Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Liposomes
Reexamination Certificate
1999-06-09
2002-08-27
Kishore, Gollamudi S. (Department: 1615)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Liposomes
C424S401000, C424S070100, C424S070200, C424S070110, C424S070210, C424S070220, C424S073000, C514S881000, C514S937000
Reexamination Certificate
active
06440456
ABSTRACT:
The present invention relates to novel carrier systems based on organic phospholipids capable of forming bilayers in aqueous solution, nonionic surfactants, amphoteric surfactants and suspending agents, wherein these carrier systems allow lipophilic materials to be incorporated into aqueous solutions.
Organic phospholipids play an important role in the cosmetics and pharmaceutical industries because of their outstanding physiological properties, such as, for example, emulsifying, softening, and anti-oxidant effects. When hydrolyzed, organic phospholipids yield phosphoric acid, an alcohol, a fatty acid, and a nitrogenous base. Most phospholipids are amphipathic, i.e., have polar “heads” and non-polar “tails.” As a result, most phospholipids tend to arrange spontaneously into a bilayer when suspended in an aqueous environment, with the polar heads contacting the water and the non-polar tails contacting each other. Most naturally occurring phospholipids prefer to form vesicular bilayers in water solutions. In such a bilayer vesicle, no non-polar part of the phospholipid has any contact with the water solution.
Because of their non-polar portions, phospholipids typically are water-insoluble and incompatible with many water soluble anionic compounds, such as anionic surfactants. While they can be solubilized in water at low levels by a range of surfactants, this is often not easily accomplished.
Instead, solubilization has been accomplished conventionally using specific solubilizing agents in aqueous alcoholic solutions. For example, U.S. Pat. No. 4,874,553 to Hager et al. discusses methods of rendering phospholipid mixtures water-soluble or water-dispersible by using certain amine compounds as solubilizing agents. U.S. Pat. No. 4,174,296 to Kass describes a method of improving the solubility of phospholipid compounds in water, in particular lecithin compounds, by mixing lecithin with specific single solubilizing agents, including amphoteric and anionic surfactants. These methods utilize alcohol for cosolubilization. Alcohol solutions can have the drawback of disrupting any bilayer formation by altering the solution such that the alcohol functions as a secondary solvent.
Lecithins and other phospholipids have been used in the pharmaceutical industry to formulate carriers for water-insoluble drugs. For instance, in U.S. Pat. No. 5,173,303 to Lau et al., water-insoluble material is encapsulated by vesicles composed of phospholipids such as lecithin. Ribosa et al., in “Physico-chemical modifications of liposome structures through interaction with surfactants,”
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Int'l Journal of Cosmetic Science 14:131-149 (1992), also discuss solubilization of phospholipids via the interaction of liposomes with surfactants. Lau and Ribosa, however, investigated only dilute solutions of pure liposomes.
Despite difficulties in solubilization, certain organic phospholipids, such as lecithin, can advantageously give hair and skin a soft, moisturized feel because they have a strong affinity for the hydrophobic surface of the hair and skin. In addition, lipophilic ingredients, including hydrocarbons such as petrolatum, offer moisturizing and protecting properties that are also desirable in many applications including hair care and skin care. However, in addition to the difficulties encountered in solubilizing phospholipids, the incorporation of high concentrations or “loads” of lipophilic ingredients into an aqueous environment has proven difficult. The water-insoluble nature of the these ingredients has made their utilization in aqueous environments complicated. It would thus be desirable for cosmetic and pharmaceutical applications to provide delivery systems that include such organic phospholipids as carriers for high loads of other lipophilic ingredients, without the need for alcohols and other similar solvents.
For the most part, the use of hydrocarbons such as petrolatum in hair care and skin care has been accomplished through the use of water-in-oil emulsions, encapsulating lipids and other multi-phase compositions. For example, U.S. Pat. No. 5,716,920 to Glenn et al. describes a method of making a liquid personal cleaning composition that contains a lipophilic skin moisturizing agent such as hydrocarbon oils and waxes by the use of an encapsulation technique. However, the methods described result in a multi-phase emulsion or composition comprised of droplets.
Thus, there remains a need for an aqueous delivery system that can solubilize and/or form a stable suspension (i.e., without phase separation) with lipophilic materials such as hydrocarbons, waxes, and silicones, where these lipophilic materials will remain stable and/or not precipitate out of solution, where the amount of deposition of lipophilic material can be controlled, and where the system could carry other ingredients in addition to the lipophilic ingredient. For example, it would be beneficial to have a system which incorporates lipophilic materials into compositions containing other ingredients, such as dyeing and permanent wave compositions. The present invention provides such a delivery system.
To achieve these and other advantages, the present invention is drawn to a composition made up of at least one organic phospholipid capable of forming bilayers in aqueous solution, at least one amphoteric surfactant, at least one nonionic surfactant, and at least one suspending agent or viscosity increasing agent. The nonionic surfactant is present in an amount equal to or greater than the amount of the organic phospholipid. The suspending agent is present in an amount effective for maintaining a stable composition. A stable composition or system is one that experiences substantially no settling out or phase separation.
In another embodiment, the present invention relates to an aqueous delivery system for lipophilic materials. The delivery system (or “carrier”) includes the above-described composition in addition to at least one lipophilic ingredient, and an aqueous phase. The nonionic surfactant preferably is present in an amount equal to or greater than the amount of the organic phospholipid. The organic phospholipid, the amphoteric surfactant, and the nonionic surfactant are present in a combined amount sufficient to allow the lipophilic ingredient to be incorporated into the delivery system by the composition of the present invention. The suspending agent is present in an amount effective for maintaining a stable delivery system, i.e. one that experiences substantially no settling out or phase separation.
In a preferred embodiment, the delivery system of the present invention results in a stable, milky suspension, solution, lotion, or cream. A delivery system comprising at least one organic phospholipid capable of forming bilayers in aqueous solution, at least one amphoteric surfactant, at least one nonionic surfactant, at least one water-insoluble ingredient, and an aqueous phase has been described previously. See WO 98/56333. This system is referred to as the “LAN” because it preferably contains a lecithin (L) as the phospholipid, an amphoteric surfactant (A), and a nonionic surfactant (N). The LAN system previously described “solubilized” a water-insoluble ingredient resulting in a clear or cloudy solution. However, the LAN system of the present invention is different in that, by containing a suspending or viscosity increasing agent, it enables a lipophilic ingredient to be incorporated into the system to give a stable, milky suspension, solution, lotion, or cream.
A milky solution is not equivalent to a cloudy solution. For example, a cloudy solution is a solution that contains small particles, is turbid, will experience settling over time and/or will experience separation/precipitation of phases. The stable milky solution of the present invention generally does not settle over time and typically, experiences no separation of phases. Like the previously disclosed LAN clear solution system, the milky LAN system of the present invention will incorporate or act as a carrier for lipophilic materials. However, the LAN system of the
Cannell David W.
Nguyen Nghi Van
Finnegan Henderson Farabow Garrett & Dunner LLP
Kishore Gollamudi S.
L'Oreal (S.A.)
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