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Drug Delivery

Video: Microrobots roll against blood flow to deliver drugs

With the help of magnetic fields, the bots might one day navigate the circulatory system to target tumors

by Tien Nguyen, special to C&EN
June 16, 2020


Credit: Sci. Robot./Tien Nguyen

Drug-carrying microrobots offer a way to deliver treatments straight to where they are needed, such as tumors deep within the body. But most bots designed in labs have so far been limited to easy-to-reach targets such as the gut. Now, researchers have developed drug-delivering “microrollers” that can move against blood flow (Sci. Robot. 2020, DOI: 10.1126/scirobotics.aba5726). With the help of a magnetic field, these two-faced particles might one day navigate our circulatory system to deliver treatments to tumors. The microrollers are coated on one side with magnetic materials and on the other with antibodies specific to cancer cells. These antibodies would help the particles selectively bind to tumors in the body, where they could release their payload. This targeted approach could minimize exposure of healthy cells to cancer drugs, reducing side effects.

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The following is the script for the video. We have edited the interviews within for length and clarity.

Tien Nguyen: This is a tiny microrobot fighting its way against blood flowing in an artificial vein. The scientists who designed these bots imagine them cruising the bloodstream, carrying cancer-killing drugs to treat difficult-to-reach tumors deep inside the body. This approach to drug delivery would minimize the exposure of normal, healthy cells to toxic chemotherapy drugs, thus avoiding side effects. So says Metin Sitti, who helped to create the bots.

Metin Sitti: Our goal of using microrobotic approach is to localize the cancer drugs to only tumor regions so there is no side effects.

Tien Nguyen: The team calls these bots “microrollers” because they could navigate blood vessels by rolling along their walls. By sticking to the walls where blood flow is slower with the help of a magnetic field, the microrollers could move against the bloodstream, which has been a challenge for bots of this size.

The microrollers have two faces, each with a specific job. One side is needed for navigation, and it’s made of magnetic gold and nickel layers. This face allows researchers to control the microbot’s movement by flipping on a weak external magnetic field. By changing the direction of the magnetic field, the team can change the direction of the bots’ movements, with speeds up to 600 μm/s. The researchers could even steer the bots through junctions, like those the microrollers would encounter in an actual circulatory system.

The other face of the bots is critical for attacking tumors. This face is equipped with antibodies and cancer drug molecules. The antibodies bind to proteins found specifically on breast cancer cells. This allows the bots to stick to the tumor cells while passing by healthy skin cells shown at the bottom of the screen. Once the bots reach a tumor, researchers could zap them with UV light to trigger a chemical reaction that releases the cancer drug payload. But prolonged UV exposure can damage healthy cells, so Sitti says his team is working on other ways to release the drug such as using a change in temperature.


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