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Posted: Jun 06, 2006

Researchers use nanoscale zinc oxide structures to detect anthrax

(Nanowerk Spotlight) A new approach by scientists at Penn State greatly promotes the use of zinc oxide (ZnO) nanomaterials as signal enhancing platforms for rapid, multiplexed, high-throughput, highly sensitive, DNA sensor arrays. They report that engineered nanoscale ZnO structures can be effectively used for the identification of the biothreat agent, Bacillus anthracis, by successfully discriminating its DNA sequence from other genetically related species.
In their recent work ("Ultrasensitive DNA sequence detection using nanoscale ZnO sensor arrays"), published in the May 26, 2006 online edition of Nanotechnology, Professor Jong-in Hahm from the Department of Chemical Engineering at Penn State, together with first author Nitin Kumar, and co-author Adam Dorfman, explore both covalent and non-covalent linking schemes in order to couple probe DNA strands to the zinc oxide nanostructures.
The Penn State researchers found that the use of ZnO nanomaterials greatly enhances the fluorescence signal collected after carrying out duplex formation reaction. They point out that, specifically, the covalent strategy allows detection of the target species at sample concentrations as low as a few femtomolar level as compared to the detection sensitivity in tens of nanomolar range when using the non-covalent scheme.
"The presence of the underlying ZnO nanomaterials is critical in achieving increased fluorescence detection of hybridized DNA and, therefore, accomplishing rapid and extremely sensitive identification of the biothreat agent" Hahm says.
Innovative assembly and fabrication of nanomaterials for use as advanced biosensor substrates can be greatly beneficial in increasing the detection sensitivity of biomolecular fluorescence. ZnO nanostructures have received considerable attention particularly due to their desirable optical properties, which include a wide band gap of 3.37 eV and a large exciton binding energy of 60 meV at room temperature. ZnO has been previously demonstrated as a candidate material for use in a broad range of technological applications. Examples of ZnO materials in these areas include short-wavelength light-emitters, field-emitters, luminescence devices, UV lasers, and solar cells.
Hahm explains: "Nanometer scale ZnO has very good potential for aiding optical detection of target bioconstituents as ZnO nanomaterials are stable in typical biomolecular detection environments, have attractive optical properties, and can be easily processed through many synthetic routes. Despite its demonstrated functions in broad areas and suitability for advanced optical detection, biosensing applications of wide bandgap ZnO have not yet been extensively realized. For the first time, our findings report the successful use of ZnO nanostructured materials as biosensor platforms."
Hahm and her team also demonstrated the easy integration potential of the nanoscale ZnO materials into high density arrays directly upon their synthesis.
"Our synthesis method can be easily modified for seamless integration with current manufacturing processes for commercial production of bioarrays or biochips" she says. "When combined with conventional automatic sample handling apparatus and computerized fluorescence detection equipment, our approach can greatly promote the use of ZnO nanomaterials as signal enhancing substrates for multiplexed, high-throughput optical DNA sensor arrays."
"We are looking into the exact ZnO nanostructure-enabled fluorescence enhancement mechanisms&q Hahm explains her group's next steps. "We are also testing detection sensitivity of our ZnO nanoplatforms using other important biomolecules such as proteins and cells."
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