Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Particulate form
Reexamination Certificate
2001-05-07
2003-03-11
Dees, Jose′ G. (Department: 1616)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Particulate form
C424S059000, C424S070800, C424S401000, C424S451000, C424S455000, C424S457000, C424S489000, C424S494000, C424S497000, C424S498000, C424S501000, C424S502000
Reexamination Certificate
active
06531160
ABSTRACT:
The present invention relates to microcapsules with an aqueous core containing at least one water-soluble cosmetic or dermatological active principle, to cosmetic or dermatological compositions containing them and to a process for preparing such microcapsules.
The microencapsulation of cosmetic or dermatological active agents to allow better storage and/or sustained and controlled release is known.
Microencapsulation processes and the principles upon which they are based are described in detail, for example, in <<Microencapsulation, Methods and Industrial Application>>, edited under the direction of Benita, M. Dekker, 1996.
All these processes are based on the use of polymers as constituent elements of the wall of the microparticle which isolates the active agent from the external medium. These microparticles make it possible to encapsulate higher levels of water-soluble active agents than do other vesicular systems such as liposomes, which are nanoparticles formed from phospholipid bilayers surrounding an aqueous core.
It has thus been sought to encapsulate various hydrophilic active agents. Among these, ascorbic acid is of most particular interest, since its instability in aqueous medium makes it difficult to formulate in cosmetic compositions, although it has many beneficial properties.
Specifically, on account of its chemical structure (&agr;-keto lactone), ascorbic acid is highly sensitive to certain environmental parameters such as light, oxygen or water. This results in a rapid degradation of the ascorbic acid formulated in the presence of these agents. This instability is liable to impair its efficacy, although it is an active agent of choice for stimulating the synthesis of connective tissue and in particular of collagen, for reinforcing skin tissue defenses against external attack such as ultraviolet radiation and pollution, for compensating for a vitamin E deficiency of the skin, for depigmenting the skin and for trapping free radicals. In particular, these properties make it an excellent candidate as a cosmetic or dermatological active agent for combating or preventing ageing of the skin.
Among the techniques for encapsulating hydrophilic active principles such as ascorbic acid, in dissolved, dispersed or pulverulent form, mention may be made of coacervation (JP-8 325 117, JP-5 285 210 and U.S. Pat. No. 4,460,563), spray-drying (U.S. Pat. No. 5,767,107), air-bed fluidization (WO 95/27488 and EP 0 600 775) or interfacial polymerization (JP 1 043 343, WO 91/01801 and WO 94 23832).
The main drawback of spray-drying and air-bed fluidization is that of encapsulating the active agent in the form of powder, i.e. in solid form. Now, it is often essential in cosmetics or dermatology to encapsulate the active agent in dissolved form in an aqueous medium to ensure its immediate bioavailability to the skin.
The techniques of coacervation or of interfacial polymerization are not suitable for the microencapsulation of water-soluble cosmetic or dermatological active principles since they generally involve the use of polymerizable or bifunctional reagents that are toxic to the skin and liable to react with the active agent to be encapsulated and deactivate it.
Another microencapsulation process has also been used to encapsulate dissolved hydrophilic active agents in microparticles. This is the <<multiple emulsion-solvent evaporation or extraction>> technique, which consists in preparing a water-in-oil primary emulsion by dispersing an aqueous solution of the active principle in an organic solution of a water-insoluble polymer, followed by dispersing this primary emulsion in an outer aqueous phase, in a second stage. The organic solvent is then removed by evaporation or extraction.
This process is disclosed in U.S. Pat. Nos. 3,523,906, 3,523,907, EP 190 833 and WO 95/28149.
U.S. Pat. Nos. 3,523,906 and 3,523,907 disclose, respectively, a multiple emulsion-evaporation process and a multiple emulsion-extraction process using, as polymers constituting the wall of the microcapsules, vinyl polymers or copolymers, polycondensates such as polycarbonates, polyesters, polysulphonates, polyurethanes or polyamides, or natural polymers such as chlorinated natural rubber or cellulose derivatives.
Patent application EP 190 833 discloses a process for encapsulating water-soluble active principles by multiple emulsion-solvent evaporation using water-insoluble biocompatible polymers, and in particular polymers based on lactic acid and on glycolic acid.
Patent application WO 95/28149 discloses the preparation, via a multiple emulsion-evaporation process, of microcapsules having a wall consisting of a copolymer of poly(lactide-co-glycolide) type.
Now, the Applicant has found that the polymers mentioned in the above documents are not suitable for stabilizing active principles either because their hydrolysis in aqueous medium is reflected by the release of organic acids which modify the pH of the composition, or because they do not allow satisfactory degrees of encapsulation to be obtained.
The problem underlying the present invention is consequently that of developing novel microcapsules which contain, in their envelope, polymers that are stable in aqueous medium and produce satisfactory degrees of encapsulation of water-soluble active principles.
Another problem—which is specific to the encapsulation of cosmetic active principles—is associated with the presence of water in cosmetic compositions.
Specifically, the presence of an aqueous phase outside the microcapsules necessitates excellent impermeability of the wall of these microcapsules in order to prevent the active principle from passing into the outer aqueous phase, which would negate all the benefits of the encapsulation. Thus, in the cosmetic field, microcapsules with an impermeable wall which release the active principle only after application, for example following the rupture or biodegradation of the envelope, are generally sought.
This problem does not arise in the pharmaceutical field, in which the microcapsules are generally kept in dried form and need to release the active principle rapidly after they have been placed in contact with an aqueous medium.
The Applicant has discovered that it is possible to solve the problems listed above, i.e. to obtain, with satisfactory degrees of encapsulation, microcapsules consisting of an envelope containing an aqueous solution of at least one stabilized cosmetic or dermatological active principle by appropriately selecting the materials forming the envelope from certain polymers and/or certain waxes.
A subject of the present invention is thus microcapsules with an aqueous core containing at least one water-soluble cosmetic or dermatological active principle, and with a polymeric and/or waxy envelope consisting
of at least one polymer chosen from polycaprolactone, poly(3-hydroxybutyrate), poly(ethylene adipate), poly(butylene adipate), cellulose esters of at least one C
1
-C
4
carboxylic acid, preferably mixed cellulose esters of two types of carboxylic acid, copolymers of styrene and of maleic anhydride, copolymers of styrene and of acrylic acid, styrene-ethylene/butylene-styrene block terpolymers, styrene-ethylene/propylene-styrene block terpolymers and terpolymers of ethylene, of vinyl acetate and of maleic anhydride, and/or
of at least one wax chosen from beeswax, polyglycerolated beeswax, hydrogenated plant oils, paraffin with a melting point above 45° C., and silicone waxes.
For the purpose of the present invention, a wax is a lipophilic compound which is solid at room temperature (about 25° C.), undergoes a reversible solid/liquid change of state, has a melting point above about 40° C., which may be up to 200° C., and has an anisotropic crystal organization in the solid state.
Silicone waxes which may be mentioned, for example, are alkyl- or alkoxydimethicones containing from 16 to 45 carbon atoms, for example behenoxydimethicone and alkyl esters of C
16
-C
45
dimethiconol, for instance dimethiconol behenate.
The subject of the present invention is also cosmetic or d
Biatry Bruno
Lheureux Eric
Dees Jose′ G.
Jacobson & Holman PLLC
L′Oreal
Lamm Marina
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