In vitro testing of surface-modified biomaterials.
The influence of surface modification treatments such as ion implantation and sputter coating on an in vitro rat bone-marrow cell culture was studied by scanning electron microscopy and X-ray microanalysis. 316 L stainless steel, Ti-6Al-4V and Ti-5Al-2.5Fe were nitrogen ion-implanted with three fluences: 10(15), 10(16) and 10(17) ion cm-2 with an energy beam of 40 keV. Both nitrogen and carbon sputter-coated 316 L stainless steel samples were also studied. Polished 316 L stainless steel, Ti-6Al-4V, Ti-5Al-2.5Fe and Thermanox were also studied, in order to give comparative information. The materials were inoculated with a droplet of cell suspension and were maintained for 3 wk. A mineralized extracellular matrix was formed on all materials except on nitrogen sputter-coated 316 L stainless steel. The morphology of the cell cultures obtained on nitrogen-ion implanted materials was similar to those obtained on the untreated materials and Thermanox. The observation of the interface between the cell layer and the substrata showed the presence of calcium- and phosphorus-rich globular deposits associated with collagen fibres. A higher density of these globular deposits was observed on the ion-implanted materials.