The use of graphene-based materials to engineer sophisticated biosensing interfaces that can adapt to the central nervous system requires a detailed understanding of how such materials behave in a biological context. Graphene's peculiar properties can cause various cellular changes, but the underlying mechanisms remain unclear. Here, we show that single-layer graphene increases neuronal firing by altering membrane-associated functions in cultured cells. Graphene tunes the distribution of extracellular ions at the interface with neurons, a key regulator of neuronal excitability. The resulting biophysical changes in the membrane include stronger potassium ion currents, with a shift in the fraction of neuronal firing phenotypes from adapting to tonically firing. By using experimental and theoretical approaches, we hypothesize that the graphene-ion interactions that are maximized when single-layer graphene is deposited on electrically insulating substrates are crucial to these effects.

Physicochemical modification of implantable electrode systems is recognized as a viable strategy to enhance tissue/electrode integration and electrode performance in situ. In this work, a bench-top electrochemical process to formulate anodized ITO films with altered roughness, thickness and conducting profiles was explored. In addition, the influence of these anodized films on SH-5YSY cell proliferation, viability and focal adhesion reinforcement indicated that anodized ITO film cytocompatibility can be altered by varying the anodization current density. Furthermore, an ITO anodized films formed with a current density of 0.4 mA cm-2 showed important primary neural cell survival and promotion of neural network activity.

During the last decades, neuroscientists have increasingly exploited a variety of artificial, de-novo synthesized materials with controlled nano-sized features. For instance, a renewed interest in the development of prostheses or neural interfaces was driven by the availability of novel nanomaterials that enabled the fabrication of implantable bioelectronics interfaces with reduced side effects and increased integration with the target biological tissue. The peculiar physical-chemical properties of nanomaterials have also contributed to the engineering of novel imaging devices toward sophisticated experimental settings, to smart fabricated scaffolds and microelectrodes, or other tools ultimately aimed at a better understanding of neural tissue functions. In this review, we focus on nanomaterials and specifically on carbon-based nanomaterials, such as carbon nanotubes (CNTs) and graphene. While these materials raise potential safety concerns, they represent a tremendous technological opportunity for the restoration of neuronal functions. We then describe nanotools such as nanowires and nano-modified MEA for high-performance electrophysiological recording and stimulation of neuronal electrical activity. We finally focus on the fabrication of three-dimensional synthetic nanostructures, used as substrates to interface biological cells and tissues in vitro and in vivo.

Carbon nanotube-based biomaterials critically contribute to the design of many prosthetic devices, with a particular impact in the development of bioelectronics components for novel neural interfaces. These nanomaterials combine excellent physical and chemical properties with peculiar nanostructured topography, thought to be crucial to their integration with neural tissue as long-term implants. The junction between carbon nanotubes and neural tissue can be particularly worthy of scientific attention and has been reported to significantly impact synapse construction in cultured neuronal networks. In this framework, the interaction of 2D carbon nanotube platforms with biological membranes is of paramount importance. Here we study carbon nanotube ability to interfere with lipid membrane structure and dynamics in cultured hippocampal neurons. While excluding that carbon nanotubes alter the homeostasis of neuronal membrane lipids, in particular cholesterol, we document in aged cultures an unprecedented functional integration between carbon nanotubes and the physiological maturation of the synaptic circuits.

Highlights d Two-thirds of principal cells in the hippocampal CA1 region express slow AMPA receptors d Slow AMPA receptors show reduced desensitization and stay active for up to half a second d Increased charge transfer allows single stimulations to trigger action potentials d Postsynaptic short-term potentiation has implications for computation and cognition

The increasing engineering of carbon‐based nanomaterials as components of neuroregenerative interfaces is motivated by their dimensional compatibility with subcellular compartments of excitable cells, such as axons and synapses. In neuroscience applications, carbon nanotubes (CNTs) have been used to improve electronic device performance by exploiting their physical properties. Besides, when manufactured to interface neuronal networks formation in vitro, CNT carpets have shown their unique ability to potentiate synaptic networks formation and function. Due to the low optical transparency of CNTs films, further developments of these materials in neural prosthesis fabrication or in implementing interfacing devices to be paired with in vivo imaging or in vitro optogenetic approaches are currently limited. In the present work, we exploit a new method to fabricate CNTs by growing them on a fused silica surface, which results in a transparent CNT‐based substrate (tCNTs). We show that tCNTs favor dissociated primary neurons network formation and function, an effect comparable to the one observed for their dark counterparts. We further adopt tCNTs to support the growth of intact or lesioned entorhinal–hippocampal complex organotypic cultures (EHCs). Through immunocytochemistry and electrophysiological field potential recordings, we show here that tCNTs platforms are suitable substrates for the growth of EHCs and we unmask their ability to significantly increase the signal synchronization and fiber sprouting between the cortex and the hippocampus with respect to Controls. tCNTs transparency and ability to enhance recovery of lesioned brain cultures, make them optimal candidates to implement implantable devices in regenerative medicine and tissue engineering.

SummaryGlutamate receptor ion channels such as the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor mediate the majority of fast excitatory neurotransmission in the vertebrate CNS. AMPA receptors canonically provide the fast, millisecond component of the synaptic current. However, we found that about two-thirds of principal cells in the mouse hippocampus express AMPA receptors that do not desensitize and stay active for up to half a second. These receptors are expressed at synapses with a sparse but flat spatial distribution. The resulting increase in charge transfer allows single connections to reliably trigger action potentials. Biophysical and pharmacological observations imply that slow AMPA receptors incorporate γ-8 and other auxiliary proteins, and their activation lengthens individual miniature synaptic currents. Synaptic connections harboring slow AMPARs should have unique roles in hippocampal function.

AMPA-type glutamate receptors (AMPARs) mediate fast excitatory neurotransmission, and the plastic modulation of their surface levels determines synaptic strength. AMPARs of different subunit compositions fulfill distinct roles in synaptic long-term potentiation (LTP) and depression (LTD) to enable learning. Largely unknown endocytic mechanisms mediate the subunit-selective regulation of the surface levels of GluA1-homomeric Ca 2+ -permeable (CP) versus heteromeric Ca 2+ -impermeable (CI) AMPARs. Here, we report that the Alzheimer’s disease risk factor CALM controls the surface levels of CP-AMPARs and thereby reciprocally regulates LTP and LTD in vivo to modulate learning. We show that CALM selectively facilitates the endocytosis of ubiquitinated CP-AMPARs via a mechanism that depends on ubiquitin recognition by its ANTH domain but is independent of clathrin. Our data identify CALM and related ANTH domain–containing proteins as the core endocytic machinery that determines the surface levels of CP-AMPARs to bidirectionally control synaptic plasticity and modulate learning in the mammalian brain.