Typhoid bacteria sensor
doi:10.1038/nindia.2012.96 Published online 30 June 2012
Using a modified gold chip, researchers have designed a new kind of biosensor which could detect traces of Salmonella typhi, a bacterium responsible for enteric fever in humans. This surface plasmon resonance (SPR) biosensor will be useful in tracking down S. typhi in biological and environmental samples in laboratories and hospitals.
Existing techniques to detect Salmonella consume much time. To find out a faster technique, the researchers prepared a 4-mercaptobenzoic acid (4-MBA)-modified gold chip. Separately, they prepared recombinant flagellin (r-fla – a bacterial protein) antigen using recombinant DNA technology and developed specific antibodies to r-fla antigen.
They attached the antigen on 4-MBA modified gold chip. The gold chip shows surface plasmon response in terms of SPR angle change, an electronic property of gold metal which helps detect adsorbed materials onto metallic surface. The researchers exposed this antigen-attached modified gold chip to varying concentrations of r-fla antigen specific antibodies in phosphate buffer solution and the interactions were monitored through a personal computer with data acquisition software.
The detection time for antibodies of r-fla S. typhi by SPR was found to be less than 10 minutes. Similar studies using normal human serum and typhoid patient serum showed that using the biosensor, it was possible to distinguish easily between the patient serum and normal human serum by SPR in less than 10 minutes.
The authors of this research are from: Defence Research and Development Establishment, DRDO, Jhansi Road, and ITM Universe, Gwalior, India.