May 20, 2010
Carbon nanotubes as biosensors: realizing the full potential
Carbon nanotubes (CNTs) are exceptionally multifaceted nanomaterials that have a wide range of potential applications such as electrodes, power cables, fibres, composites, actuators, sensors and many other devices. However, transforming their exceptional properties at the nanoscale towards macroscopic applications has been challenging. Recently, CNT microfibres with these unique properties have been developed in such a way to give multilayered nanotube bundles concentrically assembled in seamless tubules along the yarn axis. Researchers in the UK led by Dr Wenhui Song and Prof. Francis Moussy at Brunel University in collaboration with Prof. Ya-Li Li at Tianjin University, China, have applied these novel CNT nano-yarn fibres as electrodes for glucose biosensing and proved that a 10 times smaller CNT-fibre electrode outperforms a traditional Pt-Ir-based metal electrode, which is a step closer to realizing the full potential of CNTs as biosensors.
The CNT fibre (figure 1a; click on the image to enlarge) is spun directly from a chemical vapour deposition (CVD) reaction and consists of double-walled CNTs self-assembled into nanobundles that are organized into multiple concentric nanolayers. It resembles a scaled-down multistranded electric wire and has a nanoscale surface topography and porosity (figure 1b). The CNT bundles at the end of the fibre are unwound to form a brush-like structure that can be used as an electrode for glucose biosensing (figure 1c).
The individual CNT bundles within the brush-like end act as multi-nanoelectrodes that facilitate the efficient capture and promotion of electron transfer reactions, as well as increase the electro-active surface area for enzyme immobilization. The Brunel team designed and fabricated the amperometric glucose biosensor by immobilizing glucose oxidase at the brush-like end of the CNT fibre.
Owing to its small size, high electrochemical activity, excellent physical properties, low density and biocompatibility, the CNT fibre has huge potential for implantable applications for continuous monitoring of clinically relevant analytes, including glucose (to aid the control of diabetes), lactate, antibodies and antigens. Other areas of interest include the analysis of analytes in bioreactors, veterinary and clinical chemistry, the food industry and environmental science.
Currently the Brunel team is addressing the long-term ex vivo and in vivo stability of the CNT-fibre-based glucose biosensors, and exploring other biosensor applications for CNT fibres.
More details can be found in the journal Nanotechnology.
About the author
The work was performed by a collaborative team from the Wolfson Centre for Materials Processing and Brunel Institute of Bioengineering (BIB), both Brunel University, UK. Dr Zhigang Zhu, the research fellow who performed the experiments, now works as a research associate at the University of Cambridge, UK. Dr Wenhui Song is a lecturer at the Wolfson Centre for Materials Processing, School of Engineering and Design. Dr Krishna Burugapalli is a research fellow, leading the biosensor group at BIB. Prof. Francis Moussy is head of diagnostics research at TDR, the Special Programme for Research and Training in Tropical Diseases, at the World Health Organization in Geneva, Switzerland, but is still a visiting professor at Brunel. The carbon nanotube fibre was produced by Xiao-Hua Zhong, a PhD student in Prof. Ya-Li Li's group, School of Materials Science and Engineering, Tianjin University, China.