Chitosan/silver nanocomposites: Synergistic antibacterial action of silver nanoparticles and silver ions

In the present work chitosan-silver (CS/Ag) nanocomposites, either in the form of nanoparticles (AgNP) or as ionic dendritic structures (Ag+), are synthesized by a simple and environmentally friendly in situ chemical reduction process. The antibacterial activity of the resulting nanocomposites in the form of films is studied against two bacteria, Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli. The relationship between electrical, structural and antibacterial properties of CS/AgNP and CS/Ag+ nanocomposites are studied by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction, and UV-Vis, impedance, infrared and X-ray photoelectron spectroscopies. The results demonstrate that in contrast to CS/Ag+ ion films, the CS/AgNP composites films (average particle size less than 10 nm) showed a significantly higher antibacterial potency. The collective action of AgNP and Ag+ ions facilitate the enhancement and synergetic antibacterial activity below certain critical concentration. The bactericide activity of both CS/AgNP and CS/Ag+ ion composite films increases by increasing the concentration of Ag. The composites containing 1 wt.% of silver nanoparticles and about of 2 wt.% of silver ions exhibit a maximum antibacterial activity, which is close to their electrical percolation threshold. The concentration of AgNP and Ag+ ions above the threshold level greatly diminish the antibacterial potential. © 2015 Elsevier Ltd. All rights reserved

The effect of methylphenidate and rearing environment on behavioral inhibition in adult male rats

The effect of the type of CNT (functionalized and non-functionalized) on the dielectric relaxation phenomena and conductivity of MWCNT/chitosan (MWCNT/CS) was investigated. Composites were prepared by the solvent cast method by homogeneously dispersing CNT into a CS matrix. FTIR analysis suggests the formation of hydrogen bonding in functionalized-MWCNT/CS whereas the CS remains unaffected in non-functionalized films. In the low conductivity region, the ?-relaxation process associated with a glass transition in CS is affected by the MWCNT; the Vogel temperature increases due to a decrease of the water content. The ?-relaxation exhibits a typical Arrhenius-type temperature dependence that is independent on the moisture content. Strong interfacial interactions of functionalized-MWCNT with the CS matrix are responsible for high values of the contact resistance Rc between individual CNT. Conversely, non-functionalized MWCNTs exhibit a typical 3D percolation threshold at ca. 4 wt %. " 2015 Elsevier B.V. All rights reserved.",,,,,,"10.1016/j.matchemphys.2015.02.041",,,"http://hdl.handle.net/20.500.12104/45086","http://www.scopus.com/inward/record.url?eid=2-s2.0-84924626391&partnerID=40&md5=2077a8248f1178527deca8ec39ee5bde",,,,,,,,"Materials Chemistry and Physics",,"25

Practice patterns and outcomes after stroke across countries at different economic levels (INTERSTROKE):an international observational study

Background: Stroke disproportionately affects people in low-income and middle-income countries. Although improvements in stroke care and outcomes have been reported in high-income countries, little is known about practice and outcomes in low and middle-income countries. We aimed to compare patterns of care available and their association with patient outcomes across countries at different economic levels. Methods: We studied the patterns and effect of practice variations (ie, treatments used and access to services) among participants in the INTERSTROKE study, an international observational study that enrolled 13 447 stroke patients from 142 clinical sites in 32 countries between Jan 11, 2007, and Aug 8, 2015. We supplemented patient data with a questionnaire about health-care and stroke service facilities at all participating hospitals. Using univariate and multivariate regression analyses to account for patient casemix and service clustering, we estimated the association between services available, treatments given, and patient outcomes (death or dependency) at 1 month. Findings: We obtained full information for 12 342 (92%) of 13 447 INTERSTROKE patients, from 108 hospitals in 28 countries; 2576 from 38 hospitals in ten high-income countries and 9766 from 70 hospitals in 18 low and middle-income countries. Patients in low-income and middle-income countries more often had severe strokes, intracerebral haemorrhage, poorer access to services, and used fewer investigations and treatments (p<0·0001) than those in high-income countries, although only differences in patient characteristics explained the poorer clinical outcomes in low and middle-income countries. However across all countries, irrespective of economic level, access to a stroke unit was associated with improved use of investigations and treatments, access to other rehabilitation services, and improved survival without severe dependency (odds ratio [OR] 1·29; 95% CI 1·14–1·44; all p<0·0001), which was independent of patient casemix characteristics and other measures of care. Use of acute antiplatelet treatment was associated with improved survival (1·39; 1·12–1·72) irrespective of other patient and service characteristics. Interpretation: Evidence-based treatments, diagnostics, and stroke units were less commonly available or used in low and middle-income countries. Access to stroke units and appropriate use of antiplatelet treatment were associated with improved recovery. Improved care and facilities in low-income and middle-income countries are essential to improve outcomes