There is no shortage of effective chemotherapeutic drugs available to doctors in the fight against prostate and other cancers. The trick has always been getting them into the cancerous tumors without making the nearby tissues toxic.

The latest delivery vehicle has just arrived on the scene in the unlikely form of magnetic bacteria.

Now, we have played this course before, with so-called nano-carriers.  These are microscopically small mechanisms, packed with drugs, designed to travel along in the bloodstream. The tiny delivery trucks are coded in such a way that they are only taken in by cancer cells.

It's a great system in theory, but the trek through the bloodstream is so tortuously long that unfortunately a large percentage are filtered out of the body before ever getting a chance to drop off their payload. Worse yet, the pressure differential between the tumor and the surrounding tissues prevent the carrier from getting very deep into the tumor's low-oxygen zones – areas of active cell division inside the tumor – which is where most of the cancer's bad actors live.  Researchers estimate that only approximately 2 percent of drugs delivered via the nano-carriers make it into tumors.

“Only a very small proportion of drugs reach the hypoxic zones, which are believed to be the source of metastasis. Therefore, targeting the low-oxygen regions will most likely decrease the rate of metastasis while maximizing the effect of a therapy,” says Sylvain Martel, PhD, Director of the Polytechnique Montréal NanoRobotics Laboratory and lead researcher of the study, and the data was published in Nature Nanotechnology.

Science needed a very small carrier that would make a beeline for the tumor, and then have some mechanism that would thwart the low-oxygen zone. Science found what it needed in Nature.

They turned to a bacterium called magnetococcus marinus, or MC-1, that thrives in deep waters where oxygen is sparse. Then they rigged a chain of magnetic nanocrystals within MC-1. This acts like a compass needle and causes the bacteria to swim in a northerly direction when in the Northern Hemisphere. When the magnetic navigation has gotten the bacterial barge into the tumor, the doctors just turn it off. Finally, they added a second layer of navigation that could detect oxygen levels and drive the bacteria to the low-oxygen areas where the action is.

The pay-off? The researchers estimated that on average, 55 percent of the injected bacterial cells made it into the tumor.

“These bacteria are really the perfect machine. They replicate, they’re cheap, and we can inject hundreds of millions or more at a time,” says Martel.