ligand and by at least one photosensitizer that absorbs in the same wavelength band as the emission wavelength band of terbium, namely between 520 and 560 nm.

Description

Surface-modified gadolinium terbium fluoride nanoparticles: their preparation and use in imaging and tumor treatment

[0001] The present invention relates to gadolinium and terbium fluoride nanoparticles, surface modified by at least one biocompatibility ligand and by at least one photosensitizer, as well as their preparation process and their use in imaging and treatment of a tumor.

[0002] Spectral photon-counting computed tomography (SPCCT) is emerging as a promising new imaging modality in diagnostic radiology. Its sensors, called photon-counting detectors (PCDs), count each photon and classify them by energy level. This makes it possible not only to perform the decomposition of two materials (for example, water and iodine), but also K-threshold imaging to generate additional specific mapping. K-threshold imaging is essential for distinguishing between two contrast agents. This characterization provides specific information about elements whose K-threshold lies within the CT imaging energy range (approximately 40 to 140 keV).Thanks to this approach, recent animal studies have shown that SPCCT can differentiate between two contrast agents in vivo, for example, by combining them simultaneously in the vascular and peritoneal compartments or by injecting them intravenously. Another important advantage of spectral imaging is the ability to measure the absolute concentration of contrast agents.

[0003] The development of new contrast agents exploiting the specific attenuation associated with the K-line remains necessary to optimize and fully utilize SPCCT technology. It has been discovered that certain nanoparticles can be used as contrast agents for SPCCT imaging, enabling the acquisition of very high-definition, nanoparticle-specific images, thus opening new perspectives for imaging, particularly for diagnostics and theranostics.

[0004] Zhang et al. Bioconjugate Chem. 2019, 30, 2191−2200 described terbium-doped mixed gadolinium and sodium fluoride nanoparticles with a rose Bengale photosensitizer for use in X-ray excitation photodynamic therapy.

[0005] For such particles to be used most effectively in therapy, their concentration in the formulation to be injected into the patient must be as high as possible. It is therefore important to obtain a stable suspension without the nanoparticles aggregating and settling within it.

[0006] To this end, the present invention relates to Gd nanoparticles a Tb bF3, where a = 0.50 to 0.95, b = 0.05 to 0.50 and a+b = 1, surface modified by at least one biocompatibility ligand and by at least one photosensitizer absorbing in the wavelength band of 520 to 560 nm under excitation of the nanoparticles by X-rays.

[0007] When nanoparticles are exposed to X-rays, the inorganic core of gadolinium fluoride and terbium emits scintillation radiation in response. This scintillation radiation is then absorbed by the photosensitizer, which subsequently leads to the generation of reactive oxygen species (ROS).

[0008] Nanoparticles are defined by ISO 80004-1:2023 as objects whose three external dimensions are on the nanometric scale, this scale itself being a length scale extending approximately from 1 nm to 100 nm.

[0009] Nanoparticles can range in size from 3 to 60 nm, particularly from 10 to 50 nm, as measured in suspension in water by dynamic light scattering (DLS). ISO / TS 80004-1:2015 describes such a measurement method.

[0010] In particular, a = 0.80 to 0.95, b = 0.05 to 0.20, in particular a = 0.90 and b = 0.10.

[0011] A biocompatibility ligand can be chosen from: polymers whose chain is chosen from: , with n = 10 to 80, in particular 19 or 20; , with p = 6 to 50, , with q = 5 to 25, in particular 25, and R representing hydrogen or a C1-C3 alkyl radical, such as methyl, ethyl, or propyl, , with r = 8 to 60,

[0012] and which carries a functionality allowing its direct or indirect grafting onto Gd nanoparticles a Tb b F3; bovine serum albumin; sodium triphosphate (TPP) formula .

[0013] In one particular embodiment, the photosensitizer is Rose Bengal.

[0014] In another particular embodiment, the photosensitizer is merocyanine 540, which absorbs in the green.

[0015] The nanoparticles according to the invention can be modified on the surface both by grafting a PEG-phosphonate as a biocompatibility ligand of formula:

[0016] in which m = 10 to 80, in particular 19 or 20, and by grafting a bifunctional ligand of formula:

[0017] in which x = 1 to 10, in particular 1 to 5, the rose Bengal being grafted by its reaction with an available function, such as an amine function, of the bifunctional ligand.

[0018] When x is 1 in the bifunctional ligand of formula , the ligand is then aminomethylphosphonic acid (AMPA).

[0019] Surface modification of nanoparticles by grafting creates a covalent bond between the nanoparticles and the compounds grafted onto them. This improves the chemical and long-term colloidal stability of the resulting nanoparticles.

[0020] The molar ratio of PEG-phosphonate to the bifunctional ligand can be from 20:80 to 90:10, particularly from 50:50 to 80:20

[0021] The nanoparticles according to the invention can be surrounded by a silica layer in which the photosensitizer(s) is / are trapped, and then grafted onto said silica layer by a PEG-silane as a biocompatibility ligand, PEG-silane being represented by the formula:

[0022] in which u = 20 to 50, in particular 45.

[0023] The present invention also relates to a method for preparing nanoparticles containing PEG-phosphonate as a biocompatibility ligand, as defined above, characterized in that it comprises the following steps: heating for 1-24 hours, at a temperature of 25 to 80°C, an aqueous mixture of PEG-phosphonate and a bifunctional ligand of formula with x = 1 to 10, specifically 1 to 5, and add Gd nanoparticles a Tb b F3 to obtain an aqueous suspension of these nanoparticles modified on the surface by PEG-phosphonate and said bifunctional ligand; add to this suspension rose Bengal in solution in an organic solvent, and react for 1 - 24 h, at a temperature of 25°C; and purify by dialysis the nanoparticles obtained, and if necessary lyophilize them.

[0024] The bifunctional ligand can in particular be aminomethylphosphonic acid.

[0025] The present invention also relates to a method for preparing nanoparticles containing PEG-silane as a biocompatibility ligand, as defined above, characterized in that it comprises the following steps: adding sodium silicate in aqueous solution to a suspension of Gd nanoparticles a Tb b F3 then heat to a temperature of 25 to 80°C for 1 to 24 h to obtain a suspension of Gd particles a Tb b F3 modified with sodium silicate; disperse these particles in a water / alcohol / photosensitizer(s) mixture, with successive additions of an ethanolic solution of tetraethyl orthosilicate (TEOS) being made to produce Gd particles a Tb bF3 coated with a layer of silica trapping the photosensitizer(s); modify the surface of the particles thus obtained by grafting PEG chains by adding an ethanolic solution of PEG-silane in a basic medium to obtain the desired nanoparticles; and purify the nanoparticles obtained by dialysis, and if necessary, freeze-dry them.

[0026] The present invention also relates to the nanoparticles defined above for their use in a method of imaging a tumor or of imaging a tumor followed by its treatment.

[0027] In particular, tumor imaging followed by tumor treatment may include the following steps: administering nanoparticles to a patient in need; placing the patient in an X-ray machine; subjecting the patient to a first dose of X-rays to perform tumor imaging; subjecting the patient to a second dose of X-rays, of higher intensity than the first dose, to perform tumor treatment; subjecting the patient again to the first dose of X-rays to perform tumor imaging.

[0028] Imaging performed after treatment allows, in particular, monitoring of the decrease in tumor size.

[0029] Nanoparticles can be injected as a suspension in a solvent at a concentration of 0.1 M – 5 M. The solvent can be chosen from water, physiological saline and a buffer solution such as a phosphate buffer.

[0030] Nanoparticles can be administered by intra-arterial injection, intravenous injection, intramuscular injection or subcutaneous injection; or in situ directly into the area to be imaged and treated; or by oral ingestion or cutaneous delivery.

[0031] The X-ray machine can be a spectral photon counting computed tomography (SPCCT) machine.

[0032] The first dose of X-rays can be 0.01Gy – 0.03Gy.

[0033] The second dose of X-rays can be 1 Gy – 4 Gy.

[0034] Another drug or immunomodulator may be injected at the same time as the nanoparticles.

[0035] The tumor may be a solid tumor, preferably chosen from the group consisting of glioblastoma, brain metastases, meningioma or primary tumors of cervical, rectal, lung, head and neck, prostate, colorectal, liver, pancreatic and breast cancers.

[0036] The tumor may also be a metastasis from primary cancers of melanoma, lung, breast or kidney.

[0037] The process of imaging a tumor may include the following steps: administering nanoparticles to a patient in need; placing the patient in an X-ray machine; subjecting the patient to a dose of X-rays to perform a first imaging of a tumor; after a determined time, subjecting the patient to a dose of X-rays to perform a second imaging of a tumor.

[0038] Nanoparticles can be injected as a suspension in a solvent at a concentration of 0.1 M – 5 M.

[0039] The solvent can be chosen from water, physiological saline, and a buffer solution such as a phosphate buffer.

[0040] Nanoparticles can be administered by intra-arterial injection, intravenous injection, intramuscular injection or subcutaneous injection; or in situ directly into the area to be imaged and treated; or by oral ingestion or cutaneous delivery.

[0041] The X-ray machine can be a spectral photon counting computed tomography (SPCCT) machine.

[0042] The X-ray dose can be 0.01 Gy – 0.03 Gy.

[0043] The present invention also relates to nanoparticles as defined above for their use in a method of imaging a tumor and producing one or more reactive oxygen species in said tumor, comprising the following steps: administering said nanoparticles to the patient; exposing the tumor to a first dose of X-rays in a range of 0.01 Gy – 0.03 Gy to generate a first image of a tumor; exposing the tumor to a second dose of X-rays in a range of 1 Gy – 4 Gy to generate the reactive oxygen species in said tumor.

[0044] The following examples illustrate the present invention without, however, limiting its scope.

[0045] In these examples, the following abbreviations have been used:

[0046] NP: Gd nanoparticles 0,90 Tb 0,10 F3

[0047] PEG-phosphonate:

[0048] with n = 19-20, Me = methyl, and M = H, methyl or ethyl

[0049] AMPA: aminomethylphosphonic acid

[0050] RB: Bengal rose

[0051] PEG-silane:

[0052] with p = 20-50, Me = methyl, Et = ethyl

[0053] TEOS: tetraethyl orthosilicate

[0054] BSA: Bovine serum albumin

[0055] NP@xPEG-phosphonate / y AMPA: NP nanoparticles modified on the surface by grafting PEG-phosphonate and AMPA in a molar ratio x / y, x+y = 100.

[0056] NP@xPEG-phosphonate / y AMPA@RB: NP@xPEG-phosphonate / y AMPA nanoparticles with RB grafted onto AMPA

[0057] DMSO: dimethyl sulfoxide

[0058] EDC: 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide

[0059] NP@silicate: silicate-functionalized NPs

[0060] NP@SiO2@RB: NP@silicate having reacted with RB

[0061] NP@SiO2@RB@PEG-silane: NP@SiO2@RB grafted with PEG-silane

[0062] NP@BSA: NPs modified on the surface by BSA

[0063] The following examples illustrate the present invention without, however, limiting its scope.

[0064] Example 1: Preparation of an aqueous suspension of NP nanocrystals

[0065] 3.64 g of GdCl3·6H2O (9.8 mmol) and 0.41 g of TbCl3·6H2O (1.1 mmol) were dissolved in 5 g of ethylene glycol. The resulting solution was added to a 100 mL Teflon insert.

[0066] In parallel, 875 µl of a 50% by mass aqueous solution of hydrofluoric acid (25 mmol) were added to a container containing 20g of pyrrolidinone.

[0067] The resulting solution was slowly added to the Teflon insert containing the salts and the container was rinsed with 45g of pyrrolidinone.

[0068] The mixture was then heated in an autoclave at 170°C for 1 hour and 30 minutes.

[0069] The product obtained was treated with 100 mL of acetone to precipitate the nanoparticles, which were then recovered by centrifugation.

[0070] The nanoparticles thus recovered were purified by cycles of centrifugation-redispersion in methanol, then redispersed in ultrapure water.

[0071] The mass fraction of the aqueous suspension is approximately 15% by mass of NP.

[0072] We obtained an aqueous suspension with 10% by mass of NP.

[0073] Examples 2 to 4: Obtaining NP@xPEG-phosphonate / yAMPA@RB General operating procedure

[0074] First step: Obtaining NP@xPEG-phosphonate / yAMPA

[0075] A mg of AMPA-HCl and B mg of PEG-phosphonate were introduced into 20 mL of water. To this mixture, 25 mL of the aqueous suspension obtained in Example 1 (at 1.2 x 10⁻³) was added dropwise. -2mol of Gd+Tb). This mixture was then heated to 80°C with stirring for 2 hours. The NPs mentioned in the title of this step were purified by dialysis.

[0076] Second step: Obtaining the NPs from the titles of these Examples 2 to 4

[0077] 50 mL of an aqueous NP suspension obtained in the first step was sonicated for 10 minutes. 5 mL of a RB (10 mg / mL) solution in DMSO was added to this suspension.

[0078] After a few minutes of stirring, 570 µL of EDC were added dropwise to the reaction mixture, which became cloudy. After stirring at room temperature for about ten minutes, the mixture became clear again.

[0079] The reaction mixture was left under stirring at room temperature for 24 hours.

[0080] The NPs obtained were then purified by dialysis until the dialysis waters remained colorless, then they were lyophilized and stored as a powdery pink solid.

[0081] In the following Table 1, we have indicated the parameters A and B (see first step) which led to the NPs of the title with indication of the x and y.

[0082] During the synthesis of NP@PEG, the molar proportions of ligands are such that there are 3 moles of lanthanide per ligand, or 0.3 ligand equivalents. When using a typical 50% PEG / 50% AMPA ratio, this means that 0.15 equivalents of PEG and 0.15 equivalents of AMPA will be introduced.

[0083] ExampleA (mg)B (mg)xy2549(3.12x10 -3 mol)137(7.8x10 -4 mol)20803343(1.95x10 -3 mol)195(1.11x10 -3 mol)50504137(7.8x10 -4 mol)312(1.78x10 -3 mol)8020

[0084] The size of the nanoparticles in Example 3 was measured in suspension in water by dynamic light scattering. This size is 30 nm + / - 3 nm.

[0085] The zeta potential of these nanoparticles was measured at +27 mV.

[0086] This is a transmission electron microscope view of the nanoparticles in Example 1.

[0087] Example 5: Preparation of NP@SiO2@RB@PEG-silane

[0088] First step: Obtaining NP@silicate

[0089] 50g of an aqueous suspension obtained in Example 1 (at 1.39x10 -3 mol of Gd+Tb) were placed under ultrasound.

[0090] Under ultrasound, 20.8 mL of an aqueous sodium silicate solution with 3% by mass of SiO2 were added (1.35x10 -2 mol of Si).

[0091] The mixture became viscous white, then as sonication progressed, it became a stable colloidal suspension with a whitish tint.

[0092] The mixture was then heated for 1 hour at 80°C, and subsequently purified by dialysis. 100 µL of ammonia at 30% by mass in water was then added to maintain the stability of the suspension over time.

[0093] Second step: Obtaining NP@SiO2@RB

[0094] 407.2 mg of RB were dissolved in a mixture containing 8.4 mL of water, 3.15 mL of absolute ethanol and 114 µL of ammonia at 30% by mass in water.

[0095] After sonication, 14.1 mL of an aqueous suspension of nanoparticles obtained in the first step (71 mg / mL) were added to the mixture.

[0096] A solution of TEOS in absolute ethanol was prepared by adding 841.6 µL of TEOS to 1248 µL of absolute ethanol. Every hour, for 4 hours, 521.6 µL of this solution were added to the reaction mixture.

[0097] The NPs obtained were then purified by dialysis for 48 hours, with a pink color appearing in the dialysis waters.

[0098] Third step: Obtaining NP@SiO2@RB@PEG-silane

[0099] To 20.8 mL of the suspension obtained in the second step (25 mg / mL of NP), 150 µL of 30% ammonia in water was added. Then, 1.52 mL of an ethanolic PEG-silane solution was added dropwise under vigorous stirring.

[0100] The medium was left under agitation for 48 hours at room temperature, protected from light.

[0101] The final suspension was purified by dialysis until the dialysis waters were no longer colored. The NPs were then lyophilized and stored as a powdered solid, protected from light.

[0102] The size of the NP@SiO2@RB@PEG-silane nanoparticles obtained was measured in suspension in water by dynamic light scattering. This size is 50 nm + / - 3 nm.

[0103] The zeta potential of these nanoparticles was measured at -31 mV.

[0104] This is a transmission electron microscope view of the nanoparticles obtained in this example.

[0105] Example 6: Preparing NP@BSA

[0106] An ethanolic suspension of NP was obtained at 0.5 mg.ml -1 following the protocol of Example 1 with the difference that the NPs were redispersed in a 50% by volume ethanolic solution.

[0107] 5 g of an aqueous saline solution of BSA were prepared by mixing 2.9 mg of NaCl and 100 mg of BSA. A sodium hydroxide solution (0.1 M) was added until a pH of 8.57 was obtained, checked with a pH meter.

[0108] 2 mL of the ethanolic NP solution was added to 500 μL of this BSA solution using a peristaltic pump at a flow rate of approximately 1.5 mL.min-1. A colloidal suspension was obtained.

[0109] 2.4 μL of an aqueous glutaraldehyde solution (8% in

[0110] mass) were added to the reaction medium which is vigorously stirred for 24 hours in the dark.

[0111] The NP@BSA nanoparticles were recovered by centrifugation at 4°C, then washed by cycles of centrifugation-redispersion in water at 4°C.

[0112] Example 7: X-ray irradiation

[0113] The scintillation of RB-functionalized NP suspensions was studied by X-ray excitation of a micro-computed tomography (micro-CT) system.

[0114] Lamontre presents the results obtained for an aqueous suspension of 0.1 mol / L of Gd 0,9 Tb 0,1 F3 (column A), and an aqueous suspension at 0.1 mol / L of nanoparticles from Example 2 (column B), Example 3 (column C) and Example 4 (column D).

[0115] The luminescence of Tb 3+No X-ray radiation is detected for the aqueous suspensions in Examples 2 to 4. This confirms efficient energy transfer between the Tb 3+ and the RB present on the surface.

[0116] Lamontre presents the results obtained for an aqueous suspension of 0.1 mol / L of Gd 0,9 Tb 0,1 F3 (column A), and an aqueous suspension at 0.1 mol / L of nanoparticles from Example 5 (column B).

[0117] The nanoparticle suspension in Example 5 still exhibits scintillation. However, the intensity of this scintillation is significantly lower than that of the Gd nanoparticles. 0,9 Tb 0,1 F3, which indicates an energy transfer between the Tb 3+ and the RB.

[0118] Example 8: Stability of nanoparticles

[0119] A chemical stability test (solubilization) was performed in water for 3 days at 37°C to compare the stability of the nanoparticles from Example 1 with the nanoparticles described by Zhang et al. After removal of the remaining nanoparticles, the liquid media were analyzed by ICP to quantify the main rare earth elements. The resulting concentrations are shown.

[0120] Compared to the terbium-doped mixed gadolinium-sodium fluoride nanoparticles described by Zhang et al., the terbium-doped gadolinium fluoride nanoparticles are extremely stable in dilute media.

[0121] The nanoparticles in Examples 2 to 4 have a hydrodynamic diameter in the range of 20 to 25 nm, and the nanoparticles in Example 5 have a hydrodynamic diameter of 50 nm, as measured by dynamic light scattering. The particles described by Zhang et al. have a hydrodynamic diameter well over 100 nm.

[0122] Compared to the particles described by Zhang et al., the nanoparticles according to the invention exhibit a smaller size and much better dispersibility.

[0123] Example 9: Colloidal stability

[0124] We measured by dynamic light scattering the size of the particles according to Example 4 in the case where the particles are suspended in water or in physiological serum at different points in time over a period of 24 hours.

[0125] The results are presented with the suspension in water represented by grey circles and the suspension in physiological serum represented by white circles.

[0126] The size of the nanoparticles does not increase over time, which means that the nanoparticles do not aggregate, which is a characteristic of the colloidal stability of nanoparticles.

[0127] Example 10: X-ray doses used

[0128] The nanoparticles according to the invention are capable of generating reactive oxidative species (ROS) under X-ray radiation.

[0129] The generation efficiency of these species is measured by the decomposition of 1,3-diphenylisobenzofuran (DPBF). The protocol is as follows: 21 μg of DPBF are solubilized with a suspension of 4.7 mg of nanoparticles from each of Examples 2 to 5 in 2 mL of a suitable solvent and placed in a 10 mm x 10 mm quartz cuvette. The degradation of DPBF is measured by absorbance. The results are presented on the [page number].

[0130] Upon X-ray irradiation, the nanoparticles in Example 5 were able to decompose all of the DPBF (21 μg) after 40 seconds. Zhang et al. presented nanoparticles requiring an irradiation time of over one minute for a similar result in the best-case scenario. Similarly, after 40 seconds of irradiation, the nanoparticles described by Zhang et al. degraded barely 10 μg of DPBF.

[0131] Example 11: Infrared Spectra

[0132] Lamontre shows the combined infrared spectrum of nanoparticles according to Example 5 (light grey), of NP@SiO2@PEG-silane nanoparticles obtained as in Example 5 with omission of the second step (grey) and of rose Bengal (darkest spectrum at the bottom).

[0133] The infrared spectra of the nanoparticles both show the characteristic signals of PEG and silica in the 1100 cm⁻¹ region. -1 and 2873 cm -1 In both cases, these signals show that a SiO2@PEG shell is indeed present around the nanoparticles. The infrared spectrum of the nanoparticles containing rose bengal differs from that of the nanoparticles without rose bengal, notably by the presence of a band at 1592 cm⁻¹ -1 This band corresponds to the vibration due to the elongation of the C=O bond present on the tricyclic structure of the rose Bengal flower.

[0134] Lamontre shows the infrared spectra of NP@80PEG-phosphonate / 20AMPA particles (denoted Gd)0,90 Tb 0,10 F3@80P20A, in grey) and nanoparticles according to Example 4 (noted Gd 0,90 Tb 0,10 F3@80P20A@RB, in black).

[0135] Comparison of the infrared spectra for nanoparticles before (grey) and after (black) modification by RB shows a band that differs at 1545 cm⁻¹ -1 (marked *). This can be attributed to the stretching vibration of the C=O bond in the amide. This band can be compared to that at 1550 cm⁻¹ -1 appearing on the infrared spectrum of RB shown in the Figure, which corresponds to the stretching vibration of the C=O bond of the carboxylic acid. The decrease in the wavenumber of this vibration is consistent with the transition from a carboxylic acid function to an amide function, thus a strong and chemically stable bond during the grafting of Rose Bengal onto the nanoparticle.

[0136] Example 12: Obtaining images and tracking the distribution of nanoparticles over time

[0137] A suspension of Example 3 nanoparticles at a concentration of 1 M was injected into a physiological saline solvent. Images were acquired by SPCCT with a dose of 100 mAs and 120 kV.

[0138] Lamontre (A) the diagram illustrating the axial plane of the acquisitions made by the SPCCT on the mice (BC) This figure illustrates two distinct biodistribution profiles: a predominantly intra-tumoral distribution (B) and a predominantly peritumoral diffusion (C).

[0139] It is possible to track the distribution of nanoparticles over time after their injection and to quantify the amount of nanoparticles present using spectral scanning and K-edge imaging.

[0140] This is a curve of the distribution as a function of time of nanoparticles from Example 3, after injection into the tumor.

[0141] Example 13: Control of the production of reactive oxygen species

[0142] We studied the control of the generation of reactive oxygen species by different nanoparticles according to the invention and subjected to different doses of X-rays by a spectral scanner (1.2 Gy and 300 mGy – theranostic nanoparticles according to Examples 2, 3, 4 and 5 and non-theranostic T nanoparticles).

[0143] Lamontre the results obtained.

[0144] Controlling the X-ray dose delivered by the spectral scanner and controlling the dose of injected theranostic nanoparticles according to the invention allows for the choice of: imaging the area to be treated without triggering treatment, or treating the area of ​​interest.

[0145] Example 14: Therapeutic effect on a murine model of breast cancer.

[0146] Two groups of mice were tested: four mice received X-rays with control nanoparticles (GdTbF3@SiO2), and five mice received X-rays with nanoparticles according to Example 5 (GdTbF3@SiO2+RB+PEG). Both groups aimed to evaluate the association between nanoparticles and X-rays.

[0147] The tumors received an injection of nanoparticles (1 M, 50 µL, in physiological saline), followed 24 hours later by a single dose of 1800 mGy of X-ray. Tumor growth was monitored throughout the study, and an ex vivo analysis was performed to evaluate the treatment efficacy.

[0148] Tumor growth retardation was assessed using a measure widely used to evaluate the effectiveness of cancer treatments and detailed below.

[0149] To assess tumor growth retardation (TGR) between treatment groups, the following steps were followed:

[0150] 1. Definition of the evaluation criterion:

[0151] A specific tumor volume (e.g., 4 times the initial size) was chosen as the comparison target.

[0152] 2. Measurement of tumor growth:

[0153] Tumor volumes were monitored regularly (tumor volume / caliper measurement) and the time taken for each tumor to reach the target volume was recorded for the treated and control groups.

[0154] 3. Calculation of the DCT:

[0155] The average time to reach the target volume in the control group was subtracted from that of the treatment group.

[0156] 4. Statistical analysis:

[0157] Statistical tests were applied to determine if the delay was significant.

[0158] This method allows for a direct comparison of treatment effectiveness based on tumor growth retardation.

[0159] Experience shows a trend towards increased efficacy in the group treated with the nanoparticles of Example 5 (GdTbF3@SiO2+RB+PEG) compared to the control group (GdTbF3@SiO2), with post-treatment days extending longer.

[0160] The results are presented on the.

[0161] For the same type of sequence on the spectral scanner, a negative control (non-theranostic nanoparticles) does not prevent tumor growth. Theranostic nanoparticles limit tumor growth.

[0162] The present invention relates to the following embodiments:

[0163] [Embodyment 1] – Gd nanoparticles a Tb b F3, where a = 0.50 to 0.95, b = 0.05 to 0.50 and a+b = 1, surface modified by at least one biocompatibility ligand and by at least one photosensitizer absorbing in the wavelength band of 520 to 560 nm under excitation of the nanoparticles by X-rays.

[0164] [Embodyment 2] – Nanoparticles according to embodiment 1, characterized in that they have a size of 3 - 60 nm, in particular 10 - 50 nm, as measured in suspension in water by dynamic light scattering.

[0165] [Embodyment 3] – Nanoparticles according to one of embodiments 1 and 2, characterized by the fact that a = 0.80 to 0.95, b = 0.05 to 0.20, in particular a = 0.90 and b = 0.10.

[0166] [Embodyment 4] – Nanoparticles according to one of embodiments 1 to 3, characterized in that a biocompatibility ligand is selected from: polymers whose chain is selected from: , with n = 10 to 80, in particular 19 or 20; , with p = 6 to 50, , with q = 5 to 25, in particular 25, and R representing hydrogen or a C1-C3 alkyl radical, such as methyl, ethyl, or propyl, , with r = 8 to 60,

[0167] and which carries a functionality allowing its direct or indirect grafting onto Gd nanoparticles a Tb b F3; bovine serum albumin; sodium triphosphate (TPP) formula .

[0168] [Embodyment 5] – Nanoparticles according to any one of embodiments 1 to 4, characterized in that the photosensitizer is rose bengal.

[0169] [Embodyment 6] – Nanoparticles according to any one of embodiments 1 to 4, characterized in that the photosensitizer is merocyanine 540 which absorbs in the green.

[0170] [Embodyment 7] – Nanoparticles according to one of embodiments 4 and 5, characterized in that they consist of Gd nanoparticles a Tb b F3 modified on the surface by grafting a PEG-phosphonate as a biocompatibility ligand of formula: in which m = 10 to 80, in particular 19 or 20, and by grafting a bifunctional ligand of formula:

[0171] in which x = 1 to 10, in particular 1 to 5, the rose bengal being grafted by its reaction with an available function, such as an amine function, of the bifunctional ligand.

[0172] [Embodyment 8] – Nanoparticles according to embodiment 7, characterized in that the molar ratio of PEG-phosphonate to bifunctional ligand is 20:80 to 90:10, in particular 50:50 to 80:20.

[0173] [Embodyment 9] – Nanoparticles according to any one of embodiments 1 to 6, characterized in that they consist of Gd nanoparticles a Tb bF3 surrounded by a silica layer in which the photosensitizer(s) is / are trapped, then grafted, onto said silica layer, by a PEG-silane as a biocompatibility ligand, the PEG-silane being represented by the formula: in which u = 20 to 50, in particular 45.

[0174] [Embodyment 10] – A process for preparing nanoparticles as defined in either embodiment 7 or 8, characterized in that it comprises the following steps: heating for 1–24 hours, at a temperature of 25 to 80°C, an aqueous mixture of PEG-phosphonate and a bifunctional ligand of formula with x = 1 to 10, specifically 1 to 5, and add Gd nanoparticles a Tb bF3 to obtain an aqueous suspension of these nanoparticles modified on the surface by PEG-phosphonate and said bifunctional ligand; add to this suspension rose bengal in solution in an organic solvent, and react for 1 - 24 h, at a temperature of 25°C; and purify by dialysis the nanoparticles obtained, and if necessary lyophilize them.

[0175] [Embodyment 11] – A process for preparing nanoparticles as defined in embodiment 9, characterized in that it comprises the following steps: adding sodium silicate in aqueous solution to a suspension of Gd nanoparticles a Tb b F3 then heat to a temperature of 25 to 80°C for 1 to 24 hours to obtain a suspension of Gd particles a Tb bF3 modified with sodium silicate; disperse these particles in a water / alcohol / photosensitizer(s) mixture, with successive additions of an ethanolic solution of tetraethyl orthosilicate (TEOS) being made to produce Gd particles a Tb b F3 coated with a layer of silica trapping the photosensitizer(s); modify the surface of the particles thus obtained by grafting PEG chains by adding an ethanolic solution of PEG-silane in a basic medium to obtain the desired nanoparticles; and purify the nanoparticles obtained by dialysis, and if necessary, freeze-dry them.

[0176] [Embodyment 12] – Nanoparticles according to any one of embodiments 1 to 8 for their use in a tumor imaging process or tumor imaging followed by tumor treatment.

[0177] [Embodyment 13] – Nanoparticles for their use according to embodiment 12, characterized in that the imaging of a tumor followed by the treatment thereof comprises the following steps: administering nanoparticles to a patient in need; placing the patient in an X-ray machine; subjecting the patient to a first dose of X-rays, to perform imaging of a tumor; subjecting the patient to a second dose of X-rays, of greater intensity than the first dose, to perform treatment of the tumor; subjecting the patient again to the first dose of X-rays to perform imaging of the tumor.

[0178] [Embodyment 14] – Nanoparticles for their use according to embodiment 13, characterized in that the nanoparticles are injected as a suspension in a solvent at a concentration of 0.1 mol / L - 5 mol / L.

[0179] [Embodyment 15] – Nanoparticles for their use according to embodiment 14, characterized in that the solvent is chosen from water, physiological serum and a buffer solution such as a phosphate buffer.

[0180] [Embodyment 16] – Nanoparticles for use according to any one of embodiments 13 to 15, characterized in that the nanoparticles are administered by intra-arterial injection, intravenous injection, intramuscular injection or subcutaneous injection; or in situ directly into the area to be imaged and treated; or by oral ingestion or cutaneous delivery.

[0181] [Embodyment 17] – Nanoparticles for their use according to any one of embodiments 13 to 16, characterized by the fact that the X-ray machine is a spectral photon counting computed tomography (SPCCT) machine.

[0182] [Embodyment 18] – Nanoparticles for their use according to any one of embodiments 13 to 17, characterized by the fact that the first dose of X-rays is 0.01 Gy - 0.03 Gy.

[0183] [Embodyment 19] – Nanoparticles for their use according to one of embodiments 13 to 18, characterized by the fact that the second dose of X-rays is 1 Gy - 4 Gy.

[0184] [Embodyment 20] – Nanoparticles for their use according to any one of embodiments 13 to 19, characterized in that another drug or immunomodulator is injected at the same time as the nanoparticles.

[0185] [Embodyment 21] – Nanoparticles for use according to any one of embodiments 12 to 20, characterized by the fact that the tumor is a solid tumor, preferably selected from the group consisting of glioblastoma, brain metastases, meningioma or primary tumors of cervical, rectal, lung, head and neck, prostate, colorectal, liver, pancreatic and breast cancers.

[0186] [Embodyment 22] – Nanoparticles for use according to any one of embodiments 12 to 20, characterized by the fact that the tumor is a metastasis from primary melanoma, lung, breast or kidney cancers.

[0187] [Embodyment 23] – Nanoparticles for their use according to embodiment 12, characterized in that the method of imaging a tumor comprises the following steps: administering nanoparticles to a patient in need; placing the patient in an X-ray machine; subjecting the patient to a dose of X-rays, to perform a first imaging of a tumor; after a determined time, subjecting the patient to a dose of X-rays, to perform a second imaging of a tumor.

[0188] [Embodyment 24] – Nanoparticles for their use according to embodiment 23, characterized in that the nanoparticles are injected as a suspension in a solvent at a concentration of 0.1 mol / L - 5 mol / L.

[0189] [Embodyment 25] – Nanoparticles for their use according to embodiment 24, characterized in that the solvent is chosen from water, physiological serum and a buffer solution such as a phosphate buffer.

[0190] [Embodyment 26] – Nanoparticles for use according to any one of embodiments 23 to 25, characterized in that the nanoparticles are administered by intra-arterial injection, intravenous injection, intramuscular injection or subcutaneous injection; or in situ directly into the area to be imaged and treated; or by oral ingestion or cutaneous delivery.

[0191] [Embodyment 27] – Nanoparticles for their use according to any one of embodiments 23 to 26, characterized by the fact that the X-ray machine is a spectral photon counting computed tomography (SPCCT) machine.

[0192] [Embodyment 28] – Nanoparticles for their use according to one of embodiments 23 to 27, characterized by the fact that the X-ray dose is 0.01 Gy- 0.03 Gy.

[0193] [Embodyment 29] – A method for imaging a tumor followed by its treatment, characterized in that the method comprises the following steps: administering Gd nanoparticles a Tb bF3, where a = 0.50 to 0.95, b = 0.05 to 0.50 and a+b = 1, surface modified by at least one biocompatibility ligand and by at least one photosensitizer absorbing in the wavelength band of 520 to 560 nm under excitation of the nanoparticles by X-rays, to a patient in need; place the patient in an X-ray machine; subject the patient to a first dose of X-rays, to perform imaging of a tumor; subject the patient to a second dose of X-rays, of greater intensity than the first dose, to perform treatment of the tumor; subject the patient again to the first dose of X-rays to perform imaging of the tumor.

[0194] [Embodyment 30] – Method according to embodiment 29, characterized in that the nanoparticles have a size of 3 - 60 nm, in particular 10 - 50 nm, as measured in suspension in water by dynamic light scattering.

[0195] [Embodyment 31] – A method according to one of embodiments 29 and 30, characterized in that a = 0.80 to 0.95, b = 0.05 to 0.20, in particular a = 0.90 and b = 0.10.

[0196] [Embodyment 32] – A process according to any one of embodiments 29 to 31, characterized in that a biocompatibility ligand is selected from: polymers whose chain is selected from: , with n = 10 to 80, in particular 19 or 20; , with p = 6 to 50, , with q = 5 to 25, in particular 25, and R representing hydrogen or a C1-C3 alkyl radical, such as methyl, ethyl, or propyl, , with r = 8 to 60,

[0197] and which carries a functionality allowing its direct or indirect grafting onto Gd nanoparticles a Tb b F3; bovine serum albumin; sodium triphosphate (TPP) formula .

[0198] [Embodyment 33] – A process according to any one of embodiments 29 to 32, characterized in that the photosensitizer is rose bengal.

[0199] [Embodyment 34] – A process according to any one of embodiments 29 to 32, characterized in that the photosensitizer is merocyanine 540 which absorbs in the green.

[0200] [Embodyment 35] – A method according to one of embodiments 32 and 33, characterized in that they consist of Gd nanoparticles a Tb b F3 modified on the surface by grafting a PEG-phosphonate as a biocompatibility ligand of formula: in which m = 10 to 80, in particular 19 or 20, and by grafting a bifunctional ligand of formula:

[0201] in which x = 1 to 10 in particular 1 to 5, the rose bengal being grafted by its reaction with an available function, such as an amine function, of the bifunctional ligand.

[0202] [Embodyment 36] – Process according to embodiment 35, characterized in that the molar ratio of PEG-phosphonate to bifunctional ligand is 20:80 to 90:10, in particular 50:50 to 80:20.

[0203] [Embodyment 37] – A method according to any one of embodiments 29 to 34, characterized in that they consist of Gd nanoparticles a Tb b F3 surrounded by a silica layer in which the photosensitizer(s) is / are trapped, then grafted, onto said silica layer, by a PEG-silane as a biocompatibility ligand, the PEG-silane being represented by the formula: in which u = 20 to 50, in particular 45.

[0204] [Embodyment 38] – A method according to any one of embodiments 29 to 37, characterized in that the nanoparticles are injected as a suspension in a solvent at a concentration of 0.1 mol / L - 5 mol / L.

[0205] [Embodyment 39] – Process according to embodiment 38, characterized in that the solvent is chosen from water, physiological saline and a buffer solution such as a phosphate buffer.

[0206] [Embodyment 40] – A method according to any one of embodiments 29 to 39, characterized in that the nanoparticles are administered by intra-arterial injection, intravenous injection, intramuscular injection or subcutaneous injection; or in situ directly into the area to be imaged and treated; or by oral ingestion or cutaneous delivery.

[0207] [Embodyment 41] – Method according to any one of embodiments 29 to 40, characterized in that the X-ray machine is a spectral photon counting computed tomography (SPCCT) machine.

[0208] [Embodyment 42] – A method according to any one of embodiments 29 to 41, characterized in that the first dose of X-rays is 0.01 Gy - 0.03 Gy.

[0209] [Embodyment 43] – A method according to any one of embodiments 29 to 42, characterized in that the second dose of X-rays is 1 Gy - 4 Gy.

[0210] [Embodyment 44] – A method according to any one of embodiments 29 to 43, characterized in that another drug or immunomodulator is injected at the same time as the nanoparticles.

[0211] [Embodyment 45] – A method according to any one of embodiments 29 to 44, characterized in that the tumor is a solid tumor, preferably selected from the group consisting of glioblastoma, brain metastases, meningioma or primary tumors of cervical, rectal, lung, head and neck, prostate, colorectal, liver, pancreatic and breast cancers.

[0212] [Embodyment 46] – A method according to any one of embodiments 29 to 45, characterized in that the tumor is a metastasis from primary melanoma, lung, breast or kidney cancers.

[0213] [Embodyment 47] – A tumor imaging method characterized in that it comprises the following steps: administering Gd nanoparticles a Tb bF3, where a = 0.50 to 0.95, b = 0.05 to 0.50 and a+b = 1, surface modified by at least one biocompatibility ligand and by at least one photosensitizer absorbing in the wavelength band of 520 to 560 nm under excitation of the nanoparticles by X-rays, to a patient in need; place the patient in an X-ray machine; subject the patient to a dose of X-rays, to perform a first imaging of a tumor; after a determined time, subject the patient to a dose of X-rays, to perform a second imaging of a tumor.

[0214] [Embodyment 48] – Method according to embodiment 47, characterized in that the nanoparticles have a size of 3 - 60 nm, in particular 10 - 50 nm, as measured in suspension in water by dynamic light scattering.

[0215] [Embodyment 49] – A method according to one of embodiments 47 and 48, characterized in that a = 0.80 to 0.95, b = 0.05 to 0.20, in particular a = 0.90 and b = 0.10.

[0216] [Embodyment 50] – A method according to any one of embodiments 47 to 49, characterized in that a biocompatibility ligand is selected from: polymers whose chain is selected from: , with n = 10 to 80, in particular 19 or 20; , with p = 6 to 50, , with q = 5 to 25, in particular 25, and R representing hydrogen or a C1-C3 alkyl radical, such as methyl, ethyl, or propyl, , with r = 8 to 60,

[0217] and which carries a functionality allowing its direct or indirect grafting onto Gd nanoparticles a Tb b F3; bovine serum albumin; sodium triphosphate (TPP) formula .

[0218] [Embodyment 51] – A process according to any one of embodiments 47 to 50, characterized in that the photosensitizer is rose bengal.

[0219] [Embodyment 52] – A process according to any one of embodiments 47 to 50, characterized in that the photosensitizer is merocyanine 540 which absorbs in the green.

[0220] [Embodyment 53] – A method according to one of embodiments 50 and 51, characterized in that they consist of Gd nanoparticles a Tb b F3 modified on the surface by grafting a PEG-phosphonate as a biocompatibility ligand of formula: in which m = 10 to 80, in particular 19 or 20, and by grafting a bifunctional ligand of formula:

[0221] in which x = 1 to 10 in particular 1 to 5, the rose bengal being grafted by its reaction with an available function, such as an amine function, of the bifunctional ligand.

[0222] [Embodyment 54] – Process according to embodiment 53, characterized in that the molar ratio of PEG-phosphonate to bifunctional ligand is 20:80 to 90:10, in particular 50:50 to 80:20.

[0223] [Embodyment 55] – A method according to any one of embodiments 47 to 52, characterized in that they consist of Gd nanoparticles a Tb b F3 surrounded by a silica layer in which the photosensitizer(s) is / are trapped, then grafted, onto said silica layer, by a PEG-silane as a biocompatibility ligand, the PEG-silane being represented by the formula: in which u = 20 to 50, in particular 45.

[0224] [Embodyment 56] – A process according to any one of embodiments 47 to 55, characterized in that the nanoparticles are injected as a suspension in a solvent at a concentration of 0.1 mol / L - 5 mol / L.

[0225] [Embodyment 57] – Process according to embodiment 56, characterized in that the solvent is chosen from water, physiological saline and a buffer solution such as a phosphate buffer.

[0226] [Embodyment 58] – A method according to any one of embodiments 47 to 57, characterized in that the nanoparticles are administered by intra-arterial injection, intravenous injection, intramuscular injection or subcutaneous injection; or in situ directly into the area to be imaged and treated; or by oral ingestion or cutaneous delivery.

[0227] [Embodyment 59] – Method according to any one of embodiments 47 to 58, characterized in that the X-ray machine is a spectral photon counting computed tomography (SPCCT) machine.

[0228] [Embodyment 60] – A method according to any one of embodiments 47 to 59, characterized in that the X-ray dose is 0.01 Gy - 0.03 Gy.

[0229] [Embodying 61] – A method for imaging a tumor and producing one or more reactive oxygen species in said tumor, characterized in that it comprises the following steps: administering Gd nanoparticles to the patient a Tb bF3, where a = 0.50 to 0.95, b = 0.05 to 0.50 and a+b = 1, surface modified by at least one biocompatibility ligand and by at least one photosensitizer absorbing in the wavelength band of 520 to 560 nm under excitation of the nanoparticles by X-rays; expose the tumor to a first dose of X-rays in a range of 0.01 Gy – 0.03 Gy to generate a first image of a tumor; expose the tumor to a second dose of X-rays in a range of 1 Gy – 4 Gy to generate the reactive oxygen species in said tumor.

[0230] [Embodyment 62] – Method according to embodiment 61, characterized in that the nanoparticles have a size of 3 - 60 nm, in particular 10 - 50 nm, as measured in suspension in water by dynamic light scattering.

[0231] [Embodyment 63] – A method according to one of embodiments 61 and 62, characterized in that a = 0.80 to 0.95, b = 0.05 to 0.20, in particular a = 0.90 and b = 0.10.

[0232] [Embodyment 64] – A method according to any one of embodiments 61 to 63, characterized in that a biocompatibility ligand is selected from: polymers whose chain is selected from: , with n = 10 to 80, in particular 19 or 20; , with p = 6 to 50, , with q = 5 to 25, in particular 25, and R representing hydrogen or a C1-C3 alkyl radical, such as methyl, ethyl, or propyl, , with r = 8 to 60,

[0233] and which carries a functionality allowing its direct or indirect grafting onto Gd nanoparticles a Tb b F3; bovine serum albumin; sodium triphosphate (TPP) formula .

[0234] [Embodyment 65] – A process according to any one of embodiments 61 to 64, characterized in that the photosensitizer is rose bengal.

[0235] [Embodyment 66] – A process according to any one of embodiments 61 to 65, characterized in that the photosensitizer is merocyanine 540 which absorbs in the green.

[0236] [Embodyment 67] – A method according to one of embodiments 64 and 65, characterized in that they consist of Gd nanoparticles a Tb b F3 modified on the surface by grafting a PEG-phosphonate as a biocompatibility ligand of formula: in which m = 10 to 80, in particular 19 or 20, and by grafting a bifunctional ligand of formula:

[0237] in which x = 1 to 10 in particular 1 to 5, the rose bengal being grafted by its reaction with an available function, such as an amine function, of the bifunctional ligand.

[0238] [Embodyment 68] – Process according to embodiment 67, characterized in that the molar ratio of PEG-phosphonate to bifunctional ligand is 20:80 to 90:10, in particular 50:50 to 80:20.

[0239] [Embodyment 69] – A method according to any one of embodiments 61 to 66, characterized in that they consist of Gd nanoparticles a Tb b F3 surrounded by a silica layer in which the photosensitizer(s) is / are trapped, then grafted, onto said silica layer, by a PEG-silane as a biocompatibility ligand, the PEG-silane being represented by the formula: in which u = 20 to 50, in particular 45.

[0240] [Embodyment 70] – A method according to any one of embodiments 61 to 69, characterized in that the nanoparticles are injected as a suspension in a solvent at a concentration of 0.1 mol / L - 5 mol / L.

[0241] [Embodyment 71] – Process according to embodiment 70, characterized in that the solvent is chosen from water, physiological saline and a buffer solution such as a phosphate buffer.

[0242] [Embodyment 72] – A method according to any one of embodiments 61 to 71, characterized in that the nanoparticles are administered by intra-arterial injection, intravenous injection, intramuscular injection or subcutaneous injection; or in situ directly into the area to be imaged and treated; or by oral ingestion or cutaneous delivery.

[0243] [Embodyment 73] – Method according to any one of embodiments 61 to 72, characterized in that the X-ray machine is a spectral photon counting computed tomography (SPCCT) machine.

[0244] [Embodyment 74] – A method according to any one of embodiments 61 to 73, characterized in that another drug or immunomodulator is injected at the same time as the nanoparticles.

[0245] [Embodyment 75] – A method according to any one of embodiments 61 to 74, characterized in that the tumor is a solid tumor, preferably selected from the group consisting of glioblastoma, brain metastases, meningioma or primary tumors of cervical, rectal, lung, head and neck, prostate, colorectal, liver, pancreatic and breast cancers.

[0246] [Embodyment 76] – A method according to any one of embodiments 61 to 75, characterized in that the tumor is a metastasis from primary melanoma, lung, breast or kidney cancers.

Claims

– Gd nanoparticles a Tb b F3, where a = 0.50 to 0.95, b = 0.05 to 0.50 and a+b = 1, surface modified by at least one biocompatibility ligand and by at least one photosensitizer absorbing in the wavelength band of 520 to 560 nm under excitation of the nanoparticles by X-rays. – Nanoparticles according to claim 1, characterized in that they have a size of 3 - 60 nm, in particular 10 - 50 nm, as measured in suspension in water by dynamic light scattering. – Nanoparticles according to any one of claims 1 and 2, characterized by the fact that a = 0.80 to 0.95, b = 0.05 to 0.20, in particular a = 0.90 and b = 0.

10. – Nanoparticles according to any one of claims 1 to 3, characterized in that a biocompatibility ligand is selected from: polymers whose chain is selected from: , with n = 10 to 80, in particular 19 or 20; , with p = 6 to 50, , with q = 5 to 25, in particular 25, and R representing hydrogen or a C1-C3 alkyl radical, such as methyl, ethyl, or propyl, , with r = 8 to 60, and which carries a functionality allowing its direct or indirect grafting onto Gd nanoparticles a Tb b F3; bovine serum albumin; sodium triphosphate (TPP) formula . – Nanoparticles according to any one of claims 1 to 4, characterized in that the photosensitizer is rose bengal. – Nanoparticles according to any one of claims 1 to 4, characterized in that the photosensitizer is merocyanine 540 which absorbs in the green. – Nanoparticles according to any one of claims 4 and 5, characterized in that they consist of Gd nanoparticles a Tb bF3 modified on the surface by grafting a PEG-phosphonate as a biocompatibility ligand of formula: in which m = 10 to 80, in particular 19 or 20, and by grafting a bifunctional ligand of formula: in which x = 1 to 10, in particular 1 to 5, the rose bengal being grafted by its reaction with an available function, such as an amine function, of the bifunctional ligand. – Nanoparticles according to claim 7, characterized in that the molar ratio of PEG-phosphonate to AMPA is 20:80 to 90:10, in particular 50:50 to 80:

20. – Nanoparticles according to any one of claims 1 to 6, characterized in that they consist of Gd nanoparticles a Tb bF3 surrounded by a silica layer in which the photosensitizer(s) is / are trapped, then grafted, onto said silica layer, by a PEG-silane as a biocompatibility ligand, the PEG-silane being represented by the formula: in which u = 20 to 50, in particular 45. – A process for preparing nanoparticles as defined in any one of claims 7 and 8, characterized in that it comprises the following steps: heating for 1-24 hours, at a temperature of 25 to 80°C, a mixture in aqueous medium of PEG-phosphonate and a bifunctional ligand of formula with x = 1 to 10, specifically 1 to 5, and add Gd nanoparticles a Tb bF3 to obtain an aqueous suspension of these nanoparticles modified on the surface by PEG-phosphonate and said bifunctional ligand; add to this suspension rose bengal in solution in an organic solvent, and react for 1 - 24 h, at a temperature of 25°C; and purify by dialysis the nanoparticles obtained, and if necessary lyophilize them. – A method for preparing nanoparticles as defined in claim 9, characterized in that it comprises the following steps: adding sodium silicate in aqueous solution to a suspension of Gd nanoparticles a Tb b F3 then heat to a temperature of 25 to 80°C for 1 to 24 hours to obtain a suspension of Gd particles a Tb bF3 modified with sodium silicate; disperse these particles in a water / alcohol / photosensitizer(s) mixture, with successive additions of an ethanolic solution of tetraethyl orthosilicate (TEOS) being made to produce Gd particles a Tb b F3 coated with a layer of silica trapping the photosensitizer(s); modify the surface of the particles thus obtained by grafting PEG chains by adding an ethanolic solution of PEG-silane in a basic medium to obtain the desired nanoparticles; and purify the nanoparticles obtained by dialysis, and if necessary, freeze-dry them. – Nanoparticles according to any one of claims 1 to 8 for their use in a method of imaging a tumor or of imaging a tumor followed by treatment thereof. – Nanoparticles for their use according to claim 12, characterized in that the imaging of a tumor followed by the treatment thereof comprises the following steps: administering nanoparticles to a patient in need; placing the patient in an X-ray machine; subjecting the patient to a first dose of X-rays, to perform imaging of a tumor; subjecting the patient to a second dose of X-rays, of greater intensity than the first dose, to perform treatment of the tumor; subjecting the patient again to the first dose of X-rays to perform imaging of the tumor. – Nanoparticles for their use according to claim 13, characterized in that the nanoparticles are injected in the form of a suspension in a solvent at a concentration of 0.1 mol / L - 5 mol / L. – Nanoparticles for their use according to claim 14, characterized in that the solvent is chosen from water, physiological serum and a buffer solution such as a phosphate buffer. – Nanoparticles for their use according to any one of claims 13 to 15, characterized in that the nanoparticles are administered by intra-arterial injection, intravenous injection, intramuscular injection or subcutaneous injection; or in situ directly into the area to be imaged and treated; or by oral ingestion or cutaneous delivery. – Nanoparticles for their use according to any one of claims 13 to 16, characterized by the fact that the X-ray machine is a spectral photon counting computed tomography (SPCCT) machine. – Nanoparticles for their use according to any one of claims 13 to 17, characterized by the fact that the first dose of X-rays is 0.01 Gy - 0.03 Gy. – Nanoparticles for their use according to any one of claims 13 to 18, characterized by the fact that the second dose of X-rays is 1 Gy - 4 Gy. – Nanoparticles for their use according to any one of claims 13 to 19, characterized in that another drug or immunomodulator is injected at the same time as the nanoparticles. – Nanoparticles for their use according to any one of claims 12 to 20, characterized by the fact that the tumor is a solid tumor, preferably chosen from the group consisting of glioblastoma, brain metastases, meningioma or primary tumors of cervical, rectal, lung, head and neck, prostate, colorectal, liver, pancreatic and breast cancers. – Nanoparticles for their use according to any one of claims 12 to 20, characterized by the fact that the tumor is a metastasis originating from primary melanoma, lung, breast or kidney cancers. – Nanoparticles for their use according to claim 12, characterized in that the method of imaging a tumor comprises the following steps: administering nanoparticles to a patient in need; placing the patient in an X-ray machine; subjecting the patient to a dose of X-rays, to perform a first imaging of a tumor; after a determined time, subjecting the patient to a dose of X-rays, to perform a second imaging of a tumor. – Nanoparticles for their use according to claim 23, characterized in that the nanoparticles are injected in the form of a suspension in a solvent at a concentration of 0.1 mol / L - 5 mol / L. – Nanoparticles for their use according to claim 24, characterized in that the solvent is chosen from water, physiological serum and a buffer solution such as a phosphate buffer. – Nanoparticles for their use according to any one of claims 23 to 25, characterized in that the nanoparticles are administered by intra-arterial injection, intravenous injection, intramuscular injection or subcutaneous injection; or in situ directly into the area to be imaged and treated; or by oral ingestion or cutaneous delivery. – Nanoparticles for their use according to any one of claims 23 to 26, characterized by the fact that the X-ray machine is a spectral photon counting computed tomography (SPCCT) machine. – Nanoparticles for their use according to any one of claims 23 to 27, characterized by the fact that the X-ray dose is 0.01 Gy - 0.03 Gy. – Nanoparticles according to any one of claims 1 to 8 for their use in a method of imaging a tumor and producing one or more reactive oxygen species in said tumor, comprising the following steps: administering said nanoparticles to the patient; exposing the tumor to a first dose of X-rays in a range of 0.01 Gy – 0.03 Gy to generate a first image of a tumor; exposing the tumor to a second dose of X-rays in a range of 1 Gy – 4 Gy to generate the reactive oxygen species in said tumor.

Images