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Microrobot Swarm Breaks Up Bacterial Biofilms

Demonstration of CAR devices

Demonstration of CAR devices cleaning biofilms from surfaces (Geelsu Hwang and Edward Steager, University of Pennsylvania)

26 Apr. 2019. A medical-engineering team designed tiny robots that in lab tests remove large patches of bacterial communities called biofilms found growing on medical devices and human teeth. A description of the technology and test results appear in the 24 April issue of the journal Science Robotics (paid subscription required).

Researchers at University Pennsylvania’s dental and engineering schools seek to develop better techniques for dealing with the problem of biofilms, a scourge in medical facilities. Biofilms are communities of bacteria that connect and expand through a matrix of organic matter. These microbe colonies also stick tightly to surfaces, including medical devices and implants as well as human skin and teeth, making them difficult to treat, because of their persistence and ability to resist conventional antibiotics.

The UPenn team led by dentistry professor Hyun Koo and engineering researcher Edward Steager devised a solution with microscale robot devices that work together in groups to remove large swaths of biofilms. The researchers call their technology catalytic antimicrobial robots, or CARs, that degrade, kill, and remove biofilm communities as directed. The CAR devices are made of nanoscale iron oxide particles releasing free radicals, unstable atomic structures that bind to and cause oxidative stress, which breaks down nearby cells, in this case bacteria. The tiny robots also break up the organic sugar-like polymer that makes biofilms stick to surfaces.

“Existing treatments for biofilms are ineffective,” says Koo in a university statement, “because they are incapable of simultaneously degrading the protective matrix, killing the embedded bacteria, and physically removing the biodegraded products. These robots can do all three at once very effectively, leaving no trace of biofilm whatsoever.”

Koo, Steager, and colleagues created 2 types of CAR devices. Magnetically-driven CARs were arrayed like a plow that in tests on sample surfaces in the lab, completely and systematically removed large biofilm colonies, following the direction of an external magnet field. The researchers report the magnetic CARS completely eradicated the test biofilms and also prevented regrowth of the communities.

A second device is made from a gel-like polymer embedded with magnetic CARs. These devices are designed to work on curved surfaces and in tubes to remove biofilm clogs. And for a more practical test, the UPenn team tested the gel CAR devices with biofilms that form on human teeth. The tests arrayed CARS into a vane-shaped swarm — picture a cross placed over a circle — released on biofilms grown on discarded dental patients’ extracted teeth. The tests show the gel CARs can clean biofilms from teeth, including the isthmus, the narrow corridor between root canals where bacterial biofilms often form.

The next step in development is adding more intelligence to CAR devices. “We think about robots as automated systems that take actions based on actively gathered information,” notes Steager, adding “the motion of the robot can be informed by images of the biofilm gathered from microcameras or other modes of medical imaging.’

The university filed for a patent on the technology listing several authors as inventors. The researchers are also working with Penn Health-Tech, the university’s center for medical device innovation to advance the technology to commercialization.

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