Paolo Rossi Castelli 27 December 2020 8 min read

Magnetic bacteria for super-precise anti-cancer treatments

A team from ETH Zurich is studying a new way, with an added element of science fiction, to make anti-cancer drugs reach the right point inside the body of cancer patients, with extreme precision, increasing their effectiveness and reducing the damage to healthy cells.

This technique involves the use of magnetic bacteria, as the researchers explain in the scientific journal Advanced Functional Materials.

So, what is it all about?

Magnetic bacteria were discovered in the depths of the sea 45 years ago. They absorb iron dissolved in water and, after a series of metabolic reactions, transform it into iron oxide crystals forming a line one after the other. In this way, each bacterium turns into a sort of compass needle and, like a compass needle, aligns with the Earth’s magnetic field and manages its “path”.

Professor Simone Schürle, from the Department of Health Sciences and Technology at the ETH in Zurich, came up with the idea of artificially orienting the magnetic field around these bacteria, using sophisticated technology to direct them (with a “load” of drugs) towards the desired target, i.e. the tumor, inside the patient’s body.

Such an undertaking however, in practice, is far from easy….

To start with, Professor Schürle and her team looked for a way to control the movement of magnetic bacteria in a special liquid, recreated within the laboratory. In particular, in early tests, they applied weak magnetic fields to make the bacteria rotate in specific directions. Then, in subsequent experiments, they were able to gather a large number of bacteria in a kind of swarm and make them “drag” small amounts of the liquid in which they were swimming along with them, including substances found in the liquid itself.

In a nutshell, the researchers managed to make the bacteria work like micro-pumps. And it is this mechanism that could be used in the body of patients in the future. A mechanism to carry drugs from the bloodstream to cancer tissue in very specific areas with millimetre precision.

One of the advantages of this approach – which forms part of what is known as living therapies (i.e. therapies that use live microorganisms) – is the fact that ferromagnetic bacteria can be “grown” easily and in large quantities.

However, before conducting experiments on patients, of course, all the characteristics of the chosen bacterial species need to be determined and all types of toxicity need to be excluded, for example by deactivating several functions, as is the case for vaccines.

Alternatively, synthetic bacteria could be used, i.e. bacteria made using genetic engineering that would only have the characteristics required by the researchers.

But there are also other possible developments of anti-cancer therapies using bacteria. It has been known for years that some types of anaerobic microorganisms (ones that do not require oxygen to grow) – different from those used by the ETH Zurich – tend to accumulate in certain types of tumours that are hardly reached by blood vessels, for various reasons (as these tumours do not receive a lot of blood, they also receive a low number of drugs and prove to be more resistant).

Using genetic engineering could, in fact, create anaerobic bacteria that are able to reach these “difficult” tumours, but also to respond to external magnetic fields, prompted by oncologists.

Science fiction? Some researchers believe that this could become reality in just a few years.


Paolo Rossi Castelli

Journalist since 1983, Paolo has been dealing with scientific divulgation for years, especially in the fields of medicine and biology. He is the creator of Sportello Cancro, the site created by on oncology in collaboration with the Umberto Veronesi Foundation. He collaborated with the pages of the Science of Corriere della Sera for several years. He is the founder and director of PRC-Comunicare la scienza.