A novel FRET immunosensor for rapid and sensitive detection of dicofol based on bimetallic nanoclusters.

To minimize the need of complex testing procedures, accurate, rapid and selective on-site determination of dicofol (DICO) is of vital importance. Herein, fluorescence immunosensing platforms based on the Förster resonance energy transfer (FRET) between Au-Ag bimetallic nanoclusters (Au-Ag NCs) and Au nanoflowers (Au NFs) were developed for the rapid detection of DICO in both liquid system and paper-based analytical devices (PADs). Conjugations of Au-Ag NCs and antigen (NCs-Agen) and Au-Ag NCs were regarded as energy donors in liquid system and PADs, respectively, while conjugations of Au NFs and antibody (NFs-Ab) were synthesized as energy acceptors. The overlapping spectrum and decrease of fluorescence lifetime of NCs-Agen proved that the fluorescence quenching mechanism was FRET effect. When DICO was captured by NFs-Ab, FRET effect was inhibited due to the long distance between NFs-Ab and NCs/NCs-Agen. Under optimal conditions, the FRET-based fluorescent immunosensors allowed for a rapid response toward DICO with considerable sensitivities of 0.185 ng/mL and 0.170 ng/mL in liquid system and PADs, respectively. Excellent specificity and satisfactory recovery in three kinds of tea samples were confirmed as well. This study opens an avenue for on-site, portable and sensitive detection methods.