Effect of salts and temperature on the interaction of levofloxacin hemihydrate drug with cetyltrimethylammonium bromide: Conductometric and molecular dynamics investigations

Abstract

Investigation of the interaction of the beta-lactum antibiotic drug levofloxacin hemihydrate (LFH) with cetyltrimethylammonium bromide (CTAB) has been performed in aqueous solution and in the attendance of salts at various temperatures (298.15, 303.15, 308.15, 313.15 and 318.15K). A single critical micelle concentration (CMC) was observed for pure CTAB and their mixture with the drug (LFH). The CMC values for mixed systems (LFH+CTAB) in the presence of salt showed lower in magnitude in comparison to their absence. This pointed out the early micellization of the mixture of LFH and CTAB. All the ∆G0m values were found to be negative for all systems. The ∆H0m and ∆S0m values showed that hydrophobic and electrostatic interactions were boosted in the presence of salts compared to their absence at lower and higher temperatures respectively. The other thermodynamic parameters such as transfer energy (∆G0m.tr.), transfer enthalpy (ΔH0m.tr.) as well as transfer entropy (∆S0m.tr.) were also determined and discussed in detail. The intrinsic enthalpy gain (∆H0,⁎m) and the compensation temperature (Tc) were also evaluated and discussed. Molecular dynamics simulation reveals that aqueous as well as salt environment have impact on the hydrophobic interaction between LFH and surfactant.