|[March 20, 2014]
Shrink Wrap Used to Enhance Detection of Infectious Disease Biomarkers
WASHINGTON --(Business Wire)--
Detecting HIV/AIDS, tuberculosis, malaria and other deadly infectious
diseases as early as possible helps to prevent their rapid spread and
allows for more effective treatments. But current detection methods are
cost-prohibitive in most areas of the world. Now a new nanotechnology
method-employing common, everyday shrink wrap-may make highly sensitive,
extremely low-cost diagnosis of infectious disease agents possible.
Close-up image taken with a scanning electron microscope (SEM) showing the shrink wrap's surface with a fixed amount of gold (10 nm) and 5 nm thicknesses of nickel in the metal coating. Credit: Optical Materials Express.
The new technique, described in a paper published today in The Optical
Materials Express, offers a way to significantly boost the
signal of fluorescent markers used in biosensing, by depositing a
combination of metals onto shrink wrap.
"Using commodity shrink wrap and bulk manufacturing processes, we can
make low-cost nanostructures to enable fluorescence enhancements greater
than a thousand-fold, allowing for significantly lower limits of
detection," said co-author Michelle Khine, a biomedical engineering
professor at the University of California, Irvine (UC Irvine). "If you
have a solution with very few molecules that you are trying to detect-as
in the case of infectious diseases-this platform will help amplify the
signal so that a single molecule can be detected."
In the new method -- developed by Khine and her graduate student
Himanshu Sharma, along with their collaborators, Professors Enrico
Gratton and Michelle Digman, also at UC Irvine -- thin layers of gold
and nickel are first deposited onto a thermoplastic polymer (a shrink
wrap film). When heated, the shrink wrap contracs, causing the stiffer
metal layers to buckle and wrinkle into beautiful flower-like structures
that are significantly smaller than previously demonstrated. To the top
of the wrinkled metal layer, the researchers add samples of biomarkers,
antibodies generated by the immune system in response to infection with
a certain pathogen. These biomarkers are tagged with fluorescent probes
to allow their detection under near-infrared light.
The team found that the shrink wrap's wrinkles significantly enhanced
the intensity of the signals emitted by the biomarkers. The enhanced
emission, Khine says, is due to the excitation of localized surface
plasmons-coherent oscillations of the free electrons in the metal. When
researchers shined a light on their wrinkled creation, the
electromagnetic field was amplified within the nanoscale gaps between
the shrink wrap's folds, Khine said. This produced "hotspots"-areas
characterized by sudden bursts of intense fluorescence signals from the
In their study, the researchers used an immune system molecule known as
immunoglobin G, or IgG, as the biomarker. "IgG is one of the most common
circulating antibodies in the immune system, making up about 80 percent
of the all antibodies in the body, and is found in most bodily fluids,"
Sharma said. In particular, IgG is a good biomarker for the detection of
rotavirus, the virus that is the leading cause of severe diarrheal
infection in infants and young children worldwide. IgG is also a
biomarker for infection with the Epstein-Barr virus and Herpes simplex
In the future, he says, additional antibodies, such as immunoglobulin A
(IgA) and immunoglobulin M (IgM), might be used to detect other agents
including cytomegalovirus and the pathogen that causes typhoid fever.
"The technique should work with measuring fluorescent markers in
biological samples, but we have not yet tested bodily fluids," said
Khine, who cautions that the technique is far from ready for clinical
use. For example, she notes, "We are currently working on trying to
detect rotavirus, but one of the main challenges is that our surface is
hydrophobic"-that is, water-repelling-"so diffusion of the biomarker
onto our composite structures is limited."
Though their current setup requires the use of expensive equipment, the
researchers say, they believe their work will pave the way to creating
an integrated, low-cost device to trap and identify biomarkers.
Emission of Fluorophores on Shrink-Induced Wrinkled Composite Structures,"
H. Sharma et al., Optical Materials Express, Vol. x, Issue 4,
Issue 4, pp. 753-763 (2014)
EDITOR'S NOTE: High-resolution images are available to members of the
media upon request. Contact Lyndsay Meyer, email@example.com.
About Optical Materials Express
Optical Materials Express is OSA's peer-reviewed, open-access
journal focusing on the synthesis, processing and characterization of
materials for applications in optics and photonics. Optical Materials
Express primarily emphasizes advances in novel optical materials,
their properties, modeling, synthesis and fabrication techniques; how
such materials contribute to novel optical behavior; and how they enable
new or improved optical devices. It is published by The Optical Society
and edited by David J. Hagan of the University of Central Florida. For
more information, visit www.OpticsInfoBase.org/OMEx.
Founded in 1916, The Optical Society (OSA) is the leading professional
society for scientists, engineers, students and business leaders who
fuel discoveries, shape real-world applications and accelerate
achievements in the science of light. Through world-renowned
publications, meetings and membership programs, OSA provides quality
research, inspired interactions and dedicated resources for its
extensive global network of professionals in optics and photonics. For
more information, visit www.osa.org.
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