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ABSTRACT: Pulmonary delivery of sustained release formulations needs
drug encapsulation in a suitable matrix, as well as the generation
of aerosols with high lung penetration and suitable release
characteristics. Nanometer sized liposomes offer the potential for
biocompatibility, controlled release and easy internalization in the
lung. For uniform dose delivery and drug release kinetics, it is
of interest to understand generation techniques to obtain aerosols
containing nearly monodispered nanometer sized dry particles.
Two aerosolization techniques, air-jet atomization and electrohydrodynamic
atomization (EHDA) were studied to identify conditions
under which the inclusion of one-liposome-per-drop could
be achieved. In air-jet atomization, low lipid concentrations resulted
in a unimodal aerosol with a median mobility diameter of
94 (±3.5) nm, while higher concentrations led to larger median
diameters, implying possible inclusion of multiple liposomes per
drop. In EHDA, tuning drop sizes in the range of 130 to 200 nm, as
well as the use of high lipid concentrations, resulted in a bimodal
aerosol distribution, with peaks at 35 and 100 nm mobility diameters.
TEM images of the liposome aerosol from EDHA showed
fused liposomes, resulting in cylindrical structures with different
physical diameters. It was hypothesized that deformation of liposomes
to cylindrical structures in the micro-capillary liquid tip of
the electrospray, and interactions along the axial or cross sectional
surfaces led to dry particles with different mobility sizes.
Aerosol Science and Technology. 01/2010; 44:972 — 982.