| PATENT NUMBER | This data is not available for free |
| PATENT GRANT DATE | October 16, 2001 |
| PATENT TITLE |
Method for the preparation of oxide microcapsules loaded with functional molecules and the products obtained thereof |
| PATENT ABSTRACT | The present invention relates to a novel process for preparing sol-gel microcapsules loaded with up to 95% (w/w) functional molecules or substances and to the products obtained by said process. Said process is conducted in two steps: (a) creating an oil-in-water emulsion by emulsification of a water insoluble solution comprising the sol-gel precursors and the molecules to be loaded, in an aqueous solution under appropriate shear forces; (b) mixing and stirring said emulsion with an aqueous solution at a suitably selected pH to obtain loaded sol-gel microcapsules in suspension. The microcapsules so obtained can further be subjected to cycles of isolation and rinsing. Incorporation of the final product, either in the form of a suspension or a powder, in cosmetic formulations affords a transparent cream when applying to skin and has a smooth and pleasant contact. |
| PATENT INVENTORS | This data is not available for free |
| PATENT ASSIGNEE | This data is not available for free |
| PATENT FILE DATE | August 11, 1999 |
| PATENT PARENT CASE TEXT | This data is not available for free |
| PATENT CLAIMS |
What is claimed is: 1. A process for preparing sol-gel microcapsules loaded with up to 95% (w/w) functional molecules, comprising the steps of: a) emulsifying a nonaqueous, water insoluble solution, comprising sol-gel precursors and the functional molecules to be loaded, in an aqueous solution, under shear forces and with surfactants; b) mixing and stirring the emulsion obtained in step (a) with an acidic, neutral or basic aqueous solution to obtain loaded sol-gel microcapsules in a suspension. 2. A process according to claim 1 wherein the pH of the aqueous solution of step (b) is in the range of 8-13. 3. A process according to claim 1 wherein the mixture of step (b) is heated or cooled, subject to vacuum or pressure, or kept under inert gas atmosphere, subject to changes in pH and with an optional aging period of up to 14 days. 4. A process according to claim 1 wherein the hydrophobic solution in step (a) and the aqueous solution in step (b) contain additional surfactants or any additives to improve the product. 5. A process according to claim 1, comprising the further step of isolating and rinsing the microcapsules through cycles of separation by centrifuge or by filtration and re-suspension in water, or by evaporation and re-suspension in water or by dialysis. 6. A process according to claim 5 wherein the suspension so obtained is stabilized by adding additives selected from the group consisting of non-ionic, cationic and anionic polymers. 7. A process according to claim 5 further comprising the step of removing the water to obtain the final product in a powder form. 8. A process according to claim 7 further comprising adding reconstitution additives selected from the group consisting of non-ionic, cationic and anionic surfactants or polymers. 9. A process according to claim 1 wherein the sol-gel precursors are metal or semi-metal alkoxide monomers, or metal ester monomers, or semi-metal ester monomers or monomers of the formula M(R).sub.n (P).sub.m, wherein M is a metallic or semi metallic element, R is a hydrolyzable substituent, n is an integer from 2 to 6, P is a non polymerizable substituent and m is an integer from 0 to 6, or partially hydrolyzed and partially condensed polymer thereof, or any mixture thereof. 10. A process according to claim 1 wherein the sol-gel precursors are silicon alkoxide monomers, or silicon ester monomers, or monomers of the formula Si(R).sub.n (P).sub.m, where R is a hydrolyzable substituent, n is an integer from 2 to 4, P is a non polymerizable substituent and m is an integer from 0 to 4, or partially hydrolyzed and partially condensed polymer thereof, or any mixture thereof. 11. A process according to claim 1 wherein the sol-gel precursors are titanium alkoxide monomers, or titanium ester monomers, or monomers of the formula Ti(R).sub.n (P).sub.m, where R is a hydrolyzable substituent, n is an integer from 2 to 6, P is a non polymerizable substituent and m is an integer from 0 to 6, or partially hydrolyzed and partially condensed polymer thereof, or any mixture thereof. 12. A process according to claim 1 wherein the sol-gel precursors are zinc or zirconium alkoxide monomers, or zinc or zirconium ester monomers, or monomers of the formula Zn(R).sub.n (P).sub.m or Zr(R).sub.n (P).sub.m, where R is a hydrolyzable substituent, n is an integer from 2 to 6, P is a non polymerizable substituent and m is an integer from 0 to 6, or partially hydrolyzed and partially condensed polymer thereof, or any mixture thereof. 13. A process according to claim 1 wherein several sol-gel precursor are used together in a mixture, including a mixture of several metals or semi metal compounds, to afford a sol-gel material which is a composite containing different metal and/or semi metal elements in the final product. 14. A process according to claim 1 wherein the surface charge of the products is modified by adding anionic or cationic surfactants or polymers during any step of the process. 15. A process according to claim 1 wherein the functional molecules are ultra-violet absorbing molecules or ultra-violet reflecting substances to be used in sunscreens. 16. A process for preparing sol-gel microcapsules loaded with up to 95% (w/w) functional molecules, comprising the steps of: a) emulsifying a nonaqueous, water insoluble solution, comprising sol-gel precursors and the functional molecules to be loaded, in an aqueous solution, under shear forces and with surfactants; b) mixing and stirring the emulsion obtained in step (a) with an acidic, neutral or basic aqueous solution to obtain loaded sol-gel microcapsules in a suspension, wherein the functional molecules are ultra-violet absorbing molecules or ultra-violet reflecting substances to be used in sunscreens, wherein the ultra-violet absorbing molecules are selected from the group consisting of 2-ethylhexyl p-methoxycinnamate, p-aminobenzoic acid, 2-ethylhexyl N,N-dimethyl-p-aminobenzoate, 2-cyano-3,3-diphenylacrylic acid 2-ethylhexyl ester (octocrylene), oxybenzone, 2-phenylbenzimidizole-5-sulfonic acid, homomenthyl salicylate, octyl salycilate, 4,4'-methoxy-t-butyldibenzoylmethane, 4-isopropyl dibenzoylmethane, 3-(4-methylbenzyledene) camphor, 3-benzylidene camphor, triethanolamine salicylate, 4-N,N-(2-ethylhexyl)methyl aminobenzoic acid ester of 2,4-dihydroxybenzophenone, 4-N,N-(2-ethylhexyl)methyl aminobenzoic acid ester of 4-hydroxydibenzoylmethane, 4-N,N-(2-ethylhexyl)methyl-aminobenzoic acid ester of 2-hydroxy-4-(2-hydroxyethoxy)-benzophenone, 4-N,N-(2-ethylhexyl)methyl aminobenzoic acid ester of 4-(2-hydroxyethoxy)dibenzoylmethane and a mixture thereof. 17. A process according to claim 1 wherein the functional molecules or substances are selected from the group consisting of fragrances, perfume, colors and dyes, food colors and food additives, antioxidants, humidifiers, vitamins, explosives, insecticides, herbicides and fungicides, or biological molecules selected from the group consisting of enzymes and antibodies, and drugs, catalysts and reagents. 18. A process according to claim 1 wherein the functional molecules are selected from the group consisting of natural food colors, synthetic food colors, and food additives used in food products or oral drugs. 19. A process according to claim 1 wherein the functional molecules are natural food colours or synthetic food colours used in cosmetic colours and skin applications. 20. A process according to claim 1 wherein the functional molecules are selected from the group consisting of insecticides, herbicides and fungicides used in agriculture or industry. 21. The products obtained by the process according to claim 1. 22. The products obtained by the process according to claim 1 in a suspension form. 23. The products obtained by the process according to claim 1 in a powder form. 24. Products according to claim 21 wherein the powder particles or the suspended particles are of 0.01-100.mu.. 25. Products according to claim 21 wherein the powder or the suspension consists of 0.1-10.mu. spherical particles, has smooth texture, and is transparent when suspended in cosmetic or skin care formulations and applied to skin. 26. Products according to claim 21 wherein the leaching of the loaded molecules into cosmetic oils or into a surfactant-containing aqueous solution is less than 5% after vigorous shaking. 27. Products according to claim 26 wherein the leaching of the loaded molecules into cosmetic oils or into a surfactant-containing aqueous solution is less than 2% after vigorous shaking |
| PATENT DESCRIPTION |
FIELD OF THE INVENTION The present invention generally relates to a method for isolating functional molecules or substances in inert matrices. More specifically the present invention relates to a method for the preparation of 0.01-100.mu. sol-gel microcapsules loaded with up to 95% functional molecules or substances which can be dissolved in sol-gel precursors wherein the sol-gel precursors can be a metal or a semi-metal alkoxide monomer, or a partially hydrolyzed and partially condensed polymer thereof, or a mixture of any of the above. The present invention also relates to the products obtained by this process. The particle size of the final product can be controlled to the range 0.01-100.mu., more preferably 0.1-10.mu.. Under appropriate choice of the reaction conditions said product is in the form of an aqueous suspension of up to 60% solids, consisting of sphere particles of 0.1-10.mu. or in the form of fine powder with a smooth and pleasant texture consisting of sphere particles of 0.1-10.mu.. BACKGROUND OF THE INVENTION The present invention generally relates to a method for preparing sol-gel particles that encase or encapsulate or entrap (hereinafter called loading) functional molecules or substances. The term "functional molecules or substances" in the present invention relates to any molecules or substances that can be used in agriculture and industry. Isolating functional molecules or substances in inert matrices has many useful benefits and applications where chemical contact between the functional molecules and the immediate environment should be minimized. For example, make-up compositions, such as make-up colors are currently using a very limited number of approved natural pigments and even fewer artificial organic colors. Many dyes and pigments with desired color shades of natural or synthetic origin are not approved for skin contact because their safety for direct skin contact has not been demonstrated. Isolating the colorants in transparent and inert isolating material provides a way to prevent the direct contact between the color molecules and the skin, while retaining (or even enhancing) the color intensity. Another very important application is in sunscreen compositions. The active ingredients in sunscreens have been reported to cause contact dermatitis and may cause photocontact dermatitis. Moreover, the light-excited species of these reagents may undergo photodecomposition reactions resulting in the production of free radicals and reactive oxygen species, which may bear deleterious effects on live tissues. Thus, encapsulating sunscreen active ingredients in a transparent matrix like silica offers a sophisticated way to benefit from the light-absorbing capability of sunscreens, while substantially isolating them and/or their possible photodecomposition products from the live tissues. Another example, from a totally different field, is the encapsulating of food colors either for prolonging the shelf life of food products containing unstable natural colors such as lycopene and carotene or for isolating artificial food colors that have undesirable side effects. Encapsulating food colors of the second type in inert transparent microcapsules provides a way to prevent the digestion of these colorants while maintaining their desired color effect. Recognizing that metal and semi metal alkoxide monomers (and their partially hydrolyzed and condensed polymers) such as tetramethoxy silane (TMOS), tetraethoxy silane (TEOS), methyl triethoxy silane (MeTEOS) etc. are very good solvents for numerous molecules and substances facilitated the development of this method, which utilizes this solubility to load the dissolved molecules or substances in the hydrolysis-condensation polymer of the monomer solvent. Nonetheless, the present invention may also be used to coat or load particles or substances which can be suspended in the sol-gel precursors. The current invention reveals how to obtain sol-gel materials containing high loading of active ingredients, up to 95% (w/w). Such high loading is required, for example, in order to obtain high Sun Protection Factor (SPF) values. It also facilitates the entrapment or encapsulation of many other molecules or substances, where the application may demand high loading of the entrapped molecule or substance. The loaded molecules or substances can be any molecules or substances that are soluble or that can be suspended in the metal or semi-metal alkoxides of choice. Examples for such molecules or substances are: ultra-violet absorbing molecules or reflecting substances used in sunscreens, fragrances, perfume, colors and dyes, food colors and food additives, antioxidants, humidifiers, vitamins, explosives, insecticides, herbicides and fungicides, or biological molecules such as enzymes or antibodies, as well as various drugs, catalysts and reagents. The current invention further teaches how to obtain controlled physical form of the product. In a preferred embodiment, it teaches how to obtain capsules and microcapsules of sol-gel derived material, containing the loaded molecule or substance, with a smooth and pleasant contact. The product by process may accordingly vary for human or non-human applications, as the obtained aqueous suspension and the obtained dry powder may be easily incorporated in various carriers, such as creams and lotions, processed food, sprays, paints, lacquers, coatings, plastics and detergents. SUMMARY OF THE INVENTION The present invention relates to a novel process for preparing sol-gel particles loaded with up to 95% (w/w) functional molecules and to the products obtained by said process. Said process is conducted in two steps: (a) creating an oil-in-water emulsion by emulsification of a water insoluble solution comprising the sol-gel precursors and the molecules to be loaded, in an aqueous solution under appropriate shear forces; (b) mixing and stirring the said emulsion with an aqueous solution at a suitably selected pH to obtain loaded sol-gel particles of 0.01-100.mu.. (In the present invention the term "mixing" also relates to dropwise addition of one solution to the other, by pouring one solution to the other, or any other method of combining the two solutions together). After an appropriate reaction time, during which the mixture may be heated or cooled, subject to vacuum, changes in pH and optionally an aging period, the resulting particles may be isolated and rinsed through cycles of centrifuge or filtration and re-suspension in deionized water or by any other means known in the art. The water insoluble solution (of step a) and the aqueous solutions (of steps a and b and in the optional further rinses) may contain various surfactants and any other additives for improving the process and/or the product. By selecting the appropriate reaction conditions, the particle size of the final product can be controlled to be in the range from 0.01 to 100.mu. and the leaching degree of the loaded molecule into cosmetic oils or into the surfactant-containing aqueous solution can be minimized. The sol-gel precursors can be a metal or a semi-metal alkoxide monomers, or a partially hydrolyzed and partially condensed polymer thereof, or a mixture thereof. The functional molecules and substances can be any molecules and substances that can be used in agriculture and industry. In a preferred embodiment of the present invention, under appropriate choice of the reaction conditions, said product is in the form of a suspension containing about 1 to 60% solids consisting of sphere particles of 0.1-10.mu.. Said suspension may be stabilized with the aid of suitable additives such as non-ionic, cationic or anionic polymers, or any other suspension aid known to the skilled artisan in this field This suspension shows extremely low leaching of the encapsulated material into surfactants solution in water, or into cosmetic oils. Incorporation of this aqueous suspension in a cosmetic formulation affords a transparent cream when applying to skin and has a smooth and pleasant contact. In another preferred embodiment of the present invention, under appropriate choice of the reaction conditions said product is in the form of a fine powder with a smooth and pleasant texture consisting of sphere particles of 0.1-10.mu.. Dispersion of this powder in a cosmetic formulation affords a transparent cream when applying to skin and has a smooth and pleasant contact. DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a process for the preparation of sol-gel microcapsules of 0.01-100.mu., loaded with functional molecules or substances. The process is based on the preparation of an oil-in-water emulsion of the hydrophobic solution that comprises the sol-gel precursors and the molecules or substances to be loaded, in aqueous solution and then mixing said emulsion with another aqueous solution to accelerate the condensation-polymerization reaction. The polymerization progresses through condensation-polymerization of at least one monomer selected from metal alkoxides, semi-metal alkoxides, metal esters, semi-metal esters and from monomers of the formula M(R).sub.n (P).sub.m, wherein M is a metallic or semi metallic element, R is a hydrolyzable substituent, n is an integer from 2 to 6, P is a non polymerizable substituent and m is and integer from 0 to 6. In a preferred embodiment of this invention, the sol-gel precursors are silicon alkoxide monomers, or silicon ester monomers, or monomers of the formula Si(R).sub.n (P).sub.m, where R is a hydrolyzable substituent, n is an integer from 2 to 4, P is a non polymerizable substituent and m is and integer from 0 to 4, or partially hydrolyzed and partially condensed polymer thereof, or any mixture thereof. In another preferred embodiment of the present invention, the sol-gel precursors are titanium alkoxide monomers, or titanium ester monomers, or monomers of the formula Ti(R).sub.n (P).sub.m, where R is a hydrolyzable substituent, n is an integer from 2 to 6, P is a non polymerizable substituent and m is and integer from 0 to 6, or partially hydrolyzed and partially condensed polymer thereof, or any mixture thereof. In another preferred embodiment of the present invention, the sol-gel precursors are zinc or zirconium alkoxide monomers, or zinc or zirconium ester monomers, or monomers of the formula Zn(R).sub.n (P).sub.m or Zr(R).sub.n (P).sub.m, where R is a hydrolyzable substituent, n is an integer from 2 to 6, P is a non polymerizable substituent and m is and integer from 0 to 6, or partially hydrolyzed and partially condensed polymer thereof, or any mixture thereof. In yet another preferred embodiment of this invention, several sol-gel precursor are used together in a mixture, including mixtures of several metals or semi metal compounds, to afford a sol-gel material which is a composite containing different metal and/or semi metal elements in the final product. The loaded molecules or substances may be any molecules or substances that are soluble or that can be suspended in the metal or in the semi metal alkoxides of choice. Examples for molecules or substances that can be loaded include sunscreens, fragrances, perfume, colors and dyes, food colors and food additives, antioxidants, humidifiers, vitamins, explosives, insecticides, herbicides and fungicides, or biological molecules such as enzymes or antibodies, as well as various drugs, catalysts and reagents. The product by process may accordingly vary for human or non-human applications, as the obtained powder may be easily incorporated in various carriers, e.g. creams and lotions, processed food, sprays, paints, lacquers, coatings, plastics, detergents etc. Said process is conducted by the following steps: (a) A solution consisting of the water insoluble metal alkoxides with or without a co-solvent and/or surfactant and the molecules to be entrapped is emulsified in an aqueous solution, that may contain various surfactants, i.e. cationic, anionic or non-ionic surfactants, which are utilized to assist in stabilizing the emulsions. This emulsion is created under appropriate shear forces, utilizing an apparatus such as a homogenizer, a high pressure homogenizer or a sonicator. The oil phase of the emulsion may optionally contain additives for improving the process and/or for obtaining an improved product. Examples for such additives are viscosity modifying reagents (i.e., thickeners), acids or bases that dissolve in the sol-gel precursor of choice and assist in catalyzing the hydrolysis-condensation polymerization reaction, surfactants and others. (b) The emulsion obtained by step (a) is mixed with an aqueous solution at a suitably selected pH (basic, neutral or acidic), which may also contain additional surfactants. The aqueous solution may also contain additives for improving the process and/or for obtaining an improved product such as glass water. The reaction mixture may be heated or cooled, subject to vacuum, or pressure, or kept under inert gas atmosphere, subject to changes in pH and with an optional further aging period. The resulting particles can be isolated and rinsed through cycles of centrifuge or filtration and re-suspension in deionized water or by dialysis or by any other technique known in the art. The final product may be used in a dispersion form, after re-suspension in water with optional addition of suitable additives such as non-ionic, cationic or anionic polymers, or any other suspension aid known to the skilled artisan in this field. This dispersion shows extremely low leaching of the encapsulated material into surfactants solution in water, or into cosmetic oils. The final product may also be used in a powder form, after removal of the water by appropriate means (drying, lyophilization, etc.) with optional addition of reconstitution additives such as non-ionic, cationic or anionic surfactants or polymers. The loading of the loaded molecules or substances in the oxide carrier may be from zero up to 95% weight of the solid. The loading of the loaded molecules or substances in the final aqueous dispersion may be up to 50% wt/wt of the aqueous suspension. The particle size of the final product can be controlled to the range 0.01-100.mu., more preferably 0.1-10.mu.. The particles obtained by the present process can sustain high shear forces such as those present in a homogeizer or a sonicator without change in their encapsulation properties or in particle size distribution. The particles can also sustain increased temperatures up to 80.degree. C. for 2 hours, without any such change. The product by process may be designed to hold and/or isolate the entrapped molecules within the sol-gel matrix, or to act as a matrix for controlled or sustained release of the loaded molecules. |
| PATENT EXAMPLES | available on request |
| PATENT PHOTOCOPY | available on request |
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