New Optical Method Could Enable Cancer Biomarker Breath Test

The new optical sensing method is based on multi-pass spectroscopy and can detect the presence of 1 molecule of formaldehyde in a million air particles, or 1 part per million, even in the presence of gasses that often interfere with optical measurements.

Investigators have developed an extremely sensitive optical method for detecting formaldehyde in a person’s breath, a potential biomarker being investigated for breast and lung cancers. The new method could lead to an inexpensive and efficient way to screen for cancer, according to a press release.

Research published in Biomedical Optics Express found that the new optical sensing method is based on multi-pass spectroscopy and can detect the presence of 1 molecule of formaldehyde in a million air particles, or 1 part per million, even in the presence of gasses that often interfere with optical measurements. The investigators hope to eventually build a table-top device that could be used for cancer screening in any medical consulting room, according to the press release.

“Measuring biomarkers in exhaled breath is noninvasive, painless, and fast, and could be used to screen for cancer even at very early disease stages, which is crucial for successful treatment,” said research team leader Mateusz Winkowski in a press release. “The optical method we developed could make this type of measurement more practical and inexpensive.”

Spectroscopy can be used to identify the chemical composition of a substance by measuring the color of light absorbed or emitted from a sample. The study authors said the multi-pass approach is useful for detecting low concentrations of gas molecules because it increases the extent to which the light interacts with the sample. The multi-pass setup uses an experimental cell with a mirror on each end. When a laser is introduced through a small hole in one mirror and bounced back and forth in the cell, it creates interaction lengths tens or hundreds of times the length of the cell.

The authors noted that noise can be a problem with multi-pass spectroscopy because the multiple laser beams create optical interference, decreasing sensitivity and making it impossible to precisely determine the biomarker concentration. To reduce this interference, the investigators developed a method called optical fringe quenching.

In the investigative technique, the investigators slightly change, or modulate, the emission of the laser over a range of wavelengths and then average the light emitted from the sample over these wavelengths. This method helps eliminate the optical interference enough to allow detection of formaldehyde.

The new approach was tested using calibrated artificial mixtures of formaldehyde in air, showing that the approach was more than sufficient to detect formaldehyde in breath at levels that might indicate the presence of disease.

“Our optical fringe quenching technique can be used to improve any optical system that uses a multi-pass cell,” Winkowski concluded. “It could also be useful for measuring formaldehyde gas emitted from household materials or industrial sources to better understand its effects on human health.”

REFERENCE

New Optical Method Paves Way to Breath Test for Cancer Biomarker [news release]. The Optical Society; November 16, 2020. https://www.osa.org/en-us/about_osa/newsroom/news_releases/2020/new_optical_method_paves_way_to_breath_test_for_ca/. Accessed November 30, 2020.