pH-sensitive starch-g-poly(acrylic acid)/sodium alginate hydrogels for controlled release of diclofenac sodium

The pH-sensitive starch-g-poly(acrylic acid)/sodium alginate (St-g-PAA/SA) hydrogel beads for the controlled release of diclofenac sodium(DS) were prepared simply by crosslinking SA using calcium ions under the existence of the St-g-PAA superabsorbent. The St-g-PAA/SA-DS hydrogel beads were characterized by IR and scanning electron microscopy. The effects of weight ratio of St-g-PAA to SA and pH on the swelling behaviors of the hydrogel beads in pH 7.4 phosphate buffer solution were investigated. In addition, the effects of weight ratio of St-g-PAA to SA and the concentration of SA solution on the entrapment efficiency (EE) for DS and the cumulative release of DS were studied in detail. The St-g-PAA/SA-DS hydrogel beads are pH-sensitive with an interpenetrated polymer network. The introduced St-g-PAA superabsorbent has great influence on the swelling behavior and the cumulative release of DS. The pristine SA-DS hydrogel beads disintegrated in pH 7.4 phosphate buffer solution in 3 h, whereas the disintegration of SA-DS beads was delayed or avoided by introducing a proper amount of the St-g-PAA superabsorbent. Also, the burst release of DS was successfully overcome by the introduced St-g-PAA superabsorbent. A weight ratio of St-g-PAA to SA of 1:9 and an SA concentration of 4 wt % are very helpful for the sustained release of DS.