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Crab-Shaped Device Has Firm Grip on Cells


R&D Digest
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A fluorescent micrograph shows the microgripper holding onto live fibroblast cells. (Photos courtesy of T.G. LEONG AND C.L. RANDALL)
New tools called microgrippers are being developed to aid surgeons in navigating complicated regions in the body. Although the devices need more work before being used on humans, they could be used to pick up and move cells via thermal or biochemical signals.

“This is an important first step toward creating a new set of biochemically responsive and perhaps even autonomous micro- and nanoscale surgical tools,” says David Gracias. “[It] could help doctors diagnose illnesses and administer treatment in a more-efficient, less-invasive way.” Gracias is assistant professor of chemical and biomolecular engineering at Johns Hopkins University.

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A microgripper grasps a sample from bovine bladder tissue.
The 0.1-mm-diameter microgripper, about the size of a dust particle, looks like a crab. Similar to the construction of computer chips, researchers used photolithography to make the microgrippers flat with fully extended digits. Each of the three-jointed digits (six total) are thinly layered with chromium and copper. The layers create stress attributes that cause the digits to curl shut. However, the researchers used a polymer resin to make the joints rigid, preventing them from closing.

To operate the microgrippers, a user employs magnets to move the microdevice from outside the body. Because the microgripper is plated with gold, doctors can use medical imaging to view and guide it to the point of interest. Once the device is at its target, its temperature is raised to 104°F, causing the polymer in the joints to soften and the fingers to close. One current limitation to the device is that it can only close on a target once, and won't reopen.

The researchers have tested the microgripper on animal cells to perform a procedure similar to a biopsy. They also guided the device with a magnet to grasp and move a dyed bead from a group of colorless beads in water. The experiments revealed that the process of capturing animal cells didn't injure the cells, because those cells were still alive after 72 hours.

The work shows that the microtool can be used in difficult parts of the anatomy without any wires or tubes. Gracias wants to team up with medical researchers who can help in the development of the device for performing a biopsy and delivering drugs in humans.

Johns Hopkins's technology transfer staff has obtained a provisional patent on the device. Research funding has been provided by the National Science Foundation, the Dreyfus and Beckman Foundations, and the National Institutes of Health, which gave Gracias a $1.5 million New Innovators Award last September. More information about the device can be found in a January online edition of Proceedings of the National Academy of Sciences. Gracias hopes to use the grant to develop mobile micro- and nanosurgical tools.

Copyright ©2009 Medical Device & Diagnostic Industry
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