Time-Resolved FRET-Based Immunosensor for the Ultrasensitive and Rapid Detection of Cd²

The detection of heavy metals in food is beneficial to public health. Herein, a new time-resolved fluorescent immunosensor based on the Förster resonance energy transfer (FRET) was proposed to rapidly detect a cadmium ion (Cd²⁺). After coupling with an antigen and a monoclonal antibody (mAb), respectively, the synthesized europium (III)-chelate-doped polystyrene time-resolved fluorescence microsphere-antigen (Eu-antigen) and gold nanoflowers-mAb (GNFs-mAb) interacted by antigen-antibody combination to quench fluorescence through FRET. Under optimal conditions, the Eu-GNF immunosensing platform provided a quick response to Cd²⁺ within 30 min. The limit of detection was 0.29 ng/mL with a linear range of 1-500 ng/mL. This immunosensor was further validated via graphite furnace atomic absorption spectrometry and exhibited satisfactory recovery for the detection of Cd²⁺ in four kinds of tea samples (98.82-108.01%). Thus, this strategy provides a good paradigm for the rapid and high-throughput detection of heavy metals in field testing.