At first glance, the biology of magnetic, underwater-dwelling, oxygen-averse bacteria may seem of little relevance to our most pressing human health problems. But science is full of surprises. A paper published this week in Nature Nanotechnology presents an inspired use of these bacteria to deliver anti-cancer drugs to tumors, specifically targeting the oxygen-starved regions generated by aggressively proliferating cells.
The authors, Ouajdi Felfoul et al of the Université de Montréal, Polytechnique Montréal and McGill University, devised a drug delivery system using marine bacteria to propel drugs into the inaccessible, oxygen-starved heart of tumors in mice. The method was designed to address some of the limitations associated with existing nanocarrier drug delivery systems—namely, dependence on the circulation, lack of a propelling force to penetrate tumors, and the absence of a mechanism for sensing and targeting the tumor hypoxic zone.
Magnetotactic bacteria are so-named because they move directionally along a magnetic field. Magnetic minerals deposited within the bacterial cell are responsible for this magnetism. The marine bacteria used in the Nature Nanotechnology paper, Magnetococcus marinus, use a process known as magneto-aerotaxis to find their way to the low-oxygen environments of their natural habitat. It is an organism that appears tailor-made for the problem at hand—finding and delivering drugs to the low-oxygen environment of proliferating tumors.
The authors demonstrated that the bacteria could be guided to tumor sites in mice using a computer-controlled external magnetic field, and that once within the tumor environment they were able to move towards low-oxygen zones. Liposomes containing anti-tumor drugs were then covalently attached to the bacterial membranes, and were delivered effectively to colorectal tumors in a mouse model system.
Magnetococcus marinus. Who knew that this obscure, microscopic bottom-dweller held such useful secrets? Imagine what else could be out there waiting to be found, or what may be hiding in plain sight, waiting for someone to notice.
Here’s the paper:
Felfoul, O. et al. Magneto-aerotactic bacteria deliver drug-containing nanoliposomes to tumour hypoxic regions. Nature Nanotechnology, doi:10.1038/nnano.2016.137, 15 August 2016.
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