Researchers at ETH Zurich in Switzerland have developed innovative microrobots designed to combat strokes by navigating the human circulatory system. These tiny, magnetically guided beads are not fully autonomous; instead, they are equipped with lifesaving medications and small amounts of a radioactive tracer to allow doctors to monitor their journey through the blood vessels.
Current treatments for stroke often involve high dosages of injectable drugs to dissolve blood clots known as thrombi. This method poses risks, including serious side effects like internal bleeding due to the necessary volume of medication. The new microrobots may change that landscape significantly.
Innovative Design Overcomes Technical Challenges
The research team, led by Fabian Landers and Bradley Nelson, details their findings in the journal Science. They have created a soluble gel capsule powered by iron oxide nanoparticles, which allows for magnetic guidance. According to Landers, “Because the vessels in the human brain are so small, there is a limit to how big the capsule can be. The technical challenge is to ensure that a capsule this small also has sufficient magnetic properties.”
To enhance tracking, the researchers incorporated tantalum nanoparticles, enabling X-ray tracing. After years of experimentation, they achieved a microrobot capable of navigating the human body’s approximately 360 arteries and veins with high precision.
Magnetic fields play a crucial role in this process. Nelson explains, “Magnetic fields and gradients are ideal for minimally invasive procedures because they penetrate deep into the body and–at least at the strengths and frequencies we use–have no detrimental effect on the body.”
Testing and Promising Results
The effectiveness of these microrobots was assessed using a specialized catheter to inject them into artificial silicone models mimicking human and animal blood vessels. This catheter features an internal guidewire linked to a polymer gripper that releases the microrobot upon reaching the correct location.
Navigating the circulatory system is complex due to varying blood flow speeds. To address this, the team developed a guidance system that employs three strategies. Using a rotating magnetic field, they successfully maneuvered the microrobot at speeds of up to 4 millimeters per second. In another model, a shifting magnetic field gradient assisted the device in moving against the 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,” noted Landers. “Our navigation system must be able to withstand all of that.”
Following successful lab demonstrations, the researchers progressed to animal testing, specifically using pigs. In 95 percent of trials, the microrobot effectively delivered thrombus medication to the intended site, showcasing its potential for broader medical applications. The procedure also yielded promising results in a sheep’s cerebrospinal fluid, indicating versatility in treating various conditions.
“This complex anatomical environment has enormous potential for further therapeutic interventions, which is why we were so excited that the microrobot was able to find its way in this environment, too,” Landers added.
As advancements in medical technology continue to emerge, the development of these microrobots represents a significant step forward in improving stroke treatment and enhancing patient safety. The research not only highlights the potential for innovative solutions in addressing medical challenges but also opens doors for future applications in other areas of medicine.
