How the new technology uses human teardrops to spot disease

Human tears could carry a flood of useful information.

With just a few drops, a new technique can spot eye disease and even glimpse signs of diabetes, scientists report July 20 in ACS Nano.

“We wanted to demonstrate the potential of using tears to detect disease,” says Fei Liu, a biomedical engineer at Wenzhou Medical University in China. It’s possible the droplets could open a window for scientists to peer into the entire body, he says, and one day even let people quickly test their tears at home.Like saliva and urine, tears contain tiny sacs stuffed with cellular messages (SN: 9/3/13). If scientists could intercept these microscopic mailbags, they could offer new intel on what’s happening inside the body. But collecting enough of these sacs, called exosomes, is tricky. Unlike fluid from other body parts, just a trickle of liquid leaks from the eyes.

So Liu’s team devised a new way to capture the sacs from tiny volumes of tears. First, the researchers collected tears from study participants. Then, the team added a solution containing the tears to a device with two nanoporous membranes, vibrated the membranes and sucked the solution through. Within minutes, the technique lets small molecules escape, leaving the sacs behind for analysis.

The results gave scientists an eyeful. Different types of dry-eye disease shed their own molecular fingerprints in people’s tears, the team found. What’s more, tears could potentially help doctors monitor how a patient’s diabetes is progressing.

Now, the scientists want to tap tears for evidence of other diseases as well as depression or emotional stress, says study coauthor Luke Lee, a bioengineer at Harvard Medical School. “This is just the beginning,” he says. “Tears express something that we haven’t really explored.”Scientific American Logo

MEDICINE | OPINION

Your Tears Might Save Your Life Someday

They could ultimately be used to find diseases the way blood tests do now—but cheaper and more easily

By Anis Barmada on November 19, 2020

Your Tears Might Save Your Life Someday

Credit: Getty Images

At any given moment, about seven microliters of tears are present in each of our eyes—about a tenth of a drop of water. You might think of them as nothing more than salty water, but it’s more accurate to think if them filtered blood; they deliver oxygen and nutrients to our eyes, removing waste, serving as the first line of defense against pathogens and helping to heal injuries.

Tears also contain traces of the various chemicals originally present in blood, some of which serve as markers of illness—glucose, for example, which can signal diabetes, or enzymes that point to possible liver disease. That’s a primary reason doctors order blood tests. But it also that means that physicians—and maybe, in the near future, you—can look for indicators of illness by looking at your tears.Research has already shown that markers of many of the most common and devastating diseases, such as cancer, multiple sclerosis, diabetes mellitus, cystic fibrosis and Parkinson’s disease are found in tears. Work is already under way to validate the use of such markers for diagnosing Alzheimer's disease. And recently, a technology named TearExo has been developed for breast cancer screening using tears collected by patients themselves. That could greatly reduce the costs of testing and allow earlier detection of malignancy than mammograms can provide.

Tear testing could also make an impact in the COVID-19 pandemic: current research has focused on developing a test to diagnose SARS-CoV-2 infections, as well as document prior infections, through antibody testing. These assays are typically done with blood—but coronavirus RNA has been detected in tears as well, and antibodies to the virus may also be measured from tears. That means a rapid and cheap tear test could be developed in the near future—and because no needles are involved, this, too, could in principle be self-administered at home.

But the potential advantages of tears as indicators of health go beyond occasional testing. One promising tear-based technology is a smart contact lens that continuously monitors a patient’s biomarkers, significantly improving disease prevention and early detection; it has attracted the attention of Novartis and Google, among other major companies, and is currently under development in research laboratories around the world. One significant step in its development was the first stand-alone contact lens with an integrated battery, in 2019. More recently, a smart contact lens has been successfully developed for continuous glucose monitoring and treatment of diabetic retinopathy. Such a product probably won’t be ready for commercial use for several years. But according to the Centers for Disease Control and Prevention, about 45 million people in the U.S. already wear contact lenses to correct their vision. Switching to a smart version would be simple for them—and of course, you can wear smart lenses even if your vision is perfect,Scientific American Logo

MEDICINE | OPINION

Your Tears Might Save Your Life Someday

They could ultimately be used to find diseases the way blood tests do now—but cheaper and more easily

By Anis Barmada on November 19, 2020

Your Tears Might Save Your Life Someday

Credit: Getty Images

Research has already shown that markers of many of the most common and devastating diseases, such as cancer, multiple sclerosis, diabetes mellitus, cystic fibrosis and Parkinson’s disease are found in tears. Work is already under way to validate the use of such markers for diagnosing Alzheimer's disease. And recently, a technology named TearExo has been developed for breast cancer screening using tears collected by patients themselves. That could greatly reduce the costs of testing and allow earlier detection of malignancy than mammograms can provide.