Molecular interactions of cationic/anionic surfactants in presence of anionic antibiotic drug cloxacillin sodium at different temperatures: Micellization and thermodynamic studies.

• Discuss interactions of three ionic surfactants with antibiotic drug cloxacillin sodium (ClxNa) at different temperatures. • The ClxNa disfavors the micellization of CTAB and TTAB whereas it favors SDS at higher [ClxNa]. • The CMC values show a U-shaped curve against temperature for all the studied systems. • Thermodynamic parameters reveal that the micellization of studied surfactant–ClxNa systems is entropically driven. The physicochemical properties and interactions of surfactant–drug aggregates are regarded as essential features to achieve optimum therapeutic action of the drug. In this article, the effect of various concentrations of anionic antibiotic drug cloxacillin sodium (ClxNa) on the micellization of cationic surfactants such as cetyltrimethylammonium bromide (CTAB), tetradecyltrimethylammonium bromide (TTAB) and anionic surfactant sodium dodecyl sulphate (SDS) have been investigated using electrical conductance measurement at different temperatures (288.15 K, 293.15 K, 298.15 K, 303.15 K, 308.15 K, and 313.15 K). The results suggest an increase in critical micelles concentration (CMC) values for cationic surfactants (CTAB/TTAB) with a rise in drug concentration (0 mM up to 10 mM) whereas anionic surfactant SDS shows a decrease in CMC at higher drug concentrations (from 2.5 mM up to 10 mM) at all the studied temperatures. The degree of counterion dissociation (α) values for TTAB aggregates show a slight increase with [ClxNa], except at a few lower temperature ranges whereas such a regular trend was not obtained for CTAB and SDS aggregates. Temperature-dependent CMC values show a nonlinear nature with a rise in temperatures and follow a U-shaped curve for all studied pure surfactant and surfactant–ClxNa systems. Micellization for all surfactant-drug systems is found to be spontaneous. Investigation of other temperature-dependent thermodynamic parameters such as change in standard enthalpy ( Δ H m 0), and entropy ( Δ S m 0) of micellization suggest that surfactant–drug interactions are both endothermic ( Δ H m 0 < 0, particularly at lower temperatures) and exothermic ( Δ H m 0 < 0, at higher temperatures), whereas micellization is largely entropically driven ( Δ S m 0 > Δ H m 0). [ABSTRACT FROM AUTHOR]