When swimmers splash into Lake Geneva on a hot summer day, they probably do not think about invisible threats lurking beneath the surface. But during certain conditions, tiny organisms called cyanobacteria can bloom rapidly, releasing poisons called microcystins that threaten human health, drinking water, and aquatic life. Now, scientists in Switzerland have built an incredibly small sensor that can detect these toxins faster and more simply than existing methods.
Researchers at EPFL, a university in Lausanne, Switzerland, developed a sensor about 10 billion times smaller than a soccer ball. It uses a natural protein called aeroblysin that forms a microscopic channel, or nanopore, through a thin membrane. When electrical current flows through this teeny tunnel and a toxin molecule passes through, it briefly blocks the current. Different toxins create different blockage patterns, like fingerprints.
In laboratory tests, the device distinguished among seven different microcystin variants at once. That matters because while these toxins share similar structures, their health effects can differ. The team, led by scientists Alissa Agerova and Juan Francisco Bada Juarez, then took their sensor to real lakes.
They collected water from Lake Geneva, where they successfully separated two closely related microcystins that had been added at concentrations typical of strong blooms. The lake water did not confuse the sensor. More impressive still, during an actual cyanobacteria bloom in Lake Lugano, the device identified and measured one of the most studied toxins, called MC-LR, at 12.7 nanomolar. Traditional laboratory equipment running the same sample came up with 13.1 nanomolar — nearly identical results.
The nanopore sensor also proved remarkably sensitive. It detected MC-LR at concentrations as low as 25 picomolar, which is 40 times lower than the World Health Organization's safety guideline of 1 nanomolar for lifetime drinking water exposure. This means the device could potentially catch dangerous toxin levels long before they become a health concern.
"The technology is not yet ready to take into the field," admits researcher Tamar Kohn, noting that current tests require filtering water and adding salt. But because nanopores are compact and produce results instantly, the sensor could eventually be built into portable devices for real-time water testing at beaches, lakes, or water treatment plants. The same approach could also be adapted to detect other harmful substances in water.
Agerova is now working to launch a company called CYnANO to develop and sell the technology. If successful, it could give communities an affordable way to monitor their water without waiting days or weeks for laboratory results.