Systematic investigation of experimental parameters on nitrogen incorporation into carbon nanotube forests

Nitrogen doping carbon nanotubes can enhance their beneficial physical and chemical properties, rendering them more desirable for various applications, e.g., in electronics. In this study, we used catalytic chemical vapor deposition to synthesize carbon na-no-tube forests on different substrates. The samples were prepared in the presence of compounds containing nitrogen (ammonia, acetonitrile, tripropylamine, and their mixture with acetone) that were introduced into the reactor by bubbling or injection. Of the two different nitrogen introduction methods, the direct injection of a liquid nitrogen precursor promoted the synthesis of bamboo-structured carbon nanotube forests more efficiently. It was found in the injection experiments that the amount of precursor affected the extent of nitrogen incorporation. The presence of various nitrogen species in CNTs was also identified, and the manner in which temperature and the presence of hydrogen both influence nitrogen incorporation into the carbon na-no-tubes was observed

In vitro analysis of the anti-inflammatory effect of inhomogeneous static magnetic field-exposure on human macrophages and lymphocytes.

The effect of inhomogeneous static magnetic field (SMF)-exposure on the production of different cytokines from human peripheral blood mononuclear cells (PMBC), i.e., lymphocytes and macrophages, was tested in vitro. Some cultures were activated with lipopolysaccharide (LPS) at time point -3 h and were either left alone (positive control) or exposed to SMF continuously from 0 until 6, 18, or 24 h. The secretion of interleukin IL-6, IL-8, tumor necrosis factor TNF-α, and IL-10 was tested by ELISA. SMF-exposure caused visible morphological changes on macrophages as well as on lymphocytes, and also seemed to be toxic to lymphocytes ([36.58; 41.52]%, 0.308≤p≤0.444), but not to macrophages (<1.43%, p≥0.987). Analysis of concentrations showed a significantly reduced production of pro-inflammatory cytokines IL-6, IL-8, and TNF-α from macrophages compared to negative control ([56.78; 87.52]%, p = 0.031) and IL-6 compared to positive control ([45.15; 56.03]%, p = 0.035). The production of anti-inflammatory cytokine IL-10 from macrophages and from lymphocytes was enhanced compared to negative control, significantly from lymphocytes ([-183.62; -28.75]%, p = 0.042). The secretion of IL-6 from lymphocytes was significantly decreased compared to positive control ([-115.15; -26.84]%, p = 0.039). This massive in vitro evidence supports the hypotheses that SMF-exposure (i) is harmful to lymphocytes in itself, (ii) suppresses the release of pro-inflammatory cytokines IL-6, IL-8, and TNF-α, and (iii) assists the production of anti-inflammatory cytokine IL-10; thus providing a background mechanism of the earlier in vivo demonstrated anti-inflammatory effects of SMF-exposure

Systematic Investigation of Experimental Parameters on Nitrogen Incorporation into Carbon Nanotube Forests

Nitrogen doping carbon nanotubes can enhance their beneficial physical and chemical properties, rendering them more desirable for various applications, e.g., in electronics. In this study, we used catalytic chemical vapor deposition to synthesize carbon na-no-tube forests on different substrates. The samples were prepared in the presence of compounds containing nitrogen (ammonia, acetonitrile, tripropylamine, and their mixture with acetone) that were introduced into the reactor by bubbling or injection. Of the two different nitrogen introduction methods, the direct injection of a liquid nitrogen precursor promoted the synthesis of bamboo-structured carbon nanotube forests more efficiently. It was found in the injection experiments that the amount of precursor affected the extent of nitrogen incorporation. The presence of various nitrogen species in CNTs was also identified, and the manner in which temperature and the presence of hydrogen both influence nitrogen incorporation into the carbon na-no-tubes was observed

Evaluation of cell viability.

<p>Number of viable A) macrophages and B) lymphocytes at baseline and at 24 h. Cultures were exposed to different treatments: negative control: no treatment; LPS: lipopolysaccharide-activated; SMF: SMF-exposed; LPS+SMF: lipopolysaccharide-activated and SMF-exposed.</p

Cytokine profile release by lymphocytes.

<p>Concentration of A) IL-6 and B) IL-10 released from lymphocytes in 24 h under different treatments. Positive error bars show SD values. * and × denote significant differences (<i>p</i><0.05) to corresponding negative or positive control (LPS), respectively as estimated with Games-Howell <i>post hoc</i> analysis.</p

Effect sizes and corresponding significances for OD₄₅₀ and for concentration values of pro-inflammatory (IL-6, IL-8, TNF-α) and anti-inflammatory (IL-10) cytokines produced by macrophages or lymphocytes under lipopolysaccharide <i>(</i>LPS) activation and/or static magnetic field (SMF)-exposure in the 6–24 h time period.

*<p>and × denote significant differences (<i>p</i><0.05) to negative and positive control, respectively as estimated with Games-Howell <i>post hoc</i> test.</p

Effect of SMF exposure on cytokine release by macrophages.

<p>Effect of cytokine release from macrophages under SMF-exposure compared to A) negative and B) positive (LPS) control, respectively as estimated from OD₄₅₀ data. * and × denote significant differences (<i>p</i><0.05) to negative and positive control, respectively. Positive effect means inhibition, negative means assistance. Probabilities of significance can be found in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0072374#pone-0072374-t001" target="_blank">Table 1</a>.</p

Effect of SMF exposure on cytokine release by lymphocytes.

<p>Effect of cytokine release from lymphocytes under SMF-exposure compared to A) negative and B) positive (LPS) control, respectively as estimated from OD₄₅₀ data. * and × denote significant differences (<i>p</i><0.05) to negative and positive control, respectively. Positive effect means inhibition, negative means assistance. Probabilities of significance can be found in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0072374#pone-0072374-t001" target="_blank">Table 1</a>.</p