Cancer detection: Where no breathalyzer has gone before
A handheld breathalyzer for cancer detection? It might sound far-fetched, but researchers at the University of Oklahoma in Norman are working on a key component that could make such a tool a reality. And the inspiration was not a Star Trek tricorder, but man’s best friend.
“It was really the dogs that cinched the deal,” said Patrick McCann, a George Lynn Cross research professor at the university’s school of electrical and computer engineering. He had seen anecdotal reports in medical journals of dogs that could sniff out cancer, and when studies started showing statistical evidence that it wasn’t “quack science,” McCann took note. A study published in the March 2006 issue of Integrative Cancer Therapies reported that dogs could find breast and lung cancer on exhaled breath samples 88 and 97 percent of the time, respectively.
“The dogs are already doing it,” McCann said. “They’re just not telling us what they’re smelling.”
What they’re smelling are gas phase cancer biomarkers – acetaldehyde, ethane or formaldehyde molecules that act as cancer signals – on human breath. But the dogs cannot communicate which gas phase molecule they have detected. Sensors can.
Arnaud Sow, a University of Oklahoma graduate student from France, processes a sample for laser fabrication. This type of research allows engineers and researchers to make small nanoengineered materials. Courtesy of the University of Oklahoma.
McCann and his team, made up of students and colleagues at the university, are using mid-IR lasers to measure suspected cancer biomarkers on the breath. They chose lasers because of deficiencies they perceived in traditional gas chromatography/mass spectrometry analysis: species interference, operational complexity and trouble detecting short-lived reactive molecules. The team hopes to combine nanotechnology with the inherent low-heat quality of the lasers to produce a compact, workable cancer detector.
It’s the kind of laser that’s important. “We’re competing with the quantum cascade people,” McCann said. “I think our approach is better because ours works and theirs hasn’t.” Not that he means any disrespect: “Let the published data speak for itself,” he added quickly. “We’ve built prototype instruments; we’ve done breath analysis with them, and it works. Quantum cascade is beautiful physics, but there have yet to be any published studies.”
Mid-IR lasers are better than quantum cascade lasers, McCann said, because mid-IR lasers require less power and allow for better thermal management. “A quantum cascade laser requires about an amp of current, and the voltages are also high,” he said. “It’s a power hog. And dissipating that heat is a challenge. If you want a battery-operated sensor, it’s just not viable.” With mid-IR, “you don’t have to worry about heat sinking it because you don’t have a heat sink problem. With quantum cascade lasers, you’ll always have that.”
In spite of the friendly quantum cascade laser/mid-IR rivalry, this is serious work. “Let’s focus on the goal, which is cancer detection,” McCann said. “I know we can do it. What we’ve already done is show that this type of laser has the proper tunability, the reliability to do breath analysis.”
A molecular beam epitaxy system is used to make the very small laser materials for use in compact and low-cost breath meters for early cancer detection. Courtesy of the University of Oklahoma.
The next step is to show that it works. “We need to show that we can improve operating temperatures to make handheld sensors a reality,” McCann said. “We’ve already got low thermal load and low waste heat to dissipate, so they go together.” You need both, he added, to make a laser that works at room temperature – say, in a doctor’s office.
McCann doesn’t expect his cancer breathalyzer to be ready for the market anytime soon, however. “In an ideal world,” he said, “if we got a fraction of the funding that’s going into genomics, it could be five years. Ten to twenty, at the current pace it’s muddling along. Things don’t happen without resources.
“Hopefully sooner than 2230, or whatever the date was in Star Trek,” he said.
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