Title:  Non-gelatin substitutes for oral delivery capsules, their composition and process of manufacture

United States Patent:  6,214,376

Assignee:  Banner Pharmacaps, Inc. (High Point, NC)

Filed:  August 25, 1998

Gelatin-free capsule for use in oral administration of medicines, cosmetic or bath applications, or dietary supplements can be prepared from compositions comprising a) 8-50% by weight of water-dispersible or water-soluble plasticizer, b) 0.5 to 12% by weight .kappa.-carrageenan, c) 0 to 60% dextrins, and d) 1% to 95% by weight water, with the .kappa.-carrageenan comprising at least 50% by weight of all gums forming or contributing to formation of thermoreversible gels in the composition. A capsule for oral administration or cosmetic application may comprise a fill material to be administered to a patient or subject and a capsule, the capsule comprising an aqueous based film comprising a) water-dispersible or water-soluble plasticizer, and b) carrageenan, with the carrageenan comprising at least 50% or 75% by weight of .kappa.-carrageenan, and the carrageenan comprising at least 50% or 75% by weight of all gums which form or contribute to the formation of thermoreversible gels. A process for forming the capsules may comprise heating the composition, casting or extruding the composition into a film, gelling the composition by cooling, associating a fill material with the gelled composition (usually as a film) and sealing the film about the fill material.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to the manufacture of gelatin-free soft capsules employing .kappa.-carrageenan as the main gel-forming polymer (at least 50% by weight of gel-forming material, including all gums except for those from starch derivatives such as maltodextrin, gum arabic and proteins). For example, mixtures of 50/50 .kappa.-carrageenan/iota-carrageenan, 50/25/25 .kappa.-carrageenan/xanthan gum and locust bean gum, will work. Existing processing equipment for soft gelatin capsules can be used for the non-gelatin polymer composition because of the unique combination of physical properties which these compositions display, even in comparison with other natural hydrocolloids which are related to .kappa.-carrageenan. .kappa.-Carrageenan when dissolved in water by heating, followed by cooling, can form thermoreversible gels, optionally in the presence of additionally added cations. A film-forming gel mass is prepared by combining .kappa.-carrageenan, water (preferably deionized water), an optional gelling salt(s), and plasticizer. Gelling salts can be salts of divalent cations such as calcium, magnesium, and barium or salts of monovalent cations such as potassium and sodium. Preferably, where a gelling salt is additionally used (in addition to the salts which may be naturally present in the commercial .kappa.-carrageenan), a salt comprising a potassium salt, and in particular, a highly soluble potassium halide such as potassium chloride, is used. Carbohydrates, especially liquid carbohydrates, whether natural or synthetic, such as glycerin, alkylene glycols (e.g., polyethylene glycol, propylene glycol, and their mixtures or functionalized derivatives, the number present after the Tradename usually relating approximately to the molecular weight or the number of repeating units of the glycol), sorbitol (and sorbitol solution), maltitol, lactitol, xylitol, corn syrup solids, and other polyols or combinations of the above can be used as plasticizers. Preferably, a mixture of maltitol syrup and sorbitol solution is used.

It is desirable to be able to distinguish amongst the various types of gums preferred and tolerated in the practice of the present invention. Gums (hydrocolloids) that form thermoreversible gels or contribute to the formation of thermoreversible gels include, for example, .kappa.-carrageenan, iota-carrageenan, xanthan gum, gellan gum, and mannan gums (such as locust bean gum, konjac gum, tara gum and cassia gum). The specific words used in the description of "or contribute to the formation of thermoreversible gels" are important because some of these gums, such as the mannan gums and xanthan gum, do not form thermoreversible gels by themselves, but they form thermoreversible gels with carrageenan through a synergistic effect. Gums (hydrocolloids) that do not form thermoreversible gels include dextrins (including maltodextrin), proteins, gum arabic and polyvinylpyrrolidone (e.g., Povidone.TM.). The latter gums may simply be film formers (such as gum arabic and Povidone.TM.) or both film formers and formers of non-thermoreversible (heat stable) gels (such as various plant proteins, for example, soy protein). The term `thermoreversible gum` therefore refers to a gum the gel of which is thermoreversible or contributes to the formation of thermoreversible gels with .kappa.-carrageenan.

Optionally, mannan gums (e.g., locust bean gum, konjac gum, and tara gum) which have a synergistic gelling effect with .kappa.-carrageenan can be added to increase gel strength and elasticity. Also, part of .kappa.-carrageenan may be substituted by iota-carrageenan (up to a maximum of 50% or 25% by weight of the .kappa.-carrageenan) which forms "softer" and more elastic gels. Mechanical properties of carrageenan films can also be improved through a synergistic effect with added mixtures of xanthan gum (a microbial gum) and locust bean gum.

Optionally, hydrolyzed starches, such as maltodextrin (a hydrolyzed starch and an inexpensive biopolymer), are added to 1) increase solids concentration in the gel mass, 2) aid heat sealing by increasing wet film tackiness, and 3) prevent "hazing" of dried carrageenan capsules induced by the gelling salt and, if added, the mannan gums. Maltodextrin from corn starch is optionally used due to wide availability and low cost. However, dextrins from other starchy feedstocks (e.g., wheat, rice, barley, tapioca, potato, and cassava) can be used as well.

Optionally, a native or modified water-soluble or water-dispersible protein (or mixtures of proteins) derived from plant sources including, but not limited to, cereals (e.g., wheat, corn, sorghum, rice, and oat), oilseeds.(soybeans, peanuts, and cottonseed), tubers (e.g., potato), and legumes (e.g., pea and lentil) is incorporated in the gel mass to increase wet tackiness, thus improving heat-sealing properties of cast ribbons. Of course, animal proteins (e.g., whey protein, keratin, casein, egg albumen, and fish myofibrillar protein) may be used for this purpose as well. The use of animal proteins, however, would defeat one of the purposes of the use of non-animal materials in the capsule.

Preferably, the gel mass ingredients are combined in the following manner. Maltodextrin, gum arabic, and protein (if present) are dissolved. The blend of gum (carrageenan and optionally a mannan gum or a mixture of xanthan gum and locust bean gum) and the gelling salt (if present) is dispersed in the plasticizer (at about or above room temperature, with each of these non-reactive, premixing steps, being performable in any order). Then, the maltodextrin or gum arabic or protein solution is added to the gum/salt/plasticizer mixture and the gel mass is heated up to 135-210^oF. under stirring. The maltodextrin may be present, for example, at above 0% such as about 10 to 500% by weight of said carrageenan (especially as a percentage of the .kappa.-carrageenan), more preferably as about 100 to 200% by weight of said .kappa.-carrageenan. Similar to gelatin, ribbons (sheets) can be cast from the heated gel mass for subsequent encapsulation of liquid or solid fills.

The formulations of the present invention for the preparation of essentially gelatin-free compositions may comprise, for example, 8-50% by weight of plasticizer, 0.5 to 12% by weight .kappa.-carrageenan, and the remainder comprising water (e.g., approximately 38% to 91.5% or 95% by weight water), exclusive of consideration of other optional or preferable additives. Where the additives are the dextrins (especially maltodextrin), gum arabic and proteins, those materials may be present at levels of from 0% to about 25% or more of the composition, for between 0 and 20%, between 0.1 and 20%, between 1 and 15%, between 2 and 15% and the like. The .kappa.-carrageenan therefore may be present as 75% or 50% by weight of all gums which form or contribute to the formation of thermoreversible gels, into which class the dextrins, gum arabic and proteins do not fit. Additional materials may be present such as colorants (e.g., dyes and pigments), flavorings, aroma agents, diluents (e.g., particulates such as calcium carbonate), minerals to enhance the benefits of the oral consumption of the capsule, antioxidants (e.g., ascorbic acid), Ultraviolet radiation absorbers to protect encapsulants, opacifying agents (e.g., titanium dioxide), dextrins (such as maltodextrin), proteins and the like. The presence of these additional ingredients may or may not be considered in the determination of the fundamental weight percentages of the plasticizer, .kappa.-carrageenan and water. The ratio of .kappa.-carrageenan to plasticizer may range from about 1:40 to 1:1 on a weight basis. The additional gums may comprise a minor percentage of the .kappa.-carrageenan, as for example up to 25% or 50% by weight of the .kappa.-carrageenan. The dextrins, as gums that do not form or contribute to the formation of thermoreversible gels, are treated differently in the tolerable amount, as described above. These additional gums or additives (whether forming thermoreversible gels or not) may be selected from mannan gums, xanthan gums, iota-carrageenan, the native or modified water-soluble or water-dispersible proteins (discussed above), gellan gums, gum arabic, polysaccharides, Povidone.TM. (polyvinylpyrrolidone), natural and synthetic resins and the like. It is preferred for simplicity of the composition that these additional materials be minimized or completely absent from the composition so that there is less than 50% or less than 25% of the total of these ingredients present within the composition, preferably less than 10% by weight of the total composition (comprising plasticizer, .kappa.-carrageenan, and water) of any single ingredient or combination of ingredients, more preferably less than 5%, still more preferably less than 3% or less than 2%, and most preferably less than 1% or less than 0.5% by weight of the total composition (comprising plasticizer, .kappa.-carrageenan, and water) of any single ingredient or combination of ingredients. The most tolerable ingredient is the iota-carrageenan. The next most tolerable ingredients comprise the natural gums such as mannan gums and xanthan gum. Mannan gums and xanthan gum, in particular, can have a beneficial effect on the system in increasing the gel strength of the capsules, reduce syneresis, and improve elasticity. Although the use of gums is tolerated or desirable (gums which do not form thermoreversible gels) or possibly particularly beneficial (thermoreversible gums) in the practice of the present invention, it is preferred that the ratio of plasticizer to the total amount of gum that forms or contributes to the formation of thermoreversible gels (if not with respect to the total of all gums) be maintained above 4:1, preferably above 5:1, and most preferably above 6:1 or above 8:1 or higher (e.g., above 10:1). It is preferred that the use of gellan gum be minimized or eliminated, with less than 0.1% by weight of the composition comprising gellan gum, preferably less than 0.05% gellan gum, and most preferably below 0.02% down to 0% of gellan gum.

A preferred method of preparation of the compositions of the present invention comprises dispersing the .kappa.-carrageenan in the plasticizer at about room temperature or higher, adding water, heating and gelling the composition by cooling. Gelling is observed by determining particular changes in physical properties of the composition. When the composition is prepared at room temperature, it is a very viscous mass (often dough-like). Upon heating, the mass "thins out" and is converted to a clear, free-flowing liquid. The liquid may not necessarily be clear when certain optional film-forming materials are present. Materials such as proteins may impart a milky appearance or even some coloration, and, of course, if pigments or opacifying agents are added (e.g., titanium oxide), the solution would not be clear. Upon cooling (for example by casting on the surface of revolving cooled drums) the mass gels or sets, forming a freestanding ribbon (film). The composition has been found to be self-gelling, even without the addition of gelling salts (possibly because of the presence of cations in the commercial .kappa.-carrageenan product). Gelling salts may be added, however, to accelerate the gelling, or to increase gel strength, or to control the gelling more precisely. Gelling salts (e.g., especially the potassium salts) may be present as 0% of the composition, or up to about 3% or more by weight of the composition. The amount of the salt may vary significantly because of the variation in the weight of the counterion, but is preferably within a range of 0.01 to 1% by weight of the total composition, more preferably as 0.01 to 0.5% by weight of the total composition, usually as a halide salt. Potassium citrate is also a known potassium gelling salt. The addition of the gelling salts, the percentage of additives (e.g., plasticizers, gums, iota-carrageenan, etc.) can be used to control or vary the melting point or thermal fusion point of the gel. One of the important aspects of the present invention in the use of the non-gelatin compositions is the fact that the melting or fusion temperatures of the compositions can be easily controlled. Where the encapsulant might be particularly sensitive to thermal stress or decomposition temperatures, the ability to control and especially lower the capsule processing temperatures is a useful capability.

Claim 1 of 53 Claims

What is claimed:

1. A composition comprising:

a) 8 to 50% by weight of a plasticizer;

b) 0.5 to 12% by weight of .kappa.-carrageenan; and

c) 1 to 95% by weight water,

wherein the .kappa.-carrageenan comprises at least 50% by weight of all film-forming material in the composition and the weight ratio of plasticizer to .kappa.-carrageenan is greater than 1.

____________________________________________
If you want to learn more about this patent, please go directly to the U.S. Patent and Trademark Office Web site to access the full patent.