Ambient pressure drug loading on trimethylchlorosilane silylated silica aerogel in aspirin controlled-release system

Abstract

Trimethylchlorosilane silylated silica aerogel (TS-SA) was loaded with a model drug, aspirin. TS-SA preparation, drug loading, and drying were performed through ambient pressure techniques in a safe and cheap manner. The sample structure, drug loading, and drug dissolution profiles were characterized by N2 adsorption and desorption analysis, FT-IR spectroscopy, UV absorption spectroscopy, FE-EM, EDX, XRD, and DSC. The characterization results indicated drug molecules are successfully loaded on the entire nanostructure of TS-SA. Specific surface area, total pore volume, and average pore size decrease with drug loading in TS-SA structure, as well as XRD and DSC results are indicating the amorphous state of loaded aspirin. Drug adsorption isotherm was measured and fitted well by the Freundlich model. Drug release kinetics from the samples were also evaluated in 0.1 N HCl (pH 1.2) and phosphate buffer (pH 7.4). The zero-order model, the first-order model, and the Higuchi model were employed to study the release kinetics. Better fitting to the Higuchi model showed that Fick's diffusion governs the aspirin release mechanism. The release rate of loaded samples was slower than the pure drug in both HCl and phosphate buffer. As pure aspirin dissolves totally in 0.1 N HCl and phosphate buffer within 40 min and 20 min, respectively, loaded drug dissolve 35% ± 4 and 80% ± 4 in 0.1 N HCl and phosphate buffer within 100 min. The ambient pressure drug loading on TS-SA could have interesting potential applications in controlled release drug delivery systems.