Effects of solution pH on ion distribution and drug release behaviors of a weak polyelectrolyte hydrogel

In this article, a triphasic model is developed and the finite element method is adopted to research weak polyelectrolyte hydrogel. The influence of HCl concentrations in external solution on ion concentrations inside the hydrogel as well as the evolution of water volume fraction is discussed. The conservation of charge can be reached everywhere in the hydrogel. Besides, drug release equation which both considers the convection and diffusion effects is employed to analyze the drug release rate. The results show that the drug release rate has a very close relationship with the pH value. Afterwards, the simulated results are compared with experimental results of Beebe to validate the reliability and accuracy of this simulation. This work is significant in studying the oral drug controlled release in gastrointestinal tract.