Phospholipid dry powders produced by spray drying processing: structural, thermodynamic and physical properties

Phospholipid particles for pharmaceutical applications were prepared by spray-drying processing and characterized for their structural, thermodynamic and physical properties. The lipid particles were spherical and potentially suitable for pulmonary applications (aerodynamic diameter less than 5 mum), for tablet preparations of orally administered drugs or as proliposomes in liquid formulations. The operational conditions, such as nozzle diameter, lipid concentration, flow rate and temperature of the feed solution, as well as the concentration of mannitol, the core material, were found to affect the particle properties, thus allowing them to be modified through the processing conditions. When mannitol was incorporated into formulations containing 20 or 45 mM lipid, at a feed flow rate of 3 ml/min, the resulting structures were more amorphous. More crystalline structures were obtained when the feed solution temperature and the nozzle diameter were increased from 25 to 60 degreesC and from 0.5 to I mm, respectively. The physical and chemical stability of the particles was preserved when they were stored under refrigeration, as shown by the water activity measurements and differential scanning calorimetry (DSC). These results show the potential of spray-dried particles for drug delivery applications. (C) 2004 Elsevier B.V. All rights reserved.