Every year, around twelve million people worldwide suffer a stroke - often with deadly consequences or severe long-term impairments. An international research team from ETH Zurich with the participation of the Julius Maximilian University of Würzburg (JMU) has now developed a promising approach to deliver medications much more precisely to their site of action in the future: magnetically controllable microrobots. The results have been published in the prestigious journal Science.

The microrobot developed by the researchers is a tiny, spherical capsule made of a dissolvable gel shell equipped with iron oxide nanoparticles and tantalum nanoparticles. The iron oxide particles allow for precise magnetic control through the body, while tantalum serves as a contrast agent so that the capsule can be tracked using X-ray imaging. Especially in the highly sensitive and intricately branched vascular system of the brain, it was a major challenge to combine sufficient magnetic controllability with a minimal capsule size.

Micro-robots transport active substances

The microrobots can be loaded with various common active ingredients, including:

• a medication for dissolving blood clots (the FDA-approved enzyme tPA),

• an antibiotic,

• An active ingredient against tumors.

The active ingredients are released by a high-frequency magnetic field that heats the nanoparticles and selectively dissolves the gel shell. The critical aspect is the temperature range: the capsule must disintegrate without damaging the sensitive enzyme tPA. This is precisely where the work of the team led by Professor Tessa Lühmann at the Institute of Pharmacy and Food Chemistry at the University of Würzburg comes in. In comprehensive tests, the researchers examined the compatibility of the microrobots with biological systems, the activity of the enzymes, as well as their stability during storage and temperature increase.

Technology not only opens up new perspectives for stroke therapy, but also for the treatment of localized infections or tumors. The interdisciplinary team of materials science, robotics, and pharmacy has been driving the development from the beginning with a focus on clinical application in the operating room. The next step is now to prepare the path for clinical studies in humans - with the aim of making therapies more effective, safer, and with fewer side effects in the future.