A modelling framework for bulk particles dissolving in turbulent regime

A Systematic Approach in the Development of the Morphologically-Directed Raman Spectroscopy Methodology for Characterizing Nasal Suspension Drug Products

Demonstrating bioequivalence (BE) of nasal suspension sprays is a challenging task. Analytical tools are required to determine the particle size of the active pharmaceutical ingredient (API) and the structure of a relatively complex formulation. This study investigated the utility of the morphologically-directed Raman spectroscopy (MDRS) method to investigate the particle size distribution (PSD) of nasal suspensions. Dissolution was also investigated as an orthogonal technique. Nasal suspension formulations containing different PSD of mometasone furoate monohydrate (MFM) were manufactured. The PSD of the MFM batches was characterized before formulation manufacture using laser diffraction and automated imaging. Upon formulation manufacture, the droplet size, single actuation content, spray pattern, plume geometry, the API dissolution rate, and the API PSD by MDRS were determined. A systematic approach was utilized to develop a robust method for the analysis of the PSD of MFM in Nasonex® and four test formulations containing the MFM API with different particle size specifications. Although the PSD between distinct techniques cannot be directly compared due to inherent differences between these methodologies, the same trend is observed for three out of the four batches. Dissolution analysis confirmed the trend observed by MDRS in terms of PSD. For suspension-based nasal products, MDRS allows the measurement of API PSD which is critical for BE assessment. This approach has been approved for use in lieu of a comparative clinical endpoint BE study [1]. The correlation observed between PSD and dissolution rate extends the use of dissolution as a critical analytical tool demonstrating BE between test and reference products.

Biodegradation model of porous silicon nanoparticles

Development of porous silicon-based drug delivery systems for theranostics requires a precise control of their biodegradation. Thus, we propose a model for the biodegradation of porous silicon nanoparticles (PSi NPs) based on a diffusion equation combined with Nernst-Brunner mass transfer equation describing the dissolution of silicon and formation of silicic acid (SA). The spatiotemporal distributions of PSi NP porosity and SA concentration were calculated. The model was successfully applied to fitting a great variety of experimental data on more than 10 factors influencing the PSi NP biodegradation kinetics, such as the morphology of PSi NPs, surface composition, properties of surrounding media and protective coating layer. Two principal regimes were found out for systems with either diffusion or dissolution dominating over each other. The results of simulations revealed the values of several important parameters, which are hard to be measured experimentally.