The effect of L-leucine on the stabilization and inhalability of spray-dried solid lipid nanoparticles for pulmonary drug delivery

The aim of this study was to investigate the effects of leucine on the stabilization and aerodynamic characteristics of spray-dried solid lipid nanoparticles (SLN). The stabilizing effects were evaluated in terms of the ability to inhibit particle growth, and to maintain the thermodynamic integrity and drug release characteristics of reconstituted SLN. The results showed that spray-drying drastically changed particle size of reconstituted SLN, whereas the presence of different excipients led to different extent of stabilization. Leucine appeared to be more effective in the stabilization of SLN than trehalose, sucrose, lactose and mannitol, with the former conferring the ability to maintain the particle size of spray-dried and reconstituted SLN being almost the same as that before spray drying. When the content of leucine was added to 40% w/w or higher, the fine particle fractions of spray-dried powders dispersed through a Cyclohaler were about 48%. The overall results demonstrated that the presence of leucine facilitated the stabilization of SLN during spray-drying, and improved the aerosolization properties of the spray-dried SLN for pulmonary delivery.