Topographical evolution of nanocrystalline diamond and its effect on osteoblast interactions

The potential of nanocrystalline diamond films (NDFs) for biological applications has been addressed by a variety of recent researchers. In the present work, we consider the topographical evolution of NDFs fabricated by microwave plasma assisted chemical-vapor-deposition (MPCVD) and its influence on osteoblast (bone forming cells) functions. One group of NDFs formed in this study were grown with 0.67% methane, 5%similar to 20% hydrogen and argon. The other group of NDFs composed of nano diamond and amorphous carbon was created with indirect exposure to plasma with 0.67% methane, 20% hydrogen and argon. Scanning electron microscope (SEM) images revealed that the nano diamond grains in the first group of NDFs evolved from round shapes into faceted and successively cubic shapes as hydrogen increased, whereas the second group of NDFs consisted of nano platelet grains. Atomic force microscopy (AFM) analysis confirmed this evolution as well as the variation of surface roughness. Cell results demonstrated that osteoblast adhesion and proliferation on NDFs varied dramatically depending on the different topographical features of the films. Specifically, results showed that NDFs with grain size less than 100 nm could be coated on the stem of a hip implant to promote cell adhesion. In contrast, NDFs with grain size greater than 200 nm or NDF with nano platelet grains may be optimal for the inside of acetabular articulation where cell adhesion is not preferred but wear-resistance is important. Further observation by contact angle measurement suggested that the differences in cellular adhesion and proliferation were related to the wettability associated to the topographical features of NDFs surfaces.