Swarms of magnetic bacteria could be used to deliver drugs to tumors

One of the biggest challenges in cancer therapy is being able to deliver sufficient amounts of chemotherapy to tumor tissue without destroyin healthy tissues by the toxic effects. Researchers have attempted to address this through nanocarriers - small particles packed with drugs. Designed so they're only taken up by cancer cells, nanocarriers minimise exposure for healthy tissues.

Although nanocarriers protect healthy tissues, the amounts of drug delivered to tumor tissues remains low. This is because nanocarriers rely on the circulation system for delivery and amuch of it is filtered out of the body before reaching their destination. Also, differences in pressure between the tumor and surrounding tissue prevents nanocarriers from penetrating deep inside the tumor and fail to reach the tumor's hypoxic zones of active cell division.

Investigators have created a new delivery robot in the form of a bacteria called magnetococcus marinus or MC-1. MC-1 cells thrive in deep waters where oxygen is sparse. The bacteria rely on a two-part navigation system - a chain of magnetic nanocrystals within MC-1 that acts like a compass needle and sensors that allow the bacteria to detect changes in oxygen levels. This navigation system helps bacteria migrate to and maintain their position at areas of low oxygen.

In an initial experiment, mice that had been given human colorectal tumors were injected with either live MC-1 cells, dead MC-1 cells, or as a control group, non-magnetic beads (roughly the same size as the bacteria). The injection was made into the tissue directly adjacent to the tumors after which the mice were exposed to a computer-programmed magnetic field, meant to direct the cells or beads into the tumor. Upon examination of the tumors, the researchers found minimal penetration of the dead bacterial cells and the beads into the tumor, whereas the live bacterial cells were found deep within the tumor and especially in regions with low oxygen content.

This proof-of-concept work shows the potential to tap into the intricate and optimized cell machinery of single celled organisms such as bacteria. These bacteria are really the perfect machine. They replicate, they're cheap, and it is possible to inject hundreds of millions or more of particles at a time.

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Materials provided by National Institute of Biomedical Imaging and Bioengineering. Note: Content may be edited for style and length.