Abstract
There is an increasing need for biocompatible regeneration scaffolds for neuronal cell proliferation due to the complex processes involved in the regeneration of the neurites which often results in permanent nerve cell damage. The discovery of self-assembling peptides, which can form well-ordered structures, has opened a realm of opportunity for the design of tailored short peptide-based nanostructures, which can be used as scaffolds for neural cell regeneration. Self-assembling peptide-based nanostructures are attractive due to their chemical versatility, biological recognition abilities, tunable mechanical strength and biodegradability. Tryptophan and tyrosine, aromatic peptides are widely known for their redox properties and roles in neurotransmitter synthesis. Dityrosine cross-links play a crucial role in the stabilization of proteins, and their redox-active properties facilitate charge hopping to allow long-distance electron transportation in proteins. In this study, we have synthesized tryptophan and tyrosine dipeptide-based nanostructures, using solution phase self-assembly, and plasma enhanced chemical vapor deposition. Hybrid deposition techniques such as plasma enhanced chemical vapor deposition (PECVD) developed from traditional methods such as chemical vapor deposition increase the reactivity of the deposited species, and therefore allows the use of non-reactive monomers such as peptides and proteins. We have synthesized arrays of vertically oriented nanotubes using plasma enhanced chemical vapor deposition (PECVD) in order to create scaffolds for neural cell proliferation and differentiation. To elucidate the mechanisms of growth, and morphological changes, a variety of spectroscopic and microscopic and techniques such as Liquid chromatography mass spectroscopy, Fourier Transform Infrared spectroscopy, powder X-ray diffraction, circular dichroism, secondary electron microscopy and transmission electron microscopy were used to study the growth process. Our findings have shown that these peptide nanotubes are crystalline, have high aspect ratios and semiconductive behavior. In parallel, quantum chemical computational methods were utilized to study the mechanisms involved in the self-assembly of peptides. Using a biocompatible scaffold comprised of precursors could potentially lead to upregulation of neurotransmitters such as dopamine. Preliminary studies of the influence of the nanotubes on the fate of human and rat neuronal cells (PC12, SH-SY5Y and neural progenitor cells) indicate that the nanotubes promote cellular proliferation, and differentiation in the absence of growth factors. The aspect ratio of the nanotubes played an essential role in cellular interactions. Cellular metabolic activity assays, immunostaining, ELISA, and real-time polymerase chain reaction (qPCR) for gene expression were used to study the interaction of the neuronal cells on the synthesized peptide scaffolds. SEM and fluorescence confocal microscopy demonstrate the feasibility of nanotube scaffolds for enhanced adhesion and proliferation of rat and human neural cells (PC12, SH-SY5Y and NPCs). Preliminary ELISA and qPCR analysis demonstrate the upregulation in dopamine synthesis and genes involved in the dopamine expression and differentiation.