Evaluation of pH-sensitivity and drug release characteristics of (polyacrylamide-grafted-xanthan)-carboxymethyl cellulose-based pH-sensitive interpenetrating network hydrogel beads

Novel pH-sensitive interpenetrating network hydrogel beads of polyacrylamide-grafted-xanthan (PAAm-g-XG) and sodium carboxymethyl cellulose (NaCMC) loaded with ketoprofen were prepared and evaluated for pH sensitivity and drug release characteristics. The pH-sensitive PAAm-g-XG copolymer was synthesized by free radical polymerization under the nitrogen atmosphere followed by alkaline hydrolysis. The grafting and alkaline hydrolysis reactions were confirmed by Fourier transform infrared spectroscopy. Differential scanning calorimetry and X-ray diffraction studies were carried out to know the crystalline nature of encapsulated drug. Scanning electron microscopic study revealed that the interpenetrating polymer network (IPN) beads possess porous matrix structure in alkaline pH whereas nonporous matrix structure was observed in acidic pH. The swelling of the beads and drug release was significantly increased when pH of the medium was changed from acidic to alkaline. The results of pulsatile swelling study indicated that the IPN beads changed their swelling behavior when pH of the external medium was altered. As pH of the medium was changed from 1.2 to 7.4, a considerable increase in swelling was observed for all the beads. However, swelling process was slower than the deswelling. At higher pH values, the carboxyl functional groups of hydrogels undergo ionization and the osmotic pressure inside the beads increases resulting in higher swelling. Drug release followed case II transport mechanism in acidic medium whereas anomalous/non-Fickian transport mechanism was observed in alkaline medium.