SAN DIEGO - Taking a new approach
to the painstaking assembly of nanometer-sized machines,
a team of scientists at the University of Wisconsin-Madison
has successfully used single bacterial cells to make
tiny bio-electronic circuits.
The work is important because
it has the potential to make building the atomic-scale
machines of the nanotechnologist far easier. It also
may be the basis for a new class of biological sensors
capable of near-instantaneous detection of dangerous
biological agents such as anthrax.
approach, was reported March 17, 2005 at a meeting
of the American Chemical Society, suggests that microbes
can serve as forms for complicated nanoscale structures,
perhaps obviating, in part, the need for the tedious
and time-consuming construction of devices at the
The work is also scheduled
to appear in the April issue of the journal Nano Letters.
"One of the great challenges
of nanotechnology remains the assembly of nanoscale
objects into more complex systems," says Robert
Hamers, a UW-Madison professor of chemistry and the
senior author of the new reports. "We think that
bacteria and other small biological systems can be
used as templates for fabricating even more complex
Toward that end, Hamers and
his UW-Madison colleagues Joseph Beck, Lu Shang and
Matthew Marcus, have developed a system in which living
microbes, notably bacteria, are guided, one at a time,
down a channel to a pair of electrodes barely a germ's
length apart. Slipping between the electrodes, the
microbes, in effect, become electrical "junctions,"
giving researchers the ability to capture, interrogate
and release bacterial cells one by one. Built into
a sensor, such a capability would enable real-time
detection of dangerous biological agents, including
anthrax and other microbial pathogens.
"The results here are
significant because while there has been much attention
paid to the ability to manipulate nanoscale objects
such as nanotubes and nanowires across electrical
contacts, for many applications the use of bacterial
cells affords a number of potential advantages,"
For example, capitalizing on
the complex topography of the bacterial cell surface
and microbial interactions with antibodies, scientists
could potentially construct much more complex nanoscale
structures through the natural ability of cells to
dock with different kinds of molecules. Such a potential,
Hamers argues, would be superior to the painstaking
manipulation of individual nanosized components, such
as the microscopic wires and tubes that comprise the
raw materials of nanotechnology.
"We spend a lot of time
making tiny little nanowires and things of that sort,
and then we try to direct them in place, but it is
very hard," says Hamers. "However, bacteria
and other biological systems can be thought of as
nature's nanowires that can be easily grown and manipulated."
In the series of experiments
underpinning the new Wisconsin work, the group showed
that it is possible to capture cells along an electrode
and then direct them down a narrow channel that acts
as a conveyor. Small gaps in the electrical contacts
along the conveyor serve as traps that can hold single
bacterial cells while their electrical properties
are measured. Once the microbial interrogation is
completed, the live cell can be released.
"You can measure and release
them at your leisure," explains Beck, the lead
author of the Nano Letters paper and a UW-Madison
He says the chemicals naturally
expressed on the surface of the bacterium could be
wired in a way that would be the basis for a real-time
biological sensor, a device that could be seeded in
airports, stadiums, railway stations, skyscrapers,
mailrooms and other public areas to sniff for dangerous
biological agents that might be used in a bioterror
The device could be constructed,
according to Beck, utilizing the natural features
bacteria and other microbes use to sense their environments.
The wired bacterial cells, coupled with modern microelectronics,
would have the ability not only to detect dangerous
agents (anthrax spores, for example) but they then
could sound the alarm and call for help.
"You could even engineer
bacteria to have different surface molecules that
you could capitalize on," says Beck.
For instance, it may be possible,
the Wisconsin scientists say, to attach microscopic
gold particles to the shell of the bacterium, making
it more like a nanoscale gold wire.
Hamers believes the new work
could be the basis for bringing nanotechnology and
biology together in unprecedented ways.
Moreover, the ability to routinely
and easily capture and analyze individual microbes
will have implications for conventional biotechnology
as well. For example, chemical modifications to the
electrode traps might make it easier for scientists
to retrieve specified cells from a complex mixture.
The work by Hamers' group was
funded by the National Science Foundation. The Wisconsin
Alumni Research Foundation, a private, nonprofit organization
that manages UW-Madison intellectual property, has
applied for patents for the technology.
Devitt, 608-262-8282, firstname.lastname@example.org
CONTACT: Robert J. Hamers,
608-262-6371, email@example.com; Joseph D. Beck,