Radiation-Induced Senescence Reprograms Secretory and Metabolic Pathways in Colon Cancer HCT-116 Cells

Understanding the global metabolic changes during the senescence of tumor cells can have implications for developing effective anti-cancer treatment strategies. Ionizing radiation (IR) was used to induce senescence in a human colon cancer cell line HCT-116 to examine secretome and metabolome profiles. Control proliferating and senescent cancer cells (SCC) exhibited distinct morphological differences and expression of senescent markers. Enhanced secretion of pro-inflammatory chemokines and IL-1, anti-inflammatory IL-27, and TGF-β1 was observed in SCC. Significantly reduced levels of VEGF-A indicated anti-angiogenic activities of SCC. Elevated levels of tissue inhibitors of matrix metalloproteinases from SCC support the maintenance of the extracellular matrix. Adenylate and guanylate energy charge levels and redox components NAD and NADP and glutathione were maintained at near optimal levels indicating the viability of SCC. Significant accumulation of pyruvate, lactate, and suppression of the TCA cycle in SCC indicated aerobic glycolysis as the predominant energy source for SCC. Levels of several key amino acids decreased significantly, suggesting augmented utilization for protein synthesis and for use as intermediates for energy metabolism in SCC. These observations may provide a better understanding of cellular senescence basic mechanisms in tumor tissues and provide opportunities to improve cancer treatment.     

Influence of traditional agricultural practices on mobilization of arsenic from sediments to groundwater in Bengal delta

In the wake of the idea that surface derived dissolved organic carbon (DOC) plays an important role in the mobilization of arsenic (As) from sediments to groundwater and may provide a vital tool in understanding the mechanism of As contamination (mobilization/fixation) in Bengal delta; a study has been carried out. Agricultural fields that mainly cultivate rice (paddy fields) leave significantly large quantities of organic matter/organic carbon on the surface of Bengal delta which during monsoon starts decomposing and produces DOC. The DOC thus produced percolates down with rain water and mobilizes As from the sediments. Investigations on sediment samples collected from a paddy field clearly indicate that As coming on to the surface along with the irrigation water accumulates itself in the top few meters of sediment profile. The column experiments carried out on a 9 m deep sediment profile demonstrates that DOC has a strong potential to mobilize As from the paddy fields and the water recharging the aquifer through such agricultural fields contain As well above the WHO limit thus contaminating the shallow groundwater. Experiment also demonstrates that decay of organic matter induces reducing condition in the sediments. Progressively increasing reducing conditions not only prevent the adsorption of As on mineral surfaces but also cause mobilization of previously sorbed arsenic. There seems to be a cyclic pattern where As from deeper levels comes to the surface with irrigational water, accumulates itself in the sediments, and ultimately moves down to the shallow groundwater. The extensive and continual exploitation of intermediate/deep groundwater accelerates this cyclic process and helps in the movement of shallow contaminated groundwater to the deeper levels.     

Phenothiazine conjugated bipyridine as ancillary ligand in Ru(II)-complexes for application in dye sensitized solar cell

A new high molar extinction coefficient ruthenium(II)-bipyridine complex “cis-Ru(4,4′-bis((E)-2-(10-decyl-10H-phenothiazin-3-yl)vinyl)-2,2′-bipyridine)(4,4′-dicarboxylic acid-2,2′-bipyridine)(NCS)₂ PTZ1″ was synthesized through conjugation of phenothiazine unit with bipyridine and characterized by FT-IR, ¹H-NMR and ESI-MASS spectroscopes. Absorption measurements and time dependent-density functional theory (TD-DFT) calculations show increased spectral response for the ancillary ligand and the corresponding complex. The dye upon anchoring onto mesoporous nanocrystalline TiO₂ solar cells exhibited solar-to-electric energy conversion efficiency (η) of 3.77% short-circuit photocurrent density (J_SC) = 7.79 mA/cm², open-circuit voltage (V_OC) = 640 mV, fill factor = 0.750) under air mass 1.5 sunlight, the reference Z907 and HRS1sensitized solar cells, fabricated and evaluated under identical conditions exhibited η-value of 7.02% (J_SC = 15.25 mA/cm², V_OC = 650 mV, fill factor = 0.705) and 3.05% (J_SC = 8.20 mA/cm², V_OC = 610 mV, fill factor = 0.620) respectively. The lower film absorption of PTZ1on TiO₂ surface could be probably due to larger molecular diameter and planarity of phenothiazine prone to aggregate in solution as well as on TiO₂ surface. The DFT calculations show that the first three HOMOs of PTZ1 have t2g character as observed in case of Z907, while HOMO-4 and HOMO-5 have π-orbitals with major component on phenothiazine moieties of L1.     

Polypyridyl Ru(II)-sensitizers with extended π-system enhances the performance of dye sensitized solar cells

New polypyridyl ruthenium(II) complexes “cis-Ru(4,4′-dimesityl-2,2′-bipyridine) (Ln) (NCS)₂ H102” and “cis-Ru(4,4′-bis(2,3,6-tri-isopropylphenyl)-2,2′-bipyridine) (Ln) (NCS)₂ H105”, where Ln = 4,4′-dicarboxylic acid-2,2′-bipyridine; were synthesized and successfully applied to sensitization of nano-crystalline TiO₂ based solar cells (DSSCs). The DSSCs of H102 and H105 fabricated from 0.16 cm² TiO₂ electrodes exhibited broader comparable photocurrent action spectra with almost identical solar-to-electrical energy conversion efficiency (η) as compared to N719 sensitizer. The incident photon-to-current conversion efficiency (IPCE) values of 98% and 95% were obtained for H102 and H105 sensitizers respectively. Under 1 sun condition, η-values of 8.39% (short-circuit photocurrent (J_SC) = 16.4 mA/cm², open-circuit photo voltage (V_OC) = 692 mV, fill factor = 0.734), 8.76% (J_SC = 16.3 mA/cm², V_OC = 735 mV, fill factor = 0.734) and 9.12% (J_SC = 16.1 mA/cm², V_OC = 745 mV, fill factor = 0.753) were obtained for H102, H105 and N719 sensitizers respectively.     

Simple metal-free organic D-pi-A dyes with alkoxy- or fluorine substitutions: application in dye sensitized solar cells

Two new metal-free organic sensitizers with simplest structural variations have been synthesized for application in nanocrystalline TiO2 sensitized solar cells. The donor-pi-bridge-acceptor (D-pi-A) structure dyes, Y2 and Y3 each designed with three parts, an electron donor unit (substituted phenyl), a linker unit (thiophene), and an anchor unit (cyanoacrylic acid) showed maximal monochromatic incident photon to current conversion efficiencies (IPCE) in a device reaching upto 67% and 82% respectively. The organic sensitizers with 3,4,5-trimethoxy phenyl (Y3) as donor moieties obtained better solar light to electrical energy conversion efficiencies of 3.30% where as the organic sensitizer with 2,4-difluoro phenyl as donor (Y2) showed comparatively lower efficiency of 1.02%. The efficiency obtained with the reference sensitizer N719 under similar fabrication and evaluation conditions was 5.84%.     

Shining light on panchromatic ruthenium sensitizers towards dye-sensitized photocatalytic hydrogen evolution

Five new photocatalysts have been synthesized in order to extend the photo response upto visible range, by adsorbing MC113-MC117 ruthenium complexes on TiO₂-Pt composites. Highlight harvesting properties of these ruthenium complexes instigated us to evaluate for photocatalytic activity. The absorption curves of the synthesized photocatalysts extended up to 750 nm. Morphological studies of photocatalysts have been carried out using SEM and powder X-ray crystallography. Among all photocatalysts, MC113PC showed high photocatalytic activity i.e. 9474 TONs. IPCE and fluorescence quenching studies of the catalysts revealed the light harvesting nature and electron injection efficiency. The photocatalytic activity of MC photocatalysts were systematically screened at different pH and employing different sacrificial electron donors (SED) in order to obtain optimal photocatalytic performance.     

Novel ruthenium sensitizer with multiple butadiene equivalent thienyls as conjugation on ancillary ligand for dye-sensitized solar cells

A heteroleptic polypyridyl ruthenium complex ‘cis-Ru(4,4′-bis(3,5-bis(5-hexylthiophen-2-yl)phenyl)-2,2′-bipyridine)(4,4′-dicarboxyl-2,2′-bipyridine) (NCS)₂, MC102′, with a high molar extinction coefficient was synthesized and characterized with IR, ¹H NMR, Mass, UV–Vis spectroscopy. The test cell DSSC devices constructed with 0.23 cm² active area photo-electrode in combination with an electrolyte composed of 0.6 M dimethylpropyl-imidazolium iodide (DMPII), 0.05 M I₂, and 0.1 M LiI in acetonitrile yielded solar to electric energy conversion efficiency (η) of 4.42% under Air Mass (AM) 1.5 sunlight, while the reference N719 sensitized solar cell fabricated and evaluated under similar conditions exhibited η-value of 5.84%.     

Desalination of Seawater using Geothermal Energy to Meet Future Fresh Water Demand of Saudi Arabia

The future economy of the Middle East countries (GDP growth) depends on the availability of fresh water for domestic and agricultural sectors. Saudi Arabia, for example, consumes 275 L/day per capita of water that is generated from desalination process using 134 x 10⁶ kWh of electricity. With 6 % population growth rate, demand for fresh water from fossil fuel based desalination plants will grow at an alarming rate. It has been reported that Saudi Arabia’s reliance on fossil fuels to generate electricity and generate fresh water through desalination using the same energy source is economically and politically unsustainable. This may lead to destabilisation of the global economy. However, Saudi Arabia has large geothermal resources along the Red Sea coast that can be developed to generate power and support the generation of fresh water through desalination. The cost of fresh water can be further lowered from the current US$ 0.03/m³. Among the gulf countries, Saudi Arabia can become the leader in controlling CO₂ emissions and mitigating the impact on climate change and agricultural production. This will enable the country to meet the growing demand of food and energy for the future population for several decades and to reduce food imports.     

The potential contribution of geothermal energy to electricity supply in Saudi Arabia

With increase in demand for electricity at 7.5% per year, the major concern of Saudi Arabia is the amount of CO₂ being emitted. The country has the potential of generating 200×10⁶ kWh from hydrothermal sources and 120×10⁶ terawatt hour from Enhanced Geothermal System (EGS) sources. In addition to electricity generation and desalination, the country has substantial source for direct application such as space cooling and heating, a sector that consumes 80% of the electricity generated from fossil fuels. Geothermal energy can offset easily 17 million kWh of electricity that is being used for desalination. At least a part of 181,000 Gg of CO₂ emitted by conventional space cooling units can also be mitigated through ground-source heat pump technology immediately. Future development of EGS sources together with the wet geothermal systems will make the country stronger in terms of oil reserves saved and increase in exports.