Au-Fe3O4 dumbbell-like nanoparticles based lateral flow immunoassay for colorimetric and photothermal dual-mode detection of SARS-CoV-2 spike protein
Gengchen Guo, Tianyu Zhao, Ruichang Sun, Mingzhe Song, Hongyu Liu, Sen Wang, Jingwen Li, Jingbin Zeng
Abstract
Lateral flow immunoassay (LFIA) has become popular in laboratories, at-home testing, and medical diagnostics due to its minimal cost and user-friendliness. Nevertheless, conventional test strips based on colloidal gold can only obtain qualitative or semi-quantitative results with low sensitivity. In this work, Au-Fe 3 O 4 dumbbell-like nanoparticles were synthesized and used as the LFIA labelling marker for highly sensitive colorimetric-photothermal dual-mode detection of SARS-CoV-2 spike(S) protein. The unique dumbbell structure of Au-Fe 3 O 4 NPs makes it possible to combine the best features of both Au NPs and Fe 3 O 4 NPs. The increased surface area of these NPs enhances their LSPR effect and photothermal effect, which achieves signal amplification to increase sensitivity. The Au-Fe 3 O 4 NPs modified with S protein antibody could identify S protein in samples, which were recognized and accumulated on T-line by another antibody, generating color band for qualitative colorimetric detection . The T-line was irradiated by laser to obtain temperature change for quantitative detection of photothermal. In optimized conditions, the detection limit was 1.22 pg/mL, three orders of magnitude more sensitive than colorimetric detection. Finally, the approach was performed on SARS-CoV-2 pseudovirus samples and outperformed traditional colloidal gold strips. This LFIA platform exhibits significant promise for practical implementation, as it can satisfy the need for low-cost, high-sensitivity, and home-based quantitative detection for respiratory infectious diseases.