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Healthy skin is a sign of positive self-worth, attractiveness and vitality. Compromises to this are frequently caused by extended periods of recreation in the sun and in turn exposure to the harmful effects of UV radiation. To maintain strength and integrity, protection of the skin is paramount. This can be achieved by implementing skin-care products which contain sunscreen active ingredients that provide UV protection. Unfortunately, photo-degradation, toxicity, and photo-allergies limit the effectiveness of present day sunscreen ingredients. Currently, this is moderated by physically embedding within inert silica particles, but leaching of the active ingredient can occur, thereby negating protective efforts. Alternatively, this research details the preparation and investigation of bridged silsesquioxane analogues of commercial ingredients which can be chemically grafted to the silica matrix. Studies with bridged salicylate particles detail facile preparation, minimized leaching, and enhanced UV stability over physically encapsulated and pendant salicylate counterparts. In terms of UVB protective ability, the highest maintenance of sun protection factor (SPF) after extended UV exposure was achieved with bridged incorporation, and has been attributed to corollary UV stability. Additionally, bridged salicylate particles can be classified as broad-spectrum, and rate from moderate to good in terms of UVA protective ability. Particles incorporated with a bridged curcuminoid silsesquioxane were also prepared and displayed comparable results. As such, an attractive method for sunscreen isolation and stabilization has been developed to eliminate the problems associated with current sunscreens, all while maintaining the established UV absorbance profiles of the parent compound. To appreciate the technology utilized in this research, a thorough understanding of sol-gel science as it pertains to hybrid organic/silica particles, including methods of organic fragment incorporation and insight on the effect of incorporation method on ingredient leaching and UV stability, is vital. This was afforded by analysis of hybrid fluorescent dansyl particles, prepared by both O/W microemulsion polymerization and a modified Stöber process, which detailed that covalent entrapment of bridged dansyl silsesquioxane is the incorporation method of choice to ensure minimized leaching and enhanced UV stability. As such, use of this method can provide exciting applications in fields where stability and retainment of the embedded ingredient is paramount for efficacy.

Thesis (Ph.D.)--University of Alberta, 2010. / A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctor of Philosophy, Department of Chemistry. Title from pdf file main screen (viewed on April 10, 2010). Includes bibliographical references.

Protection against the harmful effects of ultraviolet radiation is of increasing importance due to the depletion of stratospheric ozone, which shields the earth from harmful UVC rays (in the range 200-280 nm) and some UVB rays (in the range 280-290 nm). In addition, as the skin is repeatedly exposed to solar radiation, the possibility exists that the incidence of skin cancer is enhanced. This has led to the increased use of commercial sunscreens, which apart from their benefits, also have undesirable effects such as photodegradation and skin penetration. We therefore studied the photodegradation of two sunscreen absorbers that are used in most sunscreen formulations. The combination of the UVB filter, 2-ethylhexyl-p-methoxycinnamate (EHMC), and the UVA filter, avobenzone (AVO), are commonly used in sunscreen products. These two filters are known to exhibit differing photostabilities in different media. The aim of this project was to investigate their photochemical behaviour in a polar and a non-polar solvent and to identify the UV-induced breakdown products. Methanol was chosen as the polar medium and cyclohexane as the non-polar medium. The sunscreen filters were irradiated either singly or in combination in the two solvents with wavelengths greater than 300 nm. The irradiated samples were analysed by UV-spectrophotometry, high performance liquid chromatography (HPLC) and gas chromatography (GC). The effects of direct irradiation with UVB and UVA light, quenchers and photosensitisers were also examined. EHMC is supplied commercially as the trans-isomer and upon irradiation photoisomerises, in both methanol and cyclohexane, to its cis-isomer. AVO is photostable in methanol but photodegrades in cyclohexane. This behaviour is also evident when mixtures of the two filters are irradiated. The loss in absorbance of both EHMC and AVO was monitored by UV-spectrophotometric analysis. Since EHMC does not absorb UV light at the wavelength of maximum absorbance of AVO, a method to quantify the amount of EHMC and AVO present in the mixture was devised. In order to identify the degradation products, HPLC and GC techniques were implemented. The photoproducts formed in the polar methanolic medium were separated and quantified by HPLC analysis. Gas chromatography with flame ionisation detection (GC-FID) was used to separate the photoproducts formed in the non-polar cyclohexane medium. Gas chromatography with mass-spectral detection (GC-MS) was used to identify the photoproducts formed upon irradiation of AVO and to show that UVA irradiation of AVO photosensitises the isomerisation of EHMC. The rate of a photochemical reaction depends upon a number of factors including the number of photons absorbed by sunscreen absorbers. Chemical actinometry was used to determine the number of photons absorbed by EHMC, AVO and the mixture of the two in methanol and cyclohexane. The number of photons absorbed by AVO in cyclohexane was used to determine the quantum yield for the photodegradation of AVO. We also determined the rate constants for EHMC photoisomerisation and AVO photodegradation. Finally, we investigated the effect of sunlight on commercial sunscreens containing EHMC and AVO. / Thesis (M.Sc.)-University of Natal, Durban, 2002.

Photoallergic contact dermatitis (PACD) is a clinical problem that has often been poorly understood and neglected by dermatologists over recent years. This can be partly attributed to its investigation by photopatch testing (PPT) falling between the expertise of photobiologists and contact dermatitis clinicians. One result of this situation was that no European Baseline PPT series had been agreed on. To redress this, the European multi centre photopatch test study (EMCPPTS) was conceived to provide up to date information on which photoallergens are of greatest clinical relevance. Its conduct and results form the core research project of this thesis. To enable the EMCPPTS to proceed and its results to be viewed in a wider context, the other Chapters of this thesis explore important related aspects of PACD and PPT in Europe. The introduction examines the nature of PACD and PPT and reviews current photoallergens. Then, the investigation of the two photoallergens carprofen and chlorproethazine by PPT is recounted. These studies highlight deficiencies within the current European regulatory system for preventing photoallergens from reaching the marketplace, as well as providing templates for the investigation of new photoallergens in the human environment. This is followed by a pilot PPT study which provides new information on the optimum non-irritating concentration of the 19 ultraviolet sunscreen absorbers to be used in the EMCPPTS. The issue of attempting to determine the photoallergenic potential of the EMCPPTS agents with respect to exposure patterns is addressed by conducting a sunscreen survey in the UK. The EMCPPTS itself is then detailed, as well as the difficulties that can be encountered when conducting a large clinical study of this nature. The results from the EMCPPTS and other presented studies were shown to be of importance in deciding upon a new European Baseline PPT series. The process involved in deciding this series, as well as its content are described before overall conclusions and possible future studies in the domain of PACD and PPT are discussed.

Em função da preocupação com a saúde do consumidor, a maioria das formulações cosméticas tem sido acrescida de filtros solares e substâncias ativas antioxidantes, tais como vitaminas, para a proteção dos danos causados na pele pelos raios solares, entretanto, o uso de associações fotoinstáveis pode levar à formação de intermediários reativos que podem promover dermatites de contato e reações fototóxicas na pele, o que leva à necessidade da comprovação da segurança desses produtos frente a exposição à radiação solar. Há um grande empenho da comunidade científica para a utilização de testes alternativos ao uso de animais de experimentação sendo que o teste de fototoxicidade 3T3 NRU PT, em cultura de fibroblastos tem sido o preconizado para a essa finalidade. Assim, o objetivo deste projeto foi a avaliação da fotoestabilidade e da fototoxicidade de formulações fotoprotetoras contendo diferentes associações de filtros solares e estabilizadores de filtros solares, associados ao retinol e ao palmitato de retinila, por meio do uso de CLAE e cultura de fibroblastos, respectivamente. Para tal, foram desenvolvidas formulações fotoprotetoras contendo diferentes filtros solares que foram acrescidas ou não de retinol ou de palmitato de retinila, e de estabilizadores de filtros solares, que são utilizados para melhorar a sua fotoestabilidade. Nesse estudo, amostras das formulações foram aplicadas em lâminas de vidro e expostas à radiação UVA/UVB, a seguir, foram realizadas análises por CLAE, para dosagem do teor de filtros solares e vitaminas, e foi realizado estudo de espectrofotometria no UV, em que foi determinada a razão da absorção na faixa UVA/UVB. A fototoxicidade das associações de filtros solares, estabilizadores e vitaminas foi avaliada por meio do uso de cultura de fibroblastos 3T3, que foi submetida à radiação UVA para a determinação da viabilidade celular na presença e ausência da radiação. Os resultados obtidos nos sugerem que, no estudo por CLAE, bemotrizinol foi considerado o melhor estabilizador para ambas as vitaminas. No estudo por espectrofotometria no UV, as formulações contendo avobenzona / vitaminas foram consideradas fotoinstáveis, e apenas o bemotrizinol aumentou a fotoestabilidade da avobenzona associada a ambas as vitaminas. No estudo de fototoxicidade, a avobenzona, o dietilexilnaftalato e o retinol apresentaram potencial fototóxico. As associações que continham avobenzona / palmitato de retinila e avobenzona / retinol foram consideradas fototóxicas. A presença do estabilizador dietilexilnaftalato reduziu o potencial fototóxico das associações avobenzona / vitaminas e a presença do estabilizador bemotrizinol reduziu o potencial fototóxico da associação avobenzona / palmitato de retinila. Os resultados encontrados no presente estudo são promissores uma vez que algumas associações consideradas fotoestáveis apresentaram potencial fototóxico, mostrando a importância da realização de ambos os estudos no desenvolvimento / avaliação de formulações fotoprotetoras estáveis e seguras ao uso. / Due to consumer health concern, many cosmetic formulations has been supplemented by UVfilters and antioxidants such as vitamins, for the protection of UV-induced skin damages; however, the use of photounstable combinations can lead to the formation of reactive intermediates which may induce contact dermatitis and phototoxic reactions in the skin, which leads to the necessity of proving the safety of these products before exposure to solar radiation. There is a great effort by the scientific community to promote the alternatives to animal testing, whereas the 3T3 NRU phototoxicity test in cultured fibroblasts has been validated and recommended for this purpose. The objective of this project was to evaluate the photostability and phototoxicity of sunscreen formulations containing different combinations of photostabilizers and UV-filters, combined with retinol and retinyl palmitate, by using HPLC and fibroblast cultures, respectively. For this purpose, sunscreen formulations developed with different UV-filters were added or not of retinol or retinyl palmitate, and photostabilizers, which are used to improve the photostability. Firstly, samples of the formulations were applied on glass slides and exposed to UVA / UVB radiation, then, they were analyzed by HPLC, to determine the concentration of UV-filters and vitamins, and by UV spectrophotometry, to determine the UVA / UVB absorption ratio. Phototoxicity of combinations of UV-filters, photostabilizers and vitamins was evaluated by using the 3T3 fibroblast cultures, which was exposed to UV radiation for the determination of cell viability in the presence and absence of radiation. The obtained results suggested that, in the HPLC study, bemotrizinol was considered the best photostabilizer for both vitamins. In the UV spectrophotometry study, formulations containing avobenzone / vitamins were considered photounstable, and only bemotrizinol increased photostability of avobenzone combined with both vitamins. In the phototoxicity study, avobenzone, diethylhexylnaphthalate and retinol showed phototoxic potential. The combinations containing avobenzone / retinyl palmitate and avobenzone / retinol were considered phototoxic. The presence of the stabilizer diethylhexylnaphthalate reduced the phototoxic potential of avobenzone / vitamins combinations and the presence of bemotrizinol reduces the phototoxic potencial of avobenzone / retinyl palmitate combination. The results of the present study are promissory since some combinations that were considered photostable presented phototoxic potential, showing the importance of performing both studies in the development / evaluation of stable and safe sunscreen formulations.

Made available in DSpace on 2014-06-11T19:25:27Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-06-28Bitstream added on 2014-06-13T18:53:26Z : No. of bitstreams: 1 manaia_eb_me_arafcf.pdf: 933779 bytes, checksum: d46491f2fe3590f23084880ccff5dbe8 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Universidade Estadual Paulista (UNESP) / A incidência de câncer de pele em todo o mundo cresce exponencialmente principalmente devido à exposição freqüente à radiação ultravioleta (UV). O uso de protetor solar é a medida mais eficaz para a sua prevenção. O dióxido de titânio (TiO2) é um filtro inorgânico que atua espalhando, refletindo e absorvendo a radiação UV, é fotoestável, hipoalergênico, entretanto, deixa a pele com aspecto esbranquiçado dependendo do tamanho da partícula. Hoje em dia há uma procura grande por produtos multifuncionais e o uso de estruturas líquido-cristalinas vem crescendo cada vez mais por promover a liberação controlada de ativos. O objetivo deste trabalho foi desenvolver sistemas multifuncionais líquido-cristalinos contendo nanopartículas de TiO2 transparentes capazes de agir como fotoprotetores e de liberar terpinem-4-ol (terpeno com atividade antioxidante) de forma controlada prevenindo e/ou tratando o câncer de pele. O teste de citotoxicidade mostrou que as nanopartículas de TiO2 obtidas através do processo sol-gel não foram citotóxicas para as duas linhagens de células testadas (queratinócitos de pele humana – HaCaT e fibroblastos de pulmão humano – MRC-5), evidenciando o uso deste material nos humanos sem causar danos. O potencial zeta das nanopartículas indicou que entre pH 5 e 7, que não é agressivo para pele humana, é possível evitar aglomeração das nanopartículas por estas apresentarem cargas superficiais significativas. Os dados de espalhamento de raios X a baixo ângulo e microscopia de luz polarizada mostraram que foi possível manter a estrutura líquido-cristalina das formulações com a presença de nanopartículas de TiO2 e terpinem-4-ol. O teste de liberação in vitro das formulações contendo 1 e 5% de terpinem-4-ol mostraram que o sistema líquido-cristalino controlou... / The incidence of skin cancer growth exponentially in all the world mainly due to the frequent ultraviolet (UV) radiation exposition. The sunscreen use is one of the efficient manners to prevent the skin cancer. The titanium dioxide (TiO2) is an inorganic filter which works scattering, reflecting and absorbing the UV radiation, it is photostable, hypoalergenic, but it presents a whiteness appearance depending on the particle size. Nowadays there is a high demand for multifunctional products and the use of liquid crystal has been increasing because it promotes active controlled delivery. The propose of this work is to develop liquid crystalline multifunctional systems with transparent TiO2 nanoparticles able to photoprotect the skin and release in a controlled manner terpinem-4-ol (a terpen with antioxidant activity) to prevent and/or treat the skin cancer. The citotoxicity assay showed that TiO2 nanoparticles obtained by sol-gel process weren´t cytotoxics to the two cell lines tested (human skin keratinocites – HaCaT and human lung fibroblasts – MRC-5), evidencing the use of this material on the humans without dangers. The nanoparticles zeta potential indicated that at pH about 5 and 7, pH that is not irritative to the human skin, it´s possible to prevent nanoparticles aggregation due to their significative superficial charges. The small angle scattering X rays and light polarized microscopy data showed that it is possible to maintain the liquid crystalline structure of the formulations with the presence of TiO2 nanoparticles and terpinem-4-ol. The in vitro terpinem-4-ol release assay of the formulations containing 1 and 5% of terpinem-4-ol showed the controlled release of the liquid crystalline systems (liberation at about 13% in 12 hours), being zero order the best mathematical model that fit the release profile, indicating... (Complete abstract click electronic access below)

Made available in DSpace on 2014-08-13T14:50:59Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-05-19Bitstream added on 2014-08-13T17:59:46Z : No. of bitstreams: 1 000773729.pdf: 3475538 bytes, checksum: 018064f79c4dfcc8527c0ab0dfe5c68d (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / A exposição à radiação ultravioleta (UV) é um dos principais fatores que contribuem para o desenvolvimento de câncer de pele e fotoenvelhecimento. Este trabalho teve como objetivo a obtenção de novos filtros solares com capacidade ampliada de proteção contra radiação UVA e UVB associada a propriedades antioxidantes, obtidos através da estratégia de hibridação molecular, entre filtros existentes (avobenzona e metoxicinamato de octila) e produtos naturais (resveratrol e ácido ferúlico). Foram sintetizados, isolados e caracterizados oito compostos inéditos obtidos através de hibridação molecular: (E)-4-hidroxi-N'-(4-hidroxibenzilideno)benzidrazida (molécula I), (E)-N'-(3,5-diidroxibenzilideno)-4-hidroxibenzidrazida (molécula II), (E)-4-(terc-butil)-N'-(3,5-diidroxibenzilideno)benzidrazida (molécula III), (E)-4-(terc-butil)-N'-(4-hidroxibenzilideno)benzidrazida (molécula IV), (E)-4-hidroxi-N'-((E)-3-(4-metoxifenil)alilideno)benzidrazida (molécula V), (E)-4-(terc-butil)-N'-((E)-3-(4-metoxifenil)alilideno)benzidrazida (molécula VI), (E)-4-hidroxi-N'-((E)-3-(4-hidroxi-3-metoxifenil)alilideno)benzidrazida (molécula VII) e (E)-4-(terc-butil)-N'-((E)-3-(4-hidroxi-3-metoxifenil)alilideno)benzidrazida (molécula VIII). O composto VIII apresentou-se como o mais termoestável, decompondo-se acima de 295°C. Na avaliação da atividade antioxidante, os compostos I, IV, VII e VIII apresentaram maior atividade, sendo os compostos VII e VIII semelhantes aos padrões ácido ferúlico, t-resveratrol e ácido ascórbico. Os resultados obtidos no ensaio de atividade fotoprotetora demonstraram capacidade protetora contra radiação UVA para os compostos I, IV, V, VI, VII e VIII, sendo todos comparáveis ao padrão t-resveratrol. O composto VI apresentou-se como o mais ativo quanto à capacidade fotoprotetora UVA sendo, inclusive, superior ao padrão t-resveratrol. Os compostos II e III foram classificados como potenciais filtros UVB e ... / The exposure to ultraviolet radiation is the mainly factor to develop skin cancer and photoaging. This work aimed to obtain new sunscreens with enhance abilities to protect against UVA and UVB radiation associated to antioxidant properties, obtained by molecular hybridization strategy among existing filters (avobenzone and methoxycinnamate) and natural products (resveratrol and ferulic acid). Eight new compounds were synthesized, isolated and characterized by molecular hybridization: (E)-4-hydroxy-N'-(4-hydroxybenzylidene)benzohydrazide (molécula I), (E)-N'-(3,5-dihydroxybenzylidene)-4-hydroxybenzohydrazide (molécula II), (E)-4-(tert-butyl)-N'-(3,5-dihydroxybenzylidene)benzohydrazide (molécula III), (E)-4-(tert-butyl)-N'-(4-hydroxybenzylidene)benzohydrazide (molécula IV), (E)-4-hydroxy-N'-((E)-3-(4-methoxyphenyl)allylidene)benzohydrazide (molécula V), (E)-4-(tert-butyl)-N'-((E)-3-(4-methoxyphenyl)allylidene)benzohydrazide (molécula VI), (E)-4-hydroxy-N'-((E)-3-(4-hydroxy-3-methoxyphenyl)allylidene)benzohydrazide (molécula VII) and (E)-4-(tert-butyl)-N'-((E)-3-(4-hydroxy-3-methoxyphenyl)allylidene)benzohydrazide (molécula VIII). Compound VIII was presented as the most thermostable, showing decomposition temperature above 295°C. Compounds I, IV, VII and VIII presented more antioxidant activity than the other compounds analysed. The compounds VII and VIII were similar to ferulic acid, t-resveratrol and ascorbic acid. Compounds I, IV, V, VI, VII and VIII had abilities to protect against UVA radiation, and all of these products were similar to t-resveratrol pattern. The VI molecule had the highest photoprotection activity against UVA radiation, and it was more effective than t-resveratrol pattern. The II and III compounds were classified as UVB filters and they were more effectiveness than t-resveratrol. Compounds I, III, V and VII showed inhibitory ability for the enzyme tyrosinase, respectively, ...