Interactions Of Ciprofloxacin With Dppc And Dppg: Fluorescence Anisotropy, Atr-Ftir And P-31 Nmr Spectroscopies And Conformational Analysis

The interactions between a drug and lipids may be critical for the
pharmacological activity. We previously showed that the ability of a
fluoroquinolone antibiotic, ciprofloxacin, to induce disorder and modify the
orientation of the acyl chains is related to its propensity to be expelled from a
monolayer upon compression [1]. Here, we compared the binding of ciprofloxacin on
DPPC and DPPG liposomes (or mixtures of phospholipids [DOPC:DPPC], and
[DOPC:DPPG]) using quasi-elastic light scattering and steady-state fluorescence
anisotropy. We also investigated ciprofloxacin effects on the transition
temperature (T(m)) of lipids and on the mobility of phosphate head groups using
Attenuated Total Reflection Fourier Transform Infrared-Red Spectroscopy
(ATR-FTIR) and (31)P Nuclear Magnetic Resonance (NMR) respectively. In the
presence of ciprofloxacin we observed a dose-dependent increase of the size of
the DPPG liposomes whereas no effect was evidenced for DPPC liposomes. The
binding constants K(app) were in the order of 10(5) M(-1) and the affinity
appeared dependent on the negative charge of liposomes: DPPG>DOPC:DPPG (1:1;
M:M)>DPPC>DOPC:DPPC (1:1; M:M). As compared to the control samples, the chemical
shift anisotropy (Deltasigma) values determined by (31)P NMR showed an increase
of 5 and 9 ppm for DPPC:CIP (1:1; M:M) and DPPG:CIP (1:1; M:M) respectively.
ATR-FTIR experiments showed that ciprofloxacin had no effect on the T(m) of DPPC
but increased the order of the acyl chains both below and above this temperature.
In contrast, with DPPG, ciprofloxacin induced a marked broadening effect on the
transition with a decrease of the acyl chain order below its T(m) and an increase
above this temperature. Altogether with the results from the conformational
analysis, these data demonstrated that the interactions of ciprofloxacin with
lipids depend markedly on the nature of their phosphate head groups and that
ciprofloxacin interacts preferentially with anionic lipid compounds, like
phosphatidylglycerol, present at a high content in these membranes.