Low-cost, portable kit to detect pathogens in drinking water
doi:10.1038/nindia.2019.76 Published online 12 June 2019
A nanoparticles-based kit can detect harmful pathogens in drinking water, fruit juice and different water samples, a study reveals1. This kit is potentially useful for on-site testing of contaminated water and liquid samples.
Existing techniques for detecting pathogens in drinking water are expensive and complex. To devise a simple and cheap method, scientists from the CSIR-Institute of Microbial Technology and Panjab University in Chandigarh, India developed the kit using an assay. They prepared the assay using modified silver nanoparticles, urease, urea and phenol red, a pH indicator that changes colour according to the pH level of a solution.
The researchers, led by Vijayender Bhalla, tested the efficacy of the assay by exposing it to a bacteria-contaminated water sample. In the sample, the positively charged nanoparticles bound to the negatively charged bacterial cell surface, leaving free urease.
When urea and phenol red were added to such samples, urease converted the urea into ammonia and carbon dioxide, increasing its pH level. This increase in pH level displayed a visible colour change from yellow to pink.
When there were no bacteria in the water sample, the nanoparticles bound to the urease, inhibiting its activity and keeping the solution yellow.
The researchers then coated the nanoparticles with antibodies specific to Salmonella typhimurium, which infects the stomach and the intestines. The antibody-coated nanoparticles easily detected this bacterium in tap water, showing its potential for detecting pathogens in real samples.
The method, which also detected bacteria in contaminated apple juice and lake water, was used to develop a low-cost, portable test kit, says Saloni Kakkar, one of the researchers.
1. Singh, P. et al. Rapid and sensitive colorimetric detection of pathogens based on silver–urease interactions. Chem. Commun.55, 4765 (2019)