Scientists at Harvard University have developed a cyborg-like tissue that can facilitate cell growth, while simultaneously measuring the ongoing activity and status of those cells. They did so by embedding a three-dimensional network of functional, biocompatible, nanoscale wires into engineered human tissues. The breakthrough could have implications for the future of drug testing and regenerative medicine.
An ongoing problem in the field of tissue engineering has been in getting biomaterials to monitor or interact with changes around them. Normal human tissue can sense chemical and electrical changes, such as pH, chemistry, oxygen, and other factors, and then trigger an autonomic response. Materials scientists have struggled to find a way to mimic these feedback loops and maintain control at the cellular and tissue level.
But by creating nanoscale "scaffolds" that can be seeded with cells that grow into tissue, the Harvard scientists believe they've made a big leap in overcoming the problem. In essence, the team was able to merge tissue with electronics to create a hybridized, cyborg-like material.
The research team, which was led by Charles M. Lieber, the Mark Hyman Jr. Professor of Chemistry at Harvard, and Daniel Kohane, a Harvard Medical School professor in the Department of Anesthesia at Children's Hospital Boston, say that the technology will allow them to work at the same scale as the unit of a biological system.
By using the human autonomic nervous system as a model, the researchers built meshed networks of nanoscale silicon wires — a process similar to how microchips are etched. Starting with a two-dimensional sheet, the researchers laid out a mesh of organic polymer around tiny wires — wires that would later serve as the critical sensing elements. Then, nanoscale electrodes were built within the mesh, thus allowing the nanowire transistors to measure the activity of the cells. After this was done, the substrate melted away, leaving a netlike material that could be folded or rolled into any number of three-dimensional shapes.
As hoped, the material was spongy and porous enough to be seeded with heart and nerve cells — and to allow those cells to grow in 3-D cultures. This was the first time that the researchers were able to work outside of 2-D limitations.
Moreover, the researchers were also able to detect electrical signals generated by cells deep within the tissue, and to measure changes in those signals facilitated by cardio- or neuro-stimulating drugs. And remarkably, they were also able to construct bioengineered blood vessels which were in turn used to measure pH changes — the kind of responses that would typically be seen when tissue responds to inflammation or ischemia.
The researchers suspect that the pharmaceutical industry will benefit the most from this technology, allowing them to study how drugs work in 3-D tissues. But looking ahead to the future, it's clear that this breakthrough will hold profound implications for human functioning and the body's ability to detect and react to any number of changes in its environment.
The study can be read at Nature Materials.
Top image Sven Hoppe/Shutterstock.com. Inset image via Charles Lieber and Daniel Kohane/Technology Review.