Abstract
The influence of electrical stimulation on neural cell activity is a fast-developing area of research. Non-invasive electrical stimulation could potentially enhance neural cell proliferation, and neuronal differentiation. Additionally, the ability to stimulate individual neurons may have a potential impact on the development of neural networks, and enhanced motor rehabilitation. Lastly, interfacing cells with biocompatible materials with electrical properties could be harnessed to introduce potential gradients across the cell membrane for neurological activation and repairs. In this project, we are studying the influence of voltage stimulation on neural cells in vitro using a high-density array of short peptide nanotubes deposited via vapor deposition. The peptide-based building blocks self-assemble to form highly organized nanoscale structures with key functional properties such as biocompatibility, high aspect ratios, semi-conductivity, and stiffness to be used as cell-scaffolding in this study. Prior studies have used carbon nanotubes scaffolds for the electrical stimulation, but their cytotoxicity makes their use in many biological systems undesirable. Peptide nanotubes are biocompatible and can be self-assembled using simple chemical techniques. Plasma enhanced chemical vapor deposition was used to produce a uniform array of vertically oriented nanotubes. The dipeptides that were used to create this scaffolding are dityrosine and tryptophan-tyrosine. These dipeptides undergo sublimation at their glass-transition temperature under vacuum, and argon gas plasma facilitates their formation into hollow tubes. Tryptophan and tyrosine are aromatic amino acids known to mediate electron transfer in proteins and form semiconductive nanotubes. In order to study the influence of electrical voltage stimulation on cell growth, we used PC-12 cells derived from rat adrenal medulla and SH-SY5Y neuroblastoma cells. The results of electrical stimulation of the cells at 1V for 2 hours daily for 5 days include increased growth cones and increased length of neurites. Preliminary analysis indicate that the cells cultured on tryptophan-tyrosine dipeptide nanotube scaffolds followed by electrical stimulation had an increased viability compared to control cells cultured on glass coverslips.