Desenvolvimento e caracterização de sistemas de delivery tópicos para ácido ascórbico: estudos comparativos
Data
2020-01-30
Autores
Caritá, Amanda Costa [UNIFESP]
Orientadores
Leonardi, Gislaine Ricci [UNIFESP]
Tipo
Tese de doutorado
Título da Revista
ISSN da Revista
Título de Volume
Resumo
O ácido ascórbico ou Vitamina C (Vit C) é um antioxidante potente, capaz de atuar de forma relevante tanto na prevenção quanto no tratamento do processo de envelhecimento cutâneo. No entanto, para apresentar eficácia terapêutica, a Vit C deve ser mantida estável e deve atingir o sítio-ativo desejado de forma sustentada. Apesar de a literatura conter diversos estudos empregando diferentes mecanismos para o delivery de Vit C, os resultados obtidos são limitados. Objetivos: Aqui, propusemos o desenvolvimento e caracterização de emulsões providas de estruturas líquido-cristalinas, de lipossomas catiônicos “convencionais” e ultradeformáveis e de emulsões estabilizadas por partículas sólidas, também chamadas de emulsões Pickering, para o delivery tópico de Vit C. Métodos: Todas as formulações foram preparadas com 5 % de Vit C. Emulsões compostas por Álcool cetílico e Polysorbato 60 foram desenvolvidas e caracterizadas por Microscopia Óptica e Polarizada, Microscopia Eletrônica de Transmissão, Calorimetria Diferencial de Varredura e Espalhamento de Raios-X. A estabilidadade química da Vit C na formulação foi verificada sob estocagem em diferentes temperaturas através de análises de Cromatografia Líquida de Alta Eficiência. Lipossomas compostos por Fosfatidilcolina de soja, pelo lipídio catiônico 1,2 dioleoil-3-trimetil amônio propano (DOTAP) e colesterol foram desenvolvidos. O surfactante Polissorbato 80 foi utilizado para conferir o caráter ultradeformável à formulação. Os sistemas foram caracterizados por Espalhamento de Luz Dinâmico, Potencial Zeta, Calorimetria de Titulação Isotérmica, Medições de Tensão de Linha, Citotoxicidade e Crio-Microscopia eletrônica. Emulsões Pickering O/A foram desenvolvidas com Laponita RD e Triglicerídeos de ácido cáprico/caprílico. A proporção de óleo nas formulações foi variada de 10 % a 90 %. Modificações de superfície foram realizadas nas partículas de Laponita através da adição do surfactante catiônico Cloreto de dimetildioctadecilamônio (DODAC). As formulações foram caracterizadas por Microscopia Óptica e Espalhamento de Luz. O perfil de permeação de todos os sistemas desenvolvidos foi verificado através do método de Células de Franz em pele de porco. Resultados: As emulsões com cristais líquidos apresentam uma estrutura coloidal com coexistência de fases lamelar líquido-cristalina e gel-cristalina, capaz de proteger a Vit C contra a degradação e promover retenção cutânea. Os sistemas lipossomais apresentaram boa estabilidade física e a ausência de toxicidade foi verificada. O surfactante Polysorbato 80 é incorporado na bicamada lipídica e altera suas propriedades, como a tensão de linha. O lipídio catiônico DOTAP favoreceu a eficácia de encapsulamento da Vit C devido a interações eletrostáticas. Todavia, o perfil de permeação encontrado foi semelhante nas duas formulações lipossomais, o que pode ser explicado pela contribuição da Vit C não encapsulada na fase externa dos lipossomas. Para as emulsões de Pickering O/A, os resultados mais interessantes foram obtidos com formulações desenvolvidas com proporções intermediárias de óleo, devido à ausência de sedimentação e melhor emulsificação. A adição de DODAC ao sistema orienta a formação de emulsões A/O, diminui consideravelmente o tamanho das gotas das emulsões e altera o aspecto da formulação, que passa a possuir um aspecto leitoso. Experimentos de permeação cutânea mostram uma maior absorção da Vit C nas camadas mais profundas da pele. Conclusões: Dentre as formulações desenvolvidas, a emulsão com cristais-líquidos se destaca pela estabilização da Vit C e pela capacidade de retenção cutânea. As formulações lipossomais apresentaram resultados físico-químicos interessantes, todavia, até o momento, não foi possível verificar uma alteração no perfil de permeação dentre os sistemas estudados. As emulsões Pickering, no melhor de nosso conhecimento, foram utilizadas pela primeira vez para o delivery de Vit C no presente trabalho. A estabilização através de partículas sólidas confere propriedades peculiares ao sistema e maiores investigações podem ser realizadas para otimizar a entrega de Vit C através deste tipo de formulação.
Ascorbic acid or Vitamin C (Vit C) is a potent antioxidant, very efficient in the prevention and treatment of the skin aging. However, for therapeutic efficacy, Vit C must be kept stable and reach the active site in a sustained way. Although the literature contains several studies employing different mechanisms for skin delivery of Vit C, the results obtained are limited. Objectives: In this study, we proposed the development of emulsions with liquid-crystalline structures, “conventional” and ultradeformable cationic liposomes and emulsions stabilized by solid particles, called Pickering emulsions, for the skin delivery of Vit C. Methods: All formulations contained 5 % of Vit C. Emulsions composed by Cetyl alcohol and Polysorbate 60 were developed and characterized by Optical and Polarized Microscopy, Transmission Electron Microscopy (TEM), Differential Scanning Calorimetry and Xray techniques. The chemical stability of Vit C in the formulations was checked upon storage in different conditions of temperature by High Performance Liquid Chromatography. Liposomes composed of Soybean phosphatidylcholine, 1,2-dioleoyl-3-trimethylammoniopropane (DOTAP, a cationic lipid) and cholesterol were developed. For ultradeformable liposomes, the surfactant Polysorbate 80 was added to the formulation. The systems were characterized by Dynamic Light Scattering, Zeta Potential, Isothermal Titration Calorimetry, Edge Tension measurements, Cytotoxicity and Cryo-TEM. W/O Pickering emulsions composed by Laponite RD and Caprylic/capric triglycerides were developed. The amount of oil ranged from 10 % to 90%. For the development of W/O emulsions, the Laponite RD was modified with the cationic surfactant Dimethyldioctadecylammonium chloride (DODAC). The formulations were characterized by Optical Microcopy and Static Light Scattering. The permeation profile of all developed systems was checked by the Franz Cells method in pig skin. Results: The emulsion with liquid-crystal contains a complex colloidal structure, consisting of lamellar liquid crystalline and lamellar gel crystalline phases, able to protect Vit C against degradation and promote skin retention. The liposomal systems showed good physical stability and are non-cytotoxic. Polysorbate 80 is incorporated into the lipid bilayer and alters its properties, such as edge ension. The cationic lipid DOTAP favored the encapsulation efficiency of Vit C due to electrostatic interactions. However, the permeation profile found was similar in both liposomal formulations, which could be explained by the contribution of nonencapsulated Vit C in the external phase of the liposomes. For Pickering O/W emulsions, the most interesting results were obtained with formulations developed with intermediate oil proportions, due to the absence of creaming and better emulsification. The addition of DODAC into the system guides the formation of W/O emulsions, considerably decreases the emulsion droplet size and alters the visual appearance, giving rise to a milky formulation. Skin permeation experiments show a greater absorption of Vit C in the deeper layers of the skin. Conclusions: Among the formulations developed, emulsions with liquid crystals stand out for their stability and skin retention capacity. The liposomal formulations presented interesting physicochemical results, however, it was not possible to verify a change in the permeation profile among the studied systems. To the best of our knowledge, Pickering emulsions were used for the first time for skin delivery of Vit C in the present work. Solid particle stabilization confers unique properties to the system and further investigation can be undertaken to optimize Vit C delivery through this type of formulation.
Ascorbic acid or Vitamin C (Vit C) is a potent antioxidant, very efficient in the prevention and treatment of the skin aging. However, for therapeutic efficacy, Vit C must be kept stable and reach the active site in a sustained way. Although the literature contains several studies employing different mechanisms for skin delivery of Vit C, the results obtained are limited. Objectives: In this study, we proposed the development of emulsions with liquid-crystalline structures, “conventional” and ultradeformable cationic liposomes and emulsions stabilized by solid particles, called Pickering emulsions, for the skin delivery of Vit C. Methods: All formulations contained 5 % of Vit C. Emulsions composed by Cetyl alcohol and Polysorbate 60 were developed and characterized by Optical and Polarized Microscopy, Transmission Electron Microscopy (TEM), Differential Scanning Calorimetry and Xray techniques. The chemical stability of Vit C in the formulations was checked upon storage in different conditions of temperature by High Performance Liquid Chromatography. Liposomes composed of Soybean phosphatidylcholine, 1,2-dioleoyl-3-trimethylammoniopropane (DOTAP, a cationic lipid) and cholesterol were developed. For ultradeformable liposomes, the surfactant Polysorbate 80 was added to the formulation. The systems were characterized by Dynamic Light Scattering, Zeta Potential, Isothermal Titration Calorimetry, Edge Tension measurements, Cytotoxicity and Cryo-TEM. W/O Pickering emulsions composed by Laponite RD and Caprylic/capric triglycerides were developed. The amount of oil ranged from 10 % to 90%. For the development of W/O emulsions, the Laponite RD was modified with the cationic surfactant Dimethyldioctadecylammonium chloride (DODAC). The formulations were characterized by Optical Microcopy and Static Light Scattering. The permeation profile of all developed systems was checked by the Franz Cells method in pig skin. Results: The emulsion with liquid-crystal contains a complex colloidal structure, consisting of lamellar liquid crystalline and lamellar gel crystalline phases, able to protect Vit C against degradation and promote skin retention. The liposomal systems showed good physical stability and are non-cytotoxic. Polysorbate 80 is incorporated into the lipid bilayer and alters its properties, such as edge ension. The cationic lipid DOTAP favored the encapsulation efficiency of Vit C due to electrostatic interactions. However, the permeation profile found was similar in both liposomal formulations, which could be explained by the contribution of nonencapsulated Vit C in the external phase of the liposomes. For Pickering O/W emulsions, the most interesting results were obtained with formulations developed with intermediate oil proportions, due to the absence of creaming and better emulsification. The addition of DODAC into the system guides the formation of W/O emulsions, considerably decreases the emulsion droplet size and alters the visual appearance, giving rise to a milky formulation. Skin permeation experiments show a greater absorption of Vit C in the deeper layers of the skin. Conclusions: Among the formulations developed, emulsions with liquid crystals stand out for their stability and skin retention capacity. The liposomal formulations presented interesting physicochemical results, however, it was not possible to verify a change in the permeation profile among the studied systems. To the best of our knowledge, Pickering emulsions were used for the first time for skin delivery of Vit C in the present work. Solid particle stabilization confers unique properties to the system and further investigation can be undertaken to optimize Vit C delivery through this type of formulation.