Dual-Responsive Semi-Interpenetrating Network Beads Based on Calcium Alginate/Poly(N-isopropylacrylamide)/Poly(sodium acrylate) for Sustained Drug Release

To improve the mechanical strength of natural hydrogels and to obtain a sustained drug-delivery device, temperature-/pH-sensitive hydrogel beads composed of calcium alginate (Ca-alginate) and poly(N-isopropylacrylamide) (PNIPAAm) were prepared in the presence of poly(sodium acrylate) (PAANa) with ultrahigh molecular weight (M-eta >= 1.0 x 10(7)) as a strengthening agent. The influence of PAANa content on the properties, including the beads stability, swelling, and drug-release behaviors, of the hydrogels was evaluated. Scanning electron microscopy and oscillation experiments were used to analyze the structure and mechanical stability of the hydrogel beads, respectively. The results show that stability of the obtained Ca-alginate/PNIPAAm hydrogel beads strengthened by PAANa the alginate/ poly(N-isopropyl acrylamide) hydrogel bead (SANBs) was significantly improved compared to that of the beads without PAANa (NANBs) at pH 7.4. The swelling behavior and drug-release capability of the SANBs were markedly dependent on the PAANa content and on the environmental temperature and pH. The bead sample with a higher percentage of PAANa exhibited a lower swelling rate and slower drug release. The drug release profiles from SANBs were further studied in simulated intestinal fluid, and the results demonstrated here suggest that SANBs could serve as a potential candidate for controlled drug delivery in vivo. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 122: 729-737, 2011