Does ciprofloxacin interact with neutral bilayers? An aspect related to its antimicrobial activity

Ciprofloxacin (CPX) physicochemical properties, mainly hydrophobicity and microspeciation, appear to be related with the ability of this drug to adsorb and diffuse through lipid environments. We have combined the information from fluorescence anisotropy, quenching and epifluorescence of phospholipid monolayers, to explore effects of CPX at the phospholipid-buffer interface. Two fluorescent probes (TMA-DPH and PA-DPH) located at surface level were used for anisotropy experiments. The results evidenced that CPX interact with liposomes at surface level and induce a moderate decrease in the bilayer anisotropy. By using two hydrophobic quenchers (iodobenzene and iododecanoic acid) the presence of CPX in the core of the bilayer was excluded. Mixed monolayers of DPPC and CPX evidenced the ability of CPX to compress the monolayer and the epifluorescence observations showed that CPX modifies lipid distribution and surface phase transition. The surface activity of CPX is reviewed from the physicochemical properties of the drug and in relation to its pharmacological activity.