Domain Fluorescence Research Articles

Wide-field fluorescence tomography with composited epi-illumination of multi-frequency sinusoidal patterns.

We present a spatial-frequency domain (SFD) fluorescence tomography (FT) for acquiring three-dimensional fluorophore distribution in turbid media. The approach uses a composited epi-illumination of multi-frequency sinusoidal patterns on a sample of semi-infinite geometry and demodulates the measured data with a generalized phase shifting scheme to calculate the modulation transfer function (MTF) at each frequency. This method results in a significantly reduced number of the optical field measurements, as compared to those with separate illumination of single-frequency sinusoidal patterns, and, thereby, achieves a fast data acquisition that is desired for a dynamic imaging application. Fluorescence yield images are recovered with the normalized Born formulated inversion of the diffusion model by simultaneously using the multi-frequency MTFs. Simulative and experimental reconstructions are performed in comparison with the single-frequency scheme to validate the proposed algorithm. The results suggest that adoption of the multi-frequency strategy to the SFD-FT can substantially improve the reconstruction quality, as well as its imaging resolution and quantitative accuracy.

Evaluation of Retinal Function and Morphology of the Pink-Eyed Royal College of Surgeons (RCS) Rat: A Comparative Study of in Vivo and in Vitro Methods

ABSTRACTPurpose: To characterize the course of retinal degeneration in the pink-eyed RCS rat in vivo and in vitro.Methods: Retinal function of RCS rats at the age of 2 to 100 weeks was determined in vivo using full-field electroretinography (ERG). Retinal morphology was evaluated in vivo using spectral domain Optical Coherence Tomography (sd-OCT) and Fluorescence angiography (FA) as well as postmortem using immunohistochemistry (IH). As a control, retinal function and morphology of non-dystrophic Wistar rats were analyzed.Results: RCS rats showed an extinction of the ERG beginning with the age of 4 weeks. In the OCT, the outer part of the retina (OPR) could be clearly distinguished from the inner part of the retina (IPR) until the age of 8 weeks. However, at this age, it was impossible to determine from OCT images whether the OPR was formed by the outer nuclear layer (ONL) or by cellular debris built in the course of retinal degeneration. In contrast, immunohistochemistry always enabled to differentiate between ONL and debris (RCS 4 weeks of age: OPR mainly formed by ONL; RCS 8 weeks of age: OPR consisted mainly of cell debris, only 1–2 cell rows of photoreceptor somata were left).Conclusions: In general, data obtained in vivo were confirmed by data obtained post mortem. Apart from the problem to differentiate between debris and ONL at the age of 8 weeks in the RCS rat, ERG and OCT are useful methods to evaluate retinal function and structure in vivo and to complement immunohistochemical analysis of the degeneration process.

New Fluorescence Domain "Excited Multimer" Formed upon Photoexcitation of Continuously Stacked Diaroylmethanatoboron Difluoride Molecules with Fused π-Orbitals in Crystals.

The crystal-packing structures of seven derivatives of diaroylmethanatoboron difluoride (1 a-gBF2 ) are characterized by no overlap of the π-conjugated main units of two adjacent molecules (type I), overlap of the benzene ring π-orbitals of two adjacent molecules (type II), and overlap of the benzene and dihydrodioxaborinine rings π-orbitals of adjacent molecules (type III). The crystal-packing structures govern the fluorescence (FL) properties in the crystalline states. The FL domain that is present in type I crystals, in which intermolecular orbital interactions are absent, leads to excited monomer-like FL properties. In the case of the type II crystals, the presence of intermolecular overlap of the benzene rings π-orbitals generates new FL domains, referred to as "excited multimers", which possess allowed S0 -S1 electronic transitions and, as a result, similar FL lifetimes at longer wavelengths than the FL of the type I crystals. Finally, intermolecular overlap of the benzene and dihydrodioxaborinine ring π-orbitals in the type III crystals leads to "excited multimer" domains with forbidden S0 -S1 electronic transitions and longer FL lifetimes at similar wavelengths as that in type I crystals.

Compact, non-invasive frequency domain lifetime differentiation of collagens and elastin

Changes in the composition of type I and type III collagen in tissue can shed light on various diseases. However, many of the current collagen detection techniques require invasive and destructive tissue sampling. In this study, a low cost, low complexity light emitting diode (LED) based system was developed to realize both non-invasive detection and specific discrimination of collagen and elastin variations in tissue based on fluorescence lifetimes. Modulated LED excitation was applied to frequency domain (FD) fluorescence lifetime spectroscopy to calculate tissue autofluorescence lifetimes. Using this method, fluorescence lifetimes from collagen type I versus type III were clearly separated at 3.95ns and 5.01ns, respectively, distinct from the elastin lifetime at 6.78ns. The probe was tested on bovine ocular tissues, with cornea showing much shorter average lifetime of 4.27ns than sclera at 7.48ns. Furthermore, measurements of an 8mm murine skin wound at 14 days post-wounding also showed distinct, longer average lifetimes at 9.74ns versus normal skin at 6.72ns. This FD tissue detection technique can potentially offer a way to examine tissue structures and discern the underlying pathology nondestructively.

White light emission from a single component system: remarkable concentration effects on the fluorescence of 1,3-diaroylmethanatoboron difluoride

Concentration effects on the fluorescence (FL) emission of 1,3-dibenzoylmethanatoboron difluoride (1aBF2) and its diisopropyl derivative (1bBF2) in KBr and CH2Cl2 were investigated. Powder samples of 1aBF2 and 1bBF2 in KBr exhibit yellow and white FL emissions, respectively, whose intensities and wavelengths are not significantly affected by concentration. In contrast, remarkable concentration effects on FL properties of these compounds in CH2Cl2 solutions were observed. Increases in the concentrations of 1aBF2 and 1bBF2 from 1×10−7 to ca. 2×10−1 M lead to dramatic changes in the FL colors from blue (398 and 411nm, respectively) to yellow (548 and 558nm) via white. Careful analysis of the FL spectra, involving lifetime determinations and wave deconvolutions, reveals that emissions from 1BF2 involve two FL domains, corresponding to an excited monomer and an excimer, and that concentration increases promote a continuous change from the former to the latter major FL domain. Thus, white FL of 1aBF2 and 1bBF2 is achieved by modulation of the dual FL of the excited monomer (blue) and excimer (yellow). These findings indicate that 1,3-diaroylmethanatoboron difluoride (1BF2) represents a new white emitting material that has advantageous features which arise from the fact that it is an easily prepared, low molecular weight, single component system not containing a heavy metal atom.