Thermal and Chemical Stability of Diphenylalanine Peptide Nanotubes:  Implications for Nanotechnological Applications

Abstract

The diphenylalanine peptide, the core recognition motif of the beta-amyloid polypeptide, efficiently self-assembles into discrete, well-ordered nanotubes. Here, we describe the notable thermal and chemical stability of these tubular structures both in aqueous solution and under dry conditions. Scanning and transmission electron microscopy (SEM and TEM) as well as atomic force microscopy (AFM) revealed the stability of the nanotubes in aqueous solution at temperatures above the boiling point of water upon autoclave treatment. The nanotubes preserved their secondary structure at temperatures up to 90 degrees C, as shown by circular dichroism (CD) spectra. Cold field emission gun (CFEG) high-resolution scanning electron microscope (HRSEM) and thermogravimetric analysis (TGA) of the peptide nanotubes after dry heat revealed durability at higher temperature. It was shown that the thermal stability of diphenylalanine peptide nanotubes is significantly higher than that of a nonassembling dipeptide, dialanine. In addition to thermal stability, the peptide nanotubes were chemically stable in organic solvents such as ethanol, methanol, 2-propanol, acetone, and acetonitrile, as shown by SEM analysis. Moreover, the acetone environment enabled AFM imaging of the nanotubes in solution. The significant thermal and chemical stability of the peptide nanotubes demonstrated here points toward their possible use in conventional microelectronic and microelectromechanics processes and fabrication into functional nanotechnological devices.

Ostwald’s rule of stages governs structural transitions and morphology of dipeptide supramolecular polymers

“…The diphenylalanine (FF) structural motif and its derivatives are among the most widely studied minimal building blocks that allow the formation of ordered polymer-like assemblies at the nano-scale [17][18][19][20] . This class of molecular species exhibits effective self-assembly properties, and has been shown to generate a rich variety of ultrastructures, with functional physical and chemical properties, including piezoelectricity 21,22 , luminescence 23 and robust mechanical characteristics [24][25][26][27][28][29] . Moreover, it is becoming increasingly clear that the ability to control the structures of self-assembled peptides at interfaces has great potential for a multitude of future applications 30 .…”

Peptide Self-Assembled Nanostructures for Drug Delivery Applications

“…Many studies have been carried out to self-assemble FF dipeptides into different nanostructures including nanoparticles, nanotubes, nanovesicles, and nanowires, shown in Figure 2 [34,[38][39][40][41][42]. FF selfassembled nanotubes have been demonstrated to be thermally stable, which is one of the most unique properties for bioinspired materials [43]. The high yield of FF dipeptides self-assembled nanotubes was achieved through vapor deposition method, which could tune the density and length of nanotubes by controlling the monomer supply [38].…”

“…These solvents can make the -stacking more dominant than other self-assembly effects [40]. For the dipeptide FF self-assembly process, -stacking from the aromatic groups and hydrogen bonding stabilized the selfassembled FF nanostructures, which have been demonstrated for various applications including drug delivery [43,113].…”

Turbidity patterns of spontaneous peptidization in an aqueous abiotic system and possible secondary peptide structures

“…Moreover, the selected peptide structures tend to be viewed as fairly stable units (e.g., [8][9][10]), often with some negative health repercussions (e.g., as a cause of the age-related neurodegenerative diseases [10][11][12]) or to the contrary, they can be positively employed in various different biomedical nanotechnology contexts, owing to their biocompatibility (e.g., [10,13,14]). Numerous reports on the lack of peptide stability in abiotic solutions refer to their decomposition (e.g., hydrolysis) rather than to their spontaneous formation (the latter process being the leitmotif of this study) and they tend to ascribe such phenomena to the external stimuli such, as pH, temperature, chemical nature of solvents, etc.…”