Controlled release of DNA from zinc and magnesium ion-doped hydroxyapatites

Hydroxyapatite (HA) is a biocompatible and porous material that is useful for gene delivery. In this study, various Zn- and Mg-doped HA samples were produced by adding the ions at different dopant concentrations to control the association and dissociation of DNA. Although the HA crystal structure was retained after doping, it became distorted with increasing doped metal concentration. In 20% Zn-doped HA, a secondary Zn(OH)2 phase was observed. Mg-doped HA did not show significant cytotoxicity against breast tumor cells and osteoblasts. But, highly Zn-doped HAs were toxic, suggesting that doped Zn ions affected the cells. DNA could effectively adsorb to HA, regardless of metal ion doping, but the dissociation behavior of DNA differed. DNA was gradually released from Mg-doped HA for over a week, independent of Mg dope concentration, but not from Zn-doped HA, except for 20% doping. Therefore, the release properties of HA can be controlled by doping with suitable metal ion species at an appropriate dosage.