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- Johansson, Therese B., et al.
(author)
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Sub-Nanomolar Detection of Oligonucleotides Using Molecular Beacons Immobilized on Lightguiding Nanowires
- 2024
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In: Nanomaterials. - 2079-4991. ; 14:5
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Journal article (peer-reviewed)abstract
- The detection of oligonucleotides is a central step in many biomedical investigations. The most commonly used methods for detecting oligonucleotides often require concentration and amplification before detection. Therefore, developing detection methods with a direct read-out would be beneficial. Although commonly used for the detection of amplified oligonucleotides, fluorescent molecular beacons have been proposed for such direct detection. However, the reported limits of detection using molecular beacons are relatively high, ranging from 100 nM to a few µM, primarily limited by the beacon fluorescence background. In this study, we enhanced the relative signal contrast between hybridized and non-hybridized states of the beacons by immobilizing them on lightguiding nanowires. Upon hybridization to a complementary oligonucleotide, the fluorescence from the surface-bound beacon becomes coupled in the lightguiding nanowire core and is re-emitted at the nanowire tip in a narrower cone of light compared with the standard 4π emission. Prior knowledge of the nanowire positions allows for the continuous monitoring of fluorescence signals from each nanowire, which effectively facilitates the discrimination of signals arising from hybridization events against background signals. This resulted in improved signal-to-background and signal-to-noise ratios, which allowed for the direct detection of oligonucleotides at a concentration as low as 0.1 nM.
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| 3. |
- Unksov, Ivan N., et al.
(author)
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Semiconductor nanowires for biosening
- 2023
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In: European Biophysics Journal. - 1432-1017 .- 0175-7571. ; 52:SUPPL 1, s. S40-S40
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Conference paper (other academic/artistic)abstract
- Semiconductor nanowires are known to enhance the signal of fluorophores in their proximity. In our recent work, we optimized GaP nanowires to maximize the enhancement of fluorescence excitation. For that, we used optical microscopy to measure the fluorescence photobleaching rate on the nanowires, proportional to local excitation. From the measurements and modelling, we show for red fluorophores (excitation wavelength 640 nm) that nanowires with diameters of 90–130 nm enable enhancement of over a factor of 5 compared to bulk solution. We also demonstrate that a 10 nm oxide layer on the nanowires enables functionalisation using biotin-streptavidin chemistry without hindering the enhancement. Such nanowires were used in our laboratory to detect fluorescently-labelled proteins on a single molecule level. Now we employ these results for detection of down to nanomolar concentrations of DNA in solution, and in our poster, we discuss these biosensors.
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- Valderas Gutiérrez, Julia, et al.
(author)
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Enhanced Optical Biosensing by Aerotaxy Ga(As)P Nanowire Platforms Suitable for Scalable Production
- 2022
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In: ACS Applied Nano Materials. - : American Chemical Society (ACS). - 2574-0970. ; 5:7, s. 9063-9071
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Journal article (peer-reviewed)abstract
- Sensitive detection of low-abundance biomolecules is central for diagnostic applications. Semiconductor nanowires can be designed to enhance the fluorescence signal from surface-bound molecules, prospectively improving the limit of optical detection. However, to achieve the desired control of physical dimensions and material properties, one currently uses relatively expensive substrates and slow epitaxy techniques. An alternative approach is aerotaxy, a high-throughput and substrate-free production technique for high-quality semiconductor nanowires. Here, we compare the optical sensing performance of custom-grown aerotaxyproduced Ga(As)P nanowires vertically aligned on a polymer substrate to GaP nanowires batch-produced by epitaxy on GaP substrates. We find that signal enhancement by individual aerotaxy nanowires is comparable to that from epitaxy nanowires and present evidence of single-molecule detection. Platforms based on both types of nanowires show substantially higher normalized-to-blank signal intensity than planar glass surfaces, with the epitaxy platforms performing somewhat better, owing to a higher density of nanowires. With further optimization, aerotaxy nanowires thus offer a pathway to scalable, low-cost production of highly sensitive nanowire-based platforms for optical biosensing applications.
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