In this work, a simple and sensitive approach for detection of prostate-specific antigen (PSA) based on the fluorescence resonance energy transfer (FRET) from cadmium telluride (CdTe) quantum dots (QDs) to gold nanoparticles (AuNPs)-polyamidoamine (PAMAM) is described. In this FRET system, CdTe QD modified with antibody (Ab) acts as donor and aptamer decorated PAMAM-AuNPs is used as acceptor in the QDs-Ab/AuNPs- PAMAM/aptamer system. Detection of PSA is achieved by monitoring immunocomplex between PSA and aptamer, while the fluorescence intensity of CdTe QDs decreased during PSA addition. A linear relationship between the concentrations of the PSA antigen and the fluorescence-quenching intensities is obtained when QDs is closed to the AuNPs surface as a result of sandwich structure of QDs-Ab/PSA/AuNPs-PAMA/aptamer. Under the optimized conditions, the linear range of PSA antigen is extended from 0.01 ng mL−1 to 100 ng mL−1 with limit of detection (LOD) of 1 pg mL−1. A superior sensitivity is achieved due to the superior fluorescence properties of CdTe QDs along with highly loading ability of dendrimer and high selectivity of sensor toward PSA displayed due to more specificity of aptamer. The presented assay was further applied for PSA detection in human serum samples with satisfactory results. Due to high selectivity, simplicity and sensitivity of the proposed strategy, it could be developed for sensing of other targets by varying the recognition probes.
