Image: Microcapsules illustration
University of Pittsburgh
Microcapsules in "snake" formation as competing signaling capsules (shown in red) pull respective lines of target cells in opposite directions.
updated 7/23/2010 4:01:55 PM ET 2010-07-23T20:01:55

Inspired by the social interactions of ants and slime molds, scientists from the University of Pittsburgh have created slimmed-down, virtual slime mold cells to study how organisms communicate and work together.

The research could lead to a new generation of microscopic devices that could deliver medicines inside the body.

"Cells have all this complicated machinery to perform various functions," said Anna Balazs, a co-author of a recent study on the work in Proceedings of the National Academy of Sciences and a scientist at the University of Pittsburgh. "We wanted to see what you could do if you didn't have all that complicated machinery."

That complicated machinery lets cells do all the things they need to survive: it helps them find or make food, excrete, move and sense their surrounding environment. Another vital function of that machinery is to communicate between cells or organisms, allowing groups to accomplish tasks that are impossible for a single cell.

For tiny-brained ants, this might be moving massive amounts of food along a trail back to their home. For slime molds that don't even have a brain, communication allows them to build fruiting bodies that shoot out the next generation of slime mold. Other organisms, including deadly, infectious disease, coordinate their behavior using these chemical signals.

The University of Pittsburgh scientists sought to mimic this behavior in a computer using a new computer model. They created virtual, but very slimmed-down versions of slime molds using microscapsules as small at 10 microns across that secreted nanometer-scale particles.

The virtual nanoparticles performed two functions. First, they controlled the viscosity of a little oval racetrack, making it smoother or stickier. As the cells pushed out the nanoparticles, they push themselves forward. By varying how many of the nanoparticles are pushed out the scientists could vary the speed of the nanoparticles.

Second, the secreted nanoparticles controlled how the virtual cells worked with each other. Depending on the molecules, the virtual cells worked together to create three types of groups: an ant trail, a dragon or a snake.

An ant trail is so named because it resembles the pheromone trail ants leave behind so others can follow them. The virtual cells do the same thing. One cell moves around the track and leaves a trail of molecules in its wake. Those molecules activate target cells, which then follow the first cell around the track.

A dragon forms when two cells work together, leading a long chain of other cells around the track. When two cells compete against each other, they form a snake, or two lines of cells moving around the track.

In the computer, ants, snakes and dragons just race around the track. In a person, these animal-themed cells could act like semi-trucks, hauling drugs to various cells inside the body. In nascent lab-on-a-chips, otherwise known as microelectromechcanicsal systems, these cells could act as gate keepers, separating and sorting various tiny molecules

The next step in the research is for someone to actually build this system, a consideration the Pitt researchers had from the beginning. "We made sure that all the pieces we put together were based on real systems, so people could make the microcapsules we simulated," said Balazs. "The next step is having an experimentalist actually build what we described."

That shouldn't be too hard, according to Steven Levitan, another co-author of the PNAS paper and a scientist at the University of Pittsburgh; microcapsules and nanoparticles like the ones they simulated already exist.

Whether the virtual particles are ever made real, "the results are quite thought provoking," said Manoj Chaudhury, a scientist at LeHigh University who reviewed the work. Chaudhury expects the new research will inspire scientists in a variety of fields, including microelectromechanical devices, drug delivery and microfluidics.

© 2012 Discovery Channel


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