Wash – In a mixing of pasta metaphors, Pacific Northwest
National Laboratory scientists have used electrostatic
attraction to layer reactive biological molecules
lasagna-like around spaghetti-like carbon nanotubes.
The configuration can accommodate a wide range of
applications, from ultra-precise blood-sugar monitoring
to infectious-agent detection, said Yuehe Lin, who
led the research at the Department of Energy campus'
W.R. Wiley Environmental Molecular Sciences Laboratory.
The technique, described in the April Journal of
Nanoscience and Nanotechnology, enables enzymes,
with the help of a long, noodle-like polymer molecule,
to self-assemble layer-by-layer on a single carbon
Lin and co-author Guodong Liu, a postdoctoral fellow
in Lin's group, coaxed electrostatic clinginess in
a polymer and an oppositely charged protein-enzyme,
in this case glucose oxidase, which reacts in the
presence of blood sugar. The catalyzed products from
the reaction ping the carbon nanotube; if the tube
is connected to an electrode, the tube will carry
a signal that corresponds precisely with the amount
of glucose detected. The first polymer binds to the
carbon nanotube. Enzymes are attracted to the polymer,
leaving an outer layer for the next polymer of opposite
charge to cling to, and so on.
individual strand coated with one to six layers
ranges from 30 nanometers to about 50 nanometers
thick. “Each polymer layers is porous,” Lin said. “This
allows the glucose to diffuse in and come into contact
with the enzymes.”
“The polymers trap the enzymes in place,” Liu said. “You
can go up to five or six layers to improve the sensitivity
of the detector, but after that, the more enzyme
layers” inhibit diffusion of the glucose.
Now that the glucose enzyme biosensor has passed
the test, Lin said, it should be possible to build
a similar sensor using other enzymes that react specifically
with other biological chemicals, environmental pollutants
or even microbes and their toxic byproducts. Lin
and colleagues also reported, in February issue of
Analytical Chemistry, having used a similar technique
to construct sensors for nerve agents.
The research was funded through PNNL's environmental
biomarker initiative . PNNL is
a DOE Office of Science laboratory that solves
complex problems in energy, national security,
the environment and life sciences by advancing
the understanding of physics, chemistry, biology
and computation. PNNL employs more than 4,200,
has an annual budget of more than $725 million
annual budget, and has been managed by Ohio-based
Battelle since the lab's inception in 1965.