Reaction-Based Two-Photon Probes for Mercury Ions: Fluorescence Imaging with Dual Optical Windows

For fluorescent imaging of mercury ions in living species, two-photon probes with dual optical windows are in high demand but remain unexplored. Several dithioacetals were evaluated, and a probe was found, which, upon reaction with mercury species, yielded a two-photon dye; this conversion accompanies ratiometric emission changes with a 97-nm shift, enabling fluorescent imaging of both the probe and mercury ions in cells by one- and two-photon microscopy for the first time

Media 3: Dark-field polarization-sensitive optical coherence tomography

Originally published in Optics Express on 18 May 2015 (oe-23-10-12874

Media 1: Dark-field polarization-sensitive optical coherence tomography

Originally published in Optics Express on 18 May 2015 (oe-23-10-12874

Media 5: Dark-field polarization-sensitive optical coherence tomography

Originally published in Optics Express on 18 May 2015 (oe-23-10-12874

Media 2: Dark-field polarization-sensitive optical coherence tomography

Originally published in Optics Express on 18 May 2015 (oe-23-10-12874

Two-Photon Absorbing Dyes with Minimal Autofluorescence in Tissue Imaging: Application to <i>in Vivo</i> Imaging of Amyloid‑β Plaques with a Negligible Background Signal

Fluorescence imaging of tissues offer an essential means for studying biological systems. Autofluorescence becomes a serious issue in tissue imaging under excitation at UV–vis wavelengths where biological molecules compete with the fluorophore. To address this critical issue, a novel class of fluorophores that can be excited at ∼900 nm under two-photon excitation conditions and emits in the red wavelength region (≥600 nm) has been disclosed. The new π-extended dipolar dye system shows several advantageous features including minimal autofluorescence in tissue imaging and pronounced solvent-sensitive emission behavior, compared with a widely used two-photon absorbing dye, acedan. As an important application of the new dye system, one of the dyes was developed into a fluorescent probe for amyloid-β plaques, a key biomarker of Alzheimer’s disease. The probe enabled <i>in vivo</i> imaging of amyloid-β plaques in a disease-model mouse, with negligible background signal. The new dye system has great potential for the development of other types of two-photon fluorescent probes and tags for imaging of tissues with minimal autofluorescence

Synthesis and Characterization of Water-Soluble Conjugated Oligoelectrolytes for Near-Infrared Fluorescence Biological Imaging

Near-infrared (NIR) fluorophores attract increasing attention as a molecular marker (or probe) for in vivo and in vitro biological fluorescence imaging. Three types of new NIR fluorescent conjugated oligoelectrolytes (COEs: <b>Q-FlTBTTFl</b>, <b>Q-FlBBTFl</b>, and <b>Q-FlTBBTTFl</b>) are synthesized with quaternized ammonium ionic groups in their side-chains for water solubility. The emission wavelength is modulated in the range 600–1300 nm, by adjusting the intramolecular charge transfer in the molecular backbone based on the electron-rich fluorene (and/or thiophene) and electron-deficient benzo­[2,1,3]­thiadiazole (or benzo­[1,2-<i>c</i>:4,5-<i>c′</i>]­bis­[1,2,5]­thiadiazole) moieties. The COEs show a remarkably larger Stokes shift (147–276 nm) compared to commercial rhodamine and cyanine dyes in water, avoiding self-quenching and interference from the excitation backscattered light. The photoluminescence (PL) quantum efficiency is improved substantially by up to 27.8% in water by fabricating a vesicular complex, COE/v, with a block ionomer, poly­[(ethylene oxide)-<i>block</i>-(sodium 2-acrylamido-2-methyl-1-propanesulfonate)]. In vitro cellular uptake images with the COEs are obtained with good biocompatibility by confocal single-photon and two-photon microscopy. The ex vivo and in vivo images of a mouse xenograft model treated with the <b>Q-FlBBTFl</b>/v exhibit a substantially stronger fluorescence signal at the tumor site than at the other organs, highlighting the potential of the COE/v as an NIR fluorescent imaging agent for the diagnosis of cancer

Media 2: Gradient index lens based combined two-photon microscopy and optical coherence tomography

Originally published in Optics Express on 02 June 2014 (oe-22-11-12962