In my childhood, I especially loved watches that also had a small compartment with a different kind of arrow: red and blue. I loved the idea of a device that you always had with you that showed you the way. I would spin it around for hours to make sure the arrow always returned to the correct position after turning and a little thought. We humans need a compass in our watches. However, many organisms and animals have a compass in their bodies. One of the most notable examples is birds, which can travel thousands of miles without getting lost. However, since we are interested in biotechnology and its applications in medicine, perhaps we had better talk about unique bacteria that also have a kind of compass in their small organisms. 

Last time, I told you about a sophisticated system of bacterial immunity that scientists have exploited to develop a tool for genome editing. Today, I want to share another stunning scientific discovery that has also been used as a bioengineering tool. It is very interesting to even imagine that such systems exist on our planet. There are some bacteria, called magnetotactic bacteria, that have the unique ability to form chains of magnetic crystals of magnetite (Fe₃O₄) or greigite (Fe₃S₄) in their cells. These are so-called microoxyphilic bacteria. This means they need the amount of oxygen that is available in the middle layer of water: not too deep because there is too little oxygen, and not too shallow because there is too much of it. Magnetotactic bacteria use planet Earth’s magnetic field to navigate through the water depth and settle in the most optimal spot using their internal compass- crystals of magnetite or greigite. Scientists extract these magnetic particles from bacteria or synthesize in a chemical lab and use them according to various biotechnological needs. And there are numerous applications for magnetic nanoparticles in biotechnology. The most notable are the delivery systems, cell separation tools and oncological treatment.

Delivery systems can be distinguished between in vivo applications for drug delivery and in vitro applications for biotechnological processes. Targeted drug delivery is achieved by coupling the magnetic nanoparticles with some ligands of cell surface receptors expressed on the specific cell types we want to target. By using the magnetic field, scientists can enhance the accumulation and storage in a specific tissue. We can also use magnetic particles to introduce genome editing tools into hard-to-transfect cell lines such as fibroblasts, or even in vivo for the treatment of some cancers (3)

Hyperthermia therapy for cancer treatment. In terms of cancer treatment, researchers have also proposed an interesting approach called local hyperthermia. The idea is to accumulate magnetic nanoparticles in the tumor and then generate hyperthermia to damage the cancer cells by applying a rapidly changing magnetic field. An even more efficient approach has been proposed to use local hyperthermia in conjunction with conventional chemotherapeutic approaches by combining magnetic nanoparticles and chemotherapeutic agents such as doxorubicin in a liposomal structure (4). Although this approach may be very promising from the perspective of tumor destruction, the efficiency of magnetic particle delivery in vivo is quite low. Only about 1% of magnetic particles can reach the tumor via the bloodstream (5)

So today, not only have we learned that some bacteria can produce small magnetic crystals in their bodies to deal with the Earth’s magnetic field, but also that researchers are trying to harness these magnetic particles for their own benefit. Specifically, to enhance the delivery of various molecules to target tissues or to destroy tumors by bringing the nanoparticles inside the tumors, moving the particles in a rapidly alternating magnetic field, and thus heating the tumor. If that’s not fascinating, what is?