These tiny robots could be disease-fighting machines inside the body
These tiny robots could be disease-fighting machines
inside the body
Nanobots could provide cancer treatment free from side
effects.
by Edd Gent / Mar.30.2018 / 8:25 AM ET
Call it another case of science fiction becoming
scientific fact. Researchers have long dreamed of developing tiny robots that
could roam about inside our bodies, delivering drugs with unprecedented
precision, and hunting down and destroying cancer cells.
We’re not there yet, but we’re getting close. Last month
scientists from China’s National Center for Nanoscience and Technology (NCNT)
and Arizona State University said they had developed robots a few hundred
nanometers across — there are 25 million nanometers in an inch — and when they
injected them into the bloodstream of mice, the nanorobots could shrink tumors
by blocking their blood supply.
The nanorobots were made from sheets of DNA rolled into
tubes containing a blood-clotting drug. On the outside, the researchers placed
a small DNA molecule that binds with a protein found only in tumors. When the
bots reached tumors, this molecule attached to the protein, triggering the DNA
tube to unroll and release the drug.
Most cancer drugs typically have nasty side effects
because they can’t distinguish between cancer cells and healthy ones. The
researchers showed that the nanorobots only targeted the tumors and didn’t
cause clotting elsewhere in the body. They say this offers a promising future
of cancer treatments free of side effects.
Such a device is very different from the human-scale bots
that build our cars and vacuum our floors. But Guangjun Nie, one of the NCNT
professors who developed the nanorobots, points out that they are able to sense
their environment, navigate, and carry out mechanical tasks just like large
robots.
The researchers are working with a biotech firm to
commercialize the cancer-fighting nanobots. And Nie says this is just a taste
of what DNA nanorobots could do.
“What we call nanorobots are the next generation of
nanomedicines because they give you much better control and can be made to work
like a machine,” he says. "In the future we will demonstrate even more
scenarios for our nanorobots from monitoring disease, to finding tissue damage,
curing cancer and maybe even finding and destroying plaques in our blood
vessels."
The idea of tiny disease-fighting machines working inside
the human body can be traced at least as far back as the 1966 release of the
movie “Fantastic Voyage,” in which a submarine and its crew were shrunk down
and injected into a scientist’s body to remove a dangerous blood clot.
In real life, of course, it’s not so easy to shrink
machines, much less humans. Computer chips, electric motors, and batteries are
typically too bulky to operate in blood vessels or between cells.
But being able access hard-to-reach areas of our bodies
could have profound implications for medicine, so scientists are scrambling to
find ways to power and control inside-the-body bots.
In addition to boosting the effectiveness and lessening
the side effects of powerful drugs, nanorobots loitering in our bloodstream
could act as early warning systems for disease. And tiny wireless surgical
tools could let doctors perform medical procedures without cutting people open.
Eric Diller, an assistant professor of mechanical
engineering at the University of Toronto in Canada, is working on this last
problem. He’s developing robots just under a millimeter across that are built
from elastic polymers filled with magnetic particles that can be dragged
through fluids and triggered to grasp objects.
These tiny bots are controlled by precise magnetic fields
generated by an array of electromagnets. The robots could eventually be used to
collect tissue biopsies or carry drug capsules inside the body, says Diller.
His lab has yet to test the devices in animals, but
researchers at ETH Zurich, in Switzerland, have already tested a similar
magnetically guided microbot in the eye of a rabbit, using it to puncture a
blood vessel with its needle-like tip. The ultimate goal, Diller says, is to
create a suite of wirelessly powered surgical tools.
"Instead of having an open wound site we would like
to be able to inject surgical tools,” he says. "We could do non-invasive,
not just minimally invasive, procedures with no external cuts and without the
complications that come from surgery."
Probably the most developed and versatile approach to
microscopic medical robots uses so-called “nanomotors” and “micromotors.” These
are tiny particles, tubes, or wires made from materials like gold, magnesium,
and carbon. They either propel themselves using fuels found in the body — such
as stomach acid or water — or are dragged or pushed around by magnetic fields
or ultrasound waves.
Researchers have shown that these devices can precisely
navigate to disease sites and can even penetrate deep into diseased tissue to
deliver drugs more efficiently. When combined with biosensors like enzymes or
antibodies, they can create much more sensitive ways to detect chemical signals
of disease, because their movement means they bump into other molecules more
frequently.
By the same principle, combining them with nanosponges
that absorb toxins could someday create tiny robots that efficiently mop up
harmful substances in the body.
Dr. Joseph Wang, a professor of nanoengineering at the
University of California, San Diego, is one of the pioneers of this field. Last
August, his lab demonstrated that micromotors loaded with antibiotics and
powered by stomach acid could treat stomach infections in mice more effectively
than taking the drug by itself.
"We just dump the motors in the stomach and they
just swim autonomously," he said. "It's like taking a pill and
forgetting about it."
Meanwhile, other researchers are looking for ways to
harness and redirect the activities of nature’s own tiny machines.
In December, a group at the Leibniz Institute for Solid
State and Materials Research in Germany loaded sperm cells with anti-cancer
drugs and fitted them with tiny magnetic harnesses. The sperm tails provided
propulsion but the harnesses let the researchers guide them using a magnetic
field toward mini cervical cancer tumors that had been grown in a petri dish.
They killed 87 percent of the tumors’ cells within three days.
And in 2016, a team from Polytechnique Montréal in Canada
hijacked bacteria that naturally swim along magnetic field lines, loading them
with cancer drugs and using artificial magnetic fields to steer them to tumors
in mice.
Eventually, Diller says building in-the-body robots from
scratch will give us much greater control over their functionality. But we’re
still a long way from being able to mimic nature’s innovations, so for now,
these bio-hybrid approaches are a smart idea.
“At this point in time there is a compelling argument for
using these organisms that are already functional and trying to modify them to
do what our goal is,” he says. “They have much more functionality than the
devices we can build today.”
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