After gold nanoparticles are trapped on the brown collection surface (left), the NIST team can apply a mild electric field and release most of them (right). The ability to trap and release particles in this fashion could aid in studying their properties, particularly with respect to their effects on human health. |
Depending
on whom you ask, nanoparticles are, potentially, either one of the most
promising or the most perilous creations of science. These tiny objects
can deliver drugs efficiently and enhance the properties of many
materials, but what if they also are hazardous to your health in some
way? Now, scientists at the National Institute of Standards and
Technology (NIST) have found a way to manipulate nanoparticles so that
questions like this can be answered.
The
team has developed a method of attracting and capturing metal-based
nanoparticles on a surface and releasing them at the desired moment. The
method, which uses a mild electric current to influence the particles’
behavior, could allow scientists to expose cell cultures to
nanoparticles so that any lurking hazards they might cause to living
cells can be assessed effectively.
The
method also has the advantage of collecting the particles in a layer
only one particle thick, which allows them to be evenly dispersed into a
fluid sample, thereby reducing clumping—a common problem that can mask
the properties they exhibit when they encounter living tissue. According
to NIST physicist Darwin Reyes, these combined advantages should make
the new method especially useful in toxicology studies.
“Many
other methods of trapping require that you modify the surface of the
nanoparticles in some way so that you can control them more easily,”
Reyes says. “We take nanoparticles as they are, so that you can explore
what you’ve actually got. Using this method, you can release them into a
cell culture and watch how the cells react, which can give you a better
idea of how cells in the body will respond.”
Other
means of studying nanoparticle toxicity do not enable such precise
delivery of the particles to the cells. In the NIST method, the
particles can be released in a controlled fashion into a fluid stream
that flows over a colony of cells, mimicking the way the particles would
encounter cells inside the body—allowing scientists to monitor how
cells react over time, for example, or whether responses vary with
changes in particle concentration.
For
this particular study, the team used a gold surface covered by long,
positively charged molecules, which stretch up from the gold like wheat
in a field. The nanoparticles, which are also made of gold, are coated
with citrate molecules that have a slight negative charge, which draws
them to the surface covering, an attraction that can be broken with a
slight electric current. Reyes says that because the surface covering
can be designed to attract different materials, a variety of
nanoparticles could be captured and released with the technique.
