“We are working on construction of different biosensors for different pathogens,” say Dr. Ashok Kumar and Swati Singh (left). | Photo Credit: Special arrangementThis beats conventional methods
An ultrasensitive DNA sensor that can detect S. pyogenes, a bacterium which causes a wide range of diseases in about 30 minutes has been developed. The DNA chip is highly specific device for S. pyogenes. The conventional method of identification takes 18-24 hours and the basic culture test does not specifically help distinguish S. pyogenes.
Early detection
From mild skin and throat infections to life-threatening toxic shock syndrome, S. pyogenes infections affect 700 million people every year. If not treated during early stages of the infection, S. pyogenes can even lead to rheumatic heart disease (heart valves damage).
The sensor was developed by scientists from CSIR-Institute of Genomics and Integrative Biology (CSIR-IGIB) and National Centre for Disease Control (NCDC) Delhi, and the results were published in the International Journal of Biological Macromolecules.
The DNA chip based sensor consists of a carbon electrode embedded with gold nanoparticles. By means of a bioinformatics study, the researchers were able to design probes which are specific for S. pyogenes.
The working electrode surface of the device is attached with several small-sized, single-stranded DNA probe specific to the pathogen. When patients’ DNA, isolated from throat swabs, are placed on the surface, they bind to the complementary single-stranded DNA on the device and an electrochemical change is seen. This is measured using a differential pulse voltammetry.
Identification of pathogen
For confirmation, traditional culture test was used and the results matched with the DNA sensor. “The sensor is highly sensitive and could detect even 60-65 bacteria in a 6 microlitre sample. It could identify the pathogen even at very low concentrations of DNA. We were able to get a peak with a concentration of even 0.001nanogram per 6 microlitre,” explains Swati Singh from IGIB and the first author of the paper.
Stable sensor
The sensor was found to be stable for 12 months with only 10% loss in initial current peak on storage at 4 degree C. “We are working on construction of different biosensors for different pathogens. Early and quick diagnosis can help in preventing the diseases and seek medical treatment at the early stage of infection,” adds Dr. Ashok Kumar, Chief Scientist/Professor (AcSIR) at IGIB and corresponding author of the paper.
