Ever wonder how a germ knows where to attack the body or how a white blood cell knows where to counter attack? How bacteria find food? Or how cells organize themselves to close a wound? How can something so simple do things so complex? A team of MIT researchers is seeking the answers as they develop "microwalkers" – microscopic machines that can move unguided across the surface of a cell as they seek out particular areas.

Though they may not seem so at first glance, microorganisms are remarkable pieces of engineering. Lacking nervous systems, senses, or any way of understanding the world around them, they can look for and find places in the body or on cell surfaces where they can carry out their functions.

Alfredo Alexander-Katz, the Walter Henry Gale Associate Professor of Materials Science and Engineering and his team at MIT believe that if they can mimic this process, it will provide scientists with a valuable tool for constructing sensors and medical devices that can find their way to specific areas of a cell surface without outside guidance.

The MIT microwalker system is, like that of microorganisms, based on friction. On cell membranes, areas with a concentration of cell receptors tend to be rougher. White blood cells and other microorganisms use these friction gradients to find their destination in a sort of blind man's bluff called "chemotaxis" as they feel their way along. What the MIT team is trying to do is come up with a mechanical way of duplicating this.

The MIT system is based on a pair of linked particles. One particle has magnetic properties, while the other is designed to make contact with the surface. When a magnetic field is applied, the particle pairs are dragged along like magnetic beads in a children's toy – effectively causing them to walk across the surface until they reach their destination.

According to MIT, when the system is perfected, the microwalkers will be equipped with particles that will bind with receptors, giving them the same navigation by friction capabilities as microbes and allowing them to find particular areas without being told where they are.

MIT sees a number of applications for the microwalkers. They could be made to congregate around cells or areas of cells that are of interest to scientists, or could be used to locate and identify pathogens and tumors that would otherwise escape detection. It could also be a means of delivering targeted drugs or microsensors.

Alexander-Katz says that so far the method has been confined to microscope slides, but the team is working on how to make it work on living tissue. Now that the method has been proven to work on flat surfaces, the next step will be to see if it can be adapted to complex three-dimensional structures, such as cells.

The team’s findings were published in the journal Physical Review Letters.

Source: MIT

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