Abstract
In this work, it is shown that surface-enhanced Raman scattering (SERS) measurements can be performed using liquid platforms to perform bioanalysis at sub-pM concentrations. Using magnetic enrichment with gold-coated magnetic nanoparticles, the high sensitivity was verified with nucleic acid and protein targets. The former was performed with a DNA fragment associated with the bacteria Staphylococcus aureus, and the latter using IgG antibody, a biomarker for COVID-19 screening. It is anticipated that this work will inspire studies on ultrasensitive SERS analyzers suitable for large-scale applications, which is particularly important for in vitro diagnostics and environmental studies.
Highlights
Surface-enhanced Raman scattering (SERS) spectroscopy holds promises for ultrasensitive detection of analytes in complex environments (Ding et al, 2016; Langer et al, 2020)
This study can be summarized as follows: (1) magnetic enhancements significantly improve the sensitivity of liquidstate SERS by lowering the limit of detection (LoD) by at least three orders of magnitude to enable pM-level detection of biomolecules
(2) The LoD for nucleic acid targets was determined by using DNA fragments associated with Staphylococcus aureus, a bacteria associated with crossinfections in hospitals
Summary
Surface-enhanced Raman scattering (SERS) spectroscopy holds promises for ultrasensitive detection of analytes in complex environments (Ding et al, 2016; Langer et al, 2020). Of interest is recent studies showing that well-defined SERS substrates can be produced directly in the liquid-state via self-assembling gold nanoparticles between the phases of immiscible solvents (Ma et al, 2016; Tian et al, 2018; Du et al, 2019; Su et al, 2019) This is attractive as gold colloids can be obtained and it provided a simple and reproducible method to perform SERS at minimal cost. Using a signature peak in Alexa 488, which occurred at 1,306 cm−1, corresponding to the amide stretch (Chen et al, 2011), a clear linearity between peak intensity and analyte concentration was seen between ∼0.5 and ∼500 pM, a detection range inaccessible to current liquid-SERS measurements In this case, an LoD was found to be ∼0.37 pM using the S/N ratio of 3. Nano star SERS (Indrasekara et al, 2014; Li et al, 2021) Single-molecule SERS (Yang et al, 2016; Li et al, 2021)
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