Scientists are using antibodies to detect minute amounts of toxins in foods, writes Dr Claire O'Connell.
Sometimes nature can provide ingenious solutions to technological challenges. For example, how do you detect tiny but potentially dangerous levels of poisons in food?
Scientists at Dublin City University are borrowing tricks from the body's immune system to help answer this question.
Our immune systems make proteins called antibodies that recognise and bind to specific molecules. The DCU researchers are engineering antibodies to screen food samples for minute levels of cancer-causing contaminants called aflatoxins, poisons made by Aspergillus moulds that can grow on foodstuffs, particularly under warm, humid conditions.
"You can find them in certain types of foods, for example nuts or figs or cereals, although in Ireland it's not a major problem in cereals," explains Prof Richard O'Kennedy, who leads the research project at DCU's school of biotechnology.
The trouble is that if animals or humans eat aflatoxins the poisons can accumulate in the liver or pass into milk. This is not good news for the consumer.
"Aflatoxins can cause certain types of cancer, they can affect the liver and kidneys and they can push down the immune system," explains O'Kennedy, who has received several awards for his contribution to science, including the Royal Irish Academy Medal for Biochemistry in 2001 and the DCU President's Award for Excellence in Research in Science and Engineering in 2005.
Combinations of different aflatoxins may pose even greater health risks, he says. "Some of these molecules - while they might individually be below the level that would be allowed by regulations - if you have a number of them together the sum total of the effect might be greater than just adding them."
The EU is currently updating regulations to reduce the levels of aflatoxin contamination allowed in foods. Now O'Kennedy's group is developing a highly sensitive antibody system that can detect aflatoxins at these new, lower thresholds.
To do this the researchers first generate antibodies that can bind to aflatoxins. Then they tweak the genetic structure of those parent antibodies to make more specific protein molecules, explains Sharon Stapleton, a PhD candidate in O'Kennedy's lab.
By altering the genetic material they can fine-tune an antibody's ability to detect different types and amounts of aflatoxins.
"Because of the new EU legislation it's really important that we get down to the level they require," says O'Kennedy. "With these we are talking about 100 picograms (less than one billionth of a gram), so we can detect them at very low levels."
Convenience is also an issue. Scientists currently use expensive, lab-based methods to detect aflatoxins. The DCU researchers want to make a more portable, hand-held device to measure aflatoxin contamination quickly on site.
They are developing a chip-based diagnostic system to measure levels of the toxin in collaboration with Belfast company XenoSense .
The test adds specially engineered, "small" antibodies to a food sample where they bind to any aflatoxin present. The sample is then washed over a chip that has aflatoxin molecules stuck to its surface, and leftover small antibodies bind to the aflatoxin on the chip.
By measuring the amount of leftover antibody that binds to the chip, the researchers can determine how much aflatoxin was in the food sample.
"Let's say there is no contamination, the small antibody will bind onto the aflatoxin on the chip and you see a huge signal," O'Kennedy explains. "If there is contamination, all of the small antibody will bind onto the aflatoxin in the sample and you won't see a thing on the chip."
Early results from the project have generated a lot of interest from government laboratories and from the food industry according to Dr Andrew Baxter, general manager at XenoSense.
"The nice thing about these technologies is that they are generic and we know they have lots of applications," he says.
The DCU group is also engineering antibodies to detect drugs of abuse, antibiotics, the blood-thinning medication warfarin and a diagnostic marker for prostate cancer.