A Fluorescent Probe for Neural Stem/Progenitor Cells with High Differentiation Capability into Neurons.

Selection of a specific neural stem/progenitor cells (NSPCs) has attracted broad attention in regenerative medicine for neurological disorders. Here, we report a fluorescent probe, CDg13, and its application for isolating strong neurogenic NSPCs. In comparison to the NSPCs isolated by other biomarkers, CDg13-stained NSPCs showed higher capability to differentiate into neurons. Target identification revealed that the fluorescence intensity of the probe within cells is inversely proportional to the expression levels of mouse and human Abcg2 transporters. These findings suggest that low Abcg2 expression is a biomarker for neurogenic NSPCs in mouse brain. Furthermore, CDg13 can be used to isolate Abcg2low cells from heterogeneous cell populations.

Synthesis and characterization of reversible chemosensory polymers: modulation of sensitivity through the attachment of novel imidazole pendants.

Three novel electron donor-acceptor conjugated polymers (P1-P3) bearing various imidazole pendants have been synthesized. Their excellent photophysical and electrochemical properties make them suitable transduction materials for chemosensing applications. Indeed, polymers P1-P3 have been found to show remarkable sensing capabilities towards H(+) and Fe(2+) in semi-aqueous solutions. Upon titration with H(+), polymers P1 and P2 showed hypsochromic shifts of their absorptions and photoluminescence (PL) maxima with enhanced fluorescence intensities. However, P3 showed diminished absorption and fluorescence intensities under similar conditions due to static quenching. The anomalous behavior of P3 compared with P1 and P2 has been clarified in terms of electronic distributions through computational analysis. Furthermore, P3 (K(SV) = 1.03×10(7)) showed a superior sensing ability towards Fe(2+) compared with P1 (K(SV) = 2.01×10(6)) and P2 (K(SV) = 4.12×10(6)) due to its improved molecular wire effect. Correspondingly, the fluorescence lifetime of P3 was greatly decreased (almost 11-fold) compared to those of polymers P1 (4.6-fold) and P2 (6.2-fold) in the presence of Fe(2+). By means of a fluorescence on-off-on approach, chemosensing reversibilities in protonation-deprotonation and metallation-demetallation have been achieved by employing triethylamine (TEA) and the disodium salt of ethylenediaminetetraacetic acid (Na(2)-EDTA)/phenanthroline, respectively, as suitable counter ligands. (1)H NMR titrations have revealed the unique behavior of P3 compared with P1 and P2. To the best of our knowledge, there have been no previous reports of Fe(2+) sensors based on single imidazole receptors conjugated to a main-chain polymer showing such a diverse sensitivity pattern depending on their attached substituents.

Synthesis of main-chain metallo-copolymers containing donor and acceptor bis-terpyridyl ligands for photovoltaic applications.

Two random (Zn(II)-based P1-P2) and two alternating (Ru(II)-based P3-P4) metallo-copolymers containing bis-terpyridyl ligands with various central donor (i.e., fluorene or carbazole) and acceptor (i.e., benzothiadiazole) moieties were synthesized. The effects of electron donor-acceptor interactions with metal (Zn(II) and Ru(II)) ions on their thermal, optical, and electrochemical properties were investigated. Because of the strong ICT transitions between donor and acceptor ligands in both Zn(II)- and Ru(II)-based metallo-coplymers and MLCT transitions in Ru(II)-based metallo-coplymers, the absorption spectra covered a broad range of 260-750 nm with the band gaps of 1.57-1.77 eV. In addition, the introduction of Ru(II)-based metallo-coplymer P4 mixed with PC(60)BM as an active layer of the BHJ solar cell device exhibited the highest PCE value up to 0.90%.

Development of background-free tame fluorescent probes for intracellular live cell imaging.

Fluorescence labelling of an intracellular biomolecule in native living cells is a powerful strategy to achieve in-depth understanding of the biomolecule's roles and functions. Besides being nontoxic and specific, desirable labelling probes should be highly cell permeable without nonspecific interactions with other cellular components to warrant high signal-to-noise ratio. While it is critical, rational design for such probes is tricky. Here we report the first predictive model for cell permeable background-free probe development through optimized lipophilicity, water solubility and charged van der Waals surface area. The model was developed by utilizing high-throughput screening in combination with cheminformatics. We demonstrate its reliability by developing CO-1 and AzG-1, a cyclooctyne- and azide-containing BODIPY probe, respectively, which specifically label intracellular target organelles and engineered proteins with minimum background. The results provide an efficient strategy for development of background-free probes, referred to as 'tame' probes, and novel tools for live cell intracellular imaging.

Novel thieno-imidazole based probe for colorimetric detection of Hg2+ and fluorescence turn-on response of Zn2+.

Novel thieno-imidazole based polymer P showed both colorimetric and ratiometric detections of Hg(2+) as well as fluorometric detection of Zn(2+) via fluorescence turn-on response with augmented lifetime. Its model polymer M did not show any such sensing capability under similar conditions, which further confirmed the unique sensitivity of P toward Hg(2+) and Zn(2+) via the chelation of metal ions to both "S" and "N" heteroatoms.

Novel dithieno-benzo-imidazole-based Pb2+ sensors: substituent effects on sensitivity and reversibility.

Two novel dithieno-benzo-imidazole-based compounds (M2 and A2) showed remarkable sensitivities towards Pb(2+) by 12-fold enhancement and 10-fold decay of fluorescence, respectively, in aqueous solutions. Substituent effects of different dithieno-benzo-imidazole-based moieties (M1, M2, A1 and A2) on the quantum yields, fluorescence lifetimes and sensitivities to Pb(2+) along with the reversibilities by S(2-) were investigated.