Microgrippers: Tiny Surgical Tools Perform Biopsies

Photo: Microgripper

A mu-gripper near the opening of an endoscopic catheter; © John Hopkins University/Evin Gultepe

By using swarms of untethered microgrippers Johns Hopkins engineers and physicians may have devised a new way to perform biopsies that could prove more effective to access narrow body conduits as well as find early signs of diseases.

The team reports successful animal testing of the tiny tools, which require no batteries, wires or tethers as they seize internal tissue samples. The devices are called "mu-grippers," incorporating the Greek letter that represents the term for "micro." These star-shaped tools are autonomously activated by the body's heat, which causes their tiny "fingers" to close on clusters of cells. Because the tools also contain a magnetic material, they can be retrieved through an existing body opening via a magnetic catheter.

The researchers describe their use of the mu-grippers to collect cells from the colon and esophagus of a pig, which was selected because its intestinal tract is similar to that of humans. Earlier this year, the team reported that they had successfully inserted the mu-grippers through the mouth and stomach of a live animal and released them in a hard-to-access place, the bile duct, from which they obtained tissue samples.

"This is the first time that anyone has used a sub-millimeter-sized device - the size of a dust particle - to conduct a biopsy in a live animal," said David Gracias, an associate professor of chemical and biomolecular engineering. "That is a significant accomplishment. And because we can send the grippers in through natural orifices, it is an important advance in minimally invasive treatment and a step toward the ultimate goal of making surgical procedures noninvasive." Physician Florin M. Selaru of the Johns Hopkins School of Medicine said the mu-grippers could lead to an entirely new approach to conducting biopsies, which are considered the "gold standard" test for diagnosing cancer and other diseases.

The advantage of the mu-grippers, he said, is that they could collect far more samples from many more locations. He pointed out that the much larger forceps used during a typical colonoscopy may remove 30 to 40 pieces of tissue to be studied for signs of cancer. But despite a doctor's best intentions, the small number of specimens makes it easy to miss diseased lesions.

"What is the likelihood of finding the needle in the haystack?" said Selaru. "Based on a small sample, you cannot always draw accurate inferences. We need to be able to do a larger statistical sampling of the tissue. That is what would give us enough statistical power to draw a conclusion, which, in essence, is what we are trying to do with the microgrippers. We could 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."

Although each mu-gripper can grab a much smaller tissue sample than larger biopsy tools, the researchers said each gripper can retrieve enough cells for effective microscopic inspection and genetic analysis. Armed with this information, they said, the patient's physician could be better prepared to diagnose and treat the patient.

MEDICA.de; Source: John Hopkins University