September 13, 2010 — Ottawa, Ontario
A decade ago, in May 2000, Canada experienced its worst-ever E. coli outbreak after this bacteria entered the water supply in Walkerton, Ontario, killing seven people and making more than 2,300 others sick. More recently, 22 Canadians died and another 57 became seriously ill after consuming luncheon meat contaminated with the bacterium, Listeria monocytogenes. This resulted in a massive recall by Maple Leaf Foods Inc. of its packaged meat products. Detecting deadly pathogens like E. coli and Listeria quickly and accurately could prevent future public health crises, which is the idea behind new sensing technologies being developed at NRC.
As part of the NRC Genomics and Health Initiative, a multidisciplinary scientific team involving several NRC facilities has undertaken a three-year, $17-million project to design biochips to investigate the molecular processes underlying critical infectious diseases. The goal is to create small and efficient point-of-care diagnostic devices integrated onto a single silicon chip. These biochips, in turn, could rapidly detect specific pathogenic markers based on their "genomic signature" in order to diagnose infectious agents that threaten water and food safety, or are responsible for hospital-acquired infections.
So far, the NRC team has configured photonic wires to produce sensitive probes that can measure the molecular properties of biochemical mixtures. Rather than relying on chemicals used in the time-consuming process of fluorescent labelling, NRC's photonic-wire evanescent field (PWEF) sensor-array technology [see: "Photonic wires to detect pathogens"] sends light along the interface between the silicon and the liquid sample that sits atop the sensor. If the light encounters a target molecule, such as a piece of DNA or a "marker" molecule belonging to a protein unique to certain bacteria, the passage of the light is altered. This minute change is measured by the sensor's photodetector, which the system interprets as the presence of the target molecule.
NRC researchers are also designing a complementary biochip that uses electrons, instead of light, to detect the presence of pathogens. Ultimately, the PWEF sensor-array and biochip technology could be integrated into a single device. That device would be capable of conducting multiple measurements simultaneously and would provide detailed genotyping of a bacterial strain or other pathogen present in a sample, says Dr. John Pezacki, who serves as scientific leader of the NRC biochips project.
NRC's rapid biosensing technology could be used both in labs that lack efficient and cost-effective diagnostic tools, and for conducting tests in the field. To facilitate field tests, the biochips team is building a portable demonstration system that could be transported to a site for testing.
"It could be used in a food processing plant to take swabs from equipment and check for bacteria, or at a water source where a technician could collect a sample and see whether any pathogens are present," explains Eddy Guzzo, who serves as project manager of the biochips initiative. "There could also be multiple applications in a hospital setting, where the system could be used to test the blood of patients or to take swabs of operating rooms to see if any potentially harmful bacteria are living on any surfaces."
Dr. Pezacki says that if a company commercializes the biosensor alone or in partnership with NRC, the technology platform is broad enough for the biomedical community to adapt it for other applications, such as testing samples for pathogens. "We want to enhance its capabilities in monitoring and surveillance, in partnership with other government agencies."
To that end, NRC is collaborating with the Public Health Agency of Canada (PHAC) to use the biochips technology to identify pathogenic strains of E. coli as part of PHAC's efforts to prevent pandemics and outbreaks of diseases.
