6-FLUOROQUINOLONE-LIPOSOME INTERACTIONS - FLUORESCENCE QUENCHING STUDY USING IODIDE

Two models (octanol:buffer and lipid:buffer) were used to estimate the interaction of ciprofloxacin and two alkyl derivatives with neutral m embranes. To investigate the existence of a mechanism of permeation th rough the lipid bilayers quenching methods of fluorescence were applie d to ciprofloxacin liposomes in order to discriminate relative membran e location of ciprofloxacin. Different mechanisms of quenching appear depending on conditions (pH 4.80, 7.40 and 9.10) which were interprete d under the basis of 6-fluoroquinolone microspeciation and the ability of only the neutral microspecies to permeate across apolar environmen ts. No major effects of temperature (below and above transition temper ature, T-m) on quenching mechanism were observed. The high accessibili ty for iodide shown by ciprofloxacin and its methyl and ethyl derivati ves together with the low drug/phospholipid ratio indicate a fast rele ase of the drug from liposomes. Previously the quenching effect of iod ide on ciprofloxacin and its inability to access the apolar hydrophobi c regions of the bilayers were studied. (C) 1998 Elsevier Science B.V. All rights reserved.