Phone-connected device detects bacterial toxins in water

Potentially fatal to both animals and humans, blue-green algae blooms occur when overly-abundant cyanobacteria in the water produce harmful substances known as cyanotoxins. The sooner those toxins are detected, the better – which is where a new smartphone-connected device comes into the picture.

Ordinarily, when officials are checking for the early signs of algae blooms in lakes or rivers, they take water samples that have to be sent off to a lab. By the time those samples have been analyzed, the bloom may have already reached the stage where the public should have been alerted.

Led by Asst. Prof. Qingshan Wei, scientists at North Carolina State University set out to make earlier warnings possible, producing what is being called the world's first portable cyanotoxin-detection system. Users simply place a drop of water on a chip, which is then inserted into a reader device that is in turn mounted to a smartphone.

The chip is preloaded with single-stranded DNA (ssDNA) dyes combined with molecules known as aptamers. These bind with any target molecules that may be present in a sample, causing them to fluoresce. As a result, within just five minutes, an app on the phone is able to alert users to the presence and levels of four common types of cyanotoxins – anatoxin-a, cylindrospermopsin, nodularin and microcystin-LR.

"Our technology is capable of detecting these toxins at the levels EPA [Environmental Protection Agency] laid out in its water quality criteria," says Wei. "However, it's important to note that our technology is not yet capable of detecting these cyanotoxins at levels as low as the World Health Organization's drinking water limit. So, while this is a useful environmental monitoring tool, and can be used to assess recreational water quality, it is not yet viable for assessing drinking water safety."

The researchers are now working on boosting the system's sensitivity, so that it can be used to determine if water is safe to drink. They also state that if produced at a commercial scale, the reader device should be relatively inexpensive – it currently costs less than US$70 to manufacture, with the chips coming in at under a dollar each.

A paper on the research was recently published in the journal Analytical Chemistry.

Source: North Carolina State Universit