"The scaffold is not just a mechanical support for cells, it contains multiple sensors. We seed cells into the scaffold and eventually it becomes a 3-D engineered tissue," Tian says.
The team chose silicon nanowires as its electronic sensors because they are small, stable, can be safely implanted into living tissue, and are more electrically sensitive than metal electrodes. The nanowires, which range in diameter from 30 to 80 nanometers (about 1,000 times smaller than that of a human hair), can detect voltages less than one-thousandth of a watt, which is the level of electricity that might be seen in a cell.
Monitoring cell behavior
In the Nature Materials study, the researchers used their scaffolds to grow cardiac, neural and muscle tissue. Using the engineered cardiac tissue, the researchers were able to monitor cells' response to noradrenalin, a stimulant that typically increases heart rate.
The team also grew blood vessels with embedded electronic sensors and showed they could be used to measure pH changes within and outside the vessels. Such implantable devices could allow doctors to monitor inflammation or other biochemical events in patients who receive the implants. Ultimately, the researchers would like to engineer tissues that can not only sense an electrical or chemical event, but also respond to it appropriately for example, by releasing a drug.
"It could be a closed feedback loop, much as our autonomic nervous system is," Kohane says. "The nervous system senses changes in some part of the body and sends a message to the central nervous system, which then sends a message back to take corrective action."
The team is now further studying the mechanical properties of the scaffolds and making plans to test them in animals.
|Contact: Sarah McDonnell|
Massachusetts Institute of Technology