Silica coating of carboxymethyl tamarind kernel polysaccharide beads to modify the release characteristics

In present study, the release characteristics of ibuprofen-loaded carboxymethyl tamarind kernel polysaccharide beads were modified by coating with silica. The influence of concentrations of carboxymethyl tamarind kernel polysaccharide, calcium chloride and tetraethoxysilane on the % entrapment and in vitro release of ibuprofen was optimized using response surface methodology. The coating of beads with silica restricted the drug release from the beads but at the same time the ethanol formed as by-product of the sol gel process leached out the drug. The optimized batch of beads were prepared using carboxymethyl tamarind kernel powder-12.5 (%, w/v), calcium chloride-10.12 (%, w/v) and coated with tetraethoxysilane-0.25 M, entrapped 89.2% and released 92% of drug over 24 h. Energy dispersive X-ray analysis confirmed the coating of silica on the beads. The coating with silica shielded the crevices on the surface of beads but it did not elicit any significant change in thermal stability of beads. Further, in vitro release was found to be in good agreement with the swelling study. Modeling analysis revealed that ibuprofen was released from the beads following zero-order kinetics with erosion of the matrix as the main mechanism of drug release. Thus, silica coating provides a facile strategy to formulate sustained release formulations.