Carbon Nanotube Based Orthopedic Implant Sensors

Sirinrath Sirivisoot

Abstract In this chapter, the use of multiwalled carbon nanotubes (MWCNTs) as sensors for healthy bone growth will be discussed. MWCNTs are cytocompat-ible with osteoblasts (bone-forming cells) and enhance osteoblast calcium deposition, and thus, bone formation. Moreover, here, MWCNTs have been grown out of nanopores of anodized titanium (MWCNT-Ti), which has a surface layer of titanium oxide (a popular chemistry for orthopedic implants), to serve as a novel in situ orthopedic implant sensor. The electrochemical responses of MWCNT-Ti have been investigated in an attempt to ascertain if MWCNT-Ti can serve as novel in situ sensors for bone formation. MWCNT-Ti have been subjected to a ferri/ferrocyanide redox couple and its electrochemical behaviors measured. Cyclic voltammograms (CV) have demonstrated enhanced redox potentials of the MWCNT-Ti compared to Ti alone. These redox signals have been superior to that obtained by bare Ti, which does not sense either oxidation or reduction peaks in CV. Moreover, the redox reactions of MWCNT-Ti have been tested in a solution of extracellular bone components synthesized by osteoblasts in vitro. It has been found that MWCNT-Ti also exhibited well-defined and persistent CV, similar to the ferri/ferrocyanide redox reaction. The observed higher electrodic performance and electrocatalytic activity the MWCNT-Ti senses compared to bare Ti, are likely because of the fact that MWCNTs enhance direct electron transfer and facilitate double layer effects, leading to a strong redox signal. These collective results may encourage the further study and modification of MWCNT-Ti to sense new bone growth in situ next to implants and perhaps to monitor other events (such as infection and/or scar tissue formation) to improve the current clinical diagnosis of orthopedic implant success or failure.

Keywords Osteoblasts • Titanium • Multiwalled carbon nanotubes • Biosensing

Wake Forest Institude for Regenerative Medicine, Wake Forest University, Health Sciences, 391 Technology Way, Winston-Salem, NC 27157, USA e-mail: [email protected]

T.J. Webster (ed.), Nanotechnology Enabled In situ Sensors for Monitoring Health, 139

DOI 10.1007/978-1-4419-7291-0_7, © Springer Science+Business Media, LLC 2011

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