FR2597346A1 - PROCESS FOR FACILITATING THE FORMATION OF NIOSOMES IN DISPERSION IN AN AQUEOUS PHASE AND FOR IMPROVING THEIR STABILITY AND THEIR ENCAPSULATION RATE, AND CORRESPONDING DISPERSIONS. - Google Patents

Abstract

THIS PROCESS ALLOWS TO FACILITATE THE FORMATION OF NIOSOMES IN DISPERSION IN AN AQUEOUS MEDIUM D AND SIMULTANEOUSLY IMPROVE THE STABILITY AND THE ENCAPSULATION RATE OF SAID NIOSOMES, EACH CONSTITUTING OF A LIPID SHEET, OR OF SEVERAL LIPID SHEETS, OR OF SEVERAL SHEET CONCENTRICS, THE SHEET (OR THE SAID) SHEET (S) ENCAPSULATING AN AQUEOUS PHASE E. FOR THIS EFFECT, BEFORE THE FORMATION OF THE SAID NIOSOMES, WE ADD TO THE LIPID (S) INTENDED TO CONSTITUTE THE SHEETS OF NIOSOMES, CHOLESTEROL -PHOSPHATE, FROM 1 TO 40 IN WEIGHT IN RELATION TO THE TOTAL WEIGHT OF THE LIPID PHASE.

Description

METHOD FOR FACILITATING THE FORMATION OF DISPERSION NIOSOMES IN A

  AQUEOUS PHASE AND TO IMPROVE THEIR STABILITY

  AND THEIR ENCAPSULATION RATE, AND CORRESPONDING DISPERSIONS.

  The present invention relates to aqueous dispersions of niosomes, these dispersions being usable in the cosmetic, pharmaceutical and food fields. More specifically, it relates to a method for facilitating the formation of these niosomes and for simultaneously improving

  their stability in aqueous dispersions, as well as their degree of encapsulation.

  It is known that certain lipids have the property of forming, in the presence of water, mesomorphic phases whose state of organization is intermediate between the crystalline state and the liquid state. Among the lipids which give rise to mesomorphic phases, it has already been indicated that some can swell in aqueous solution to form spherules dispersed in the aqueous medium, these spherules being constituted by multi-molecular layers and

  preferably bi-molecular layers.

  In French Patent No. 2,315,991, dispersions of lipid spherules have already been described; these spherules are characterized by their sheet structure consisting of two or more lipid layers separated from each other by layers of aqueous phase; they can thus serve to encapsulate, in the aqueous compartments comprised between the lipid layers, water-soluble active substances, for example pharmaceutical or cosmetic, and to protect them from external conditions. The lipid compounds which can be used to constitute such spherules can be ionic compounds, in which case liposomes are obtained, or nonionic compounds,

in which case we get niosomes.

  The present invention is limited to the implementation

work of niosomes.

  When preparing niosomes, various additives can be combined with the nonionic lipid compounds, in order to modify the permeability or the surface charge of the spherules. A number of these additives have been cited in this regard in French patents 2,315,991, 2,485,921 and 2,490,504. It is thus known that, when it is desired to reduce the permeability of the vesicles, it is possible to add, to lipid compounds, sterols, in particular cholesterol,

  these sterols increasing the rigidity of the multi-layers.

  It is also known that the incorporation of electrically charged molecules into the walls of the niosomes affects the properties of these multi-layers. The role of charged lipids, such as diketylphosphate, phosphatidic acid, amines or ammonium quaternaries with long hydrocarbon chains, is to improve the stability of the vesicles by preventing their flocculation and, therefore, their fusion, even in the presence electrolytes, and to allow the increase of the rate of encapsulation of water-soluble substances by increasing the thickness of the aqueous sheets which separate the

lipid multi-layers.

  For liposomes, it has also been demonstrated, by A. Colombat et al, Biochemistry (1981), 63, 795-798, that cholesterol phosphate, that is to say, a hydrophilic ester of cholesterol, combines, on the one hand, the effects of a charged amphiphilic, namely to increase the stability of the liposomes and their encapsulation rate, and, on the other hand, the effect of cholesterol, namely to decrease the permeability of liposomes. We observe however that the introduction of

  more than 5% by weight of lipids loaded in the vesicular membrane results in either a high permeability to solutes or a recrystallization of the loaded lipid.

  However, the Depositing Company has discovered that, surprisingly, the cholesterol phosphates do not have the abovementioned drawbacks when they are associated with niosomes and are distinguished from other charged li35 pides by the fact that they can be introduced up to 40% by weight in the lipid membrane, without

  observe recrystallization, and that at already high percentages in the membrane (10% by weight), they induce only a low permeability.

  The subject of the present invention is therefore a process for facilitating the formation of niosomes in dispersion in an aqueous medium D, and for simultaneously improving the stability and the encapsulation rate of said niosomes, the latter each consisting of a lipid sheet, or more substantially concentric lipid sheets, said sheet (s) encapsulating an aqueous phase E, characterized in that before the formation of said niosomes, the nonionic lipid (s) are added intended for constituting the sheets of nioso15 mes, at least one cholesterol-phosphate in free acid form or neutralized by an ammonium, alkaline or alkaline-earth cation, to

  1 to 40% by weight relative to the total weight of the lipid phase.

  In practice, the maximum threshold depends on the

  nature of the lipid used and it can be between 10 20 and 40% by weight in the lipid phase of the niosomes.

  Cholesterol phosphate is preferably used

  of ammonium, substituted or not, of sodium or potassium.

  A subject of the invention is also a dispersion of niosomes obtained by the process defined above, said process possibly incorporating the characteristics

  which will be detailed below.

  To carry out the dispersion in the aqueous phase D of the niosomes, any of the methods can be used

previously known and described.

  One can, for example, use the method which consists in dissolving the lipids in a volatile solvent, in forming a thin film of lipids on the walls of a bottle by evaporation of the solvent, in introducing into said bottle the aqueous phase E to encapsulate and agitate the mixture mechanically until the dispersion of niosomes at the desired size is obtained; in this case, the phases

  aqueous D and E are necessarily identical.

  It is also possible to use the process described in French Patent No. 2 315 991, which consists in forming a planar lamellar phase by introducing the aqueous phase to be encapsulated E in the liquid nonionic lipid (s), at a temperature ------------- slightly higher than the melting temperature of the lipids, then add to the lamellar phase obtained an aqueous phase of dispersion D, which may or may not be identical to the phase aqueous E, and stir vigorously, for example me-. 10 canically, to obtain the transition from the planar lamellar phase to a dispersion, in the aqueous phase D, of niosomes

  encapsulating the aqueous phase E. Depending on the means used to produce the dispersion (ultra-disperser, homogenizer and / or ultrasound).

  and depending on the stirring time (from 15 minutes to some 15 hours), niosomes are obtained, the mean diameter of which

  ranges from about 0.025 to 5 microns.

  The above-mentioned method is particularly suitable when it is desired to use multilamellar niosomes. If it is desired to use unilamel 20-niosomes, the process described in French patent 2,543,018 can be used for their preparation; according to this method, the lipids intended to form the niosome sheet are dissolved in at least one solvent insoluble in water; the lipid solution is conditioned in the liquid state, in a container, at a pressure P1 and at a temperature e1; the aqueous phase to be encapsulated E is conditioned at a pressure P2 and at a temperature e2, and the lipid solution is injected into the aqueous phase so that the solvent (s) of the lipid solution vaporizes (s) when it (s) come (s) into contact with said aqueous phase, said injection being carried out with a reduced flow rate

  to initially form droplets, the pressure P2 being lower than the pressure P1 and the vapor pressure of the solvent (s) in said droplets at temperature 92.

  As indicated above, the cholesterol phosphate is added at any time before the formation of the niosomes, that is to say, when one goes through the formation of a lamellar phase, ie before the preparation of the said lamellar phase, either after. The lipids used for the preparation of the spherules are nonionic amphiphiles of natural or synthetic origin, comprising, per molecule, one or more long hydrocarbon chain (s) having in particular from 12 to 30 carbon atoms , like chains

  oleic, lanolic, tetradecylic, hexadecylic, isostearyl, lauric or alkylphenyl, and one (or more) hydrophilic group (s).

  For these nonionic amphiphiles, it is preferred that the hydrophilic groups are polyoxyethylenated or polyglycerolated groups, or groups deriving from esters of polyols which are oxyethylenated or not. Advantageously, these nonionic lipid compounds are chosen from the group formed by: the polyglycerol ethers, linear or branched, of respective formulas:

R- (OCH2 -CH-CH2.OH

  OH and RtRO-CH2-CH) '- OH CH2OH 4 being a mean statistical value between 1 and 6, R being a linear or branched, saturated or unsaturated aliphatic chain, comprising from 12 to 30 carbon atoms, the hydrocarbon radicals of lanolin alcohols, 2-hydroxy alkyl radicals of long chain &diols; - polyoxyethylenated fatty alcohols; polyol ethers; - polyoxyethylenated sterols; - esters of polyols, oxyethylenated or not and, in particular, polyoxyethylenated sorbitol esters; - glycolipids of natural or synthetic origin, for example

example cerebrosides.

  In known manner, various additives can be combined with the lipid compounds in order to modify the permeability or the surface charge of the spherules. In this regard, mention may be made of the possible addition of long-chain alcohols and diols, sterols, for example cholesterol and tsitosterol, long-chain amines, hydroxyalkylamines, polyoxyethylenated fatty amines, amino esters long chain alcohols, their salts, phosphoric esters of fatty alcohols, for example sodium diketylphosphate and alkyl sulfates, for example sodium cetylsulfate, ionic derivatives of sterols other than cholesterol phosphates. Advantageously, one can use, to constitute

  the dispersion of niosomes, from 0.5 to 25% by weight of nonionic amphiphilic (s) relative to the total weight of the dispersion of niosomes to be obtained.

  Provision may be made for the aqueous phase E to be encapsulated in the niosomes to be an aqueous solution of active substance, preferably isoosmotic with respect to phase D

of dispersion.

  For a cosmetic composition, the aqueous phase E 25 encapsulated in the niosomes contains, for example, at least one product taken from the group formed by humectants, such as glycerin, sorbitol, pentaerythritol, inositol, acid pyrrolidone-carboxylic acid and its salts; artificial browning agents, such as dihydroxy30 acetone, erythrulose, glyceraldehyde, Y-dialdehydes, such as tartaric aldehyde, optionally combined with dyes; water-soluble sunscreen agents; antiperspirants; deodorants; astringents; of

  refreshing, toning, healing, keratoly-

  ticks, depilatories; extracts of animal or plant tissue; scented waters; water-soluble dyes;

  anti-dandruff agents; anti-seborrheic agents; oxidants such as hydrogen peroxide and reducers such as thioglycolic acid and its salts.

  In the case of a composition which can be used in pharmacies, the aqueous phase E encapsulated in the niosomes preferably contains at least one product taken from the group formed by vitamins, hormones, enzymes, such as super10 oxide dismutase, vaccines, anti-inflammatories, such

  than hydrocortisone, antibiotics and bactericides.

  It is also possible to provide that the aqueous phase D surrounding the niosomes contains at least one liquid phase immiscible with water dispersed in said aqueous phase D. This liquid phase immiscible with water can be an oil or a constituent taken from the group formed by hydrocarbons, halogenated carbides, polysiloxanes, esters of organic acids, ethers and polyethers. Advantageously, the amount of liquid phase immiscible with water, dispersed in the aqueous phase D, is between 2 and 70% by weight relative to the total weight of the composition,

  the relative weight proportion of amphiphilic lipid (s) constituting _nicsomes with respect to the liquid phase (s) immiscible with water, dispersed (s), being between 0.02 / 1 and 10/1.

  The oil used to be dispersed in the aqueous phase D is advantageously taken from the group formed by esters of fatty acids and of polyols, in particular liquid triglycerides, and esters of fatty acids and of branched alcohols of formula 30 R4-COOR5, formula in which R4 represents the remainder of a higher fatty acid containing from 7 to 19 carbon atoms and R5 represents a chain

  branched hydrocarbon containing from 3 to 20 carbon atoms.

  In such a case, if the oil is an ester of fatty acids and of polyols, it is preferred that it is chosen from the group formed by sunflower, corn, soybean, squash, seed oil. grapes, jojoba and glycerol tri-caprocaprylate; if, on the contrary, the oil is an ester of higher fatty acids and of branched alcohol, it is preferred that said oil is Purcellin oil; To constitute the liquid phase immiscible with water, it is still advantageously possible to choose hexadecane,

  paraffin oil, perhydrosqualene, perfluorotributylanine and perfluorodecahydronaphthalene.

  It is also possible to provide that the aqueous phase D, which surrounds the niosomes, contains at least one adjuvant taken from the group formed by opacifiers, gelling agents, aromas, perfumes, sunscreen filters and dyes, those of these adjuvants which are liposoluble and which can be dissolved in the liquid phase immiscible with water dispersed in the aqueous phase D, in case a

such dispersion.

  If the dispersed water-immiscible liquid added in the continuous aqueous phase, which surrounds the niosomes, must contain dissolved adjuvants, the dissolution of these

  adjuvants is carried out before dispersing.

  Such adjuvants can be, for example, sunscreen filters, such as 2-ethyl hexyl paradimethylamino benzoate or substances intended to improve the condition of dry or senile skin, in particular

  unsaponifiables such as soJa, avocado unsaponifiables, tocopherols, vitamins E, F. antioxidants.

  The dispersion of oil in water which constitutes the external medium of the dispersion of niosomes may contain 3O

  at least one additive, in particular a gelling agent or a perfume.

  The additive is added to the dispersion at the same time as the oil.

  The gelling agent can be introduced at a concentration varying between 0.1 and 2%, these percentages being expressed by weight par relative to the total weight of the composition. Among the gelling agents which can be used, mention may be made of cellulose derivatives, such as hydroxyethylcellulose; algae derivatives, such as satiagum or natural gums, such as tragacanth. It is preferred to use, as gelling agents, hydroxyethylcellulose, a mixture of carboxyvinylic acids which is commercially available under the name "CARBOPOL

  940 ", satiagum or even tragic.

  When a composition comprising a dispersion of liquid (s) immiscible with water is produced, it is found

  that this dispersion is stable without the use of an emulsifier.

  the present invention therefore also relates to a disper10

  sion of niosomes in an aqueous medium D, said niosomes each consisting of a lipid sheet or of several substantially concentric lipid sheets, said sheet (s) encapsulating an aqueous phase E, characterized in that it is obtained by the method as defined above.

  We will give below some examples of preparation using the invention and some examples of

  formulation illustrating the use of the spherule dispersions according to the invention.

  The cosmetic or pharmaceutical formulas given in the examples below are prepared

in one or two phases.

  In a first phase, an aqueous dispersion is produced according to the process described in French patent 2,315,991 (examples 1 to 3). The aqueous dispersion of lipid spherules is prepared from: - a nonionic amphiphilic lipid, - phosphate cholesterol, used alone or associated with cholesterol,

  - active cosmetic substances of a liposoluble and / or water-soluble nature and demineralized water.

  In a second optional phase, depending on the cosmetic or pharmaceutical nature of the formulation,

  may add oil to the external medium, so as to form an oil-in-water system according to the method described in French patents Nos. 2,485,921 and 2,532,191.

2597346-

  Also add different cosmetic additives. EXAMPLE 1 CARE CREAM FOR DRY SKIN products 1st phase: In a stainless steel beaker, the following are weighed: - nonionic amphiphilic lipid of formula R- (OCHCH -) OH OH2OH in which R is a hexadecyl radical and has mean statistic value equal to 3 ........... 4.00 - cholesterol. .......; .....

  . 2.00 g g The two products are mixed by fusion at a temperature of 110 ° C. under a nitrogen atmosphere. Then, .. DTD: the temperature of the molten mixture is reduced to 900C. 20 g of demineralized water are added and the mixture obtained is homogenized at a temperature of 90 C.

  At this same temperature, 2 g of choles20 terol phosphate (acid form) are added and the mixture is homogenized until the total disappearance of the non-associated lipid crystals, which are checked by examination under an optical microscope.

in polarized light.

  We then add: - methyl parahydroxybenzoate (stabilizer) .........

  .......... 0.30 g - glycerin ........................... 5.00 g - demineralized water ................... 25.50 g At the temperature of 700 C, the mixture 30 is homogenized using an ultradisperser of the "Virtis" type until at this..DTD: that the average size of the vesicles obtained is 0.5 micron.

  2nd phase The following products are added to the above mixture: - sweet almond oil .............. 5.00 g - Cetiol LC sold by the company HENKEL (mixture of esters C8-C10 acids and C17C18 fatty alcohols) ... 10.00 g The whole is subjected to the action of a "Virtis" ultradisperser until the oil globules have a dia10

average meter of about 1 micron.

  Finally, the following additives are added: - Perfume ...........................

  . 0.40 g - Mixture of carboxyvinyl acids marketed under the name of "CARBOPOL 940" ...................... 0.40 g Triethanolamine .... ........ DTD: ......... 0.40 g - Demineralized water ................... 25.00 g. .DTD: It should be noted that this composition remains stable for a period greater than 2 years.

  This cream, applied in topical use a

  once a day on subjects with dry skin, gives satisfactory results after 20 days of application.

  EXAMPLE 2 CONCENTRATE FOR IRRITATED SKIN In a stainless steel beaker, the following products are weighed: - nonionic amphiphilic lipid of formula R- (O- H-CH2 --OH CH2OH in which R is a hexadecyl radical and M has a mean statistical value equal to 3 .................

  7.60 g - cholesterol ......................... 7.60 g The two products are mixed by melting at a temperature of 110 C under a nitrogen atmosphere, .. DTD: then the temperature of the molten mixture is brought back to 90 C.

  40 g of demineralized water and 5 g of glycerin are added. The mixture obtained is homogenized at a temperature of 90 ° C. and 0.8 g of phosphate cholesterol (acid form) is added. The mixture is homogenized until total disappearance of the non-associated lipid crystals, which are controlled

  by examination under an optical microscope in polarized light.

  The following products are then added: - methyl parahydroxybenzoate (stabilizer) ..................... 0.30 g - demineralized water ........ ...

  ....... 38.70 g At the temperature of 70 C, the mixture is homogenized using an ultradisperser of the "Virtis" type. DTD: until the average size of the vesicles obtained or 30 of about 0.3 microns.

  It should be noted that this composition remains stable

  for a period longer than 2 years.

  This cream, used topically twice a day on subjects with irritated acne skin, reduces irritation after one or two weeks of application.

Claims (10)

  1 - Process for facilitating the formation of niosomes in dispersion in an aqueous medium D, and for simultaneously improving the stability and the encapsulation rate of said 5 niosomes, these each consisting of a lipid sheet, or of several lipid sheets substantially concentric, said sheet (s) encapsulating an aqueous phase E, characterized in that before the   formation of said niosomes, at least one non-ionic lipid (s) intended to constitute the sheets of niosomes is added to at least one cholesterol-phosphate in free acid form or neutralized by an ammonium, alkali or alkaline cation -terrous, at a rate of 1 to 40% by weight relative to the total weight of the lipid phase.   2 - Method according to claim 1, characterized   by the fact that a cholesterol-phosphate is used in aci, free or substituted or unsubstituted ammonium salt, sodium or potassium form.   3 - Method according to one of claims 1 or 2,   characterized in that, to obtain a dispersion of niosomes in the aqueous phase D, a plane lamellar phase is formed by introduction of the aqueous phase E into   liquid nonionic lipid, the aqueous phase D is then added and the mixture is vigorously stirred to produce the desired dispersion of niosomes.   4 - Method according to one of claims 1 to 3, characterized in that, as lipid (s) intended (s) for   constitute the sheets of the niosomes, at least one non-ionic amphiphile, of natural or synthetic origin, is chosen, comprising one or more long (s) per molecule   hydrocarbon chain (s) and one or more hydrophilic group (s).   - Method according to claim 4, characterized in that, as non-ionic amphiphile, at least one compound is chosen, taken from the group formed by: - polyglycerol ethers, linear or branched, of respective formulas: R- (OCH2-CH-CH28 - OH   OH and R40-CH2 -cH OH CH2OH n being an average statistical value between 1 and 6, R representing a linear or branched, saturated or unsaturated aliphatic chain containing 12 carbon atoms, hydrocarbon radicals of lanolin alcohols or the 2-hydroxyalkyl residues of 4-chain diols; - polyoxyethylenated fatty alcohols or polyoxyethylenated sterols; - polyol ethers, - polyol esters, oxyethylenated or not;   - glycolipids of natural or synthetic origin.   6 - Method according to one of claims 1 to 5,   characterized in that at least one additive taken from the group consisting of long chain alcohols and diols, sterols, long chain amines, hydroxyalkylamines, amines is added to the amphiphiles intended to form the niosomes polyoxyethylenated fatty acids, esters of long chain amino alcohols and their salts, phosphoric esters of fatty alcohols, alkyl sulfates, and   ionic derivatives of sterols other than cholesterol30 phosphates.   7 - Method according to one of claims 1 to 6,   characterized by the fact that, to constitute   the dispersion of spherules, from 0.5 to 25% by weight of nonionic amphiphilic (s) relative to the total weight of the dision persion of niosomes to be obtained.   8 - Method according to one of claims 1 to 7,   characterized by the fact that the aqueous phase E encapsulated in the niosomes is an aqueous solution of active substance (s), preferably isoosmotic with respect to phase D which surrounds the niosomes. 9 Method according to claim 8, characterized   by the fact that the aqueous phases D and E are identical.   - Method according to one of claims 8 or 9,   leading to a composition which can be used in cosmetics, characterized by the fact that at least one product taken from the group formed by humectants, artificial browning agents, water-soluble sunscreen agents is introduced into the aqueous phase E , antiperspirants, deodorants, astringents, refreshing products, toning products, healing products, keratolytic products, depilatory products, scented waters, water-soluble dyes, anti-dandruff agents, anti-dandruff agents seborrheic, oxidants,   reducers and extracts from animal or plant tissues. 20 11 Method according to one of claims 8 and 9,   leading to a composition which can be used in pharmacies, characterized in that at least one product taken from the group formed by the   vitamins, hormones, enzymes, vaccines, anti-inflammatory drugs, antibiotics and bactericides.   12 - Method according to one of claims 1 to 11,   characterized in that the dispersion of niosomes is mixed with at least one liquid phase L immiscible with water, intended to be dispersed in the aqueous phase D. 30 13 - Process according to claim 12, characterized in that that an amount of water-immiscible liquid phase of between 2 and 70% by weight relative to the total weight of the composition is introduced, the relative weighting proportion of constituent amphiphilic lipid (s) 35 of the niosomes with respect to the liquid phase immiscible with   the dispersed water being between 0.02 / 1 and iC / 1.   14 - Method according to one of claims 12 and   13, characterized in that the liquid phase immiscible with water dispersed in the aqueous phase D is chosen from the group consisting of oils such as fatty acid and polyol esters, and esters of fatty acids and branched alcohols of formula R4-COOR5, formula in which R4 represents the residue of a higher fatty acid containing from 7 to 19 carbon atoms and R5 represents a branched hydrocarbon chain containing from 3 to 20 carbon atoms , hydrocarbons such as hexadecane, paraffin oil, perhydrosqualene; halogenated carbides such as perfluorodecahydronaphthalene; perfluorotributylamine;   polysiloxanes; esters of organic acids; 15 ethers and polyethers.   - Method according to one of claims 1 to 14,   characterized by the fact that one introduces in the phase   aqueous D at least one adjuvant taken from the group formed by opacifiers, gelling agents, flavors, perfumes, sunscreen filters and colorants.   16 - Dispersion of niosomes in an aqueous medium D, said niosomes each consisting of a lipid sheet or of several substantially concentric lipid sheets, said sheet (s) encapsulating an aqueous phase E, characterized by the fact which is   obtained by the method according to one of claims 1 to 15.