Fluorescence images of DNA-bound YOYO between coupled silver particles.

Oligonucleotide-bound silver particles were coupled through hybridization with target complementary oligonucleotides. YOYO molecules were intercalated into DNA duplexes bound between the coupled metal particles. Fluorescence images of YOYO molecules were monitored by scanning confocal microscopy. Relative to the free single YOYO, the emission brightness of the image was enhanced 80-fold after intercalating the fluorophores into the DNA duplexes between the coupled silver particles. Some images of the labeled metal particle dimers were observed to be dumbbell-shaped, suggesting that the stretching of intercalated YOYO molecules was restricted because of the orientation effect of fluorophores. The shortened lifetime of YOYO molecules between the coupled metal particles indicated that the fluorescence was enhanced via a near-field interaction mechanism between the fluorophore and the metal nanoparticle.