Rapid, quantitative and ultra-sensitive detection of cancer biomarker by a SERRS-based lateral flow immunoassay using bovine serum albumin coated Au nanorods

Early diagnosis of cancer biomarkers is the key to guiding treatments and improving the survival rate of patients. Herein, we report a novel surface-enhanced resonance Raman scattering (SERRS)-based lateral flow immunoassay (LFIA) for quantitative and ultra-sensitive analysis of alpha-fetoprotein (AFP). Gold nanorods (AuNRs) were fabricated to be in resonance with 785 nm laser excitation, that is, the excitation level that can maximize SERRS activity. The AuNRs were modified with 5,5′-dithiobis(2-nitrobenzoic acid), bovine serum albumin (BSA), and AFP detection antibody successively as the SERRS nanotags for the LFIA system. Modification of the BSA layer guaranteed good stability and biocompatibility of the SERRS nanotags in complex samples. The SERRS-LFIA strip for AFP detection showed a low detection limit of 9.2 pg mL^-1 and a broad detection range from 10 pg mL^-1 to 500 ng mL^-1. By comparison, the detection limit of the proposed assay is about 100 and 10 times lower than those of the Au nanoparticle-based SERS-strip and conventional enzyme-linked immunosorbent assay, respectively. Moreover, the potential clinical applications of the assay were evaluated by detecting 10 actual serum samples. Results showed 100% accuracy based on the clinical tests.