Multi-wavelength and multicolor immunoassay for sensitive detection of fluorene based on silver deposition on the surface of gold nanorods

Fluorene, a kind of polycyclic aromatic hydrocarbons (PAHs), was harmful to human health. In this work, a multi-wavelength and multicolor immunoassay was established for detecting fluorene based on the gold nanorods (AuNRs) growth. In the target recognition, fluorene was recognized by monoclonal antibody (McAb) through a competitive immune response. Then, the alkaline phosphatase-labeled Goat anti-Mouse IgG (ALP-IgG) as secondary antibody was used to combine with McAb. In signal output, ALP-IgG was used to catalyze 4-aminophenylphosphate to 4-aminophenol which can reduce Ag(I) to Ag(0). Then, the Ag(0) can deposit on the surface of AuNRs to cause the AuNRs growth. Along with the AuNRs growth, the absorption wavelength of the AuNRs was blue shifted and the color changed accordingly. The linear range of this immunoassay for fluorene was 0.063–4.000 ng/mL with the limit of detection (LOD) of 0.035 ng/mL. This immunoassay had excellent selectivity for fluorene according to the fact that it can distinguish fluorene among 16 PAHs. Meanwhile, this proposed immunoassay had a potential to detect fluorene in different water samples with satisfactory recovery rates (83 %–96 %).