Crystal structure optimization, ultrasonic properties and morphology of Mg/Se co-dopant into annealed hydroxyapatite for biomedical applications

Binary doped hydroxyapatite (HAP) with selenite ( $$SeO_{3}^{2 - }$$ ) and magnesium (Mg) ions have been fabricated in different contents of Mg(II) using the co-precipitation method. The crystal structure of the co-doped compositions has been investigated and showed that the crystallographic sites of Ca(2) are energetically preferred for Mg(II) substitution. Moreover, the c/a ratio indicates that crystal growth was promoted in a-direction upon additions of Mg(II). Furthermore, the maximum roughness peak height increased from 113.8 to 216.9 nm for x = 0.0 and 1.0, respectively. In addition, the microhardness has been examined and exhibited a growth upon Mg(II) contributions, starting from 2.4 ± 0.1 GPa up to 4.6 ± 0.3 GPa for the compositions of x = 0.0 and 0.6, respectively. The cell viability was examined against human osteoblasts cell lines in vitro and progressed to 98.2 ± 3.2% at x = 0.8. The high biocompatibility, thermal stability, and adequate mechanical properties encourage their utilization for numerous potential applications.