Hollow Multilayer Microcapsules for pH-/Thermally Responsive Drug Delivery using Aliphatic Poly(urethane-amine) as Smart Component

Hollow multilayer microcapsules made of aliphatic poly(urethane-amine) (PUA) and sodium poly(styrene sulfonate) (PSS), templated on PSS-doped CaCO 3 particles, are prepared for pH-/thermally responsive drug delivery. The electrostatic interaction and hydrogen bonding under weak-acid conditions between aliphatic PUA and PSS contribute to the formation of multilayer microcapsules. Scanning electron microscopy (SEM) results demonstrate an obvious variation of the hollow multilayer microcapsules in response to changes in temperature and pH value. Drug-release behaviors using DOX as a model drug demonstrate that the drug release increases on decreasing the pH value because of the interaction weakness between aliphatic PUA and PSS in acidic conditions. Moreover, the drug release is higher at 55 °C than that at 37 °C for the sake of the shrinkage of aliphatic PUA above its lower critical solution temperature (LCST).