Evidence of Segregation of a Quinolone Antibiotic in Dipalmitoylphosphatidylcholine Environment

Abstract

Biophysical techniques as Photon correlation spectroscopy (PCS), Diferential Scaning Calorimetry (DSC) and Epifluorescence and monolayer studies, were used to explore the interaction between the quinolone, 1-cyclopropyl-6-fluoro-l,4-dihydro-4-oxo-7-(N-3-methyl-piperazinyl)-3-quinoline carboxilic acid (CNV8912) and dipalmitoylphosphatidyl-choline (DPPC). CNV8912 caused a reduction in the size and polydispersity of the liposomes, and a reduction in the rate of change in these parameters near the usual pretransition temperature of DPPC. DSC showed that the quinolone could be incorporated initially in relatively large amounts into the DPPC bilayers, but repetitive cycling through the gel to liquid crystal phase transition led to a substantial exclusion of CNV8912 into separate domains. CNV8912 caused expansion of monolayers of DPPC, although CNV8912 alone did not spread well at the air-water interface. CNV8912 in monolayers of DPPC caused the production of more, smaller, condensed domains when the film were3 compressed through the liquid expanded-liquid condensed transition into the condensed form than were seen when monolayers of the pure lipid were similarly c ompresed. These observations are pertinent to potential interactions of quinolones with membranes and their eventual encapsulation in liposomes and reinforce the hypothesis about the existence of a hidrophobic via of uptake by bacteria.