FLOWER power optical sensor: another tool in Covid-19 battle

05 Nov 2020

University of Arizona’s “whispering” development involved in hunt for compounds to cut virus binding to receptor in the lungs.

From Ford Burkhart in Tucson

A powerful optical sensor developed by a University of Arizona researcher may be on its way to rapidly detecting a single viral particle of Covid-19. The device, devised by Judith Su, a UA professor of biomedical engineering and optics is called FLOWER, standing for “frequency locked optical whispering evanescent resonator.”

That word “whispering” has a story of its own. It comes from the ability of waves to travel far when someone whispers near circular walls, for example like those at the Whispering Gallery at St. Paul’s Cathedral in London. Something similar happens in Su’s device.

To detect a specific molecule under study, the device sends out waves of light, just 100µm across. In turn, some of the light particles will travel inside a tiny sensor shaped like a toroid.

As the laser light moves around inside the microtoroid ring, a small amount extends out beyond the sensor and interacts with a solution such as urine, blood, sweat or water. FLOWER combines microtoroid optical resonator technology with a variety of noise reduction and data processing techniques for single macromolecular detection.

Highly sensitive

If the molecule under study is present, it will change the light’s index of refraction very slightly. As the light interacts with the molecule, the change becomes more pronounced, making FLOWER more sensitive than many other sensing methods, said Su.

FLOWER determines – in just 30 seconds – whether the target or analyte is present in a sample. “Conventional sensors will interact with a molecule once. But in this case, it will interact with the molecule hundreds of thousands of times, so we get this buildup of signal, which is what gives us our sensitivity boost,” said Su.

FLOWER has several additional advantages over other sensing methods. Many use fluorescent dyes or other chemicals to label the analyte and make it visible under a microscope. But the often expensive and difficult-to-produce labels can interfere with particularly small analytes. Additionally, FLOWER’s sensor is larger than others, so it casts a wider net to capture trace amounts of analytes.

Detecting coronavirus

FLOWER can be adapted for various substances and can be used to address some of the medical community’s most pressing problems, said Su. She is collaborating with a group at the California Institute of Technology on a Covid-19 project. The teams are searching for compounds that reduce binding of SARS-CoV-2 to a specific receptor in the lungs and therefore help protect against the virus.

“We’re also starting a project to research olfaction, vapor and breath,” Su said. “There are a lot of molecules in the air that could provide a noninvasive way to test for disease. Say, a breath test for Covid-19 instead of a swab or a blood test.”

Su’s work has attracted major national support. In October, she received a $1.82 million research award from the US National Institute of General Medical Sciences, part of the National Institutes of Health, to make her sensors even more sensitive and portable.

Her research site, which she calls “the Little Sensor Lab,” is part of the University of Arizona’s Department of Biomedical Engineering, the Wyant College of Optical Sciences, and BIO5 Institute. With the new funding, Su’s lab intends to increase the device’s sensitivity to detect even smaller and more lightweight molecules.

Further applications

Additionally, the researchers are working toward adapting the device to detect not just the presence of a molecule but also molecular abnormalities or changes in shape. The device could help with the study of light-activated proteins in the eye and increase scientific understanding of vision.

Up to now, the FLOWER lab has sensed interleukin-2, a cytokine-signaling molecule in the immune system, and has investigated the progression of human Burkitt lymphoma tumor cells in mice.

Su’s work employing FLOWER operating in serum and cerebrospinal fluid with Alzheimer’s patients is being submitted as a journal article. She has also used FLOWER to test for human chorionic gonadotropin (hCG) in the urine of pregnant women at various trimesters of pregnancy. The lab’s ongoing work involves biomarkers for prostate cancer, ovarian cancer and Lyme disease.

The Covid-19 crisis has expanded their work to new coronavirus horizons. “FLOWER’s speed and sensitivity make it an ideal asset for the war against Covid-19,” she said. “Everything our lab does is centered around ultrasensitive optical sensing, for a wide variety of applications, like environmental health monitoring, food and water quality monitoring, and detecting toxic industrial chemicals,” Su said. “Anything worth sensing, we sense.”