21 July 2010

Beware the Zombie Nano-Assassin


Perhaps the most important difference between life and non-life is the ability of biological cells and organisms to communicate -- and modify their behaviour on the basis of that communication. Cell signaling and organism to organism communication allow for remarkable adaptation to changing circumstances within and around cells and organisms.

University of Pittsburgh researchers are designing artificial life cellular systems that are able to signal, and achieve self-organising behaviours of a complexity not generally attributed to non-biological entities. This project uses a vastly simplified form of "cell signaling" compared to actual biological cells, but it represents the "baby steps" of a human effort to devise useful artificial nano- and micro- systems which display something of the adaptability and "ingenuity" of living systems.
To communicate, a signaling cell will secrete special nanoparticles known as agonists that prompt the target cell to respond by secreting different nanoparticles known as antagonists. When the antagonists reach the original signaling cell, it stops secreting agonists. Once the signaling cell goes silent, the target cell does the same (it was only secreting antagonists in response to the agonists). At that point, the signaling cell knows to start signaling again.

This cycle locks the two into a cycle that can be thought of as a conversation. Engineers can manipulate that conversation by adjusting the nanoparticles themselves, the capsules' permeability, and the number of nanoparticles each one is given.

But how do the microcapsules know where to find each other? That's the neatest trick of all: the Pitt engineers devised a method -- with a tip of the hat to ants -- wherein the capsules leave a chemical trail behind them as they move about. That trail prompts other microcapsules to follow, just as ants follow one another along a perfect trail even though the trail isn't marked. Such an ability to gather, follow, and cooperate could make for highly targeted drug delivery systems or carry out super-precise chemical processes in the lab. _PopSci
Ants, slime moulds, bacterial signaling etc . . . there are many biological parallels to what the U. Pittsburgh researchers are attempting. The difference is that the biological examples are orders of magnitude more complex than the artificial system -- which is only a computer simulation so far.

Such research may lead to utility fog (flocking nano-actuators) or smart dust (flocking nano-computing). Biomedical research will almost certainly use such technology -- once instantiated in real form -- for diagnostic and therapeutic purposes. Military and intelligence agencies will use it for stealth information gathering -- and perhaps for untraceable assassinations.

Once nano-technological tools are given biological-level signaling tools, the variety of tasks for which such hybrid designs could be suited is difficult to overstate. And you will never see it coming, since such very small objects can float on the wind, burrow through "solid objects", or swim through water like a tiny minnow.

These tools can provide narcissistic would-be tyrants with powers far more powerful and selective than any nuclear arsenal.

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