Engineer Tests Nanoparticles As Cancer Detection in Emory/Georgia
Shuming Nie is testing the use of nanoparticles called quantum dots
to improve clinical diagnostic tests for the early detection of cancer.
The tiny particles glow and act as markers on cells and genes, potentially
giving scientists the ability to rapidly analyze biopsy tissue from
cancer patients so that doctors can provide the most effective therapy
Nie, a chemist by training,
is an associate professor in the Wallace H. Coulter Department of Biomedical
Engineering at Georgia Tech and Emory University and director of cancer
nanotechnology at Emory's Winship Cancer Institute.
His research focuses on the
field of nanotechnolgy, in which scientists build devices and materials
one atom or molecule at a time, creating structures that take on new
properties by virtue of their miniature size. The basic building block
of nanotechnology is a nanoparticle, and a nanometer is one-billionth
of a meter, or about 100,000 times smaller than the width of a human
Nanoparticles take on special
properties because of their small size. For example, if you break a
piece of candy into two pieces, each piece will still be sweet, but
if you continue to break the candy until you reach the nanometer scale,
the smaller pieces will taste completely different and have different
Until recently, nanotechnology
was primarily based in electronics, manufacturing, supercomputers and
data storage. However, Nie predicted several years ago in a paper published
in Science that the first major breakthroughs in the field would
be in biomedical applications, such as early disease detection, imaging
and drug delivery.
"Electronics may be the field
most likely to derive the greatest economic benefit from nanotechnology,"
Nie said. "However, much of the benefit is unlikely to occur for another
10 to 20 years, whereas the biomedical applications of nanotechnology
are very close to being realized."
Nie was recently recruited
from Indiana University as a professor and researcher in the joint biomedical
engineering department established by Georgia Tech and Emory University.
While at Indiana, Nie and his colleagues constructed a nanoscale crystal.
Also called a quantum dot, this particle is made of semiconductors with
a limited ability to conduct electricity.
Because quantum dots are
so small, their electrons are compacted, causing them to emit light
or to act as a fluorescent tag. Quantum dots can bond chemically to
biological molecules, enabling them to trace specific proteins within
cells. Nie calls them "bioconjugated nanoparticles" -- small particles
that are chemically linked to biological materials.
Nanoparticle probes can be
used as contrast markers in magnetic resonance imaging (MRI), in positron
emission tomography (PET) for in-vivo molecular imaging, or they can
be used as fluorescent tracers in optical microscopy. These tags can
trace specific proteins in cells for cancer diagnosis or monitor the
effectiveness of drug therapy. Because the dots glow with bright, fluorescent
colors, scientists hope they will improve the sensitivity of diagnostic
tests for molecules that are difficult to detect, such as those in cancer
cells, or even the AIDS virus, Nie said.
"Basically, it is a barcoding
technology that can encode genes and proteins," Nie said. He plans to
use bioconjugated nanoparticles for early identification, quantification,
and localization of gene sequences, proteins, infectious organisms,
or genetic disorders.
Many of the practical applications
of nanoparticles are based on the different colors they absorb or emit
in the light spectrum as their sizes change. A piece of gold, for instance,
appears yellow in color, but appears red at nanoscale size. Broken down
even smaller, it could appear to be blue.
Using a spectrum of six colors,
in addition to four more colors in the infrared spectrum, scientists
are able to finely tune nanoparticles to carry out tracking tasks traditionally
accomplished using organic dyes. Nanoparticles have characteristics
that are more desirable than dyes, however. Dyes fade more quickly,
they can be toxic to cells, and they cannot be used together because
each dye requires a different light wavelength to be visible. Nanoparticles
can be illuminated using just one laser beam.
When scientists embed different
sized dots in tiny beads made of a polymer material, they can finely
tune the color of the bead. Theoretically, beads with tiny permutations
of color could tag a million different proteins or genetic sequences
in a process called "multiplexing."
Nie acts as a senior consultant
to Bioplex Corp., a company spun out of his laboratory's research in
Indiana. The company, which holds the exclusive license from Indiana
University for the synthesis of multiplexing dyes for imaging and detection,
was recently added to the roster of start-ups at EmTech Bio, a business
incubator jointly run by Georgia Tech and Emory University. Bioplex
Corporation is partially owned by Pittsburgh-based LaunchCyte.
Scientists, including Nie,
are currently studying methods of linking quantum dots to medical drugs
or other therapeutic agents to target cancer cells. These dots could
serve as "smart bombs" to deliver a controlled amount of drug to a particular
type of cell.
Nie is working with Emory
University cancer urologist Lelund Chung to use bioconjugated quantum
dots as molecular probes to rapidly analyze biopsy tissue from cancer
patients. The nanoparticles would be able to profile a large number
of genes and proteins simultaneously, allowing physicians to individualize
cancer treatments based on the molecular differences in the cancers
of various patients. Even when cells appear to be similar under the
microscope, their genes and proteins may be decidedly different, which
explains why cancer patients with apparently similar cancers sometimes
respond differently to the same treatment.
Nie and his colleagues are
working on methods to deliver nanoparticles into specific kinds of tissues
and cells -- a process that would make cancer therapy more selective.
Using near-infrared imaging technology, they are monitoring the migration
of the particles within cells.
Nie is also working with
tissue engineers at Georgia Tech and Emory to study the use of nanoparticles
to construct new materials that could be used as improved implants for
damaged tissue, such as bone, cartilage, or skin. Bio-nanomaterials
provide new opportunities in cell and tissue engineering, such as cell
growth/differentiation, tissue scaffolding, and controlled release of
multiple growth factors.