Porous Hydroxyapatite Microspheres Prepared by Using Poly (Allylamine Hydrochloride) and its Application in Drug Delivery

Porous and hollow hydroxyapatite(HAP) microspheres were synthesized successfully in hydrothermal method utilizing poly(allylamine hydrochloride)(PAH) as the crystal growth regulator. Effects of reaction time and concentration of the polymer on the growth of final products were investigated. Uniform microspheres with dense pores can be synthesized by controlling the PAH concentration(0.3-0.5 g/L) after 12 h hydrothermal reaction at 150℃. Formation of hollow microspheres includes different stages of early precursor microstructures, heterogeneous nucleation and phase transformations. At different stages, the cationic polyelectrolyte PAH plays an important role in regulating growth of hollow microspheres. Ibuprofen(IBU) was chosen as a typical model drug to study the drug loading and the desorption ability. The results show that porous and hollow microspheres have relatively high drug loading capacity(413.65 mg/g). Drug release of the microspheres is favorably p H-responsive, which may have close relationship with the surface properties of HAP nanorods. Date from this study suggest that the porous microspheres will have potential application as the targeted-drug carrier in the biomedicine field.