Scientists from Rovira i Virgili University (URV) in Tarragona, Spain are reporting the development of a device capable of rapidly detecting the presence of bacteria in a sample, even at very low concentration of organisms. The system uses carbon nanotubes coupled with aptamers–in this case, artificial DNA and RNA strings that stick to bacteria–to be able to discern a single Salmonella cell within a five-milliliter sample.
This new biosensor functions using a method, described this month in the scientific journal Angewandte Chemie International Edition, which involves carbon nanotubes with inbuilt aptamers providing electrochemical readings.
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", says Rius.
Traditional methods for identifying and measuring micro organisms require one or two days’ analysis. "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", adds the researcher.
This study is part of the international research being carried out to find the most effective and fast ways of detecting all kinds of pathogens. The new biosensor makes it possible to identify a single cell of Salmonella in a five-millilitre sample and can successfully make quantitative measurements of up to 1,000 bacteria per millilitre.
Press release: New biosensor detectect bacteria instantaneously…
Abstract in Angewandte Chemie International Edition: Immediate Detection of Living Bacteria at Ultralow Concentrations Using a Carbon Nanotube Based Potentiometric Aptasensor