Scientists at ETH Zurich in Switzerland have unveiled a technique that weaponizes bacterial cells against tumors. The approach involves using bacteria called Magnetospirillum that are naturally magnetic by virtue of the iron oxide particles they contain. The researchers use a rotating magnetic field applied at the tumor location from outside the body to help draw the bacteria through gaps in the walls of tumor blood vessels. At present, the technique has been explored as a proof-of-concept, but in the future it may be possible to attach anti-cancer drug-loaded nanoparticles to the outside of the bacteria, turning them into living drug delivery vehicles. Researchers around the world are developing new and ingenious ways to deliver toxic anti-cancer drugs directly to tumors in the hope of maximizing efficacy and reducing off-target side-effects. These drug delivery vehicles are the tiny version of precision weapons, and this latest example is itself a living organism. Bacteria have previously been investigated as anti-cancer therapy, primarily in the hope that they could colonize a tumor and provoke a powerful immune reaction in the vicinity, potentially damaging the tumor in the process. While bacteria do have potential in this regard, this latest technology is a little more elegant and sophisticated. In this scenario, the bacteria are intended primarily as a means to deliver a conventional anti-cancer drug, but the main innovation comes in the means of achieving this targeting specificity – magnetic fields. Bacteria are not typically magnetic, with the exception of Magnetospirillum, which naturally contain iron oxide particles. The researchers realized that they could induce this bacterium to leave the blood stream and enter a tumor by using a rotating magnetic field. Whereas a static field would provide merely directional cues for the bacteria, a rotating field keeps them in constant movement against the blood vessel walls and increases the chances that a given bacterial cell will encounter a gap in the vessel that allows it to slip through into the tumor tissue beyond. Such gaps naturally and reversibly occur between endothelial cells in blood vessels, but moving about increases a bacterium’s chances of encountering one. So far, the researchers have trialed their approach in cancer cell spheroids, attaching dye-loaded liposomes to the outside of the bacteria and showing that they could successfully deliver it into the cells. The team also demonstrated that the technique can successfully increase the number of bacterial cells that accumulate in tumors in mice. Source
