In vitro biomineralization by osteoblast-like cells I. Retardation of tissue mineralization by metal salts

The cytocompatibility of stainless steel 316L (SS 316L) corrosion products was investigated with particular focus on the dose- and time-effect of electrochemically dissolved SS and the corresponding separate metal ions on osteogenic bone marrow derived cells. Type AISI 316L stainless steel (Fe 63.9%, Cr 18.0%, Ni 12.5%, Mo 2.8%, Si 1.2%, Mn 1.6% and C 0.025%, weight for weight) was anodically dissolved in Hankʹs Balanced Salt Solution (HBSS) and diluted to the following concentrations: 500 μg ml−1 of Fe, 122 μg ml−1 of Cr and 101 μg ml−1 of Ni, as estimated by atomic absorption spectrometry. Similarly, salt solutions containing 500 μg ml−1 of Fe (FeCl3 · 6H2O), 122 μg ml−1 of Cr(CrCl3 · 6H2O) or 101 μg ml−1 of Ni (NiNO3) were prepared. All solutions were diluted 1:103, 1:104 and 1:105 and their effects on cell proliferation and function of rabbit bone marrow cells were studied up to 28 days of culture. Bone marrow cells (second subculture) were cultured in α-Minimal Essential Medium (α-MEM) supplemented with 10% fetal bovine serum 10−8 moll−1 dexamethasone, 2.52 × 10−4 moll−1 ascorbic acid and 10−2 moll−1 β-glycerophosphate. The osteoblast response to the presence of metal ions was evaluated by biochemical assays (enzymatic reduction of MTT for evaluation of cell viability/proliferation, and estimation of alkaline phosphatase (ALP) activity) and histochemical assays (identification of ALP positive cells and calcium and phosphates deposits). Results suggest a decrease in the expression of the osteoblast phenotype in the presence of ion and alloy solutions. Stainless steel corrosion products elicited slight effects but the corresponding metal ions produced pronounced effects on the osteoblast phenotype, namely an alteration in the levels and temporal expression of ALP and lower and retarded tissue mineralization ability.