Aqueous Self-Assembly of Unsymmetric Peptide Bolaamphiphiles into Nanofibers with Hydrophilic Cores and Surfaces

Abstract

Unsymmetric peptide bolaamphiphiles that incorporate (l-glutamyl)3glycine at one terminus and either tetraethylene glycol or aspartic acid at the other were found to form hydrogels at low wt %, presumably by self-assembling into nanofibers presenting (l-glutamyl)3glycine at their surfaces and burying the second headgroup at their cores. Transmission electron microscopy measurements on 1 wt % gels negatively stained with phosphotungstic acid and positively stained with uranyl acetate show one-dimensional objects with diameters of 5 nm and lengths in excess of 1 mum. Circular dichroism and solid-state FTIR spectra indicate the adoption of beta-sheet structure within the nanofibers.

Supramolecular design of self-assembling nanofibers for cartilage regeneration

“…For cell encapsulation, cell suspensions were mixed with aqueous PA solutions (pH 7) and 20 μL aliquots of the PA/cell suspension were injected into 200 μL of MSC growth media (Lonza) supplemented with 25 mM calcium chloride to induce gelation (in a 96-well U-bottom plate). For differentiation studies, media was changed to a serum-free chondrogenic media containing high glucose DMEM (high glucose 4.5% without L-glutamine), 0.1 mM nonessential amino acids, 10 mM Hepes buffer, 100 U∕mL penicillin, 100 μg∕mL streptomycin gluta- [8][9][10]. Of note is the narrow distribution of scores for the defect groups treated with the 10% TGFBPA compared to the wider spread in scores for those treated with 100 ng∕mL rhTGF-β1 (100TGF) alone or filler PA þ 100TGF.…”

“…These molecules, targeted to serve as the components of artificial extracellular matrices, consists of a peptide segment covalently bonded to a more hydrophobic segment such as an alkyl tail (9)(10)(11)(12). PAs are normally charged molecules so that screening ions in the biological environment can trigger self-assembly into cylindrical nanofibers, which form by hydrogen bonding among peptide segments into β-sheets and the hydrophobic collapse of their alkyl segments (13).…”

Supramolecular Self-Assembly of Multiblock Copolymers in Aqueous Solution

“…Peptidebased materials have also been shown to form hydrogel networks in response to physical or chemical stimuli. [13][14][15][16][17] These materials utilize the primary modes of self-association in peptides, the hydrophobic aggregation of -strands and coiling of helices, to form long-range networks that lead to hydrogel formation. In this work, we have developed new synthetic block copolymers that respond to both pH and temperature, providing the ability to tune the nanoscale and macroscale structures formed using two independent environmental stimuli, giving rise to unique phase behavior and formation of dehydrated elastic solids by self-assembly that has not been seen in other systems.…”

Development of New Smart Materials and Spinning Systems Inspired by Natural Silks and Their Applications

“…Stupp's group described the use of a series of well-known diblock polymers, the peptide amphiphiles (PA), consisting of a peptide segment and a more hydrophobic alkyl tail that self-assemble to form supramolecular nanofibers in an aqueous solution (Hartgerink et al, 2001(Hartgerink et al, , 2002Claussen et al, 2003;Behanna et al, 2005;Shah et al, 2010). The silk GA domains were incorporated into the PAs to provide stability to the nanofibers by forming β-sheets in the fibers (Shah et al, 2010).…”