Yingzhong Zhu

Highly Hydrophilic, Two-photon Fluorescent Terpyridine Derivatives Containing Quaternary Ammonium for Specific Recognizing Ribosome RNA in Living Cells

A two-photon fluorescent probe (J1) that selectively stains intracellular nucleolar RNA was screened from three water-soluble terpyridine derivatives (J1-J3) with quaternary ammonium groups. The photophysical properties of J1-J3 were systemically investigated both experimentally and theoretically, revealing that J1-J3 possess large Stokes shifts and the two-photon absorption action cross sections range from 38 to 97 GM in the near-infrared region. This indicates that J1 could specifically stain nucleoli by targeting the nucleolar rRNA from the recognition experiments in vitro, the two-photon imaging experiments, and the stimulated emission depletion in vivo. The mechanism of action in which J1 binds to the nucleolar rRNA was researched via both experiments and molecular modeling. The high binding selectivity of J1 to nucleolar RNA over cytosolic RNA made this probe a potential candidate to visualize rRNA probe in the living cells.

Formation and nonlinear optical properties of Ag nanocrystals capped with the conjugated ligand carbazolyl styryl terpyridine

The third-order nonlinear materials have been the focus of present research. It is known that the χ(3) value of the organic optical material is generally small, and hardly displays any evident third order nonlinear effect. However, the χ(3) value was significantly improved when the organic ligands were combined with nano-Ag due to the increase of surface plasmon resonance. The nano-Ag changes its local electric field, and in turn causes a regional interaction between the ligand and the metal clusters. In this article, a new optical carbazole derivative (E)-2-(4-([2,2′:6′,2′′-terpyridine]-4′-yl)styryl)-9-hexyl-9H-carbazole, abbreviated as L, has been designed and synthesized. The ligands were combined with nano-Ag, acting on the surface and stabilizing the system without any extra control such as surfactant and pH, which may be explained by the theory of hard and soft acid–base. Careful characterizations have been performed by UV-vis absorption spectroscopy, 1H NMR spectroscopy, FT-IR, XRD and TEM. Particular properties have been shown by fluorescence spectra, fluorescence lifetime, Raman spectrum, non-linear optical response and cyclic voltammetry curve. The results indicate that the nano-composite L–Ag NCs have a stronger Raman enhancement effect, shorter fluorescence lifetime and larger two-photon absorption (TPA) when compared to the free ligand L. The data for the TPA cross-section value (σ = 1336.85 GM), nonlinear refractive index (γ = 2.23 × 10−13 cm2 W−1) and third order nonlinear optical susceptibility (Re(χ(3)) = 1.16 × 10−11 esu) are measured and discussed.

Thiophene-based pyridine derivatives: synthesis, crystal structures, two-photon absorption properties and bio-imaging applications in the near-IR region

Two novel D–π–A structural thiophene-based pyridine (N^N^N or N^N^C) chromophores have been designed and synthesized. Then they were characterized by 1H NMR, 13C NMR, IR, MALDI-TOF-MS and single crystal X-ray diffraction analyses. Photophysical properties including UV-vis absorption, fluorescence, and two-photon absorption (2PA) spectra were systematically investigated using both theoretical and experimental methods. The results indicated that the thiophene-based chromophores displayed high fluorescence quantum yields and large active 2PA cross-sections in the near infrared region. Due to their excellent 2PA properties, low toxicity and low molecular weight, two-photon fluorescence microscopy (2PFM) images of HepG2 cells were captured, which suggested their potential applications in biological studies.

A water-soluble two-photon fluorescence chemosensor for ratiometric imaging of mitochondrial viscosity in living cells

A convenient and rationally designed water-soluble two-photon excited fluorescence (TPEF) sensor for monitoring viscosity with specific targeting at the subcellular level remains a challenge. Herein, we reported a novel water-soluble ratiometric TPEF chemosensor EIN that is specifically responsive and singularly sensitive to mitochondria viscosity in living cells. Because its fluorescence emission bands at two different wavelengths show obvious enhancement with increased solvent viscosity, we found that the fluorescence intensity ratio (I569/I384) versus the logarithm of the viscosity (log η) enables monitoring and quantifying of abnormal changes of mitochondria viscosity. More importantly, EIN was successfully utilized to distinguish the normal and nystatin treated HepG2 cell viscosity difference of mitochondria. In a word, the merits of the NIR property, high selectivity and signal ratio provide a more convenient means for studying biological processes and mitochondria viscosity related diseases.

A Series of Imidazole Derivatives: Synthesis, Two-Photon Absorption, and Application for Bioimaging

A new series of D-π-A type imidazole derivatives have been synthesized and characterized. Two corresponding imidazolium salts (iodine and hexafluorophosphate) were prepared from the imidazole compound. Their electron-withdrawing ability can be largely tunable by salt formation reaction or ion exchange. UV-vis absorption and single-photon fluorescence spectra have been systematically investigated in different solvents. The two-photon cross sections (δ 2PA) of the imidazole derivatives are measured by two-photon excited fluorescence (2PEF) method. Compared with those of T-1 (107 GM) and T-3 (96 GM), T-2 (imidazolium iodine salt) has a large two-photon absorption (2PA) cross section value of 276 GM. Furthermore, the cytotoxicity and applications in bioimaging for the imidazole derivatives were carried out. The results showed that T-1 can be used as a lysosomal tracker with high stability and water solubility within pHs of 4–6, while T-2 and T-3 can be used as probes for cell cytoplasm.

Two novel bipyrazole derivative ligands: Synthesis, crystal structure, theoretical studies, and sensitive response toward Fe3+

Two novel bipyrazole derivative ligands L1 (4-(di(1H-pyrazol-1-yl)methyl)-N,N-diphenylaniline) and L2 (4-(di(1H-pyrazol-1-yl)methyl)-N,N-bis(4-ethoxy phenyl)aniline), were synthesized, and fully characterized. The crystal structures of the two ligands were confirmed by single-crystal X-ray diffraction analysis. The structural analysis revealed that two pyrazole units are attached to the same carbon atom connected with triphenylamine moiety. The UV-vis absorption and fluorescence spectral properties of the ligands were investigated and explained relying on theoretical calculation. Significantly, it was found that the ligands display an exclusively selective and sensitive response toward Fe(3+) with aid of UV-vis absorption spectroscopic methods.

Synthesis, crystal structures, one/two-photon optical properties and bioimaging application of two organic molecules with D–A and D–π–A models containing 6-phenyl-2,2′-bipyridine

Two novel organic compounds with D–A (L1) and D–π–A (L2) models containing 4-(N,N-dipropylamino)phenyl [donor group (D)] and 6-phenyl-2,2′-bipyridine [acceptor (A)] groups were synthesized and characterized by IR, 1H NMR, 13C NMR, MS and single crystal X-ray diffraction. Their photophysical properties were systematically investigated using both experiments and theoretic calculations. It was found that the two-photon action cross-section (δΦ) of the D–π–A model molecule (δΦL2 = 119 GM) was approximately three times larger than that of the D–A type molecule (δΦL1 = 43 GM). Furthermore, their cytotoxicity and applications in bioimaging were determined. The results showed that L1 and L2 could be used as cytoplasmic dyes with high stability and low cytotoxicity.

Double labelling of intracellular mitochondria and nucleolus using thiophene pyridium salt with high quantum yield as biosensor and its application in stimulated emission depletion nanoscopy

Probe for dual-site target distinct subcellular compartments from cytosol and nucleus is an attractive approach, however, which was scarcely reported. Herein, a series of small-molecular thiophene pyridium salt derivatives (MitoNuc1-4) possessing water-soluble, high quantum yield and two-photon activity were rationally designed, and their structures were crystallographic confirmed. Systematic photophysical and biological imaging property investigations were carried out for them. It was found that MitoNuc1-4 exhibit two-photon absorption properties in the near infrared region, and MitoNuc1 has membrane permeability and cationic nature, rendering it to be double labelling of mitochondria and nucleolus in living cells with superb photo-stability and non-invasiveness. It also demonstrated that MitoNuc1 in living cells can monitor mitochondrial division in real time and revealed nucleolar ultrastructure under stimulated emission depletion nanoscopy.

CCDC 1500293: Experimental Crystal Structure Determination

Related Article: Wei Du, Hui Wang, Yingzhong Zhu, Xiaohe Tian, Mingzhu Zhang, Qiong Zhang, Senio Campos De Souza, Aidong Wang, Hongping Zhou, Zhongping Zhang, Jieying Wu, and Yupeng Tian|2017|ACS Applied Materials and Interfaces|9|31424|doi:10.1021/acsami.7b08068

CCDC 1500294: Experimental Crystal Structure Determination

Related Article: Wei Du, Hui Wang, Yingzhong Zhu, Xiaohe Tian, Mingzhu Zhang, Qiong Zhang, Senio Campos De Souza, Aidong Wang, Hongping Zhou, Zhongping Zhang, Jieying Wu, and Yupeng Tian|2017|ACS Applied Materials and Interfaces|9|31424|doi:10.1021/acsami.7b08068