Pig, pig, pig, pig, pipette, pig.
Uppsala, Sweden-based Biacore has created an array-based prototype system, Foodsense that has promise for making high-throughput field testing for food contaminants a possibility.
The company recently completed a long-term test of a benchtop prototype of its technology in a Northern Ireland abattoir. Results of the study, “On-line detection of sulfamethazine and sulfadiazine in porcine bile using a multi-channel high-throughput SPR biosensor,” by Chen Situ, et al, were published in Analytical Chimica Acta (Vol. 473, Issues 1-2 Nov. 25, 2002)
Food safety is a critical issue across the globe, and one that has been targeted as potentially addressable by DNA and protein microarray technology. In addition to concerns about genetically modified foods, pathogens, and growth hormones, the specter of food terrorism is adding yet another wrinkle of concern for consumers and governments alike. Theoretically, arrays could be used to test for this whole spectrum of food contaminants.
But while others contemplate entry into this area, Biacore has become one of the first companies to actually take its technology out of the lab and into the field. The 350-employee firm has worked with a team of scientists over the past two years to adopt its protein assay technology to perform in the rugged conditions of a slaughterhouse and produce analytical information in realtime.
Instead of screening protein biomarkers, Biacore’s technology uses a chip-based technique to investigate protein binding kinetics. Surface plasmon resonance (SPR) occurs when light is reflected off thin metal films to which target molecules are immobilized and addressed by ligands in a mobile phase running along a flow cell. If binding occurs to the immobilized target, the change in SPR angle can be monitored in realtime by detecting changes in the intensity of the reflected light, producing a sensorgram. Biacore binds its target molecules to the surface of a sensor chip over which test material is passed.
The technique is useful for measuring protein-protein interactions because no labeling of the proteins is required.
The key part of the experiment, said Esa Stenberg, vice president of food business unit of Biacore, was conducting the analysis in a slaughterhouse.
“No other technology has been tested like that,” he said. Current analysis consists of taking a sample, getting it to a central lab and then waiting for the results, Stenberg said. “When the sample comes back, the pig is already eaten. This method can get the test done before it enters the food chain.”
In conducting the experiment, a lab was set up 30 to 45 feet from the slaughterhouse to test for sulfame thazine (SMT) and sulfadiazine (SDZ). A technician, standing beside a butcher, would sample the bile of every fifth pig.
The testing apparatus ran through two microplates per hour. The prototype chips had eight parallel circuits for detection and the system analyzed up to 650 bile samples per day. Approximately 20 percent of the pig carcasses were tested, including tests on animals from nearly all suppliers. False positive rates were below 1 percent and no false negatives results were recorded, the company said.
Two years ago, the Foodsense project was created by the European Community Program for Agriculture and Fisheries as part of the Fourth Framework Research Program. Karl-Erik Hellenäs, of the National Food Administration of Sweden, coordinated the project, which included Biacore and Åse Sternesjö, Swedish University of Agricultural Science; Christopher Elliott of the Queens University of Belfast, Northern Ireland; Erik van der Vlis, TNO Nutrition and Food Research Institute of the Netherlands; Willem Haasnoot of Rikilt-DLO of Wageningen, Netherlands; Gertraud Suhren of the Federal Dairy Research Center of Kiel, Germany; Alistair Hamill, Stevenson and Co., Cullybackey, Northern Ireland; and Karl-Heinz Hahne, Nordmilch, of Zeven, Germany.
The project was funded with €2 million — €1 million from the European Community and another €1 million by the partners.
Three assay kit prototypes were developed to test for: clenbuterol and ethinylestradiol in bovine urine; SMT and SDZ in porcine bile; and SMT, SDZ, and enrofloxacin in milk. The assays were designed to test the system by including veterinary drugs, legal and illegal compounds, and different drug and matrix combinations.
“There’s a need for real-time testing,” Lee-Ann Jaykus, associate professor of food science and microbiology at North Carolina State University told BioArray News. “It’s a fairly new idea developed over the last three or four years. It would be a valuable tool, but not a panacea. Personally, I’m sold on DNA-, RNA-based methods, from the standpoint of detection. “
Jaykus said her preferred technology, nucleic acid amplification, works well on pure cultures but has yet to overcome issues of residual matrix components that inhibit detection. She said the Biacore process avoided matrix issues by testing bile, rather than tissue.
“We don’t see [microarray] companies focusing on the food industry’s needs,” Stenberg said. “It’s a complex situation with so many matrices — meats, cereals, pet food. What you want to analyze is huge.”
The company has a suite of instrumentation, software, and sensor chips that it already sells to the food industry, including tests for folic acid, vitamin fortification; and tests for veterinary drugs.
A Biacore spinoff, XenoSense Limited, will commercialize the technology.
Stenberg said the company will now create a second-generation prototype and test it in a different sector.
“We have an interesting application for testing in salmonella line chickens,” he said.