Embedded nanowires could control tissue growth

日期:2019-03-01 07:18:07 作者:段干拗 阅读:

By Michael Reilly A new way of embedding silicon nanowires in cells could one day allow scientists to control how living tissues grow using electrical stimulation. Living cells cannot easily be connected to nanowires. In the past, researchers have had to physically push nanowires or carbon nanotubes into the cells, which can damage or kill them. However, Peidong Yang of the University of California at Berkeley and a team of researchers found that when cells in a solution settle onto an array of silicon nanowires, they gradually incorporate the wires into the cells without any resistance. Importantly, the team didn’t use just any old cells – they used embryonic stem cells from a mouse that had begun differentiating into cardiac muscle. Stem cells are especially intolerant of being disturbed, but the researchers managed to grow the mouse cells for over a month with the wires inside. They even watched as the mass of cells beat like a heart. “Stem cells are very sensitive to external stimulation,” says Dong Cai of Boston College, who was not involved in the study. “By not using force, the researchers’ method is more compatible with biological systems, so the cells stay happy.” The key to the process working, Yang suspects, is that the silicon wires form a coating of silicon dioxide when exposed to air. “The oxide is very compatible with the cell membranes, which wraps around the wires”, then assimilates the wire into the cell, he says. Still, similar tests using human kidney cells showed that they only survived for long periods – up to a week – when wires were between 30 and 90 nanometers in diameter. The cells died off within a day when diameter was increased to 400 nm. With the wires safely embedded, the next step will be to zap the cells with a current to see how they respond. Yang believes that by varying power levels he can make the cells differentiate into various tissues such as neurons, muscles, or glands like the pancreas. “It is our hope that this will be our way of communicating with the cells,” he says. “We’d like to explore this new version of the nano-electrode and see if we can guide how stem cells differentiate.” If the technique works, it would represent a new way of manipulating stem cells to form tissues. Current methods rely chiefly on providing cells with chemical cues on how they should differentiate. The team also demonstrated that wires coated with DNA could transfer the genetic material to the cell. This feat has been accomplished before using carbon nanotubes, but Yang says the nanowires’ tiny size could increase the procedure’s accuracy by inserting genes into specific organelles within the cell. “We should be able to pinpoint delivery to within a spatial resolution of 50 nm,