Multiphoton fluorescence lifetime imaging microscopy reveals free-to-bound NADH ratio changes associated with metabolic inhibition.

Measurement of endogenous free and bound NAD(P)H relative concentrations in living cells isa useful method for monitoring aspects of cellular metabolism, because the NADH∕NAD⁺ reduction-oxidation pair is crucial for electron transfer through the mitochondrial electron transport chain. Variations of free and bound NAD(P)H ratio are also implicated in cellular bioenergetic and biosynthetic metabolic changes accompanying cancer. This study uses two-photon fluorescence lifetime imaging microscopy (FLIM) to investigate metabolic changes in MCF10A premalignant breast cancer cells treated with a range of glycolysis inhibitors: namely, 2 deoxy-D-glucose, oxythiamine, lonidamine, and 4-(chloromethyl) benzoyl chloride, as well as the mitochondrial membrane uncoupling agent carbonyl cyanide m-chlorophenylhydrazone.

Dense two-dimensional silver single and double nanoparticle arrays with plasmonic response in wide spectral range.

We report the properties of plasmons in dense planar arrays of silver single and double nanostructures with various geometries fabricated by electron beam lithography (EBL) as a function of their size and spacing. We demonstrate a strong plasmon coupling mechanism due to near-field dipolar interactions between adjacent nanostructures, which produces a major red shift of the localized surface plasmon resonance (LSPR) in silver nanoparticles and leads to strong maximum electric field enhancements in a broad spectral range. The extinction spectra and maximum electric field enhancements are theoretically modeled by using the finite element method.

Europium chelate (BHHCT-Eu3+) and its metal nanostructure enhanced luminescence applied to bioassays and time-gated bioimaging.

We report the use of europium chelate, 4,4'-bis(1'',1'',1'',2'',2'',3'',3''-heptafluoro-4'',6''-hexanedion-6''-yl)chlorosulfo-o-terphenyl-Eu(3+) (BHHCT-Eu(3+)), in silver nanostructure-enhanced luminescence and its application to bioassays and bioimaging. The highest luminescence intensity enhancement factor of BHHCT-Eu(3+) achieved in this study was about 11 times, while the simultaneously measured luminescence lifetime was reduced 2-fold. The luminophore photostability was also improved by a factor of 3.

Enhanced flow cytometry-based bead immunoassays using metal nanostructures.

While the principle of fluorescence enhancement of metal nanostructures is well-known, the utility of this effect in practical methodologies used in analytical laboratories remains to be established. In this work, we explore the advantage of fluorescence enhancement for flow cytometry. We report the observation of metal-enhanced fluorescence emission of fluorophores located on the surface of silica beads coated with nanostructured silver, suitable for flow cytometry detection.

Fluorescence amplification by electrochemically deposited silver nanowires with fractal architecture.

Electrochemically deposited silver structures with nanowires 50-100 nm in diameter show high fluorescence amplification and strongly reduced fluorescence lifetimes. Both quantities depend on the structure thickness. With increasing thickness the fluorescence amplification proportionally increases and the fluorescence lifetime decreases.

Optical characterization of eu-doped and undoped gd(2)o(3) nanoparticles synthesized by the hydrogen flame pyrolysis method.

Rare-earth-doped nanoparticles are promising materials for fluorescent labeling, as they are characterized by a high Stokes shift, narrow emission spectra, long lifetimes, minimized photobleaching, and low toxicity. We examined the structural and optical properties of europium-doped gadolinium oxide nanoparticles synthesized by the flame pyrolysis method, with specific emphasis on full spectral characterization and fluorescence kinetics. The emission-excitation characterization revealed the presence of predominantly monoclinic but also highly luminescent cubic phases with a prominent oxygen-to-europium charge-transfer band in the 230-260 nm range.