A well-known perfluorosulfonated polymer (Nafion) has been used to solubilize single-wall and multiwall CNTs. Nafion bears a polar side chain and hydrophobic backbone. The hydrohobic interaction is between the side-wall of CNTs and the backbone of Nafion, while the polar side-chain of the polymer leads to the solubilization of CNTs in polar solvents like aqueous buffer solutions.

The Nafion-induced solubilization of CNTs permits various manipulations, including the modification of electrode surfaces and the preparation of biosensors or biofuel cells. The resulting biosensors greatly benefit from the coupling of the efficient electrocatalytic action of CNTs toward hydrogen peroxide and NADH with the antifouling/discriminative properties of Nafion films.

In conclusion, this work is highly important because it provides a new way for the fabrication of CNT-based biosensors or biofuel cells. This probably explains why this paper has attracted the attention of so many other research groups. Recently, we summarized the latest work in this area in a review article. (Y.H. Lin, W. Yantasee, F. Lu, J. Wang, M. Musameh, Y. Tu, and Z. Ren. 2004. "Biosensors Based on Carbon Nanotubes." In Dekker Encyclopedia of Nanoscience and Nanotechnology, ed. J. A. Schwarz, C. Contescu, K. Putye, pp. 361-373. Marcel Dekker, New York.)

Yes. We have discovered a new way for the fabrication of biosensors/biofuel cells by wrapping CNTs with an ionic polymer and solubilizing them in an aqueous solution. The CNTs/Nafion-dispersed solution is compatible with many enzymes and successfully used in our work for enzyme immobilization and biosensor fabrication. This new biosensor fabrication method is suitable for the fabrication of various biosensors or biofuel cells based on redox enzymes, which has been the topic of interest for several other research groups since our paper was published.

In spite of the many great properties of carbon nanotubes, working with carbon nanotubes has been difficult because of their poor solubility. This work found that a carbon nanotube can be made solubilize with the help of a polymer substance called Nafion.

Using Nafion in a buffer solution, both enzyme molecules and carbon nanotubes can be dispersed in aqueous solutions, and the carbon nanotubes/Nafion/enzyme-mixed solution can be coated on an electrode surface to form a selective biosensor or biofuel cell.

The approach is generally applicable for the fabrication of other enzyme-based biosensors/biofuel cells and provides a new way for biosensor/biofuel cell development. Further work based upon this discovery will lead to the development of novel biosensors/biofuel cells which will greatly benefit the biomedical and environmental monitorings.

Exploiting new nanoscale materials for electrochemical sensor/biosensor development has long been the research focus of both the PNNL and the NMSU groups. I (Yuehe Lin) worked with Prof. Wang on biosensor development about 12 years ago at NMSU as a postdoctoral fellow. Since joining PNNL seven years ago, I have been collaborating with Prof. Wang’s group in conducting electrochemical sensors/biosensor research.