Incorporation, release and in-vitro antibacterial activity of liposomal aminoglycosides against Pseudomonas aeruginosa

Abstract

Amikacin, netilmicin and tobramycin were incorporated into either anionic or cationic liposomes prepared by sonication. The influence of lipid constituents (charges) on encapsulation efficiency was determined after lysis of vesicles by 0.2% (v/v) Triton X-100. The in-vitro activities of the liposomal aminoglycosides were evaluated against Pseudomonas aeruginosa by agar dilution and compared with free antibiotics. Normal human pooled sera, incubated at 37 degrees C, were supplemented with anionic or cationic liposomes containing known fixed concentrations of amikacin, netilmicin or tobramycin. At various time intervals (0-48 h), samples were taken and antibiotic concentrations determined by the enzyme multiplied immunoassay technique (EMIT). The encapsulation efficiency of cationic liposomes (amikacin 17.1 +/- 1.55%, netilmicin: 5.63 +/- 1.13%, tobramycin 6.7 +/- 0.5%) was approximately 30% higher than that of anionic liposomes (amikacin 12.3 +/- 0.95%, netilmicin 4.0 +/- 0.06%, tobramycin 5.13 +/- 0.18%). Anionic and cationic liposomes in human serum still retained 79.13 +/- 4.04% and 82.71 +/- 2.6% of amikacin, 50.67 +/- 1.8% and 38.6 +/- 0.8% of netilmicin, and 89.09 +/- 1.0% and 88.93 +/- 0.4% of tobramycin, respectively, after 48 h of incubation at 37 degrees C under 5% CO2. The MICs of amikacin (2, 16 and 2 mg/L), netilmicin (2, 1 and 4 mg/L) and tobramycin (1, 2 and 4 mg/L) in free, anionic or cationic liposomal formulations, respectively, were relatively comparable except for anionic liposomal amikacin for which the MIC was increased eight-fold. Empty cationic or anionic liposomes had no effect on bacterial growth. Cationic liposomes containing aminoglycosides should be evaluated further for the treatment of pseudomonal infection.

Antibacterial activity of liposomal gentamicin against Pseudomonas aeruginosa: a time–kill study

“…As reported previously, liposomes containing PBS have no antibacterial activity. Likewise, the combination of empty liposomes with free drug had no additive effect on the antibacterial activity of gentamicin [31].…”

Pharmacokinetics of Cationic Liposome-Encapsulated Doxycycline in Mice Challenged with Genital Infection by <i>Chlamydia trachomatis</i>

“…CaL-DOX was prepared with egg lecithin, stearylamine and cholesterol in a 7:2:1 molar ratio, as described elsewhere [9,10]. Briefly, all three components were dissolved in chloroform and mixed in a round-bottomed flask.…”

“…After sonication and centrifugation, CaL-DOX was resuspended in sterile water. The DOX encapsulation rate was determined by disrupting the lipid membranes with 0.2% of Triton X-100 (Sigma, St. Louis, Mo., USA) using a microbiological assay [10].…”

“…To study the pharmacokinetics of CaL-DOX, after ketamine-xylazine anesthesia, the entire kidneys, liver and half of the genital organs of the mice treated with CaL-DOX or DOX were removed in 1 ml of sterile water; sera were used undiluted. All samples were frozen at -70°C until their microbiological testing [10]. The concentration was determined by comparing the diameter of inhibition to a calibration curve traced with DOX.…”

Determination of Minimum Inhibitory Concentration of Liposomes: A Novel Method

“…al., 2006, Halwani et al, 2007, Institute, 2012 or by agar dilution method (Omri et al, 1995). Liposome suspension loaded with drugs is normally milky in nature.…”