doi:10.1038/nindia.2012.142 Published online 26 September 2012
Researchers have developed a new kind of biosensor that can detect extremely low concentrations of alcohol in human serum samples. The researchers made the biosensor using alcohol oxidase (AOx) isolated from yeast, a gold electrode, multi-walled carbon nanotubes (MWCNTs), nafion and polyethyleneimine (PEI).
Detection and quantification of alcohol levels are needed in clinical and forensic analyses, and the food, beverage and pulp industries. Most existing detection methods are complex and time-consuming. In addition, recent alcohol biosensors that use alcohol dehydrogenase need a constant supply of a co-factor, nicotinamide adenine dinucleotide.
To create a better and more effective technique for alcohol detection, the researchers took a cleaned gold electrode, then spread a solution of MWCNTs and nafion over the electrode. On top of this, they smeared AOx solution and covered with PEI solution, yielding the alcohol biosensor.
Efficacy of the biosensor was tested by exposing it to alcohol solution and alcohol-containing human serum samples and comparing the results with two other electrodes — a platinum rod as counter electrode and a silver chloride-based reference electrode.
In electrochemical studies, an increase in redox current at 0.27 V was observed for the alcohol biosensor when an alcohol sample was added. The layer of PEI enhanced the interaction between AOx enzyme and MWCNTs, facilitating electron transfer from the enzyme to the electrode surface.
Response of the alcohol biosensor was found to be optimal at pH 7.5. The biosensor retained about 90 per cent of the original response, even after 4 weeks when stored at 4°C. This sensor could selectively detect minute traces of alcohol even in the presence of interfering chemical agents such as ascorbic acid, lactic acid, glucose, urea and uric acid.
"This biosensor could be used without any significant interference from substances present in body fluids, making it suitable for determining alcohol content in human serum samples," says lead researcher Pranab Goswami.