Delivery of liposomes in dry powder form: Aerodynamic dispersion properties

Objective: In our previous study, we reported a novel approach of delivering liposomes in dry powder form that relies on spontaneous formation of liposomes upon dispersion of micronised phospholipid(s) based powders in an aqueous environment, thereby creating reservoirs for the encapsulation of drugs [J. Pharm. Sci. 91 (2002) 482]. In this paper, we demonstrate the in vitro generation of aerosols from these novel powders. Methodology: Various formulations comprising different phospholipid(s) exhibiting different physico-chemical properties were prepared. Aerosol was generated using a deagglomeration rig wherein the powder was entrained at a flow rate of 60l/min and high turbulence was generated using air-jets. Two antimicrobial agents (ciprofloxacin and CM3, a novel peptide) and a bronchodilator, salbutamol sulfate, were used as model drugs to examine the powder dispersion properties. Results: The deagglomeration rig used in this study was able to disperse 87-95% of the total loaded powder into the cascade impactor. Amongst the various formulations comprising different phospholipid(s), DMPG and (DMPC+DMPG) based formulations exhibited excellent aerodynamic dispersion properties. Fine particle fractions (FPF) of more than 50% were achieved for these formulations for three model drugs. Encapsulation of the model drugs in the FPF, obtained upon dispersion of these novel powders, is also discussed in this paper. An encapsulation of approximately 35, 40 and 25% was achieved in the FPF for ciprofloxacin, CM3 peptide and salbutamol sulfate, respectively.