Peptide-amphiphile nanofibers: A versatile scaffold for the preparation of self-assembling materials

Abstract

Twelve derivatives of peptide-amphiphile molecules, designed to self-assemble into nanofibers, are described. The scope of amino acid selection and alkyl tail modification in the peptide-amphiphile molecules are investigated, yielding nanofibers varying in morphology, surface chemistry, and potential bioactivity. The results demonstrate the chemically versatile nature of this supramolecular system and its high potential for manufacturing nanomaterials. In addition, three different modes of self-assembly resulting in nanofibers are described, including pH control, divalent ion induction, and concentration. P reprogrammed noncovalent bonds, within and between molecules, build highly functional and dynamic structures in biology, which motivates our interest in self-assembly of synthetic systems. Over the past few decades a substantial amount of literature describing noncovalent self-assembly of nanostructures has accumulated (1-14). However, it is still difficult to design supramolecular structures, particularly if we want to start with designed molecules and form objects that measure between nanoscopic and macroscopic dimensions. Developing this ability will take us closer to the broad, bottom-up approach of selfassembly observed in biology.Our laboratory has studied over the past decade self-assembly of designed molecules into macromolecular structures of twodimensional (15, 16), one-dimensional (17, 18), and zerodimensional nature (19)(20)(21)(22). These self-assembled objects contain between 10 1 and 10 5 molecules and thus resemble synthetic and biological polymers in molar mass. The interactions that lead to the formation of these structures include chiral dipole-dipole interactions, -stacking, hydrogen bonds, nonspecific van der Waals interactions, hydrophobic forces, electrostatic interactions, and repulsive steric forces. All systems studied involved combinations of these forces that counterbalance the enormous translational and rotational entropic cost caused by polymolecular aggregation. In some cases the possibility of internally linking these self-assembled structures through covalent bonds has been explored (1,17,20,23). A cross-linking produces actual polymers whose various shapes and dimensionalities are controlled by self-assembly and are very different from the well-known ''beads-on-a-chain'' structures of traditional polymers.In our studies of self-assembling systems we also have explored self-organization at length scales much greater than those of the aggregates themselves, reaching into scales of microns, millimeters, and even centimeters. We also have been interested in functionalities that emerge from self-assembly at these largerlength scales. An interesting example was the layering and polar stacking of mushroom-shaped supramolecular structures each measuring about 5 nm. The stem-to-cap layers of these nanostructures result in centimeter-scale films that are spontaneously piezoelectric (24). The search for useful systems in the microscopic and macroscopic regime that take advantage of mole...

Self-Assembled Peptide Amphiphile Nanofibers and PEG Composite Hydrogels as Tunable ECM Mimetic Microenvironment

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Peptide hydrogel in vitro non‐inflammatory potential

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