Tag Archives: International School for Advanced Studies (SISSA)

The nanotube of a thousand faces (similar nanomaterials behaving differently)

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Kudos to any one who recognizes the reference to the ‘man of a thousand faces’, Lon Chaney, a silent film horror star. As for the nanotubes, there’s this Sept. 14, 2016 news item on ScienceDaily,

Nanotubes can be used for many things: electrical circuits, batteries, innovative fabrics and more. Scientists have noted, however, that nanotubes, whose structures appear similar, can actually exhibit different properties, with important consequences in their applications. Carbon nanotubes and boron nitride nanotubes, for example, while nearly indistinguishable in their structure, can be different when it comes to friction. A study conducted by SISSA/CNR-IOM and Tel Aviv University created computer models of these crystals and studied their characteristics in detail and observed differences related to the material’s chirality. …

A Sept. 14, 2016 Scuola Internazionale Superiore di Studi Avanzati (SISSA) press release (PDF), which originated the news item, describes the research in more detail,

“We began with a series of experimental observations which showed that very similar nanotubes exhibit different frictional properties, with intensities ranging up to two orders of magnitude,” says Roberto Guerra, a researcher at CNR-IOM and the International School for Advanced Studies (SISSA) in Trieste, first author of the study. “This led us to hypothesize that the chirality of the materials may play a role in this phenomenon.” The study involving also Andrea Vanossi (CNR-IOM) and Erio Tosatti (SISSA), was conducted in collaboration with the University of Tel Aviv.

For materials, such as those used in the study, chirality is linked to the three-dimensional arrangement of the weft that form the nanotube. “If we wrap a sheet of lined paper around itself to form a tube, the angle that the lines form with the axis of the tube determines its chirality,” says Guerra. “In our work we reconstructed the behavior of double-walled nanototubes, which can be imagined as two tubes of slightly different diameters, one inside the other. We observed that the difference in chirality between the inner tube and the outer tube has a remarkable effect on the three-dimensional shape of the nanotubes.”

A polygonal tube

“If we continue with the paper metaphor, the difference in orientation between the lattice on the inner tube and the outer tube determine to what extent, and, in what way, planar regions (faces) along the tube will form,” says Guerra. To better understand what is meant by “faces,” imagine a cross section of the tube, which is polygonal rather than perfectly circular. “The smaller the difference in chirality, the clearer and more obvious the faces,” concludes Guerra. If, however, the difference in chirality becomes too large, the faces disappear and the nanotubes take on the classic cylindrical shape.

The faces appear spontaneously depending on the characteristics of the material. Double-walled carbon nanotubes tend to form with a greater difference in internal and external chirality compared to boron nitride. Therefore, the former usually maintains a cylindrical shape that allows for less friction. In further studies, Guerra and colleagues intend to work directly on measuring the level of friction between nanotubes.

Here’s a link to and a citation for the paper,

Multiwalled nanotube faceting unravelled by Itai Leven, Roberto Guerra, Andrea Vanossi, Erio Tosatti, & Oded Hod. Nature Nanotechnology (2016) doi:10.1038/nnano.2016.151 Published online 22 August 2016

This paper is behind a paywall.

Calming a synapse (part of a neuron) with graphene flakes

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As we continue to colonize our own brains, there’s more news of graphene and neurons (see my Feb. 1, 2016 post featuring research from the same team in Italy featured in this post). A May 10, 2016 news item on ScienceDaily highlights work that could be used for epilepsy,

Innovative graphene technology to buffer the activity of synapses– this is the idea behind a recently-published study in the journal ACS Nano coordinated by the International School for Advanced Studies in Trieste (SISSA) and the University of Trieste. In particular, the study showed how effective graphene oxide flakes are at interfering with excitatory synapses, an effect that could prove useful in new treatments for diseases like epilepsy.

I guess the press release took a while to make its way through translation, here’s more from the April 10, 2016 SISSA (International School for Advanced Studies) press release (also on EurekAlert),

The laboratory of SISSA’s Laura Ballerini in collaboration with the University of Trieste, the University of Manchester and the University of Castilla -la Mancha, has discovered a new approach to modulating synapses. This methodology could be useful for treating diseases in which electrical nerve activity is altered. Ballerini and Maurizio Prato (University of Trieste) are the principal investigators of the project within the European flagship on graphene, a far-reaching 10-year international collaboration (one billion euros in funding) that studies innovative uses of the material.

Traditional treatments for neurological diseases generally include drugs that act on the brain or neurosurgery. Today however, graphene technology is showing promise for these types of applications, and is receiving increased attention from the scientific community. The method studied by Ballerini and colleagues uses “graphene nano-ribbons” (flakes) which buffer activity of synapses simply by being present.

“We administered aqueous solutions of graphene flakes to cultured neurons in ‘chronic’ exposure conditions, repeating the operation every day for a week. Analyzing functional neuronal electrical activity, we then traced the effect on synapses” says Rossana Rauti, SISSA researcher and first author of the study.

In the experiments, size of the flakes varied (10 microns or 80 nanometers) as well as the type of graphene: in one condition graphene was used, in another, graphene oxide. “The ‘buffering’ effect on synaptic activity happens only with smaller flakes of graphene oxide and not in other conditions,” says Ballerini. “The effect, in the system we tested, is selective for the excitatory synapses, while it is absent in inhibitory ones”

A Matter of Size

What is the origin of this selectivity? “We know that in principle graphene does not interact chemically with synapses in a significant way- its effect is likely due to the mere presence of synapses,” explains SISSA researcher and one of the study’s authors, Denis Scaini. “We do not yet have direct evidence, but our hypothesis is that there is a link with the sub-cellular organization of the synaptic space.”

A synapse is a contact point between one neuron and another where the nervous electrical signal “jumps” between a pre and post-synaptic unit. [emphasis mine] There is a small gap or discontinuity where the electrical signal is “translated” by a neurotransmitter and released by pre-synaptic termination into the extracellular space and reabsorbed by the postsynaptic space, to be translated again into an electrical signal. The access to this space varies depending on the type of synapses: “For the excitatory synapses, the structure’s organization allows higher exposure for the graphene flakes interaction, unlike inhibitory synapses, which are less physically accessible in this experimental model,” says Scaini.

Another clue that distance and size could be crucial in the process is found in the observation that graphene performs its function only in the oxidized form. “Normal graphene looks like a stretched and stiff sheet while graphene oxide appears crumpled, and thus possibly favoring interface with the synaptic space, ” adds Rauti.

Administering graphene flake solutions leaves the neurons alive and intact. For this reason the team thinks they could be used in biomedical applications for treating certain diseases. “We may imagine to target a drug by exploiting the apparent flakes’ selectivity for synapses, thus targeting directly the basic functional unit of neurons”concludes Ballerini.

That’s a nice description of neurons, synapses, and neurotransmitters.

Here’s a link to and a citation for the paper,

Graphene Oxide Nanosheets Reshape Synaptic Function in Cultured Brain Networks by Rossana Rauti, Neus Lozano, Veronica León, Denis Scaini†, Mattia Musto, Ilaria Rago, Francesco P. Ulloa Severino, Alessandra Fabbro, Loredana Casalis, Ester Vázquez, Kostas Kostarelos, Maurizio Prato, and Laura Ballerini. ACS Nano, 2016, 10 (4), pp 4459–4471
DOI: 10.1021/acsnano.6b00130 Publication Date (Web): March 31, 2016

Copyright © 2016 American Chemical Society

This paper is behind a paywall.