3.3.3. Long Term Cell Proliferation on FGM

As demonstrated in Figure 5, the cells could not proliferate for the Mo containing sample and even not adhere at high Mo concentration, so only the Nb containing sample were investigated in term of cell proliferation. Figure 7 presents an example of the number of cells after three, seven, 14 and 21 days in the polished TiNb sample for the same donor. Figure 7 shows that if the total number of cells increased during the 21 days, the proliferation depended on the composition. Niobium had the fewest cells in the first week but then became the location in the gradient where proliferation was the most important. Thus, after three weeks, it became the best material with the highest cell number. Despite the fact that niobium was not used as such in prostheses because of its mechanical properties that were too far from those of the bones (higher Young modulus) [51], this test demonstrated the perfect biocompatibility of pure niobium [50]. In addition, this type of test validated the fact that FGM can be used successfully in biocompatible experiments to decrease the number of needed samples for long term proliferation test.

**Figure 7.** Cells proliferation: example of polished TiNb.
