Researchers at Switzerland’s ETH Zurich have developed a novel approach to combat strokes using microrobots that navigate the human circulatory system. These tiny, magnetically guided beads are designed to break down blood vessel blockages, known as thrombi, which can lead to serious health risks. Unlike traditional injectable drugs that require high dosages, this method aims to deliver targeted medication with greater precision.
Current treatments for stroke patients often involve injecting drugs that dissolve thrombi. However, the vastness of the circulatory system necessitates large doses to ensure effectiveness, increasing the risk of serious side effects, including internal bleeding. The innovative microrobots offer a potential solution by reducing the dosage needed while enhancing delivery accuracy.
Fabian Landers, a robotics researcher and coauthor of the study published in March 2023 in the journal Science, explained the technical challenges involved in creating such small capsules. “Because the vessels in the human brain are so small, there is a limit to how big the capsule can be,” he noted. To overcome these challenges, the team infused a soluble gel capsule with iron oxide nanoparticles for magnetization. Additionally, nanoparticles of tantalum were introduced for X-ray tracing to monitor the microrobots’ journey through the body.
The researchers have successfully created a magnetic microrobot capable of navigating the human body’s approximately 360 arteries and veins. Coauthor Bradley Nelson emphasized the advantages of magnetic fields for minimally invasive procedures: “They penetrate deep into the body and have no detrimental effect at the strengths and frequencies we use.”
To test their microrobots, the research team utilized a catheter to inject the devices into artificial silicone models simulating human and animal blood vessels. The specialized catheter features an internal guidewire linked to a polymer gripper designed to release the microrobot. This process is not straightforward, however, as blood flow speeds vary significantly throughout the arterial system.
Navigating these challenges requires a sophisticated guidance system that employs three distinct strategies to maneuver through various arterial regions. Using a rotating magnetic field, the team was able to guide the microrobot at speeds of up to 4 millimeters per second. In other tests, a shifting magnetic field gradient enabled the microrobot to travel against the blood flow, achieving speeds of up to 20 centimeters per second.
“It’s remarkable how much blood flows through our vessels and at such high speed,” Landers commented. The successful lab results prompted the team to conduct clinical tests on pigs, where the microrobot successfully delivered thrombus medication to the correct destination in 95 percent of scenarios.
The microrobots also showed promise in accessing cerebrospinal fluid in sheep, suggesting their potential for a wide range of medical applications. Landers expressed enthusiasm about the results, stating, “This complex anatomical environment has enormous potential for further therapeutic interventions.”
As research in this field continues, the development of these microrobots may revolutionize stroke treatment, offering a safer and more effective alternative to existing methods. With ongoing advancements, researchers aim to further refine this technology, paving the way for future medical innovations.
