Optimizing Chitosan-based Posaconazole Dry Powder Formulation Using Box-Behnken Design: The Role of Leucine in Enhancing Performance

Introduction: The objective of this study was to develop and optimize a dry powder inha-lation formulation of Posaconazole-loaded Chitosan Nanoparticles (POS-CSNPs) using a Quality by Design (QbD) approach. The aim was to enhance pulmonary drug delivery and antifungal efficacy, particularly against Rhizopus oryzae, by improving drug encapsulation, particle dispersion, and lung deposition using leucine as a performance enhancer. Methods: A Box-Behnken Design (BBD) was employed to evaluate the effects of Chitosan-to-Tripolyphosphate (CS:TPP) ratio, stirring speed, and polymer concentration on particle size, Poly-dispersity Index (PDI), and Entrapment Efficiency (EE). Nanoparticles were prepared via ionic gela-tion and spray-dried with varying concentrations of lactose and leucine. Characterization techniques included FTIR for drug-excipient compatibility, Dynamic Light Scattering (DLS) for size and zeta potential, TEM for morphology, and XRD for crystallinity. In vitro drug release, pulmonary deposi-tion using a twin-stage impinger, antifungal activity, and stability under ICH conditions were as-sessed. Results: The optimized formulation had a particle size of 248.20 ± 6.82 nm, PDI of 0.225 ± 0.010, zeta potential of 21.92 ± 0.84 mV, and EE of 68.17 ± 1.73%. In vitro release showed sustained drug delivery over 48 hours. The Fine Particle Fraction (FPF) reached 68.9% in leucine-based formula-tions, and antifungal activity was significantly higher compared to the pure drug, with a zone of inhibition of 21 ± 0.5 mm. Discussion: The results demonstrated improved particle characteristics, drug release, and antifungal efficacy. Leucine significantly enhanced dispersibility and deposition. However, scale-up and batch consistency remain challenges. Further in vivo studies are needed to confirm clinical applicability. Conclusion: The study successfully developed a stable, effective dry powder POS-CSNP formulation with enhanced pulmonary delivery and antifungal activity, offering potential for improved treatment of pulmonary fungal infections.