Finding blood clots using Nanotechnology .. BEFORE …they wreak havoc.


Finding blood clots before they wreak havoc

Anne Trafton, MIT News Office
Simple urine test developed by MIT engineers uses nanotechnology to detect dangerous blood clotting.
Life-threatening blood clots can form in anyone who sits on a plane for a long time, is confined to bed while recovering from surgery, or takes certain medications.
There is no fast and easy way to diagnose these clots, which often remain undetected until they break free and cause a stroke or heart attack. However, new technology from MIT may soon change that: A team of engineers has developed a way to detect blood clots using a simple urine test.
The noninvasive diagnostic, described in a recent issue of the journal ACS Nano, relies on nanoparticles that detect the presence of thrombin, a key blood-clotting factor.
Such a system could be used to monitor patients who are at high risk for blood clots, says Sangeeta Bhatia, senior author of the paper and the John and Dorothy Wilson Professor of Biochemistry.
“Some patients are at more risk for clotting, but existing blood tests are not consistently able to detect the formation of new clots,” says Bhatia, who is also a senior associate member of the Broad Institute and a member of MIT’s Koch Institute for Integrative Cancer Research and Institute for Medical Engineering and Science (IMES).
Lead authors of the paper are Kevin Lin, a graduate student in chemical engineering, and Gabriel Kwong, a postdoc in IMES. Other authors are Andrew Warren, a graduate student in Health Sciences and Technology (HST), and former HST postdoc David Wood.
Sensing thrombin
Blood clotting is produced by a complex cascade of protein interactions, culminating in the formation of fibrin, a fibrous protein that seals wounds. The last step of this process — the conversion of fibrinogen to fibrin — is controlled by an enzyme called thrombin.
Current tests for blood clotting are very indirect, Bhatia says. One, known as the D-dimer test, looks for the presence of fibrin byproducts, which indicates that a clot is being broken down, but will not detect its initial formation.
Bhatia and her colleagues developed their new test based on a technology they first reported last year for early detection of colorectal cancer. “We realized the same exact technology would work for blood clots,” she says. “So we took the test we had developed before, which is an injectable nanoparticle, and made it a thrombin sensor.”
The system consists of iron oxide nanoparticles, which the Food and Drug Administration has approved for human use, coated with peptides (short proteins) that are specialized to interact with thrombin. After being injected into mice, the nanoparticles travel throughout the body. When the particles encounter thrombin, the thrombin cleaves the peptides at a specific location, releasing fragments that are then excreted in the animals’ urine.
Once the urine is collected, the protein fragments can be identified by treating the sample with antibodies specific to peptide tags included in the fragments. The researchers showed that the amount of these tags found in the urine is directly proportional to the level of blood clotting in the mice’s lungs.
In the previous version of the system, reported last December in Nature Biotechnology, the researchers used mass spectrometry to distinguish the fragments by their mass. However, testing samples with antibodies is much simpler and cheaper, the researchers say.
Rapid screening
Bhatia says she envisions two possible applications for this kind of test. One is to screen patients who come to the emergency room complaining of symptoms that might indicate a blood clot, allowing doctors to rapidly triage such patients and determine if more tests are needed.
“Right now they just don’t know how to efficiently define who to do the more extensive workup on. It’s one of those things that you can’t afford to miss, so patients can get an unnecessarily expensive workup,” Bhatia says.
Another application is monitoring patients who are at high risk for a clot — for example, people who have to spend a lot of time in bed recovering from surgery. Bhatia is working on a urine dipstick test, similar to a pregnancy test, that doctors could give patients when they go 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,’” she says.
The technology could also be useful for predicting recurrence of clots, says Henri Spronk, an assistant professor of biochemistry at Maastricht University in the Netherlands.
“High levels of activation markers have been related to recurrent thrombosis, but they don’t have good sensitivity or specificity. Through application of the nanoparticles, if proven well-tolerated and nontoxic, alterations in the normal low levels of physiological thrombin generation might be easily detected,” says Spronk, who was not part of the research team.
Bhatia plans to launch a company to commercialize the technology, with funding from MIT’s Deshpande Center for Technological Innovation. Other applications for the nanoparticle system could include monitoring and diagnosing cancer. It could also be adapted to track liver, pulmonary, and kidney fibrosis, Bhatia says.
The research was funded by the Koch Institute Frontier Research Fund, the Kathy and Curt Marble Cancer Research Fund, the Mazumdar-Shaw International Oncology Fellows Program, the Burroughs Wellcome Fund, and the Deshpande Center.

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Nanoparticles Enable Earlier Cancer Diagnosis


QDOTS imagesCAKXSY1K 8 From Science Daily, Dec. 17, 2012 — Finding ways to diagnose cancer earlier could greatly improve the chances of survival for many patients. One way to do this is to look for specific proteins secreted by cancer cells, which circulate in the bloodstream. However, the quantity of these biomarkers is so low that detecting them has proven difficult.


 A new technology developed at MIT may help to make biomarker detection much easier. The researchers, led by Sangeeta Bhatia, have developed nanoparticles that can home to a tumor and interact with cancer proteins to produce thousands of biomarkers, which can then be easily detected in the patient’s urine.

This biomarker amplification system could also be used to monitor disease progression and track how tumors respond to treatment, says Bhatia, the John and Dorothy Wilson Professor of Health Sciences and Technology and Electrical Engineering and Computer Science at MIT.

“There’s a desperate search for biomarkers, for early detection or disease prognosis, or looking at how the body responds to therapy,” says Bhatia, who is also a member of MIT’s David H. Koch Institute for Integrative Cancer Research. She adds that the search has been complicated because genomic studies have revealed that many cancers, such as breast cancer, are actually groups of several diseases with different genetic signatures.

The MIT team, working with researchers from Beth Israel Deaconess Medical Center, described the new technology in a paper appearing in Nature Biotechnology on Dec. 16. Lead author of the paper is Gabriel Kwong, a postdoc in MIT’s Institute for Medical Engineering and Science and the Koch Institute.

Amplifying cancer signals

Cancer cells produce many proteins not found in healthy cells. However, these proteins are often so diluted in the bloodstream that they are nearly impossible to identify. A recent study from Stanford University researchers found that even using the best existing biomarkers for ovarian cancer, and the best technology to detect them, an ovarian tumor would not be found until eight to 10 years after it formed.

“The cell is making biomarkers, but it has limited production capacity,” Bhatia says. “That’s when we had this ‘aha’ moment: What if you could deliver something that could amplify that signal?”

Serendipitously, Bhatia’s lab was already working on nanoparticles that could be put to use detecting cancer biomarkers. Originally intended as imaging agents for tumors, the particles interact with enzymes known as proteases, which cleave proteins into smaller fragments.

Cancer cells often produce large quantities of proteases known as MMPs. These proteases help cancer cells escape their original locations and spread uncontrollably by cutting through proteins of the extracellular matrix, which normally holds cells in place.

The researchers coated their nanoparticles with peptides (short protein fragments) targeted by several of the MMP proteases. The treated nanoparticles accumulate at tumor sites, making their way through the leaky blood vessels that typically surround tumors. There, the proteases cleave hundreds of peptides from the nanoparticles, releasing them into the bloodstream.

The peptides rapidly accumulate in the kidneys and are excreted in the urine, where they can be detected using mass spectrometry.

This new system is an exciting approach to overcoming the problem of biomarker scarcity in the body, says Sanjiv Gambhir, chairman of the Department of Radiology at Stanford University School of Medicine. “Instead of being dependent on the body to naturally shed biomarkers, you’re sampling the site of interest and causing biomarkers that you engineered to be released,” says Gambhir, who was not part of the research team.

Distinctive signatures

To make the biomarker readings as precise as possible, the researchers designed their particles to express 10 different peptides, each of which is cleaved by a different one of the dozens of MMP proteases. Each of these peptides is a different size, making it possible to distinguish them with mass spectrometry. This should allow researchers to identify distinct signatures associated with different types of tumors.

In this study, the researchers tested their nanoparticles’ ability to detect the early stages of colorectal cancer in mice, and to monitor the progression of liver fibrosis.

Liver fibrosis is an accumulation of scarring in response to liver injury or chronic liver disease. Patients with this condition have to be regularly monitored by biopsy, which is expensive and invasive, to make sure they are getting the right treatment. In mice, the researchers found that the nanoparticles could offer much more rapid feedback than biopsies.

They also found that the nanoparticles could accurately reveal the early formation of colorectal tumors. In ongoing studies, the team is studying the particles’ ability to measure tumor response to chemotherapy and to detect metastasis.

The research was funded by the National Institutes of Health and the Kathy and Curt Marble Cancer Research Fund.