Researchers are genetically modifying
ordinary mice, like the one shown here, to make
them far more sensitive to explosives.
Scientists are engineering a real-life Mighty Mouse
that will scurry through fields sniffing out hidden
landmines thanks to olfactory superpowers.
The researchers, at Hunter College of the City
University of New York, have genetically
engineered the animals to be 500 times better
equipped than their normal counterparts to sniff
out landmine explosives. They hope that these
"hero mice" could warn of buried bombs.
Hidden landmines are a deadly reality in nearly 70
countries globally, and detection and removal are
expensive and dangerous. Currently, metal
detectors, radar, magnetometers, and sniffer
dogs are used to search for them.
A Belgian organization called APOPO already uses
giant African pouched rats as a cheaper way to
sniff out landmines. The rats are not genetically
modified, but their sense of smell is sharp
enough to detect TNT. The bomb-sniffing rats are
taught to scratch the ground when they detect a
hidden mine (fortunately, they are small enough
not to set off the explosives). While the furry
minesweepers are effective (with two handlers,
they can cover a field in one hour that would take
two full days for metal detectors), they need nine
months of training to become reliable, a process
that costs around 6,000 euros per rat.
The genetically engineered mice, however, are so
sensitive to TNT that encountering the molecule is
likely to change their behavior involuntarily, so
they would need little to no training. Charlotte
D'Hulst, a molecular neurobiologist at Hunter
College who presented her work at a meeting of
the Society for Neuroscience, used genetic
modification to ensure that the mice have 10,000
to 1,000,000 odor-sensing neurons with a TNT-
detecting receptor compared with only 4,000 in a
normal animal, "possibly amplifying the detection
limit for this odor 500-fold," she says. Each odor-
sensing neuron in a mouse's nose is spotted with
one kind of odor receptor. Usually, each specific
receptor is found in one out of every thousand
odor-sensing neurons, but about half the scent-
detecting neurons in D'Hulst's mice have the TNT-
detecting receptor.
This particular odorant receptor was originally
identified by Danny Dhanasekaran, a molecular
biologist at the University of Oklahoma College of
Medicine. Dhanasekaran says that a given odor is
usually detected by a handful of different kinds of
odorant receptors, which helps natural noses
more easily and accurately discern smells.
However, by engineering a great abundance of
one receptor that detects TNT, D'Hulst and
colleagues "could enhance the sensitivity of the
system so it can be easily used in operations to
detect landmines," says Dhanasekaran, who is
continuing to look for other TNT-type receptors.
D'Hulst hopes this overwhelming dedication to
just one odor will provide an easy way to know
whether or not the engineered mice have
encountered TNT. Recent research suggests that
sudden and intense stimulation of the olfactory
system will trigger seizures, she says. "We can
only hope that our mice will show a seizure
behavior ... upon detecting landmines. We won't
have to work with food rewards; we will
probably use some radio signaling system. A
chip implant may track, report, and record their
behaviors." The researchers still need to test the
mice in behavioral studies.
Roger Hess, director of field operations for Golden
West Humanitarian Foundation, a charity that
develops technologies to aid landmine removal,
says that while this mine-sniffing method could
show promise, it would still depend on detection
of trace vapors from the mine. The release of the
odor from the ground can depend on soil and
water conditions, and the trace of an explosive
could be several meters away from where the
mine is actually buried, he says. The technique
will also not work for mines that have no gaps
for the scent of explosives to escape.
"Due to the risk of missing an item, a secondary
method would need to be employed," he says.