U.S. nanotechnology engineers say they have created a nanoscale probe that can slide through a cell wall without damaging it and fuse with the membrane.

Stanford University researchers said their probe offers scientists a portal for extended eavesdropping on the inner electrical activity of individual cells. Everything from signals generated as cells communicate with each other to "digestive rumblings" as cells react to medication could be monitored for up to a week, the engineers said. Current methods of probing a cell are destructive and usually allow a few hours of observation before the cell dies.

The researchers said they are the first to implant an inorganic device into a cell wall without damaging it.

Assistant Professor Nick Melosh, who led the study, said with modification the probe might also serve as a conduit for inserting medication into a cell's heavily defended interior and also provides an improved method of attaching neural prosthetics, such as artificial arms that are controlled by pectoral muscles, or deep brain implants used for treating depression.

The 600-nanometer-long, metal-coated silicon probe has integrated so smoothly into membranes in the laboratory the researchers call it a "stealth" probe.

"The probes fuse into the membranes spontaneously and form good, strong junctions there," Melosh said. "We cannot pull them out. The membrane will just keep deforming rather than let go of the probes."

Melosh and graduate student Benjamin Almquist report their accomplishment in the Proceedings of the National Academy of Sciences.