pH敏感瓜胶/聚丙烯酸半互穿网络水凝胶研究

Study of pH-Sensitive GG/PAA Semi-interpenetrating Polymer Network

制备了瓜胶/聚丙烯酸(GG/PAA)的半互穿网络(sem i-IPN)水凝胶,以N,N-亚甲基双丙烯酰胺(MBA)为交联剂,考察了加料量、溶胀介质pH对平衡溶胀率(ESR)的影响。结果表明:GG/PAA半互穿网络水凝胶的ESR在pH≤3时较小,pH>4后增加较快,pH=8.2时达最大值,继续增加pH,ESR又呈下降趋势,体系具有pH敏感性。在pH相同条件下,ESR随GG用量增加而减小,随丙烯酸(AA)用量增加而增大。pH=8.2、ρ(GG)从5 g/L增加到25 g/L时,ESR从3 142降低到1 026;当ρ(AA)用量从125 g/L增加到375 g/L时,ESR从1 195增加到2 611。m(MBA)∶m(AA)=(0.5∶100)^(1.2∶100)时,ESR略有增加。GG/PAA半互穿网络水凝胶的溶胀动力学表明,该类凝胶满足在胃液pH环境中溶胀率较小、小肠部位pH环境中溶胀率较高的要求,因此,通过调整配方,结合瓜胶只被结肠部位细菌降解的特性,GG/PAA半互穿网络水凝胶有望成为一种理想的靶向结肠给药载体。

A process was developed to prepare pH-sensitive guar gum/poly （ acrylic acid） （GG/PAA） hydrogels using N, N-methylenebisacrylamide as cross-linker with a semi-interpenetrating polymer network （semi-IPN） structure by free radical solution polymerization. Influence of feed composition and pH of the swelling medium on the equilibrium swelling ratio （ESR） was investigated. Results show that ESR of GG/PAA semi-IPN hydrogels with various feed composition is dependent on the pH of the swelling medium. At pH≤3.0 ,ESR is very low and shows little change with pH, but increases sharply with pH value in the range of 4.0-8.2, and goes to its maximum at pH 8.2 and then decreases with the increase of pH. In pH 8.2 buffer, ESR decreases from 3 142 to 1 026 when the amount of guar gum increases from 5 to 25 g/L in the composition, but increases from 1 195 to 2 611 with the increase of acrylic acid amount from 125 to 375 g/L. ESR increases slightly with the cross-linker amount changingfrom 0.5% to 1.2% （wt%） based on acrylic acid charged weight . The kinetic dynamics in buffers with the pH close to simulated gastric liquid and intestine liquid shows that the swelling ratio of the GG/PAA semi-IPN hydrogel （GAS） is higher in the latter than in the former. Thus,pH sensitivity and colonic-specific degradability of GG component could make GG/PAA semi-IPN hydrogels good candidates for colon-specific drug delivery carriers