On biological role of titanium

According to WebElements, “titanium has no biological role”. Having recently acquired a titanium (or rather, Ti₆AlV₄ alloy) dental implant, I am not convinced. To be a dental implant sounds like a perfectly valid biological role to me. Apparently, osteoblasts like to attach to titanium surface (more precisely, to titanium dioxide, TiO₂). However, it is not just the material that matters, it is the shape of the material as well. In the recent paper, in vivo bone binding to TiO₂ nanotubes and TiO₂ gritblasted surfaces was investigated. The authors have found that

after four weeks of implantation in rabbit tibias, pull-out testing indicated that TiO₂ nanotubes significantly improved bone bonding strength by as much as nine-fold compared with TiO₂ gritblasted surfaces.

Earlier this year, another study has demonstrated that the fate of human mesenchymal stem cells can be affected solely by the geometry of TiO₂ nanotubes:

Small (≈30-nm diameter) nanotubes promoted adhesion without noticeable differentiation, whereas larger (≈70- to 100-nm diameter) nanotubes elicited a dramatic stem cell elongation (≈10-fold increased), which induced cytoskeletal stress and selective differentiation into osteoblast-like cells...

Growing microtubes from polyoxometallate crystals

The long-awaited first issue of Nature Chemistry is out. It has a number of excellent reviews and research articles; best of all, it is all in free access. The cover shows the artist’s impression of “a growing microtube with a single polyoxometalate ion visible at the open end of the tube” [see Ritchie et al. (2009) Nature Chemistry 1, 47–52, and comment, Constable, E. (2009) Nature Chemistry 1, 22–23].