Effect of liposome composition on erythomycin encapsulation and in vitro antibacterial activity

Some erythromycin-containing multilamellar liposomal formulations were prepared and characterized, with a particular regard to the effects of the presence of charged lipids (stearylamine or DPPS) and of a surfactant, Tween 80 at a 0.1 or 0.2% concentration, upon vesicle physico-chemical properties, as drug encapsulation and leakage rate. The prepared formulations were submitted to an in vitro microbiological screening, to test the effects of liposomal incorporation on erythromycin antibacterial activity, against different Gram + strains. After encapsulation into neutral and positive MLVs, the drug retains its activity, even if no relevant MIC reduction was observed; DPPC/CHOL vesicles showed the best activity. The addition of the surfactant in liposome matrix in some eases resulted in an increase of erythromycin activity. When erythromycin was carried in negatively-charged liposomes, a fall of activity was instead observed.