Novel semi-IPN based on crosslinked carboxymethyl starch and clay for the in vitro release of theophylline

A novel semi-interpenetrating polymer network (IPN) based on crosslinked carboxymethyl starch (CL-CMS) and montmorillonite (MMT) was prepared, where carboxymethylation occurs as a result of the reaction between native starch and monochloroacetic acid in isopropanol/water medium at 60 °C. The carboxymethyl starch is further crosslinked and made into a semi-IPN with MMT for the release of theophylline. The drug carrier was characterized using FTIR, XRD and surface analysis using SEM. Studies including physio-chemical analysis, swelling behavior, encapsulation efficiency, effect of MMT content, effect of ionic strength and in vitro drug release were carried out. Theophylline encapsulation of up to 74% was achieved and drug release was monitored in SGF (pH 1.2) and SIF (pH 7.4). Results show that the matrix releases drug at a much faster rate in the basic medium than in the acidic medium, thereby holding the promise of developing the semi-IPN system as a potential candidate for the release of theophylline.