Enhancing Antituberculosis Treatment Nanoparticles Encapsulated with Catalase and Levofloxacin Under Ultrasound Stimulation: A 3D Spheroid Study

Tuberculosis (TB) is a chronic infectious disease caused by Mycobacterium tuberculosis (MTB). Tuberculous granuloma is the central and key pathological structure of tuberculosis and is characterized by tissue hypoxia and ineffective drug delivery. To address these issues, this study fabricated a composite nanoparticle loaded with catalase (CAT) and levofloxacin (LEV) (CAT@LEV-NPs) and then combined it with ultrasound (US) to investigate the bactericidal effect and underlying mechanisms using TB spheroids. The TB spheroids were constructed using attenuated Bacillus Calmette-Guérin (BCG) instead of MTB to facilitate operation under general experimental conditions. This study examined the physical properties and oxygen production efficiency of CAT@LEV-NPs. Subsequently, we treated TB spheroids with nanoparticles alone or in combination with US and found that ultrasound significantly increased drug permeability and activated CAT@LEV-NPs to produce a large number of reactive oxygen species (ROS). The combined treatment showed excellent antibacterial effects, resulting in more severe damage to the bacterial structure than other treatments. Additionally, the combined treatment induced a higher M1 polarization of macrophages, increased the apoptosis rate, and improved the anoxic microenvironment in TB spheroids. These factors may be closely related to the enhanced bactericidal effects of combined treatment. In conclusion, our study suggests that US combined with CAT@LEV-NPs could serve as a novel, noninvasive, safe, and effective treatment modality for intractable MTB infections.