Directed osteoblast adhesion at particle boundaries: Promises for nanophase metals

In spite of under performance, metals and metal alloys are currently being used in orthopedic implantable devices. Poor osseointegration, severe stress shielding, bone cell death and eventual necrotic bone resulting from the generation of wear debris are known to be some of the reasons responsible for their under performance. In addition, metallic corrosion products may also initiate cancer. Steady growth in the use of metals in orthopedic applications inspired researchers to deal with these problems in an integrated way. When conventional Ti, Ti6A14V, and CoCrMo surfaces were modified to the nano-range, this study showed increased percentages of osteoblast (bone forming cell) adhesion on nanophase metals. Moreover, larger amounts of osteoblast adhesion was related to quantitative increases in the total length of particle boundaries per unit area and the total number of pores between surface particles per unit area, and the surface particle boundary index (SPBI) of nanophase metals. Additionally, we have developed a novel anticarcinogenic orthopedic metalloid, selenium (Se). When micron range surface particles of Se compacts were modified to the nano-range by chemical etching, we found positive relationships between directed osteoblast adhesion and various particle boundary parameters mentioned above under in vitro conditions. These results provided the first evidence to utilize nanosurface Se as an anticarcinogenic and bio-inspiring material for future applications in orthopedic metallic devices.