Peptide Nanotube Arrays as a Substrate for Electrical and Physical Stimulation for Neural Cell Differentiation

Tryptophan and tyrosine, aromatic peptides, are widely known for their redox properties and roles in neurotransmitter synthesis. Redox-active properties of tyrosine and tryptophan facilitate charge hopping to allow long-distance electron transportation in proteins. Self-assembling peptide-based nanostructures are attractive due to their chemical versatility, biological recognition abilities, tunable mechanical strength and biodegradability. In this study, we have synthesized nanotubes composed of various dipeptides such as tryptophan-tyrosine, phenylalanine-tyrosine and dityrosine peptides, using solution phase self-assembly and plasma enhanced chemical vapor deposition (PECVD). These were characterized using various chemical, mechanical, morphological, and thermal characterization techniques such as FTIR & Raman spectroscopy, and Liquid chromatography mass spectroscopy, nuclear magnetic resonance, powder X-ray diffraction and circular dichroism, and scanning electron microscopy (SEM).
There is an increasing need for biocompatible neuronal cell proliferation and regeneration scaffolds as regeneration of the neurite structures is slow and complex, which results in permanent nerve cell damage. In recent years, there has been growing interest in nanotube arrays and electrical stimulation in neural cell regeneration, however, there has still yet to be an approach that combines these two techniques for simultaneous physical and electrical stimulation. Our hypothesis is a biocompatible, semi-conductive scaffold of peptide nanotubes deposited via PECVD can contribute to upregulation of neurotransmitters such as dopamine could aid neuronal regeneration. After the analysis of physicochemical properties of these peptide nanostructures, we studied the biological interactions and influence these scaffolds had human neuroblastoma cells and neural progenitor cells. To test the same, MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) cytotoxicity studies, morphological cellular interaction imaging through SEM and confocal imaging, dopamine-enzyme linked immunosorbent assay, immunostaining for neuronal marker, and real-time polymerase chain reaction (q-PCR) for gene expression were carried out after the electrical stimulation and subsequent differentiation of neuronal cells on the synthesized peptide bioscaffolds.