Pulmonary delivery of excipient-free tobramycin DPIs for the treatment of Pseudomonas aeruginosa lung infection with CF

<i>Pseudomonas aeruginosa</i> infection has become a widespread problem in patients with cystic fibrosis (CF). A safe and effective manufacturing method is required to produce antibiotic dry powder inhalations (DPIs) which can be effectively delivered to treat lung infections. In this study, an excipient-free tobramycin inhalable powder was prepared using spray freeze-drying (SFD) method. The mass median aerodynamic diameters (MMAD) of optimized inhalable powder prepared by SFD was 1.30 µm, and the fine particle fractions (FPF) reached 83.31%. In both <i>in vitro</i> and <i>in vivo</i> safety and activity studies, the inhalable powder showed excellent safety performance at both animal and cellular levels, with a minimum inhibitory concentration (MIC) of 0.5 μg/mL. Compared with intravenous injection, inhalation of excipient-free tobramycin inhalable powder had a better effect in the infected mouse model because of its amorphous state. This study demonstrates that excipient-free tobramycin inhalable powder with good delivery and deposition performance can be successfully obtained using the SFD method. Inhalation of excipient-free tobramycin inhalable powder has the potential to be a promising strategy for treating pulmonary infections caused by <i>P. aeruginosa</i> in patients with CF.