Testing living cells’ influence on nanostructure growth — continued
Helen Baca looks over the letters
“CDA,” standing for cell-directed
assembly, prepared by UNM grad
student Eric Carnes, who for the
picture stained an estimated 10
billion yeast cells with nucleic acid.
(Photo by Randy Montoya)
“We know they can withstand quite a bit
of radiation,” says Baca. The samples have
survived exposure to powerful X-rays and
the vacuum of an electron microscope,
The entrapped cells easily absorb other
nanocomponents inserted at the cellular
interface. Because of this, a cell can internalize
new DNA, providing an efficient form
of genetic modification of cells without the
usual procedures of heat shock or cumbersome
puncturing procedures that can result
in cell death. For example, the yeast can be
modified to glow fluorescent green when
they contact a harmful chemical or biotoxin.
Because such nanostructures are cheap,
extremely light and small, and easy to make,
they could conceivably be attached to insects
and their emanations read remotely by
beams from unmanned aircraft.
The method also makes it easier to
prepare individual cells for laboratory investigation
under microscopes. “Normally,
to visually examine a cell, researchers use
time-consuming fixation or solvent extraction
techniques,” says Brinker. “We can
spin-coat a cell in seconds, pop the cell into
an electron microscope, and it doesn't shrink
when air is evacuated from the microscope
chamber.” (Spin-coating refers to deposition
of the cell slurry on a spinning substrate
until dry.)
Understanding TB
Assistant Professor Graham Timmins
of UNM’s College of Pharmacy notes that
the encapsulated cells' unusual longevity
may serve as a model for persistent infections
such as tuberculosis, which has a long
latency period. TB bacteria can remain
dormant for 30 to 50 years and then reactivate
to cause disease. Presently, the state of
the dormant bacterium is not understood.
Timmins and Brinker are discussing further
experiments to validate the model.
Finally, building the cells into a coating
with a high enough density might elicit from
them a defensive, multi cellular signal of an
unpleasant nature that discourages unwanted
biofilm formation on the coated surface —
important for avoiding infections that could
be carried by implants and catheters.
The cell’s ability to sense and respond to
its environment is what forms these unique
nanostructures, says Brinker. During spincoating,
the cells react to the increasing
concentrations of materials in the developing
silica nanostructure by expelling water and
developing varying levels of acidity. This in
turn influences the form of the silica nanostructure,
reduces stress, and ultimately
improves the living conditions of the ensconced
cellular tenants.
Technical Contact: Jeff Brinker (505) 272-7627, cjkbrink@sandia.gov
Media Contact: Neal Singer (505) 845-7078, nsinger@sandia.gov
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