Scientists have managed to successfully create a biohybrid robot that has the potential to carry drugs to specific parts of the body, minimising side effects. 

According to Science, by manipulating spirulina, a microscopic plant and food supplement, to travel through people in response to magnetic signals, the robot even appears to kill cancer cells. 

Although researchers have already managed to build bots out of rods, tubes, spheres, and even cages no bigger than a cell, it was outfitting the tiny devices with a power supply that caused the issues, largely due to potential fuels being toxic to humans. 

In addition, steering a microrobot through the body’s maze of proteins and other molecules, requires both a way to control its movements and to see where it is. 

In an attempt to overcome this, Liz Zhang, a materials scientist at the Chinese University of Hong Kong in Shatin, turned to magnetism, and living organisms. This is because magnetic fields created outside the body can penetrate living tissue without harm allowing mobility, a helical body propelled by twirling works best. 

Peer Fischer, a physical chemist at the Max Planck Institute for Intelligent Systems in Stuttgart, Germany, explained, “It’s surprising that you can find in nature such a convenient structure and that it can behave so nicely.”

The scientists realised that they needed a way to track the robot in the body, and the alga produces a fluorescent glow. The researchers wondered whether they could follow the robot’s course near the body surface by detecting this fluorescence, and then use a medical imaging technology, called nuclear magnetic resonance (NMR) to track it in deeper parts of the body. This works by detecting magnetic particles given to a patient before the imaging takes place. 

The scientists developed a one-step method to magnetise the alga, coating millions of spirulina with iron oxide nanoparticles. A longer dip time allows for more control, but a short dip time allows researchers to detect the fluorescence more readily. When the bot is too deep for that technique to work, NMR can still follow the robot’s course because of the coating. 

Joseph Wang, a nanoengineer at the University of California, San Diego, who is developing a different sort of medical microbot, said, “It’s a step forward that you can track these swimmers in the body, and it’s biocompatible and low cost.”

The biocompatibility is an important feature, largely because the microrobot degrades in hours or days, depending on how thick the coating is; yet it doesn’t damage most cells. The one exception in this is cancer cells, approximately 90% of which were destroyed after tumour cells growing in a lab dish were exposed to the spirulina for 48 hours. 

Despite the progress, there’ still a long way to go for the half-dozen teams around the globe who are developing microrobots. Wang concluded that he thinks it might be ready in about another ten years. 

“It’s still not ready for a doctor to use. Everyone wants to realise this fantastic voyage.”