Microgrippers That Perform Cell Biopsies

Johns Hopkins University scientists have developed and successfully lab tested “microgrippers” that can be injected and remotely activated, using heat or certain chemicals, to grab onto unique cells.
From a Johns Hopkins press release:

The microgripper design — six three-jointed digits extended from a central "palm" — resembles a crab. (In fact, the joint design was inspired by that of arthropod animals.) To fabricate the microgrippers in their initial flat position with all digits fully extended, the researchers employ photolithography, the same process used to make computer chips. When the tiny devices are inserted in the body and moved magnetically, the gold-plated nickel in the palm and digits will allow doctors to see and guide the grippers with medical imaging units such as an MRI or CT.
The microgrippers’ grasping ability is rooted in the chemical composition of the joints embedded in the finger- like digits. These joints contain thin layers of chromium and copper with stress characteristics that would normally cause the digits to curl themselves closed like fingers clasping a baseball. But the researchers added a polymer resin, giving the joints rigidity to keep the fingers from closing.
When the microgrippers arrive at their destination, however, the researchers raise the temperature to 40 degrees C (or 104 degrees F, equivalent to a moderate fever in humans). This heat softens the polymer in the joints, causing the fingers to flex shut. The researchers also found an alternative method: Some nontoxic biological solutions can also weaken the polymer and cause the grippers to clamp down on their target.

In their lab experiments, the Johns Hopkins researchers used a microgripper, guided by a magnet, to grab and transport a dyed bead from among a group of colorless beads in a water solution. Team members also captured dozens of live animal cells from a cell mass at the end of a capillary tube. The cells were still alive 72 hours later, indicating the capture process did not injure them. Also, the microgrippers captured samples from relatively tough bovine bladder tissue.
The experiments showed that the tetherless microgripper concept is viable and has great potential for medical applications, the researchers said. Gracias’ team is now working to overcome some remaining hurdles. As currently designed, each biologically-compatible gripper can close on a target only once and cannot be reactivated to reopen and release its contents.

Hopkins press release with videos towards the bottom demonstrating the microgrippers: Wireless Microgrippers Grab Living Cells in ‘Biopsy’ Tests …
Images: Top: This fluorescent micrograph features a single microgripper with live cells within its grasp. The tetherless microgripper was triggered to close and capture these live fibroblast cells with thermobiochemical cues. Bottom: This optical microscopy image shows a tetherless microgripper holding on to a piece of bovine bladder tissue retrieved from a tissue sample placed at the end of a narrow glass capillary tube.