Researchers in the field of molecular machines were awarded the Nobel prize for chemistry in 2016, although the committee noted that the science was still in its infancy. Current nanomachines were compared to the electric motors of the 1830s, in which early scientists displayed spinning wheels and cranks, unaware of the future impact they would have.
In one of the first applications of modern nanomachines, the team at Rice University led by James Tour have used UV light to drive molecular rotors that spin at 2 to 3 million rotations per second. These tiny drills, each only a nanometre in size, were shown to rupture the membranes of living cells, causing molecules that are normally kept out by the protective membrane to diffuse into the cells.
The machines could also be used to kill the cells, which may offer a new strategy to eliminate cancer. When specific peptides were attached to the nanomachines, the devices could be targeted to the membranes of prostate cancer cells, with other control cells left intact.
This membrane disruption approach is a completely different mode of action compared to traditional chemotherapies, which often block cell division and which cancers can become resistant to. “It is highly unlikely that a cell could develop a resistance to molecular mechanical action,” Tour said.
In the clinic it is probably not practical to use UV light to drive these motors, as UV light does not penetrate well into living tissue. The team are looking to trial near infrared light or even radio frequencies to power future machines, as these would allow the therapy to be targeted to specific sites within the body, possibly reducing side effects.
“These nanomachines are so small that we could park 50,000 of them across the diameter of a human hair, yet they have the targeting and actuating components combined in that diminutive package to make molecular machines a reality for treating disease,” Tour said.