New insight into the structure of CTAB micelles in the presence of cyclodextrins, using non-steroidic anti-inflammatory agents - Nabumetone, Naproxen - As fluorescent probes

Abstract

[EN]The structure of CTAB micelles in the presence of α-, β- and hydroxypropyl-β-cyclodextrin has been investigated by means of conductivity and spectroscopic measurements – absorption and steady state fluorescence – using Naproxen, Nabumetone and pyrene as probes. In the presence of the three cyclodextrins, two types of micelles have been detected. The first type is a pure surfactant micelle, while the other is formed by surfactant monomers complexed with cyclodextrins. The presence of cyclodextrins produces a decrease in the cmc of the pure micelle. The second type of micelle is formed at higher cmc* values, 25.6 × 10-4 M, 27.8 × 10-4 M and 38.9 × 10-4 M for α-, β-, and HPβCD respectively. A significant increase in the ionisation degree has been detected. The aggregation number is strongly increased, being 92 ± 3 , 97 ± 3 and 80 ± 2 for for α-, β-, and HPβCD respectively. The polarity of this micelle decreases, indicating that it becomes tighter and its hydrophobic region becomes less polar.