Swelling Kinetics and Theophylline Controlled-Release Properties of pH-Sensitive P(AM-AA-co-C8PhEO10Ac) Hydrogel

A pH-sensitive P(AM-AA-co-C8PhEO10Ac) hydrogel was prepared using acrylamide(AM), acrylic(AA) and octylphenyl polyoxyethylene acrylate(C8PhEO10Ac) as monomer by free radical crosslinking polymerization. Effect of pH and monomer ratio on swelling property, swelling and deswelling kinetics of the hydrogels were studied. Theophylline was chosen as a model drug and the controlled-release properties of hydrogels in stimulated gastric fluid (pH=1.4) and intestinal fluid (pH=7.4) were studied. Results showed that the hydrogel had the rapid swelling, deswelling rate and good pH sensitivity. The dynamic swelling behavior of P(AM-AA-co-C8PhEO10Ac) hydrogels belonged to non-Fickian mode in pH=7.4 buffer solutions. The cumulative release rates of drug-loaded hydrogels in stimulated intestinal fluid were higher than those in stimulated gastric fluid. The cumulative release rate of theophylline was the highest when n(C8PhEO10Ac)∶n(AM)∶n(AA) was 1∶20∶30.