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Creative Diagnostics offers a series of novel SpecNano™ gold nanostars, as a plasmonic core, for SERS-based lateral flow immunoassay. SpecNano™ gold nanostars, as one of the most important components of Surface-enhanced Raman scattering (SERS) tags, have unique characteristic: multi-arms and surface roughness features allows high SERS performance in the system to be achieved via the increased bioconjugation sites and hot spot regions. Surface-enhanced Raman scattering (SERS) have been developed in order to decrease the detection limit and enable the qualitative and quantitative analysis of analytes. In the assay, Surface-enhanced Raman scattering (SERS) tags needed new readout systems and signal processing algorithms, while the LFIA design remained unchanged, and a portable strip reader recording the color intensity of the band was used for quantitative analysis.
Creative Diagnostics offers a full product line of SpecNano™ gold nanostars (AuNS) for use in SERS-based Lateral Flow Immunoassay:
SERS-based Lateral Flow Immunoassay
ompared with conventional analytical methods, lateral flow assays (LFA) play an increasingly important role due to their advantages, such as cost-effectiveness, rapidity, easy operation, friendly use, and colorimetric readout. LFA strips usually consist of a nitrocellulose substrate that contains a series of functional areas, each of which stores a specific chemical reagent. Driven by capillary force, liquid samples transport along the LFA strips and react with the reagents. The presence of the target analyte causes a change in the output signal, whose intensity is measured for qualitative or semiquantitative analysis. Visual sensing is the most often used signal readout method for LFA tests. However, the application of visual LFA (VLFA) in point-of-care diagnosis and toxin analysis was severely limited by its lower sensitivity (usually mM to μM of detection limit) than other “wet-chemistry” techniques, such as enzyme-linked immunosorbent assays (ELISA) and high pressure liquid/gas chromatography-mass spectrometry (HPLC-MS/GC-MS).
Besides their unique color signal, gold nanoparticles also have specific properties including localized surface plasmon resonance (LSPR) and fluorescence quenching ability, which are considered promising assets for achieving high sensitivity of the quantitative analysis. The combination of SERS and LFIA shows promises in overcoming low sensitivity problem of conventional LFIA and lack of precision of signal measurement from optical or fluorescence signal reader. Amongst lots of gold nanoparticles, gold nanostars (AuNS) were dominant due to their tunable surface plasmon and multiple sharp branches. AuNS was applied to various substrates in order to produce the SERS active substrates for biosensing applications, for instance; paper-based SERS active substrate for detection of the oxidation products of apomorphine.
SERS tags consist of Au nanoparticles, serving as a plasmonic core, Raman-active molecules adsorbed or embedded in nanoparticles, and a protective polymer or inorganic layer, which is functionalized with recognizing antibodies. From a physicochemical point of view, SERS tags resemble simple colloidal gold, thus we can use them in the same LFIA design. On the other hand, from an optical point of view, SERS tags have several attractive advantages. First, the intensity of enhanced Raman scattering makes it possible to detect even a single SERS tag using a common optical technique; Second, the intensity of the SERS signal is proportional to the tag number in a wide range of concentrations; Finally, the narrow spectral bands of Raman scattering make it suitable for multiplexing. This has led to the emergence of a number of studies demonstrating significant increases in the sensitivity and dynamic range of LFIA using the SERS readout.
Sensitivity evaluation using various concentration of influenza A nucleoprotein (Recombinant nucleoprotein, rNP) from 0-6700 ng mL-1. (A) Signal visualization of the SERS-LFIA test strips with the limit of detection (LOD) of 67 ng mL-1. (B) SERS spectra obtained from the T line after applying different concentrations of the rNP. The limit of detection (LOD) was 6.7 ng mL-1 by determining the Raman shifts at 1086 and 1588 cm-1 (C) Quantitative analysis of the SERS-LFIA for rNP detection by calculating relative Raman intensity at 1086 and 1588 cm-1. Error bars represent standard deviations from three measurements.