Cells grow on a bed of nails

Putting cells on pins and needles is a way of getting foreign molecules into the cells, according to a team led by chemist Peidong Yang at the University of California, Berkeley, and medical researcher Bruce R. Conklin at the Gladstone Institute of Cardiovascular Disease in San Francisco (J. Am. Chem. Soc. 2007, 129, 7228). They have been growing mammalian cells on arrays of silicon nanowires, each about 3-6 µm long and less than 100 nm in diameter (shown). As the cells settle out of the culture medium onto the bed of nanowires, the wires penetrate the cells without damaging them and without the application of any external force. The cells survive and proliferate, even after being impaled on the wires. By first depositing DNA onto the wires, the researchers are able to transfer the genetic material into human embryonic kidney cells. The team expects that the delivery efficiency could be improved by adjusting the nanowires' surface chemistry. The nanowire arrays could also be used for drug delivery and electrical stimulation and detection in cells, the scientists say.