Abstract: 
The aim of this work was to synthesize semi-Interpenetrating Polymer Network superporous hydrogels of hydroxypropyl guar and chitosan, by cross-linking chitosan with glyoxal and to study its swelling behavior for application as a gastroretentive drug delivery system. Chitosan- hydroxypropyl guar superporous hydrogels of metoprolol tartrate were synthesized by gas blowing method. The effect of pH on the swelling ratio was determined. Swelling reversibility studies were also carried out. Fourier transform infrared spectroscopy analysis and scanning electron microscopy studies were undertaken to characterize the drug loaded super porous hydrogels, while dissolution studies were carried out to assess release characteristics. Swelling was highly dependent on the extent of crosslinking and the amount of the polymer present in formulation. The higher the amount of cross-linking agent, lower was the swelling ratio. The superporous hydrogels were highly sensitive to pH of swelling medium, and showed reversible swelling and de-swelling behaviour while still retaining their mechanical stability. Apparent density was dependent on the volume of the superporous hydrogels and decreased with increasing crosslink density. Degradation kinetics showed that chitosan superporous hydrogels had good water retention capability. Drug release was inversely related to the amount of cross-linking agent. The studies revealed that chitosan- hydroxypropyl guar superporous hydrogels can be used as a gastroretentive drug delivery system in view of their swelling characteristics in acidic pH.

Keywords: Gastro-retentive Drug Delivery, Superporous Hydrogels, Chitosan, Hydroxypropyl Guar, Metoprolol Tartrate, Swelling Ratio.