Researchers are currently developing tiny biorobots made from living cells to perform a variety of tasks in the human body, from drug delivery to identifying cancer cells. In the latest development, researchers at Tufts University and Harvard University's Wyss Institute have successfully created a new type of biological robot using human tracheal cells.
Researchers have used human airway cells to create tiny biological robots that can move on their own and work together to promote the healing of damaged neurons without modifying genes. This tiny robot has the potential to transform regenerative medicine and disease treatment.
Previously, Tufts University collaborated with the University of Vermont to use frog embryonic cells to create a multi-cell biological robot called "Xenobot" that can navigate, record information and repair itself. At the time, researchers weren't sure whether these abilities were because the Xenobot was made from frog cells, or whether the biobot could be made from cells from other species.
In the current study, the researchers wanted to see if cells could be removed from their natural environment and reassembled into different "body plans" to perform other functions. They found that using adult human cells they could create robots that would be more capable without the need for genetic modification.
"We wanted to explore what cells can do besides creating default functions in the body," said Gizem Gumuskaya, first and corresponding author of the study. "By reprogramming the interactions between cells, new multicellular structures can be created, just as stones and bricks can be arranged into different structural elements such as walls, arches or columns."
They first extracted tracheal cells from the surface of human trachea and then developed a new protocol that exploits the existing abilities of bronchial epithelial progenitor cells to form multicellular spheroids with cilia, tiny hair-like structures that can vibrate and move. They modified this process to produce cilia-wrapped spheres; that is, the ciliated structures are on the outside of the spheres rather than inside.
Within days, the new cells, which the researchers call "Anthrobots," began to move, driven by cilia. The robots range in size from 30 microns to 500 microns when fully grown, and some are spherical and completely covered with cilia, while others are irregular or football-shaped and unevenly covered with cilia. The distribution of cilia determines how the robot moves, either looping or oscillating on straight or curved paths. Anthrobots typically survive in laboratory conditions for 45 to 60 days before degrading naturally.
"Anthrobots can assemble themselves in a laboratory dish," Gumuskaya said. "Unlike Xenobots, they don't require tweezers or scalpels to shape them, and we can use adult cells, or even cells from older patients, instead of embryonic cells. It's completely scalable -- we can produce swarms of these robots in parallel, which is a great start for developing therapeutic tools."
The researchers grew a layer of two-dimensional human neurons in a lab dish and then scratched the cells with a thin metal rod, creating a "wound" without cells. They placed a swarm of Anthrobots in a petri dish and watched them move across the surface of neurons. The robots promoted the growth of new cells, filling the gaps created by wounds and forming neuronal bridges as thick as healthy cells. In wounds without Anthrobots, neurons did not grow.
Michael Levin, another corresponding author, said: "The cell assemblies we created in the laboratory can have functions beyond their capabilities in the body. It is fascinating and completely unexpected that normal patient airway cells can move on their own and promote the growth of neurons in the damaged area without changing their DNA. We are now studying how this healing mechanism works and exploring what else these constructs can do."
One of the advantages of using human cells is the ability to use the patient's own cells to build robots that can complete treatments without triggering an immune response or needing to take immunosuppressants.
Further development of such robots could lead to other applications, such as clearing plaque buildup in arteries, repairing damaged spinal cord or retinal nerves, identifying bacteria or cancer cells, or delivering drugs to target tissues. In theory, Anthrobots could help heal tissue while delivering drugs that promote regeneration.
The research was published in the journal Advanced Science.