Permeability of lipid bilayer to anthracycline derivatives. Role of the bilayer composition and of the temperature.

The uptake of three anthracycline derivatives: doxorubicin, daunorubicin and pirarubicin, into large unilamellar vesicles (LUV) in response to a driving force provided by DNA encapsulated inside the LUV has been investigated as a function of the temperature and of the bilayers lipid composition. The kinetics of the decay of the anthracycline fluorescence in the presence of DNA-containing liposome was used to follow the diffusion of the drug through the membrane. For the three drugs, the permeability coefficient of the neutral form of the drug (P0) decreases as the amount of negatively charged phospholipid in the bilayers increases. This can be explained by the fact that the kinetics of passive diffusion of the drugs depends on the amount of neutral form embedded in the polar head group region, which decreases as the quantity of negatively charged phospholipids increases. P0 also decreases as the amount of cholesterol, that makes the bilayer more rigid, increases. The activation energies, Ea, for the passage of the neutral form of these anthracyclines through the bilayers lie within 100 +/- 15 kJ x ml-1, except for pirarubicin and doxorubicin through anionic phospholipid-rich membranes (Ea = 57 kJ x mol-1) and cholesterol-rich membranes (Ea = 167 kJ x mol-1).