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Tiny Tools Offer New Biopsy Approach

July 9, 2013
Swarm of micro-grippers

These star-shaped tools, each as small as a speck of dust, are autonomously activated by the body’s heat, which causes their tiny “fingers” to close on clusters of cells.

Using swarms of untethered “grippers,” each as small as  a speck of dust, Johns Hopkins engineers and physicians have devised a new approach to conducting biopsies that could eventually provide a more effective way of finding early signs of cancer and other diseases in the body’s narrowest conduits.

In two recent peer-reviewed journal articles, the researchers reported using these sub-millimeter-sized tools, which require no batteries or wires, to conduct the first-ever biopsies in the gastrointestinal tract of a live pig, selected because its gastro-intestinal tract is similar to that of humans.

“This is a significant accomplishment,” said David Gracias, an associate professor of chemical and biomolecular engineering, whose lab developed the micro-grippers. “Because we can send the grippers through natural orifices, it is an important advance in minimally invasive treatment, and a step toward the ultimate goal of making surgical procedures non-invasive.”


This photo compares the size of a microgripper with that the much larger forceps used in traditional biopsies. Image credit: Evin Gultepe, Gracias Lab, Johns Hopkins University.

The devices are called “mu-grippers,” incorporating the Greek letter that represents the term for “micro.” Instead of relying on electric or pneumatic power, these star-shaped tools are autonomously activated by the body’s heat, which causes their tiny fingers to close on clusters of cells. Because they contain a magnetic material, they can be retrieved by way of a magnetic catheter.

Another member of the research team, physician Florin Selaru of the School of Medicine, praised the mu-grippers’ ability to collect far more samples from many more locations than can a conventional biopsy, which includes only 30 to 40 samples.

“Based on a small sample, you can’t always draw accurate inferences,” said Selaru. “We can deploy hundreds or even thousands of these grippers to get more samples, and a better idea of what kind of, or whether a disease is present.”

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