Researchers at the Indian Institute of Technology, Guwahati have developed a low-cost, hand-held device that can detect minute traces of bacteria in biological and environmental samples1. The device rapidly detects bacteria without the need for a cell culture. This makes it potentially promising for detection of bacteria that cause water-borne diseases or for the diagnosis of critical illnesses such as meningitis.
Bacteria are divided into two broad categories (gram positive such as Staphylococcus pneumoniae and gram negative such as Escherichia coli ), depending on their cell wall composition.
The device, made of glass and a plastic substrate, identifies the microbes by using this difference in the flow of electrons in the cell walls of various bacteria. It detects the surface charges on the cell walls with the help of an organic field-effect transistor to differentiate between gram positive and negative strains. The researchers, led by Siddhartha Sankar Ghosh and Parameswar K. Iyer, designed the device employing this property of bacteria.
The charges on the surface of a bacterium induce a current in the transistor which can be easily read. Each bacterium strain generates unique electrical signal, making it possible to identify it.
1. Dey, A. et al. Rapid and label-free bacteria detection using a hybrid tri-layer dielectric integrated n-type organic field effect transistor. J. Mater. Chem. A. (2019) doi: 10.1039/C9TA06359E