FR2817478A1 - Aqueous suspension of nanospheres useful in cosmetic compositions, comprises an amorphous lipophilic active ingredient stabilized with a surfactant - Google Patents

Abstract

Aqueous nanosphere suspension comprises nanospheres consisting of: (1) an amorphous lipophilic active ingredient (I) selected from dehydroepiandrosterone and its precursors and derivatives, pentacyclic triterpene acids, hydroxystilbenes, isoflavonoids and aminophenol derivatives; and (2) a surfactant (II). Aqueous nanosphere suspension comprises nanospheres with an average size of 10-1000 nm consisting of: (1) an amorphous lipophilic active ingredient (I) selected from dehydroepiandrosterone (DHEA) and its precursors and derivatives (other than cholesterol, plant sterols and their esters), pentacyclic triterpene acids, hydroxystilbenes, isoflavonoids and aminophenol derivatives of formula (III); and (2) a surfactant (II) capable, at its critical micelle concentration (cmc), of reducing the interfacial tension of a hexane/water system from 51 mN/m - 12 mN/m or less and/or reducing the surface tension of water to 50 mN/m or less. R = CONR1R2, COOR3 or SO2R3; R1 = H or (un)saturated 1-6C alkyl optionally substituted by OH; R2 = H or (un)saturated 12-30C alkyl or (poly)cycloalkyl optionally substituted by OH; and R3 = (un)saturated 12-30C alkyl or (poly)cycloalkyl optionally substituted by OH. Independent claims are also included for the following: (1) a process for producing the suspension, comprises: (i) dissolving (I) in a volatile water-miscible solvent at a concentration of 0.1-30 wt.%; (ii) stirring the solution into an aqueous phase, where the solution and/or the aqueous phase contains (II) at a concentration at least equal to its cmc; and (iii) evaporating the solvent and optionally part of the water; (2) a process for producing the suspension, comprises: (i) dissolving (I) in a volatile water-miscible solvent at a concentration of 0.1-30 wt.%; (ii) emulsifying the solution with an aqueous phase, where the solution and/or the aqueous phase contains (II) at a concentration at least equal to its cmc; and (iii) evaporating the solvent and optionally part of the water.

Description

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Aqueous suspensions of nanospheres of lipophilic active ingredients
The present invention relates to aqueous suspensions of nanospheres of lipophilic active principles, in a stable amorphous form, as well as to processes for the preparation of such suspensions and to cosmetic compositions containing them.

 There are many cosmetic active ingredients which, due to their highly lipophilic nature, are insoluble in most cosmetically acceptable solvents.

 An interesting approach to solving this insolubility problem consists in forming with these lipophilic molecules solid particles of very small size (less than one micron), called nanoparticles, which can then be used in the form of colloidal suspensions.

 Among the nanoparticles, a distinction is made between nanocapsules and nanospheres.

 Nanocapsules are particles with a core-shell structure. The internal phase containing the active principle in dissolved, dispersed or pure form is encapsulated in a continuous, solid envelope, insoluble in the medium, and which is generally of polymeric or waxy nature. Nanocapsules containing biologically active lipophilic molecules are described for example in patent applications EP-A 0 007 895, EP-A 0 064 967, EP-A-0 447 318 and WO 96/14830, and patent applications EP 780,115, EP 1,025,901, EP 1,029,587 and EP 1,025,898.

 Nanospheres are solid spheres containing the active ingredient generally incorporated in a waxy matrix. A certain number of documents describe nanospheres containing biologically active lipophilic active principles (see for example EP-A-0 446 094, EP-A-0 394 078, EP-A-0 847 747, EP-A-0 605 497 , WO 96/14830, US 5, 885,486, FR 2775441 and US 5,250, 236). All the nanospheres described in these documents are based on a wax, the proportion of which is never less than 50%.

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 The presence of a large fraction of waxes, polymers or other substances forming the matrix, the envelope or the core of the nanoparticles of the prior art limits the concentration of active principle of the suspensions obtained. To obtain high concentrations of biologically active molecules, it is therefore desirable to have nanoparticles almost exclusively made up of active principle.

 US patent 5,902,606 (Alfatec Pharma GmbH) describes nanospheres consisting exclusively of active ingredient. The main drawback of this technology lies in the fact that the nanoparticle suspensions described are stabilized by proteins constituted by hydrophilic peptides such as collagen or gelatin. However, proteins can be the cause of sensitization problems (allergies) and their use in cosmetic compositions is therefore undesirable.

 Other publications such as the articles by Sjônstrôm et al. (J.

Dispersion Science and Technology, 15 (1), 89-117,1994 and Pharmaceutical Research, 12 (1) 39-48,1995) describe the preparation of aqueous suspensions of nanospheres based on cholesterol acetate stabilized by a lecithin / mixture bile salt or with polyethoxylated sorbitan mono-oleate at 20 EO (tweens 80). However, such suspensions are only stable at low concentration of active ingredient. In addition, the use of bile salts in cosmetics should be avoided for reasons of safety.

 The Applicant has therefore sought to formulate lipophilic active principles, biologically active, in the form of stable aqueous suspensions of nanoparticles containing high fractions of active principle, having dimensions less than one micron.

 The Applicant has discovered that it was possible to obtain such suspensions of liposoluble active principle nanospheres in a stable amorphous form by combining with the lipophilic active principle at least one surfactant capable of inhibiting the crystallization of the latter.

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 The aqueous suspensions thus obtained can contain relatively large fractions of active principle because the nanospheres are free of polymeric or waxy matrix insoluble in water. In the absence of crystallization phenomena, the suspensions - even when they contain high concentrations of active ingredient - remain stable, that is to say the active ingredient remains in amorphous form and the nanospheres retain their spherical shape and their small initial size.

 The subject of the present invention is therefore aqueous suspensions of nanospheres of lipophilic active principles, having an average particle size of 10 nm to 1 μm, containing, in a physiologically acceptable aqueous medium, nanospheres consisting essentially (A) of at least one lipophilic active principle, in amorphous form, chosen from those indicated below and (B) of at least one water-soluble or liposoluble surfactant inhibiting the crystallization of the lipophilic active principle (A), the characteristics of which will be defined below after.

 The present invention also relates to two different processes for the preparation of aqueous suspensions of nanoparticles of lipophilic active ingredients which will be described in more detail below, as well as cosmetic compositions containing these aqueous suspensions of nanospheres of lipophilic active ingredients.

 As indicated above, the small average particle size is essential for the good bioavailability of the lipophilic active principles. According to the present invention, particular preference is given to nanospheres having an average size of between 50 and 500 nm.

 The active ingredients used according to the invention have a melting point above 100 C, a solubility in water at room temperature (25OC) of less than 0.01%, and a solubility of less than 7.5% in the alcohols of Guerbet such as octyldodecanol, and glycols, such as, for example, glycerin, polyethylene glycols or isoprene glycol.

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Elle est connue pour ses propriétés anti-âge liées à sa capacité à promouvoir la kératinisation de l'épiderme (JP-07 196 467) et à lutter contre l'ostéoporose (US 5,824, 671), ou encore dans le traitement des peaux sèches, en raison de son aptitude à augmenter la production endogène et la sécrétion de sébum et à renforcer l'effet barrière de la peau (UQ 4,496, 556). Il a en outre été proposé d'utiliser le sulfate de DHEA contre l'alopécie (JP-60 142 908) et pour traiter différents signes du vieillissement tels que les rides, la perte d'éclat de la peau et le relâchement cutané (EP-0 723 775). According to the present invention, the lipophilic active principles are formulated in the form of nanospheres in suspension in an aqueous medium and are chosen from: (1) dehydroepiandrosterone (DHEA) and its chemical and biological precursors and derivatives, with the exception of cholesterol and its esters and plant sterols such as phytosterols and sitosterols, and their esters; dehydroepiandrosterone is a natural steroid, produced mainly by the adrenal cortex, corresponding to the formula

It is known for its anti-aging properties linked to its ability to promote keratinization of the epidermis (JP-07 196 467) and to fight against osteoporosis (US 5,824, 671), or even in the treatment of dry skin. , due to its ability to increase endogenous production and sebum secretion and to reinforce the barrier effect of the skin (UQ 4,496, 556). It has also been proposed to use DHEA sulfate against alopecia (JP-60 142 908) and to treat various signs of aging such as wrinkles, loss of radiance of the skin and sagging skin (EP -0 723 775).

The DHEA which can be used according to the invention is for example available from the companies SIGMA and AKZO NOBEL.

By precursor of DHEA is meant its immediate biological precursors as well as its chemical precursors. Examples of biological precursors are pregnenolone, 17 (x-hydroxypregnenolone, 5-androstenediol, 17cl-hydroxypregnenolone sulfate and 5-androstenediol sulfate. Examples of

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précurseurs biologiques sont la prégnénolone, la 17ahydroxyprégnénolone, le 5-androstènediol, le sulfate de 17cl- hydroxyprégnénolone et le sulfate de 5-androstènediol. Des exemples de précurseurs chimiques sont les sapogénines telles que la diosgénine (spirost-5-èn-3-beta-ol), l'hécogénine, la smilagénine et la sarsapogénine, ainsi que des extraits naturels en contenant, en particulier le fénugrec et les extraits de Dioscorées telles que la racine d'igname sauvage ou Wild Yam.

biological precursors are pregnenolone, 17ahydroxyprégnénolone, 5-androstènediol, 17cl-hydroxyprégnénolone sulfate and 5-androstènediol sulfate. Examples of chemical precursors are sapogenins such as diosgenin (spirost-5-en-3-beta-ol), hecogenin, smilagenin and sarsapogenin, as well as natural extracts containing them, in particular fenugreek and Dioscorea extracts such as wild yam root or Wild Yam.

notamment la 7a-hydroxy-DHEA, la 7-céto-DHEA, le 5-androstène-3ss- 17ss-diol (ou adiol), le sulfate de 5-androstène-3ss-17ss-diol et la 4- androstène-3,17-dione, sans que cette liste soit limitative. Comme dérivés chimiques, on peut citer notamment les sels, en particulier les sels hydrosolubles tels que le sulfate de DHEA, les esters tels que les esters d'acides hydroxycarboxyliques et de DHEA décrits dans US 5,736, 537 ou les autres esters tels que le salicylate, l'acétate, le valérate et l'énanthate de
DHEA ; (2) les acides triterpène pentacycliques tels que l'acide ursolique et l'acide oléanolique. Ils sont présents dans les plantes telles que le romarin. Ils sont fréquemment utilisés dans les compositions pharmaceutiques pour leurs nombreuses propriétés thérapeutiques, et notamment pour leurs propriétés anti-inflammatoires, hépatoprotectrices, diurétiques, analgésiques, antimicrobiennes, inhibitrices de certaines activités enzymatiques et anti- tumorales. Dans le domaine cosmétique l'acide ursolique est décrit par exemple comme constituant d'une composition anti-transpirante (FRA2541 895) et comme inhibiteur de l'activité de la tyrosinase, enzyme clé de la synthèse mélanique (JP-58/57307). The term DHEA derivatives is understood to mean both its metabolic derivatives and its chemical derivatives. As metabolic derivatives, there may be mentioned

in particular 7a-hydroxy-DHEA, 7-keto-DHEA, 5-androstene-3ss-17ss-diol (or adiol), 5-androstene-3ss-17ss-17ss-diol sulfate and 4-androstene-3, 17-dione, without this list being exhaustive. As chemical derivatives, mention may in particular be made of the salts, in particular the water-soluble salts such as DHEA sulfate, the esters such as the esters of hydroxycarboxylic acids and of DHEA described in US Pat. No. 5,736,537 or the other esters such as the salicylate , acetate, valerate and enanthate
DHEA; (2) pentacyclic triterpene acids such as ursolic acid and oleanolic acid. They are present in plants such as rosemary. They are frequently used in pharmaceutical compositions for their numerous therapeutic properties, and in particular for their anti-inflammatory, hepatoprotective, diuretic, analgesic, antimicrobial, inhibitory properties for certain enzymatic and anti-tumor activities. In the cosmetic field, ursolic acid is described, for example, as a constituent of an antiperspirant composition (FRA2541 895) and as an inhibitor of the activity of tyrosinase, a key enzyme in melanin synthesis (JP-58/57307).

(3) hydroxystilbenes, which are compounds corresponding to the general formula:

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dans laquelle n est un nombre entier compris entre 1 et 4 inclusivement et m est un nombre entier compris entre 1 et 5 inclusivement. Cette formule englobe les composés cis et trans. Selon la présente invention, le terme hydroxystilbène recouvre également les dérivés hydroxyalkylés des composés de formule (II).

in which n is an integer between 1 and 4 inclusive and m is an integer between 1 and 5 inclusive. This formula includes the cis and trans compounds. According to the present invention, the term hydroxystilbene also covers the hydroxyalkylated derivatives of the compounds of formula (II).

Hydroxystilbenes are compounds that are found naturally in plants of the spermatophyte class and in particular in the vine. In the cosmetic field, hydroxystilbenes are used, among others, as depigmenting agents (JP-87-192040) or anti-aging agents (FR-2 777 186).

Among the hydroxystilbenes, there may be mentioned mono-, di-, tri-, tetra-, pentahexa-, hepta-, octo- and nonahydroxystilbènes, or their hydroxyalkylated derivatives.

According to the invention, the hydroxystilbenes can be used alone or in mixtures of any kind and can be of natural or synthetic origin.

The hydroxystilbenes which can be used according to the invention are chosen from: 4'-hydroxystilbene, 2 ', 4'-dihydroxystilbene, 3', 4'-dihydroxystilbene, 4,4'-dihydroxystilbene, 2 ', 4', 4-trihydroxystilbene, 3 ', 4', 4-trihydroxystilbene, 2,4, 4'-trihydroxystilbene, 3,4, 4'-trihydroxystilbene, 3,5, 4'-trihydroxystilbene, 2 ', 3 , 4-trihydroxystilbene, 2,3 ', 4-trihydroxystilbene, 2', 2,4'-trihydroxystilbene,

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 2, 4, 4 ', 5'-tetrahydroxystilbene, 2', 3, 4 ', 5-tetrahydroxystilbene, 2, 2', 4,4'-tetrahydroxystilbene, 3.3 ', 4', 5- tetrahydroxystilbene, 2,3 ', 4,4'-tetrahydroxystilbene, 3.3', 4,4'-tetrahydroxystilbene, 3,3 ', 4', 5,5'-pentahydroxystilbene, 2, 2 ', 4,4 ', 6-pentahydroxystilbène, le 2, 3', 4,4 ', 6-pentahydroxystilbène, le 2, 2', 4,4 ', 6,6'-hexahydroxystilbène.

Among these compounds, resveratrol (3,5,4'-trihydroxystilbene) is particularly preferred because it is naturally present in the skin of grapes and in wine. In this regard, one can consult the review of Soleas et al., (Clinical Biochemistry, vol. 30, no 2, pages
91-113.1997) which perfectly summarizes the state of knowledge concerning this compound and the hydroxystilbenes.

(4) isoflavonoids, a subclass of flavonoids, which are formed from a more or less oxidized 3-phenylchroman skeleton and which can carry different substituents. The term isoflavonoid groups together several classes of compounds among which mention may be made of isoflavones, isoflavanones, rotenoids, pterocarpans, isoflavans, isoflavane-3-enes, 3-arylcoumarins, 3-aryl-4-hydroxycoumarins, coumestanes, coumaronochromones, or 2-arylbenzofurans. A complete review of isoflavonoids, their sources and methods of analysis was published in The Flavonoids, Harbone editor (1988), chapter 5 titled Isoflavonoids by P. M. Dewick, pages 125-157.

 The isoflavonoids used according to the invention have a solubility in water at room temperature (25OC) of less than 0.01% and can be of natural origin, that is to say extracted from an element of natural origin , most often a plant, or have been obtained by chemical synthesis. Isoflavonoids of natural origin are preferred.

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 Examples of isoflavonoids of natural origin that may be cited are genistin.

 A preferred subclass of isoflavonoids is that of isoflavones encompassing both the aglycone forms (daidzein, genistein, glyciteine and the glycosylated forms (daidzine, genistin, glycitin).

Methods for the preparation of isoflavones are especially described in patents and patent applications WO 95/10530, WO 95/10512, US 5,679
806, US 5,554,519, EP 812,837 and WO 97/26269.

 Isoflavones are known in particular as antioxidant agents, for their anti-radical and depigmenting properties, as well as for their capacity to inhibit the activity of the sebaceous glands (DE-44 32 947). They have also been described as agents capable of preventing the signs of aging of the skin (JP 1-961 06).

dans laquelle R est un radical correspondant à l'une des formules (i), (ii) ou (iii) suivantes (i)-CO-NRIR2 (ii)-CO-O-R3 (iii)-SO2-R3 où RI représente un atome d'hydrogène ou un radical alkyle en CI-6, linéaire ou ramifié, saturé ou insaturé, éventuellement hydroxylé, R2 représente un atome d'hydrogène ou un radical choisi parmi les radicaux alkyle, saturés ou insaturés, linéaires, cycliques ou ramifiés, en Cl2 à C30, éventuellement hydroxylés, et (5) the aminophenol derivatives of formula

in which R is a radical corresponding to one of the following formulas (i), (ii) or (iii) (i) -CO-NRIR2 (ii) -CO-O-R3 (iii) -SO2-R3 where RI represents a hydrogen atom or a C1-6 alkyl radical, linear or branched, saturated or unsaturated, optionally hydroxylated, R2 represents a hydrogen atom or a radical chosen from alkyl radicals, saturated or unsaturated, linear, cyclic or branched, in Cl2 to C30, optionally hydroxylated, and

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R3 représente un radical choisi parmi les radicaux alkyle en Cl2 à C30, saturés ou insaturés, linéaires, ramifiés ou cycliques, y compris polycycliques condensés, et éventuellement hydroxylés.

R3 represents a radical chosen from C1 to C30 alkyl radicals, saturated or unsaturated, linear, branched or cyclic, including condensed polycyclics, and optionally hydroxylated.

 As examples of preferred active principles according to the present invention, mention may be made of dehydroepiandrosterone (DHEA), DHEA sulfate, 7a-hydroxy-DHEA, 7-keto-DHEA, prednisolone, prednisone, progesterone, pregnenolone, testosterone, diosgenin, hecogenin, ursolic acid, oleanolic acid, resveratrol (= 3.5, 4'trihydroxystilbene) and N-cholesteryloxycarbonyl-4-aminophenol, isoflavonoids including solubility in water at room temperature (25 C) is less than 0.01%.

 The content of lipophilic active ingredient in the aqueous nanosphere suspensions of the present invention is between 0.2 and 50% by weight, and preferably between 1 and 20% by weight, relative to the total weight of the aqueous suspension of nanospheres.

 According to the present invention, the lipophilic active principles listed above are associated with one or more water-soluble or liposoluble surface-active agents inhibiting their crystallization, capable, at their critical micellar concentration (CMC), of lowering the interfacial tension of the hexane system / water of 51 mN / m to a value less than or equal to 12 mN / m and / or to lower the surface tension of the water to a value less than or equal to 50 mN / m.

 The role of the surfactants used in the invention is to stabilize the amorphous form of the active principle by preventing its crystallization.

 The term “stable amorphous form” of the active principle according to the present invention means an aqueous suspension of nanospheres which, after 7 days of storage at a temperature between 4 and 45 ° C., shows no sign of evolution visible under the microscope ( cross polarization, contrast

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 phase) at a magnification adapted to the size of the particles, and in particular no sign of recrystallization of the active principle.

dans laquelle Ra, Rb et R représentent chacun indépendamment un radical alkyle en CI-6 ou un radical- (CH2) x- (O-CH2CH2) y- The surfactants capable of preventing the crystallization of the active principles indicated above are chosen in particular from (a) natural or synthetic phospholipids, hydrogenated or not, enriched or not with phosphatidylcholine. By way of example, mention may be made of soy lecithin enriched with 45% by weight of phosphatidylcholine (marketed under the name Emulmetiko 900 by the company
LUCAS MEYER) or a hydrogenated soy lecithin (marketed under the name Lécinolo S10 by the company NIKKOL or under the name Emulmetike 950 by the company LUCAS MEYER); (b) polyethoxylated sterols such as cholesterol and phytosterol polyethoxylated with 5 to 100 units of ethylene oxide (EO); (c) surfactants chosen from fatty esters of glycerol, fatty esters of sorbitan, fatty esters of polyethoxylated sorbitan, polyethoxylated fatty alcohols and polyethoxylated fatty acids, the fatty chains of these molecules being saturated chains, linear or branched in C12-
30 ; examples that may be mentioned are polyethoxylated behenyl alcohol 30
EO, polyethoxylated stearic acid at 40 EO or polyethoxylated sorbitan laurate at 20 EO; (d) poly (vinyl alcohol), polyvinylpyrrolidone and their copolymers; (e) polyethoxylated polysiloxanes, optionally polypropoxylated (CTFA designation: dimethicone copolyols), such as those described in patents US-A-5,364,633 and US-A-5,411,744. These silicone surfactants correspond in particular to the formula

in which Ra, Rb and R each independently represent a C1-C6 alkyl radical or a radical- (CH2) x- (O-CH2CH2) y-

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 (OCH2CH2CH2) z-ORd where Rd represents a hydrogen atom or an alkyl or acyl radical, at least one of the radicals Ra, Rb and Rc not being a C1-6 alkyl radical, m is an integer ranging from 0 to 200, n is an integer ranging from 0 to 50, the sum m + n being other than zero, x is an integer ranging from 1 to 6, y is an integer ranging from 1 to 30, and z is an integer ranging from 0 to 5.

According to a preferred embodiment of the invention, the alkyl radicals Ra, Rb, Rc or Rd represent a methyl group, x is an integer ranging from 2 to 6 and y an integer ranging from 4 to 30.

dans laquelle m est un nombre entier allant de 20 à 105, n est un nombre entier allant de 2 à 10 et y est un nombre entier allant de 10 à 20, ou les composés de formule (IVb)

Mention may be made, as examples of silicone surfactants of formula (IV), of the compounds of formula (IVa)

in which m is an integer ranging from 20 to 105, n is an integer ranging from 2 to 10 and y is an integer ranging from 10 to 20, or the compounds of formula (IVb)

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in which m and y are whole numbers ranging from 10 to 20. Use may in particular be made, as silicone surfactants, of those sold by the company Dow Corning under the names DC 5329 (compound of formula (IVa) where m = 22, n = 2 , y = 12), DC 7439-146 (compound of formula (IVa) where m = 103, n = 10, y = 12), DC 2-5695 (compound of formula (IVa) where m = 27, n = 3 , y =
12) and Q4-3667 (compound of formula (IIb) where m = 15 and y = 13).

sucres et notamment les esters d'acides gras en C822 et de saccharose, de maltose, de glucose ou de fructose, ou les esters d'acides gras en 14. 22 et de méthylglucose ; (i) les alcényl (C12-3o) succinates choisis parmi les alcénylsuccinates polyalcoxylés, les alcénylsuccinates de glycose polyalcoxylés et les alcénylsuccinates de méthylglucose polyalcoxylés, comme par exemple l'hexadécénylsuccinate de PEG (18 ou 45 OE) et le dihexadécénylsuccinate PEG (18 OE) ; (j) les acétylènediols polyéthoxylés tels que le 2,4, 7,9-tétraméthyl-5-décyne-
4,7-diol éthoxylé (1,3 OE) commercialisé par la société Air Product

Chemical sous la dénomination Surfinol 402 ; (k) les alkyl (Cl230) éthersulfates de sodium tels que le lauryléthersulfate de sodium (en moyenne 2, 2 OE), et les alkyl (C12-3o) sulfates de sodium tels que le laurylsulfate de sodium, le tridécylsulfate de sodium et le cétylstéarylsulfate (50/50) de sodium ; (f) sequenced copolymers of ethylene oxide and propylene oxide; (g) sequenced copolymers of styrene and ethylene oxide such as, for example, the products sold by the company GOLDSCHMIDT under the names SE0418 (PS400 / OE1800), SE0720 (PS700 / OE2000), SE1010 (PS1000 / OE1000), SE1030 (PS1000 / OE3000), or also the anionic sulfated derivatives of these copolymers such as SE1030A sold by the company
Goldschmidt; (h) esters of fatty acids and sugars and ethers of fatty alcohols and

sugars and in particular esters of C822 fatty acids and of sucrose, maltose, glucose or fructose, or esters of 14.22 fatty acids and of methylglucose; i ); (j) polyethoxylated acetylenediols such as 2,4,7,9-tetramethyl-5-decyne-
4,7-ethoxylated diol (1.3 EO) sold by the company Air Product

Chemical under the name Surfinol 402; (k) sodium alkyl (Cl230) ethersulphates such as sodium laurylethersulphate (on average 2, 2 EO), and sodium alkyls (C12-3o) sulphates such as sodium laurylsulphate, sodium tridecylsulphate and sodium cetylstearyl sulfate (50/50);

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dans laquelle les radicaux R4, Rs, R6 et R7 représentent chacun indépendamment un groupe aliphatique, linéaire ou ramifié ou un groupe aromatique tel qu'un noyau aryle ou alkylaryle, comportant de 1 à 30 atomes de carbone ; les groupes aliphatiques peuvent comporter des hétéroatomes tels qu'un atome d'oxygène, d'azote, de soufre ou d'halogène, et sont choisis par exemple parmi les radicaux alkyle, alcoxy,

polyoxy (alkylène en C2-6), alkylamide, (alkyle en Ci2-22)'amido- (alkyle en C2-6), (alkyle en 12-22)-acétate ou hydroxyalkyl, comportant de 1 à environ 30 atomes de carbone ;
X représente un anion choisi parmi les ions halogénures, phosphates, acétates, lactates, alkyl (C2-6)-sulfates, alkyl (C2-6)- ou alkyl (C2-6)- arylsulfonate. (1) quaternary ammonium salts having surfactant properties corresponding to the following formula:

wherein the radicals R4, Rs, R6 and R7 each independently represent an aliphatic group, linear or branched or an aromatic group such as an aryl or alkylaryl ring, having from 1 to 30 carbon atoms; the aliphatic groups may contain heteroatoms such as an oxygen, nitrogen, sulfur or halogen atom, and are chosen, for example, from alkyl, alkoxy,

polyoxy (C2-6 alkylene), alkylamide, (C1-22 alkyl) 'amido- (C2-6 alkyl), (12-22 alkyl) -acetate or hydroxyalkyl, having from 1 to about 30 carbon atoms ;
X represents an anion chosen from halide, phosphate, acetate, lactate, (C2-6) alkyl, (C2-6) alkyl or (C2-6) alkyl (arylsulfonate) ions.

 A preferred compound is myristyltrimethylammonium bromide.

 Among these surfactants, particular preference is given to those of classes (a), (c), (g) and (1).

 The optimum concentration of the surfactant (B) capable of preventing the crystallization of the active principle depends on a large number of factors, for example on the chemical nature of the active principle and of the surfactant, on the size of particles sought, the concentration of active ingredient sought in the final aqueous suspension, or conditions for the preparation of the suspensions.

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 It can be expressed relative to the amount of active ingredient used. The weight ratio of active ingredient (A) / surfactant (B) is preferably between 50 and 0.5, and more preferably between 25 and 1.

dans laquelle R représente un radical alkyle en C16-22, en particulier un radical C16H33 ou C18H37 ou un mélange de ceux-ci, et M représente un métal alcalin ou alcalino-terreux tel que le sodium, et les mélanges de ces composés. The surface-active agents (B) inhibiting the crystallization of the active principle can be of ionic (anionic or cationic) or nonionic nature. In the case where only non-ionic surfactants (B) are used, it may be necessary to guarantee good dispersion of the droplets or particles during the preparation of the aqueous suspensions of nanospheres, that is to say for improve their stability, to introduce into the organic solution of the lipophilic active principle at least one ionic surfactant (C) chosen from * diketyl phosphate, dimyristyl phosphate or their alkaline salts, * the alkaline salts of cholesterol sulphate or cholesterol phosphate , * fatty chain amino acids and their salts such as mono- and di-sodium acylglutamates such as the disodium salt of N-stearoyl-Lglutamic acid sold under the name Acylglutamatee HS21 by the company AJINOMOTO, 'sodium phosphatidates, and * the compounds of formula
R-CH (SO3M) -CO-O (CH2CH2CO) -CH3

in which R represents a C16-22 alkyl radical, in particular a C16H33 or C18H37 radical or a mixture thereof, and M represents an alkali or alkaline earth metal such as sodium, and mixtures of these compounds.

 This ionic surfactant (C) is used in an amount less than or equal to 40% by weight, preferably less than 10% by weight, based on the amount of surfactant (B) inhibiting the crystallization of the lipophilic active principle .

 The aqueous nanosphere suspensions of the present invention can be prepared by two types of methods.

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 The first process, called "nanoprecipitation by solvent tilting" (in English solvent nanoprecipitation) is described in particular in patent application EP-A-0 274 961.

 Applied to the preparation of the aqueous suspensions of nanospheres of the present invention, this process by tilting of solvent consists in dissolving the lipophilic active principle in a concentration of between 0.1 and 30% by weight in an organic solvent more volatile than water and miscible with it, e to introduce, with moderate stirring, the organic solution of the active principle in an aqueous phase, at least one of these two phases containing at least one surfactant (B) in a higher concentration or equal to its critical micellar concentration, then e to evaporate the organic solvent more volatile than water, as well as possibly part of the water.

 In this process, thanks to the presence of at least one surfactant, the nanospheres are formed spontaneously by precipitation of the active principle during the mixing of the organic solution of the active principle and of the aqueous phase. The volume of aqueous phase must be sufficient to obtain satisfactory precipitation of the lipophilic active principle. In practice it is never lower than that of the organic solution.

 The weight ratio aqueous phase / organic phase is at least equal to 1 and preferably between 1 and 20.

 The size of the nanospheres depends in particular on the nature of the solvent, the concentration of the active principle in it, the organic phase / aqueous phase ratio, as well as the nature and the amount of the surfactant (B) inhibiting the crystallization of the lipophilic active principle.

Mention may be made, as solvents which are more volatile than water and which are miscible with it, ketones such as acetone, C1-6 alcohols such as methanol or isopropanol, tetrahydrofuran, as well as mixtures of these solvents. .

As indicated above, it may be advantageous, when using a nonionic surfactant (B), to combine one or more agents with it

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 surfactants (C) chosen from those indicated above. This surfactant (C) is then introduced into the organic phase.

 The second type of process for preparing the aqueous suspensions of nanospheres of the present invention differs from the first process described above mainly by the immiscibility of the organic phase with the aqueous phase. The mixing of the organic solution of the lipophilic active principle and of the aqueous phase will therefore give rise to an oil-in-water emulsion.

à dissoudre le principe actif lipophile en une concentration comprise entre 0, 1 et 30 % en poids dans un solvant organique plus volatil que l'eau et non miscible avec celle-ci, e à émulsifier la solution organique du principe actif avec une phase aqueuse, l'une au moins de ces deux phases contenant au moins un agent tensio-actif (B) en une concentration supérieure ou égale à sa concentration micellaire critique, puis e à évaporer rapidement le solvant organique plus volatil que l'eau, et éventuellement une partie de l'eau. This so-called emulsification process consists in particular

dissolving the lipophilic active principle in a concentration of between 0.1 and 30% by weight in an organic solvent more volatile than water and immiscible with it, e emulsifying the organic solution of the active principle with an aqueous phase , at least one of these two phases containing at least one surfactant (B) in a concentration greater than or equal to its critical micellar concentration, then e to rapidly evaporate the organic solvent more volatile than water, and optionally part of the water.

 The organic solvents more volatile than water and immiscible with it are chosen for example from halogenated hydrocarbons such as dichloromethane, or cyclic hydrocarbons such as cyclohexane and toluene.

 The aqueous phase / organic phase weight ratio during the emulsification step is between 1.5 and 99.

 Contrary to what happens for the first type of process, nanospheres do not form spontaneously but it is generally necessary to refine the preemulsion obtained by passing it one or more times through a high pressure homogenizer (10 to 120 MPa) or by exposing it to ultrasound. The size of the nanospheres obtained will depend directly on the efficiency of this advanced emulsification step.

 As with the solvent tilting process, it can be useful when the surface-active agent (B) which inhibits crystallization is non-ionic,

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 to use, in addition to this, one or more surfactants (C) chosen from those indicated above and always introduced into the organic phase.

 The aqueous suspensions of nanospheres obtained according to one of the two types of process described above can be concentrated by elimination of a certain amount of the aqueous phase. This elimination can be done for example by evaporation under vacuum or by ultrafiltration.

 Generally, large concentrations of active principle will be sought for which the stability of the nanospheres in suspension remains satisfactory, in other words the content of active principle of the aqueous nanosphere suspensions will preferably be adjusted to a value of between 0.2 and 50% by weight, preferably between 1 and 20% by weight by weight, relative to the total weight of the aqueous suspension of nanospheres.

 The present invention also relates to cosmetic compositions containing such an aqueous suspension of nanospheres of lipophilic active principle.

 These cosmetic compositions contain from 0.1 to 40% by weight, and preferably from 1 to 30% by weight of aqueous suspension of nanoparticles of active principle, in a cosmetically acceptable medium.

 These compositions can be presented, for example, in the form of lotions, gels, suspensions, emulsions such as W / O, O / W, multiple W / O / W emulsions, O / W / O, or nanoemulsions .

 They can contain additives and adjuvants usually used in the cosmetic field such as antioxidants, essential oils, hydrating agents, vitamins, essential fatty acids, spingolipids, self-tanning agents, anti-radical agents, filters. sunscreen, perfumes, preservatives, dyes, defoamers, sequestering agents, pH adjusting agents, hydrophilic thickeners such as polysaccharides (xanthan gum), Carbomers (carboxyvinyl polymers), partially neutralized and highly crosslinked polyacrylamidomethylpropanesulfonic acid.

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 Of course, a person skilled in the art will take care to choose any additional compounds so that the advantageous properties of the composition according to the invention, and in particular the stability of the nanospheres, are not, or practically not, affected by the planned addition.

 The present invention will be illustrated by the following examples.

Example 1
Preparation of N-cholesteryloxycarbonyl-4-aminophenol nanospheres according to a nanoprecipitation process by solvent tilting
A solution of 0.6 g of N-cholesteryloxycarbonyl-4-aminophenol and 0.1 g of soy lecithin in 20 g of acetone is prepared. The solution is heated to 45 ° C. and poured into 100 g of distilled water heated to 45 ° C. The acetone is evaporated in vacuo on a rotary evaporator, then the aqueous suspension obtained is concentrated to a total weight of about 40 g.

 This gives an aqueous suspension of nanospheres of N-cholesteryloxycarbonyl-4-aminophenol at 1.5% by weight, having an average particle diameter of 90 nm and which shows no sign of crystallization after 7 days of storage at temperature from 4 C to 45 C.

Example 2
Preparation of N-cholesteryloxycarbonyl-4-aminophenol nanospheres according to a nanoprecipitation process by solvent tilting
The procedure of Example 1 is repeated except that we use
1.2 g of active ingredient and 40 g of acetone. This gives a suspension of nanospheres of N-cholesteryloxycarbonyl-4-aminophenol at 3% by weight having an average particle diameter of 115 nm and which has no

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signe de cristallisation au bout de 7 jours de conservation à une température de 4 C à45 C.

sign of crystallization after 7 days of storage at a temperature of 4 C to 45 C.

Example 3
Preparation of N-cholesteryloxycarbonvl-4-aminophenol nanospheres according to a nanoprecipitation process by solvent tilting
The procedure is analogous to that described in Example 1 but using, instead of 0.1 g of soy lecithin, 0.03 g of myristyltrimethylammonium bromide and without heating the two phases to be mixed. An aqueous suspension of N-cholesteryloxycarbonyl- nanospheres is obtained.
1.5% by weight 4-aminophenol having an average particle diameter of
120 nm and which shows no sign of crystallization after 7 days of storage at a temperature of 4 ° C. to 45 ° C.

OE) dans 20 g d'isopropanol. On chauffe cette solution à 45 oC et on la verse dans 100 g d'eau distillée chauffée à 45 C. On évapore l'isopropanol sous vide dans un évaporateur rotatif, puis on concentre la suspension aqueuse obtenue jusqu'à un poids total d'environ 40 g. Example 4 Preparation of aqueous suspensions of ursolic acid nanospheres according to a nanoprecipitation process by tilting of solvent
0.3 g of ursolic acid and 0.1 g of polyethoxylated stearate are dissolved (20

OE) in 20 g of isopropanol. This solution is heated to 45 oC and poured into 100 g of distilled water heated to 45 C. The isopropanol is evaporated in vacuo in a rotary evaporator, then the aqueous suspension obtained is concentrated to a total weight of about 40 g.

 A stable aqueous suspension of nanospheres of ursolic acid containing 0.75% by weight of active material is thus obtained. The nanospheres have an average diameter of 322 nm.

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Example 5 Preparation of aqueous suspensions of N-cholesteryl-oxycarbonyl-4-aminophenol nanospheres according to an emulsification process
2.5 g of N-chlorolesteryloxycarbonyl-4-aminophenol and 1.5 g of soy lecithin are dissolved in 20 g of dichloromethane. In an rotor-stator type device, this organic phase is emulsified with 76 ml of distilled water. The primary emulsion thus obtained is refined by 3 passages in a high pressure homogenizer at 45 MPa, then the dichloromethane and approximately 40 ml of water are evaporated. A stable aqueous suspension of nanospheres is obtained having an active ingredient concentration of 6.25% by weight. The nanospheres have an average diameter of 105 nm.

Claims (26)

R3 represents a radical chosen from C1 to C30 alkyl radicals, saturated or unsaturated, linear, branched or cyclic, including condensed polycyclics, and optionally hydroxylated, and (B) of at least one water-soluble or fat-soluble inhibiting surfactant the crystallization of the lipophilic active principle (A), capable, at its critical micellar concentration, of lowering the interfacial tension of the hexane / water system R2 represents a hydrogen atom or a radical chosen from alkyl radicals, saturated or unsaturated, linear, cyclic or branched, in Cl2 to C30, optionally hydroxylated,  (iii) -SO2-R3 where RI represents a hydrogen atom or an alkyl radical in CI-6, linear or branched, saturated or unsaturated, optionally hydroxylated,

 .. NH-R HO-JJ in which R is a radical corresponding to one of the following formulas (i), (ii) or (iii) (i) -CO-NRIR2 (ii) -CO-O-R3

 CLAIMS 1. Aqueous suspension of nanospheres of lipophilic active principle having an average particle size ranging from 10 nm to 1 gb, characterized in that it comprises, in a physiologically acceptable aqueous medium, nanospheres consisting essentially (A) of at least one lipophilic active principle, in amorphous form, chosen from dehydroepiandrosterone (DHEA) and its chemical and biological precursors and derivatives with the exception of cholesterol and its esters and plant sterols such as phytosterols and sitosterols, and their esters, pentacyclic triterpene acids, hydroxystilbenes, isoflavonoids, and aminophenol derivatives of formula <Desc / Clms Page number 22>  from 51 mN / m to a value less than or equal to 12 mN / m and / or to lower the surface tension of the water to a value less than or equal to 50 mN / m.  2. Aqueous suspension of nanospheres according to claim 1, characterized in that the content of lipophilic active principle is between 0.2 and 50% by weight, preferably between 1 and 20% by weight, relative to the total weight of the aqueous suspension of nanospheres.  3. Aqueous suspension of nanospheres according to claim 1 or 2, characterized in that the average size of the nanospheres of lipophilic active ingredients is between 50 and 500 nm.  4. Aqueous suspension of nanospheres according to any one of the preceding claims, characterized in that the lipophilic active principle is chosen from dehydroepiandrosterone (DHEA), DHEA sulfate, 7a-hydroxy-DHEA, 7-keto- DHEA, prednisolone, prednisone, progesterone, pregnenolone, testosterone, diosgenin, hecogenin, ursolic acid, oleanolic acid, resveratrol (= 3,4 ', 5trihydroxystilbene) and N-cholesteryloxycarbonyl -4-aminophenol, isoflavonoids whose solubility in water at room temperature (25 OC) is less than 0.01%.  5. Aqueous suspension of nanospheres according to any one of the preceding claims, characterized in that the surfactant (B) inhibiting the crystallization of the lipophilic active principle is chosen from (a) natural or synthetic phospholipids, hydrogenated or not , enriched or not with phosphatidylcholine, (b) polyethoxylated sterols, (c) surfactants chosen from glycerol fatty esters, sorbitan fatty esters, polyethoxylated sorbitan fatty esters, polyethoxylated fatty alcohols and acids polyethoxylated fats, the fatty chains of these molecules being saturated, linear or branched; (d) poly (vinyl alcohol), polyvinylpyrrolidone and their copolymers, <Desc / Clms Page number 23>  in which the radicals R4, Rs, R6 and R7 each independently represent an aliphatic group, linear or branched or an aromatic group such as an aryl or alkylaryl ring, comprising from 1 to 30 carbon atoms, and X is chosen from anions halides, phosphates, acetates, lactates, (C2-6) alkylsulfates, (C2-6) alkyls - or (C2-6) alkylsarylsulfonates.

 (j) polyethoxylated acetylenediols, (k) sodium alkyl (Cl230) ethersulphates and sodium alkyl (CI2-3o) sulphates, (1) quaternary ammonium salts having surfactant properties corresponding to the following formula :

 sugars and in particular esters of fatty acids in Ce. 22 and sucrose, maltose, glucose or fructose, or the esters of fatty acids in Cul422 and methylglucose, and mixtures thereof; (i) the alkenyl succinates chosen from polyalkoxylated alkenyl succinates, polyalkoxylated glucose alkenyl succinates and polyalkoxylated methylglucose alkenyl succinates,

 (e) the polyethoxylated polysiloxanes, optionally polypropoxylated (CTFA name: dimethicone copolyols), (f) the sequenced copolymers of ethylene oxide and of propylene oxide, (g) the sequenced copolymers of styrene and of oxide ethylene and the anionic sulfate derivatives thereof, (h) esters of fatty acids and sugars and ethers of fatty alcohols and  6. Aqueous suspension of nanospheres according to claim 5, characterized in that the surface-active agent (B) is a phospholipid chosen from soy lecithin enriched with phosphatidylcholine and hydrogenated soy lecithin. <Desc / Clms Page number 24>  7. Aqueous suspension of nanospheres according to claim 5, characterized in that the surfactant (B) is a polyethoxylated sterol chosen from cholesterol and phytosterol polyethoxylated with 5 to 100 units of ethylene oxide (EO) ) 8. Aqueous suspension of nanospheres according to claim 5, characterized in that the surfactant (B) is behenyl alcohol polyethoxylated at 30 EO, stearic acid polyethoxylated at 40 EO, or polyethoxylated sorbitan laurate at 20 EO.  9. Aqueous suspension of nanospheres according to claim 5, characterized in that the surfactant (B) is a polyethoxylated and optionally polypropoxylated polysiloxane of formula

 in which Ra, Rb and R: each independently represent a

 C1-6 alkyl radical or a radical- (CH2) x- (O-CH2CH2) y- (OCH2CH2CH2) z-ORd where Rd represents a hydrogen atom or an alkyl or acyl radical, at least one of the radicals Ra, Rb and Rc not being a C1-C6 alkyl radical, m is an integer ranging from 0 to 200, n is an integer ranging from 0 to 50, the sum m + n being other than zero, x is a integer ranging from 1 to 6, y is an integer ranging from 1 to 30, and z is an integer ranging from 0 to 5.  10. Aqueous suspension of nanospheres according to claim 9, characterized in that the surfactant (B) is a polysiloxane <Desc / Clms Page number 25>  polyethoxylated and optionally polypropoxylated of formula (IV) in which the alkyl radicals Ra, Rb, Re or Rd are methyl radicals, x is an integer ranging from 2 to 6 and y an integer ranging from 4 to 30.  11. Aqueous suspension of nanospheres according to claim 9, characterized in that the surfactant (B) has the formula

 in which m is an integer ranging from 20 to 105, n is an integer ranging from 2 to 10 and y is an integer ranging from 10 to 20, 12. Aqueous suspension of nanospheres according to claim 9, characterized in that the surfactant (B) has the formula

 where m and y are integers ranging from 10 to 20.  13. Aqueous suspension of nanospheres according to claim 5, characterized in that the surfactant (B) is myristyltrimethylammonium bromide.  14. Aqueous suspension of nanospheres according to any one of the preceding claims, characterized in that the weight ratio of <Desc / Clms Page number 26>  lipophilic active ingredient (A) to the surfactant (B) is between 50 and 0.5, preferably between 25 and 1.  15. Aqueous suspension of nanospheres according to any one of the preceding claims, characterized in that it also comprises at least one ionic surfactant (C) chosen from diketyl phosphate and dimyristyl phosphate in the form of acids or alkaline salts, the alkaline salts of cholesterol sulfate and cholesterol phosphate, the fatty chain amino acids and their salts, sodium phosphatidates, and the compounds of formula R-CH (SO3M) -CO-O (CH2CH2CO) -CH3 in which R represents a C16-22 alkyl radical, in particular a C16H33 or C1sH37 radical or a mixture of these, and M represents an alkali or alkali metal - earthy, and their mixtures.  16. Aqueous suspension of nanospheres according to claim 15, characterized in that the concentration of the ionic surfactant (C) is less than or equal to 40% by weight, preferably less than or equal to 10% by weight, compared to that of the surfactant (B) inhibiting the crystallization of the lipophilic active principle.  17. Method for preparing an aqueous suspension of nanospheres of lipophilic active principle according to any one of the preceding claims, characterized in that it comprises the steps consisting in dissolving the lipophilic active principle in a concentration of between 0, 1 and 30% by weight in an organic solvent more volatile than water and miscible with it, e to introduce, with stirring, the organic solution of the active principle in an aqueous phase, at least one of these two phases containing at least one surfactant (B) in a concentration greater than or equal to its critical micelle concentration, then e to evaporate the organic solvent and optionally part of the water. <Desc / Clms Page number 27>  18. The method of claim 17, characterized in that the organic solvent more volatile than water and miscible with the latter is chosen from ketones such as acetone, Cl-6 alcohols such as methanol or l isopropanol, tetrahydrofuran, and mixtures of these solvents.  19. The method of claim 17 or 18, characterized in that the aqueous phase / organic phase ratio is at least equal to 1, preferably between 1 and 20.  20. Process for the preparation of an aqueous suspension of nanospheres of lipophilic active principle according to any one of claims 1 to 16, comprising the steps consisting in dissolving the lipophilic active principle in a concentration of between 0.1 and 30% by weight in an organic solvent more volatile than water and immiscible with it, e to emulsify the organic solution of the active principle with an aqueous phase, at least one of these two phases containing at least one surfactant (B) in a concentration greater than or equal to its critical micelle concentration,

 then evaporating the organic solvent and possibly part of the water.  21. The method of claim 20, characterized in that the organic solvent more volatile than water and immiscible with it is chosen from halogenated hydrocarbons such as dichloromethane, and cyclic hydrocarbons such as cyclohexane and toluene .  22. Method according to claim 20 or 21, characterized in that the aqueous phase / organic phase ratio during the emulsification step is between 1.5 and 99.  23. A method of preparing an aqueous suspension of nanospheres according to any one of claims 17 to 22, characterized in that at least one surfactant is introduced into the organic phase <Desc / Clms Page number 28>  in which R represents a C1-222 alkyl radical, in particular a Ci6H33 or Ci8H37 radical or a mixture thereof, and M represents an alkali or alkaline earth metal such as sodium, and mixtures thereof.

R-CH (SO3M) -CO-O (CH2CH2CO) -CH3  ionic (C) chosen from diketyl phosphate and dimyristyl phosphate in the form of acids or alkaline salts, alkaline salts of cholesterol sulfate and cholesterol phosphate, fatty chain amino acids and their salts, phosphatidates of sodium, and the compounds of formula  24. Method for preparing an aqueous suspension of nanospheres according to any one of claims 17 to 23, characterized in that the aqueous suspension of nanospheres of lipophilic active principle obtained is concentrated, by elimination of a certain amount of aqueous phase until a content of lipophilic active principle of between 0.2 and 50% by weight, preferably between 1 and 20% by weight, relative to the total weight of the aqueous suspension of nanospheres is obtained.  25. Cosmetic composition containing, in a cosmetically acceptable medium, an aqueous suspension of nanospheres of lipophilic active principle according to any one of claims 1 to 16.  26. Cosmetic composition according to claim 25, characterized in that it contains from 0.1 to 40% by weight, preferably from 1 to 30% by weight of aqueous suspension of nanoparticles of lipophilic active principle according to any one of claims 1 to 16.