Compositions Comprising Solid Particles Entrapped In Collapsed Polymeric Microspheres, And Methods Of Making The Same

Abstract

The present invention relates to topical compositions containing solid particles that are stabilized via entrapment by microspheres. Each of the microspheres contains a collapsed polymeric shell that has entrapped therein one or more solid particles. The solid particles are preferably formed of zinc oxide or titanium dioxide or both, which can readily be used either alone or in combination with other sunscreen agents to form sunscreen compositions of broader UV protection spectrum and enhanced photostability.

1 . A topical composition comprising a dispersion of microspheres in a cosmetically or pharmaceutically acceptable carrier, wherein each of said microspheres comprises a collapsed polymeric shell having entrapped therein one or more solid particles. 
   
   
       2 . The composition of  claim 1 , wherein the microspheres have an average particle size ranging from about 1 micron to about 50 microns, and the solid particles have an average particle size ranging from about 0.001 micron to about 0.5 micron. 
   
   
       3 . The composition of  claim 1 , wherein the collapsed polymeric shell comprises at least one synthetic polymer obtained by polymerization of one or more ethylenically unsaturated monomers selected from the group consisting of vinylidene chloride, vinyl chloride, acrylonitrile, acrylic acid and its C 1 -C 20  aliphatic or aromatic esters, methacrylic acid and its C 1 -C 20  aliphatic or aromatic esters, acrylamide, methacrylamide, vinyl pyrrolidone, alkenes, styrene, ethylene, propylene, butylene, methylpentene, and 1,3-butadiene. 
   
   
       4 . The composition of  claim 1 , wherein the collapsed polymeric shell comprises at least one synthetic thermoplastic polymer selected from the group consisting of polyesters, polyamides, polyphthalamides, polyimides, polycarbonates, polyketones, cellulose acetate, polysulfones, polyphenylene sulfides, polyphenylene oxides, polylactic acids, polyvinylpyrrolidone, polystyrene, polyacrylonitrile, polyacrylamide, polymethylmethacrylate, polyacrylates, and copolymers thereof. 
   
   
       5 . The composition of  claim 1 , wherein the collapsed polymeric shell comprises a copolymer of vinylidene chloride, acrylonitrile, and/or methyl methacrylate. 
   
   
       6 . The composition of  claim 1 , wherein the entrapped solid particles comprise one or more materials selected from the group consisting of talc, kaolin, mica, bismuth oxychloride, chromium hydroxide, barium sulfate, polymethylmethacrylates (PMMA), boron nitride, nylon beads, polymeric powders, silica, silica beads, lakes, metal oxides, iron oxide, chromium oxide, zinc oxide, titanium dioxide, and physical and chemical sunscreen agents. 
   
   
       7 . The composition of  claim 1 , wherein the entrapped solid particles comprise one or more materials capable of generating free oxygen radicals. 
   
   
       8 . The composition of  claim 1 , wherein the entrapped solid particles comprise one or more metal oxides. 
   
   
       9 . The composition of  claim 1 , wherein the entrapped solid particles comprises titanium dioxide, zinc oxide, or a combination thereof. 
   
   
       10 . The composition of  claim 1 , wherein the collapsed polymeric shell is further coated with a liquid-impermeable membrane. 
   
   
       11 . The composition of  claim 10 , wherein the liquid-impermeable membrane comprises one or more materials selected from the group consisting of acrylate homo- or co-polymers, methacrylate homo- or co-polymers, vinylpyrrolidone homo- or co-polymers, silicone gums, silicone waxes, silicone oils, silicone resins, esters, hydrocarbons, celluloses, fatty acids, fatty alcohols, and inorganic materials. 
   
   
       12 . The composition of  claim 10 , wherein the liquid-impermeable membrane comprises crosslinked dimethicone or trimethylated silica treated with dimethyl siloxane. 
   
   
       13 . The composition of  claim 7 , further comprising at least one organic compound susceptible to oxidative decomposition or degradation. 
   
   
       14 . The composition of  claim 13 , wherein said organic compound is an organic sunscreen agent susceptible to oxidative decomposition or degradation. 
   
   
       15 . The composition of  claim 13 , wherein said organic compound is an organic dye susceptible to oxidative decomposition or degradation. 
   
   
       16 . A microsphere comprising a collapsed polymeric shell having entrapped therein one or more solid particles, wherein the collapsed polymeric shell is further coated with a liquid-impermeable membrane. 
   
   
       17 . A topical sunscreen composition comprising a dispersion of microspheres in a cosmetically or pharmaceutically acceptable carrier, wherein each of said microspheres comprises a collapsed polymeric shell having entrapped therein one or more solid particles that comprise titanium dioxide, zinc oxide, or a combination thereof. 
   
   
       18 . The topical sunscreen composition of  claim 17 , further comprising at least one organic sunscreen agent. 
   
   
       19 . The topical sunscreen composition of  claim 18 , wherein the at least one organic sunscreen agent is selected from the group consisting of 4,4′-t-butyl methoxydibenzoylmethane, 2-ethylhexyl-2-cyano-3,3-diphenylacrylate, 2-ethylhexylsalicylate, 3,3,5-trimethylcyclohexylsalicylate, 2-ethylhexyl p-methoxycinnamate, 2-hydroxy-4-methoxybenzophenone, 2,2-dihydroxy-4-methoxybenzophenone, 2,4-bis-{4-(2-ethyl-hexyloxy)-2-hydroxyl-phenyl}-6-(4-methoxyphenyl)-1,3,5-triazine, methylene bis-benzotriazolyl tetramethylbutylphenol, terephthalylidene dicamphor sulfonic acid, diethylhexyl 2,6-naphthalate, digalloyltrioleate, ethyl 4-[bis(hydroxypropyl)]aminobenzoate, n-hexyl 2-(4-diethylamino-2-hydroxybenzoyl)benzoate, glycerol p-aminobenzoate, methylanthranilate, p-dimethylaminobenzoic acid or aminobenzoate, 2-ethylhexyl p-dimethylaminobenzoate, 2-phenylbenzimidazole-5-sulfonic acid, 2-(p-dimethylaminophenyl)-5-sulfoniobenzoxazoic acid, and mixtures or combinations thereof. 
   
   
       20 . The topical sunscreen composition of  claim 18 , wherein the at least one organic sunscreen agent is 4,4′-t-butyl methoxydibenzoylmethane. 
   
   
       21 . The topical sunscreen composition of  claim 20 , further comprising a second organic sunscreen agent. 
   
   
       22 . The topical sunscreen composition of  claim 18 , wherein the at least one organic sunscreen agent is encapsulated in protective structures. 
   
   
       23 . The topical sunscreen composition of  claim 22 , wherein the protective structures comprise additional microspheres with collapsed polymeric shells, into which the at least organic sunscreen agent is entrapped. 
   
   
       24 . The topical sunscreen composition of  claim 17 , wherein at least some of the microspheres have titanium dioxide particles entrapped therein. 
   
   
       25 . The topical sunscreen composition of  claim 17 , wherein at least some of the microspheres have zinc oxide particles entrapped therein. 
   
   
       26 . The topical sunscreen composition of  claim 17 , wherein some of the microspheres have titanium dioxide particles entrapped therein, and others have zinc oxide particles entrapped therein. 
   
   
       27 . The topical sunscreen composition of  claim 17 , further comprising one or more antioxidants. 
   
   
       28 . The topical sunscreen composition of  claim 27 , wherein said one or more antioxidants are co-entrapped with the solid particles inside the collapsed polymeric shell of each microsphere, or coated over the microspheres, or solubilized or dispersed in the cosmetically or pharmaceutically acceptable carrier. 
   
   
       29 . A method for modifying or treating solid particles, comprising:
 (a) forming a gelled mixture by mixing either simultaneously or sequentially in any order (1) hollow microspheres each comprising a deformable polymeric shell having entrapped therein an expandable fluid, (2) a polar organic solvent capable of swelling but not dissolving the polymeric shells of the hollow microspheres, and (3) solid particles, wherein micro-channels are formed in the swelled polymer shells to allow entry of the solid particles into the hollow microspheres and exit of the expandable fluid therefrom, thereby forming microspheres that each comprises a collapsed polymeric shell in a gelled state and has one or more of said solid particles entrapped therein;   (b) removing the expandable fluid and the polar organic solvent from the gelled mixture; and   (c) coating the microspheres with a film-forming material to form a liquid-impermeable membrane thereon.   
   
   
       30 . The method of  claim 29 , wherein the polar organic solvent is selected from the group consisting of dimethylformamide, dimethylchloride, trichloroethylene, chloroform, methanol, ethanol, isopropanol, acetone, ethyl acetate, butyl acetate, and methyl ethyl ketone. 
   
   
       31 . The method of  claim 29 , wherein the expandable fluid is selected from the group consisting of gases, air, nitrogen, volatile liquid hydrocarbons, isobutane, and isopentane. 
   
   
       32 . The method of  claim 29 , wherein the expandable fluid is first removed from the gelled mixture by de-gassing at a reduced pressure or under vacuum conditions, followed by a quenching step in which water is added to the gelled mixture to allow separation of the microspheres from one another before removal of the polar organic solvent.