Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Particulate form
Reexamination Certificate
2002-04-17
2004-05-11
Page, Thurman K. (Department: 1615)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Particulate form
C424S493000, C424S491000, C424S490000, C424S489000, C424S400000, C424S401000, C424S059000, C424S405000, C424S484000, C424S486000, C424S488000, C424S070900, C424S070100, C514S844000, C514S846000
Reexamination Certificate
active
06733790
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to the encapsulation of active principles and more particularly to new microcapsules, to a process for their production using various polymers and chitosans and to their use for the production of, for example, surface-active preparations.
PRIOR ART
“Microcapsules” are understood to be spherical aggregates with a diameter of about 0.1 to about 5 mm which contain at least one solid or liquid core surrounded by at least one continuous membrane. More precisely, they are finely dispersed liquid or solid phases coated with film-forming polymers, in the production of which the polymers are deposited onto the material to be encapsulated after emulsification and coacervation or interfacial polymerization. In another process, liquid active principles are absorbed in a matrix (“microsponge”) and, as microparticles, may be additionally coated with film-forming polymers. The microscopically small capsules, also known as nanocapsules, can be dried in the same way as powders. Besides single-core microcapsules, there are also multiple-core aggregates, also known as microspheres, which contain two or more cores distributed in the continuous membrane material. In addition, single-core or multiple-core microcapsules may be surrounded by an additional second, third etc. membrane. The membrane may consist of natural, semisynthetic or synthetic materials. Natural membrane materials are, for example, gum arabic, agar agar, agarose, maltodextrins, alginic acid and salts thereof, for example sodium or calcium alginate, fats and fatty acids, cetyl alcohol, collagen, chitosan, lecithins, gelatin, albumin, shellac, polysaccharides, such as starch or dextran, polypeptides, protein hydrolyzates, sucrose and waxes. Semisynthetic membrane materials are inter alia chemically modified celluloses, more particularly cellulose esters and ethers, for example cellulose acetate, ethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose and carboxymethyl cellulose, and starch derivatives, more particularly starch ethers and esters. Synthetic membrane materials are, for example, polymers, such as polyacrylates, polyamides, polyvinyl alcohol or polyvinyl pyrrolidone.
Examples of known microcapsules are the following commercial products (the membrane material is shown in brackets) Hallcrest Microcapsules (gelatin, gum arabic), Coletica Thalaspheres (maritime collagen), Lipotec Millicapseln (alginic acid, agar agar), Induchem Unispheres (lactose, microcrystalline cellulose, hydroxypropylmethyl cellulose), Unicerin C30 (lactose, microcrystalline cellulose, hydroxypropylmethyl cellulose), Kobo Glycospheres (modified starch, fatty acid esters, phospholipids), Softspheres (modified agar agar) and Kuhs Probiol Nanospheres (phospholipids).
Reference is also made in this connection to German patent application DE 19712978 A1 (Henkel) which describes chitosan microspheres obtained by mixing chitosans or chitosan derivatives with oil components and introducing the resulting mixtures into alkalized surfactant solutions. In addition, the use of chitosan as an encapsulating material for tocopherol is known from German patent application DE 19756452 A1 (Henkel).
The active principles are released from the microcapsules by mechanical, thermal, chemical or enzymatic destruction of the membrane, normally during the use of the preparations containing the microcapsules. Disadvantages in this regard are that the microcapsules do not allow controlled release of the active principles from their interior at all or only to an inadequate extent and that the capsules lack stability in the presence of surfactants, especially anionic surfactants. Accordingly, the problem addressed by the present invention was to overcome these disadvantages.
DESCRIPTION OF THE INVENTION
The present invention relates to microcapsules with mean diameters of 0.1 to 5 mm consisting of a membrane and a matrix containing at least one active principle and obtainable by
(a) preparing a matrix from gel formers, anionic polymers and active principles and
(b) introducing the matrix dropwise into aqueous chitosan solutions.
It has surprisingly been found that the use of thermogelling natural heteropolysacharides or proteins together with anionic polymers which form membranes in the presence of (cationic) chitosans enables new microcapsules distinguished by distinctly improved surfactant stability to be produced.
The present invention also relates to a process for the production of microcapsules with mean diameters of 0.1 to 5 mm consisting of a membrane and a matrix containing at least one active principle, characterized in that it comprises the steps of
(a) preparing a matrix from gel formers, anionic polymers and active principles and
(b) introducing the matrix dropwise into aqueous chitosan solutions.
Gel Formers
In the context of the invention, preferred gel formers are substances which are capable of forming gels in aqueous solution at temperatures above 40° C. Typical examples of such gel formers are heteropoly-saccharides and proteins. Preferred thermogelling heteropoly-saccharides are agaroses which may be present in the form of the agar agar obtainable from red algae, even together with up to 30% by weight of non-gel-forming agaropectins. The principal constituent of agaroses are linear polysaccharides of D-galactose and 3,6-anhydro-L-galactose with alternate &bgr;-1,3- and &bgr;-1,4-glycosidic bonds. The heteropolysaccharides preferably have a molecular weight of 110,000 to 160,000 and are both odorless and tasteless. Suitable alternatives are pectins, xanthans (including xanthan gum) and mixtures thereof. Other preferred types are those which—in 1% by weight aqueous solution—still form gels that do not melt below 80° C. and solidify again above 40° C. Examples from the group of thermogelling proteins are the various gelatines.
Anionic Polymers
Preferred anionic polymers are salts of alginic acid. The alginic acid is a mixture of carboxyl-containing polysaccharides with the following idealized monomer unit:
The average molecular weight of the alginic acid or the alginates is in the range from 150,000 to 250,000. Salts of alginic acid and complete and partial neutralization products thereof are understood in particular to be the alkali metal salts, preferably sodium alginate (“algin”) and the ammonium and alkaline earth metal salts. Mixed alginates, for example sodium/magnesium or sodium/calcium alginates, are particularly preferred. In an alternative embodiment of the invention, however, anionic chitosan derivatives, for example the carboxylation and above all succinylation products described, for example, in German patent DE 3713099 C2 (L'Oréal) and German patent application DE 19604180 A1 (Henkel) are also suitable for this purpose.
Active Principles
Basically, the choice of the active principles encapsulated in the new microcapsules is not critical. They are preferably substances which are only released by mechanical destruction of the microcapsules. In cases such as these, the function of the microcapsules is to prevent contact between the surrounding environment and the active principle and, hence, chemical reaction and degradation. It may be that the encapsulated substances are not to be released at all and merely serve the purpose of providing the preparation with an aesthetic appearance. This often applies, for example, to dyes. It is of course clear that these forms of use may also exist alongside one another. More particularly, it is possible for example to encapsulate a perfume to be subsequently released together with a pigment which provides the capsule with a particular appearance.
Active principles for Cosmetic and Pharmaceutical Applications
Typical examples of active principles used in cosmetic and pharmaceutical preparations are surfactants, cosmetic oils, pearlizing waxes, stabilizers, biogenic agents, vitamins, deodorants, antiperspirants, antidandruff agents, UV protection factors, antioxidants, preservatives, insect repellents, self-tanning agents, tyrosine inhib
Bennett Rachel M.
Cognis Iberia S. L.
Drach John E.
Ettelman Aaron R.
Page Thurman K.
LandOfFree
Microcapsules and processes for making the same using... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Microcapsules and processes for making the same using..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Microcapsules and processes for making the same using... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3250543