Scientists looking to harness the cancer-fighting capabilities of bacteria have made an impressive advance, demonstrating how magnetic forms of the microorganisms can be propelled into tumors. This in itself is a promising breakthrough, but through advanced engineering techniques, the team behind the technology hope to supercharge its anti-tumor effects even further.
The study was carried out at ETH Zurich in Switzerland and builds on previous work that demonstrated Magnetospirillum bacteria, which naturally contain iron oxide particles, can be controlled by magnetic fields. In 2020, the scientists used this technique to control the flow of liquids surrounding the bacteria in the laboratory, effectively turning them into magnetic micropumps.
This raised the possibility of using them to deliver drugs in the body, by steering them to the desired location in the bloodstream. But exiting the bloodstream and entering tumor tissue isn’t like hopping off of a train. The walls of blood vessels are densely packed barriers made up of cells, and only by squeezing through the narrow but fluctuating spaces in between those cells can certain molecules make it through.
The scientists injected Magnetospirillum bacteria into mice and with a rotating magnetic field, showed that they could bolster their ability to sneak through these temporary gaps in the vessel walls. This enabled them to enter the tumor and from there, the bacteria were able to travel into the tumor of their own accord.
“We make use of the bacteria’s natural and autonomous locomotion as well,” said Simone Schürle, who led the study. “Once the bacteria have passed through the blood vessel wall and are in the tumor, they can independently migrate deep into its interior.”
In cell culture experiments, the team attached small spheres of fatty substances called liposomes to the bacteria. This was designed to simulate how the technology could work as a drug delivery method, in which the cargo would be loaded into the liposomes and released in the tumor. These experiments showed that the bacteria successfully carry these liposomes into cancerous tissue.
Using bacteria as vehicles for cancer drug delivery is an idea we’ve seen explored elsewhere, also with promising results. Earlier this year, a team at Columbia University demonstrated a form of engineered bacteria that could hide from the immune system long enough to produce an anti-tumor toxin, shrinking tumors in mouse models. Schürle holds similar aspirations.
“We believe we can use our engineering approach to increase the efficacy of bacterial cancer therapy,” she says.
The possibilities include engineering forms of E.coli, which is not magnetic but is currently being studied as a therapeutic bacteria for cancer treatment. If it could be made magnetic, magnetic fields could be used to send it toward tumors deep inside the body to unleash anti-cancer effects.
The research was published in the journal Science Robotics.
Source: ETH Zurich
