Binding of a potential chloride channel blocker with an anionic surfactant and subsequent release in solution: effect of a hydrotropic solute in the post-micellar region

Abstract

The present work demonstrates a thorough description of the differential interactions of a potential chloride channel blocker, 9-methyl anthroate (9-MA), with a charged surfactant, sodium dodecyl sulfate (SDS), in the pre- and post-micellar regime along with the consequences of the addition of a hydrotropic salt in the post-micellar region. The modulated photophysical properties of the emissive probe within the biomimetic environment have been spectroscopically monitored to gain an insight into the binding interaction. The moderate strength of the binding phenomenon as revealed by Benesi–Hildebrand analysis, as well as the hindrance exerted by the binding process towards the aggregation of the surfactants, paves the way to rationalize the observation of the exclusion of the drug to the bulk after micelle formation to be an outcome of a free energy advantage in the thermodynamically favorable micellization process. A substantial increase in the bulk viscosity of the medium in the presence of the hydrotrope in the post-micellar region coupled with a non-covalent binding between the alkane chains of the salt and the hydrophobic drug has also been unveiled from steady state and time-resolved fluorimetric perspectives.