FIELD OF THE INVENTION

The invention concerns the field of (dried) capsules with a high active ingredient or active substance content, their use in cosmetic and/or pharmaceutical compositions, and the production of said capsules.

PRIOR ART

Encapsulations or enclosures of active ingredients, in particular flavoring agents or fragrances or cosmetic or pharmaceutically active ingredients, belong to prior art, and often provide the possibility of stabilizing the encapsulated or enclosed material and protecting it from reactions with the medium in order to obtain the effect of the active ingredient and slowly release it. There are various possibilities for encapsulation materials. A matrix material known to the person skilled in the art is alginate.

Alginates are linear polysaccharides whose monomeric building blocks are β-D-mannuronate and α-L-guluronate. The β-D-mannuronate and α-L-guluronate radicals in the alginate are linked to one another via 1,4-glycosidic bonds and form sequences with homopolymers and an alternating structure. The degree of polymerization is between 100 and 3000, which corresponds to a molar mass of 20,000 to 600,000 u. The homopolymer sequences are classified into two different categories: while the so-called “MM blocks” are composed of β-1,4-glycosidically linked D-mannuronate radicals, the “GG blocks” contain L-guluronate radicals having α-1,4-glycosidic bonds. In the third alginate block type, the sequence with the alternating structure and the D-mannuronate and L-guluronate radicals are alternately linked to one another via β-1,4 and α-1,4-glycosidic bonds. As a result, all four possible types of glycosidic bonds are present in the alginate: diequatorial (MM), diaxial (GG), equatorial-axial (MG), and axial-equatorial (GM).

Methods for the production of calcium alginate particles have also long belonged to prior art. The so-called drip feed method is often used in production. In this method, a solution of sodium alginate is added dropwise via a hollow needle or cannula to a solution of a crosslinking agent, e.g. a calcium salt solution (an “ionogenic crosslinker”). In order to prevent agglomeration, rotating or vibrating needles or cannulas can be used. Other divalent cations such as Sr2+, Ba2+, Pb2+, Cu2+, Cd2+, Co2+, Ni2+, Zn2+, and Mn2+are also suitable as ionogenic crosslinkers. However, their use is limited by their toxicity. The purely ionogenic crosslinking and the gelation of the alginate solution connected therewith chiefly result from replacement of the Na+ ions of the guluronate in the polymer by e.g. Ca2+. The resulting special spatial arrangement of the guluronic acid sequences around the divalent Ca2+ion is known in the literature as the “egg box model” and is responsible for the structure of the resulting gel network. This imparts strength to the forming particles (beads). Spherical particles of alginate produced by dropwise addition of an alginate solution to a reservoir of an ionogenic crosslinker are widely known in the literature for encapsulation of a wide range of substances, e.g. yeast cells (T. Shiotani et. al., Eur. J. Appl. Microbial. Biotechnol. 13 (2), 1981), bacteria (H. Provost et. al., Biotechnology Letters, 7(4), 247-252, 1985), as well as therapeutic agents (U.S. Pat. No. 485,471). For incorporation purposes, the material to be encapsulated is added to the alginate solution prior to contact with the crosslinking medium.

DE 10026453 A1 discloses magnetic and non-magnetic spherical particles composed of a dimensionally stable alginate gel that is crosslinked by salt bridges between the carboxyl groups of the alginate. The spherical particles can contain incorporated magnetic material, alginate with a D-mannuronate (M): L-guluronate (G) ratio of 0.1:1 to less than 1:1, one or a plurality of cationic species, preferably a divalent or multivalent metal cation, and one or a plurality of agents with favorable properties.

The subject matter of EP 1110462 A2 (Nutrinova) is an encapsulated biologically active food ingredient composed of a core containing at least one dietary fiber which is surrounded by a biologically active substance and a capsule-forming substance surrounding the core, wherein the dietary fibers may be wheat fibers or pectin, the biologically active substance may be a nutrient, and the capsule-forming substance may be an emulsifier.

EP 1295538 A2 (Nutrinova) discloses dietary fiber capsules, the core of which contains locust bean fiber and is enclosed on all sides by capsule materials, with the capsule materials being selected from soluble dietary fibers, which may be alginate, pectin, gum arabic, or modified fibers.

EP 1508591 A1 (Symrise) discloses gelatin-free seamless capsules with a liquid core and a solid shell surrounding this core, with the shell being composed of agar, hydrolyzed starch, water, and one or more additives.

EP 2099889 B1 also discloses alginate capsules (beads), but for use in detergents, comprising.

EP 2340805 A2 (Blume) discloses nanocapsules containing at least the following components: a liquid lipid core and a continuous shell surrounding the core composed of at least one hydrophobically modified polysaccharide and at least one membrane-forming emulsifier.

EP 0766515 B1 concerns alginate capsules containing active ingredients which are released on a delayed basis. The alginate capsules have a composition in which the weight ratio of alginate to polyacrylic acid is 75:2 to 75:10 and the polyacrylic acid has a molecular weight of 10 to 250 kDa.

A problem with the particles of prior art, particularly when a high content of flavoring agents or fragrances is to be achieved, is that the capsules are microbially unstable in a wet state. Improved stability can be achieved by drying the capsules. In the drying process, however, the active ingredients encapsulated in the capsules, particularly when these are flavoring agents or fragrances, are frequently pressed out and unintentionally released, causing the particles to shrink and a portion of the encapsulated active ingredients (flavoring agents or fragrances) to be lost before actual use.

The object of the present invention was therefore to provide stable capsules containing active ingredients or substances which allow targeted release of the encapsulated active ingredients or substances, for example during heating, baking, or frying or on exposure to strong shearing forces such as chewing or rubbing. The object of the present invention was thus to develop capsules that are not water-based and are water-insoluble, as most foods and cosmetic products contain water, with the result that the required release on heating, consumption, or exposure to shearing forces is not achieved to an optimal extent or is achieved only in a very limited manner.

Another object of the present invention was to develop capsules that allow a variable content as well as a high content of active ingredients, so that the capsules can be used over the widest possible range of applications, such as in the cosmetic and pharmaceutical fields, particularly in the areas of oral care or dermatology. The active ingredients and substances in the capsules are to be water-insoluble in this case as well, and are only to be released by rubbing or shearing, e.g. on brushing the teeth or rubbing on the skin.

