Web Date: September 22, 2015
Bendable Breath Sensor Detects Ovarian Cancer
A flexible film layered with gold nanoparticles can tell from a woman’s breath whether she has ovarian cancer. As thin as paper, the bendable device collects several times the data that previous breath sensors could, making it a potentially more cost-effective way to screen for this particularly deadly and difficult-to-detect disease (Nano Lett. 2015, DOI: 10.1021/acs.nanolett.5b03052).
Today’s tools for detecting ovarian cancer—a pelvic exam, radioimmunoassay, or ultrasound—are so invasive or expensive that doctors only recommend them for high-risk women. A noninvasive test cheap enough to use for universal screening would help catch cancers earlier and boost the survival rate, says Hossam Haick of Technion-Israel Institute of Technology. Less than half of women diagnosed with ovarian cancer survive five years.
Haick’s group develops electronic noses—arrays of nanoparticles that capture specific airborne organic compounds in a person’s breath. Those with lung cancer, gastric cancer, tuberculosis, and other diseases exhale a particular mix of organics unique to each disease. Ovarian cancer, the researchers found in previous work, gives one’s breath a distinct mixture of styrene, nonanol, 2-ethylhexanol, 3-heptanone, decanal, and hexadecane.
This information allowed Haick and his group to create a specialized nose for ovarian cancer. They attached an aromatic ligand, chosen through trial and error for its ability to interact with the range of volatile organic compounds associated with ovarian cancer, to gold nanoparticles. Then they layered the nanoparticles in between electrodes onto a flexible, strip of polyimide about the size of a Band-Aid. When an ovarian cancer patient’s breath wafts over the gold nanoparticles, the mix of volatile compounds in her breath interacts with the ligand, causing a measurable change in electrical resistance in the strip. Up to now, Haick’s instrument has required six sensors to detect enough interaction events to reliably diagnose patients. To make the system efficient enough for screening, however, Haick knew he needed to reduce the number of sensors.
So Haick found a way to get more data from each sensor. He bends the strip while noting the strain applied at each position and taking the corresponding resistance measurements. As the sensor ends bend downward, making an arch shape, the distance between the gold nanoparticles grows, favoring interactions with the larger diagnostic molecules. When the sensor flattens again, the interparticle space shrinks, giving smaller compounds a better chance to mingle with the ligand. The pattern of electrical resistance for a given strain throughout the bending process provided enough data per sensor that one bending sensor does what six static sensors did before.
To test the resulting sensor’s performance, Haick wafted the breath of 43 patients with and without ovarian cancer over the sensor as it bent. More than 80% of the time, it correctly identified the patients with ovarian cancer.
Chuan-Jian Zhong of Binghamton University, SUNY, who helped pioneer using bending of flexible films to gather more data from tests, notes that Haick’s group uniquely combined chemical sensing with strain sensing on a flexible film to do cancer detection: “To have these two components in one sensing array system for potential cancer diagnostics is exciting,” he says.
Haick is now applying the same technology to a sensor for tuberculosis. Developing countries need cheap screening tools for TB, he says, and with this technology, he thinks he can print a wearable, accurate sensor for just 20 cents each.
- Chemical & Engineering News
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