Low-Temperature Hydrothermal Synthesis of Hierarchical Porous Hydroxyapatite Microsphere with Co-substituted Essential Trace Elements for pH-responsive Drug Delivery

Abstract

Hierarchical hydroxyapatite microspheres composed of two porous hemispherulites have been synthesized hydrothermally at 80°C. A possible formation mechanism was proposed. The drug loading and release properties were further investigated. [Formula: see text] 3D hierarchical microspheric hydroxyapatite (HAp) composed of two porous hemispherulites was hydrothermally fabricated at low temperature with the aid of urea and NaNO 3, Mg ( NO 3)2, KNO 3, NH 4 Cl and NH 4 F as the homogeneous precipitation reagent and substituted ion sources. In this novel strategy, the element-substitutions serve as regulating agents for the self-assembly of porous HAp microspheres from the dumbbell-like particles to two hemispheres with radius of about 10 μm. Furthermore, the as-prepared hierarchical HAp microspheres exhibit high drug-loading capability and superior sustained release properties, which make it a promising carrier for pH responsive drug delivery system.