Nanosensors Detect Signs of Cancer in Human Breath
With a single breath, a Breathalyzer™ can tell a police officer when a driver has had too much to drink. Now, thanks to a team of investigators at the Israel Institute of Technology, a single breath may be enough to tell a doctor that their patient has cancer.
Reporting its work in the British Journal of Cancer, a research team headed by Hossam Haick demonstrated that a nanosensor array made of gold nanoparticles can differentiate between healthy patients and those with lung, breast, colorectal, and prostate cancers based on a single exhaled breath. The nanosensor array detects trace chemical known as volatile organic compounds (VOCs) that are generated by cancer cells, escape into the blood stream, and then released along with carbon dioxide into the lungs, from which they are exhaled. In addition, the investigators found that patients with each of the four cancers had characteristic VOC profiles, though these differences were not well-differentiated enough to diagnose a specific form of cancer.
To test their device, the researchers collected exhaled breaths from 177 volunteers, 96 of whom had just been diagnosed with lung, breast, colorectal, or prostate cancer and had not yet received therapy. Each test subject spent up to five minutes breathing purified air before exhaling into a collection bag; this was to ensure that any VOCs detected in the subjects' breaths did not originate in the ambient air that they were breathing. The researchers used collection bags made of chemically inert Mylar so that the bags could be reused after thorough cleaning with ultrapure nitrogen gas.
After testing the samples using their nanosensor array, the investigators repeated their analysis using gas chromatography-mass spectrometry (GC-MS), a highly accurate analytical method that would be too slow and costly to use in any routine diagnostic procedure. GC-MS also requires the use of a pre-concentration step in order to detect the low levels of VOCs in human breath. Comparison of the results obtained using the two techniques showed that the nanosensor arrays was the more accurate of the two methods as far as discriminating between healthy patients and those with cancer, and in distinguishing one type of cancer from another. More importantly, results from the nanosensor array – unlike those obtained using GC-MS – were not dependent on the gender, age, ethnic origin, family cancer history, intake of food additives, drug treatment, exposure to environmental toxins, and smoking habits.
This work is detailed in a paper titled, "Detection of lung, breast, colorectal, and prostate cancers from exhaled breath using a single array of nanosensors." An abstract of this paper is available at the journal's Web site.