Microcapsule loaded with an active substance and comprising a micrometric opening

Abstract

The present invention relates to a microcapsule that is made of bioavailable polymer, is loaded with at least one active substance and comprises at least one micrometric opening. The invention also relates to a method for obtaining said capsule and to said capsule for use in the treatment of a pathology, in particular cancer or myopathy.

Description

MICROCAPSULE LOADED WITH AN ACTIVE SUBSTANCE AND COMPRISING A MICROMETRIC OPENING

[0001] The present invention relates to a microcapsule made of bioassimilable polymer, loaded with at least one active substance, and comprising at least one micrometric opening. The invention also relates to a method for obtaining said capsule, as well as this capsule for its use in the treatment of a pathology, in particular cancer or myopathy.

[0002] Micro or nanoencapsulation is a technique for trapping liquids or solids in an envelope (also called a membrane) that isolates them in order to protect them from the external environment. It is then possible to release their contents into a chosen environment. Their size can vary from a few nanometers to a few hundred microns.

[0003] Depending on the encapsulated molecules and the size of the capsules, it is possible, for example, to offer creams containing fragile molecules (vitamin C, beta carotene, etc.), which will only be released at the time of application, or to vectorize a drug directly to the target cells, thus reducing quantities and costs and consequently undesirable side effects. In the textile industry, this process makes it possible to encapsulate, for example, a persistent perfume or a cosmetic active ingredient for prolonged action on the skin.

[0004] However, the most commonly used technologies are chemical and suffer from several limitations. When the encapsulates are in liquid form, it is very complicated to control the size of the drops. It is also difficult to control the thickness of the encapsulant and therefore the content / container ratio. In addition, the capsules thus obtained traditionally release the encapsulated molecule or composition by bioassimilation of the container. And since the thickness of the encapsulant is difficult to control, the same is true for the release time of said encapsulated molecule or composition. Furthermore, the molecule or composition to be encapsulated is generally in contact during the preparation of the capsules with a liquid or solvent that can denature it.

[0005] When the encapsulation technology is physical, the release of the encapsulated active ingredient is generally carried out by dissolution of the encapsulant or rupture of the capsule. This release is sudden and therefore not continuous, making slow and finely controllable administration of the active ingredient impossible.

[0006] Microcapsules with a bioassimilable shell have now been developed, loaded with at least one active substance, said shell comprising at least one micrometric opening. These capsules allow the release of molecules of interest, for example cytotoxic, over a period of up to several weeks or months depending on the need, followed by a progressive disintegration to finally be metabolized. Localized implantation is easy due to the size of the capsules. The treatment is thus targeted, thus reducing the quantity of the active product required and consequently the cost of the treatment as well as potential side effects. The body of the capsules is metabolized, the implantation can thus be repeated.

[0007] It is also possible to encapsulate fragile molecules and biological species using this method. Compared to chemical encapsulation, the microcapsules of the invention also make it possible to considerably increase the content / container ratio.

[0008] Furthermore, the process of obtaining these microcapsules, by "physical means", is particularly advantageous because it is based on an approach that consists of manufacturing the encapsulant first and filling it subsequently. One of the advantages of this technique lies in the fact that the capsules are possibly always the same size and that the encapsulated material is never in contact with harmful chemistry. This technology makes it possible to isolate and protect active ingredients in a determined quantity until their slow release into the tissues.

[0009] Thus, according to a first aspect, the invention relates to a microcapsule comprising an external envelope consisting of or comprising a bioassimilable polymer, and loaded at its core with at least one active substance, said external envelope comprising at least one micrometric opening.

[0010] According to a particular embodiment, the size (t A ) of the microcapsule is from 80 to 2000 µm, in particular from 80 to 800 µm, in particular from 200 to 800 µm, more particularly from 500 to 800 µm.

[0011] According to a particular embodiment, the size (t A ) of the microcapsule is greater than or equal to 80 µm and less than 2000 µm, in particular from 80 to 1950 µm, in particular from 80 to 1900 µm, more particularly from 80 to 1800, 1700, 1600, 1500, 1400, 1300, 1200, 1100, 1000 or 900 µm.

[0012] According to a particular embodiment, the size (t A) of the microcapsule is from 100 nm to 2000 µm, for example greater than 100 nm and less than 2000 µm, in particular from 200, 300, 400, 500, 600, 700, 800 or 900 nm to 2000 µm.

[0013] According to a particular embodiment, the size (t A ) of the microcapsule is from 100 nm to 1950 µm, in particular from 200, 300, 400, 500, 600, 700, 800 or 900 nm to 1950 µm.

[0014] According to a particular embodiment, the size (t A ) of the microcapsule is from 100 nm to 1500 µm, in particular from 200, 300, 400, 500, 600, 700, 800 or 900 nm to 1500 µm.

[0015] According to a particular embodiment, the size (t A ) of the microcapsule is from 100 nm to 800 µm, in particular from 200, 300, 400, 500, 600, 700, 800 or 900 nm to 800 µm.

[0016] According to a particular embodiment, the size (t A) of the microcapsule is from 1 to 2000 µm, for example greater than 1 and less than 2000 µm, in particular from 5, 10, 20, 30, 40, 50, 60 or 70 to 2000 µm.

[0017] According to a particular embodiment, the size (t A ) of the microcapsule is from 1 to 2000 µm, in particular from 5, 10, 20, 30, 40, 50, 60 or 70 to 1950 µm.

[0018] According to a particular embodiment, the size (t A ) of the microcapsule is from 1 to 2000 µm, in particular from 5, 10, 20, 30, 40, 50, 60 or 70 to 1500 µm.

[0019] According to a particular embodiment, the size (t A ) of the microcapsule is from 1 to 2000 µm, in particular from 5, 10, 20, 30, 40, 50, 60 or 70 to 800 µm. By "size (t A) of the microcapsule”, means in particular, unless otherwise stated, the largest dimension of the microcapsule. One of these references may concern microcapsules having at least partially a cylindrical shape, where the size (t A ) corresponds in particular to the largest dimension of the base of said cylinder.

[0020] According to a particular embodiment, the at least one micrometric opening has a size (t B ) included from 0.0125(t A ) to 0.4(t A ), in particular of 0.1(t A ) to 0.4(t A ).

[0021] According to a particular embodiment, the present invention relates to a microcapsule whose external envelope comprises one or two micrometric openings, in particular one micrometric opening.

[0022] According to a particular embodiment, the external envelope has a thickness of 0.001(t A ) to 0.2(t A), in particular of 0.01(t A ) to 0.15(t A ), more particularly about 0.1(t A ).

[0023] According to a particular embodiment, the present invention relates to a microcapsule having at least partially a cylinder shape, for example with a circular, oval, rectangular, square or star-shaped base, in particular a right circular cylinder or parallelepiped, truncated cylinder, cone, truncated cone, spherical or partially spherical, ellipsoid.

[0024] By "at least partially" is meant in particular that the microcapsule has a cylinder shape, for example with a circular, oval, rectangular, square or star-shaped base, in particular a right circular cylinder or parallelepiped, a truncated cylinder, a cone, a truncated cone, a spherical or partially spherical, or an ellipsoid; or that the microcapsule can be decomposed into a set of sub-volumes of which at least one of these sub-volumes has a cylinder shape, for example with a circular, oval, rectangular, square or star-shaped base, in particular a right circular cylinder or parallelepiped, a truncated cylinder, a cone, a truncated cone, a spherical or partially spherical, or an ellipsoid.

[0025] According to a particular embodiment, the present invention relates to a microcapsule having at least partially a cylinder shape, in particular a right circular cylinder, the largest dimension of the base (t A ) is between 80 and 800 µm.

[0026] According to a more particular embodiment, the present invention relates to a microcapsule having the shape of a cylinder, in particular a right circular cylinder, the largest dimension of which (t A ) of the base is from 250 to 800 µm, in particular from 500 to 800 µm, the external envelope of which comprises at least one micrometric opening, in particular circular, the diameter t of which B is comprised from 100 to 300 µm, in particular from 150 to 250 µm, with (t B ) being included from 0.1(t A ) to 0.4(t A ).

[0027] According to another more particular embodiment, the present invention relates to a microcapsule having a cylinder shape, and the external envelope of which comprises at least one micrometric opening, in particular one micrometric opening, in particular on one of the bases of the cylinder or on the cylindrical surface, or two micrometric openings, in particular on each of the bases of the cylinder, or on the cylindrical surface, the two micrometric openings being for example opposite.

[0028] According to a particular embodiment, the present invention relates to a microcapsule having at least partially a cylindrical shape, the ratio R of its height (h) to the largest dimension of the base (t A ) is from 0.5 to 2, in particular from 0.5 to 1.5, more particularly from 0.5 to 1.

[0029] Such a ratio R is likely in particular to allow the microcapsules of the invention to be easily inserted, in particular in vivo, more particularly at the level of a tumor, for example at a plurality of locations, around and / or in the tumor, and this in a homogeneous manner and / or in different directions.

[0030] According to a particular embodiment, the bioassimilable polymer is selected from the group consisting of poly(lactic acid) (PLA), in particular poly(L-lactic acid) (PLLA) or poly(DL-lactic acid) (PDLLA), poly(glycolic acid) (PGA), poly(ε-caprolactone) (PCL), poly(lactic-co-glycolic acid) (PLGA), poly(ortho ester), polyphosphoester, polyphosphazene, polyanhydride, polyamide, polyester-amide, poly(sebacic acid), polyposphazene, poly(dioxanone), polyurethane, polycarbonate, in particular poly(trimethylene carbonate) (PTMC), poly(propylene carbonate) (PPC), copolyester carbonate (PEC), poly(butylene succinate) (PBS), poly(p-dioxanone) (PPDO), poly(methyl methacrylate) (PMMA), polyhydroxyalkanoate (PHA), polybutylene succinate co-adipate (PBSA), polybutylene adipate co-terephthalate (PBAT), polymethylene adipate co-terephthalate, aliphatic-aromatic copolyester, poly-3-hydroxybutyrate (PHB), poly(hydroxybutyrate-hydroxyvalerate) (PHB / HV),cellulose acetate phthalate, collagen, gelatin, chitosan, chitin, alginate, carrageenan, gums, in particular shellac, guar gum, gum arabic, or gum tragacanth, poly(amino acid), in particular poly(aspartic acid), and copolymers comprising them.,

[0031] According to a more particular embodiment, the bioassimilable polymer is chosen from polylactic acids (PLA), polyglycolic acids (PGA) and polycaprolactones (PCL), and the copolymers comprising them.

[0032] According to a particular embodiment, the active ingredient (or active substance) is in solid form or in liquid form.

[0033] According to a more particular embodiment, the active ingredient (or active substance) is in the form of powder, gel or paste.

[0034] According to an even more particular embodiment, the active principle (or active substance) is in powder form.

[0035] According to a particular embodiment, the active substance is not dissolved in a solvent, for example DMSO (dimethyl sulfoxide).According to a particular embodiment, the active substance has not been dissolved, prior to encapsulation, in a solvent, for example DMSO (dimethyl sulfoxide).

[0036] According to a particular embodiment, the active substance has not been obtained, beforehand or during encapsulation, from a solution containing said active substance, for example by evaporation (in particular under reduced pressure and / or heating), or lyophilization of said solution.

[0037] According to a particular embodiment, the active principle (or active substance) is an enzyme or a drug.

[0038] According to a particular embodiment, the invention relates to a microcapsule, loaded exclusively in its core with at least one active substance.

[0039] By "charged exclusively in its core with at least one active substance" is meant in particular that the core of the microcapsule of the invention is made up of at least one active substance and possibly air and / or inert atmosphere.

[0040] For example, the microcapsule of the invention is devoid, in particular in its core, of a compound which is not the active substance (before encapsulation), for example a polymer, in particular a carrier polymer.

[0041] This active substance may be an active molecule or an active pharmaceutical composition. This active pharmaceutical composition is in particular one of the active pharmaceutical compositions currently or having been on the market.

[0042] According to a particular embodiment, the invention relates to a microcapsule, the loading of which is devoid of any compound not present in the active substance before encapsulation.

[0043] The microcapsules of the invention allow encapsulation of the active substance without it being necessary to first put said active substance into solution. The active substance remains, within the scope of the encapsulation of the invention, pure, unmodified, and therefore undegraded. Indeed, the encapsulation according to the invention can be carried out at room temperature, without dilution or physical or chemical transformation (for example at high or low temperature) of the active substance.

[0044] According to a particular embodiment, the invention relates to a microcapsule, which is capable of releasing said at least one active substance into the body of a patient immediately and over a period of one or more months, for example over a period of approximately 60 days.

[0045] According to another aspect, the present invention also relates to a plurality of microcapsules, which are as defined above.

[0046] According to a particular embodiment, the plurality of microcapsules is uniform in size.

[0047] By "uniform in size" we mean in particular that the size (t A ) of the microcapsules is within ±20, 10, or 5% of the size (t A ) number average of the plurality of microcapsules.

[0048] According to another aspect, the present invention also relates to a method for preparing a microcapsule or a plurality of microcapsules as defined above, which comprises the following steps:

[0049] (i) The provision of a sacrificial mold having at least one cavity;

[0050] (ii) Covering the wall(s) of the at least one cavity of said mold with a structurable composition comprising a bioassimilable polymer;

[0051] (iii) Drying or annealing the structurable composition as obtained at the end of step (ii) to obtain a mold of which the wall(s) of the at least one cavity are covered by the hardened bioassimilable polymer;

[0052] (iv) Filling the at least one cavity as obtained at the end of step (iii) with at least one active substance;

[0053] (v) sealing the open cavity as obtained at the end of step (iv) by applying a layer of bioassimilable polymer to this opening of the mold;

[0054] (vi) removing the mold to obtain at least one microcapsule sealed by said layer of bioassimilable polymer as obtained at the end of step (v);

[0055] (vii) separating the at least one sealed microcapsule as obtained at the end of step (vi) from the remainder of the layer of bioassimilable polymer;

[0056] (viii) perforation of the at least one sealed microcapsule as obtained at the end of step (vii);

[0057] steps (vii) and (viii) may be interchanged.

[0058] According to a particular embodiment, the sacrificial mold is made of or comprises a water-soluble material, in particular a water-soluble polymer, in particular a polymer chosen from poly(vinyl alcohol) (PVOH or PVAL), poly(vinylacetate) (PVA), polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), polyacrylamide, dextrin, casein, dextran, pullulan, cellulose ethers.

[0059] According to a particular embodiment, the sacrificial mold has a plurality of cavities, in particular a plurality of identical cavities.

[0060] According to a particular embodiment, the at least one cavity of the sacrificial mold is formed by the action of a laser, in particular a CO2 laser, or by molding.

[0061] According to a particular embodiment, the structurable composition comprising a bioassimilable polymer of step (ii) is a solution of said polymer in an organic solvent, the organic solvent being for example an aromatic solvent.

[0062] By "aromatic solvent" is meant in particular benzene, or a solvent consisting of or comprising an aromatic ring, in particular benzene, substituted, in particular by alkyl groups, for example C1-C3, and / or alkoxy groups, for example C1-C3.

[0063] According to a more particular embodiment, the polymer concentration in the organic solvent is from 10 to 200 g / L, in particular from approximately 20 to approximately 100 g / L.

[0064] According to a particular embodiment, step (ii) is repeated, in particular once.

[0065] According to a more particular embodiment, the polymer concentration in the organic solvent is approximately 100 g / L, step (ii) being repeated, in particular once.

[0066] According to another more particular embodiment, step (ii) is repeated two or more times, the first covering being done with a structurable composition comprising a bioassimilable polymer at approximately 20 g / L, the other coverings being done with a structurable composition comprising a bioassimilable polymer at approximately 100 g / L.

[0067] According to a particular embodiment, the coating of step (ii) is carried out by spin coating, spraying, dipping, nebulization, flexography, screen printing, inkjet, gravure printing, or coating using a slot die.

[0068] According to a particular embodiment, the drying or annealing of the structurable composition of step (iii) is an annealing carried out at a temperature of from 50 to 100°C, in particular of approximately 80°C, and / or for a duration of from 5 minutes to 5 hours, in particular of approximately 30 minutes.

[0069] According to a particular embodiment, the filling of step (iv) is carried out mechanically.

[0070] According to a particular embodiment, the layer of bioassimilable polymer of step (v) is obtained by concentrating a solution of said polymer in an organic solvent, the organic solvent being for example an aromatic solvent.

[0071] According to a particular embodiment, the concentration is carried out by heating, in particular with stirring, and in particular in a polytetrafluoroethylene container.

[0072] According to a particular embodiment, the sealing of step (v) is carried out under pressure, in particular under the pressure of an inflatable membrane, in particular made of rubber. Said pressure is for example equivalent to a weight of approximately 10 kg.

[0073] According to a particular embodiment, the sealing of step (v) is carried out for a period of 1 to 24 hours, for example 6 to 12 hours, in particular at a temperature of 15 to 100°C, in particular 20 to 25°C.

[0074] According to a particular embodiment, step (v) is preceded by a step of preparing said layer of bioassimilable polymer by bringing this layer into contact with a solution of said polymer in an organic solvent.

[0075] According to a particular embodiment, the sacrificial mold is made of or comprises a water-soluble material, in particular a water-soluble polymer, and the removal of the mold from step (vi) is carried out by bringing said mold into contact with water, in particular for a period of 30 minutes to 12 hours, more particularly for approximately 4 hours.

[0076] According to a particular embodiment, contact with water is made using a flow of water, in particular at a flow rate of 0.1 to 20 L / min, in particular 1 to 10 L / min, for example approximately 6 L / min, in particular at a temperature of 20 to 25°C.

[0077] According to a particular embodiment, the separation of the at least one sealed microcapsule from step (vii) is carried out using a punch or a coaxial needle.

[0078] According to a particular embodiment, the perforation of the at least one sealed microcapsule of step (viii) is done mechanically, in particular using at least one tip, using a laser, or using ultrasound, preferably mechanically, more preferably using a tip.

[0079] According to another aspect, the invention also relates to a microcapsule or a plurality of microcapsules as defined above, for its use in the treatment and / or prevention of a disease, said disease being in particular a cancer, a myopathy or a dermatological disease.

[0080] According to a particular embodiment, the disease is a cancer. This concerns in particular:tumors which are not operable, that is to say in particular which cannot be removed from the body with simple surgery,tumors which are very difficult to access (but nevertheless accessible for the microcapsule(s) of the invention, for example using a needle through which said microcapsule(s) can be introduced), and / ortumors which are sensitive, in particular exclusively, to very toxic substances by systemic route. The treatment of the latter therefore requires a local and preferably long-term application, an application which may be mediated by the microcapsule(s) of the present invention. DEFINITIONS

[0081] As used herein, the term "about" refers to a range of values ​​within ± 10% of a specific value. For example, the term "about 20" includes values ​​of 20 ± 10%, or values ​​from 18 to 22.

[0082] For the purposes of this description, percentages refer to percentages by mass relative to the total mass of the formulation, unless otherwise indicated.

[0083] As used herein, the value ranges of "xy" or "from x to y" or "between x and y" include the bounds x and y as well as the integers between these bounds. For example, "1-5", or "from 1 to 5" or "between 1 and 5" denote the integers 1, 2, 3, 4 and 5. Preferred embodiments include each individual integer in the value range, as well as any subcombination of these integers. For example, preferred values ​​for "1-5" may include the integers 1, 2, 3, 4, 5, 1-2, 1-3, 1-4, 1-5, 2-3, 2-4, 2-5, etc. FIGURES

[0084] Lamontre the diffusion of fluorescein contained in a microcapsule of the invention within a mouse tumor, the tumor having been cut in two to show the location of the capsule (A) and the diffusion of fluorescein inside the tumor (A and B).

[0085] Corresponds to the observation by fluorescence microscopy through the skin of a capsule according to example 4.1. 1: diffusion of doxorubicin; 2: capsule; 3: tissues / skin.

[0086] Corresponds to the observation by fluorescence microscopy of a capsule according to example 4.1, after the skin covering the capsule has been incised.

[0087] Corresponds to the observation of a PLA capsule containing Doxoribicin and having a perforation of 302 µm in diameter. EXAMPLES

[0088] Example 1: Preparation of microcapsules of the invention

[0089] Microcapsules of the invention were obtained as follows:A sacrificial PVA mold comprising a plurality of cylindrical cavities 800 µm deep and 800 µm in diameter, which were formed in a 1.2 mm thick PVA layer by CO2 laser or molding, was manufactured;Two solutions of PLA in an aromatic solvent, one at 20 g / L and the other at 100 g / L, were prepared by dissolving the PLA in the solvent at 50°C using ultrasound;The walls of the cavities of said mold were covered by spin-coating the 20 g / L PLA solution, then the 100 g / L solution, this last step being repeated;The mold thus covered was annealed at 80°C for 30 minutes;The cavities were filled with an active substance in powder form by mechanical means;A closing PLA layer was prepared by concentrating a PLA solution in an aromatic solvent under heating and stirring in a Teflon beaker; said layer is a film obtained on the surface of the beaker; The surface of this layer is treated with the solution remaining in the beaker after removal of the film; the sealing of the cavities is carried out by plating the PLA layer on the mold, the plating being done using an inflated (rubber) membrane, overnight at room temperature; the PVA mold is then dissolved by a flow of water for 4 hours, the water being at a temperature of 20 to 25 ° C; the mechanical perforation of the microcapsules thus obtained using a tip, viewed by an XYZ camera mounted on a microscope and controlled by a computer; the isolation of the microcapsules obtained is carried out using a punch.

[0090] PUR (polyurethane) capsules were obtained in a similar way.

[0091] The experimental protocol for PUR may, however, differ in the annealing and drying times of the layers on the PVA. Furthermore, the surface modification of the plating closure film is generally carried out with the initial PUR solution.

[0092] Example 2: Study of the release of an active ingredient contained in the microcapsules of the invention

[0093] The release of encapsulated methylene blue (polyurethane, see example 1) was studied in an aqueous medium. This study showed that the release was stable and continuous over several hours to several weeks depending on the openings and was confirmed by UV spectroscopy measurements.

[0094] Thus, the thickness of the capsule walls and the size of the perforation can be chosen so that the diffusion of the active ingredient is present over the chosen period and the metabolization of the capsule only occurs subsequently.

[0095] Example 3: Another study of the release of an active ingredient contained in the microcapsules of the invention

[0096] To verify diffusion in tumor tissues, 800 μm diameter polyurethane capsules, as described in Example 1, containing fluorescein, were implanted into mouse tumors to verify diffusion of the latter into the tumor. Fluorescein is a fluorescent dye that is easily detectable by fluorescent emission in the green.

[0097] Implantation was performed using a trocar or simply by placing the capsule at the end of a needle. Implantation of one microcapsule per tumor was performed in a subcutaneous tumor model in an immunocompetent mouse (LPB fibrosarcomas implanted subcutaneously in C57Bl / 6 mice).

[0098] Once implanted, the capsule diffused fluorescein within the tumor for 24 hours.

[0099] Tumor ablation and observation showed significant and continued diffusion as described in. However, the microcapsules were not empty after 24 hours: a significant amount of fluorescein still remained, showing that the release of microcapsule contents can continue well beyond 24 hours.

[0100] Example 4: Microcapsules of the invention for their use in chemotherapy 1. Evaluation of the toxicity of microcapsules:

[0101] A capsule of the invention, obtained according to Example 1, and containing doxorubicin, was injected subcutaneously into the right flank of 4 mice (one capsule per mouse).

[0102] The mice were then examined at the time of injection and then twice a day for two days, to detect any symptoms and / or significant weight loss.

[0103] No significant weight loss was observed, nor were there any notable adverse effects.

[0104] The mice were then autopsied. The capsules were first observed under fluorescence microscopy through the skin. It was evident that all the capsules had diffused into the surrounding tissue, as a luminous halo was observed around the four capsules (). The skin covering the capsules was then incised. The 4 capsules were found in good condition, with a significant amount of doxorubicin still inside, as observed, again under fluorescence microscopy (). 2. Injection into an animal bearing tumors:

[0105] A capsule of the invention, obtained according to Example 1, and containing doxorubicin, was injected into a mouse bearing two tumors, one on the left flank, the other on the right flank (one capsule in each tumor).

[0106] The left tumor was cut in two 5 days after injection of the capsules. A diffusion of doxorubicin is clearly visible, very localized around the capsule, within the tumor. The same is true for the right tumor.

[0107] Thus, doxorubicin diffuses into tumors, and is thus capable of constituting an effective and localized treatment in chemotherapy using the devices of the present invention.

Claims

Microcapsule comprising an outer envelope made of or comprising a bioassimilable polymer, and loaded in its core with at least one active substance, said outer envelope comprising at least one micrometric opening. Microcapsule according to claim 1, wherein: the size (t A ) is greater than or equal to 100 nm and less than 2000 µm; and / or at least one micrometer aperture has a size (t B ) including 0.0125(t A ) at 0.4(t A ) ; and / or the outer envelope has a thickness of 0.001(t A ) at 0.2(t A ). A microcapsule according to any one of the preceding claims, wherein the bioavailable polymer is selected from the group consisting of poly(lactic acid) (PLA), in particular poly(L-lactic acid) (PLLA) or poly(DL-lactic acid) (PDLLA), poly(glycolic acid) (PGA), poly(ε-caprolactone) (PCL), poly(lactic-co-glycolic acid) (PLGA), poly(ortho ester), polyphosphoester, polyphosphazene, polyanhydride, polyamide, polyester-amide, poly(sebatic acid), polyposphazene, poly(dioxanone), polyurethane, polycarbonate, in particular poly(trimethylene carbonate) (PTMC), poly(propylene carbonate) (PPC), copolyester carbonate (PEC), poly(butylene succinate) (PBS), poly(p-dioxanone) (PPDO), poly(methyl methacrylate) (PMMA), polyhydroxyalkanoate (PHA), and polybutylene succinate. co-adipate (PBSA), polybutylene adipate co-terephthalate (PBAT), polymethylene adipate co-terephthalate, aliphatic-aromatic copolyester, poly-3-hydroxybutyrate (PHB),poly(hydroxybutyrate-hydroxyvalerate) (PHB / HV), cellulose acetate phthalate, collagen, gelatin, chitosan, chitin, alginate, carrageenan, gums, in particular shellac, guar gum, gum arabic, or tragacanth gum, poly(amino acid), in particular poly(aspartic acid), and copolymers comprising them. Microcapsule according to any one of the preceding claims, wherein the active substance: is not dissolved in a solvent or has not been dissolved, prior to encapsulation, in a solvent; is in solid form, in particular in the form of a powder, gel or paste, or in liquid form, the active substance being in particular in powder form; and / or an enzyme or a drug. A method for preparing a microcapsule according to any one of the preceding claims, comprising the following steps: (i) Providing a sacrificial mold having at least one cavity; (ii) Coating the wall(s) of the at least one cavity of said mold with a structuring composition comprising a bio-assimilable polymer; (iii) Drying or annealing the structuring composition as obtained at the end of step (ii) to obtain a mold in which the wall(s) of the at least one cavity are coated with the hardened bio-assimilable polymer; (iv) Filling the at least one cavity as obtained at the end of step (iii) with at least one active substance; (v) Sealing the open cavity as obtained at the end of step (iv) by applying a layer of bio-assimilable polymer to this mold opening;(vi) the removal of the mold to obtain at least one microcapsule sealed by said bioassimilable polymer layer as obtained at the end of step (v); (vii) the separation of the at least one sealed microcapsule as obtained at the end of step (vi) from the remainder of the bioassimilable polymer layer; (viii) the perforation of the at least one sealed microcapsule as obtained at the end of step (vii); steps (vii) and (viii) may be interchanged. A method according to claim 5, wherein the sacrificial mold is made of or comprises a water-soluble material, in particular a water-soluble polymer, especially a polymer selected from poly(vinyl alcohol) (PVOH or PVAL), poly(vinyl acetate) (PVA), polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), polyacrylamide, dextrin, casein, dextran, pullulan, cellulose ethers. A process according to any one of claims 5 to 6, wherein the structuring composition comprising a bioassimilable polymer of step (ii) is a solution of said polymer in an organic solvent, the organic solvent being, for example, an aromatic solvent. A process according to any one of claims 5 to 7, wherein the bioassimilable polymer layer of step (v) is obtained by concentrating a solution of said polymer in an organic solvent, the organic solvent being, for example, an aromatic solvent. A method according to any one of claims 5 to 8, wherein step (v) is preceded by a step of preparing said bioassimilable polymer layer by contacting said layer with a solution of said polymer in an organic solvent. A method according to any one of claims 5 to 9, wherein the separation of at least one sealed microcapsule from step (vii) is carried out using a coaxial punch or needle. A method according to any one of claims 5 to 10, wherein the perforation of at least one sealed microcapsule of step (viii) is done mechanically, in particular using at least one tip, using a laser, or using ultrasound, preferably mechanically, more preferably using a tip. Microcapsule according to any one of claims 1 to 4, for its use in the treatment and / or prevention of a disease, said disease being in particular cancer, myopathy or dermatological disease.

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