Development of CNT Film Alignment and Geometries for Neuronal Attachment and Efficient Signal Transfer between Neurons and Electrodes

Abstract

Carbon nanotubes (CNTs) are widely used in neuroscience research for its excellent properties such as high conductivity, electrochemical stability, biocompatibility, mechanical compatibility with tissues, tunable mechanical and chemical properties. CNTs are investigating for its performance as neuronal scaffolds to support neural tissues, neuron growth and differentiation as well as neural stimulating and recording electrodes to control and monitor neural activity in both vitro and in vivo environments. Surprisingly neurons show a better interaction with CNTs when neurons are grown on CNT substrates. Previous research has shown neuronal differentiation on pristine CNT and CNT composites and the alignment of neurites on CNT substrates. Current research focus on interaction of neurons at the interface of pristine CNT films with aligned and cross hatch patterned CNT layers prepared from multi-walled CNT arrays. CNTs have nano scale surface roughness and contribution of alignment of CNTs can retain and adhere neurons without any adhesive proteins. As an initial step to study the interaction of neurons with CNT films, the effect of different CNT alignment on neuron adhesion and neurite development was chosen. PC12 cell line was used to study neuron adhesion and neurite alignment on CNT substrates. It is a commonly used neuronal cell model due to its ability to attain sympathetic neurons characteristics in the presence of nerve growth factor (NGF) in low serum medium. For the study, CNT films were prepared as aligned and in cross hatch pattern on PET sheets. After sterilization with UV irradiation, PC12 cells were seeded and cultured at a density of 20 000 cells/mL on CNT films and allowed to differentiate in NGF medium. For comparison poly l lysine (PLL) coated CNT films were used. Fig 1(Left) shows SEM image of a differentiating PC12 cell on PLL coated film of aligned CNTs and Fig 1(Right) shows SEM image of a differentiating PC12 cell on a crosshatch patterned CNT film with no adhesive coating. While neurites of PC12 cells align with the CNTs on aligned CNT film as states in the literature, pristine CNTs in crosshatch pattern were also able to hold the cells without any surface adhesive coating and allow differentiation of cells. Also PC12 cells tend to show random alignment on crosshatch patterned CNTs and adhere well due to higher degree of porosity and surface roughness. As pristine CNT films were able to hold PC12 cells, the interface properties will be further evaluated by impedance spectroscopy. Figure 1