Nanopore sensor identifies seven cyanobacterial toxins in lake water

A tiny biological channel could make it faster to monitor toxins produced by cyanobacteria. EPFL researchers used an aerolysin nanopore to identify seven common microcystin variants, both individually and in mixtures.

Microcystins can occur during cyanobacterial blooms and pose risks to drinking and recreational water. Their structure differs from one variant to another. This diversity makes it difficult to obtain a rapid and comprehensive measurement with a single instrument.

The sensor uses a protein pore carrying an ionic current. When a molecule passes through the channel, it briefly changes the electrical signal. The shape of the blockage and the time spent inside provide a fingerprint that allows individual microcystins to be distinguished at single-molecule level.

From samples to on-site monitoring

In the study, released as a scientific preprint, the system reached picomolar sensitivity and detected microcystins below World Health Organization intervention thresholds. Researchers also tested it on different natural lake-water samples, including water from lakes Lugano and Geneva.

This does not mean that a ready-to-use device is already available at the lakeside. The EPFL project aims to produce portable, real-time measurements without a separate calibration standard for every substance. Further validation, automation and field testing during blooms will be needed before the laboratory demonstration becomes an operational tool.

Existing methods remain essential, but they may require specialist staff and laboratory analysis or capture only part of the range of compounds. A sensor able to flag several variants quickly could help water managers decide when detailed testing is needed and where sampling should be concentrated.

The research therefore opens a practical possibility rather than immediately replacing current procedures. Its value will depend on whether the technology remains accurate and reliable outside the laboratory, in natural water containing many other molecules.