Estudos físico-químicos do corante rosa de bengala B e seus derivados ésteres visando aplicações fotodinâmicas

• Ano de defesa: 2013
• Autor(a) principal: Pereira, Paulo Cesar de Souza
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Estadual de Maringá; Brasil; Departamento de Química; Programa de Pós-Graduação em Química; UEM; Maringá, PR; Centro de Ciências Exatas
• Palavras-chave em Português: Corante rosa de bengala; Terapia fotodinâmica; Inativação fotodinâmica; Microorganismos; Corantes xantenos; Fotosensibilizadores; Sistemas surfactantes; Solubilização; Drogas hidrofóbicas; Modificação estrutural; Propriedades fotofísicas; Brasil.; Photodynamic therapy; Photodynamic inactivation of microorganisms; Xanthene dyes; Surfactants systems; Brazil.; Ciências Exatas e da Terra; Química
• Link de acesso: http://repositorio.uem.br:8080/jspui/handle/1/3894

Photodynamic therapy (PDT) and photodynamic inactivation of microorganisms (PDIMO) are clinical modalities that are based on the excitation of a photosensitizer compound with light in the visible region of the electromagnetic spectrum, to generate cytotoxic chemical species, among which stands out the oxygen singlet (1O2). The xanthene dye Rose Bengal B (RBB) is one of known compounds with a higher quantum yield of singlet oxygen generation. However, his character preferably hydrophilic not favor their interaction with biomembranes, a main target sites of action of PDT and PDIMO. The present study evaluated the physico-chemical and photo-physical properties of the RBB and some of its derivatives esters. The modification on the molecular structure of RBB was made by insertion of alkyl chains of different sizes in order to make derivatives more hydrophobic and thus increase its affinity for membrane model systems formed by micelles. Beyond to the RBB were evaluated RBB methyl ester (RBBMET) RBB butyl ester (RBBBUT) and RBB decyl ester (RBBDEC) in aqueous environment and anionic (SDS), nonionic (P-123), and cationic (CTAB) micelles. Were evaluated the hydrophilichydrophobic balance, the acid-base equilibrium, binding parameters and location in micellar environments. The photo-physical properties such as quantum yields of the fluorescence and singlet oxygen, as well as the photo-activity in the inactivation of microorganisms were also measured. Synthesis of ester derivatives of RBB were relatively simple and reproducible, with high yields of purified product. The determination of pKa values for the protolytic equilibriums of the RBB showed a complex task due to the coexistence of tautomeric equilibrium checked in xantênicos dyes. However, the use of multivariate chemometric methodology with data associated and compared with the pKa of the ester derivatives made possible the identification and assignment of RBB pKa values. An effect of reversing pKa between phenol and carboxylic acid groups was detected when the RBB was allocated in the hydrophobic core of the micelles. The hydrophobicity of the dyes was evaluated by measuring its partition coefficient between the 1-octanol/water system. It was observed that the hydrophilic/hydrophobic balance of ester derivatives is modulated by the amount of carbons that comprise the alkyl chain, and a greater number of the methylene units results in increased hydrophobicity of dyes, favoring their primary interaction with biological membranes. The micellar environments evaluated influence on the absorption and emission spectra of dyes, with verification of displacements to the red (bathochromic shift). These changes are attributed to differences in polarity between the microenvironment inside the micelle and the aqueous solution. Binding dye-micelle constants were modulated by the hydrophobicity of the dyes as well as by the charge of the polar head groups of the surfactant molecules. The relative depth of location was determined by fluorescence quenching, which confirmed the influence of the hydrophobicity and charge of the dyes and micelles. The order of the binding constant values was RBBDEC > RBBBUT > RBBMET > RBB for all micelles, and CTAB > P -123 > SDS for all dyes. The values of fluorescence quantum yields are relatively small and have slightly increased when the dye is encapsulated. The values of the quantum yields of singlet oxygen formation inside of the micelles are high and similar to each other, independently of the dye or surfactant system evaluated. Assays with cultures of bacteria S. aureus showed which all evaluated dyes have activity against microorganism by photo-inactivation, and so are candidates to photosensitizer drugs for use in photodynamic therapy (PDT) and photodynamic inactivation of micro -organisms (PDIMO).