Bacteria take fantastic voyage through bloodstream
Canadian engineers have sent swimming magnetic bacteria through the bloodstreams of rats. The work is a step towards the team's goal of harnessing them as drug mules steered through human bodies using magnetic fields.
Microscopic machines have proven attractive to medics trying to make treatments ever more targeted and less invasive than surgery. But although it is now possible to make micromachines from individual molecules, providing them with power is another matter.
Sylvain Martel's
team at the École Polytechnique de Montréal in Canada think tapping the
skills of bacteria that have evolved to swim with ease at the
microscopic scale is the best solution.
Speed demon
"Instead of trying to build a
nanomachine it makes more sense to spend effort trying to control what
nature provides," says Martel. He and his team are focusing on a
bacterium dubbed MC-1
– a microbial speed demon that swims 10 times faster than most species
and can travel at top speeds of 200 micrometres per second using its
twirling flagella.
If MC-1 was to be loaded with a drug
and given the ability to target a particular tissue it could provide a
nimble addition to the medical arsenal.
Apart from speed, the bacterium has
another property that makes it a perfect candidate for the role: each
cell contains a chain of magnetic nanoparticles, allowing the bacteria
to sense and swim along magnetic fields.
Remote control
By placing a patient inside an MRI
machine it would be possible to create a magnetic field to steer the
magnetic bacteria in any direction, towards targets just a few micrometres
across, says Martel.
Martel says initial tests suggest the
bacteria are not harmful – and generally not harmed – inside the body.
His team injected a 50 microlitre solution containing some 50 million
MC-1 bacteria into the bloodstream of rats, and found no adverse
reaction.
"More work needs to be done, but it
appears a sufficient quantity of these bacteria can be injected without
causing toxicity," he told New Scientist. The bacteria naturally die after about 40 minutes in the blood, and would then be cleaned up by the immune system.
The initial rat trials simply assessed
the health impact of injecting the bacteria – the next step is to guide
them using magnetic fields, which will be precisely controlled via
computer, says Martel. The team has already shown that's possible in
principle by steering the magnetic bacteria in a 50-micrometre-diameter
tube system.
Metal mules
In 2007, the same team piloted metal particles through the blood stream of a living pig
using an MRI machines. Using magnetic bacteria is a more attractive
option because the applied field needs only to direct the microbes as
they propel themselves towards the target.
Bradley Nelson at the Swiss Federal Institute of Technology in Zurich, who earlier this year designed a magnetically controlled artificial bacterium
, thinks the work is an improvement on a 2004 study by Howard Berg at Harvard University.]
, thinks the work is an improvement on a 2004 study by Howard Berg at Harvard University.]
Berg used another bacterial species to
create a simple propulsion system. "By using MC-1 instead, Martel had
been able to demonstrate steering in addition to propulsion," Nelson
says. "I am sure there are issues in keeping the bacteria happy, but it
is certainly a clever idea."
No comments:
Post a Comment