Transplantation of stem cells, such as mesenchymal stem cells (MSCs), is a promising strategy for treating several types of intractable disorders. Mechanistically, it could not only replace damaged cells by direct contribution, but also establish an anti-inflammatory or immunomodulatory microenvironment. However, the cellular mechanisms underlying molecular and biological properties of stem cells during ex vivo expansion and also after transplantation in pathological environments remain largely elusive. We recently developed the cyanoacrylamide-based coumarin derivatives (Fluorescent real-time thiol tracer; FreSHtracer*) reversibly react with glutathione for monitoring of glutathione levels in living stem cells. These probes revealed that glutathione levels are heterogeneous among subcellular organelles and among individual cells and show dynamic changes and heterogeneity in repopulating stem cells depending on oxidative-stress or culture conditions. Importantly, a subpopulation of stem cells with high-glutathione levels exhibited increased self-renewal and migration activities in vitro and showed improved therapeutic efficiency in treating asthma. Furthermore, employing a novel combination of longitudinal intravital confocal fluorescence imaging and microcystoscopy in living animals, we investigated the distributions and properties of transplanted multipotent MSCs derived from human embryonic stem cells at single-cell resolution in real-time by performing confocal imaging of bladder tissues in a rat model of IC/BPS for up to 6 months post-transplantation. These novel real-time monitoring strategies demonstrate the novel molecular insight for maintaining stem cell functions and also enhance understanding of the in vivo behaviors of the engrafted stem cells, which is crucial to determine the efficacy and safety of stem cell-based therapies. This strategy may facilitate the translation of various stem cell-based approaches into clinical practice.

The effects of molecular structure on the redox properties of the organic electroluminescent materials (Ir(ppy)3 Ir(m-ppy)3 Ir(p-toly)3) were studied using cyclic voltammetry and spectroscopy. These iridium complexes show reversible oxidation and reduction on the electrode, which produce the symmetric cyclic voltammogram. It indicates that these materials are very stable under repetitive oxidation/reduction cycles. The electrochemically determined ionization potentia/electron affinity values are 5.4OeV/3.02eV for Ir(ppy)3, 5.36eV/2.96eV for Ir(m-ppy)3, and 5.35eV/2.97eV for Ir(p-toly)3 from the SCE(Standard Calomel Electrode). The electrically determined band gaps are 2.38eV (521nm), Ir(ppy)3, 2.4OeV (517nm), Ir(m-ppy)3, and 2.38eV (521nm). Ir(p-toly)3, which are similar with the optical band gaps. The position of methyl group on 2-phenylpyridine (ppy) effects do not influence much on the ionization potential, electron affinity, and band gap of Ir(ppy)3 derivatives.

The color stability and purity from OLED is of current interest. Aggregation of dyes alters the device color after fabrication of the devices. Exciplex and electroplex formations have been proposed to explain the aggregate color change. We investigate the possibility of exciplex formation and propose the new electroplex state that can cause the bathochromic shift of the electroluminescence spectrum from the devices with TPD/PBD layers. The photoluminescence maximum of the device was 420nm, and the electroluminescence maximum of the device to became 480nm. The bathochromic shift cannot be attained with photoluminescence study with highly concentrated TPD/PBD mixture. This clearly indicates that the 480nm spectrum of the devices is not resulted from the exciplex formation with TPD and PBD. We observed the overshoot in EL spectrum from the OLEDs. The most intense overshoot was observed at 460nm, which may be due to the aggregates that are formed after the electric field has been removed from the devices.