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Get a Whiff of This

Can electronic noses come close to the real thing?

By | September 1, 2012

image: Get a Whiff of This Andrzej Krauze

Artificial noses have orbited the Earth in spacecraft, inhaled in doctors’ offices, and sniffed in food-processing plants, all in an effort to surpass the sensitivity and specificity of the mammalian olfactory organ. Sure, dogs have been known to smell a cancer, but can they tell you what kind it is, too? Hossam Haick, a professor at the Technion-Israel Institute of Technology, has developed a device that can do just that. By collecting a breath sample from patients, Haick’s electronic nose can determine whether that person has lung cancer, as opposed to breast, prostate, or head and neck tumors, and even whether it’s non-small cell or small cell lung cancer.

Cancer patients emit a suite of volatile organic compounds in their breath that is different from the composition of healthy patients’ breath—and that differs from cancer to cancer. “If we develop an artificial nose which can detect very tiny amounts—at the range of parts per billion or parts per trillion—of these biomarkers of cancer, then we can provide a very simple and inexpensive way to detect cancer,” says Haick. “And most importantly, this is not invasive.”

Haick’s cancer sniffer is currently in clinical trials, but there are already some electronic noses on the market. Alpha MOS, a French company, markets electronic noses that are used in food and beverage quality control, in plastics and packaging manufacturing to detect contaminants, and in flavor and perfume development.

If we develop an artificial nose which can detect very tiny amounts of these biomarkers of cancer, then we can provide a very simple and inexpensive way to detect cancer.
—Hossam Haick, Technion-Israel Institute of Technology


Pretty much all electronic noses are based on the same approach, “sort of a fingerprint pattern recognition, like in the human process of olfaction,” says Alpha MOS spokesperson Marion Bonnefille. The mammalian sense of smell uses a combinatorial code composed of responses from different olfactory receptors. Rather than have an odor receptor specific to a particular odor, mammals interpret different scents by the pattern of receptors stimulated and the neural responses they excite. “In this way, 1,000 different receptors can recognize a million different odorants,” says Nate Lewis, a professor at CalTech and a pioneer in developing electronic noses.

 

Lewis’s own technology works through an array of tiny sensors made of polymer film that act like sponges. Each one responds to an odor slightly differently, and the amount of swelling of the “sponge” in the presence of a vapor changes its electronic resistance. The pattern of resistance changes is distinct for each odor, giving the electronic nose the ability to distinguish between good wine and bad wine, toluene and benzene, and even between mirror images of the same molecule. Lewis has been able to detect compounds diluted down to the tens of parts per trillion.

But there is a limit to the seemingly endless uses for artificial noses. “What we are not good at . . . is [breaking] down a complex mixture into hundreds of different compounds,” says Lewis. Gas chromatography-mass spectrometry, and the human nose to some degree, can tell you the specific composition of a sample, whereas an e-nose can only tell you whether or not the sample matches a particular profile. “It would be very good to know what are the biomarkers found inside [a breath sample], but this would require further studies and further redevelopment of the device,” says Haick.

Perena Gouma of the State University of New York, Stony Brook, has made artificial noses that can detect particular components of a person’s breath. “We have arrays of sensors, each of which can target a specific biomarker . . . or class of chemicals,” she says. In such a way, her lab is developing gadgets to measure the likelihood of? having a health condition. Whereas the electronic nose uses the overall differences between healthy breath and diseased breath to distinguish between them, Gouma’s approach requires knowledge of the particular biomarkers in advance so that sensors can be developed specifically to detect them. (See “Vital Signs,” The Scientist, August 2011.)

The inability to describe the composition of a sample aside, Tufts University chemist David Walt says that during his research on electronic noses “we pretty much couldn’t find a problem that we couldn’t solve.” That is, except for one very big challenge: for each problem an e-nose can solve, say, to distinguish spoiled milk from fresh or safe packaging from contaminated packaging, “every one of those different problems is a training and then validation that can eat up a huge amount of money,” Walt says. Additionally, recalibrating each device might be a massive undertaking if it requires, for example, bringing in numerous patients with a certain disease. “That’s not trivial.”

Walt gave up on researching electronic noses several years ago because he could not find investors to move the technology into the real world, presumably because of these challenges. But he is somewhat optimistic for those who remain in the field—if they can figure out how to make it easier to train the devices to recognize signals of particular odors. “Lots of opportunities are there,” he says.

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Avatar of: Syafiqah Kamarudin

Syafiqah Kamarudin

Posts: 1457

September 18, 2012

hi, i'm just passing by here and what an amazing article i must say. to get to detect cancer by using such harmless and economy method will definitely be a breakthrough in the medical field. hope the research can be continued on soon...

Avatar of: danskow

danskow

Posts: 1

September 21, 2012

I believe our paper published in the Am J Respir Crit Care Med Vol 171. pp 1286–1291, 2005 "Detection of Lung cancer by Sensor Array Analyses of Exhaled Breath" opened the door for the use of electronic noses to detect lung cancer. This paper published in 2005 has had much continued research and shows the potential for this science. To detect desease in exhaled breath of humans. Although we are not there yet we are knocking on the door. The abstract is attached for those with an interest in this science.
Rationale: Electronic noses are successfully used in commercial applications,including detection and analysis of volatile organic compoundsin the food industry. Objectives: We hypothesized that theelectronic nose could identify and discriminate between lung diseases,especially bronchogenic carcinoma. Methods: In a discoveryand training phase, exhaled breath of 14 individuals with bronchogeniccarcinoma and 45 healthy control subjects or control subjectswithout cancer was analyzed. Principal components and canonic discriminantanalysis of the sensor data was used to determine whetherexhaled gases could discriminate between cancer and noncancer. Discriminationbetween classes was performed using Mahalanobis distance.Support vector machine analysis was used to create and applya cancer prediction model prospectively in a separate group of 76individuals, 14 with and 62 without cancer. Main Results: Principalcomponents and canonic discriminant analysis demonstrated discriminationbetween samples from patients with lung cancer and thosefrom other groups. In the validation study, the electronic nose had71.4% sensitivity and 91.9% specificity for detecting lung cancer; positiveand negative predictive values were 66.6 and 93.4%, respectively.In this population with a lung cancer prevalence of 18%, positiveand negative predictive values were 66.6 and 94.5%, respectively.Electronic noses are successfully used in commercial applications,
including detection and analysis of volatile organic compounds
in the food industry. Objectives: We hypothesized that theelectronic nose could identify and discriminate between lung diseases,especially bronchogenic carcinoma. Methods: In a discoveryand training phase, exhaled breath of 14 individuals with bronchogeniccarcinoma and 45 healthy control subjects or control subjectswithout cancer was analyzed. Principal components and canonic discriminantanalysis of the sensor data was used to determine whetherexhaled gases could discriminate between cancer and noncancer. Discriminationbetween classes was performed using Mahalanobis distance.Support vector machine analysis was used to create and applya cancer prediction model prospectively in a separate group of 76individuals, 14 with and 62 without cancer. Main Results: Principalcomponents and canonic discriminant analysis demonstrated discriminationbetween samples from patients with lung cancer and thosefrom other groups. In the validation study, the electronic nose had71.4% sensitivity and 91.9% specificity for detecting lung cancer; positiveand negative predictive values were 66.6 and 93.4%, respectively.In this population with a lung cancer prevalence of 18%, positiveand negative predictive values were 66.6 and 94.5%, respectively.Objectives: We hypothesized that the
electronic nose could identify and discriminate between lung diseases,
especially bronchogenic carcinoma. Methods: In a discoveryand training phase, exhaled breath of 14 individuals with bronchogeniccarcinoma and 45 healthy control subjects or control subjectswithout cancer was analyzed. Principal components and canonic discriminantanalysis of the sensor data was used to determine whetherexhaled gases could discriminate between cancer and noncancer. Discriminationbetween classes was performed using Mahalanobis distance.Support vector machine analysis was used to create and applya cancer prediction model prospectively in a separate group of 76individuals, 14 with and 62 without cancer. Main Results: Principalcomponents and canonic discriminant analysis demonstrated discriminationbetween samples from patients with lung cancer and thosefrom other groups. In the validation study, the electronic nose had71.4% sensitivity and 91.9% specificity for detecting lung cancer; positiveand negative predictive values were 66.6 and 93.4%, respectively.In this population with a lung cancer prevalence of 18%, positiveand negative predictive values were 66.6 and 94.5%, respectively.Methods: In a discovery
and training phase, exhaled breath of 14 individuals with bronchogenic
carcinoma and 45 healthy control subjects or control subjects
without cancer was analyzed. Principal components and canonic discriminant
analysis of the sensor data was used to determine whether
exhaled gases could discriminate between cancer and noncancer. Discrimination
between classes was performed using Mahalanobis distance.
Support vector machine analysis was used to create and apply
a cancer prediction model prospectively in a separate group of 76
individuals, 14 with and 62 without cancer. Main Results: Principalcomponents and canonic discriminant analysis demonstrated discriminationbetween samples from patients with lung cancer and thosefrom other groups. In the validation study, the electronic nose had71.4% sensitivity and 91.9% specificity for detecting lung cancer; positiveand negative predictive values were 66.6 and 93.4%, respectively.In this population with a lung cancer prevalence of 18%, positiveand negative predictive values were 66.6 and 94.5%, respectively.Main Results: Principal
components and canonic discriminant analysis demonstrated discrimination
between samples from patients with lung cancer and those
from other groups. In the validation study, the electronic nose had
71.4% sensitivity and 91.9% specificity for detecting lung cancer; positive
and negative predictive values were 66.6 and 93.4%, respectively.
In this population with a lung cancer prevalence of 18%, positive
and negative predictive values were 66.6 and 94.5%, respectively.Conclusion: The exhaled breath of patients with lung cancer hasdistinct characteristics that can be identified with an electronicnose. The results provide feasibility to the concept of using theelectronic nose for managing and detecting lung cancer.The exhaled breath of patients with lung cancer has
distinct characteristics that can be identified with an electronic
nose. The results provide feasibility to the concept of using the
electronic nose for managing and detecting lung cancer.

Avatar of: Kieran McMullen

Kieran McMullen

Posts: 1457

September 23, 2012

this is a breakthrough to be sure, but I read articles all the time with equally signifigant revelations, things like warp drives and super-durable materials, but I have to know, why don't we ever see these things implemented? when will I be able to use the chemical nose at my local GP?

September 24, 2012

Kierran, many developments don't turn out to be cost effective to develop or it's difficult to get doctors informed about the benefits. Probably more to the point, it did mention in the second last paragraph about the downside to the e-nose.

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