Detection of low quantum yield fluorophores using metallic nanoparticles: improved imaging time and spatial resolution

PEDRO F. ARAMENDÍA

Córdoba

Conferencia; Plasmones 2011; 2011

AAIFQ

We present experiments with gold nanoparticles interacting with dyes in solution and with fluorescently labeled actin filaments within cells. These experiments show an enhanced contrast for weakly fluorescent molecules in the vicinity of the nanoparticles and longer imaging times for fluorophores associated to actin filaments near a nanoparticle. The results are rationalized by a careful review of the parameters that modify the emission of fluorescent molecules in the vicinity of a gold nanoparticle. Nanoparticle-fluorophore separation, intrinsic molecule quantum yield (f0), and molecule absorption and emission spectra were analyzed with the purpose of finding the optimum conditions to design new probes based on fluorophores coupled to metallic nanoparticles. We show that the maximum gain in brightness of the metallic nanoparticle-fluorophore hybrid system with respect to the isolated molecule increases almost inversely proportional to f0, while the width at half maximum of the enhanced region is reduced, reaching a spatial resolution of 10 nm for f0 = 0.01. Using the field enhancement of AuNP, fluorescence fluctuation experiments can be performed with weakly fluorescent dyes at the micromolar concentration range in a volume of 10-4 fL. Our results point to the promising possibility of detecting intrinsic fluorescence of biomolecules and illustrate a way to obtain longer tracking times and to track molecules in the vicinity of a metallic nanoparticle after background photobleaching.