Fabrication and characterization of a novel semi-interpenetrating network hydrogel based on sodium carboxymethyl cellulose and poly(methacrylic acid) for oral insulin delivery

In this research, pH-sensitive semi-interpenetrating polymer network hydrogels based on sodium carboxymethyl cellulose and poly(methacrylic acid) were synthesized using free radical polymerization and semi-interpenetrating polymer network approach for oral administration of insulin. The chemical structure and thermal stability of the hydrogels were characterized using Fourier transform infrared spectroscopy, X-ray diffraction, and thermogravimetric analysis measurements. The interior morphology was observed by scanning electron microscopy and the inner structure exhibited a porous honeycomb-like shape. The investigations on the swelling properties of hydrogels revealed their ability to response to pH value change. The in vitro release behavior of insulin was pH dependent and the release of insulin was much lower at pH 1.2 compared to pH 6.8. In vitro cytotoxicity assay indicated that the hydrogels were noncytotoxic to HeLa cells. A sustained reduction in blood glucose level was observed after oral administration of insulin-loaded hydrogel to diabetic rats at 75 IU/kg. These results indicated that the hydrogel would be a promising vehicle for oral insulin delivery systems.