Gripper microbots help perform live biopsy

Developed by engineers and physicians at Johns Hopkins University, the untethered grippers - dubbed mu-grippers - could provide a more effective way to access narrow conduits in the body.

Although each mu-gripper can grab a much smaller tissue sample than larger biopsy tools, the researchers - including David Gracias and Florin M. Selaru - said in a statement that 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.

This approach would be possible through the latest application of the Gracias lab’s self-assembling tiny surgical tools, which can be activated by heat or chemicals, without relying on electrical wires, tubes, batteries or tethers.

The low-cost devices are fabricated through photolithography and their fingerlike projections are made of materials that would normally curl inward, but the team added a polymer resin to give the joints rigidity and to keep the digits from closing.

Prior to a biopsy, the grippers are kept on ice, so that the fingers remain in this extended position. An endoscopy tool then is used to insert hundreds of grippers into the area targeted for a biopsy. Within about five minutes, the warmth of the body causes the polymer coating to soften, and the fingers curl inward to grasp some tissue. A magnetic tool is then inserted to retrieve them.

‘This is the first time that anyone has used a sub-millimetre-sized device—the size of  a dust particle—to conduct a biopsy in a live animal,’ said Gracias, an associate professor of chemical and biomolecular engineering. ‘That’s 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 non-invasive.’

In two recent peer-reviewed journal articles, the team reported successful animal testing of the tiny tools.

In the journal Gastroenterology, the researchers described their use of the mu-grippers to collect cells from the colon and oesophagus of a pig, which was selected because its intestinal tract is similar to that of humans.

Earlier this year, the team members reported in the journal Advanced Materialsthat they had successfully inserted the mu-grippers through the mouth and stomach of a live animal and released them into the bile duct, from which they obtained tissue samples.

Although the animal testing results are promising, the researchers said the process will require further refinement before human testing can begin.

‘The next step is improving how we deploy the grippers,’ said Selaru of the Johns Hopkins School of Medicine. ‘The concept is sound, but we still need to address some of the details. The other thing we need to do is thorough safety studies.’