Carbon Nanotubes Promote Growth and Spontaneous Electrical Activity in Cultured Cardiac Myocytes

Nanoscale manipulations of the extracellular microenvironment are increasingly attracting attention in tissue engineering. Here, combining microscopy, biological, and single-cell electrophysiological methodologies, we demonstrate that neonatal rat ventricular myocytes cultured on substrates of multiwall carbon nanotubes interact with carbon nanotubes by forming tight contacts and show increased viability and proliferation. Furthermore, we observed changes in the electrophysiological properties of cardiomyocytes, suggesting that carbon nanotubes are able to promote cardiomyocyte maturation

Gene Ontology enrichment analysis showing gene categories whose expression is modulated by MWCNTs.

<p>See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0073621#pone.0073621.s002" target="_blank">Table S2</a> for statistics.</p

Carbon nanotubes substrate selectively affects membrane properties and neurite extension of spinal neurons.

<p>(A) Spinal neurons grown on MWCNT show similar resting potential and membrane resistance (R_input) with respect to control neurons (top), while membrane capacitance, indicative of total cell membrane extension, is significantly lower in CNT neurons (bottom left, ***: P<0.001; bottom right, cumulative distribution, KS test: P<0.01). (B) Top, typical examples of spinal cord neurons cultured in control condition or on MWCNTs, labeled with the antibody against the neuronal marker β-tubulin III to visualize neuronal morphology. Bottom, despite a similar neuronal density (left), CNT cultures showed a slightly, but significantly lower somatic neuronal diameter compared to control cultures (middle; ***: P<0.001), together with a lower number of long neurites (right; *: P<0.05). These findings are in agreement with the lower membrane capacitance values found in CNT neurons. (C) SEM images of neurites from spinal neurons grown on a MWCNT layer, showing the numerous and very tight contacts between MWCNTs and neuronal membranes (red arrows).</p

The expression of <i>Alox15</i> and <i>Robo1</i> is increased by MWCNT substrate.

<p>(A) Top left, Western blot analysis of the Alox15 protein (migrated at approximately 80 KD) isolated from control (left lane) and CNT (right lane) spinal cultures, showing the strong increase in Alox15 expression in CNT cultures. Top right, quantification of the Alox15 protein level normalized against actin. Bottom, confocal images of control and CNT neurons, stained using the anti-Alox15 antibody. Note the punctate appearance of strongly Alox15-immunopositive cytoplasmatic structures in both culturing conditions. (B) Left, Western blot analysis of the Robo1 protein (migrated at approximately 180 KD) from control (left lane) and CNT (right lane) cultures. Robo1 expression level is unaffected by the MWCNT substrate (right). (C) Time course of <i>Alox15</i> (left) and <i>Robo1</i> (right) expression levels by transcript-specific real time PCR in CNT cultures normalized to control. The expression of both proteins is progressively upregulated in CNT cultures during <i>in vitro</i> development.</p

MWCNTs boost the functional maturation of spinal neurons.

<p>(A) Top left, voltage-clamp stimulation protocol to test the presence of voltage-dependent currents. Top middle (and right, in extended time scale), typical recordings from a spinal neuron displaying voltage-dependent currents. Note the presence of both outward (open arrow, middle panel; K⁺) and inward (filled arrow, right panel; Na⁺) voltage-dependent currents. The fraction of neurons displaying voltage-dependent currents is considerably higher in CNT neurons with respect to controls (bottom left; **: P<0.01), while current density is similar for inward and outward currents in both culturing conditions (bottom middle and right). (B) Left, current-clamp stimulation protocol to test the neuronal ability to generate action potentials. Middle (and right, in extended time scale), example of action potentials generated by a spinal neuron.</p

Knitting the Catalytic Pattern of Artificial Photosynthesis to a Hybrid Graphene Nanotexture

The artificial leaf project calls for new materials enabling multielectron catalysis with minimal overpotential, high turnover frequency, and long-term stability. Is graphene a better material than carbon nanotubes to enhance water oxidation catalysis for energy applications? Here we show that functionalized graphene with a tailored distribution of polycationic, quaternized, ammonium pendants provides an sp² carbon nanoplatform to anchor a totally inorganic tetraruthenate catalyst, mimicking the oxygen evolving center of natural PSII. The resulting hybrid material displays oxygen evolution at overpotential as low as 300 mV at neutral pH with negligible loss of performance after 4 h testing. This multilayer electroactive asset enhances the turnover frequency by 1 order of magnitude with respect to the isolated catalyst, and provides a definite up-grade of the carbon nanotube material, with a similar surface functionalization. Our innovation is based on a noninvasive, synthetic protocol for graphene functionalization that goes beyond the ill-defined oxidation–reduction methods, allowing a definite control of the surface properties