Zn- and Mg-doped hydroxyapatite nanoparticles for controlled release of protein.

Bovine serum albumin (BSA) protein incorporated with hydroxyapatite (HA) nanoparticles (NPs) were synthesized by an in situ precipitation process. 2 mol % Zn(2+) and Mg(2+) were used as dopants to synthesize Zn(2+)/Mg(2+)-doped HA-BSA NPs. In our study we used BSA as a model protein. The amount of BSA uptake by doped and undoped HA NPs and subsequent release of BSA from NPs were investigated. Zn-doped HA NPs showed the highest amount of BSA uptake, whereas the amount of BSA loaded in undoped HA NPs was the lowest. A two-stage BSA release profile from doped and undoped HA NPs was observed in phosphate buffer solution (PBS) at pH 7.2 +/- 0.2. The initial burst release was due to the desorption of BSA from the HA surface. The later stage of slow release was controlled by the dissolution of BSA incorporated HA NPs. The BSA release rate from Zn-doped HA NPs was found to be the highest, whereas undoped HA NPs released BSA at the slowest rate. Our study showed that the protein release rate from HA NPs can be controlled by the addition of suitable dopants, and doped HA-based NP systems can be used in bone growth factor and drug release study.