Microscopic robots—no larger than blood cells—are being developed to swim through the human body and deliver targeted medical treatments. Remarkably, these tiny machines are built from algae.
Researchers have made significant progress in creating so-called “biohybrid” microrobots using spirulina, a spiral-shaped algae commonly sold as a dietary supplement in health food stores. By engineering these natural cells with magnetic particles, scientists have transformed them into steerable medical delivery systems.
After coating the spirulina with iron oxide, the research team made the algae magnetic. This allows external magnets to guide their movement through biological environments. In laboratory tests, scientists successfully steered the algae microrobots inside the body of a rat, directing them to swim toward specific locations.
Because the algae are biodegradable, they break down naturally and pose no long-term harm to the body—an important advantage over many synthetic microdevices.
The technology opens the door to new medical possibilities. Many areas of the human body remain difficult to access using conventional drug delivery methods, including portions of the nervous system and the back of the eye. Traditional medicine often relies on passive distribution through the bloodstream—similar to a ship drifting without propulsion. Biohybrid microrobots, by contrast, could actively navigate to precise targets.
The research team, led by Li Zhang at the Chinese University of Hong Kong, developed the microrobots by bathing the algae in iron oxide nanoparticles. Using magnetic fields, they can control the direction and movement of entire swarms.
An additional advantage is visibility. The algae possess natural fluorescence, allowing researchers to track their position from outside the body using imaging technologies.
“Rather than fabricate a functional microrobot from scratch using intricate laboratory techniques and processes, we set out to directly engineer smart materials in nature, which are endowed with favorable functionalities for medical applications owing to their intrinsic chemical composition. For instance, because these biohybrid bots have a naturally fluorescent biological interior and magnetic iron-oxide exterior, we can track and actuate a swarm of those agents inside the body quite easily using fluorescence imaging and magnetic resonance imaging.”
— Professor Zhang.
In experimental trials, the team demonstrated that the microrobots could be used to kill cancer cells in rats. Looking ahead, researchers envision attaching therapeutic drugs to the algae robots and guiding them directly to tumors—potentially enabling highly targeted cancer treatments capable of locating and destroying malignant cells throughout the body.
Reference:
Xiaohui Yan et al. Multifunctional biohybrid magnetite microrobots for imaging-guided therapy. DOI: 10.1126/scirobotics.aaq1155