Paste electrodes have been constructed using single-wall carbon nanotubes mixed with mineral oil. The electrochemical behavior of such electrodes prepared with different percentages of carbon nanotubes has been compared with that of graphite paste electrodes and evaluated with respect to the electrochemistry of ferricyanide with cyclic voltammetry. Carbon nanotubes were purified by a treatment with concentrated nitric acid, then oxidized in air. In addition, electrochemical pretreatments were carried out to increase the selectivity of carbon nanotube electrodes. Performances of carbon nanotube paste and carbon paste electrodes were evaluated by studying such parameters as current peak, deltaEp, anodic and cathodic current ratio, and charge density toward several different electroactive molecules. Data interpretation based on the carbon nanotubes and carbon surface area is presented. Carbon nanotube paste and carbon paste electrodes were tested as H2O2 and NADH probes, and several analytical parameters were evaluated. The oxidative behavior of dopamine was examined at these electrodes. The two-electron oxidation of dopamine to dopaminequinone showed an excellent reversibility in cyclic voltammetry that was significantly better than that observed at carbon paste electrodes.

Several in vitro and in vivo studies suggest local and systemic effects following\ud exposure to carbon nanotubes. No data are available, however, on their possible\ud embryotoxicity in mammals. In this study, we tested the effect of pristine and\ud oxidized single-wall carbon nanotubes (SWCNTs) on the development of the mouse\ud embryo. To this end, SWCNTs (from 10 ng to 30 μg/mouse) were administered to\ud female mice soon after implantation (postcoital day 5.5); 10 days later, animals \ud were sacrificed, and uteri, placentas, and fetuses examined. A high percentage of\ud early miscarriages and fetal malformations was observed in females exposed to\ud oxidized SWCNTs, while lower percentages were found in animals exposed to the\ud pristine material. The lowest effective dose was 100 ng/mouse. Extensive vascular\ud lesions and increased production of reactive oxygen species (ROS) were detected\ud in placentas of malformed but not of normally developed fetuses. Increased ROS\ud levels were likewise detected in malformed fetuses. No increased ROS production\ud or evident morphological alterations were observed in maternal tissues. No fetal \ud and placental abnormalities were ever observed in control animals. In parallel,\ud SWCNT embryotoxicity was evaluated using the embryonic stem cell test (EST), a\ud validated in vitro assay developed for predicting embryotoxicity of soluble\ud chemical compounds, but never applied in full to nanoparticles. The EST predicted\ud the in vivo data, identifying oxidized SWCNTs as the more toxic compound

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A new carbon electrode material, obtained by mixing single wall carbon nanotubes (SWNTs) with a mineral oil binder is studied. Carbon nanotube pastes show the special properties of carbon nanotubes combined with the various advantages of composite electrodes such as a very low capacitance (background current) and the possibility of an easy preparation, modification and renewal. A better knowledge of the characteristics of electrode reactions at carbon nanotube paste (CNTP) electrodes was obtained studying the electron transfer rates of various redox couples under different pretreatment conditions. A critical comparison with carbon paste (CP), platinum (Pt) and glassy carbon (GC) electrodes was also carried out. Capacitance and resistance values were also calculated for all electrodes investigated. Both untreated and treated CNTP electrodes showed a low resistance while the capacitance was markedly reduced with CNTP electrodes previously treated with concentrated nitric acid. An electrochemical pretreatment on CNTP electrodes was developed which showed an excellent result towards two-electron quinonic structure species. After this treatment the heterogeneous standard rate constants for p-methylaminophenol sulfate (MAP) and dopamine resulted to be significantly higher (2.1 Â 10 À2 cm/s and 2.0 Â 10 À2 cm/s, respectively) than those obtained with the other electrodes studied. Reproducibility, stability and storage characteristics of CNTP electrodes were also reported.

Magnetic bio-hybrid porous scaffolds have been synthesized, nucleating nano-apatite in situ on self-assembling collagen, in the presence of magnetite nano-particles. The magnetic phase acted as a sort of cross-linking agent for the collagen, inducing a chemico-physical-mechanical stabilization of the material and allowing us to control the porosity network of the scaffold. Gradients of bio-mineralization and magnetization were also developed for osteochondral application. The good potentiality of the material as a biomedical device, able to offer assistance to bone regeneration through scaffold reloading with specific factors guided by an external magnetic field, has been preliminarily investigated. Up to now the proof of this concept has been realized through in vitro assessments.

Nanowires have received considerable attention owing to their broad potential applications. We report here on the application of nanowires for magnetic control of the electrochemical reactivity and demonstrate how one can modulate the electrocatalytic activity by orienting catalytic nanowires at different angles. Unlike early "on/off" magnetic switching studies based on functionalized magnetic spheres, the present magnetoswitchable protocol relies on modulating the electrochemical reactivity without removing the magnetic material from the surface. Such behavior is attributed to the reversible blocking of the redox processes and to changes in the tortuosity-dependent flux rate. The nanowire-based magnetoswitchable protocol may be extremely useful for adjusting the electrochemical reactivity, such as for tuning the power output of fuel cells (rather than switching the power on/off).