Robotic white blood cells crawl against the current to deliver drugs
In the future, many diseases may be treated by tiny robots swimming through the bloodstream, delivering drugs. The latest test of these kinds of medical machines comes from researchers at the Max Planck Institute, who took inspiration from white blood cells to create a new micro-robot design that can move against the current of blood flow.
The robots are essentially glass microparticles, less than eight micrometers wide. One half is coated in a thin film of nickel and gold, while the other carries the drug payload. In this test, the payload was anti-cancer molecules as well as antibodies that recognize cancer cells.
Rather than swimming through the blood like other micro-robots, the new ones move by rolling along the walls of blood vessels, much like white blood cells do. The direction of this movement can be controlled from outside the body by way of a magnetic field. When switched on, the metal-coated side pulls the spheres in that direction.
The researchers tested them in simulated blood vessels in the lab, and found that the magnetic pull was strong enough to drag the robots against the current. When switched off, the robots simply go with the flow, potentially giving scientists precise control over where in the body the machines travel.
"Using magnetic fields, our micro-robots can navigate upstream through a simulated blood vessel, which is challenging due to the strong blood flow and dense cellular environment,” says Yunus Alapan, lead author of the study. “None of the current micro-robots can withstand this stream. Additionally, our robots can autonomously recognize cells of interest such as cancer cells. They do this thanks to a coating of cell-specific antibodies on their surface. They can then release the drug molecules while on the move.”
In these tests, the team clocked the robots at speeds of up to 600 micrometers per second, or 76 body lengths p/s. That makes them the fastest magnetic micro-robot of this scale.
The researchers say that swarms of these robots would be needed to make a difference in the human body. That’s because individual robots would be too small to see using most imaging techniques, and wouldn’t be able to carry enough of the drugs on their own.
While there’s still plenty of work to do to get them up to that stage, the team is hopeful that this technique would allow for non-invasive and precise treatment of a range of diseases and illnesses.
The research was published in the journal Science Robotics.