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A remote-controlled robot the size of a grain of sand can swim through blood vessels to deliver drugs before dissolving into the body. The technology could allow doctors to administer small amounts of drugs to specific sites, avoiding the toxic side effects of body-wide therapies.

The microrobots — guided by magnetic fields — work in blood vessels in pigs and sheep, researchers showed in a paper published in Science on 13 November¹.

The system has yet to be trialled in people, but it shows promise because it works in a roughly human-sized body, and because all its components have already been shown to be biocompatible, says Bradley Nelson, a mechanical engineer at Swiss Federal Institute of Technology (ETH) in Zurich, who co-led the work.

Around one-third of developed drugs that fail to come to market do so because they’re too toxic², says Nelson. The team says the microrobots would allow smaller amounts of drugs to be given directly to the affected areas, thereby reducing potential side effects. The technique could be used to target stroke-causing blockages or brain tumours.

“The demonstrations are compelling but still preclinical,” says Wei Gao, a medical engineer at the California Institute of Technology in Pasadena, whose team has developed an alternative robotic drug-delivery system. But if further studies proceed smoothly, remote-controlled drug-delivery robots could be used in the first medical applications within five to ten years, he says.

Robot-delivered drugs

Researchers have explored how to use tiny robots to deliver drugs for decades, including by steering them using ultrasound and using rotating devices that mimic bacteria.

The system developed by the ETH team involves filling a tiny bead of gelatine with a drug, as well as nanoparticles of magnetic iron oxide, which allows its movement to be controlled by magnetic fields surrounding the patient.

In trials in the brains of pigs and sheep, the team showed that they could use a catheter to insert the bots, before making them roll along the edges of blood vessels, swim against the flow or navigate with the stream at speeds as fast as 40 centimetres per second. They used X-ray images to observe and manoeuvre the bots in real time with millimetre-precision. In trials in pigs, the team showed that in more than 95% of cases, the drugs were delivered to the correct location.