Effect of surfactant head group on micellization and morphological transitions in drug-Surfactant catanionic mixture: A multi-technique approach

Abstract

Abstract This work aims to explore the various interactions prevailing in catanionic mixtures of cationic amphiphilic drug tetracaine hydrochloride (TC) and anionic surfactants viz. sodium lauroyl sarcosinate (SLS) and sodium dodecylbenzenesulfonate (SDBS). The synergistic interactions in terms of micellar, interfacial and thermodynamic parameters in binary mixtures of TC and SLS/SDBS have been investigated by employing surface tension measurement. The microenvironment of TC in micellar media, the binding constant and the stoichiometry of catanionic complexes have been examined from steady state fluorescence, three dimensional (3D) fluorescence and UV–vis spectroscopy. The thermodynamic heat changes were also investigated by using isothermal titration calorimetry (ITC). The more exothermic heat changes were observed in TC + SDBS in comparison to TC + SLS mixture owing to the presence of strong electrostatic, hydrophobic and π-π stacking interactions in former. Furthermore the effect of different head groups on the morphology and hydrodynamic diameter (Dh) were explored using, dynamic light scattering (DLS) and transmission electron microscopy (TEM) techniques. We observed the morphological transition such as vesicle formation in TC-SDBS mixtures at different mole fractions of TC whereas in TC-SLS the Dh values first increases with increasing mole fraction of TC and then decreases which signifies only the changes in micellar aggregates and no transition to larger aggregates. This work speculate the potential of TC and SLS/SDBS mixtures which can be used as drug carriers to alter physicochemical and pharmacokinetic characteristics of drugs.