Improved point-of-care detection of P. gingivalis using optimized surface-enhanced Raman scattering in lateral flow assays

The introduction of surface-enhanced Raman scattering (SERS) in lateral flow assays (LFA) has been recently exploited to increase the sensitivity and quantification capabilities of these rapid tests. Herein, we took advantage of a SERS-LFA combination to improve LFAs designed to test for P. gingivalis, a biomarker for oral health. We have demonstrated a limit of detection (LOD) < 10 ng mL(-1), which is within the range of concentration needed to monitor oral health. By comparison, conventional colorimetric LFAs achieve an LOD approximate to 100 ng mL(-1), generating a lower diagnostic sensitivity. To achieve this enhanced sensitivity, we optimized the materials used in the SERS-LFA, investigating nanostars (NS) differing in size and material composition and comparing them to commercial gold nanoparticles, as a benchmark. We found that large (56 nm) NSs with a silver coating were the most sensitive nanomaterials for SERS-LFA. To prove the applicability of this SERS-LFA to point-of-care (POC) settings, we tested the optimized LFA with a portable Raman system prototype designed to work on LFAs with 3D-printed cartridges and a line-shaped laser illumination. Using this prototype, we achieved the same LOD observed with the traditional benchtop Raman system. The use of a portable Raman system has brought the SERS-LFA technology closer to the POC use.