New Scientist 1 February 2001 Silicon and cells Electrical signals from human cells are coupled to silicon chips Living tissue has been hooked up to electronic circuitry by scientists in Germany. The technique could lead to implants that communicate with the body and hybrid sensors made from biological material and silicon. "Having solved the principal problem of coupling cellular electrical signals with silicon electrical signals, we can now proceed to develop cellular biosensors," says Peter Fromherz at the Max-Planck Institute for Biochemistry, Martinsried, Germany. Connecting living cells to silicon circuitry is difficult because cells grown on silicon sheets do not bond to the surface. Instead they float in their nutrient solution about 40 nanometres above it. Even though the gap is small, it makes it very difficult for electronic devices to detect the weak electrical signals produced by the cells. Fromherz found a way around the problem by making cells produce larger electrical signals through their "ion channels". These are gates in the cell membrane that pump out electrical signals. Signal booster To boost the signal, he took human kidney cells that have very few "ion channels" - effectively a blank canvas - and added a gene for a specific type of ion channel capable of conducting large electrical signals. The result was a group of cells with extra ion channels capable of producing stronger electrical signals. When Fromherz grew the cells on a silicon transistor he found the transistor could detect and amplify the electrical signals being pushed out of the cells. Erwin Neher of the Max-Planck Institute for Biophysical Chemistry in G³)ngen says that coupling living tissue to electronics in this way could lead to far more sophisticated implants than we have right now: "Intelligent prosthetic devices could be designed that allow two-way communication between their control circuits and the nervous system."
