Biomaterials are widely used in clinical practice as bone graft substitutes for treating patients with bone defects. A molecular level understanding of the chemical processes at the interface between the biomaterial and the biological environment is crucial to succeed in tissue regeneration and to predict the treatment outcome. In this study, we used three different bone graft substitute materials (BioGlass 45S5 -synthetic, Bio-Oss -bovine derived and Algipore -derived from algae) which were incubated in an α-minimum essential medium (α-MEM) during 1, 3 and 7 days. Initial surface composition of the biomaterials and the chemistry of their solid-solution interface were monitored by XPS with a fast-frozen samples technique. The XPS analysis showed that the equilibrium at the solid-solution interface is reached within 24 h. The Na/Cl atomic ratio at equilibrium indicates a negatively charged surface for Bio-Oss. In contrast, the other two materials gained a positive surface charge, which resulted in pronounced adsorption of amino acids at the interface from the medium. The surface chemical reconstruction and charge generation mechanism responsible for this effect are discussed with regard to bulk composition of the materials and possible proliferation and differentiation cell patterns that could be expected at the interface.

Dissolution-precipitation reactions occur at the surface of Bio-Oss, and osteogenic responses are seen at the biological interface. The concentration of Bio-Oss is a key factor for the experimental in vitro results, and may also have implications for the clinic.

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