Preparation of microcapsules with the evaluation of physicochemical properties and molecular interaction

The objective of this study was to prepare and characterize dutasteride (a hydrophobic model drug) microcapsules using ethyl cellulose as a capsule shell polymer with different drug/polymer ratios of 1:1, 1:3, and 1:5. The microcapsules were prepared by a solvent evaporation method and the prepared microcapsules were evaluated for percent yield, percent drug content, encapsulation efficiency, particle size distribution, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), Fourier transform infrared (FT-IR) spectroscopy, powder X-ray diffraction (PXRD), and in vitro drug release studies. SEM revealed the spherical shape of all prepared microcapsules. The particle size of the microcapsules was about 95-119 μm with good yield and encapsulation efficiency. PXRD showed different X-ray patterns compared to the drug itself suggesting possibility of crystalline form change during the process. Moreover, it confirmed that ethyl cellulose was changed to amorphous state. The physical property changes may affect the overall quality and drug release behavior. In the FT-IR studies, hydrogen bonding was observed between the drug and polymer at the molecular level. DSC data provided consistent results with the FT-IR and PXRD analyses. Drug release profiles showed the overall sustained release of drug and anomalous diffusion mechanism based on the Korsmeyer-Peppas equation. Understanding the physicochemical properties of a drug and polymer including molecular interactions may facilitate formulation of microcapsules with acceptable properties and drug release behaviors.