Monday, November 29, 2010


WorldWideTech & Science. Francisco De Jesús.

Doctors would really like to fight diseases such a cancer in precise, directed ways. That means delivering cancer-killing therapies to ugly cells, while leaving healthy cells alone. One way that could happen in the future is by using super tiny robots -- nanobots -- that work together inside the body like an infantry of warriors armed to battle cancer.
But there are some big challenges. Among them, communication. Like any battlefield army, soldiers need to coordinate their attacks. And nanobots, in theory, would have a difficult time. They can't use nano-sized cell phones, for example, because radio signals don't travel through liquids. (What about sonar? Has anyone looked into nano-sonar?) And chemical forms of communications only seem to work over long distances.
So, a team from the Polytechnic University of Catalonia in Barcelona, Spain, are looking at a way to use bacteria as messengers that deliver instructions to nanobots wrapped in DNA. Researchers Maria Gregori and Ignacio Llatser encoded the cytoplasm of non-pathogenic strain of E. coli with a short DNA sequence. Think of it as a tweet.
Here's how it might work: A scout-like nanobot in the body encounters a cancerous tumor. It wants to call over the troops for an attack, so it releases bacteria encoded with packets of information in the form of DNA. The bacteria swim towards soldier nanobots, where they attach to the nanobots and then download their DNA message. Orders in hand, the nanobots arm their attack.
It's way cool, but keep in mind this is all theory and simulation. In the simulation, bacteria equipped with flagella -- whip-like tails that propel them forward -- took about 6 minutes to travel 1 millimeter. And the amount of data they carried in DNA is equal to about 600 kilobits of information. That's 3G, which provides typical download speeds of 600 kilobits to 1.4 Megabits per seconds.

Injecting bacteria into the bloodstream might sound like a health risk, but those propelled by a whirling helical tail, or flagellum, could one day be used to send messages between cancer-fighting nanobots.
Maria Gregori and Ignacio Llatser at the Polytechnic University of Catalonia in Barcelona, Spain, envision a future in which nanobots in the body sense tumour cells and release anticancer drugs to fight them. But one machine can't defeat a tumour single-handedly; it needs some way of telling the others to swarm on the target.
Radio signals won't travel through a liquid, and chemical forms of communication using pheromones or calcium ions work only across large or microscopic distances. On the scale of a few millimetres – the distance from one blood vessel to another – there is no way to transmit information reliably.
So the pair came up with the idea of using bacteria with flagella, in this case a non-pathogenic strain of E. coli, to send the information. The idea is to encode a message in a DNA sequence that is inserted into each bacterium's cytoplasm. Each nanobot would contain bacteria inscribed with every message that could be needed
When a nanobot encounters a tumour, it would release the correctly encoded bacteria. These would then swim towards other nanobots, attracted by the nutrients stored there. Once there, the encoded DNA sequence binds with chemical receptors and its message – telling it where to swarm or to release its drugs – is acted upon.

Six minute transfer

In a computer simulation, the pair found bacteria that had flagella took about 6 minutes to traverse a distance of 1 millimetre from a transmitting to a receiving nanobot. They used an encoding scheme that enabled them to encode up to 300,000 DNA base pairs – or 600 kilobits of information.
"That's a bandwidth of 1.7 kilobits per second. It's not high, but for the biomedical applications we envisage it should be [fast] enough," Llatser says.
Others need convincing, however. "These are just simulation results. Everything is possible in simulation," says Andrew Adamatzky of the unconventional computing department at the University of the West of England in Bristol, UK.
Like the Barcelona team, Adamatzky also uses biology to model networks. He studies how slime moulds can be used in route planning and has famously remapped the UK's and Mexico's road networks with the organism Physarum polycephalum.
"While their simulation results seem OK, only experimental evidence will convince me that their technique is working," says Adamatzky.

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