Kinetics of Drug Release from Drug Carrier of Polymer/TiO2 Nanotubes Composite-pH Dependent Study

This study was to investigate the kinetics of drug release from polymer/TiO2 nanotubes composite. Lidocaine and carprofen were selected as model drugs to represent weak base and weak acid drugs, respectively. Mathematical models used to fit the in vitro drug release experimental data indicate that at higher pH, the drug release was first order diffusion controlled. At lower pH, the release of the two drugs exhibits two staged controlled release mechanism. The first phase is due to drug diffusion and the second stage is a result of poly(lactic-co-glycolic acid) (PLGA) polymer degradation. The rate of drug release from polymer/TiO2 nanotubes drug carrier was mainly controlled by three pH dependent factors: the solubility of the drug, the degree of polymer swelling/degradation, and the electrostatic force between polymer and drug. This study suggests that controlled release could be achieved for polymer/ TiO2 nanotubes drug carrier via the modulation of pKa values of polymers and drug solubility. (C) 2014 Wiley Periodicals, Inc.