In-vitro cytotoxicity, synergistic antibacterial activity and interaction studies of imidazolium-based ionic liquids with levofloxacin

Nowadays, the third generation of ionic liquids (ILs) emerged as a new active pharmaceutical ingredient (API) as they possess biological activity. These active pharmaceutical ingredients in combination with available antimicrobials may enhance their selectivity and activity. Therefore, the screening and development of these API are very important for pharmaceutical industries. Thus, herein, the efforts have been made to study the synergistic interaction between antibacterial drug levofloxacin (LVF) and imidazolium-based ILs such as 1-butyl-3-methylimidazolium chloride (C4mimCl) and 1-decyl-3-methylimidazolium chloride (C10mimCl). The in-vitro cytotoxicity of ILs was done using MTT assay on HEK293 (Human embryonic kidney cells). The antibacterial activities of these imidazolium based ILs have been evaluated against E. coli and S. aureus strain. Further, the effect of these ILs on the antibacterial property of LVF was checked by preparing various combinations of ILs with LVF. The results showed the remarkable enhancement in the antibacterial activity of LVF with ILs, however, the effect is more prominent with higher alkyl chain length IL.The critical micellar concentration (cmc), of ILs and ILs with LVF were also measured which further utilized to evaluate Gibss free energy of adsorption (∆Gad). The value of ∆Gad, further showed that IL with a larger alkyl chain has greater efficiency towards the antibacterial activity. The other surface-active and thermodynamic parameters like maximum excess concentration (Γmax) minimum area per molecules (Amin), Gibbs free energy change of micellization (ΔGm), enthalpy change of micellization (ΔHm), entropy change of micellization (ΔSm), and Gibbs excess energy (Gsmin) for pure ILs and ILs + LVF mixtures were also determined.