Scientists looking for ways to get minute doses of drugs, so-called “nano-medicines”, into the right places in the human body have turned to “backpacking” bacteria to ferry the cargo.
This week, at the 243rd National Meeting & Exposition of the American Chemical Society (ACS) in San Diego, Dr David H Gracias, from Johns Hopkins University in Baltimore, Maryland, gave an account of the progress he and his team are making in this area.
Gracias told the press:
“Cargo-carrying bacteria may be an answer to a major roadblock in using nano-medicine to prevent, diagnose and treat disease.”
Nano-technology concerns itself with making ultra-tiny devices, small enough to fit a million or so on the head of a pin. In medicine the idea is to use them to transport particles of medication, sensors and other materials to precise locations in the human body.
But it is not easy to devise self-sustaining motors and propulsion mechanisms at this scale: so scientists are increasingly turning to nature, where organisms like bacteria are already of the right scale and capable of moving on their own.
As Gracias explained:
“Currently, it is hard to engineer microparticles or nanoparticles capable of self-propelled motion in well-defined trajectories under biologically relevant conditions.”
“Bacteria can do this easily, and we have established that bacteria can carry cargo,” he added.
The other advantage with using bacteria is they respond to specific biochemical signals. It is possible, for instance, to control their direction and destination in the body so that once they reach their target, they settle, deposit their “cargo” and grow naturally.
Bacteria are not strangers to the human body: were are covered with them on our skin, and our intestines are home to billions of them. In fact, the total population of bacterial cells we harbour outnumbers the population of our human cells by 10 to 1.
While the word bacteria may conjure up thoughts of disease and infection, many are safe and quite harmless, such as the colonies in our guts that are essential to food digestion.
It is these safe types of gut bacteria that Gracias and colleagues have turned to to find the ideal “beasts of burden” for transporting nano-materials that have optical, electrical, magnetic, electrical or medicinal properties.
So far, Gracias and his team have tested the backpacking bacteria with various shapes and sizes of “cargo” material. For example, they have used them to ferry nano-wires, beads and lithographically fabricated nanostructures.
Other teams are also working with bacteria to transport nano-cargoes. For example, one team has made “bacterial carpets” of large numbers of bacteria to move tiny bits of material.
But Gracias and his team are focusing on getting individual bacteria cells to transport individual bits of cargo, what they call “biohybrid devices”. The biohybrid devices can move freely with their cargo backpacks attached.
Gracias said their work is still at a very early, exploratory, stage. They are experimenting with lots of different things to see what might prove to be useful with using bacteria as backpackers for nano-medicines.
“Our next steps would be to test the feasibility of the backpacking bacteria for diagnosing and treating disease in laboratory experiments. If that proves possible, we would move on to tests in laboratory mice,” said Gracias, explaining that:
“This could take a few years to complete.”
Written by Catharine Paddock PhD