Published online by Cambridge University Press: 01 February 2011
The objective of this in vitro present study was to create a biosensor which can monitor in situ orthopedic tissue growth juxtaposed to a newly implanted orthopedic material. This biosensor has unique properties including the ability to sense, detect, and control bone regrowth. Such a biosensor is useful not only in regenerating tissue necessary for orthopedic implant success, but also to aid in informing an orthopedic surgeon whether sufficient new bone growth occurred. If the sensor determines that insufficient new bone growth occurred, the sensor can also act in an intelligent manner to release bone growth factors to increase bone formation. The primary biomaterial in this biosensor is anodized Ti, developed by chemical etching and passivation treatments. Carbon nanotubes (CNTs), because of their electrical and mechanical properties, are essential to consider when designing such biosensors since they will be used to apply and measure conductivity changes as new bone grows next to the implant. For this, parallel multiwall CNTs were grown from the pores of the anodized Ti by a chemical vapor deposition process. Lastly, these sensors will be composed of a conductive, biodegradable, polymer layer that degrades when bone grows and, consequently, undergoes a change in conductivity that can be measured by the CNTs grown out of the anodized Ti. This conductive, biodegradable polymer consists of polypyrrole (which is conductive) and poly-lactic-co-glycolic acid (which is biodegradable). Preliminary in vitro results suggest that osteoblast functions (specifically alkaline phosphatase activity and calcium deposition) on CNTs grown on anodized Ti are significantly enhanced when compared to anodized Ti and currently-used Ti; thus, it is anticipated that bone growth could be enhanced on these novel biomaterial sensors.