A SERS-based lateral flow assay for the stroke biomarker S100-β

A surface-enhanced Raman scattering (SERS)-based lateral flow assay (LFA) is described for the quantitative analysis of the proteinic stroke biomarker S100-β that has to be detected at very low concentration levels. The Raman reporter 5,5'-dithiobis-2-nitrobenzoic acid (DTNB) on gold nanoparticles (GNPs) was employed as the SERS tags. They are shown to perform much better than bare GNPs in LF strips. The S100-β protein can be detected by this method with very low detection limits by monitoring the intensity of the characteristic Raman peak of the S100-β protein-conjugated GNPs at 1332 cm^-1. Under optimized conditions, the assay works in the 1 pg·mL^-1 to 40 ng·mL^-1 S100-β concentration range, and the detection limit is as low as 0.14 pg·mL^-1. This is lower by a factor of 3 compared to colorimetric or fluorimetric methods. Graphical abstract Schematic illustration of the configuration (A) and the principle of the SERS-based lateral flow assay for quantification of S100-β (B).