Kinetics of the release of elemental precursors of syngas and syngas contaminants during devolatilization of switchgrass.

In this study, the results from laboratory measurements of the devolatilization kinetics of switchgrass in a rapidly heated fixed bed reactor flushed with argon and operated at constant temperatures between 600 and 800°C was reported. Results indicate that switchgrass decomposes in two sequential stages during pyrolysis: stage I involves the evaporation and devolatilization of water and extractives and stage II involves that of hemicellulose, cellulose, and lignin. The estimated global activation energy for stage II increased from 52.80 to 59.39kJ/mol as the reactor temperature was increased from 600 to 800°C. The maximum conversion of carbon, hydrogen, oxygen, sulfur, and nitrogen ranged from 0.68 to 0.70, 0.90 to 0.95, 0.88 to 0.91, 0.70 to 0.80, and 0.55 to 0.66, respectively. The retention of alkali and alkaline earth metal (AAEM) species in the solid char after complete pyrolysis was significantly higher than in the original feed, indicating the importance of AAEM species in subsequent char processing.

The influence of bisnaphthalimidopropyl polyamines on DNA instability and repair in Caco-2 colon epithelial cells.

Bisnaphthalimido compounds bis-intercalate to DNA via the major groove and are potentially potent cancer therapeutics. Previously, we incorporated natural polyamines as linkers connecting the two naphthalimido ring moieties to create a series of soluble bisnaphthalimidopropyl polyamines (BNIPPs). Here, extending earlier work on bisnaphthalimidopropylspermidine (BNIPSpd)-induced apoptosis in colon adenocarcinoma Caco-2 cells, we compare the cytotoxicity and genotoxicity of BNIPSpd relative to the spermine and oxaspermine derivatives, bisnaphthalimidopropylspermine (BNIPSpm) and bisnaphthalimidopropyloxaspermine (BNIPOSpm). The order of cytotoxicity after 24 h was BNIPSpd (IC(50) = 0.47 µM) > BNIPSpm (IC(50) = 10.04 µM) > BNIPOSpm (IC(50) >50 µM). After a 72-h BNIPOSpm exposure, an IC(50) = 10.25 µM was achieved. With 4-h exposure to BNIPSpd or BNIPSpm or 12-h exposure to BNIPOSpm, concentrations ≥1 µM induced a significant dose-dependent increase in DNA damage as measured by alkaline single-cell gel electrophoresis. The longer incubation times required for BNIPOSpm to induce DNA strand breaks reflect a slower rate of BNIPOSpm cellular distribution as monitored via BNIPP fluorescence within the cells. Moreover, exposure to a non-genotoxic concentration of BNIPSpd, BNIPSpm (0.1 µM for 4 h) or BNIPOSpm (0.1 µM for 12 h) induced a significant decrease in repair of oxidative DNA damage induced by hydrogen peroxide. In conclusion, BNIPP exposure in Caco-2 cells is associated with significant induction of DNA damage and inhibition of DNA repair at non-genotoxic concentrations. The latter is a novel consequence of BNIPP-cell interactions which adds to the spectrum of therapeutically relevant activities that may be exploited for the design and development of naphthalimide-based therapeutics.

Cell response to dextran-derivatised iron oxide nanoparticles post internalisation.

Magnetic nanoparticles have been used for many years as magnetic resonance imaging contrast agents. Despite the fact that there are currently several dextran-coated iron oxide nanoparticles are in preclinical and clinical use, there is very little information available concerning the influence such particles have on cells in culture. The prerequisite for particles employed as contrast agents is capture and subsequent uptake by cells. This study involved the use of magnetic nanoparticles synthesised and derivatised with dextran, compared to similar underivatised plain particles. The influence in vitro was assessed using human dermal fibroblasts and various techniques to observe cell-particles interaction, including light and fluorescence microscopy, scanning and transmission electron microscopy. The results indicate that although both the uncoated and the dextran-derivatised particles are uptaken into the cell, the derivatised particles induce alterations in cell behaviour and morphology distinct from the plain particles, suggesting that cell response is dependent on the particles coating.

The influence of transferrin stabilised magnetic nanoparticles on human dermal fibroblasts in culture.

Magnetic nanoparticles have been used for bio-medical purposes including drug delivery, cell destruction and as MRI contrast agents for several years. A more recent biological application has focused on targeted drug delivery. To this end, a wide variety of iron oxide nanoparticles have been synthesised. This study involves the use of magnetic nanoparticles synthesised and derivatised with human transferrin, compared to identical underivatised particles. Human fibroblasts were used, representative of a tissue cell-type. The influence in vitro was determined using light and fluorescence microscopy, scanning and transmission electron microscopy, and 1718 gene microarray. The results indicate that the transferrin derivatised particles appear to localise to the cell membrane without instigating receptor-mediated endocytosis, and also induce up-regulation in the cells for many genes, particularly in the area of cytoskeleton and cell signalling. The microscopy results further support these findings.

Dextran and albumin derivatised iron oxide nanoparticles: influence on fibroblasts in vitro.

Magnetic nanoparticles have been used for biomedical purposes for several years. In recent years, nanotechnology has developed to a stage that makes it possible to engineer particles to provide opportunities for the site-specific delivery of drugs. To this end a variety of iron oxide particles have been synthesised. The size and surface of the particles are crucial factors in the application of the particles. This study therefore involves the use of magnetic nanoparticles synthesised and derivatised with either dextran or albumin, compared to identical underivatised plain particles. This influence in vitro was assessed using human dermal fibroblasts and various techniques to observe cell-particles interaction, including light and fluorescence microscopy, scanning and transmission electron microscopy. The results indicate that the derivatised particles induce alterations in cell behaviour and morphology distinct from the plain particles, suggesting that cell response can be directed via specifically engineered particle surfaces.