doi:10.1038/nindia.2008.176 Published online 7 April 2008
Researchers in Madras have devised a tiny biosensor that can detect glucose even in minute amounts of blood samples. The carbon nanotube-based sensor is highly sensitive and stable in determining glucose in blood and urine for the diagnosis of diabetes.
Carbon nanotubes have proved to be versatile materials. The researchers took phenazine dye neutral red (NR) and Nafion (Nf), a perfluorinated ionomer. NR aids in enzymatic reactions for electrochemical investigations of biological samples and Nf traps enzymes and proteins on electrode. Using solvent casting process, the researchers produced a nanobiocomposite film mixing NR-modified multiwalled carbon nanotubes (MWNTs), glucose oxidase (GOx) and Nf and another film mixing MWNTs-GOx-Nf.
Then they developed three working electrodes — paraffin impregnated graphite electrodes (PIGEs), PIGEs coated with MWNT-NR-GOx-Nf film and PIGEs coated with MWNT-GOx-Nf film.
When exposed to human blood samples at negative potential, the nanobiocomposite film coated electrode exhibited better response for glucose determination compared to MWNT-GOx-Nf coated electrode and bare electrode.
It responded in both acidic and alkaline solution with maximum response at pH 7.4. Besides maximum response at 50°C, the biosensor showed no significant change in current response over the 3-month period when stored at 4°C. Such stability is crucial for any commercial biosensor device.
If positive potential is applied, substances like ascorbic acid, dopamine, and glutathione in blood samples undergo oxidation hampering the determination of glucose. "At negative potential, all these interfering compounds are eliminated, which is very vital in the detection of blood glucose level," says lead researcher S. Sriman Narayanan from the Department of Analytical Chemistry at the School of Chemical Sciences of University of Madras.
- Jeykumari, D. R. S. et al. A novel nanobiocomposite based glucose biosensor using neutral red functionalized carbon nanotubes. Biosens. Bioelectron. 23, 1404-1411 (2008)