At present, harmful pathogens in food are mostly only discovered when people get sick. Earlier detection - preferably before food reaches consumers - could prevent many cases of foodborne illness and save the cost and effort involved in food recalls. Now, a team working toward solving this problem has developed a portable biosensor based on "nanoflowers" that detects harmful bacteria.

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The nanoflower biosensor detects tiny chemical signals emitted by bacteria and amplifies them so they can be picked up easily with a simple handheld pH meter.

The new technology is the work of researchers at Washington State University (WSU) in Pullman, who describe how they developed and tested it in a paper published in the journal Small.

Even tiny amounts of harmful bacteria and other microbes can give rise to serious health risks, but the available sensor technology is unable to detect them easily and quickly in small quantities.

The key challenge in solving this problem is finding a way to detect the faint chemical signals that the harmful microbes emit at the molecular level.

If these pathogen signals can be detected, then it is a matter of amplifying them so that more conventional equipment can translate them into alert messages.

In their paper, senior author Yuehe Lin, a professor in WSU's School of Mechanical and Materials Engineering, and colleagues describe how they developed a "nanoflower" biosensor that is able to detect and amplify signals from Escherichia coli O157:H7, a food pathogen that causes severe diarrhea and kidney damage in people.

The biosensor uses a flower-like nanoparticle made from organic and inorganic components. Its key feature is the ability to maintain a large amount of enzyme activity for detecting antigens in a sample.

An antigen is any part of a microbe that causes a reaction in the body.

'As simple as a pregnancy test or glucose meter'

Smaller than a speck of dust, the nanoflower biosensor comprises a group of molecules arranged like the petals of a flower. The arrangement provides a large surface area for immobilizing the highly active enzymes that are needed to detect the bacteria at low levels.

The team showed that the nanoflower biosensor recognized and amplified signals from E. coli O157:H7 so they could be picked up easily with a simple handheld pH meter or pH indicator paper strip.

The researchers have filed a patent for the technology and are developing versions that can detect other food pathogens such as Salmonella.

According to the Centers for Disease Control and Prevention (CDC), around 1 in 6 Americans - about 48 million people - get sick, 128,000 are hospitalized, and 3,000 die of foodborne diseases every year.

There are 31 known foodborne pathogens, eight of which account for the vast majority of illnesses, hospitalizations, and deaths.

As well as E. coli and Salmonella, these include Norovirus, Clostridium perfringens, Campylobacter spp., Staphylococcus aureus, Toxoplasma gondii, and Listeria monocytogenes.

"We want to take these nanoflowers and create a simple-to-use, handheld device that anyone can use anywhere. It'll be as simple as using a pregnancy test strip or a glucose meter."

Prof. Yuehe Lin

Learn how chemists developed a tiny, cheap nanosensor that sniffs out rotten meat.