Binding Interaction of Gemini Surfactants with Nanotubes of β‐Cyclodextrin and Controlled Release of Guest Molecules: Effect of Spacer Chain Length and Concentration of Surfactants

Abstract

AbstractThe formation of guest molecule (Coumarin 485, C‐485) induced nanotubes by β‐cyclodextrin (β‐CD) and their interactions with cationic gemini surfactants (12‐n‐12, where n=3, 6, and 12) have been explored by means of UV‐visible absorption, steady‐state fluorescence and fluorescence anisotropy, time‐resolved fluorescence and fluorescence anisotropy, and dynamic light scattering (DLS) measurements. β‐CD at its high concentration form extended nanotubes and secondary aggregates of nanotubes. A gemini surfactant has a significant role in binding interactions between C‐485 and nanotubes of β‐CD. In a low concentration range, surfactant molecules are co‐associated with the guest molecules, C‐485, however, at high concentrations, they are capable of pushing C‐485 out of the nanotubular cavities. A gemini molecule with a comparatively longer spacer chain is more efficient in removing the guest molecules out of the nanotubular cavities. Also, the rate of release of guest molecules increases with increasing concentration of surfactants. Release of guest molecules from the nanotubes can be tuned by changing the spacer chain length and concentration of gemini surfactants. Guest molecules after coming out of the nanotubular cavities, get solubilized in the micelles formed by surfactant molecules in the solution. The results of the present work suggest potential application in the development of promising drug delivery systems.