Effects of niobium ions released from calcium phosphate invert glasses containing Nb ₂O ₅ on osteoblast-like cell functions

The effects of niobium ions released from 60CaO-30P ₂O ₅-(10-x)Na ₂O-xNb ₂O ₅ (mol %, x = 0-10) glasses on MC3T3-E1 cell functions were evaluated by culture tests with two systems; cell culture on glass plates, or in culture media containing glass extracts. Alkaline phosphatase (ALP) activity in the cells cultured on the glass plates containing 3 and 5 mol % of Nb ₂O ₅ was significantly higher than that on the Nb ₂O ₅-free glass, although proliferation was not enhanced on all glasses containing Nb ₂O ₅. Cells cultured in the medium containing 3 × 10 ^-7 M niobium ions showed the highest ALP activity in comparison with other Nb-containing media or normal medium, regardless of the presence of osteogenic factors (ascorbic acid, β-glycerophosphate and dexamethasone) in the media. Calcium deposition by the cells cultured in the medium containing 3 × 10 ^-7 M niobium ions was twice as high as those cultured in medium containing no niobium ions. The effects of niobium ions were thought to depend on ion concentration, and to enhance differentiation and mineralization of osteogenic cells rather than their initial adhesion or proliferation.