Under its human skin, James Cameron’s Terminator was a fully-armored cyborg built out of a strong, easy-to-spot hyperalloy combat chassis – but judging from recent developments, it looks like Philip K. Dick and his hard-to-recognize replicants actually got it right. In a collaboration between Harvard, MIT and Boston Children's Hospital, researchers have figured out how to grow three-dimensional samples of artificial tissue that are very intimately embedded within nanometer-scale electronics, to such an extent that it is hard to tell where one ends and the other begins. It could lead to a breakthrough approach to studying biological tissues on the nanoscale, and may one day be used as an efficient, real-time drug delivery system – and perhaps, why not, even to build next-generation androids.
Putting aside futuristic cyberpunk dreams, embedding electronics deep within biological tissue has concrete and immediate uses in the applied sciences of today, because it could lead to a finely tuned, two-way communication link between the biological and the synthetic. On the one hand, nanoscale sensors could be used to monitor cellular activity on a scale and precision never seen before; on the other, electrical signals could regulate the cells’ activity on a hyperlocal scale. One day, tying the two together could create a feedback loop capable of emulating much of the same functionality of our very own autonomic nervous system.
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So far, our attempts at creating an intimate blend of lab-grown tissues and nanoscale electronics have led to mediocre results at best. We can use probes to study the surface of the tissues, but this doesn’t give us a very clear picture of what is really going on. Even when we stick to scratching the surface, the information we can receive is limited because the probes we use to gather data almost invariably end up damaging the cells that we want to observe.
If we are to monitor and interact with biological tissues more effectively, we need a new approach that can gather data from deep within the tissues, and do so without damaging or even affecting them. One way would be to create three-dimensional structures in which nanoscale sensors reach all the way inside the tissue. The technique developed by the Boston-based researchers does exactly that.
The researchers have created a self-supporting scaffolding of nanowires, each about 80 nanometers in diameter, bunched up in a chaotic, porous configuration that has been likened to cotton candy and coated with a biocompatible material. Cell cultures are then deposited in the gaps between the nanowires and grow to form a single structure with the signal-carrying nanowires. With this technology, researchers can work at the cellular scale much more effectively, without damaging the cells and with the capability to observe cells from anywhere within the tissue.
In preliminary experiments, heart and nerve cells were grown inside the nanostructured scaffolding. Using the networks of nanowires, the researchers could detect the cells’ electrical signals generated deep within the tissues and measure how they responded to cardio- or neurostimulating drugs. Then, they constructed bioengineered blood vessels with embedded nanowiring networks and showed that they could measure changes in pH, which normally happen in response to inflammation.
The technique could be used to build implanted diagnostic and therapeutic devices, lab-on-a-chip tissues for drug screening, and even, most excitingly, cyborg-like tissues that can autonomously sense changes within our bodies and respond appropriately – perhaps by delivering the required stimuli (and even drugs) in real time, on a cell-by-cell basis.
A paper detailing this research was featured in a recent online issue of the journal Nature Materials.
Source: Boston Children's Hospital