Magnetic-driven bacteria get drugs deep into tumors

Researchers at the Polytechnique Montreal NanoRobotics Laboratory have found that bacteria imbued with magnetic capabilities can be a way to deliver targeted loads of chemotherapy to tumors with fewer side effects.

Many nanocarriers reach a tumor via the circulatory system to disburse their payloads, but this kind of passive delivery doesn’t allow them to penetrate a tumor in a way that some of the tumor’s most active parts remain intact. These are the tumor’s hypoxic zones and are thought to be the source of metastasis, and they are also known to have less oxygen than surrounding areas.

Scientists are relying more and more on self-propelled nanocarriers, and that’s what led the PMNL researchers to a bacterium called Magnetococcus marinus, which lives in deep waters with little oxygen. The bacteria have adapted to the environment with magnetic nanocrystals that act like a compass guiding them north, as well as oxygen sensors that lead them to the deeper waters.

These bacteria, led to a tumor using a programmed magnetic field, burrowed deep within to “find” the hypoxic zones. The researchers attached drug vesicles to each bacteria cell, and 55% of the injected bacterial cells made it to the tumor. Normally, only about 2% of drugs make it inside.

“When they get inside the tumor, we switch off the magnetic field and the bacteria automatically rely on the oxygen sensors to seek out the hypoxic areas,” lead researcher Sylvian Martel said. “We constrain them to the tumor and then let nature do the rest.”

The scientists, who published their results in the journal Nature Nanotechnology, next plan to test their drug-loaded bacteria for their effect on tumor size.

"This proof-of-concept work shows the potential to tap into the intricate and optimized cell machinery of single-celled organisms such as bacteria," said Richard Conroy of the National Institute of Biomedical Imaging and Bioengineering, a major funder of the study. "The ability to actively and precisely target drug delivery to a tumor will help reduce side effects and potentially improve the efficacy of treatments."