Lyophilization of budesonide-loaded liposomes

Liposomes are nano-scale drug carrier systems with the ability to improve several pharmacokinetic properties of the encapsulated drug. Our goal was to create and lyophilize budesonide-loaded small unilamellar liposomes for inhalation in chronic inflammation-related conditions like asthma or chronic obstructive pulmonary disease (COPD) accompanied by reduced quantity of pulmonary surfactant. The budesonide-loaded liposomes (composed of 3 different phospholipids: 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), and 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) were prepared by thin layer hydration technique and extrusion, then were lyophilized and rehydrated applying dissacharides as cryoprotectants. The freeze-drying method for increasing the shelf-life of the product was optimized regarding the type and ratio of the cryoprotectant sugar as well as the amount of the encapsulated drug. According to the dynamic light scattering measurements, application of trehalose in high ratio (sugar to lipid mass ratio of 15:1) is optimal to avoid aggregation of the small vesicles. Transmission electron microscopy combined with freeze-fracture confirmed the mostly unilamellar liposome structure after rehydration and sterile filtration. Next to the shelf-life measurements, the drug location inside the liposome was investigated: both Fourier-transform infrared spectroscopy and molecular dynamic simulation revealed localization of budesonide at the polar-apolar interface region of the phospholipid bilayer. In summary, these liposomes can be stored long term in freeze-dried from, and their inhalation after rehydration and sterile filtration could provide a dual effect in an asthma or COPD therapy: inflammation inhibition with high efficacy due to the nanoformulation of budesonide while compensating the decreased lipid level of the surfactant by the high DPPC content. • Budesonide-loaded liposomes were prepared, lyophilized and successfully recovered. • Type and amount of cryoprotective disaccharides were optimized. • Mostly unilamellar liposome were gained after rehydration and sterile filtration. • Budesonide is localized at the polar-apolar interface of the lipid bilayer.