Hierarchically organization of biomineralized alginate beads for dual stimuli-responsive drug delivery.

Compartmentalized biomineralized alginate beads ranging from the micro to the visible scales with thermal- and pH-responsive drug delivery properties have been prepared via a one-step method in the present paper. Hollow multilayer microcapsules made of aliphatic poly(urethane-amine) (PUA) and sodium poly(styrenesulfonate) (PSS) serve as drug container to slow down the drug release. The results indicate that internal hollow multilayer microcapsules could hinder the permeation of the encapsulated Vitamin B2 (VB2) and retard the initial burst release of VB2. In addition, the drug release of compartmentalized biomineralized alginate beads exhibit distinguished pH- and thermal-dependent property due to pH-responsive alginate and the thermal-responsive aliphatic PUA. The drug release decreases when decreasing the pH value because the compact construction of alginate and biomineralized layer could prevent VB2 release from the beads. 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). The results demonstrate that the compartmentalized biomineralized alginate beads show great potential as smart materials for controllable drug delivery.