Preparation of germanium apatite and its cytotoxicity

Abstract

Germanium apatite was synthesized via the solid-state reaction between GeO₂ and (NH₄)₃PO₄. The synthesized materials were characterized using XRD, and thermal analysis was carried out using TG-DTA. Ge₂P₂O₇ was preferentially produced at temperatures between 300–900°C, and at temperatures above 1000°C, germanium apatite (Ge₅O(PO₄)₆, GeAp) was synthesized. In solubility tests, 0.36% and 0.65% of Ge ions were liberated from GeAp powder in distilled water at 37 and 80°C after four weeks, respectively. A GeAp aqueous solution maintained at 37°C was strongly acidic with a pH=1.67 after four weeks. The growth rate of human adult gingival fibroblast cells in a medium that included GeAp, HA, and GeO₂ was investigated. The growth rate of the cells in a 0.1 mg/ml GeAp medium was almost the same as that in the control. The cell growth was restricted in a 1.0 mg/ml GeAp medium, whereas the cell growth in a pH-adjusted 1.0 mg/ml GeAp medium at pH=7.60 was higher than that in non-adjusted medium at pH = 7.06.