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Proceedings Paper

Enhanced molecular beacon based DNA detection using plasmonic open-ring nanoarrays
Author(s): A. Kannegulla; Y. Liu; B. Wu; L.-J. Cheng
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Paper Abstract

Molecular beacon (MB) probe is a fluorophore-labeled oligonucleotide and has been widely used in biological analysis and medical diagnostics by detecting DNA or RNA with specific sequences. The MB initially folds into a loop shape that brings the fluorophore close to a quencher for fluorescence quenching. It opens up upon the binding of target DNA that separates the fluorophore from the quencher to allow fluorescence emission. In this paper, we experimentally demonstrate the use of a silver open-ring nanostructure array (ORA) to enhance both fluorescence emission and quenching of MBs for highly sensitive DNA detection. The ORA displays a broadband resonance spectrum to enhance both the excitation and emission of fluorophores. The fluorescence enhancement is highly dependent on the distance between nanostructure and fluorophore. The couplings of the fluorescence emission and the external excitation with the proximate plasmonic nanostructure result in coherent electron oscillations that in turn act as secondary excitation of the fluorophore in a ~10 nm separation distance, leading to fluorescent enhancement. The resonance feature of ORA also improved the Förster resonance energy transfer between the fluorophore and ORA in an even shorter separation distance that promotes the fluorescence quenching. The enhanced fluorescence emission and quenching amplified the on-off ratio of the detection signal. The sensor was integrated into a microfluidic chamber to handle microliter-volume analyte and achieved a ~300 fM detection limit, an equivalent 360 zmol in a 1.2 μL analyte volume, superior to the detection on plane silver surfaces.

Paper Details

Date Published: 5 September 2018
PDF: 6 pages
Proc. SPIE 10728, Biosensing and Nanomedicine XI, 107280E (5 September 2018); doi: 10.1117/12.2321234
Show Author Affiliations
A. Kannegulla, Oregon State Univ. (United States)
Y. Liu, Oregon State Univ. (United States)
B. Wu, Oregon State Univ. (United States)
L.-J. Cheng, Oregon State Univ. (United States)

Published in SPIE Proceedings Vol. 10728:
Biosensing and Nanomedicine XI
Hooman Mohseni; Massoud H. Agahi; Manijeh Razeghi, Editor(s)

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