In vitro ion adsorption and cytocompatibility of dicalcium phosphate ceramics

In vitro cell testing of degradable bioceramics such as brushite or monetite is often challenging due to the ion release into or adsorption from the culture medium. These ionic changes are then mostly responsible for cell proliferation and activity, which prohibits the investigation of effects originating from surface topography or further material modifications.

Here, we aimed to solve this problem by developing a pre-conditioning regime following the repeated immersion of brushite and monetite samples in various Ca²⁺, Mg²⁺ and PO₄^3- containing electrolytes, followed by studying ion adsorption / release as well as changes in phase composition and in vitro cytocompatibility with MG63 cells.

The results demonstrated that by using DMEM cell culture medium in a ratio of 10 ml/sample was sufficient to minimize changes of ionic composition after 7 d with a daily change of the medium. This leads to changes of the surface composition with dissolution of the brushite phase. In turn, this also positively influences the in vitro cytocompatibility with a 2-3 fold higher cell number and cell activity on the DMEM pretreated surfaces.

Controlled sample washing prior to cell testing using DMEM medium seems to be a valuable procedure not only to stabilize the pH during cell culture but also to maintain ion concentrations within a cell friendly range.