Cross-linked pH-sensitive pectin and acrylic acid based hydrogels for controlled delivery of metformin

The purpose of present study is to load Metformin HCl into pH-sensitive hydrogels to have sustained release over a period of time. The hydrogel was synthesized from naturally occurring polysaccharide pectin and monomer acrylic acid (AA) using ethylene glycol dimethacrylate (EGDMA) as cross-linker under controlled conditions for polymerization at 45?C for one hr, 50?C for two hrs, 55?C for three hrs, 60?C for four hrs and finally 65?C for 12 hrs. Hydrogels were characterized for dynamic/equilibrium swelling, sol-gel fraction analysis, diffusion coefficient and percentage porosity. Hydrogels were tested by FTIR, XRD and SEM for structure and surface morphology respectively. Experimental in-vitro drug release data was applied to kinetic models. Formation of strong bonding between pectin and AA was supported by FTIR. The intensity of XRD peaks was reduced in non-loaded and loaded hydrogels compared to active drug substance. The non-loaded hydrogel showed discrete porous structure whereas loaded hydrogels were fibrous and smooth. Hydrogels showed higher swelling in the solutions of pH 6.5 and 7.5 as compared to in the solutions of pH 1.2 and 5.5. The diffusion coefficient decreases with the increase of AA and pectin concentrations. It was observed upon increasing the EGDMA concentration porosity decreases. The release of drug from all compositions of hydrogels took place through non-Fickian diffusion mechanism.