Interaction of pyrimethamine and sulfadiazine with ionic and neutral micelles: Electronic absorption and fluorescence studies

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• 作者：Gilderman Silva Lá ; zaro ; Adelmo Lima Meneses Jr. ; Osmir Fabiano Lopes de Macedo ; Iara de Fá ; tima Gimenez ; Nivan Bezerra da Costa Jr. ; Ledjane Silva Barreto ; Luí ; s Eduardo Almeida
• 关键词：Antitoxoplasmosis drugs ; Pyrimethamine ; Sulfadiazine ; Surfactant ; Micelles ; Binding constant
• 刊名：Colloids and Surfaces A ; Physicochemical and Engineering Aspects
• 出版年：2008
• 期刊代码：22_09277757
• 类别：ch
• 出版时间：1 July 2008
• 卷：324
• 期：1-3
• 页码：98-104
• 文件大小：469 K

摘要

The binding of two antitoxoplasmosis drugs, pyrimethamine (PYR) and sulfadiazine (SDZ) to cationic cetyltrimethylammonium chloride (CTAC), anionic sodium dodecylsulfate (SDS), zwiterionic N-hexadecyl-N,N-dimethyl-2-ammonium-1-propanesulfonate (HPS) and neutral polyoxyethylene-dodecyl-ether (Brij-35^®) micelles was studied using absorption and fluorescence spectroscopic methods. The pK_a of PYR changed in the presence of charged anionic, cationic and zwiterionic micelles, indicating that interaction is influenced by the micellar charge. For SDZ, pK_a changes were lower than 1 for all micelles, suggesting the occurrence of low binding constants in addition to a reasonable influence of the micellar charge. The values of binding constants K_b, obtained from fluorescence measurements, for PYR to CTAC micelles were very low at pH 4.0, where the drug is in a complete protonated state, increasing at pH 9.0 to long-chained CTAC and HPS micelles since this factor also favors accomodation of the neutral drug in the hydrophobic compartments. For SDZ the binding constants were determined from optical absorption measurements. Low binding constants were observed to charged surfactant micelles, with influence of micellar charge. It must be stated however that those values can be underestimated due to the relatively low sensitivity of the method based on absorption measurements.