New test detects water contamination in minutes
The system has been compared to a pregnancy test, because it only takes one drop of water and a few minutes to produce a positive or negative result. According to the researchers, the tests are also extremely inexpensive to make.
The experts tested their technology in Paradise, California. Toxins had corrupted the water supply in Paradise after the Camp Fire, the deadliest and most destructive wildfire in California history.
The new platform is powered by synthetic biology, and can be continuously updated to detect additional types of pollutants. If the test detects a specific contaminant level that exceeds the EPA’s standards, it glows green.
Study lead author Julius Lucks is a professor of Chemical and Biological Engineering in Northwestern’s McCormick School of Engineering and a member of the Center for Synthetic Biology.
“Current water tests rely on a centralized laboratory that contains really expensive equipment and requires expertise to operate,” said Professor Lucks. “Sending in a sample can cost up to $150 and take several weeks to get results.”
“We’re offering a technology that enables anyone to directly test their own water and know if they have contamination within minutes. It’s so simple to use that we can put it into the hands of the people who need it most.”
A major obstacle for ensuring the safety of drinking water is that people cannot usually see or taste contaminants.
“Nature has already solved this problem,” said study co-first author Khalid Alam. “Biology has spent over three billion years evolving an elegant solution to detect contaminants.”
According to Professor Luck’s, the team found that bacteria naturally “taste” things in the water.
“They do so with little molecular-level ‘taste buds.’ Cell-free synthetic biology allows us to take those little molecular taste buds out and put them into a test tube. We can then ‘re-wire’ them up to produce a visual signal. It glows to let the user quickly and easily see if there’s a contaminant in their water,” explained Professor Lucks.
The “taste buds” are freeze-dried and placed in test tubes. Adding a drop of water to the tube and flicking it triggers a chemical reaction that creates a green glow in the presence of a contaminant.
“The magic is in the tubes,” said Professor Lucks. “We compose everything and freeze dry it – the same process as making astronaut ice cream.”
The testing platform – RNA output sensors activated by ligand induction – is nicknamed ROSALIND in honor of the famous chemist Rosalind Franklin.
The project was also inspired by Professor Lucks’ wife, Northwestern anthropologist Sera Young, who studies global food and water security.
“Sera researches how poor water quality impacts people’s daily lives,” said Professor Lucks. “People tend to go to the most convenient sources to get water. But if they knew that water was contaminated, they might choose to travel farther to find safer water. We want everyone to have the tools they need in order to make informed decisions.”
Upon testing the new system in Paradise, California, the team found that ROSALIND successfully identified the presence of elevated toxic metals in the water supply. The test provided much faster and less expensive results when compared to gold-standard water tests.
“Laboratory testing doesn’t scale,” said Alam. “It shouldn’t take days to get an answer to the simple question: ‘Is my water safe to drink?'”
“To ensure access to safe and clean drinking water, we need technologies that will allow easy monitoring of water quality,” said Professor Lucks. “With a simple, easy-to-use, handheld device like ROSALIND, you can test the water in your home or out in the field – where you would want to use it most.”
The study is published in the journal Nature Biotechnology.