Fluorescently Labeled Gold Nanoparticles with Minimal Fluorescence Quenching

Abstract

Minimal quenching of fluorescence emission was observed when the fluorescent dye AlexaFluor 514 (AF514) was covalently bound to gold monolayer protected clusters (AuMPCs) that have negligible plasmon bands (diameters <2 nm). The fluorescence emission of the conjugated dye was measured as a function of dye-AuMPC mixing ratio with a combination of steady-state and time-resolved ensemble spectroscopic measurements in conjunction with single-molecule fluorescence microscopy. Fluorescence emission of the conjugated samples decreased slightly as a function of dye mixing ratio, which, in combination with a negligible change in fluorescence lifetime, was attributed to static quenching of the dye by the AuMPCs. From the single-molecule fluorescence measurements, it was observed that luminescent conjugates could still be detected, and, at all loading ratios, almost all of the dye-particle conjugates photobleached in either a single-or doublestep process, with a small subpopulation exhibiting more than two photobleaching events. Beyond simple, irreversible photobleaching, no additional blinking dynamics were detected at the single-molecule level within the time resolution of the experiment. Emission intensities of coupled fluorophores were comparable with those measured of dye molecules that had not been attached to the AuMPCs, suggesting that the statically quenched fluorophores are entirely nonemissive, whereas the remaining dyes are essentially unquenched. These results are discussed in the context of other dye-AuMPC coupled systems described in the literature.

Development and Characterization of an Antibody-Labeled Super-Paramagnetic Iron Oxide Contrast Agent Targeting Prostate Cancer Cells for Magnetic Resonance Imaging

“…Fluorescence intensity measurements were performed routinely as quality control assessment measure following each synthesis experiments and to determine the overall loading concentration. Our results agree with previous reports that indirectly suggest that the solvent polarity and proximity of quenching species to the metal-fluorophore conjugation system may play a role in the fluorescence quenching [35] .…”

“…Fluorescence quenching and emission enhancement have been reported for metal-fluorophore conjugate systems [35] . We determined that fluorescent quenching occurred in our system by comparing the fluorescence intensity and peak λ max of MIRB alone and muJ591:MIRB complex ( Figure 3 ).…”

Kinetics and mechanism of sodium (Z)-3-(5-chloro-2-((5-chloro-3-(3-sulfonatopropyl) benzothiazol-2(3H)-ylidene)methyl)benzo-thiazol-3-ium-3-yl)propane-1-sulfonate adsorption on gold nanoparticle colloids of different properties and size

“…Lu sa saradnicima je istraživao fluorescentno obeležene nanočestice zlata gde je primećen efekat unutrašnjeg filtera pri čemu je došlo do minimalnog gašenja fluorescencije fluorofore [240]. Poznati su i opisani u literaturi i drugi primeri smanjenja intenziteta fluorescencije fluorofore u prisustvu nanočestica zlata uz primenu korekcije za efekat unutrašnjeg filtera [241][242][243].…”

“…U literaturi [1,17,77,240,244,346,347] je opisano mnogo primera gde se gašenje (engl. quenching) pobuđenog stanja hromofore pripisuje prenosu energije ka površini metalne čestice.…”

“…Ovo gašenje fluorescencije se generalno pripisuje povećanoj neradijativnoj relaksaciji pobuđenog stanja usled prenosa energije i/ili prenosa elektrona [323,17]. U literaturi su opisani primeri gde je u slučaju fluorescentno obeleženih nanočestica zlata došlo do gašenje fluorescencije fluorofore iako je primećen i efekat unutrašnjeg filtera [240][241][242][243]. Međutim, za razliku od rezultata predstavljenih u ovom radu, u prisustvu nanočestica može doći i do obrnutog efekta tj.…”