Avoiding diffusion limitations in cobalt(III/II)-tris(2,2'-bipyridine)-based dye-sensitized solar cells by tuning the mesoporous TiO2 film properties

Dye-sensitized solar cells based on electrolytes containing cobalt complexes as redox shuttles typically suffer a major limitation in terms of slow diffusion of those couples through the mesoporous TiO(2) film. This results in a drop of the photocurrent density, particularly at high incident light intensities, reducing the overall cell performance. This work illustrates how tuning the four characteristic parameters of the mesoporous TiO(2) layer, namely film thickness, particle size, pore size and porosity, by simply optimizing the TiCl(4) post-treatment, completely eliminates diffusion problems of cobalt(III/II) tris(2,2'-bipyridine) and at the same time maximizes the short-circuit photocurrent density. As a result, a power conversion efficiency of 10.0% at AM 1.5 G 100 mW cm(-2) was reached in conjunction with an organic sensitizer.

Porphyrin-sensitized solar cells with cobalt (II/III)-based redox electrolyte exceed 12 percent efficiency

The iodide/triiodide redox shuttle has limited the efficiencies accessible in dye-sensitized solar cells. Here, we report mesoscopic solar cells that incorporate a Co((II/III))tris(bipyridyl)-based redox electrolyte in conjunction with a custom synthesized donor-π-bridge-acceptor zinc porphyrin dye as sensitizer (designated YD2-o-C8). The specific molecular design of YD2-o-C8 greatly retards the rate of interfacial back electron transfer from the conduction band of the nanocrystalline titanium dioxide film to the oxidized cobalt mediator, which enables attainment of strikingly high photovoltages approaching 1 volt. Because the YD2-o-C8 porphyrin harvests sunlight across the visible spectrum, large photocurrents are generated. Cosensitization of YD2-o-C8 with another organic dye further enhances the performance of the device, leading to a measured power conversion efficiency of 12.3% under simulated air mass 1.5 global sunlight.

A cobalt complex redox shuttle for dye-sensitized solar cells with high open-circuit potentials

Dye-sensitized solar cells are a promising alternative to traditional inorganic semiconductor-based solar cells. Here we report an open-circuit voltage of over 1,000 mV in mesoscopic dye-sensitized solar cells incorporating a molecularly engineered cobalt complex as redox mediator. Cobalt complexes have negligible absorption in the visible region of the solar spectrum, and their redox properties can be tuned in a controlled fashion by selecting suitable donor/acceptor substituents on the ligand. This approach offers an attractive alternate to the traditional I₃⁻/I⁻ redox shuttle used in dye-sensitized solar cells. A cobalt complex using tridendate ligands [Co(bpy-pz)₂]^3+/2+(PF₆)_3/2 as redox mediator in combination with a cyclopentadithiophene-bridged donor-acceptor dye (Y123), adsorbed on TiO₂, yielded a power conversion efficiency of over 10% at 100 mW cm⁻². This result indicates that the molecularly engineered cobalt redox shuttle is a legitimate alternative to the commonly used I₃⁻/I⁻ redox shuttle.

Dye-sensitized solar cells are a promising alternative to traditional inorganic semiconductor-based solar cells. Yum et al. use a molecularly engineered cobalt complex as a redox mediator to achieve an open-circuit voltage of over 1,000 mV in a mesoscopic dye-sensitized solar cell.

Tris(2-(1H-pyrazol-1-yl)pyridine)cobalt(III) as p-type dopant for organic semiconductors and its application in highly efficient solid-state dye-sensitized solar cells

Chemical doping is an important strategy to alter the charge-transport properties of both molecular and polymeric organic semiconductors that find widespread application in organic electronic devices. We report on the use of a new class of Co(III) complexes as p-type dopants for triarylamine-based hole conductors such as spiro-MeOTAD and their application in solid-state dye-sensitized solar cells (ssDSCs). We show that the proposed compounds fulfill the requirements for this application and that the discussed strategy is promising for tuning the conductivity of spiro-MeOTAD in ssDSCs, without having to rely on the commonly employed photo-doping. By using a recently developed high molar extinction coefficient organic D-π-A sensitizer and p-doped spiro-MeOTAD as hole conductor, we achieved a record power conversion efficiency of 7.2%, measured under standard solar conditions (AM1.5G, 100 mW cm(-2)). We expect these promising new dopants to find widespread applications in organic electronics in general and photovoltaics in particular.

Antitumor effect of sFlt-1 gene therapy system mediated by Bifidobacterium Infantis on Lewis lung cancer in mice

Soluble fms-like tyrosine kinase receptor (sFlt-1) is a soluble form of extramembrane part of vascular endothelial growth factor receptor-1 (VEGFR-1) that has antitumor effects. Bifidobacterium Infantis is a kind of non-pathogenic and anaerobic bacteria that may have specific targeting property of hypoxic environment inside of solid tumors. The aim of this study was to construct Bifidobacterium Infantis-mediated sFlt-1 gene transferring system and investigate its antitumor effect on Lewis lung cancer (LLC) in mice. Our results demonstrated that the Bifidobacterium Infantis-mediated sFlt-1 gene transferring system was constructed successfully and the system could express sFlt-1 at the levels of gene and protein. This system could not only significantly inhibit growth of human umbilical vein endothelial cells induced by VEGF in vitro, but also inhibit the tumor growth and prolong survival time of LLC C57BL/6 mice safely. These data suggest that Bifidobacterium Infantis-mediated sFlt-1 gene transferring system presents a promising therapeutic approach for the treatment of cancer.

Synthesis, structures, redox and photophysical properties of benzodifuran-functionalised pyrene and anthracene fluorophores

Benzodifuran-functionalised pyrene and anthracene fluorophores 1 and 2 were obtained in reasonable yields. Their single crystal structures, electrochemical, optical absorption, and fluorescence characteristics have been described. They show strong luminescence with high quantum yields of 0.53 for 1 and 0.48 for 2.

Gemcitabine and capecitabine as third-line treatment in patients with metastatic colorectal cancer after failure of irinotecan and oxaliplatin

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Background: There is no standard chemotherapeutic regimen for patients with advanced colorectal cancer (CRC) progressing after combination regimens including irinotecan and oxaliplatin and having good performance status. 5-FU and gemcitabine are synergistic in preclinical studies of colon cancer cells. And gemcitabine also increases intracellular release of 5-FU from capecitabine. The aim of this study is to evaluate the efficacy and tolerance of the gemcitabine/capecitabine combination as third-line treatment for patients with advanced colorectal cancer.

Methods: Between May 2007 and September 2009, the data on 12 patients with metastatic colorectal cancer after failure of irinotecan- and oxaliplatin-containing regimens reviewed retrospectively. The median patient age was 54.0 years (range 37-77). The ECOG performance status was 0, 1 or 2. All patients has 2 or more previous chemotherapy. Patients received GemCap regimen (oral capecitabine 1,000 mg/m2 twice daily on days 1 to 14 plus Gem 1,000 mg/m2 on days 1 and 8 every 3 weeks). Eleven patients were evaluable for the response and all patients were evaluable for toxicity.

Results: No partial response was achieved and disease stabilization in 4 (36.4.3%) cases. Median progression-free survival and median overall survival were 9.1 weeks (range 3.0-18.0) and 22.3 weeks (range 10.5- 53.0). Four patients with disease stabilization had longer median progression-free survival than those with disease progression (13 weeks vs. 6.2 weeks). No toxic deaths occurred. Grade 3 toxicities were thrombocytopenia (in 2 patients), neutropenia (in 2 patients) and mucositis (in 1 patient), hand-foot syndrome (in 1 patient) and GI toxicity (in 2 patients).

Conclusions: The combination of gemcitabine and capecitabine was found to be a safe palliative regimen for heavily pretreated patients with metastatic CRC. Despite no patients had radiologic response, patients with disease stabilization achieved better progression-free survival. This regimen seems to be potentially effective regimen in the treatment of CRC.

No significant financial relationships to disclose.

Versatile strategy to access fully functionalized benzodifurans: redox-active chromophores for the construction of extended pi-conjugated materials

An efficient synthetic approach to construct a fully substituted benzo[1,2-b:4,5-b']difuran (BDF) 2a via base-catalyzed double annulations is presented. Compound 2a can readily undergo Suzuki, Heck, and Sonogashira coupling reactions to afford in good yields a manifold of extended pi-conjugated BDF derivatives, e.g., with pyridine termini (4-6) and with different spacers. These are highly luminescent materials that undergo two reversible one-electron oxidations. Remarkably, their photophysical and electrochemical properties can be largely tuned by methylation or protonation. Consequently, they can function as pH-dependent fluorescence switches. Finally, the observed electronic properties are explained on the basis of density functional theory.

Synergistic antitumor effect of TRAIL and adriamycin on the human breast cancer cell line MCF-7

The aim of the present study was to determine the effect of the combination of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and adriamycin (ADM) on the human breast cancer cell line MCF-7 and to identify potential mechanisms of apoptosis. Cell viability was analyzed by the MTT assay and the synergistic effect was assessed by the Webb coefficient. Apoptosis was quantified using the annexin V-FITC and propidium iodide staining flow cytometry. The mRNA expression of TRAIL receptors was measured by RT-PCR. Changes in the quantities of Bax and caspase-9 proteins were determined by Western blot. MCF-7 cells were relatively resistant to TRAIL (IC50 >10 microg/mL), while MCF-7 cells were sensitive to ADM (IC50 <10 microg/mL). A subtoxic concentration of ADM (0.5 microg/mL) combined with 0.1, 1, or 10 microg/mL TRAIL had a synergistic cytotoxic effect on MCF-7 cells, which was more marked with the combination of TRAIL (0.1 microg/mL) and ADM (0.5 microg/mL). In addition, the combined treatment with TRAIL and ADM significantly increased cell apoptosis from 9.8% (TRAIL) or 17% (ADM) to 38.7%, resulting in a synergistic apoptotic effect, which is proposed to be mediated by up-regulation of DR4 and DR5 mRNA expression and increased expression of Bax and caspase-9 proteins. These results suggest that the combination of TRAIL and ADM might be a promising therapy for breast cancer.

Recombinant human growth hormone improves survival and protects against acute lung injury in murine Staphylococcus aureus sepsis

OBJECTIVE

To investigate whether recombinant human growth hormone (rhGH) reduces mortality and protects against Staphylococcus aureus sepsis-induced acute lung injury.

METHODS

The bacteria-positive rate of blood smears and bacteria colony counts in bacteria plate culture, TNFalpha and IL-10 plasma levels, lung injury score, expression of intercellular adhesion molecule-1 (ICAM-1) as well as activation of nuclear factor-kappa B (NF-kappaB) in the lungs were determined 6, 12 and 24 h after 140 KM mice were injected with physiologic saline (i.p. group C, n = 20); S. aureus E311122 (1.75 x 10(12) cfu/L, 40 ml/kg, i.p. group S, n = 60); or S. aureus (as group S) with a subsequent treatment of rhGH (1.0 U kg(-1) day(-1)), i.m. group T, n = 60). The cumulative survival rate of an additional 15 mice from each group was followed for 7 days post S. aureus injection.

RESULTS

rhGH treatment significantly increased IL-10 plasma levels and the 7-day cumulative survival rate, whereas the bacteria-positive rate of blood smears, bacteria colony counts in bacteria plate cultures, lung injury score, ICAM-1 and NF-kappaB expression in the lungs were significantly reduced. In addition, rhGH treatment significantly suppressed the S. aureus sepsis-induced elevation of TNFalpha plasma levels.

CONCLUSIONS

These results indicate an ability of rhGH to prevent S. aureus sepsis-induced acute lung injury in mice, which may be attributed to attenuation of increased plasma TNFalpha levels, and elevated IL-10 plasma levels as well as reduced ICAM-1 expression and inhibited NF-kappaB activity in the lungs.