Borrowing a technology used to produce microchips, researchers at the University of Illinois have created patterned glass surfaces on which live nerve cells can grow and wire themselves to electrodes. The tactic may help scientists to develop better implants, prosthetics and biosensors. "Controlling tissue response is particularly important for implants, which tend to work for a while, then lose electrical sensitivity," Bruce Wheeler explains. "If we can better understand and control the interface between electronic components and nerve cells, we could build more sophisticated and longer-lasting implants." Wheeler presented his team's newest findings at an international workshop last month in Germany.

The group harvested brain cells from developing rat embryos and separated them both chemically and mechanically. Using a lithographic method called microstamping, they then printed a pattern on the surface of a petri dish in polylysine, an artificial polymer used for cell cultures. "The microstamp works the same as a conventional rubber stamp except that the ink is polylysine and the patterns produced are measured in micrometers, or the same size as the cells themselves," Wheeler says. The scientists then poured the brain cells onto the patterned surface, where the cells attached to the artificial polymer. "Within a few days, the cells send out processes that explore the environment, preferring areas that have intact polylysine," Wheeler notes. "The cells soon mature and begin sending electrical signals."

The scientists faced two problems: the nerve cells tended to grow past the polylysine pattern and they didn't survive for very long. So to prevent the cells from outgrowing their minuscule barriers, the researchers covered the neural network with a layer of polyethylene glycol. "The nerve cells maintained compliance to the microstamped patterns and remained viable for up to one month," Wheeler says. He hopes that these neural networks will eventually let scientists study basic neuroscience more easily and even allow them to construct neural biosensors.