Interfacing neurons with carbon nanotubes: electrical signal transfer and synaptic stimulation in cultured brain circuits

The unique properties of single-wall carbon nanotubes (SWNTs) and the application of nanotechnology to the nervous system may have a tremendous impact in the future developments of microsystems for neural prosthetics as well as immediate benefits for basic research. Despite increasing interest in neuroscience nanotechnologies, little is known about the electrical interactions between nanomaterials and neurons. We developed an integrated SWNT-neuron system to test whether electrical stimulation delivered via SWNT can induce neuronal signaling. To that aim, hippocampal cells were grown on pure SWNT substrates and patch clamped. We compared neuronal responses to voltage steps delivered either via conductive SWNT substrates or via the patch pipette. Our experimental results, supported by mathematical models to describe the electrical interactions occurring in SWNT-neuron hybrid systems, clearly indicate that SWNTs can directly stimulate brain circuit activity.

Substrate arrays of iridium oxide microelectrodes for in vitro neuronal interfacing

Shady Didier Gawad, Michele Giugliano, Marc Olivier Heuschkel, Henry Markram, Hywel Morgan, Philippe Renaud

The design of novel bidirectional interfaces for in vivo and in vitro nervous systems is an important step towards future functional neuroprosthetics. Small electrodes, structures and devices are necessary to achieve high-resolution and target-selectivity during stimulation and recording of neuronal networks, while significant charge transfer and large signal-to-noise ratio are required for accurate time resolution. In addition, the physical properties of the interface should remain stable across time, especially when chronic in vivo applications or in vitro long-term studies are considered, unless a procedure to actively compensate for degradation is provided. In this short report, we describe the use and fabrication of arrays of 120 planar microelectrodes (MEAs) of sputtered Iridium Oxide (IrOx). The effective surface area of individual microelectrodes is significantly increased using electrochemical activation, a procedure that may also be employed to restore the properties of the electrodes as required. The electrode activation results in a very low interface impedance, especially in the lower frequency domain, which was characterized by impedance spectroscopy. The increase in the roughness of the microelectrodes surface was imaged using digital holographic microscopy and electron microscopy. Aging of the activated electrodes was also investigated, comparing storage in saline with storage in air. Demonstration of concept was achieved by recording multiple single-unit spike activity in acute brain slice preparations of rat neocortex. Data suggests that extracellular recording of action potentials can be achieved with planar IrOx MEAs with good signal-to-noise ratios.

2009

Impact of Carbon-Nanotube Substrate Coating in Neuronal Networks

Luca Gambazzi

The interest in new materials and their application in the neuroscience are growing incredibly fast. Current research interests are increasingly focusing on new artificial materials and their direct effects on the central nervous systems so that it would be possible use them to restore the original nervous function lost due to neuronal diseases or trauma. This thesis is part of the international Neuronano project and has been funded by the European Commission 6th Framework Programme. The main goal is to understand the interactions of carbon nanotubes (CNT) with the nervous tissues. Not only it focuses on how neuron stimulations and recordings instruments may be ameliorated by a CNT-neuron interface, but it also focuses on the endogenous effects of those artificial materials on neuronal activity. This thesis is divided into four themes: First, an integrated CNT-neuron system was developed to test whether electrical voltage stimulation, delivered via nanotubes, can induce neuronal signaling. It was also compared to neuronal responses evoked by voltage steps delivered via conventional patch-pipette. In the second part, the focus was on understanding the CNT-neuron interface and the tight contacts with the cell membranes that might favour electrical shortcuts between neuronal compartments. The third part is an overview of the effects of a CNT coated substrates when employed to grow long-term cell cultures. The activity was constantly monitored by an extracellular array of electrodes (MEA) for several weeks. The intimate relationship between nanotubes and cell membrane observed at single-neuron and network level, results in a more robust network activity. Finally, the MEA setup developed for cell cultures monitoring was used to investigate the effects of of BDNF on cortical cell culture model of Huntington disease.

EPFL2010

A conditional GABAergic synaptic vesicle marker for Drosophila

Brian Donal McCabe

Background: Throughout the animal kingdom, GABA is the principal inhibitory neurotransmitter of the nervous system. It is essential for maintaining the homeostatic balance between excitation and inhibition required for the brain to operate normally. Identification of GABAergic neurons and their GABA release sites are thus essential for understanding how the brain regulates the excitability of neurons and the activity of neural circuits responsible for numerous aspects of brain function including information processing, locomotion, learning, memory, and synaptic plasticity, among others. New method: Since the structure and features of GABA synapses are critical to understanding their function within specific neural circuits of interest, here we developed and characterized a conditional marker of GABAergic synaptic vesicles for Drosophila, 9XV5-vGAT. Results: 9XV5-vGAT is validated for conditionality of expression, specificity for localization to synaptic vesicles, specificity for expression in GABAergic neurons, and functionality. Its utility for GABAergic neurotransmitter phenotyping and identification of GABA release sites was verified for ellipsoid body neurons of the central complex. In combination with previously reported conditional SV markers for acetylcholine and glutamate, 9XV5-vGAT was used to demonstrate fast neurotransmitter phenotyping of subesophageal ganglion neurons. Comparison with existing methods: This method is an alternative to single cell transcriptomics for neurotransmitter phenotyping and can be applied to any neurons of interest represented by a binary transcription system driver. Conclusion: A conditional GABAergic synaptic vesicle marker has been developed and validated for GABA neurotransmitter phenotyping and subcellular localization of GABAergic synaptic vesicles.

2022