New Nanotechnology Platform Developed for the Rapid Detection of Foodborne Viruses
By Suresh Neethirajan, Ph.D., P.E.
At the University of Guelph, our bionano lab, working in collaboration with Korean and Japanese scientists, has developed a nanotechnology-based platform for rapidly detecting foodborne viruses that is quicker, easier, and more accurate than current testing methods. This new sensing mechanism can detect very faint traces of foodborne viruses that can help prevent epidemics and further transmission.
Foodborne viruses can cause major health problems. Sufferers can end up with gastroenteritis, an inflammation of the gastrointestinal tract that involves the stomach and small intestine and can cause liver damage with hepatitis strains.
What Are Foodborne Viruses?
Foodborne viruses are not really living organisms, as they do not have a metabolic apparatus. They are inert, incapable of reproducing, and must induce living cells to infect the host. They are shed in particles; one bout of vomiting from gastroenteritis can shed many particles, which can lead to large outbreaks in a short time. Viruses are persistent and can even survive some food production processes used to control bacteria in food.
How Are These Viruses Contracted?
Human infection can occur following consumption of contaminated food, person-to-person body contact, or release of aerosols from vomiting. Food may be contaminated by infected food handlers or by contact with water contaminated by treated or untreated sewage. Outbreaks of viral foodborne illness have also been associated with the consumption of shellfish harvested from polluted water. Signs and symptoms of infection in humans include diarrhea, vomiting, and abdominal pain. Fever, lack of energy, and dehydration can occur. Hepatitis symptoms can include jaundice, muscle weakness, and bad headaches.
Types of Foodborne Viruses
Norovirus: Norovirus is contracted orally through contaminated water or food. The infection can last anywhere from 24 hours to 6 days, and symptoms include nausea, vomiting, and diarrhea. Noroviruses are often the cause of epidemic outbreaks. Water from wells, swimming pools, recreational lakes, or water stored on cruise liners is usually the source of these outbreaks. Infection from food is normally associated with shellfish or salads that have been washed in contaminated water. If it is picked up from other foods, it is usually due to the food handler’s contaminating the food with the virus.
Rotavirus: Rotavirus A is endemic worldwide, causing approximately 80 percent of rotavirus gastroenteritis in humans, particularly through waterborne infection. Rotavirus gastroenteritis is a self-limiting, mild to severe disease that includes symptoms of vomiting, watery diarrhea, and low-grade fever. It can be deadly in children and the elderly, as it can cause rapid dehydration.
Hepatitis A: Hepatitis A is a liver infection characterized by symptoms similar to influenza’s such as fever, malaise, nausea, joint pain, and abdominal discomfort, followed several days later by jaundice. Sufferers normally recover within 2 months. The illness is usually more severe the older the person is. Foods can be contaminated with the virus through contact with raw sewage, as is the case with shellfish, or through contact with contaminated water; transmission is then primarily via the fecal-oral route. Hepatitis A virus replicates exclusively in liver cells, is excreted in bile, and shed in the feces of infected people.
Hepatitis E: This strain also attacks the liver. Symptoms include jaundice, enlarged tender liver, abdominal pain, arthralgia, vomiting, and fever. Chronic hepatitis has been reported in organ transplant recipients and in patients with active HIV infections.
From Which Foods Can We Become Infected with a Virus?
As viruses are passed through the feces or orally, contamination can occur at any point in cultivation, harvesting, processing, distribution, or processing/preparation of food. The foods most commonly associated with viruses are the following:
• Shellfish, including oysters, cockles, and mussels
• Salads and salad dressings
• Cold cuts
• Green onions
• Sun-dried tomatoes
• Drinking water
• Fruit juices
• Milk and milk products
• Pig-liver sausage
• Pork livers
• Cake icings
Current Detection Methods
Detecting foodborne viruses is quite a complex procedure, as viruses can’t be easily cultured in a laboratory. Molecular techniques are used, such as reverse transcription polymerase chain reaction, also known as RT-PCR. Before detection, the viruses must be extracted and concentrated from the food matrix. These processing steps result in the loss of viruses and thereby low recovery; time and experience are required to carry out the tests accurately.
How Was the Study Carried Out?
We invented a method to fabricate gold nanoparticle films using different substrates, including glass, 96-well polystyrene plates, and polydimethylsiloxane, which belongs to a group of compounds often referred to as silicone. Gold nanoparticles are utilized in research because they can act as a catalyst to help reactions when other molecules are applied to them. A combination of sodium formate and chloroauric acid was used to prepare the gold nanoparticle films. When these particles were then put into contact with foodborne viruses such as norovirus, influenza, rotavirus, and different strains of the hepatitis virus, they were 500 times more sensitive than commercial immunochromatography testing kits that are currently used to detect foodborne viruses. The amount of virus needed for detection was lower as well. In fact, it was 116 times lower than the amount of virus needed for its detection using conventional testing kits.
The film fabrications were treated under different conditions and with a variety of techniques to get specific results, ranging from color to size changes of the particles. We experimented with different formulations until the exact formula was identified. Plasma and synthetic particles were used as well as gold nanoparticles to ensure that all areas were explored during the study. Also, different concentrations of the viruses were used to ensure that the lowest amount of virus could be detected and that the films were more sensitive than the testing now available.
Utilizing the Findings
Currently, the tests used to detect these viruses are not very effective and can’t be carried out in real time; it is possible that a foodborne virus can go undetected. This means that these film fabrications can be used to improve upon what is now available. This new sensing mechanism can aid the detection of viruses from even complex media with varying substrates and properties. It is now possible, thanks to these film fabrications, for scientists to invent a simple, highly sensitive, and low-cost diagnostic technique for foodborne virus detection without the need for any complex equipment or special training on how to use it.
This breakthroughis very good news for the consumer. With the development of a new diagnostic technique as a result of these findings, viruses such as influenza that can occur in chickens and pigs can be found in the live animal before it reaches the food supply. It’s also possible that if the meat reaches the food chain and is infected because either the animal was carrying the virus or a food handler had a foodborne infection and contaminated the meat, the infection can be detected before the meat is consumed. It is also possible that foodborne viruses can be diagnosed more quickly in humans, ensuring that the necessary treatment is given promptly; making the sufferer aware that they have a virus means that they might take extra care around food and with personal hygiene, which could help prevent epidemics.
It is imperative that studies like these are carried out to continually improve the technology available. Different strains of viruses are detected quite frequently; for the general public to remain as safe as possible, such research is an important part of maintaining that safety.
Suresh Neethirajan, Ph.D., P.E., is the program leader of the bionano lab in the School of Engineering at the University of Guelph in Ontario, Canada.