TARRAGONA – Scientists from Rovira i Virgili University (URV) in Tarragona have come up with a novel biosensor that can instantly detect Salmonella typhi, the bacteria that causes typhoid fever.

The technique uses carbon nanotubes and synthetic DNA fragments that activate an electric signal when they link up with the pathogen.

“We have developed a new biosensor that can detect extremely low concentrations of bacteria immediately, easily and reliably”, F. Xavier Rius, lead author of the study and a professor in the Chemometrics, Qualimetrics and Nanosensors research group in the Analytical Chemistry and Organic Chemistry Department of the URV, told SINC.

The new biosensor functions using a method, which involves carbon nanotubes with inbuilt aptamers providing electrochemical readings.

According to the researchers, the aptamers are small fragments of artificial DNA or RNA designed to attach themselves specifically to a particular molecule, cell or micro organism, in this case Salmonella.

If the bacteria are not present, the aptamers remain on the walls of the carbon nanotubes.

However, if they detect bacteria, they become activated and stick to it, and the carbon nanotubes generate an electric signal that is picked up by a simple potentiometer connected to the biosensor.

“The presence of the bacteria sparks a change in the interaction between the aptamers and the nanotubes, which takes place in a few seconds and creates an increase in the voltage of the electrode”, said Ruis, who led the research along with researcher Jordi Riu.

“This technique means small quantities of micro organisms can be detected simply and practically in real time, just the same as measuring the pH of water”, Ruis added.

The study appears in the scientific journal Angewandte Chemie International Edition