EP4003431A1

EP4003431A1 - Particulate structures made from gold nanoparticles, methods for preparing same and uses thereof for treating solid tumours

Info

Publication number: EP4003431A1
Application number: EP20757379.1A
Authority: EP
Inventors: Gautier LAURENT; Arnaud Beduneau; Stéphane Roux
Original assignee: Universite de Franche-Comte
Current assignee: Universite de Franche-Comte
Priority date: 2019-07-23
Filing date: 2020-07-23
Publication date: 2022-06-01
Also published as: FR3099052A1; CA3146881A1; WO2021014103A1; US20220257801A1; JP2022541073A; FR3099052B1

Abstract

The present invention concerns a particulate structure characterised in that it comprises: a/ a biodegradable polymer particle, b/ gold nanoparticles covered on their surface with macrocyclic chelators complexing at least one ion of interest and/or a radionucleide for medical imaging, c/ a polycation having a positive charge over a pH range from 5 to 11, the gold nanoparticles b/ being encapsulated in the polymer particle a/ and/or adsorbed at the surface of the polymer particle a/. The invention also relates to a method for preparing the particulate structures. The invention further concerns the use of the particulate structures for radiotherapy or chemotherapy in the context of cancer treatment.

Description

Title: Particulate structures based on gold nanoparticles, their preparation processes and their uses in the treatment of solid tumors

Technical area

The present invention relates to the field of chemistry and formulation applied to health. In particular, it relates to novel particle structures that include multifunctional gold nanoparticles, and their uses for radiotherapy, imaging and chemotherapy in the treatment of cancer.

[0002] The invention also relates to a process for preparing these novel particulate structures which consists in particular in encapsulating the multifunctional gold nanoparticles in particles of biodegradable polymer.

Prior art

[0003] The use of gold nanoparticles represents a promising strategy in the diagnosis and treatment of cancer (1), (2).

The small size of the nanoparticles allows an exploration of living things down to the cellular level. These nanoparticles are large enough not to cross biological barriers in healthy tissue and small enough to cross the porous epithelium of solid tumor blood vessels.

Gold nanoparticles are also attractive due to their intrinsic properties. Indeed, the gold element is a noble metal par excellence, very insensitive to external chemical attacks, which also has a biocompatibility suitable for medical applications. Gold nanoparticles have modular optical properties depending on size, shape and dielectric environment. This property is widely used in photothermal therapy and imaging (3). In addition, gold, due to a high atomic number, is characterized by a very high density and absorption cross section of X and y photons. This property, independent of size, confers on gold nanoparticles the behavior of a contrast agent for X-ray computed tomography and a radiosensitizing effect that can be exploited for radiotherapy (4), (5). Finally, the two main synthesis methods described by Brust and Frens are relatively simple to implement. The first consists of a reduction of a gold salt by a strong reducing agent in the presence of thiolated ligands while the Frens method leads to the formation of nanoparticles stabilized by citrate ions using the sodium citrate reducing agent on the salt of 'or (6), (7). The functionalization of these gold nanoparticles, which can be carried out during or after the synthesis, makes it possible to enrich the range of properties. By an appropriate choice of the constituents used for the synthesis of multifunctional gold nanoparticles, it is then possible, despite the reduced size, to integrate within the same object a therapeutic activity and imaging functions.

[0004] The thesis work of G. Laurent (8) has shown that multifunctional gold nanoparticles, namely gold nanoparticles coated on their surface with macrocyclic chelators capable of complexing elements of interest for imaging (Gd ³⁺ for MRI, ¹¹¹ ln ³⁺ for SPECT and ⁶⁴ Cu ²⁺ for PET), show strong potential for image-guided radiotherapy.

These gold nanoparticles thus functionalized indeed have the potential of multimodal contrast agent (MRI, nuclear imaging) and radiosensitizing agent. Once injected intravenously, these nanoparticles exhibited a significant therapeutic effect following their activation by X-ray radiation. Furthermore, the biodistribution of these nanoparticles could be monitored by MRI, SPECT and X-ray tomodensitometry. Multifunctional gold, by virtue of their optical and radiosensitizing properties, therefore represent an extremely interesting approach for the diagnosis and treatment of tumors.

However, despite these promising results, the plasma half-life of these multifunctional gold nanoparticles remains very short, thus slowing their accumulation in tumor areas (accumulation rate of approximately 2%). The too rapid elimination of nanoparticles (renal clearance) can be explained by their small size (hydrodynamic diameter of about 6 to 7 nm) which is nevertheless essential to be able to be eliminated via the kidneys.

[0005] It has thus been proposed to increase the hydrodynamic diameter of gold nanoparticles in order to limit the problem of too rapid renal clearance. However, such an approach considerably reduces the radiosensitizing properties of nanoparticles as well as their elimination from the body via the kidneys (9), (10).

[0006] The inventors of the present invention then imagined encapsulating the multifunctional gold nanoparticles in larger biodegradable polymer particles, which would circulate for longer in the blood and would therefore have more opportunities to accumulate in the tumor, while keeping the renal elimination of nano-objects.

[0007] Approaches to encapsulate gold nanoparticles in biodegradable polymer particles have already been described in the literature. Mention may thus be made of encapsulation by simple oil-in-water emulsion or by double water-in-oil-in-water emulsion described in Wang Y et al (11) or else the synthesis of gold nanoparticles in situ, at namely directly inside the polymeric particles, described in Luque-Michel et al (12).

However, these methods suffer from a low encapsulation efficiency and / or lead to particles of too large size, namely on the order of a micrometer, and also suffer from a lack of size homogeneity (polydisperse particles). In addition, the generally encapsulated gold particles are "naked" (ie unfunctionalized) which results in a lack of colloidal stability in a physiological medium and a problem of elimination during the degradation of the polymeric particle, in vivo.

summary

[0008] One of the aims of the present invention is to develop new particle structures which comprise multifunctional gold nanoparticles, and which have a sufficiently long plasma half-life (namely from 15 minutes to 120 minutes) in order to '' improve their accumulation in the tumor zone and better exploit the radiosensitizing potential of Multifunctional gold nanoparticles.

Another aim of the invention is to develop new particle structures which are biodegradable transporters, which exhibit a sufficiently long plasma half-life (circulation time in the blood) in order to fully exploit the promising potential of the nanoparticles of multifunctional gold for imaging guided radiotherapy.

Another aim of the invention is to develop new particle structures which, while exhibiting a sufficiently long plasma half-life to improve their tumor accumulation, then rapidly degrade in the blood and are eliminated via the kidneys. .

Another object of the present invention is to develop an original process for preparing these novel particulate structures, said process making it possible to effectively encapsulate the multifunctional gold nanoparticles in biodegradable polymer particles, namely with a encapsulation yield greater than 90%, close to 100%, or even equal to 100%.

Another aim of the invention is to develop a process making it possible to prepare particle structures of the order of one nanometer, namely which have a diameter ranging from 50 to 200 nm, and which have a narrow size distribution (at know which have a low polydispersity index).

Another aim of the invention is to develop a process making it possible to prepare particulate structures as defined above, with high reproducibility, both for the degree of charge obtained (degree of encapsulation) and for the size. particles obtained.

During their research concerning the synthesis of biodegradable polymer particles encapsulating gold nanoparticles, the inventors were particularly interested in methods based on the method of nanoprecipitation by displacement of solvent (13).

They thus surprisingly discovered that the process for preparing such particulate structures could be greatly improved by the use of a polycation having a positive charge over a wide pH range, namely a pH range from 5 to 11. .

Indeed, the polycation makes it possible to electrostatically trap the nanoparticles. multifunctional gold, which facilitates and makes possible in particular their encapsulation in the particles of biodegradable polymer.

[0011] A more particular subject of the present invention is a particulate structure characterized in that it comprises:

a / a particle of biodegradable polymer,

b / gold nanoparticles coated on their surface with macrocyclic chelators complexing at least one ion of interest and / or one radionuclide for medical imaging,

cl a polycation with a positive charge over a pH range from 5 to 11,

the gold nanoparticles b / being encapsulated in the polymer particle a / and / or adsorbed to the surface of the polymer particle a /.

The term "nanoparticle" designates an object, regardless of the shape, at least one of its dimensions of which is between 1 and 100 nanometers.

The particulate structure of the invention designates in particular a particle of biodegradable polymer a / inside which gold nanoparticles b / are encapsulated and / or on the surface of which gold nanoparticles b / are adsorbed.

[0013] Regarding the gold nanoparticles, the possible shapes can be spheres, nanoshells (heart-shell), nanoparticles. The spherical shape is however an approximation. Indeed, gold crystallizes in a face-centered cubic lattice and thus forms a polyhedral object that can be likened to a sphere.

[0014] According to the invention, the gold nanoparticles and the biodegradable polymer particles are preferably spherical in shape. Likewise, the particulate structure of the invention is preferably spherical in shape.

The gold nanoparticles of the particulate structures of the invention, coated on their surface with macrocyclic chelators complexing at least one ion of interest and / or one radionuclide for medical imaging, can also be referred to indifferently as nanoparticles of. or "functional" (as opposed to "naked" gold nanoparticles), "multifunctional", "functionalized", Radiosensitizing functionalized gold nanoparticles etc. They could simply be designated in what follows by gold nanoparticles b /. Such gold nanoparticles b / are therefore composed of a gold core surrounded or covered with an organic layer consisting of macrocyclic chelators complexing ions of interest and / or radionuclides.

[0016] The essential role of the organic layer, besides colloidal stability, is to allow the complexation of elements for medical imaging (ion of interest, radionuclide) in order to be able to follow the b / gold nanoparticles by imaging.

The functional gold nanoparticles b / can also be designated by the acronym Au @ L (M) in which Au represents gold, L (M) represents the macrocyclic chelator (namely L) complexing the ion d 'interest and / or the radionuclide (ie M).

The macrocyclic chelator L can also be designated by macrocyclic ligand or ligand.

[0019] Schematic representations of the functionalized gold nanoparticles are given in Figures 1 a, 1 b and 1 c.

[0020] For the purposes of the invention, the term “biodegradable polymer” means a polymer which will degrade or be absorbed naturally in the body of a subject. The biodegradable polymer can also be referred to as a bioresorbable polymer. The particle of biodegradable or bioresorbable polymer may be designated in the following as polymer particle a /, polymeric particle a /.

The polycation exhibiting a positive charge over a wide pH range as defined above may be referred to in the following as polycation cl. Said polycation c / will always be found near the gold nanoparticles b / since it is in electrostatic interaction with them. Thus the polycation c / can be encapsulated in the polymer particle a / and / or adsorbed to the surface of the polymer particle a /.

[0022] The particulate structure which is the subject of the invention is further characterized in that it comprises a surfactant adsorbed on the surface of the α / polymer particle. Said surfactant, when it is present, is therefore always present at the surface of the polymer particle a / and is never encapsulated within the latter. The presence of the surfactant depends on the nature of the biodegradable polymer of the nanoparticle.

The surfactant of the invention is in particular polyvinyl alcohol (PVA) and / or a poloxamer, and is preferably PVA.

By way of examples of a poloxamer, mention may be made of those sold under the name Pluronic F-127 (Poloxamer 407), P85, L64.

[0023] Schematic representations of particulate structures of the invention with the surfactant are given in Figures 2a, 2b and 2c.

[0024] According to another aspect of the invention, the particulate structure further comprises at least one active principle encapsulated in the polymer particle a /, said active principle preferably being a chemotherapeutic agent and / or a fluorophore.

[0025] By way of example of a chemotherapeutic agent, there may be mentioned temozolomide, paclitaxel, docetaxel and etoposide.

By way of example of a fluorophore, mention may be made of indocyanine green (which is used clinically for imaging) or other fluorophores such as cyanine 5, cyanine 7 or DU (IUPAC name: "(2Z) -2 - [(E) -3- (3,3-dimethyl-1 -octadecylindol-1 -ium-2-yl) prop-2-enylidene] -3,3-dimethyl-1 -octadecylindole; perchlorate ').

[0027] Thus according to the invention, the polymer particle a1 advantageously allows the co-encapsulation of functional gold nanoparticles b / and at least one active principle.

[0028] Schematic representations of particulate structures of the invention with the active principle are given in Figures 3a, 3b and 3c.

[0029] According to the invention, the macrocyclic chelators as mentioned above, which cover the gold nanoparticles, each comprise:

an anchoring function which comprises at least one sulfur atom making it possible to attach the macrocyclic chelator to the gold nanoparticle, and which preferably comprises two sulfur atoms forming an endocyclic disulfide bond,

at least one complexation site of ions of interest and / or radionuclides for medical imaging, said complexation site comprising at least one carboxylic acid function and / or an amine function,

a spacer arm located between the anchoring function and the complexation site (s),

optionally a functionalization site allowing the grafting of the chelator with a targeting agent towards cancer cells.

[0030] The bond between at least one sulfur atom of the anchoring function and the gold nanoparticle more particularly designates an ionocovalent bond, which is an intermediate bond between a covalent bond and an ionic bond.

[0031] The macrocyclic chelator covering the gold particles is more particularly characterized in that:

- the anchoring function is a radical chosen from the group comprising:

, ^* -N- (CH ₂ -CH ₂ -SH) ₂ , ^* -C (= 0) - (CH ₂ ) _n -SH with n being an integer ranging from 2 to 5 and mixtures thereof;

- the spacer arm is a radical chosen from the group comprising:

* - (CH ₂ ) ₂ -CO-NH- (CH ₂ ) ₂ -NH- ^* , ^* -NH- (CH ₂ -CH ₂ -0) _m -CH ₂ -CH ₂ -NH- ^* with m an integer equal to 0, 4 or 1 1, and mixtures thereof

- the functionalization site, if it is present, is a radical, originating from an amino acid, chosen from the group comprising:

^* -NH-CH ((CH ₂ ) ₄ -NH ₂ ) -CO- ^* , ^* -NH-CH (CH ₂ -OH) -CO- ^* ,

^* -NH-CH (CH-OH-CH ₃ ) -CO- ^* , ^* -NH-CH (CH ₂ -C ₆ H ₄ -OH) -CO- ^* ,

* -NH-CH ((CH ₂ ) _n -NH- ^* ) -CO- ^* with n ranging from 2 to 5, and mixtures thereof.

By way of example of the amino acid from which the functionalization site originates, mention may be made of lysine, serine, threonine, tyrosine.

[0032] According to one embodiment of the invention, the macrocyclic chelator is chosen from the group comprising:

TADOTAGA, TANODAGA, TADFO, TA [DOTAGA-lys-NH ₂ ], TA [NODAGA-lys-NH ₂ ], TA [DOTAGA-lys-NODAGA] and mixtures thereof.

The meanings of these abbreviations are described below.

DOTAGA: "1, 4,7,10-tetraazacyclododecan-1 -glutaric acid-4, 7,10-triacetic acid". NODAGA: "1, 4, 7-triazacyclononane-1 -glutaric acid-4, 7-diacetic acid". DFO: "Deferroxamine".

TADOTAGA refers to the derivative of DOTAGA with the addition of a thioctic acid (TA) function.

TANODAGA designates the derivative of NODAGA with the addition of a thioctic acid (TA) function.

TADFO is the derivative of DFO with the addition of a thioctic acid (TA) function. TA [DOTAGA-lys-NFl2] denotes the derivative of TADOTAGA with the addition of an amine function via lysine.

TA [NODAGA-lys-NFl2] denotes the derivative of TANODAGA with the addition of an amine function via lysine.

TA [DOTAGA-lys-NODAGA] denotes a compound comprising a DOTAGA unit and a NODAGA unit linked together by lysine with the addition of the thioctic acid (TA) function.

[0033] The organic layer surrounding the gold core, consisting of macrocyclic chelators, may be a "mixed" layer which means that it consists of a mixture of macrocyclic chelators.

As examples of a mixture, there may be mentioned [(TADOTAGA) (TANODAGA)], which denotes a mixture of TADOTAGA and TANODAGA, [(TADOTAGA) (TADFO)], which denotes a mixture of TADOTAGA and TADFO .

[0035] According to another embodiment of the invention:

- the ion of interest for medical imaging, and more particularly for magnetic resonance imaging (MRI), is chosen from the group comprising Gd3 +, Ho3 +, Dy3 + and their mixtures;

- the radionuclide for medical imaging, and more particularly for nuclear imaging (TEMP or PET), is chosen from the group comprising ⁶⁴ Cu, ⁸⁹ Zr, ⁸⁸ Ga,

¹¹¹ ln and their mixtures.

Magnetic Resonance Imaging (MRI) is an imaging technique that allows three-dimensional visualization of biological tissues based on the principle of nuclear magnetic resonance (NMR). MRI exploits the magnetic properties of protons in water (a major constituent of biological tissue, around 80%) which depend on the environment and therefore on the tissue.

Nuclear imaging techniques require the injection of radionuclides to perform functional imaging of the organism. Two techniques can be distinguished: single photon emission tomography (SPECT) which uses emitters of y photons and positron emission tomography (PET) which relies on the use of emitters of b ⁺ positrons.

[0036] SPECT and PET have the advantage of having a very high sensitivity and of being able to perform functional imaging.

The b / functional gold nanoparticles, represented by Au @ L (M), can therefore be followed by MRI (when M is an ion of interest), TEMP or PET (when M is a radionuclide) and by X imaging ( thanks to gold).

[0037] The @ symbol designates the bond or the ionocovalent bond between the anchoring function of the macrocyclic chelator L and the gold nanoparticle.

[0038] The particulate structure of the invention is further characterized in that the polycation is chosen from the group comprising polyethyleneimine (PEI), polylysine, polyarginine, polyamidoamine (PANAM), a poly (-amino ester), chitosan and mixtures thereof, and is preferably polyethyleneimine. As a more specific example, branched polyethyleneimine will be mentioned (as opposed to linear).

The term polycation is used because each of the compounds described above comprises amine groups which may or may not be charged by protonation depending on the pH. As already indicated, the polycation used in the context of the invention exhibits a positive charge over a wide pH range, namely a pH range from 5 to 11.

[0039] According to another aspect, the biodegradable polymer of the particle is chosen from the group comprising poly (lactic-co-glycolic acid) (PLGA), poly (lactic acid) (PLA), poly acid (glycolic) (PGA), polycaprolactone (PCL), a polyanhydride, the copolymers of each of said polymers with polyethylene glycol (PEG) and mixtures thereof, and is preferably PLGA or the copolymer (PLGA-PEG).

PLGA is a hetero copolymer of lactic acid and glycolic acid obtained by a copolymerization reaction. The monomers are linked by ester bonds and the result is a linear aliphatic polyester comprising x units of lactic acid and y units of glycolic acid. Thus, PLGA 75/25 identifies a copolymer whose composition is 75% lactic acid and 25% glycolic acid with a molecular mass of between 7000 and 17000 g / mole. PLGA 50/50 is more particularly preferred.

PLGA is used in drug delivery due to its excellent biocompatibility and biodegradability in lactic acid and glycolic acid, which are two monomers naturally produced by metabolic pathways.

As an indication, when the biodegradable polymer is the copolymer (PLGA-PEG), the particulate structure of the invention does not include a surfactant.

As an indication, the developed formulas of macrocyclic chelators, polycations and biodegradable polymers are given in Figure 4.

According to yet another aspect of the particulate structure of the invention, the macrocylic chelator present at the surface of the gold nanoparticles is linked to an active targeting agent for integrins anbiii overexpressed on neovessels of tumors, said agent of targeting preferably being the cyclic RGD peptide.

[0042] The addition of a targeting agent allows for active targeting, in addition to passive targeting. The affinity of the biomolecule with the receptors overexpressed at the level of the tumor or neovessels of the tumor (case of RGD) will thus allow a longer retention of the gold nanoparticles in the targeted area.

The particulate structure is further characterized in that:

- the hydrodynamic diameter of the polymer particle a / is from 50 to 200 nm, preferably from 70 to 160 nm;

- the hydrodynamic diameter of the gold nanoparticles b / is 3 to 15 nm, preferably 6 to 10 nm.

[0044] The hydrodynamic diameter of a particle takes into account the diameter of the particle and of its so-called "hydration" layer.

In the present case, the hydrodynamic diameter of the polymer particle a / is the diameter of the polymer particle a / on the surface of which the gold nanoparticles b / and / or the surfactant are adsorbed.

In other words, the diameter of the polymeric particle a1 with its layer formed by the gold nanoparticles b / and / or the surfactant constitutes the hydrodynamic diameter of the polymeric particle a /. The diameter of the particulate structure is therefore equal to the hydrodynamic diameter of the polymer particle a /.

The hydrodynamic diameter of gold nanoparticles b / refers to the diameter of gold nanoparticles coated on their surface with macrocyclic chelators complexing at least one ion of interest and / or one radionuclide.

According to one embodiment of the invention, the particulate structure is more particularly characterized in that the gold nanoparticles b / and optionally the active principle are encapsulated in the polymer particle a /, said gold nanoparticles b / which can also optionally be adsorbed to the surface of the polymer particle a /.

A subject of the invention is also a process for preparing a particulate structure as defined above (namely in which the gold nanoparticles b / (and optionally the active principle) are encapsulated in the particle of polymer a1 and optionally adsorbed to the surface of the polymer particle a /). This process can be performed using either of the two methods described below, and may be referred to as the "encapsulation process".

[0048] Method 1

According to one embodiment, the method of the invention is characterized in that it comprises the following steps:

- bringing an aqueous suspension of b / gold nanoparticles into contact with an aqueous polycation solution, in order to obtain an assembly of b / gold nanoparticles and polycation;

- Contacting the assembly of gold nanoparticles b / and polycation as defined in the previous step with a mixture of biodegradable polymer and organic solvent miscible with water, said organic solvent optionally being mixed beforehand with at least one active principle, in order to obtain a mixture of gold nanoparticles b /, of polycation, of biodegradable polymer and optionally of active principle,

- contacting the mixture of gold nanoparticles b /, polycation, polymer and optionally active principle as defined in the previous step, with water, optionally added with a surfactant, in order to precipitate in the form of particles the polymer around the gold nanoparticles b / and possibly the active principle,

the encapsulation yield of the gold nanoparticles b / and optionally of the active principle, in the polymer particles a / is at least 75%, preferably at least 90%, and more preferably still at least 95%.

[0049] Method 2

According to another embodiment, the method of the invention is characterized in that it comprises the following steps:

- bringing an aqueous polycation solution into contact with a mixture of biodegradable polymer and organic solvent miscible with water, said organic solvent optionally being mixed beforehand with at least one active principle,

- bringing the polycation assembly into contact with the mixture of biodegradable polymer and organic solvent as defined in the previous step with the aqueous suspension of gold nanoparticles b / in order to obtain a mixture of gold nanoparticles b /, of polycation, of biodegradable polymer and optionally of active principle,

- contacting the mixture of gold nanoparticles b /, polycation, polymer and optionally active principle as defined in the previous step, with water, optionally added with a surfactant, in order to precipitate in the form of particles, the biodegradable polymer around the gold nanoparticles b / and possibly the active principle,

As already indicated, the active principle can be a fluorophore and / or a chemotherapeutic agent.

The encapsulation efficiency of the gold nanoparticles denotes the final mass of gold (namely the mass of gold encapsulated and optionally the mass of gold adsorbed) relative to the mass of gold used. Indeed, during the encapsulation process, it is possible that some of the gold nanoparticles are not found in the biodegradable polymer particle but are found adsorbed on the surface of the biodegradable polymer particle. The final gold mass is identical to the mass of gold used if the encapsulation yield is 100%. However, this can mean that some of the gold nanoparticles are found on the surface of the biodegradable polymer particle.

The encapsulation yield of the active ingredient refers to the mass of active ingredient encapsulated relative to the mass of active ingredient used. The active principle is always found in the biodegradable polymer particle and never on its surface.

Regarding the biodegradable polymer, the final polymer mass is identical to the polymer mass used if the manufacturing yield is 100%.

The degree of encapsulation (also referred to as the charge rate) of the gold nanoparticles denotes the final mass of gold (namely the mass of encapsulated gold and possibly the mass of gold adsorbed) relative to the mass of biodegradable polymer particles formed.

The charge rate of gold nanoparticles obtained with the encapsulation process denotes the final mass of gold (namely the mass of gold encapsulated and possibly the mass of gold adsorbed) relative to the mass of polymer particles biodegradable formed.

The degree of encapsulation of the active ingredient refers to the mass of final active ingredient (namely the mass of encapsulated active ingredient) relative to the mass of biodegradable polymer particles formed.

[0056] These are effective masses that are measured after formulation.

[0057] As an indication, the degree of encapsulation of the gold nanoparticles is 1 to 4%, preferably 1 to 3%, and more preferably still about 1, 4%.

[0058] The degree of encapsulation of the active principle is 0.5 to 5%, preferably 1 to 3%, and more preferably still about 2%.

The preparation process of the invention described above (encapsulation process) advantageously allows an encapsulation yield of more than 75%, preferably at least 90%, and more preferably still at minus 95%, whereas without the use of the polycation, the encapsulation efficiency, as well as the encapsulation rate, is impaired.

The use of the polycation as defined above in the process of the invention advantageously makes it possible to obtain high encapsulation yields, namely close to 100%, or even equal to 100%, which presents in particular a strong interest in terms of cost and time.

According to another embodiment of the invention, the particulate structure is more particularly characterized in that the gold nanoparticles b / are adsorbed on the surface of the polymer particle a /, and the active principle, s' it is present, is encapsulated in the polymer particle.

In this scenario, the particle of polymer a / is a particle "filled" with polymer a1 in which there is still optionally an active principle.

A further subject of the invention is a process for preparing a particulate structure as defined above (namely in which the gold nanoparticles b / are adsorbed to the surface of the polymer particle a / and the active principle, if present, is encapsulated in the polymer particle a /). This process may also be called "adsorption process", and is characterized in that it comprises the following steps:

- Contacting a mixture of biodegradable polymer and organic solvent miscible with water, said organic solvent optionally being mixed beforehand with at least one active principle, with water, optionally added with a surfactant, in order to precipitate the biodegradable polymer in the form of particles on the surface of which the surfactant is adsorbed if it is present,

- bringing the particles of polymer a / as defined in the previous step into contact with an aqueous solution of a polycation, in order to obtain particles of polymer a / on the surface of which the polycation is adsorbed, said particles of polymer biodegradable also encapsulating the active principle if it is present,

- Contacting the polymer particles a / on the surface of which the polycation is adsorbed as defined in the previous step with a aqueous suspension of gold nanoparticles b /, in order to lead to adsorption of gold nanoparticles b / to the surface of the polymer particles a /,

the adsorption efficiency of the gold nanoparticles b / to the surface of the polymer particle a / is 30 to 70%, preferably 40 to 60%.

[0064] The adsorption efficiency of gold nanoparticles refers to the final mass of gold (ie the mass of gold adsorbed) relative to the mass of gold used.

[0065] The charge rate of gold nanoparticles obtained with the adsorption process refers to the final mass of gold (ie the mass of gold adsorbed) relative to the mass of biodegradable polymer particles formed.

[0066] Without the use of polycation, the adsorption efficiency would be zero.

The process of the invention relates to both the encapsulation process according to one of the two methods described above and the adsorption process described above, the common and original characteristic of these processes being the use of a polycation.

The charge rate obtained with the encapsulation process (namely gold nanoparticles inside the polymer particle and optionally on the surface of the polymer particle) is compared to the charge rate obtained with the adsorption process (gold nanoparticles only on the surface of the polymer particle), to show that there is indeed an encapsulation given the different charge rate.

Schematic representations of the preparation methods of the invention are given in Figure 5a (encapsulation process) and Figure 5b (adsorption process).

[0070] According to an advantageous embodiment of the preparation process of the invention:

- the aqueous solution of gold nanoparticles b / is at a concentration of 8 to 12 grams of gold nanoparticles per liter of water,

- the aqueous polycation solution is at a concentration of 30 to 70 grams of polycation per liter of water,

- the mixture of biodegradable polymer with the organic solvent miscible with water, is at a concentration of 10 to 20 grams of polymer per liter of solvent, said organic solvent is chosen from the group comprising dimethylsulfoxide (DMSO), dimethylformamide (DMF) and N-methyl-pyrrolidone,

- the amount of active ingredient, if present, in the organic solvent is at a concentration of 0.15 to 0.75 grams of active ingredient per liter of solvent,

- the amount of surfactant, if present, in the water is 5 to 10 grams of surfactant per liter of water.

These different concentrations or amounts are valid both for the encapsulation and adsorption process.

As already indicated, the presence or absence of the surfactant depends on the nature of the biodegradable polymer used. Thus when the biodegradable polymer is PEG or a copolymer (PLGA-PEG), it is then not necessary to use a surfactant. When the biodegradable polymer is PLGA, the presence of the surfactant is then necessary. The surfactant will, for example, be polyvinyl alcohol (PVA).

According to another advantageous embodiment of the preparation process of the invention, the polycation / gold ratio, namely the “aqueous polycation solution / aqueous suspension of gold nanoparticles b /” ratio varies from 4 to 8 , and is preferably 5.

According to yet another advantageous embodiment of the preparation process of the invention, and more particularly of the encapsulation process, the pH of the aqueous polycation solution varies from 9 to 11, and is preferably 10, 8.

The pH of the polycation solution influences the size of the polymer particle obtained. A pH of 10.8 produces particles of a / polymer with a hydrodynamic diameter of about 150 nm.

The original preparation process of the invention, which consists in using a polycation, leads to the production of particulate structures which have a monodisperse size and can be modulated according to the polycation / gold ratio and according to the pH of the aqueous solution of polycation. As an indication, the polydispersity index of the particulate structures must be less than 0.25. The particulate structures of the invention exhibit a polydispersity index of about 0.16.

[0078] The polydispersity index represents the size distribution of a population of particles. The lower the index, the more monodisperse (homogeneous size) the sample. Conventional methods, which do not use polycation, lead to polydisperse particles and / or generally large in size (of the order of a micrometer) and which include a low encapsulation yield.

In addition to obtaining particles of the order of a nanometer and which have a homogeneous size, the preparation process of the invention is also advantageous in that it is highly reproducible, both for the charge rate (rate of encapsulation) obtained as the size of the particles obtained.

The method of the invention is also advantageous in that it makes it possible to encapsulate gold nanoparticles b /, namely gold nanoparticles already functionalized, which in particular have the properties of contrast agent required for the MRI, and optionally an active principle, with an encapsulation yield close to 100%, or even 100%.

The main field of application of the particulate structures of the invention is imaging coupled with the treatment of tumors by radiotherapy.

The particles of biodegradable polymer a /, such as for example the particles of PLGA, will play the role of transporter, and the gold nanoparticles b / encapsulated and / or adsorbed will play the role of contrast agent and radiosensitizing agent. . The primary interest of the encapsulation (or adsorption) of gold nanoparticles b / in (at the surface of) polymer particles a / is to increase the plasma half-life of gold nanoparticles b / in order to improve their tumor accumulation and to better exploit their radiosensitizing potential. As an indication, the plasma half-life of the PLGA particles is 15 days. The gold nanoparticles b / thus encapsulated and / or adsorbed circulate for a longer time in the blood and have the possibility of accumulating in greater quantities in the tumor. The enhanced tumor accumulation of gold nanoparticles increases the synergistic effect with the radiotherapy. In addition, once the polymer particles have been degraded, the functionalized gold nanoparticles b / return to the bloodstream and can be rapidly eliminated via the kidneys.

[0080] Furthermore, the role of bioresorbable polymer particles a / is not limited to the transport of functionalized b / radiosensitizing gold nanoparticles. In fact, the polymeric particles al allow, in addition to the encapsulation of the gold nanoparticles b /, the encapsulation of at least one active principle such as a chemotherapeutic agent and / or a fluorophore.

[0081] This co-encapsulation confers on the particulate structures of the invention extremely interesting therapeutic properties, since the particulate structures of the invention make it possible to combine radiotherapy guided by imaging and chemotherapy and thus improve the treatment of tumors.

[0082] The particulate structures of the invention advantageously make it possible to perform radiotherapy in order to improve the effect of the therapy while reducing the side effects, in particular in the case of treatment of tumors.

A subject of the invention is also a pharmaceutical composition containing a therapeutically effective amount of at least one particulate structure as defined above.

The amount of particulate structures may vary depending on the intended applications, the age and weight of the patient.

The particulate structures or the pharmaceutical composition of the invention may be in a form suitable for intravenous administration. By way of examples, mention may be made of injectable suspensions.

A subject of the present invention is also a particulate structure as defined above, for use in the treatment of solid cancerous tumors.

The invention also relates to a method of therapeutic treatment of solid cancerous tumors comprising the administration to a subject of a therapeutically effective amount of at least one particulate structure or of a composition as defined above. A further subject of the present invention is a particulate structure for use as defined above, by radiotherapy or chemotherapy, and more particularly by radiotherapy guided by imaging.

The invention also relates to a method of therapeutic treatment by radiotherapy or chemotherapy, and more particularly by radiotherapy guided by imaging, comprising the administration to a subject of a therapeutically effective amount of at least one particulate structure or of a composition as defined above.

Brief description of the drawings

[0089] Other features, details and advantages will become apparent on reading the detailed description below, and on analyzing the accompanying drawings.

Fig. 1a

[0090] [Fig. 1 a] is a schematic representation of b / functionalized gold nanoparticles in which the macrocyclic chelators are complexed to ions of interest.

Fig. 1 b

[0091] [Fig. 1 b] is a schematic representation of b / functionalized gold nanoparticles in which the macrocyclic chelators are complexed to a radionuclide.

Fig. 1 C

[0092] [Fig. 1 c] is a schematic representation of b / functionalized gold nanoparticles in which the macrocyclic chelators are complexed with ions of interest and a radionuclide.

Fig. 2a

[Fig. 2a] is a schematic representation of a particulate structure of the invention comprising a biodegradable polymer particle a1 in which 100% of the gold nanoparticles b / are encapsulated. The gold nanoparticles form electrostatic interactions with the polycation. Fig. 2b

[Fig. 2b] is a schematic representation of a particulate structure of the invention comprising gold nanoparticles b / encapsulated in the biodegradable polymer particle a / and adsorbed to the surface of the polymer particle a /.

Fig. 2c

[Fig. 2c] is a schematic representation of a particulate structure of the invention in which 100% of the gold nanoparticles b / are adsorbed to the surface of the polymer particle a /.

A surfactant, adsorbed to the surface of the α / polymer particle, is shown in each of Figures 2a, 2b and 2c. The presence of the latter is however optional, and each of these figures could also be represented without the surfactant.

The polycation is not shown with its positive charge in each of the particulate structures of the invention so as not to encumber each of Figures 2a, 2b and 2c.

Fig. 3a

[0093] [Fig. 3a] is a schematic representation of a particulate structure of the invention corresponding to that of Figure 2a but which further comprises an active ingredient encapsulated in the polymer particle a /.

Fig. 3b

[0094] [Fig. 3b] is a schematic representation of a particulate structure of the invention corresponding to that of Figure 2b but which further comprises an active ingredient encapsulated in the a / polymer particle. Fig. 3c

[0095] [Fig. 3c] is a schematic representation of a particulate structure of the invention corresponding to that of Figure 2c but which further comprises an active principle encapsulated in the polymer particle a /. The active principle is represented by a star in each of Figures 3a, 3b and 3c.

Fig. 4a

[Fig. 4a] represents the structural formulas of the macrocyclic chelators (L).

Fig. 4b

[Fig. 4b] represents the structural formulas of the polycations.

Fig. 4c

[Fig. 4c] represents the structural formulas of biodegradable polymers.

Fig. 5a

[0097] [Fig. 5a] represents the process for preparing the particulate structures of the invention in which the gold nanoparticles b / are encapsulated in the polymer particle a /, some of the gold nanoparticles b / still being adsorbed to the surface of the polymer particle a / (encapsulation process according to method 2).

Fig. 5b

[Fig. 5b] represents the process for preparing the particulate structures of the invention in which the gold nanoparticles b / are adsorbed to the surface of the polymer particle a / (adsorption process).

In the event that an active ingredient is added, the latter is mixed with the organic solvent and the biodegradable polymer, whether it is the encapsulation process or the adsorption process.

In these figures "Gold Np" refers to gold nanoparticles.

Fig. 6

[0098] [Fig. 6] represents a photograph taken by transmission electron microscopy of a particulate structure of the invention in which one can distinguish a polymer particle a / comprising several encapsulated and / or adsorbed gold nanoparticles.

Fig. 7 [0099] [Fig. 7] represents a blood kinetics graph showing the change in the dose of gold injected (in percentage) per gram of blood as a function of time, for the gold nanoparticles alone (designated by “Np of gold”), gold nanoparticles encapsulated in PLGA particles (designated as “NP3”) or in PLGA-PEG particles (designated as “NP3-PEG”).

[0100] Description of the embodiments

[0101] Examples

[0102] Preparation of particulate structures according to the invention in which:

- the biodegradable polymer a / is poly (lactic-co-glycolic acid) (PLGA) or a poly (lactic-co-glycolic acid) and polyethylene glycol (PLGA-PEG) conjugate,

- the macrocyclic chelator is TADOTAGA and the ion of interest is gadolinium (Gd3 +),

- the polycation is polyethyleneimine (PEI).

The surfactant is polyvinyl alcohol (PVA) and the water-miscible organic solvent is dimethyl sulfoxide (DMSO).

The b / gold nanoparticles, coated on their surface with the TADOTAGA chelator complexing gadolinium ion, are represented in the following by:

"Au @ TADOTAGA (Gd)".

G0103Ί Material

[0104] More particularly, PLGA 50:50 (PM 7000-17000 Da) (marketed under the name Resomer® RG 502H) comes from Evonik Industries (Evonik Rohm GmbH) and PLGA-PEG 50:50 (PLGA: PM 25000 Da, PEG: PM 5000 Da) comes from Sigma Aldrich (St Louis, USA).

Chloroauric acid (HAUCI ₄ .3H ₂ O), sodium borohydride (NaBH ₄ ), PVA (MW 30000-70000 Da), branched polyethyleneimine (PEI) (MW 25000 Da), gadolinium chloride (GdCl ₃ , 6H ₂ 0) and dimethylsufloxide (DMSO) are from Sigma Aldrich (Saint Louis, United States). The TADOTAGA ligand comes from Chematech (Dijon, France).

[0105] Synthesis of Au @ TADOTAGA nanoparticles (Gd)

The synthesis of gold nanoparticles is adapted from the single-phase protocol developed by Brust et al (6). Gold nanoparticles are obtained by reduction gold salt (HAUCI4.3H2O) with NaBhU in the presence of the ligand TADOTAGA. The adsorption of TADOTAGA on the surface of the gold nanoparticles makes it possible to control the size and the colloidal stability and allows the immobilization of gadolinium. More particularly, HAUCI4.3H2O (50 mg, 1.22x10 ⁴ mol), dissolved in methanol (20 ml_), is placed in a 250 ml round bottom flask. The TADOTAGA ligand (86 mg, 1.22 x 10 ⁴ mol) in water (10 mL) is added to the golden salt solution with stirring. The mixture changes from yellow to orange. After a few minutes, NaBhU (48 mg, 12.7 x 10 ⁴ mol) dissolved in water (3 mL) is added to the mixture with vigorous stirring at room temperature. Stirring is maintained for 1 h. Then, the mixture is dialyzed using a 6000-8000 kDa MWCO membrane.

To obtain the final Au @ TADOTAGA (Gd) suspension ([Au] = 51 mM, [Gd] = 5 mM) before the encapsulation process in the polymer particles, the gold suspension is concentrated and the gadolinium is trapped in the TADOTAGA chelator by shaking the suspension overnight with GdCl ₃ , 6H ₂ 0 (370 pL at 135 mM for an Au @ TADOTAGA (Gd) suspension at 10 mL). The gadolinium concentration of 5 mM guarantees the stability of the suspension and an optimal MRI signal.

Synthesis of PLGA or PLGA-PEG polymer particles encapsulating Au @ TADOTAGA (Gd)

The process for preparing the polymer particles encapsulating the gold nanoparticles b / (Au @ TADOTAGA (Gd)) is based on the method of nanoprecipitation by displacement of solvent (13), with the originality, however, of using the PEI. The inventors have determined that the size of the polymer particles is adjustable as a function of the PEI / gold ratio and of the pH of the aqueous solution of PEI.

[0110] The inventors were able in particular to determine during their research that a PEI / gold ratio of 5 and that a pH of about 10.8 was appropriate for obtaining polymeric particles having a hydrodynamic diameter of about 160 nm. . Indeed, a size of 160 nm + 15 nm is advantageous in that it makes it possible to encapsulate a satisfactory quantity of gold nanoparticles b / while allowing a satisfactory production yield. [0111] An aqueous solution of PEI (25 ml, 5% w / w) is mixed with 1 ml of PLGA solution or of PLGA-PEG solution in DMSO at 15 mg / ml and 18 mg / ml, respectively.

[0112] 1N HCl is previously added to the aqueous solution of PEI in order to obtain a hydrodynamic diameter of the PLGA particles close to 160 nm + 15 nm.

In order to modulate the PEI / gold ratio for the preparation of different particles, only the concentration of the PEI is adjusted. The same volume of HCl is added to the solution as for preparing PLGA particles with a diameter of about 160 nm, regardless of the concentration of PEI.

A suspension of Au @ TADOTAGA (Gd) (25 μL, 10 mg / mL (ie 51 mM)) is added to the preceding solution comprising the PEI and the PLGA.

Next, 4 ml of PVA dissolved in 0.75% water are gradually added to the mixture, previously stirred in a vortex.

[0116] For the preparation of the PLGA particles by adsorption of the gold nanoparticles, the PLGA particles are previously formed according to the same protocol as the conventional PLGA particles.

Then, a 5% solution of PEI (25 μL) is transferred into the suspension of PLGA particles with stirring. After 5 minutes of incubation, a suspension of Au @ TADOTAGA (Gd) (25 μL, 10 mg / mL (ie 51 mM)) is finally added to the PLGA particles coated with PEI.

[0118] The different preparations are washed three times by ultracentrifugation at 30,000 G for 1 h, at 4 ° C to remove the free gold nanoparticles. Finally, the preparations are lyophilized using sucrose as a cryoprotectant, except in the batches used to estimate the production yield, the encapsulation yield and the encapsulation rate.

These parameters are estimated as follows:

Quantity of PLGA particles formed

Production efficiency (%) = Quantity of PLGA used x 100 (1) Amount of gold encapsulated and possibly adsorbed

Encapsulation yield (%) = x 100

Amount of gold used

(2)

Amount of gold encapsulated and possibly adsorbed

Encapsulation rate (%) = x 100

Quantity of PLGA particles formed (3)

[0120] The different characteristics of the particles obtained according to this protocol by varying the PEI / Gold ratio are described in Table 1 below:

[0121] [Table 1]

[0122] Particles are thus obtained having a hydrodynamic diameter ranging from 130 nm to 200 nm (the size can be further reduced by adjusting the PEI / gold ratio) with an encapsulation rate of approximately 1.4. The reduction in size inevitably results in a reduction in production efficiency due to the centrifugal washing.

The NP3 particles (PEI / gold ratio of 5) are selected for the in vivo tests. These particles represent a good compromise between size and production yield. The degree of encapsulation is half as important in the case of the adsorption protocol (adsorbed NP3) than that of encapsulation (NP3), which clearly indicates the encapsulation of the gold nanoparticles. The presence of gold is confirmed by transmission electron microscopy imaging (see Figure 6).

[0124] Image-guided therapy [0125] The particulate structures of the invention are promising candidates for imaging-guided therapy if they show an adapted behavior after intravenous injection: accumulation in the area to be treated, absence of nanoparticles in the surrounding healthy tissues, privileged renal elimination ( compared to the hepatobiliary route) and if the plasma half-life is increased compared to gold nanoparticles.

[0126] Thus, a blood kinetics study was carried out on rats by injecting 500 μL of the NP3 (or NP3-PEG) suspension at 100 mg / mL in PLGA or an equivalent quantity of gold of gold nanoparticles "alone (NP of gold) by intravenous route (penile vein) after anesthesia with isoflurane. A blood sample was taken from the tail at various times and then the amount of gold in the samples was measured by atomic absorption spectroscopy.

[0127] The results obtained are represented in FIG. 7.

[0128] Conclusion:

[0129] Encapsulation, whether performed with PLGA or PLGA-PEG, increases the plasma half-life of gold nanoparticles.

The encapsulation process of the invention advantageously allows the encapsulation of gold nanoparticles within particles of reduced size (between 100 and 200 nm) with a yield close to 100% while maintaining a low polydispersity index. The particulate structure thus obtained makes it possible to increase the plasma half-life of gold nanoparticles, and therefore has significant and promising potential for improving the therapeutic effect of said gold nanoparticles.

[0130] The present invention is not limited to the examples described above, only by way of examples, but it encompasses all the variants that a person skilled in the art may envisage in the context of the protection sought.

List of documents cited

Non-patent literature

For convenience, the following non-patent material is cited: (1) JF Hainfeld et al., Phys. Med. Biol., 49 (2004) N309-315;

(2) Gautier Laurent et al, Nanoscale, 8 (2016) 12054-65;

(3) A.M. Gobin et al, Nano Lett., 7 (2007) 1929-1934;

(4) J. F. Hainfeld et al, Br. J. Radiol., 79 (2006) 248-253;

(5) K.T. Butterworth et al, Nanoscale, 4 (2012) 4830-4838;

(6) M. Brust et al, J. Chem. Soc. Chem, Commun., (1995) 0, 1655-1656;

(7) P.C.S. John Turkevich, Discuss Faraday Soc, 11 (n.d.) 55-75;

(8) Thesis by G. Laurent, Synthesis of multifunctional nanoparticles for image-guided radiotherapy. Organic chemistry. University of Franche-Comté, 2014;

(9) T. Butterworth et al., Nanoscale, 2012; 4, 4830-4838;

(10) M. Yu et al., ACS nano, 2015, 9, 6655-6674;

(11) Wang Y et al., Biomed Opt Express, 2016, 7, 4125-4138;

(12) Luque-Michel et al., Nanoscale, 2016, 8, 6495-6506;

(13) H. Fessi et al., International Journal of Pharmaceutics, 1989, 55, R1-R4.

Claims

[Claim 1] Particulate structure characterized in that it comprises: a / a particle of biodegradable polymer,

cl a polycation with a positive charge over a pH range from 5 to 11,

[Claim 2] Particulate structure according to claim 1, characterized in that it comprises a surfactant adsorbed to the surface of the polymer particle a /, said surfactant preferably being polyvinyl alcohol (PVA) and / or a poloxamer.

[Claim 3] Particulate structure according to claim 1 or 2, characterized in that it comprises at least one active principle encapsulated in the polymer particle a /, said active principle preferably being a chemotherapeutic agent and / or a fluorophore.

[Claim 4] Particulate structure according to any one of claims 1 to 3, characterized in that the macrocyclic chelators which cover the gold nanoparticles each comprise:

at least one complexation site of ions of interest and / or radionuclides for medical imaging, said complexation site comprising at least one carboxylic acid function and / or one amine function,

a spacer arm located between the anchoring function and the complexation site (s), optionally a functionalization site allowing the grafting of the chelator with a targeting agent towards cancer cells.

[Claim 5] Particulate structure according to claim 4, characterized in that:

the anchoring function of the macrocyclic chelator is a radical chosen from the group comprising:

, ^* -N- (CH2-CH2-SH) 2, ^* -C (= 0) - (CH2) n-SH with n being an integer ranging from 2 to 5 and mixtures thereof;

the spacer arm of the macrocyclic chelator is a radical chosen from the group comprising:

^* - (CH2) 2-CO-NH- (CH2) 2-NH- ^* , ^* -NH- (CH2-CH2-0) m-CH2-CH2-NH- ^* with m an integer equal to 0, 4 or 1 1, and mixtures thereof;

the site of functionalization of the macrocyclic chelator, if it is present, is a radical, originating from an amino acid, chosen from the group comprising: ^* -NH-CH ((CH2) 4-NH2) -CO- ^* , ^* -NH-CH (CH2-OH) -CO- ^* ,

* -NH-CH (CH-OH-CH3) -CO- ^* , ^* -NH-CH (CH2-C6H4-OH) -CO- ^* ,

* -NH-CH ((CH2) n-NH- ^* ) -CO- ^* with n ranging from 2 to 5, and mixtures thereof.

[Claim 6] Particulate structure according to any one of claims 1 to 5, characterized in that the macrocyclic chelator is chosen from the group comprising:

[Claim 7] Particulate structure according to any one of claims 1 to 6, characterized in that:

the ion of interest for medical imaging, and more particularly magnetic resonance imaging (MRI), is selected from the group comprising Gd3 +, Ho3 +, Dy3 + and their mixtures;

the radionuclide for medical imaging, and more particularly nuclear imaging (TEMP or PET), is chosen from the group comprising ⁶⁴ Cu, ⁸⁹ Zr, ⁸⁸ Ga, ^{11 1} In and their mixtures.

[Claim 8] Particulate structure according to any one of claims 1 to 7, characterized in that the polycation is selected from the group comprising polyethyleneimine (PEI), polylysine, polyarginine, polyamidoamine (PANAM), a poly ( -amino ester), chitosan and mixtures thereof, and is preferably polyethyleneimine.

[Claim 9] Particulate structure according to any one of claims 1 to 8, characterized in that the biodegradable polymer is selected from the group comprising poly (lactic-co-glycolic) acid (PLGA), poly ( lactic) (PLA), poly (glycolic) acid (PGA), polycaprolactone (PCL), a polyanhydride, the copolymers of each of said polymers with polyethylene glycol (PEG) and mixtures thereof, and is preferably poly acid (lactic-co-glycolic) or the copolymer [Poly (lactic-co-glycolic acid) - Polyethylene glycol].

[Claim 10] Particulate structure according to any one of claims 1 to 9, characterized in that the gold nanoparticles b / are coated on their surface with a macrocyclic chelator linked to an active targeting agent for the integrins anbiii overexpressed on the neovessels of tumors, said targeting agent preferably being the cyclic RGD peptide.

[Claim 11] Particulate structure according to any one of claims 1 to 10, characterized in that:

- the hydrodynamic diameter of the polymer particle a / is from 50 to 200 nm, preferably from 70 to 160 nm,

[Claim 12] Particulate structure according to any one of claims 1 to 11, characterized in that the gold nanoparticles b / and optionally the active principle are encapsulated in the polymer particle a /, said gold nanoparticles b / which can also optionally be adsorbed to the surface of the α / polymer particle.

[Claim 13] Particulate structure according to any one of claims 1 to 11, characterized in that the gold nanoparticles b / are adsorbed to the surface of the α / polymer particle, and the active ingredient, if present, is encapsulated in the α / polymer particle.

[Claim 14] A process for preparing a particulate structure according to any one of claims 1 to 12, characterized in that it comprises the following steps:

- Contacting the assembly of gold nanoparticles b / and polycation as defined in the previous step with a mixture of biodegradable polymer and organic solvent miscible with water, said organic solvent optionally being mixed beforehand with at least one active principle, in order to obtain a mixture of nanoparticles of gold b /, of polycation, of biodegradable polymer and optionally of active principle,

- contacting the mixture of gold nanoparticles b /, polycation, polymer and optionally active principle as defined in the previous step, with water, optionally added with a surfactant, in order to precipitate in the form of particles the polymer a / around the gold nanoparticles b / and possibly the active principle,

the encapsulation yield of the gold nanoparticles b / and optionally of the active principle in the polymer particles a / is at least 75%, preferably at least 90%, and more preferably still at least 95 %.

[Claim 15] A method of preparing a particulate structure according to any one of claims 1 to 12, characterized in that it comprises the following steps:

- bringing the polycation assembly into contact with the mixture of biodegradable polymer and organic solvent as defined in the previous step with the aqueous suspension of gold nanoparticles b / in order to obtain a mixture of nanoparticles of gold b /, of polycation, of biodegradable polymer and possibly of active principle,

[Claim 16] A process for preparing a particulate structure according to any one of claims 1 to 11 or 13, characterized in that it comprises the following steps:

- bringing the polymer particles a / into contact at the surface of which the polycation is adsorbed as defined in the previous step with an aqueous suspension of gold nanoparticles b /, in order to lead to the adsorption of the gold nanoparticles b / at the surface of the polymer particles a /,

[Claim 17] Preparation process according to any one of claims 14, 15 or 16, characterized in that: - the aqueous solution of gold nanoparticles b / is at a concentration of 8 to 12 grams of gold nanoparticles per liter of water,

- the mixture of biodegradable polymer with the organic solvent miscible with water, is at a concentration of 10 to 20 grams of polymer per liter of solvent, said organic solvent is chosen from the group comprising dimethylsulfoxide (DMSO), dimethylformamide ( DMF) and N-methyl-pyrrolidone,

- the amount of active ingredient, if present, in the organic solvent is at a concentration of 0.1 to 0.75 grams of active ingredient per liter of solvent,

[Claim 18] A particulate structure according to any one of claims 1 to 13, for use in the treatment of solid cancerous tumors.