Drug – bio-affecting and body treating compositions – Topical sun or radiation screening – or tanning preparations
Patent
1999-07-15
2000-12-12
Dodson, Shelley A.
Drug, bio-affecting and body treating compositions
Topical sun or radiation screening, or tanning preparations
424 60, 424401, 424451, 424455, 424489, 424490, 501 12, 501 32, 501 53, A61K 742, A61K 744, A61K 700, A61K 948, A61K 966
Patent
active
061594539
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention generally relates to sunscreen-doped sol-gel materials useful for protecting body tissues and other surfaces from ultra violet radiation (the term "ultra violet radiation" in the present invention, unless otherwise specified, includes radiation in the range of 320-400 nm, called UVA, and radiation in the range of 280-320 nm, called UVB. Ultra violet radiation is hereinafter called UV radiation), to a method for preparing said sunscreen-doped sol-gel materials and to a method for protecting body tissues and other surfaces from UV radiation, using the said sunscreens. More specifically, the present invention relates to sol-gel matrices produced by hydrolysis and condensation-polymerization of metal and semi-metal alkoxide monomers to which sunscreen molecules are added either prior to or after hydrolysis of the monomer, followed, if needed, by a pH change and by gelation. The resulting sunscreen-doped sol-gel materials can be obtained in almost any shape and may be applied, as dispersions or powders, to body tissues and other surfaces, thereby achieving protection of the body tissues and surfaces against damaging effects of the sun radiation, without having undesirable direct contact between the sunscreening chemical ingredients and the body tissues.
BACKGROUND OF THE INVENTION
Sunscreens are chemical ingredients which are usually applied topically to the skin and hair in order to protect them from the damaging effects of the sun's radiation, especially against (UV) ultraviolet radiation.
There is evidence that prolonged sunlight exposure results in increasing incidence of skin carcinogenesis, pigmentation, anomalies and precancerous lesions such as actinic keratosis, melanoma and nonmelanoma skin cancers, as well as accelerated skin aging and undesirable changes in hair quality.
Sunscreens are usually classified in two major categories. The first includes chemical sunscreens which absorb sun radiation and therefore reduce the amount of UV radiation reaching the skin. Chemical sunscreens can be subdivided into eight derivative families: para amino benzoates, salicylates, cinnamates, benzophenones, anthranilates, dibenzoylmethanes, camphores and miscellaneous chemicals. The second category includes physical sunscreens which reflect, scatter or physically block the UV light reaching the skin surface. Physical sunscreens are mainly metal oxides such as titanium dioxide, zinc oxide and also red petrolatum.
Ultimate sunscreens should be chemically inert, highly photostable and neither sensitizing nor photosensitizing. Yet, according to more than 200 published reports relating to all major chemical sunscreen families, sunscreen agents induce both contact and photocontact dermatitis (Dromgoole and Maibach, In Sunscreens, eds. N. J. Lowe, N. A. Saath; Marcel Dekker: N.Y., 1990, Chapter 20). In other publications it was reported that commonly used sunscreen compounds undergo photodecomposition reactions (Roscher et al. J. Photochem. Photobiol. A: Chem, 80: 417-421, 1994). Moreover, although more people are using sunscreens, the rate of skin cancer around the world is rising. A possible explanation is that sunscreens might encourage, rather than prevent, sun related cancers. Indeed, it was found (Knowland et al. FEBS Letters, 324: 309-313, 1993) that the commercial sunscreen ingredient Padimate-O is mutagenic in sunlight. The sunlight-excited Padimate-O is thought to produce free radicals which directly attack the DNA.
Physical sunscreens, especially titania, such as disclosed in Chemical Abstracts 124:153660 although considered to be "relatively safe", are known to be photosensitizers capable of rupturing covalent bonds (U. Stafford, K. A. Gray and P. V. Kamat, Heterogeneous Chem Rev, 3, 77-104, 1996).
There is, therefore, a great need for isolating chemical and physical sunscreen agents from the body while retaining both the sunscreen activity and the compatibility with cosmetic preparations.
U.S. Pat. No. 5,223,250 and WO Patent 95/28912 describe the entrapments of s
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(1) Patent Abstract of JP 08 099838, Aug. 30, 1996.
(2) Chemical Abstract of JP 07 315 859, May 12, 1995.
(3) Chemical Abstract of JP 05 178 995, Jul. 20, 1993.
Avnir David
Cohen Levy David
Dodson Shelley A.
Lamm Marina
Yissum Research Development Company of the Hebrew University of
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