Operating tiny motors inside a cell is a “basic science” breakthrough toward a far-off dream.
Scientists at Pennsylvania State University and colleagues have built tiny motors, or nanomotors, that operate inside living human cells.
To understand the technology, you have to completely throw out the notion that a motor is a loud, hulking thing. Instead, think of the stripped down, basic definition. A ‘motor’ is any machine that produces motion in something else.
Each nanomotor is a gold rod with an arrow-shaped tip and a concave tailpipe. They get their get-up-and-go from ultrasound pulses. Flip a switch and sound waves travel through fluid then bounce off the metal rods sending them careening.
“You can make these things go really fast, you can make them spin around,” said biochemistry professor Tom Mallouk, leader of the nanomotors team. “They are like a bunch of bumper cars running around aimlessly.”
The scientists can view all that motion through the barrel of a microscope—and can control the action using magnets and varying sound wave intensities. The rods can be propelled forward like a rocket or made to spin like a single eggbeater blade.
Penn State’s motors are elegantly simple and very, very small.
“They are a couple of micrometers long,” Mallouk said. “A good way to think of this is that a human hair is about 50 micrometers wide. So, you line up 25 of these [nanomotors] end-to-end–and they span a hair.”
Two years ago, two research groups—one at Penn State, the another at the University of California, San Diego–announced they’d learned to use ultrasound to power nanomotors.
New this week: Mallouk and his team say they’ve learned how to slip their motors inside human cells living on the surface of a microscope slide.
The new nanomotors ricochet inside the cells crashing into organelles, sub-cellular structures.
“One of the things we observe—and we don’t understand yet–is if we tickle the cell in one place, it giggles somewhere else,” Mallouk said.
Scientists know a great deal about cell biology–and lots about the chemistry that happens inside human cells. Mallouk says less is known about the mechanics of the structures inside cells—how they are connected together and communicate.
The new nanomotors could be a new tool to let researchers poke and prod around inside a cell and see what happens—kind of like the little hammer a doctor uses to knock your knee and test your reflexes.
Looking for bio-compatibles
Nanomotors are not new. Scientists have been tinkering with and improving them for more than a decade. Early-generation nanomotors didn’t work properly inside biological matter—and were gassed up using fuels that would be toxic to humans.
Ever since, researchers have been on the hunt for a fuel-free propulsion mechanism for their motors with the potential to work inside living tissue.
Joseph Wang, nano-engineering professor at the University of California, San Diego says Mallouk’s team has done that. Wang also studies and develops nanomotors but was not involved in the latest research from Penn State.
“Tom Mallouk’s group demonstrated that these ultrasound motors—based on gold nano-wires—can not only approach a cell, but also the cell can swallow the motors,” Wang said. “It’s major progress.”
The motors were tested inside HeLa cells, which are popular in scientific research.
“These cells are rough, tough. They are an immortal cell line,” Mallouk said. “They are perfectly happy and we see no change in their viability after poking them with motors for hours.”
Imagining the possibilities
Penn State’s breakthrough is a basic-science advancement on a long road toward–someday–deploying microscopic robots inside the body to hunt down disease and treat illness.
Lots of people working in the field of nanoparticles have been inspired by the 1960s Sci-fi film “Fantastic Voyage.” In the movie, a medical crew—and its submarine–are shrunk down to the size of a red blood cell—then launched inside a patient. Mallouk says even with all its campy special effects, the movie is a pretty good way to imagine what nanonmotors might accomplish someday.
As an example, one of Mallouk’s good friends is a brain surgeon. He spends hours under bright lights—using fine tools to excavate tumor tissue—all the while–trying to avoid delicate, healthy tissue.
“I would like to make his life easier,” Mallouk said. “So instead of having the patient with his cranium sawed open … we’d just inject 100 million of our nanomotors into the patient’s arm.”
Mallouk imagines that instead of standing in a surgery suite—a doctor would sit at video game console and send out future-generation nanobots to deliver medicine–or may puncture cancer cells.
Later, the tiny bots would get flushed out of the body through the kidneys.
That’s the dream—anyway. Mallouk said his real-life work is a small piece of that dream.
While Penn State refines its nanomotors powered by ultrasound, collectively, the community that works on nanoparticles is designing other aspects of the nanomotor—including propulsion and communications–and making sure all this new technology is truly compatible with the body–and safe.
“You don’t want anyone promising quick cures for cancer, it’s fundamental research,” Mallouk said.
The importance of fundamental research is easy to quantify after the fact,” he said, “much harder to value upfront.”