Structure and release behavior of PMMA/silica composite drug delivery system

The preparation, characterization, and in vitro release of aspirin from polymethylmethacrylate (PMMA)/silica composites prepared via a sol-gel route are reported. The in vitro drug release test revealed that the release rate of aspirin in PBS increased with the silica content in the composites; on the contrary, the increase of the content of 3-(trimethoxysilyl) propyl methacrylate (MSMA), a coupling agent, decreased the drug release rate. The drug release rate/composite structure relationship was studied using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and swelling ratio (SR) measurement. The results indicated that the interface between polymer matrix and inorganic fillers has significant influence on the drug release behavior of the composite materials. In addition, models of mass transfer based on Fickian diffusion law at constant temperature and pressure were employed to analyze the results of the in vitro drug release experiments. The drug release behaviors of the composite samples fitted well with the Fickian diffusion model. The values of k, which is in direct proportion to drug release rate, increased with the increasing content of silica while decreased with that of MSMA in the composite samples.