Enhanced Forster resonance energy transfer (FRET) on a single metal particle

We examined the effect of a metallic silver particle on Forster resonance energy transfer ( FRET) between a nearby donor-acceptor pair. A donor-labeled oligonucleotide was chemically bound to a single silver particle, and then an acceptor-labeled complementary oligonucleotide was conjugated by hybridization. The photophysical behavior of FRET between the donor-acceptor pair on the metal particle was investigated using both ensemble emission spectra and single-molecule fluorescence detections. Both the emission intensities and lifetimes indicated an enhanced FRET efficiency due to the metal particle. This interaction led to an increase in the Forster distance for energy transfer from 8.3 to 13 nm. The rate constant of FRET near the silver particle was 21 times faster than that of unbound donor-acceptor pairs. These results suggest the use of metal-enhanced FRET for measuring proximity of large biomolecules or for energy-transfer-based assays.