Development and evaluation of novel liposomal formulations of antibiotics

The main objective of this thesis was to develop and characterize liposomal antibiotics in an effort to improve antibacterial activities of encapsulated drugs against resistant strains of P. aeruginosa isolated from CF patients.; We have developed a modified dehydration/rehydration (DRV) technique to produce small but stable vesicles with high yield drug entrapment. Encapsulation of aminoglycoside and macrolide antibiotics into these liposomes significantly increased the antibacterial activity of these agents against strains of P. aeruginosa. Furthermore, liposomal antibiotics were significantly more effective in killing bacteria than the corresponding free drugs even at lower concentrations. We investigated the mechanism of enhanced activity of liposomal antibiotics as well. Electron microscopy indicated bacterial membrane deformation and fusion with liposomes. The fusion of liposomes with bacterial membrane was further confirmed by flow cytometry and lipid mixing assays. The degree of fusion between liposomes and bacterial membranes increased as a function of incubation time until a maximum fusion rate was reached. The fusion between liposomes and P. aeruginosa resulted in significantly increased amount of antibiotic penetration inside the bacterial cells as demonstrated by immunocytochemistry studies.; In conclusion, the modified DRV technique developed may be utilized to overcome the low encapsulation efficiency associated with aminoglycoside and macrolide antibiotics. Furthermore, the fusion between the liposomes and the bacterial membranes facilitates antibiotics access inside the bacterial cells. Hence, liposome-entrapped antibiotics could overcome the drug resistance phenomenon associated with bacterial outer-membrane permeability. (Abstract shortened by UMI.)...