Recent advances in homogenous immunoassays based on resonance energy transfer.

Development of homogeneous immunoassays based on Förster resonance energy transfer (FRET), chemiluminescence resonance energy transfer (CRET) or bioluminescence resonance energy transfer (BRET) enables a one-step, rapid and direct detection of analytes as compared to the multistep, time-consuming heterogeneous immunoassays. Antibody fragments such as Fab or F(ab)2 are extensively exploited in both competitive and non-competitive formats to circumvent the size limitations characteristic of full-length antibodies. Semiconductor fluorescent nanocrystals, quantum dots are becoming increasingly popular as energy acceptors due to their beneficial optical properties as compared to organic dyes. These and other technical advances open new ways for using homogenous immunoassays in a variety of bioanalytical applications including detection of protein biomarkers, hormones, drugs of abuse, food and environmental toxins.