Waiting is the hardest part. Especially in the case of testing for water or food contamination, which can take days or even a week in some cases for the results, leaving the possibility that people have been unknowingly exposed.
To address this issue, Michigan State University researchers have developed two innovative methods to test for bacteria and viruses in food and water that reduces this time from days to hours, offering real-time results in the field.
“We know it’s a problem,” said Evangelyn Alocilja, professor in the Department of Biosystems and Agricultural Engineering in the College of Engineering and the College of Agriculture and Natural Resources. “The beach is closed today, but what about the people who went swimming before the test results came back?”
Alocilja and her team have developed glycan-coated magnetic nanoparticles that are thinner than the width of a human hair to remove and identify microbial contaminants from food and water. Glycan is a sugar that attaches to the proteins that live on the surface of viruses and bacteria. Once the nanoparticles stick to the bacteria, a magnet is used to separate the particles and bacteria from the sample. Then, the contaminant is easily removed.
Once the contaminant is removed, the next step is identifying what kind of bacteria it is by using a biological sensor or biosensor that can detect living things. The biosensor uses gold nanoparticles that embed themselves in the DNA of the bacteria if the specific gene they are looking for is present. If the gold nanoparticles appear red, the target gene is present. If the gold nanoparticles change from red to blue, that means the nanoparticles have formed a clump and the target gene is absent.
This testing method takes about 40 minutes, meaning that the user can identify bacteria in the water in two to four hours instead of one to two days. For example, salmonella, campylobacter and E. coli are transmitted through contaminated water and are the most common causes of foodborne illnesses in the U.S. and worldwide. Alocilja’s nanoparticle-based biosensor technology can isolate these foodborne and waterborne bacteria in less than 30 minutes, extract the DNA in 20 minutes and detect the target gene in 40 minutes, saving time and money.
Only a small amount of nanoparticles are needed to test the sample thanks to the glycan-coated magnetic nanoparticle technology. For example, to test one liter of water or 25 grams of food, only one milliliter of glycan-coated magnetic nanoparticles is needed. Alocilja hopes these inexpensive technologies — costing 10 to 50 cents per test for the glycan-coated magnetic nanoparticles and less than $2 per test for the gold nanoparticle method — will one day be used around the world to test water quality and be used to improve food safety
“I am passionate about helping resource-limited populations who need help the most because they are most vulnerable to contaminated water, food and the environment,” said Alocilja. “Oftentimes, these communities lack medical infrastructures and have unreliable power sources. The nanoparticle-based biosensor meets the need because it utilizes a simple magnet, requires minimal power, is easy to operate and does not necessitate cold storage.”
Recently, Alocilja and her team have been testing this integrated nanoparticle-based sample-to-result biosensor technology in the field to detect infectious and antimicrobial-resistant organisms, which can be used in health clinics and emergency rooms.
“We don’t want sick people to wait long on diagnostic results before they can be treated,” said Alocilja. “We want them to be able to receive treatment as soon as possible, because early diagnosis and treatment are critical to early recovery and survival.”
This research was published in the journal Food Safety and Quality.
