Probing astroglia with carbon nanotubes: modulation of form and function

Abstract

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.

Keywords: astrocytes; carbon nanotubes; glial fibrillary acidic protein; graft copolymers; morphology; proliferation.

Figure 1.

The experimental set-up for the use of solute and film modalities of SWCNT-PEG on astrocytes. (a) Schematic of the SWCNT-PEG graft polymer structure (left), a vial containing SWCNT-PEG colloidal solute at a stock concentration of 2 mg ml⁻¹ (middle) and an image of a glass coverslip (12 mm in diameter) top-coated with 60 nm thick SWCNT-PEG film (right). (b) Scheme to represent the experimental set-up with astrocytes plated onto PEI-coated coverslips in the absence (left) or the presence of SWCNT-PEG colloidal solute (middle) or onto the SWCNT-PEG film (right). Drawings are not to scale. Chemical structure and images in (a) are reproduced (left–right) from Gottipati et al. [12], Lee & Parpura [18] and Malarkey et al. [19], respectively. (Online version in colour.)

Figure 2.

Example images of astrocytes showing the effects induced by the solute and film modalities of SWCNT-PEG on their morphology and GFAP-ir. (a) Images of astrocytes in culture plated onto the PEI-coated coverslips in the absence and the presence of 5 µg ml⁻¹ SWCNT-PEG solute and onto the 60 nm thick SWCNT-PEG film, loaded with calcein, a vital fluorescent dye. (b) Images of astrocytes plated in matching conditions as above and labelled for GFAP using indirect immunocytochemistry. Grey scale is a linear representation of the fluorescence intensities of the pixels in the images, expressed in fluorescence intensity units (i.u.). Scale bar, 20 μm. Adapted from [12,20].

Figure 3.

Example images of astrocytes showing the effects induced by the SWCNT-PEG films on their adhesion and proliferation. Images of astrocytic nuclei labelled with Hoechst 33342, a cell permeable nuclear dye (left column), and the corresponding astrocytes loaded with calcein, a vital fluorescent dye (middle column). Right column shows the merge of the images. (top set) The top two rows show images of astrocytes plated onto the PEI-coated coverslips and onto the 60 nm thick CNT films, respectively, 4 h post-plating and assessing cell adhesion. (bottom set) The bottom two rows show images of astrocytes plated in matching conditions as above, but imaged at the later time point, 4 days post-plating, and assessing cell proliferation. Scale bar, 50 μm. Reproduced from [20]. (Online version in colour.)