Enzyme-mediated oscillatory drug release through hydrogel membranes

Implantable polymeric drug-delivery devices have been constructed to deliver drugs at well-defined rates. Currently, an oscillator is under development that is fueled by endogenous compounds and contains a variable-permeability membrane. In this paper, a simple theoretical model has been developed for the membrane oscillator, and results of simulations based on the model are discussed. Diffusion-cell studies have been performed with a variable-permeability poly(N-isopropyl-acrylamide-co-methacrylic acid) hydrogel membrane. Using glucose as a probe solute, the results show that lowering the pH induces hydrogel volume collapse and cessation of glucose permeation across the membrane.