Letter pubs.acs.org/acssensors
PSA Detection with Femtomolar Sensitivity and a Broad Dynamic Range Using SERS Nanoprobes and an Area-Scanning Method Hyejin Chang,† Homan Kang,‡,# Eunbyeol Ko,† Bong-Hyun Jun,§ Ho-Young Lee,*,∥ Yoon-Sik Lee,*,⊥ and Dae Hong Jeong*,† †
Department of Chemistry Education, ‡Interdisciplinary Program in Nano-Science and Technology, and ⊥School of Chemical and Biological Engineering, Seoul National University, Seoul 08826, Republic of Korea § Department of Bioscience and Biotechnology, Konkuk University, Seoul 05029, Republic of Korea ∥ Department of Nuclear Medicine, Seoul National University Bundang Hospital, Seongnam 13620, Republic of Korea S Supporting Information *
ABSTRACT: 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 challengessuch as a low reproducibility, a time-consuming read-out process, and limited dynamic rangeremain. 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. KEYWORDS: surface-enhanced Raman scattering (SERS), immunoassay, prostate specific antigen (PSA), SERS nanoprobe, area-scanning
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However, the area of each point is only ∼1 μm2, and so a large unscanned area is left when the spot-sampling is utilized. This unscanned area reduces signal reliability due to the heterogeneous distribution of nanoprobes on the substrate. To address this problem, a reliable read-out strategy using a whole-area raster scanning method over the entire chip area without spot sampling has been developed.17 Prostate-specific antigen (PSA), a serine protease, is used for diagnosis of carcinoma of the prostate (CaP). CaP usually causes an elevation of the blood PSA level of up to 105-fold (the normal cutoff value in serum is
