2008 NSTI Nanotechnology Conference and Trade Show - Nanotech 2008 - 11th Annual

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TechConnect Summit
Clean Technology 2008

Behind the Scenes of a Non-Cross-Linking Au-Nanoprobes Nucleic Acids-Detection Assay

G. Doria, R. Franco, P. Eaton, N. Santos, P. Baptista

gold nanoparticles, nucleic acids, nanodiagnostics

For more than a decade, derivatization of gold nanoparticles with thiol modified oligonucleotides (Au-nanoprobes) lead to a new era of molecular nanodiagnostics. Based on these Au-nanoprobes we developed a simple, easy-to-use and inexpensive colorimetric assay that allows for a fast and sensitive detection of specific nucleic acids’ sequences. Detection is based on color alteration upon salt addition to solutions containing the Au-nanoprobes and either complementary or mismatched/non-complementary targets: in presence of fully complementary targets the solution remains red; aggregation of Au-nanoprobes and concomitant color change to blue occurs in presence of non-complementary sequences or targets harboring single base mismatches. The color change can be followed by naked eye or UV-Vis spectroscopy. The assay has been successfully applied to eukaryotic gene expression studies without retro-transcription or PCR amplification; in a fast assay for Mycobacterium tuberculosis DNA detection in clinical samples; to detect single point mutations within -globin gene responsible for -thalassemia; as well as other human single nucleotide polymorphisms (SNPs). Using fluorescent spectroscopy, atomic force microscopy and zeta potential measurements, our efforts have been focused on elucidating the underlying mechanism of this assay. We determined that room temperature stability of the Au-nanoprobes is enhanced when hybridization occurs with the fully complementary DNA and/or RNA targets in solution, due to a higher number of negatively charged DNA molecules hybridized to the Au-nanoprobes, when compared to the hybridization of mismatched/non-complementary targets.

Nanotech 2008 Conference Program Abstract