CH623236A5 - Dispersion of lipid spherules - Google Patents

Description

The object of the present invention, which aims to remedy the aforementioned drawbacks, is: a) the dispersion of lipid spherules defined in claim 1 and b) the process defined in claim 9, for obtaining such a dispersion.

The spherules of the dispersion according to the invention can encapsulate active substances with a high encapsulation yield. Within the meaning of the present description, the word encapsulate is used to indicate that there is an aqueous phase inside a capsule constituted by the lipid spherules.

In a preferred embodiment, the aqueous phase to be encapsulated is an aqueous solution of active substance; the active substances of the aqueous phase to be encapsulated are products with cosmetic, pharmaceutical or food action; the continuous phase of the dispersion is an aqueous phase; the proportion of the weight of the spherules relative to the weight of the continuous phase of the dispersion is between 0.01 and 0.5 approximately; the continuous phase of the dispersion is advantageously iso-osmotic with respect to the aqueous phase encapsulated in the spherules.

The active substances, which can be encapsulated in the spherules defined above, are extremely varied and correspond to those which will be indicated below for the implementation of the method according to the invention. As a result, the compositions can be used in various fields and, in particular, in the field of the food industry, the pharmaceutical industry or the cosmetic industry.

The aqueous dispersions defined above are of particular interest in cosmetics, due to the fact that the use of large spherules makes it possible to reduce the risks of passage of these preparations through the skin.

It should be noted that the use of the aqueous dispersions according to the invention in cosmetics has a considerable advantage.

623,236

compared to the well known use of emulsions. In fact, when it is desired to use preparations containing both fatty substances and water, it is necessary, to ensure the stability of the emulsion, to use amphiphilic emulsifying compounds to ensure the stability of the dispersions . It is known that certain emulsifiers can be relatively irritating when applied to the skin. It has been discovered, in the course of work relating to the present invention, that this effect of emulsifiers, for a given chemical structure, depends considerably on the form in which they are applied. Thus, we were able to highlight the fact that a water / oil emulsion composed of 42% perhydrosqualene, 8% emulsifier and 50% water is highly irritating, while an aqueous dispersion at 8% of the same emulsifier has a practically insignificant index of irritation and that perhydrosqualene is absolutely harmless. As a result, there is a synergy of irritation when an emulsifier and an oil phase are present. The aqueous dispersions according to the invention make it possible to avoid the simultaneous use of an emulsifier and an oil, which constitutes significant progress in the field of cosmetics.

It should be noted that it is possible to add to the dispersions of spherules according to the invention various auxiliary products intended to modify the presentation or the organoleptic characters, such as opacifiers, gelling agents, flavors, perfumes or dyes.

Generally, the advantage of the dispersions according to the invention lies in the fact that they make it possible to introduce hydrophilic substances into an essentially lipophilic medium. It follows that, under these conditions, these are masked, hence a protective effect with respect to the various possible alteration agents: oxidants, digestive juices and, more generally, reactive compounds with respect to -vis encapsulated substances. The penetration and / or fixation of active substances can be modulated by varying the size of the globules and their electrical charge. Their action can also be postponed (delay effect). In addition, the fact that they are masked makes it possible to suppress or substantially alter their organoleptic characters, in particular the taste. Finally, the lipids used in these preparations have, by themselves, a beneficial action, for example emollience, lubrication, polishing.

In a preferred embodiment of the process according to the invention, the weight ratio between the quantity of aqueous phase to be encapsulated brought into contact with the lipids and the quantity of lipids forming the lamellar phase is between approximately 0.1 and 3 about ; the aqueous phase to be encapsulated can be water or an aqueous solution of active product; the weight ratio of the quantity of dispersion phase, which is added, to the quantity of lamellar phase, which is dispersed, is between approximately 2 and approximately 100; the dispersion phase and the aqueous phase to be encapsulated are preferably iso-osmotic; the dispersion phase can advantageously be an aqueous solution; the agitation carried out as the last phase of the process is obtained by means of a shaker; the process is carried out at room temperature or at a higher temperature if the lipid is solid at room temperature; if it is desired that the spherules obtained have an average diameter of less than 1000 Å, the dispersion of spherules may be subjected to an ultrasound treatment.

To form the lamellar phase, a single lipid or a mixture of lipids can be used. The lipid (s) which are used comprises (s) a long lipophilic chain comprising from 12 to 30 carbon atoms, saturated or unsaturated, branched or linear; in particular, it is possible to choose oleic, lanolic, tetra-decyl, hexadecyl, isostearyl, lauric or alkylphenyl chains. As the lipid forming the lamellar phase, it is advantageous to choose an amphoteric compound comprising two lipophilic chains or a combination of two long-chain organic ions of opposite signs.

It is possible to use an aqueous phase to be encapsulated comprising active substances of all kinds and, in particular, substances having a pharmaceutical or food interest, or substances

3

5

10

15

20

25

30

35

40

45

50

55

60

65

623,236

4

having cosmetic activity. The active substances can be, for example, with regard to cosmetics; products intended for skin and hair care, for example humectants, such as glycerin, sorbitol, pentaerythritol, inositol, pyrrolidonecarboxylic acid and its salts; artificial browning agents such as dihydroxyacetone, erythrulose, glyceral dehyde, γ-dialdehydes such as tartaric aldehyde (these products possibly being associated with dyes); water-soluble sunscreen agents; antiperspirants, deodorants, astringents, refreshing, tonic, healing, keratolytic, depilatory products; scented waters; extracts of animal or plant tissues, such as proteins, Polysaccharides, amniotic fluid; water-soluble dyes, anti-dandruff agents, antiseborrhoeic agents, oxidants (bleaching agents) such as hydrogen peroxide, reducers such as thioglycolic acid and its salts. As pharmaceutical active substances, mention may be made of vitamins, hormones, enzymes (for example, superoxide dismutase), vaccines, anti-inflammatories (for example hydrocortisone), antibiotics, bactericides.

It is clear that we will choose, depending on the active substance contained in the aqueous phase to be encapsulated, lipids capable of stably encapsulating the aqueous phase considered. In order for the lipids constituting the lamellar phase to give stable spherules, it is necessary that there is a sufficient lateral interaction between the lipid chains which, placed side by side, constitute the layers or sheets of the spherules, that is to say -to say that the Van der Waals forces between the chains ensure sufficient cohesion of the sheets. This condition is satisfied for lipids having the characteristics indicated in the general definition of the process given above. The lipids which can be used in the process according to the invention belong to the class of emulsifiers of the water in oil type.

The following examples illustrate the invention.

Example 1

In a 50 ml round flask, 300 mg of sphingomyelin is brought into contact with 0.350 ml of a 0.3M solution of glucose, and the mixture is homogenized. The experiment is carried out at room temperature.

5 ml of a 0.145M NaCl solution are then added. The flask, placed on a shaker, is shaken vigorously for 2 h.

The dispersion obtained is milky; the diameter of the spherules is approximately 2 ji.

The dispersion can be subjected to ultrasound for 1 hour in order to reduce the diameter of the spherules.

Example 2

Into a 50 ml round flask, 300 mg of the product obtained by molecular distillation, of general formula, are intimately mixed:

r- / och2-ch voh

I

\ ch2oh.

R being the alkyl radical of oleic alcohol and n being equal to 2; 150 mg of cholesterol; 50 mg of an amine of general formula:

c2h5

rc00 (ch2ch20) n-ch2ch2n ^

C2H5

RCOO being the remainder of the copra and n being a number between 2 and 5, and the mixture obtained is brought into contact with 0.5 ml of a 0.3M solution of sorbitol; the mixture is homogenized. The experiment is carried out at room temperature.

Then 4 ml of a 0.145 M KCl solution is added. The flask, placed on a shaker, is shaken vigorously for 4 h.

The dispersion obtained is opalescent; the diameter of the spherules is about 2 | i.

Example 3

5 In a 50 ml round flask, 425 mg of the product, of general formula:

r- / och2- ch-

oh ch, oh.

R being the alkyl radical of oleic alcohol and n being a number equal to 2, and 75 mg of an amine of the following formula:

R- / OCH2-CH 15 V CH2OH / n

£

-OCH, CHOH-CH, N

R being the oleyl radical and n having a mean statistical value of 1, with 0.5 ml of a 0.3M solution of glucose, and the mixture is homogenized. The experiment is carried out at room temperature. Then 4 ml of a 0.145 M solution (NaCl, KCl) is added. The flask, placed on a shaker, is shaken vigorously for 4 h.

The dispersion obtained is opaque; the diameter of the spherules is greater than 2 | i.

The dispersion can be subjected to ultrasound, the size of the spherules then becoming less than one micron.

Example 4

In a 50 ml round flask, 300 mg of sphingomyelin are brought into contact with 0.350 ml of a 0.3M solution of ascorbic acid, and the mixture is homogenized. The experiment is carried out at room temperature.

2.650 ml of a 0.145 M solution of KCl are then added. The flask, placed on a shaker, is shaken vigorously for 4 h. The dispersion obtained is milky; the diameter of the spherules is about 2 | i.

If desired, the dispersion can be filtered on a column of Sephadex G 50 coarse gel swollen in 0.145 M KCl solution.

40

Example 5

In a 50 ml round flask, 142 mg of the Na salt of N2- (alkylsuif) -N dodecyl-N- (N ', N'-diethylaminoethyl) asparagine are dissolved in 2 ml of a chloroform / methanol mixture in the report 2/1. The solvent is evaporated using an evaporator

45 rotary, then the last traces of solvent are removed by subjecting the product for 1 h to the reduced pressure given by a vane pump.

10 ml of a 0.3M glucose solution are brought into contact with the lipid.

5o The balloon, placed on a shaker, is strongly agitated for 4 h. The experiment is carried out at room temperature. The size of the spherules is approximately 1 | i. The dispersion is then filtered on a column of Sephadex G 50 coarse gel swollen in a 0.145 M NaCl solution.

55 Example 6

In a 50 ml flask, 80 mg of the product of general formula are dissolved:

R- / OCH2-CH VOH

60 x CH2OH / n

R being the hexadecyl radical and n being equal to 2.10 mg of cholesterol and 10 mg of diketylphosphate in 2 ml of a chloroform / methanol mixture in the ratio 2/1.

The solvent is evaporated using a rotary evaporator and the last traces of solvent are removed by passage through the vane pump for 1 h.

10 ml of a 0.15M solution of the sodium salt of pyroglutamic acid are brought into contact with the lipids. The ball, put on a

5

623,236

shaker, is stirred vigorously for 2 h in a water bath at 55 ° C, then gradually cooling until it returns to room temperature.

The dispersion is subjected to ultrasound for 1 h at a temperature maintained near room temperature. The dispersion is then filtered on a column of Sephadex G 50 coarse gel swollen in distilled water.

The dispersion obtained is fluid and clear after passing through the ultrasound; the diameter of the spherules is less than 1 | i.

Example 7

In a 50 ml round flask, 200 mg of the product of general formula are intimately mixed:

och2-ch v-oh

I) 15

ch2oh / „

R being the hexadecyl radical and n being equal to 2.25 mg of cholesterol and 25 mg of diketylphosphate; the mixture obtained is brought into contact with 0.3 ml of a 10% tartaric aldehyde solution and the mixture is homogenized. The experiment is carried out at 55 ° C. Then 4.7 ml of a 0.145 M solution of KCl is added.

The flask, placed in a water bath, is stirred vigorously using a shaker for 2 h at 55 ° C, then gradually cooling until it returns to room temperature.

The dispersion obtained is gelled and slightly bluish in appearance.

The simultaneous application to the skin of this dispersion of niosomes and of an aqueous solution with the same final concentration of tartaric aldehyde makes it possible to appreciate two effects of the niosomes which, considerably reinforcing the developed coloration, clearly improve the resistance of this coloration to washing with water and detergents.

R

Claims (19)

623,236 1. Dispersion of spherules consisting of organized molecular layers enclosing an aqueous phase to be encapsulated, these layers consisting of at least one lipid compound of formula X — Y, X denoting an ionic hydrophilic group and Y a lipophilic group, characterized by the fact that the spherules have a diameter between 1000 and 50,000 Å. 2. Dispersion according to claim 1, characterized in that the continuous phase of the dispersion is an aqueous phase. 3. Dispersion according to one of claims 1 or 2, characterized in that the proportion of the weight of the spherules relative to the weight of the continuous phase of the dispersion is between 0.01 and 0.5. 4. Dispersion according to one of claims 1 to 3, characterized in that the continuous phase of the dispersion is iso-osmotic with respect to the aqueous phase encapsulated in the spherules. 5. Dispersion according to one of claims 1 to 4, characterized in that the aqueous phase to be encapsulated is an aqueous solution of active substance with cosmetic action. 6. Dispersion according to claim 5, usable in cosmetics, characterized in that the aqueous phase encapsulated in the spherules contains at least one product taken from the group formed by humectants, such as glycerin, sorbitol, penta-erythritol , inositol, pyrrolidonecarboxylic acid and its salts, artificial browning agents such as dihydroxyacetone, erythrulose, glyceraldehyde, y-dialdehydes such as tartaric aldehyde, these products possibly being associated with dyes; water-soluble sunscreen agents; antiperspirants, deodorants, astringents, refreshing, tonic, healing, keratolytic, depilatory products; scented waters; extracts of animal or plant tissues, such as proteins, Polysaccharides, amniotic fluid; water-soluble dyes, anti-dandruff agents, antiseborrhoeic agents, oxidants such as hydrogen peroxide, reducers such as thioglycolic acid and its salts. 7. Dispersion according to one of claims 1 to 5, usable in pharmacy or in the food industry, characterized in that the aqueous phase encapsulated in the spherules contains at least one pharmaceutically active agent or a food adjuvant. 8. Dispersion according to one of claims 1 to 7, characterized in that it contains at least one product chosen from opacifiers, gelling agents, flavors, perfumes and dyes. 9. Method for obtaining a dispersion of spherules according to claim 1, characterized in that, on the one hand, at least one liquid lipid dispersible in water and having the general formula: X-Y formula in which X represents an ionic hydrophilic group and Y represents a lipophilic group and, on the other hand, the aqueous phase to be encapsulated in the spherules, the lipophilic / hydrophilic ratio of the lipid being such that the latter swells in the aqueous phase to be encapsulated , to form a lamellar phase; that is stirred to ensure mixing and to obtain a lamellar phase; that a dispersion liquid is then added in an amount greater than the amount of lamellar phase obtained and that is vigorously shaken for a time varying from 15 min to 3 h. 10. Method according to claim 9, characterized in that the weight ratio between the quantity of aqueous phase to be encapsulated brought into contact with the lipids and the quantity of lipids forming the lamellar phase is between 0.1 and 3. 11. Method according to one of claims 9 or 10, characterized in that the aqueous phase to be encapsulated is water. 12. Method according to one of claims 9 or 10, characterized in that the aqueous phase to be encapsulated is an aqueous solution of active product. 13. Method according to one of claims 9 to 12, characterized in that the weight ratio of the amount of dispersion phase, which is added, to the amount of lamellar phase, which is dispersed, is included between 2 and 100. 14. Method according to one of claims 9 to 13, characterized in that the dispersion phase and the aqueous phase to be encapsulated are iso-osmotic. 15. Method according to one of claims 9 to 14, characterized in that the dispersion phase is an aqueous solution. 16. Method according to one of claims 9 to 15, characterized in that it is implemented at a temperature at least equal to the melting temperature of the lipid. 17. Method according to one of claims 9 to 16, characterized in that the lipid (s) used (s) comprises (s) a lipophilic chain comprising from 12 to 30 carbon atoms. 18. Method according to claim 17, characterized in that the lipid (s) used) is (are) chosen (s) from the group formed by lipids comprising an oleic, lanolic, tetradecylic, hexadecylic, isostearyl chain, lauric or alkylphenyl. 19. Method according to one of claims 17 or 18, characterized in that the lipid forming the lamellar phase is an amphoteric compound comprising two lipophilic chains or is a combination of two long-chain organic ions of opposite signs. 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 multimolecular layers and preferably by bimolecular layers having approximate thickness of 30-100 Å (see, in particular, the article by Bangham, Standish and Watkins, "J. Mol. Biol.", 13.238 (1965). Until now, it has been possible to obtain lipid spherules consisting of concentric sheets only by using lipids comprising an ionic hydrophilic group and a lipophilic group and the preparation processes, which have been described, entail the production of spherules with an average diameter of less than 1000 Å. The process for obtaining these spherules consists in producing a dispersion, the dispersed phase of which contains the lipid substance capable of forming the spherules, and in subjecting this dispersion to a treatment by ultrasound; to achieve the dispersion which is subjected to ultrasound, it is possible, firstly, to produce on a wall, by evaporation, a thin film of the lipid substance to be dispersed, then, secondly, to bring into contact with the wall thus coated the continuous phase of the dispersion to be produced and finally, thirdly, shake to obtain the dispersion to be subjected to ultrasound. In another process described in French patent application No. 2221122, it is also possible, to obtain the dispersion to be subjected to ultrasound, add the lipid intended to form the walls of spherules to an aqueous phase, then heat slightly and stir. vigorously by shaking. The spherules, made up of concentric sheets which are obtained in this way and which have a maximum diameter of approximately 1000Å, are generally called liposomes. It has already been proposed to use liposomes to enclose aqueous solutes containing active substances in the aqueous compartments comprised between the lipid double layers and thus to protect the encapsulated substances against external conditions (see, in particular, the article Sessa and Weismann, "J. Lipid Res.", 9.310 (1968) and Magee and Miller, "Nature", vol. 235 (1972). Liposomes can vary in size in the range less than 1000 Å, vary their power of penetration into the human body, which has made it possible to envisage many uses on the pharmaceutical level, all the more 2 5 10 15 20 25 30 35 40 45 50 55 60 65 more than their external electrical charge can make it possible to choose their site of fixation ("Biochem. J." (1971), 124 p. 58 P). However, cosmetically, the use of spherules with a diameter of less than 1000 Å is likely to cause some disadvantages due to the risk of penetration of the products through the skin. It is therefore clear that at least for this type of application, it would be desirable to be able to produce spherules with concentric lipid sheets having a diameter greater than 1000 Å. In addition, the methods currently known for obtaining liposomes containing active substances between their concentric lipid sheets have considerable drawbacks: first, the active substance, placed in the continuous phase of the dispersion which is subjected to ultra -sons, is encapsulated between the lipid sheets of the liposomes only for a very small part, because a very small part of the continuous phase of the dispersion is trapped between said sheets. When it is desired to isolate the encapsulation liposomes, it is necessary to pass the dispersion, which has been subjected to ultrasound, over a separation column of the Sephadex type, in which case the liposomes are found in the form of an extremely dilute dispersion. It follows that, on the one hand, it is practically not possible, with known methods, to obtain a high concentration of liposomes and that, on the other hand, the active substance is encapsulated only in a low proportion and is lost in the elution of the separation column without it being practically possible to recover it in a simple manner, which leads to a significant increase in the cost price of the active substances encapsulated in the liposomes. It is therefore desirable to have a process for manufacturing spherules with concentric sheets which allows obtaining a dispersion with a high concentration of spherules with a reduced loss of the product encapsulated between the sheets of spherules. Finally, the methods for manufacturing liposomes which have been described to date mention that only certain well-defined categories of lipids can be used: in the state of the art cited above, the use of phospholipids, lipids comprising an ionic hydrophilic group and a lipophilic group, and unsaturated fatty acids.