3D-Printed Microbots Deliver Drugs by Navigating Arteries and Veins

The titanium microbots could one day provide a minimally invasive method for delivering therapies in humans.

Time-lapsed images of the mesenchymal stem cell-cultured microrobot moving in the yolk of a zebrafish embryo. | Li et al., Sci. Robot. 3, eaat8829 (2018)
Time-lapsed images of the mesenchymal stem cell-cultured microrobot moving in the yolk of a zebrafish embryo. | Li et al., Sci. Robot. 3, eaat8829 (2018)

Medical researchers in Hong Kong this week unveiled a drug delivery system in which microscopic robots crawl through arteries and veins carrying medicines to specific tissues in the body.

The tiny bots are inserted into the bloodstream with a syringe and directed by remote control using external magnetic fields. While similar microbot systems have been developed elsewhere, the new procedure is the first to deliver cells to a specific site and autonomously release their payload in living animals, according to a research team at City University of Hong Kong.

Although still in development, researchers said the technique could eventually be used in clinical applications for remote drug delivery or cell therapy in humans. The research was published June 27 in the journal Science Robotics.

Lead researcher Yunyang Li and colleagues first began developing the microbots by using computer models to see which shapes move most efficiently when navigating veins and arteries. They discovered that porous, burr-shaped bots did the best job at generating traction against blood vessel walls and dealing with the viscosity of different blood types.

The microbots were then designed and molded using 3D printing and coated with nickel to provide magnetism. An outer coating of titanium was also applied to improve biocompatibility.

In a series of tests, the microbots were injected into zebrafish embryos and guided to the desired target location using external electromagnetic coils. The bots were able to deliver their payload of therapeutic cells without harming the embryos.

In a subsequent set of tests, the researchers injected microbots carrying tagged fluorescent cells into mice. The target site later glowed with fluorescence, indicating that the cells were delivered to the proper location — and stayed where they were supposed to.

The microrobots with fluorescent HeLa cells were injected into the left dorsum of the nude mice. After four weeks of cultivation, an area with increased fluorescence intensity was observed at the left dorsum of the mouse (indicated by the white arrow), indicating that the tumor was due to the release of HeLa cells from the microrobots. | Li et al., Sci. Robot. 3, eaat8829 (2018)

Additional testing revealed that the system can be used to deliver embryonic stem cells and connective tissue cells.

The results suggest the technique could eventually be used to develop minimally invasive delivery methods for existing therapies in humans.

The team plans, according to press materials released in conjunction with their research results, to further refine the microbot system for eventual clinical applications. They hope to make future robots from fully biodegradable materials and to develop better imaging technology for tracking the lil' bots as they crawl through our plumbing.