Fluorescence images of DNA-bound YOYO between coupled silver particles

Abstract

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.

Scheme 1

Coupling the Silver Particles by Hybridization with Target Oligonucleotide and Intercalating the YOYO into the DNA Duplex.

Figure 1

Normalized absorbance spectra of individual and aggregated oligonucleotide-bound silver particles through hybridization with target complementary oligonucleotides.

Figure 2

TEM images of (A) citrate-coated silver particles and (B) coupled silver particles by hybridization with target complementary oligonucleotides.

Figure 3

Representative fluorescence images of (A) unbound YOYO fluorescence image, (B) silver particle scattering images, (C) YOYO intercalated into an unbound DNA duplex in the absence of metal, and (D) YOYO intercalated into a bound DNA duplex between silica beads.

Figure 4

Representative single-point fluorescence time transients for free YOYO, intercalate YOYO in an unbound DNA duplex, intercalated YOYO in a DNA duplex bound between coupled silica beads, and intercalated YOYO in a DNA duplex between coupled silver particles.

Figure 5

Representative fluorescence images of (A) YOYO intercalated into a DNA duplex bound between silver particles and (B) the detail of these images.

Figure 6

Histograms of YOYO-labeled DNA in the absence of metal and between coupled silver particles. Note the intensity scale on the right is different from that in Figure 4.

Figure 7

Representative unfocused fluorescence images of YOYO intercalated into a DNA duplex bound between silver particles.

Figure 8

Emission decay curves and fits for YOYO intercalated into DNA duplexes unbound or bound between silica beads or silver particles.