An immunosensor designed for polybrominated biphenyl detection based on fluorescence resonance energy transfer (FRET) between carbon dots and gold nanoparticles

A novel assembled immunosensor was prepared for determining 4,4′-dibrominated biphenyl (PBB15), a small-size persistent organic pollutant. The immunosensing approach is based on fluorescence resonance energy transfer (FRET) between carbon dots (CDs) and gold nanoparticles (AuNPs), which act as energy donor and acceptor, respectively. The immunosensor consists of a specific combination of CDs-conjugated PBB15 antigen and AuNPs-modified anti-PBB15 antibody, applied in a homogenous assay system. Results showed that in the absence of PBB15, FRET between CDs and the AuNPs resulted in fluorescence intensity quenching. By contrast, fluorescence intensity was recovered in the presence of PBB15 as CD-labeled antigen and PBB15 competitively combined with antibody on the surface of AuNPs. Fluorescence intensity was proportional to PBB15 concentration in the range of 0.05-4 μg/mL, with a detection limit (LOD) of 0.039 μg/mL. The advantages of homogenous over heterogeneous immunoassays include the absence of repetitive washing and incubation steps. In this proposed assay, the procedure is quite simple and could be accomplished within 1 h. The immunosensor had excellent selectivity for PBB15 over other structural analogs. The proposed immunoassay was applied to determine PBB15 in biological samples, and the precision and recovery results were satisfactory. The high selectivity and short assay time of this designed immunosensor indicate its potential application in in situ and rapid detection. Furthermore, the strategy provided in this work could be conveniently followed to establish similar immunosensors for the rapid detection of small-sized organic pollutants with corresponding antigens and antibodies.