Navegando por Palavras-chave "Xanthene"

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    Chemical equilibria of Eosin Y and its synthetic ester derivatives in non-ionic and ionic micellar environments
    (W. Schröer, 2021-04-01) Freitas, Camila Fabiano de; Estevão, Bianca Martins; Pellosi, Diogo Silva [UNIFESP]; Scarminio, Ieda Spacino; Caetano, Wilker; Hioka, Noboru; Batistela, Vagner Roberto; http://lattes.cnpq.br/4319283598735971
    Eosin (EOS) and its synthetic ester derivatives have adequate properties to be employed as histological markers for and as drugs for photodynamic therapy. However, they present a very complex protolytic and tautomeric equilibrium that reflects on their photophysical properties. Hence their biomedical applications are strongly affected by the medium's pH, charge and hydrophobicity. In this study, we evaluated the effects of two neutral (Pluronic® F-127 and P-123) and two ionic (anionic SDS and cationic CTAB) surfactant micelles as a simple membrane model on the protolytic/tautomeric equilibrium of EOS and its ester derivative dyes. Multivariate analysis based on Q-Imbrie's factor and the K-matrix method on the electronic absorption spectroscopy data in different pH conditions allowed for the understanding of the complex protolytic/tautomeric equilibrium, and the influence of medium microenvironment on the EOS dyes at each pH. Our results demonstrated that, when close to physiological pH (~7.4), and electrostatic attraction towards cationic surfaces favor dyes locating close to the micelle's (biomembrane model) interface, where their biomedical applications are favored. Therefore, the analysis in different environments shows that the interactions of EOS and its derivatives with biomembranes can be modulated based on the hydrophobicity of the xanthene derivative and the cell membrane charge.
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    Multivariate analysis of protolytic and tautomeric equilibria of Erythrosine B and its ester derivatives in ionic and non-ionic micelles
    (W. Schröer, 2020-09-01) Freitas, Camila Fabiano de; Vanzin, Douglas; Braga, Thais Lazzarotto; Pellosi, Diogo Silva [UNIFESP]; Batistela, Vagner Roberto; Wilker, Caetano; Noboru, Hioka; http://lattes.cnpq.br/4319283598735971
    Erythrosine B (ERY) is a xanthene dye that has been widely used in recent years as a photoactive drug for Photodynamic Therapy. However, application of ERY and its derivatives as photosensitizer drugs depend not only on their singlet oxygen quantum yield, but also on their hydrophobicity, and photoactive protolytic and tautomeric species. In this work, the objective was to evaluate the acid-base equilibria of ERY and its derivatives: erythrosine methyl ester (ERYMET); erythrosine butyl ester (ERYBUT) and erythrosine decyl ester (ERYDEC), in biomimetic media (micelles of SDS and CTAB) as well as in some drug delivery systems of triblock copolymer Poloxamer (P-123 and F-127). All protolytic chemical equilibria were studied by employing chemometric multivariate analysis based on the Imbrie's Q-Mode Factor Analysis and k-Matrix methods. Tautomeric equilibria were evaluated taking into account of possible chemical structures and electronic spectroscopic approximations. Results from ester derivatives presenting only one protolytic equilibrium (at the phenolate group) and two possible tautomers, allow us to determine that protolytic equilibria follow the sequence pKaCOOH < pKaOH in SDS media for ERY by structure comparison. On the other hand, CTAB and polaxamers inverted the acidity of ERY protolytic groups (pKaOH < pKaCOOH) due to changes in the tautomeric equilibrium due to a lactone formation for the dyes neutral protolytic species inside the micelles. Chemometric approaches provided detailed analyses of protolytic/tautomeric equilibria of ERY. Through this, we achieved a deeper understanding of how ERY and its derivatives are affected by microenvironments in biomimetic and drug delivery systems.