Comparative study of silica nanoparticles and surface modified silica nanoparticles: Drug adsorption process and controlled release behavior

The purpose of this study was to compare drug adsorption process and release behavior of commercial silica nanoparticles (Silica-01) and surface modified silica nanoparticles (Silica-03). Characteristics of Silica-01 and Silica-03, including specific surface area, pore size and morphology were given initially. Characteristics of diltiazem hydrochloride (DZH) loaded Silica-01 and indomethacin (IMC) loaded Silica-03 were described by differential scanning calorimeter (DSC), fourier transform infrared spectroscopy (FT-IR) and in vitro dissolution. It can be observed from scanning electron microscope (SEM) that Silica-03 was coated and possessed better dispersibility. Drug adsorption process revealed the competition between drug and solvent, and main influencing factors are polarity of solvent. FTIR indicated that DZH was adsorbed onto Silica-01 and IMC was adsorbed onto Silica-03 with hydrogen bond. Silica-01 and Silica-03 controlled drug release with a burst release and a sustained release, and Silica-03 could slow down burst release due to steric hinder caused by surface modification.