Cosolubilization of Coumarin30 and Warfarin in Cationic, Anionic, and Nonionic Micelles: A Micelle-Water Interfacial Charge Dependent FRET.

Abstract

Solubilization of structurally varied coumarins, viz., Warfarin (WF; a 4-hydroxy coumarin) and Coumarin30 (C30, a 7-amino coumarin) individually and in mixed states (cosolubilization) within the aqueous surfactant self-assemblies of varying architectures has been explored, exploiting steady-state, time-resolved fluorimetric, and spectrophotometric techniques. Cosolubilization studies within micelles, which have rarely been done in the literature, were specifically undertaken with the aim of understanding the effect of micelles on their photophysical phenomena when simultaneously present within these nanocarriers and assess their prospective use as an efficient FRET pair. WF solubilizes within CTAB micelles, whereas little or no solubilization is observed in Brij30 and SDS micelles. On the other hand, C30 solubilizes deep into the palisade layer of CTAB micelles, between negatively charged head groups in SDS micelles and between OE groups in Brij30 micelles. C30 and WF maintain their solubilization sites during cosolubilization. In SDS and Brij30 micelles, an increase in WF causes fluorescence quenching of C30 molecules, while in CTAB, an increase in WF causes an increase in fluorescence of C30 by excited WF molecules indicating FRET between the two molecules.