Aerosolizable Plasmid DNA Dry Powders Engineered by Thin-film Freezing

A Review on Micro and Nanoengineering in Powder-Based Pulmonary Drug Delivery

Pulmonary delivery of drugs has emerged as a promising approach for the treatment of both lung and systemic diseases. Compared to other drug delivery routes, inhalation offers numerous advantages including high targeting, fewer side effects, and a huge surface area for drug absorption. However, the deposition of drugs in the lungs can be limited by lung defence mechanisms such as mucociliary and macrophages' clearance. Among the delivery devices, dry powder inhalers represent the optimal choice due to their stability, ease of use, and absence of propellants. In the last decades, several bottom-up techniques have emerged over traditional milling to produce inhalable powders. Among these techniques, the most employed ones are spray drying, supercritical fluid technology, spray freeze-drying, and thin film freezing. Inhalable dry powders can be constituted by micronized drugs attached to a coarse carrier (e.g., lactose) or drugs embedded into a micro- or nanoparticle. Particulate-based formulations are commonly composed of polymeric micro- and nanoparticles, liposomes, solid lipid nanoparticles, dendrimers, nanocrystals, extracellular vesicles, and inorganic nanoparticles. Moreover, engineered formulations including large porous particles, swellable microparticles, nano-in-microparticles, and effervescent nanoparticles have been developed. Particle engineering has also a crucial role in tuning the physical-chemical properties of both carrier-based and carrier-free inhalable powders. This approach can increase powder flowability, deposition, and targeting by customising particle surface features.

Inhaled dry powder liposomal azithromycin for treatment of chronic lower respiratory tract infection

A dry powder inhaled liposomal azithromycin formulation was developed for the treatment of chronic respiratory diseases such as cystic fibrosis and bronchiectasis. Key properties including liposome size, charge and encapsulation efficiency powder size, shape, glass transition temperature (Tg), water content and in vitro respiratory deposition were determined. Antimicrobial activity against cystic fibrosis (CF) respiratory pathogens was determined by MIC, MBC and biofilm assays. Cytotoxicity and cellular uptake studies were performed using A549 cells. The average liposome size was 105 nm, charge was 55 mV and encapsulation efficiency was 75 %. The mean powder particle size d[v,50] of 4.54 µm and Mass Median Aerodynamic Diameter (MMAD) was 5.23 µm with a mean Tg of 76˚C and water content of 2.1 %. These excellent physicochemical characteristics were maintained over one year. Liposomal loaded azithromycin demonstrated enhanced activity against P. aeruginosa clinical isolates grown in biofilm. The formulation was rapidly delivered into bacterial cells with > 75 % uptake in 1 h. Rapid uptake into A549 cells via a cholesterol-dependent endocytosis pathway with no cytotoxic effects apparent. These data demonstrate that this formulation could offer benefits over current treatment regimens for people with chronic respiratory infection.

Viability of Lactobacillus acidophilus in Thin-Film Freeze-Dried Powders Filled in Delayed-Release Vegetarian Capsules in a Simulated Gastric Fluid

Previously, we have shown that thin-film freeze-drying can be applied to prepare dry powders of bacteria such as Lactobacillus acidophilus. Herein, we tested the viability of L. acidophilus in thin-film freeze-dried powders (TFF powders) filled in delayed-release vegetarian capsules in a simulated gastric fluid (SGF) consisting of 0.1N hydrochloric acid and sodium chloride. Initially, we determined the water removal rate from frozen thin films on relatively larger scales (i.e., 10-750 g). We then prepared and characterized two TFF powders of L. acidophilus with either sucrose and maltodextrin or sucrose and hydroxypropyl methylcellulose acetate succinate (HPMC-AS), a pH-sensitive polymer, as excipients and evaluated the viability of the bacteria after the TFF powders were filled in delayed-release vegetarian capsules and the capsules were incubated in the SGF for 30 min. On 10-750 g scales and at the settings specified, water removal from frozen thin films was faster than from slow shelf-frozen bulk solids. When the L. acidophilus in sucrose and HPMC-AS TFF powder was filled into a delayed-release capsule that was placed into another delayed-release capsule, the bacterial viability reduction after incubation in the SGF can be minimized to within 1 log in colony forming unit (CFU). However, for the L. acidophilus in sucrose and maltodextrin TFF powder, even in the capsule-in-capsule dosage form, bacterial CFU reduction was > 2 logs. TFF powders of live microorganisms containing an acid-resistant material in capsule-in-capsule delayed-release vegetarian capsules have the potential for oral delivery of those microorganisms.