Mingzhu Zhang

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.

A series of two-photon absorption pyridinium sulfonate inner salts targeting endoplasmic reticulum (ER), inducing cellular stress and mitochondria-mediated apoptosis in cancer cells

In this study, a two-photon active DiphenthioER1 was screened from the four pyridinium sulfonate salt derivatives (TriphenER1-2 and DiphenthioER1-2) for imaging endoplasmic reticulum (ER) and tracking the dynamics of the ER morphology. The photophysical properties of TriphenER1-2 and DiphenthioER1-2 were systemically investigated both experimentally and theoretically, revealing that they possess large Stokes shifts, and large two-photon absorption cross-sections from 163 GM to 2023 GM in the near infrared region using a Z-scan method by avoiding spontaneous fluorescence, deep tissue penetration, and low cell damage in living cells. Among them, the DiphenthioER1 compound was found to exhibit the highest cellular uptake ability and two-photon fluorescence signals using confocal microscopy. DiphenthioER1 successfully targeted the ER and induced ER-stress, subsequently nuclear misshaping and mitochondria-mediated apoptosis have been displayed. This study thus provides great insights into designing novel two-photon fluorescent materials with dual functionality and offers tools to understand the ER-stress related mechanism for cell and chemical biologists.

An Organometallic Ir(III) Molecular Probe for Imaging Microtubules in Fluorescence and Electron Microscopy

We report a versatile cyclometalated Iridium (III) complex probe that achieves synchronous fluorescence-electron microscopy correlation to reveal microtubule ultrastructure in cells. The selective insertion of probe between repeated α and β units of microtubule triggers remarkable fluorescent enhancement, and high TEM contrast due to the presence of heavy Ir ions. The highly photostable probe allows live cell imaging of tubulin localization and motion during cell division with an resolution of 20 nm, and under TEM imaging reveals the αβ unit interspace of 45Å of microtubule in cells.Microtubules are a critical component of the cell cytoskeleton and an important actor in cell mitosis and adhesion. Yet their imaging has been limited by the lack of effective probes. Fluorescent imaging can be performed using either taxol derivates, immunoglobins, or genetically encoded fluorescent proteins. These approaches however tend to hinder microtubulin functionality and they do not bestow any contrast in electron microscopy. Here we present a cyclometalated Iridium(III) complex that bind to microtubulin and allow both fluorescent and electron microscopy imaging. The complex displays a light switch phenomena coupled with strong luminescence intensity upon tubulin protein binding without interfering into cell proliferation. Furthermore, the application of super resolution imaging of microtubule ultrastructure within brain neuron network under stimulated emission depletion (STED) microscopy was successfully demonstrated. More importantly, the Ir-Tub showed its capability to display microtubule structure under protein monomeric level by means of energy-filtered transmission electron microscopy (EF-TEM). This innovative complex sheds light on the visualization and modeling of precise microtubule structure, aiding a much better understanding of correlated cellular mechanisms and ultimately associated diseases.

Real-time noninvasive monitoring of cell mortality using a two-photon emissive probe based on quaternary ammonium

We report that a dicyanyl derivative QN2 containing quaternary ammonium was capable of identifying apoptotic cells by targeting nucleic acid (DNA and RNA) and we were able to observe nuclear ultra-details using a stimulated emission depletion (STED) nanoscopy technique. QN2 could evaluate the anti-cancer drug pesticide effect by monitoring in real-time without interfering with normal cell proliferation. These results suggest the high potential for using QN2 in practice for monitoring apoptosis to evaluate tumor therapy effectiveness or for drug development.

A Series of Zn(II) Terpyridine-Based Nitrate Complexes as Two-Photon Fluorescent Probe for Identifying Apoptotic and Living Cells via Subcellular Immigration

Two-photon active probe to label apoptotic cells plays a significant role in biological systems. However, discrimination of live/apoptotic cells at subcellular level under microscopy remains unachieved. Here, three novel Zn(II) terpyridine-based nitrate complexes (C1-C3) containing different pull/push units were designed. The structures of the ligands and their corresponding Zn(II) complexes were confirmed by single-crystal X-ray diffraction analysis. On the basis of the comprehensive comparison, C3 had a suitable two-photon absorption cross section in the near-infrared wavelength and good biocompatibility. Under two-photon confocal microscopy and transmission electron microscopy, it is found that C3 could target mitochondria in living cells but immigrate into the nucleolus during the apoptotic process. This dual-functional probe (C3) not only offers a valuable image tool but also acts as an indicator for cell mortality at subcellular level in a real-time manner.

A novel flurophore-cyano-carboxylic-Ag microhybrid: Enhanced two photon absorption for two-photon photothermal therapy of HeLa cancer cells by targeting mitochondria

In this study, a novel two-photon photothermal therapy (TP-PTT) agent based on an organic-metal microhybrid with surface Plasmon resonance (SPR) enhanced two-photon absorption (TPA) characteristic was designed and synthesized using a fluorescent cyano-carboxylic derivative 2-cyano-3-(9-ethyl-9H-carbazol-3-yl) -acrylic acid (abbreviated as CECZA) and silver nanoparticles through self-assembly process induced by the interfacial coordination interactions between the O/N atom of CECZA and Ag+ion at the surface of Ag nanoparticles. The coordination interactions caused electron transfer from the Ag nanoparticles to CECZA molecules at the excited state, resulting in a decreased fluorescence quantum yield. The interfacial coordination interactions also enhanced the nonlinear optical properties, including 13 times increase in the TPA cross-section (δ). The decreased fluorescence quantum yield and increased two photon absorption caused by the SPR effect led excellent two-photon photothermal conversion, which was beneficial for the TP-PTT effect on HeLa cancer cells.

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