Researchers at Switzerland’s ETH Zurich have developed a groundbreaking approach to stroke treatment using microrobots. These tiny robots, which are not fully autonomous but are magnetically guided beads, could significantly improve the delivery of lifesaving medications to blood vessel blockages known as thrombi. This innovative method aims to enhance existing treatments that often require high doses of injectable drugs, which can pose serious risks, including internal bleeding.
Current stroke treatments typically involve administering medications that dissolve thrombi, but the vastness of the circulatory system complicates effective targeting. As a result, doctors often must use larger doses, increasing the chances of adverse side effects. The new microrobots, described in a recent study published in the journal Science, offer a potential solution by providing more precise delivery of medication.
The key to this technology lies in a soluble gel capsule that contains iron oxide nanoparticles, which allow the microrobots to be guided magnetically. According to Fabian Landers, a robotics researcher and study coauthor, the design of these capsules must balance size and magnetic properties due to the small dimensions of blood vessels in the human brain. “Because the vessels in the human brain are so small, there is a limit to how big the capsule can be,” Landers stated.
To enhance tracking capabilities, the team incorporated tantalum nanoparticles, enabling X-ray visualization of the microrobots as they navigate through the body. This extensive research has resulted in a magnetic microrobot capable of traversing the body’s approximately 360 arteries and veins. Bradley Nelson, another study coauthor, emphasized the advantages of using magnetic fields in minimally invasive procedures, noting that they penetrate deeply without causing harm.
Testing these microrobots began with artificial silicone models mimicking human and animal blood vessels. The specialized catheter used for injection features an internal guidewire connected to a polymer gripper that releases the microrobot. Navigating the system, however, is not straightforward. Nelson explained that “the speed of blood flow in the human arterial system varies a lot depending on location,” making guidance complex.
The researchers devised three distinct strategies to maneuver the microrobot through various arterial regions. They successfully guided the device at speeds of up to 4 millimeters per second using a rotating magnetic field. In another approach, a shifting magnetic field gradient enabled the microrobot to move against blood flow, achieving speeds of up to 20 centimeters per second.
Landers remarked on the challenge of maintaining control amid the high-speed flow of blood, stating, “Our navigation system must be able to withstand all of that.” Following successful laboratory demonstrations, the team proceeded to clinical tests using pigs. Remarkably, the microrobot delivered the thrombus medication to the correct destination in 95 percent of test scenarios.
The technology also showed potential in navigating a sheep’s cerebrospinal fluid, suggesting broader medical applications beyond stroke treatment. “This complex anatomical environment has enormous potential for further therapeutic interventions,” Landers added, expressing excitement about the microrobot’s performance in challenging conditions.
This innovative advancement in robotics and medicine holds promise for improving stroke treatment efficacy and reducing the risks associated with current therapeutic methods. With further development and testing, these microrobots could revolutionize the way medical professionals approach vascular blockages in the future.
