Researchers have come up with a paper-based biosensor as an inexpensive but innovative tool in detecting water toxicity.
Detecting contaminants is crucial in analyzing and controlling water quality, which has become necessary in the urban setting. A number of chemical analysis techniques are in place for evaluating samples but most of them are geared toward those with multiple contaminants. The new biosensor then is ideal because it can check for contaminants singularly depending on the biological element to be used.
"The innovation provided by our sensor is based on the use of absorbent paper matrices with entrapped bacteria with the aim of conducting colorimetric measures of toxicity," said Ferran Pujol, one of the authors of the study published in the journal Analytica Chimica Acta.
For the study, the researchers used E. coli cells as model bacteria. Following mechanisms similar to litmus paper tests for pH, the detection technique they developed uses samples added to matrices combined with ferrocyanide, a coloring agent. When breathed in by microorganisms, ferrocynanide changes from yellow to transparent.
Depending on how intense bacterial cell metabolism is, the paper sensor will change color inversely proportional to how toxic a sample is. This means that the brighter the color change, the less contaminated a water sample is. As this change is readily observable with the naked eye, there will be no need for complicated equipment. This not only simplifies the process but also makes it highly affordable as well, making it ideal for use in developing countries or other areas with economic restrictions.
Called a bioassay, the paper sensor detects all contaminants, like hydrocarbons or heavy metals, toxic to the sample bacteria after 15 to 30 minutes of exposure. Depending on whatever water source needs to be tested, the bioassay can be used on both urban wastewater and natural water.
Researchers from the Autonomous University of Barcelona, the National Centre for Microelectronics and the UPC Centre for Research and Innovation in Toxicology collaborated on developing the bioassay, which they have applied a patent for.
Problems With Contaminated Water
In 2014, complaints about contaminated water began in Flint, Michigan. Turns out, when the city switched to Flint River as a water source, corrosive river water scraped lead off the city's old pipes, which found its way into homes. It was only in March 2016 that Flint enacted a program to eliminate all its lead water lines, taking the first step toward bringing fresh water again into the city.
Photo: U.S. Army Corps of Engineers | Flickr