|NOTE TO JOURNALISTS:
A photo of Dmitri Litvinov alongside one of the tools used in this
research is available on the Web at http://www.uh.edu/media/nr/2007/02feb/020607dlitvinovph.html.
A high-resolution photo is available by contacting Lisa Merkl.
NEW MEDICATIONS, CANCER DIAGNOSIS GOALS
OF UH ENGINEERS WITH $1M IN GRANTS
Researchers Employ Nanomagnetic Sensor Technology
in Hopes of Simplifying Clinical Diagnostics
HOUSTON, Feb. 8, 2007 – Identifying new medications and
providing foolproof cancer diagnosis are two benefits anticipated
from research by a team of engineering professors at the University
A tabletop system capable of screening tens of thousands of drug
candidates in an hour and a tool that can provide a reliable cancer
diagnosis with minuscule quantities of tissue obtained through non-invasive
means are just two possible outcomes of research led by Dmitri Litvinov,
associate professor of electrical and computer engineering and of
chemical and biomolecular engineering in the Cullen College of Engineering
at UH. Along with his co-investigators Richard Willson, professor
of chemical engineering and biochemical and biophysical sciences,
and John Wolfe, professor of electrical and computer engineering,
Litvinov and his team received more than $1 million in grants from
the National Institutes of Health and the Alliance for NanoHealth.
Together, they are developing versatile technology that will enable
such breakthroughs as rapid evaluation of the effectiveness of potential
antiviral drugs by their ability to block a virus’ bond with
a cell receptor, as well as high-precision detection of cancer biomarkers
using molecular binding as a means for biorecognition. While it
is common to utilize these natural molecular binding processes to
identify biological agents, Litvinov’s research distinguishes
itself by how these processes are detected.
Usually scientists attach tags, also referred to as labels, to
biomolecules (proteins, DNAs or RNAs) that allow these biomolecules
to be tracked. This tracking tells researchers the location of the
biomolecules and whether the biomolecules have bonded with a specific
substrate, such as a healthy cell.
“Common tags used by researchers are fluorescent beads that
are detectable by their coloring, but many of the tags currently
used in research are much larger than the biomolecules being studied,”
Litvinov said. “Because of this, these tags often interfere
with the formation of bonds. This complicates research and brings
into question the accuracy of experiments.”
In Litvinov’s research, the tags are magnetic spheres measuring
about 50 nanometers – 1,000 times smaller than the width of
human hair. At such a size, they better conform to the size of the
biomolecules to which they are attached, thereby minimizing their
interference with the binding processes. While these spheres have
already been developed and are available to scientists, their small
size makes them extremely difficult to track and detect.
Litvinov, Willson and Wolfe are developing an array of magnetic-field
sensors capable of detecting the presence of these tiny magnetic
spheres. These sensors, dubbed giant magnetoresistive (GMR) sensors,
are widely used in the data storage industry and are small enough
that a million of them can be fit in a single square millimeter
This work is being done in the Center for Nanomagnetic Systems
that specializes in the development and application of novel magnetic
materials and devices at nanoscale dimensions, such as those directly
related to current and future magnetic storage technologies.
For applications in antiviral drug development, the GMR sensors
will be coated with cell receptors that bind with a specific virus
protein. When the virus protein bonds with the cell receptor, these
sensors will detect magnetic spheres, letting researchers know that
a bond has occurred. Should an antiviral drug be added to the mix,
it will block the cell receptors, preventing them from binding with
the virus protein. For example, virus proteins will bind with cell
receptors in the body to generate infections. The process imitates
the biological development of illnesses within the body.
It is this process that will enable Litvinov’s tool to screen
potential drug candidates. By adding potential medications to a
mixture containing viruses, the GMR sensor array will, in effect,
detect whether a drug blocks a particular virus from binding with
a cell receptor. If it does, further clinical trials with the drug
likely will follow. Because so many sensors can reside in a small
area, hundreds – even thousands – of drug candidates
can be screened at once, cutting down the time it takes to bring
new drugs to market. In addition to testing the viability of potential
drug candidates, the technology being developed by Litvinov’s
team also may be put to use in other areas of health care.
Though this technology initially is funded for drug development,
it can be used for other high-throughput molecular screening applications,
such as in cancer studies. Such an application would work in a similar
way as the tests for potential drug candidates. A small biological
sample suspected of being cancerous would be extracted from a patient
using a nearly painless technique – fine needle aspiration.
Nanoparticles known to bond with that particular form of cancer
would then be exposed to the biological sample, and medical professionals
would be able to determine if cancer is present depending on whether
or not the nanoparticles and biological samples bond. Should bonding
occur, the presence of cancerous cells would be confirmed.
The key advantage of such a system, Willson said, is that it would
combine the non-invasive nature of fine needle aspiration with the
reliability of conventional highly invasive techniques, such as
open surgery. This would provide results with far greater accuracy
than traditional testing methods.
“The way they evaluate fine needle aspiration biopsies for
the presence of cancer is by looking at a biological sample under
a microscope, relying heavily on the experience of the person evaluating
the sample and the quality of the sample,” he said. “Here,
the idea is to automate the process to make it foolproof and eliminate
the human-error factor without resorting to surgery.”
Whether used as a diagnostic tool or to screen drug candidates,
the use of GMR sensors in medical applications has the potential
to simplify many areas of medical research.
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