The "lab-on-a-chip." The numbered reservoirs (2-8) hold the various chemical agents used in the test. Altering the orientation of the chip within the centrifuge controls the flow of each agent through the connecting channels and into the test strip (1).
We often hear that "speed kills"—but when it comes to food safety, the opposite is often true. As Dr. Burton Blais, head of the Research and Development Section at the Canadian Food Inspection Agency (CFIA) labs in Ottawa, explains, "The sooner we can identify a potentially dangerous contaminant in a food product, the sooner we can identify the source, warn the public and take other steps to contain the contamination event, such as issuing a recall order."
Together with a team led by Dr. Teodor Veres at the National Research Council of Canada (NRC), Dr. Blais and his team at the CFIA have developed a device that can identify one of the most dangerous bacteria that can enter our food supply—E. coli O157: H7—in as little as 20 minutes.
The new method is a dramatic improvement over the current test which takes a full day to complete once a sample has been prepared for testing. The process developed by the two teams offers another significant advantage, in that it can easily be adapted to detect other bacterial or viral contaminants, and even allergens in food products.
Faster—and more cost-effective
Using a novel combination of microfluidics and automation, the new testing process is also less expensive. Dr. Veres, leader of the Functional Nanomaterials Group in the NRC's Life Sciences Division, explains that, "The existing test involves a number of steps that require a lot of hands-on work by the technician, so it's very labour-intensive. Our device eliminates most of that manual labour. As well, microfluidics means we're using microlitres of chemicals instead of millilitres, so there's a significant reduction in the cost of the inputs needed for the test."
How it works
The existing test uses a technique called Cloth-based Hybridization Array System, or CHAS, in which a technician bathes a specially treated strip of polyester cloth with a series of compounds to amplify and detect the DNA of the bacteria. The automated microfluidics version of CHAS—or mCHAS—is based on two key elements.
Two chips are shown mounted in the centrifuge. Chips can be stacked to allow as many as eight samples to be tested simultaneously.
First is a plastic "chip," about 10 centimetres long and five centimetres wide. The chip has a number of small indentations that act as reservoirs for the various fluids used in the test. A series of tiny channels carry the liquids to and from the bit of cloth in the centre of the chip.
The second element is a computer-controlled centrifuge that not only spins the chip, but also allows the orientation of the chip within the centrifuge to be changed at specific times. By altering the direction of the centrifugal force applied to the chip, the device ensures the various liquids flow from their reservoirs to the polyester cloth in the centre of the chip at the right time and in the correct order—enabling a precision and consistency that is not possible with a manual test. What's more, several chips can be stacked on top of each other, allowing as many as eight samples to be tested at the same time.
Building on progress
Both Dr. Veres and Dr. Blais, are quick to point out that their achievement would not have been possible without the work of colleagues who perfected the genomics-based CHAS test for E. coli in the first place.
"The CHAS test was itself a substantial leap forward," says Dr. Blais. "In the past, using traditional methods, it would take several days to make a positive identification of E. coli—CHAS cut that down to just one day."
Innovative partnerships, innovative achievements
Like the project led by Drs. Blais and Veres, the research that led to the development of the CHAS test was funded by the Government of Canada's Genomics Research and Development Initiative (GRDI), as part of the GRDI Food and Water Safety (FWS) project. The FWS project engaged six federal, science-based departments in a collaborative effort to apply the science of genomics to address key food and water safety issues.
While there's no question that funding for this type of research is essential, Dr. Veres says it's not just about the money. "The GRDI enabled researchers in different departments to reach out to one another and combine their expertise," says Dr. Veres. "For example, biologist Nathalie Corneau and her team at Health Canada played a key part in developing the existing test, and Dr. Blais and I have also relied on her expertise to get us where we are today. I don't think that kind of collaboration would have been possible without the GRDI."
Prior to testing, chemical "probes" to detect the genetic signature of E. coli O157:H7 are added to specific sections of a strip of polyester cloth (a). After the test (b), the test strip reveals the presence of the bacteria in the sample.
Benefits beyond food safety
The new testing device has been patented and, based on the interest the technology has generated in Canada and other countries, a Canadian company has acquired a license to manufacture and bring the device to the commercial market.