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 ≈ 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.