Probing astroglia with carbon nanotubes: modulation of form and function

Abstract

0000-0003-2592-9898; VP, 0000-0002-4643-2197 Carbon nanotubes (CNTs) have shown much promise in neurobiology and biomedicine. Their structural stability and ease of chemical modification make them compatible for biological applications. In this review, we discuss the effects that chemically functionalized CNTs, applied as colloidal solutes or used as strata, have on the morpho-functional properties of astrocytes, the most abundant cells present in the brain, with an insight into the potential use of CNTs in neural prostheses. Carbon nanotubes as biocompatible materialCarbon nanotubes (CNTs) with their many desirable properties (size, strength, flexibility, conductivity, etc.) have shown much promise in biomedical applications, especially in neural prostheses. They are relatively inert and can be chemically modified using various functional groups depending on the application.CNTs are made up of a single sheet of graphene rolled into a cylinder. They can consist of a single cylinder of graphene, single-walled CNTs (SWCNTs), with diameters ranging from 0.4 to 2 nm, or of multiple coaxial cylinders, multi-walled CNTs (MWCNTs), with their outer diameters ranging from 2 to 100 nm and inner diameters ranging from 1 to 3 nm, and lengths ranging from 1 to several micrometres; these coaxial structures can also assume an intermediate form, i.e. double-walled CNTs. CNTs are produced using a variety of methods, including electric arc, laser ablation and chemical vapour deposition in the presence of catalysts, usually Fe, Ni, Co, Y or Mo, or their combinations (e.g. nickel and yttrium, typically, in approx. 4 : 1 weight ratio). Depending on the conformation of the carbon atoms in the graphene sheet, CNTs have three different configurations, which also dictate their conductivity: armchair, chiral or zigzag. All armchair CNTs are metallic, whereas chiral or zigzag CNTs can either be metallic or semiconducting (reviewed in [1,2]).To enhance the biocompatibility of the CNTs, as well as their dispersion in aqueous media, they can be modified via non-covalent or covalent attachment of molecules. A wide range of compounds such as DNA, proteins and lipids can be adsorbed onto the CNTs creating non-covalently functionalized CNTs. However, for a permanent attachment, the compounds have to be covalently linked to the CNTs. The most common way to do this is by incubating the CNTs with a strong oxidizing agent, e.g. nitric acid, which adds carboxyl groups to the ends of the CNTs or any defect sites. To obtain CNTs linked to other compounds, this carboxyl group can be converted to an acyl chloride intermediate, which can then be reacted with the compound of interest, for example, polyethylene glycol (PEG) or poly-m-aminobenzene sulfonic (PABS) acid (reviewed in [3]). Astroglia: the homeostatic scaffold of the central nervous systemAstroglia are a highly heterogeneous population of cells of ectodermal (i.e. neural) origin that provide for homeostasis in the central nervous system (CNS) [4]. In the & 2014 The Author(s) Published by the ...

A Nanoscale Interface Promoting Molecular and Functional Differentiation of Neural Cells

“…It has been shown that functionalized single-walled carbon nanotube films induce morphological and functional changes such as increased glutamate uptake in mouse cortical astrocytes 28 29 67 . Moreover, it has been recently discovered that nano-roughness of silica films can modulate the function of hippocampal neurons and their relationship with astrocytes via mechanical stimuli 31 .…”

Chemically Functionalized Water-Soluble Single-Walled Carbon Nanotubes Obstruct Vesicular/Plasmalemmal Recycling in Astrocytes Down-Stream of Calcium Ions

“…Single-walled carbon nanotubes (SWCNTs) have been considered candidates for applications in biotechnology and biomedicine [ 1 , 2 ], and in particular for neural applications [ 3 , 4 ]. When chemically functionalized with polyethylene glycol (PEG), SWCNTs render water solubility [ 5 ].…”

Effects of Chemically-Functionalized Single-Walled Carbon Nanotubes on the Morphology and Vitality of D54MG Human Glioblastoma Cells

“…Our present work logically sprouts from our previous studies of the effect that SWCNTs have on primary astrocytes, as reviewed elsewhere [15]. Briefly, to investigate the effects of SWCNTs on primary mouse astrocytes in culture, we used graft copolymers/conjugates of SWCNTs chemically functionalized with polyethylene glycol (PEG) or poly-m-aminobenzene sulfonic acid (PABS) making SWCNTs water soluble (wsSWCNTs) [16,17].…”

“…When added to the culturing medium, wsSWCNTs were able to make astrocytes larger and less round compared to the untreated astrocytes, but these nanomaterials did not affect astrocyte vitality, that is, cell adhesion, proliferation and death rate [17]. Generally, the data indicated the necessity of the SWCNT backbone for the changes induced by the water-soluble graft copolymers, while some subtle differences in the effects that SWCNTs had on astrocytes (for clarity details omitted here, but summarized and reviewed in [15] and Table 1 of [17]; also see discussion) were due to the various functional groups attached to the SWCNTs.…”