Biology Reference
In-Depth Information
treatments are improving the lung function of CF patients, reduction in neutrophil
infl ammatory response and bacterial infections may reduce its lysis and the presence
of charged macromolecules which tend to inactivate cationic antibiotics. As novel ap-
proaches proceed towards a cure for CF, research must also be directed on strategies
that obstruct the presence and/or action of inhibitory factors associated with the dis-
ease. Future work in our laboratory will tend to focus on disruption of these negatively
charged factors for increased liposomal penetration.
RESULTS
Liposome Entrapment and Sizing
The entrapment efficiency of tobramycin in liposomes composed of DMPC/Chol (35
mg:10 mg) was 2.47 ± 0.19 mg/ml with a mean size of 293.7 ± 41.1 nm, (polydis-
persity index of 0.70 ± 0.12). Liposomes containing polymyxin B in DPPC/Chol (38
mg:10 mg) had an entrapment efficiency of 0.4 ± 0.02 mg/ml, with a mean size of
445.1 ± 49.3 nm (polydispersity index of 0.91 ± 0.06).
Stability of Liposome-entrapped Antibiotics
Liposomal stability and antibiotic leakage in different environments including CF spu-
tum at 3 or 18 hr post-exposure are shown in Table 1. The release rate of antibiotics in
the presence of bacterial supernatant, polyanionic components, autoclaved, or intact
sputum was comparable to PBS buffer or CAMH broth controls.
Table 1.
Liposome-entrapped antibiotic stability assayed by microbiological assay.
Formulations Conditions Retention at 3 h Retention at 18 h
Liposomal tobramycin PBS buffer
72.7:±:3.2% 71.5:±:2.6%
CAMH broth
74.6:±:2.1% 73.3:±:0.5%
Bacterial Supernatant
72.9:±:1.6% 74.1 :±:2.0%
Polyanionic broth
74.3:±:2.2% 73.3:±:1.8%
Sterile Sputum
72.1 :±:3.0% 71.4:±:1.1%
Intact Sputum
73.8:±: 1.9% 71.7:±: 1.4%
Liposomal polymyxin B PBS buffer
67.5:±: 1.3% 54.9:±: 1.8%
CAMH broth
65.2:±: 1.2% 54.7:±: 1.7%
Bacterial Supernatant
67.5:±:2.1% 54.9:±:2.7%
Polyanionic broth
69.4:±:2.7% 51.3:±: 2.4%
Sterile Sputum
67.2:±:2.6% 53.3:±:2.4%
Intact Sputum
65.4:±: 1.5% 53.3:±:2.4%
The stability of the liposomal formulations were examined at 37°( in an 18 h period in the presence of PBS, CAMH
broth, supernatant of biofi lm forming
P. aeruginosa
, a combination of DNA, F-actin LPS, and LTA and diluted intact
or autoclaved s utum.
Effect of DNA, F-Actin, LPS, and LTA on Bactericidal Activity
To determine the inhibitory effects of DNA, F-actin, LPS, or LTA on the activity of
antibiotics, different concentrations of these inhibitory factors were co-incubated with
