SERS-based immunoassay based on gold nanostars modified with 5,5'-dithiobis-2-nitrobenzoic acid for determination of glial fibrillary acidic protein.

A surface-enhanced Raman scattering (SERS)-based immunoassay with gold nanostars (GNSs) is utilized for determination of the subarachnoid hemorrhage (SAH) biomarker glial fibrillary acidic protein (GFAP) at very low concentration levels, which allows for early diagnosis and guides clinical decision-making to treat SAH-induced complications. The Raman reporter 5,5'-dithiobis-2-nitrobenzoic acid (DTNB) modified on GNSs was selected as the SERS tags. The SERS immunoassay was assembled by SERS tag and GFAP probe-immobilized ITO substrate. Therefore, the level of GFAP can be detected by monitoring the characteristic Raman peak intensity of GFAP-conjugated GNSs at 1332 cm-1 with a very low detection limit. Under optimized conditions, the assay can work in the GFAP concentration range from 1 pg⋅mL-1 to 1 μg⋅mL-1, with a detection limit as low as 0.54 fg⋅mL-1. The performance of the SERS immunoassay proven by the detection of GFAP is equivalent to that of the conventional enzyme-linked immunosorbent assay (ELISA). Scheme 1. Schematic illustration of GNSs SERS immunoassay for ultrasensitive dynamic change detection of GFAP. (SAH: Subarachnoid hemorrhage, SCF: Cerebrospinal fluid; GNSs: gold nanostars; SERS: surface-enhanced Raman scattering; GFAP: glial fibrillary acidic protein).