A facile one-step jet-millingapproach for the preparation of proliposomal dry powder for inhalationaseffective delivery system for anti-TBtherapeutics

Objective: Physicochemical characterization and assessmentof aerosol dispersion performance of anti-TB proliposome dry powders for inhalation (DPIs) prepared using a single-step jet-milling (JM) approach. Significance: Conventional tuberculosis treatment involves isoniazid and rifampicin as first-line agents in extended oral multi-drug regimes. Liposomal DPIs are emerging as promising alternatives for targeted delivery of anti-TB agents to alveolar macrophages harboring Mycobacterium tuberculosis. However, traditional approaches for liposomal DPI preparation are tedious, time consuming and require sophisticated/expensive equipment. The proposed JM technique for preparation of proliposome DPIs could obviate these limitations and facilitate use of these drugs for more effective and safer treatment. Methods: Proliposome DPIs containing isoniazid and/or rifampicin, cholesterol and cholesterol sulfate were successfully prepared via JM (injection pressure, 7.4 bar; milling pressure, 3.68 bar). Their physicochemical, content uniformity, and in vitro aerosol dispersion performance were assessed using scanning electron microscopy/energy-dispersive X-ray spectroscopy, transmission electron microscopy, dynamic light scattering/Zeta potential, X-ray diffraction spectroscopy, thermogravimetric analysis, high performance liquid chromatography, and the Next Generation Impactor. Results: The DPIs exhibited consistent, spherically shaped, smooth particles. Drug particles were evenly distributed with acceptable content uniformity. Drug crystallinity was not significantly affected by milling and the formulations had minimal (<2.0%) water content. After reconstitution of theDPIs, the hydrodynamic size was about 370.9 - 556.2nm and charge was-12.3 - -47.3mV. Furthermore, the proliposome DPIs presented emitted dose (69.04 - 89.03%), fine particle fraction,< 4.4 µm (13.7 - 57.8%), and mass median aerodynamic diameter (<3.0 µm), which satisfied the requirements for deep lung delivery. Conclusion: The proposed approach was suitable for preparation of proliposome DPIs that could be deployed for local targeting of the lower respiratory tract for treatment of tuberculosis.