Amorphicity and Aerosolization of Soluplus-Based Inhalable Spray Dried Powders

Soluplus is a polymer that has been explored to prepare nanocomposites for pulmonary drug delivery and is non-toxic. However, its aerosolization attributes when spray-dried have not been investigated. Hence, this work aimed to investigate the aerosol performance of soluplus-based spray-dried powders. In addition, the potential use of leucine to improve the aerosolization of such particles was also investigated by including leucine at 10 or 20% w/w. 4% w/w salbutamol was used as a model drug in all the formulations primarily to aid quantification during aerosolization evaluation and for assessing the interaction between the drug and soluplus using infrared spectroscopy with the multivariate analysis approach of principal component analysis (PCA). Three formulations (4% salbutamol/96% soluplus, 4% salbutamol/86% soluplus/10% leucine, 4% salbutamol/76% soluplus/20% leucine) were prepared. The formulations were characterized in terms of solid-state, water content, particle size/morphology, and aerosolization. Similarly, two additional formulations (14% salbutamol/86% soluplus and 24% salbutamol/76% soluplus) were prepared to assess potential non-covalent interactions between salbutamol and soluplus. The formulations with only salbutamol and soluplus were amorphous, as evident from X-ray diffraction. Leucine was crystalline in the formulations. All the spray-dried formulations were irregular spheres with surface corrugation. The 96% soluplus powder showed an emitted fraction (EF) and fine particles fraction (FPF) of 91.9 and 49.8%, respectively. The inclusion of leucine at 10% did not increase the EF; however, an increase in FPF (69.7%) was achieved with 20% leucine. PCA of the infrared spectra suggested potential non-covalent interactions between salbutamol and soluplus. It hinted at the potential involvement of ketone groups of the excipient. This study concludes that soluplus-based spray-dried powder with or without leucine can potentially be utilized for pulmonary drug delivery. In addition, PCA can effectively be utilized in assessing interactions and overcoming limitations associated with visual assessment of the spectra of such formulations.