Hollow hydroxyapatite/polyelectrolyte hybrid microparticles with controllable size, wall thickness and drug delivery properties

Hybrid hydroxyapatite (HAP) microparticles with a hollow HAP core and a chitosan/hyaluronic acid (CHI/HA) multilayer shell were fabricated via the hydrothermal method and the layer-by-layer (LbL) self-assembly technique. Depending on the hydrothermal reaction time, the thickness of the HAP shell could be controlled and the size of the hybrid hollow microparticles varied between 850 nm and 2 mu m. The size and HAP shell thickness significantly affect the drug release property of the resulting hybrid microparticles. The DOX release results demonstrated that CHI/HA multilayers could potentially assuage the initial burst release of drug from the porous HAP matrix because the polymer multilayer shell acted as a barrier to control the exchange of the drug. In addition, the drug release of hollow hybrid HAP microparticles was pH-dependent because of the different electrostatic interaction in the CHI/HA multilayers at different pH values and the dissolution of the HAP hollow core under acidic conditions. The present paper provides a facile and green route for the fabrication of hierarchical hybrid drug carriers with controllable size, wall thickness and drug release properties by combining natural polyelectrolytes and hollow HAP microparticles, which is highly attractive for controllable drug delivery.