In vitro biocompatibility of duplex stainless steel with and without 0.2% niobium.

Stainless steel is frequently used as a biomaterial. Chemical composition alterations can be undertaken to improve its mechanical and biological properties. This investigation aimed to compare the biocompatibility of duplex stainless steel, with and without 0.2% niobium, with austenitic stainless steel and titanium-6-aluminium-4-vanadium (Ti6Al4V) using rat bone marrow (RBM) cell culture. Cell attachment was evaluated at 24 hr. Cell proliferation, cell viability, total protein content, and alkaline phosphatase (ALP) activity were evaluated at 7, 14 and 21 days. Bone-like nodule formation was evaluated at 21 days. Cell attachment, proliferation and viability were unaffected by the chemical composition of the stainless steels and the Ti6Al4V. Total protein content, ALP activity, and bone-like nodule formation were unaffected by the chemical composition of the stainless steels, but these parameters were greater on the Ti6Al4V than on the stainless steels. Our results demonstrated that initial cell events were unaffected by the chemical composition of the tested alloys, while events indicating osteoblast differentiation including increased ALP activity and bone-like nodule formation were favored by the Ti6Al4V. Moreover, the evaluated parameters were unaffected by the presence of niobium in the stainless steel composition. As niobium affects microstructure and, consequently, improves the mechanical properties of duplex stainless steel, it is suggested that the addition of niobium to metallic alloys could be useful in developing alloys with acceptable biocompatibility and improved mechanical features. (Journal of Applied Biomaterials & Biomechanics 2004; 2: 162-8).