Microrobots have learned how to deliver drugs directly to blood clots

Each microrobot is a tiny spherical capsule with a gel shell. Inside there are magnetic iron oxide nanoparticles that allow the robot to be controlled using an external magnetic field. Tantalum nanoparticles, a contrast agent, have also been added, thanks to which doctors can see the movement of the robot on an X—ray.

The size of the capsule is designed so that it can move through the thinnest vessels of the brain. This has become a serious technical challenge: the microrobot must be both very small and magnetic enough to respond to external control.

Different types of medications can be placed inside the capsule, from thrombolytics to antibiotics and anticancer drugs. Once at the right point, the microrobot warms up under the influence of a high-frequency magnetic field, its shell dissolves, and the drug is released right on the spot.

A special catheter is used to enter the body, which delivers the microrobot into the bloodstream or cerebrospinal fluid. After that, electromagnetic navigation is activated, a system created that can guide the capsule even against strong blood flow.

The team has developed three movement strategies:

• rolling mode — a rotating magnetic field rolls the capsule along the vessel wall;
• moving along the field gradient — the robot moves to where the magnetic field is stronger, and can even go against the current;
• flow navigation — the magnet sets the direction so that the capsule is carried away to the desired branch of the branching vessel.

In 95% of the trials, the microrobot successfully reached the target and delivered the medicine.

To test the technology, the specialists created ultra-precise silicone vessel models that completely replicate the anatomy of a real patient. Microrobots successfully dissolved artificial blood clots on them. Then the technology was tested on animals: in pigs — in a complex system of arteries, in sheep — in cerebrospinal fluid. In both cases, the system worked as accurately as in the laboratory.

In addition to eliminating blood clots, microrobots can be useful for treating local infections or tumors in cases where targeted drug delivery is especially important.