An oral controlled release system has been developed to improve the delivery of drugs to the systemic circulation. The aim of this investigation was to synthesize and formulate controlled release matrix tablet using pH sensitive poly (methacrylic acid)-graft-karaya gum (p(MAA)-g-KG) as a graft copolymer. The pH-sensitive p(MAA)-g-KG copolymer was synthesized by free radical polymerization using cerric ammonium nitrate (CAN) as initiator and methylene bisacrylamide (MBA) as a crosslinker under nitrogen atmosphere. Grafting parameter such as grafting ratio, efficiency, add on and conversion were identified with respect to change in concentration of CAN (0.01-0.15 mol dm-3) and methacrylic acid concentration (0.05–0.15 mol dm-3). The grafting was confirmed by Fourier transform infrared spectroscopy. Differential scanning calorimetry and X-ray diffraction studies were carried out to know the internal characteristics of polymeric material. Scanning electron microscopic analyses shows the change in surface morphology of the graft copolymer. The swelling studies illustrate that there is less swelling property of graft copolymer as compared to karaya gum (KG). Tablets were formulated with different concentration of graft copolymer and other excipients by incorporating diclofenac sodium (DS) as a model drug. In vitro drug release studies were performed in pH 1.2 for 2 hours followed by pH 6.8 without enzyme at 37°C. The release time increased with increasing grafting ratio in matrix tablet which indicates the swelling behavior of graft copolymer to release drug in dissolution medium. The release rates were fitted to an empirical equation to calculate the diffusional exponent (n), which indicate Super Case II transport mechanism for controlled release of diclofenac sodium.
