Characterization of Peptide−Amphiphiles Possessing Cellular Activation Sequences

Abstract

Numerous approaches have been described for modifying biomaterials to incorporate extracellular matrix components. "Peptide-amphiphiles", whereby monoalkyl hydrocarbon chains are covalently linked to peptide sequences, have been shown previously to (a) form specific molecular architecture with enhanced stability and (b) promote cell adhesion, spreading, and signaling. The present study has examined the use of chimeric peptide-amphiphiles for inducing protein-like structures and peptide-amphiphile mixtures for enhancing surface bioactivity. The alpha-helical propensity of a 21 residue peptide, incorporating the SPARC(119-122) angiogenesis-inducing sequence and either unmodified or acylated with a C(6), C(10), C(14), C(16), C(18), C(18:1), or C(18:1-OH) monoalkyl hydrocarbon chain, has been examined. Peptide and peptide-amphiphile structures were characterized by circular dichroism and one- and two-dimensional NMR spectroscopic techniques. The 21 residue peptide alone does not form a distinct structure in solution, whereas N-terminal acylation by monoalkyl hydrocarbon chains results in the 21 residue peptide-amphiphile adopting a predominantly alpha-helical structure in solution. The thermal stability of the alpha-helix increases with increasing hydrocarbon chain length. The SPARC(119-122) peptide-amphiphiles were then screened for promotion of endothelial cell adhesion and spreading. The greatest activity was achieved by using a mixture of the alpha-helical SPARC(119-122) peptide-amphiphile, a triple-helical peptide-amphiphile incorporating the alpha2beta1 integrin binding site from type I collagen, and a pseudolipid. The pseudolipid is most likely required for a spatial distribution of the peptide-amphiphiles that allows for optimal cellular interactions. Overall, we have found that incorporation of bioactive sequences within peptide-amphiphiles results in the induction of an ordered structure of the bioactive sequence and that mixtures of peptide-amphiphiles can be used to promote endothelial cell behaviors comparable to extracellular matrix components.

Supramolecular nanostructures that mimic VEGF as a strategy for ischemic tissue repair

“…1F), evident by less change in the 220-nm α-helical CD signature upon heating. Conjugation to an alkyl tail is known to stabilize α-helical peptides (32) and supramolecular effects could also explain the increased thermal stability of the α-helical epitope when presented on the PA. Such stabilization of the bioactive conformation of the peptide by PA conjugation could enhance the potency of the epitope.…”

Differential Modulation of Human Melanoma Cell Metalloproteinase Expression by α2β1 Integrin and CD44 Triple-helical Ligands Derived from Type IV Collagen

“…This presumably leads to a multitude of signaling and regulatory pathways. One of the distinct advantages of the peptide amphiphile approach is that, initially, one receptor at a time can be studied, and then a "mini-ECM" can be assembled to examine the cumulative effects of multi-receptor binding (58,59). This will allow for the examination of cooperativity between the ␣ 2 ␤ 1 integrin and CD44/CSPG.…”

Induction of Endothelial Cell Activation by a Triple Helical α2β1 Integrin Ligand, Derived from Type I Collagen α1(I)496–507

“…To locate endothelial cell binding sites, a conservative library of type I collagen-derived triple helical sequences was screened for promotion of endothelial cell adhesion and spreading (24 -26). From this library, a triple helical peptide incorporating the human ␣1(I)496 -507 sequence (Gly-Ala-ArgGly-Glu-Arg-Gly-Phe-Hyp-Gly-Glu-Arg) was the most efficient at promoting endothelial cell binding and spreading (25). This peptide contains one of the ␣ 2 ␤ 1 integrin binding sites found in type I collagen (27)(28)(29).…”