Highly sensitive and rapid technology of surface enhanced Raman scattering (SERS) was applied to create aptasensors for influenza virus detection. SERS achieves 10 6 −10 9 times signal amplification, yielding excellent sensitivity, whereas aptamers to hemagglutinin provide a specific recognition of the influenza virus. Aptamer RHA0385 was demonstrated to have essentially broad strain-specificity toward both recombinant hemagglutinins and the whole viruses. To achieve high sensitivity, a sandwich of primary aptamers, influenza virus and secondary aptamers was assembled. Primary aptamers were attached to metal particles of a SERS substrate, and influenza viruses were captured and bound with secondary aptamers labelled with Raman-active molecules. The signal was affected by the concentration of both primary and secondary aptamers. The limit of detection was as low as 1 · 10 −4 hemagglutination units per probe as tested for the H3N2 virus (A/England/42/72). Aptamer-based sensors provided recognition of various influenza viral strains, including H1, H3, and H5 hemagglutinin subtypes. Therefore, the aptasensors could be applied for fast and low-cost strain-independent determination of influenza viruses.
During the COVID-19 pandemic, the development of sensitive and rapid techniques for detection of viruses have become vital. Surface-enhanced Raman scattering (SERS) is an appropriate tool for new techniques due to its high sensitivity. SERS materials modified with short-structured oligonucleotides (DNA aptamers) provide specificity for SERS biosensors. Existing SERS-based aptasensors for rapid virus detection are either inapplicable for quantitative determination or have sophisticated and expensive construction and implementation. In this paper, we provide a SERS-aptasensor based on colloidal solutions which combines rapidity and specificity in quantitative determination of SARS-CoV-2 virus, discriminating it from the other respiratory viruses.
Viral infections are among the main causes of morbidity and mortality of humans; sensitive and specific diagnostic methods for the rapid identification of viral pathogens are required. Surface-enhanced Raman spectroscopy (SERS) is one of the most promising techniques for routine analysis due to its excellent sensitivity, simple and low-cost instrumentation and minimal required sample preparation. The outstanding sensitivity of SERS is achieved due to tiny nanostructures which must be assembled before or during the analysis. As for specificity, it may be provided using recognition elements. Antibodies, complimentary nucleic acids and aptamers are the most usable recognition elements for virus identification. Here, SERS-based biosensors for virus identification with oligonucleotides as recognition elements are reviewed, and the potential of these biosensors is discussed.
Development of sensitive techniques for rapid detection of viruses is on a high demand. Surface-enhanced Raman spectroscopy (SERS) is an appropriate tool for new techniques due to its high sensitivity. DNA aptamers are short structured oligonucleotides that can provide specificity for SERS biosensors. Existing SERS-based aptasensors for rapid virus detection had several disadvantages. Some of them lacked possibility of quantitative determination, while others had sophisticated and expensive implementation. In this paper, we provide a new approach that combines rapid specific detection and the possibility of quantitative determination of viruses using the example of influenza A virus.
The long-range action of surface-enhanced Raman scattering (SERS) is probed via distancedependent measurements of molecular Raman spectra. To this end, identical SERS substrates composed of irregular silver nanoisland arrays were covered by dielectric spacer layers with variable thickness, and the strength of the SERS signal produced from analyte molecules deposited on top of the structure was analyzed. The obtained distance dependence of the signal strength exhibited a shelf-like behavior up to 30 nm away from the enhancing surface and then rapidly decreased further away. Thus, the observed behavior of the electromagnetic mechanism of SERS enhancement in metal island films contradicts the widely accepted picture of extremely rapid (2-3 nm) decay of SERS-enhancement of 2D nanoparticle ensembles. Because of the observed steady enhancement factors at distances of ∼30 nm from the surface, SERS can be used for probing the spectra of macromolecules or other objects relatively distant from the metal surface. PACS numbers:Since its first observation by Fleischmann et al.(1974) 1 surface-enhanced Raman scattering (SERS) has been thoroughly investigated as an amazing physical phenomenon itself and one of the most promising tools for analytical applications. The first perception of SERS as a giant enhancement over conventional Raman scattering in experiments of Jeanmaire, Van Duyne 2 and Albrecht, Creighton 3 was followed by an extensive theoretical and experimental analysis, searching for the most general explanation of the enhancement mechanism. The enhancement of Raman scattering signals from organic molecules absorbed on nanostructured metal surfaces and photoexcited in a certain spectral range has been shown to reach 6-10 orders of magnitude 2,4 . Further enhancement of up to ∼14 orders of magnitude was observed on molecules residing in silver colloidal aggregates, enabling single molecule detection 5 . It is now generally agreed that more than one effect contributes to the total enhancement of Raman signals. The enhancement mechanisms are roughly divided into so-called electromagnetic (EM) field enhancement 6-8 and chemical first-layer effects 9-11 . The electromagnetic enhancement is caused by the enhanced local optical fields at the place of the molecule nearby the metal surface due to excitation of electromagnetic resonances, called surface plasmon polaritons. For isolated silver or gold spheroidal nanoparticles typical values for electromagnetic enhancement of SERS are on the order of 12,13 10 6 − 10 7 . For the more sophisticated case of closely spaced interacting particles (or clusters of particles), the individual dipole oscillators of the small particles couple, thereby generating normal modes of plasmon excitation that embrace the cluster. According to theoretical evaluations, the excitation is not distributed uniformly over the cluster but tends to be spatially localized in so-called "hot" areas [14][15][16] . Effects of chemical enhancement arise from the electronic coupling between the adsorbate molecule...
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