Blood clots, often unexposed until they break away and result in a stroke or heart attack, can form for a number of reasons in anyone. But now, researchers from MIT have developed a simple urine test that uses nanoparticles to detect thrombin, a major blood-clotting element.
The researchers, who published the details of their system in the journal ACS Nano, hope this test could be used to monitor patients who are at high risk for blood clots.
Though we often associate blood clots with elderly patients, anyone who sits on a plane for prolonged periods of time, lies in a bed while recovering from surgery, or who takes certain medications can be at risk.
In 2012, Medical News Today reported that contraceptives containing Drospirenone have a higher blood clot risk, for example.
When they break away, blood clots can result in strokes or heart attacks, and they sometimes result in death.
In the recent past, young celebrities who have died from blood clots - celebrity stylist Annabel Tollman - or who have been hospitalized due to them - Mariah Carey's husband Nick Cannon - have brought attention to the fact that anyone is at risk.
And the researchers from the Massachusetts Institute of Technology (MIT), led by Professor Sangeeta Bhatia, say that until now, there has not been a fast or easy way to diagnose these blood clots.
Prof. Bhatia says that "some patients are at more risk for clotting, but existing blood tests are not consistently able to detect the formation of new clots."
She and her team note that blood clotting comes from complex protein interactions, which result in the formation of fibrin - a protein that closes wounds. An enzyme called thrombin controls the last step of this process and converts fibrinogen to fibrin.
Nanoparticles interact with thrombin
Prof. Bhatia and colleagues created technology last year that was used to detect colorectal cancer, but they found that the same technology could be used to detect blood clots.
"So we took the test we had developed before, which is an injectable nanoparticle, and made it a thrombin sensor," she says.
The system, which was tested in mice, uses iron oxide nanoparticles that the Food and Drug Administration (FDA) has approved for use in humans. These nanoparticles are coated with short proteins known as peptides that are specifically made to interact with thrombin.
The nanoparticles move through the body of mice after being injected, and when they come across thrombin, the thrombin splits the peptides at a specific location, which releases particles that come out in urine.
Then, protein fragments in the urine can be identified after treating the sample with antibodies that are specific to peptide tags in the fragments.
The number of these tags found in the urine is proportional to the level of blood clotting in the lungs of the mice, the researchers say.
'Pee on this stick and call me in the morning'
Prof. Bhatia sees two possible uses for the test she and her team created:
- For screening patients in the emergency room who complain of symptoms indicative of a blood clot, and
- To monitor patients at high risk, for example people who fly frequently or who spend a lot of time recovering from surgery in bed.
For the second application, Prof. Bhatia says she is working on a urine dipstick test that doctors could give to patients going home after surgery:
"If a patient is at risk for thrombosis, you could send them home with a 10-pack of these sticks and say, 'Pee on this every other day and call me if it turns blue.'"
With funding from MIT's Deshpande Center for Technological Innovation, Prof. Bhatia plans to launch a company with the aim of commercializing the technology.
She says that the system could also potentially monitor and diagnose cancer, or track liver, pulmonary and kidney fibrosis.