Friday, August 21, 2009
Evidence for electro-chemical interactions between multi-walled carbon nanotubes and human macrophages
Carbon multi-walled nanotubes (MWCNTs) may have several dangerous effects on different cell systems, but the mechanisms responsible for their cytotoxicity are not well known yet. At present, very little is known about the electrical interactions between nanomaterials and cells. We aimed to verify whether MWCNT electrical properties could affect the so called “charge-sensitive” cell parameters, interacting with cellular electrical activity. Human macrophages were challenged with two fully characterised MWCNT samples, one tested as-prepared (MWCNT), the other one purified (by annealing at 2400 °C) and better electro-conductive (a-MWCNT). Our findings show that a-MWCNTs are less cytotoxic but possess a higher inflammatory potential, as compared to MWCNTs.
Moreover, only annealed and better conductive MWCNTs affect significantly the mitochondrial membrane polarity, the intracellular pH and the reorganisation of cytoskeleton actin filaments, cell functions strictly dependent on electro-chemical mechanisms. Based on our results, there is evidence for electro-chemical interactions taking place between cell membranes and electro-conductive MWCNTs. Such a specific behaviour could have wide-range applications in the biomedical field, not only concerning those cellular systems (neuronal and bone cells) sensitive to electrical stimuli, but also other cell systems.
(Silvana Fiorito, et al., Carbon Volume 47, Issue 12, 2009, Pages 2789-2804, doi:10.1016/j.carbon.2009.06.023)
Moreover, only annealed and better conductive MWCNTs affect significantly the mitochondrial membrane polarity, the intracellular pH and the reorganisation of cytoskeleton actin filaments, cell functions strictly dependent on electro-chemical mechanisms. Based on our results, there is evidence for electro-chemical interactions taking place between cell membranes and electro-conductive MWCNTs. Such a specific behaviour could have wide-range applications in the biomedical field, not only concerning those cellular systems (neuronal and bone cells) sensitive to electrical stimuli, but also other cell systems.
(Silvana Fiorito, et al., Carbon Volume 47, Issue 12, 2009, Pages 2789-2804, doi:10.1016/j.carbon.2009.06.023)
A novel nanostructured poly(lactic-co-glycolic-acid)–multi-walled carbon nanotube composite for blood-contacting applications: Thrombogenicity studies
Composite films of poly(lactic-co-glycolic-acid) with multi-walled carbon nanotubes (PLGA–MWCNT) having two different nanotube orientations, namely random and vertically aligned, have been fabricated and characterized. The effect of these nanostructured surfaces on platelet adhesion is evaluated. In particular, the thrombogenicity of the nanostructured composite films is compared with that of pristine graphite (a low thrombogenic material) and PLGA film, in order to determine the influence of surface chemistry and topography on platelet adhesion. The results in this study show that the PLGA–MWCNT composite with vertically aligned nanotubes exhibits very low levels of fibrinogen adsorption and platelet adhesion, which can be attributed to both chemical and topographical effects. Platelet adhesion shows a good correlation with the presence of (Li Buay Koh, Isabel Rodriguez and Subbu S. Venkatraman, Acta Biomaterialia
Article in Press,
doi:10.1016/j.actbio.2009.06.003)Carbon nanotubes-graft-polyglycerol: Biocompatible hybrid materials for nanomedicine
New biocompatible and water soluble hybrid materials containing multi-wall carbon nanotubes (MWCNTs) as core and hyperbranched polyglycerol (PG) as shell were synthesized successfully. In this work, pristine MWCNTs were opened and functionalized through treatment with acid and polyglycerol was covalently grafted onto their surface by the “grafting from” approach based on in-situ ring-opening polymerization of glycidol. Some short-term In vitro cytotoxicity and hemocompatibility tests were conducted on HT1080 cell line (human Fibrosarcoma), because this epithelial cell line can be one of the first route of entry of the exogenous materials to the vascular system and therefore subsequent interactions with the whole body, in order to investigate their potential application in nanomedicine and to understand the limitation and capability of these material as nanoexcipients in biological systems.(Mohsen Adeli, Narjes Mirab, Mohammad Shafiee Alavidjeh, Zahra Sobhani and Fatemeh Atyabi, Polymer Volume 50, Issue 15, 17 July 2009, Pages 3528-3536, doi:10.1016/j.polymer.2009.05.052)
Gas sensors for ammonia detection based on polyaniline-coated multi-wall carbon nanotubes
Polyaniline-coated multi-wall carbon nanotubes (PANI-coated MWNTs) were prepared by in situ polymerization method. Field emission scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and thermogravimetric analysis were used to characterize the as-prepared PANI-coated MWNTs. Obtained results indicated that PANI was uniformly coated on MWNTs, and the thickness of the coatings can be controlled by changing the weight ratios of aniline monomer and MWNTs in the polymerization process. Sensors were fabricated by spin-coating onto pre-patterned electrodes, and ammonia gas sensing properties of the as-prepared PANI-coated MWNTs were studied. The results showed a good response and reproducibility towards ammonia at room temperature. In addition, PANI-coated MWNTs exhibited a linear response to ammonia in the range of 0.2–15 ppm. The effects of the thickness of PANI coatings on the gas sensing properties were also investigated in detail. The results suggest a potential application of PANI-coated MWNTs in gas sensor for detecting ammonia.
(Lifang He, Yong Jia, Fanli Meng, Minqiang Li, and Jinhuai Liu, Materials Science and Engineering: B 163, Issue 2, 15 July 2009, Pages 76-81, doi:10.1016/j.mseb.2009.05.009)
(Lifang He, Yong Jia, Fanli Meng, Minqiang Li, and Jinhuai Liu, Materials Science and Engineering: B 163, Issue 2, 15 July 2009, Pages 76-81, doi:10.1016/j.mseb.2009.05.009)
Toxicity and imaging of multi-walled carbon nanotubes in human macrophage cells
Multi-walled carbon nanotubes (MWNTs) have been proposed for use in many applications and concerns about their potential effect on human health have led to the interest in understanding the interactions between MWNTs and human cells. One important technique is the visualisation of the intracellular distribution of MWNTs. We exposed human macrophage cells to unpurified MWNTs and found that a decrease in cell viability was correlated with uptake of MWNTs due to mainly necrosis. Cells treated with purified MWNTs and the main contaminant Fe2O3 itself yielded toxicity only from the nanotubes and not from the Fe2O3. We used 3-D dark-field scanning transmission electron microscopy (DF-STEM) tomography of freeze-dried whole cells as well as confocal and scanning electron microscopy (SEM) to image the cellular uptake and distribution of unpurified MWNTs. We observed that unpurified MWNTs entered the cell both actively and passively frequently inserting through the plasma membrane into the cytoplasm and the nucleus. These suggest that MWNTs may cause incomplete phagocytosis or mechanically pierce through the plasma membrane and result in oxidative stress and cell death.(Crystal Cheng, Karin H. Müller, Krzysztof K.K. Koziol, Jeremy N. Skepper, Paul A. Midgley, Mark E. Welland, and Alexandra E. Porter, Biomaterials 30, Issue 25, September 2009, Pages 4152-4160, doi:10.1016/j.biomaterials.2009.04.019)
Multifunctionality of single-walled carbon nanotube–polytetrafluoroethylene nanocomposites
Multifunctional nanocomposites are increasingly needed for applications requiring prescribed sets of physical and chemical properties. Polytetrafluoroethylene (PTFE) is a popular solid lubricant due to its low friction coefficient, high chemical inertness, high thermal range and biocompatibility, but its use is limited by high rates of wear. Low loadings of nanoparticle fillers have reduced PTFE wear by 3–4 orders of magnitude, but these materials lack the mechanical, electrical or thermal properties needed for high performance applications.In this study, single-walled carbon nanotubes (SWCNT) are investigated as a route to improve wear resistance, toughness and electrical conductivity of PTFE without sacrificing low friction, high temperature capability or chemical inertness. Tribological, tensile and surface electrical measurements were made for 0, 2, 5, 10 and 15 wt.% SWCNT filled PTFE nanocomposites. A dramatic reduction in electrical resistance reflected networking (percolation) of the nanotubes at 2 wt.%. All of the nanocomposites had significantly improved electrical, mechanical and wear performance. Above 2 wt.%, electrical conductivity was reduced by more than six orders of magnitude. At 2 wt.%, ultimate engineering stress was improved by approximately 50%, true stress increased by 200%, engineering strain increased by two orders of magnitude (
10,000%). At 5 wt.%, wear resistance improved by more than 20 times and friction coefficient increased by 50%.(J.R. Vail, D.L. Burris, and W.G. Sawyer, Wear 267, Issues 1-4, 15 June 2009, Pages 619-624,
doi:10.1016/j.wear.2008.12.117)Effects of carbon nanotubes on primary neurons and glial cells
Carbon nanotubes (CNTs) are among the most promising novel nanomaterials and their unique chemical and physical properties suggest an enormous potential for many areas of research and applications. As a consequence, the production of CNT-based material and thus the occupational and public exposure to CNTs will increase steadily. Although there is evidence that nanoparticles (NPs) can enter the nervous system via the blood stream, olfactory nerves or sensory nerves in the skin, there is still only little knowledge about possible toxic effects of CNTs on cells of the nervous system.The goal of the present study was to analyse the influences of single-walled CNTs (SWCNTs) with different degrees of agglomeration on primary cultures derived from chicken embryonic spinal cord (SPC) or dorsal root ganglia (DRG). As measured by the Hoechst assay treatment of mixed neuro-glial cultures with up to 30 μg/mL SWCNTs significantly decreased the overall DNA content. This effect was more pronounced if cells were exposed to highly agglomerated SWCNTs as compared to better dispersed SWCNT-bundles. Using a cell-based ELISA we found that SWCNTs reduce the amount of glial cells in both peripheral nervous system (PNS) and central nervous system (CNS) derived cultures. Neurons were only affected in DRG derived cultures, where SWCNT treatment resulted in a decreased number of sensory neurons, as measured by ELISA. Additionally, whole-cell patch recordings revealed a diminished inward conductivity and a more positive resting membrane potential of SWCNT treated DRG derived neurons compared to control samples.
The SWCNT suspensions used in this study induced acute toxic effects in primary cultures from both, the central and peripheral nervous system of chicken embryos. The level of toxicity is at least partially dependent on the agglomeration state of the tubes. Thus if SWCNTs can enter the nervous system at sufficiently high concentrations, it is likely that adverse effects on glial cells and neurons might occur.
(Larisa Belyanskaya, Stefan Weigel, Cordula Hirsch, Ursina Tobler, Harald F. Krug, and Peter Wick, NeuroToxicology, Article in Press, 2009, doi:10.1016/j.neuro.2009.05.005)
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