PSA Detection with Femtomolar Sensitivity and a Broad Dynamic Range Using SERS Nanoprobes and an Area-Scanning Method

Recently, surface-enhanced Raman scattering (SERS)-based immunoassays (SIA) have drawn much attention as diagnostic tools with large multiplex capacity and high sensitivity. However, several challenges-such as a low reproducibility, a time-consuming read-out process, and limited dynamic range-remain. In this study, we report a reliable and sensitive SIA platform for prostate specific antigen (PSA) detection. Reliability and sensitivity were achieved by two approaches: (1) well-established SERS probes, so-called SERS dots that have high sensitivity (single particle detection) and little particle-to-particle variation in SERS intensity; and (2) a whole area-scanning readout method for rapid and reliable chip analysis rather than point scanning. As a feasibility test, PSA could be detected with high sensitivity (ca. 0.11 pg/mL, 3.4 fM LOD), with a wide dynamic range (0.001-1000 ng/mL). Thus, the developed platform will facilitate development of reliable immunoassays with high sensitivity and a wide dynamic range.