Design of salmon calcitonin particles for nasal delivery using spray-drying and novel supercritical fluid-assisted spray-drying processes

The overall aim of this study was to prepare a nasal powder formulation of salmon calcitonin (sCT) using an absorption enhancer to improve its bioavailability. In this work, powder formulations for nasal delivery of sCT were studied using various absorption enhancers and stabilizers. Powders were prepared by two different methods: conventional spray-drying (SD) and novel supercritical fluid-assisted spray-drying (SASD) to investigate the role of CO₂ in the particle formation process. The prepared sCT powder formulations were characterized by several analyses; powder X-ray diffractometry (PXRD), scanning electron microscopy (SEM), and the Fourier transform infrared (FT-IR) spectroscopy method. The particle size distribution was also evaluated. In vivo absorption tests were carried out in Sprague-Dawley rat using the prepared powder formulations, and the results were compared to those of raw sCT. Quantitative analysis by high-performance liquid chromatography (HPLC) indicated that sCT was chemically stable after both the SD and SASD processes. Results of PXRD, SEM, and FT-IR did not indicate a strong interaction or defragmentation of sCT. The in vivo absorption test showed that SD- and SASD-processed sCT powders increased the bioavailability of the drug when compared to the nasal administration of raw sCT. In addition, SASD-processed sCT exhibited higher nasal absorption when compared with SD-processed sCT in all formulations due to a reduction of particle size. The results from this study illustrate that the preparation of nasal powders using the SASD process could be a promising approach to improve nasal absorption of sCT.