Commercially pure metal niobium (c.p. Nb) as well as niobium–molybdenum (Nb–Mo)
alloys were produced following several powder metallurgical routes. In brief, niobium and
molybdenum powders were blended and milled in order to form Nb–Mo alloys. The alloy
powders and the c.p. Nb were then either pressed and sintered, or cold isostatically pressed
followed by hot isostatically pressing. In order to assess the cytotoxicity of the c.p. Nb and
c.p. Mo powders, a 72 h minimal essential medium-extraction test was performed according
to ISO/EN 10993–5. The cytotoxicity of the c.p. Nb metal and the Nb–Mo alloys was tested in
a 72 h direct contact test. Compared to a negative control (UHMWPE), c.p. Nb was non-toxic,
but c.p. Mo was moderately toxic. None of the powder metallurgically produced materials
were toxic. Neither differences in molybdenum concentration, nor in porosity of the
samples, due to different production routes, had any influence on the toxicity of the
materials. Rat bone marrow cultures showed that only on c.p. Nb was a mineralized
extracellular matrix formed, while on the more porous Nb–Mo alloys, cell growth was
observed, but no mineralization. In conclusion, c.p. Mo powder is moderately toxic,
however, as an alloying element it is non-toxic. Material porosity seems to influence
differentiation of bone tissue in vitro.
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