Collagen Mimetics Research Articles

Peptoid‐containing collagen mimetics with cell binding activity

Collagen mimetic peptides containing the peptoid residue Nleu (Goodman Bhumralkar, Jefferson, Kwak, Locardi. Biopolymers 1998;47:127–142) were tested for interactions with epithelial cells and fibroblasts. Molecules containing the sequence Gly-Pro-Nleu with a minimum of nine repeats showed cell binding activity. The activity of these molecules appeared to be conformationally sensitive, with the triple-helical form being preferred. When immobilized on a surface, the (Gly-Pro-Nleu)10-Gly-Pro-NH2 sequence stimulated the attachment and growth of corneal epithelial cells and fibroblasts and the migration of epithelial tissue. The peptide sequence KDGEA inhibited cell attachment to the (Gly-Pro-Nleu)10-Gly-Pro-NH2 sequence, suggesting that cell binding to this collagen mimetic involves the α2β1 heterodimer integrin receptor. Interestingly, peptides containing the sequence (GlyNleu-Pro-)10-NH2 did not have cell binding activity. The discovery that triple-helical peptides containing the Gly-Pro-Nleu sequences interact with cells opens up new opportunities in the design of collagen mimetic biomaterials. © 2000 John Wiley & Sons, Inc. J Biomed Mater Res, 51, 612–624, 2000.

Peptoid-containing collagen mimetics with cell binding activity

Collagen mimetic peptides containing the peptoid residue Nleu (Goodman Bhumralkar, Jefferson, Kwak, Locardi. Biopolymers 1998;47:127-142) were tested for interactions with epithelial cells and fibroblasts. Molecules containing the sequence Gly-Pro-Nleu with a minimum of nine repeats showed cell binding activity. The activity of these molecules appeared to be conformationally sensitive, with the triple-helical form being preferred. When immobilized on a surface, the (Gly-Pro-Nleu)(10)-Gly-Pro-NH(2) sequence stimulated the attachment and growth of corneal epithelial cells and fibroblasts and the migration of epithelial tissue. The peptide sequence KDGEA inhibited cell attachment to the (Gly-Pro-Nleu)(10)-Gly-Pro-NH(2) sequence, suggesting that cell binding to this collagen mimetic involves the alpha2beta1 heterodimer integrin receptor. Interestingly, peptides containing the sequence (GlyNleu-Pro-)(10)-NH(2) did not have cell binding activity. The discovery that triple-helical peptides containing the Gly-Pro-Nleu sequences interact with cells opens up new opportunities in the design of collagen mimetic biomaterials.

Design, synthesis and conformations of novel triple helical collagen mimetic structures

We have synthesized collagen-like monodisperse structures. A series of single chain Ac-(Gly-Pro-Hyp) n -NH2 wheren=1, 3, 5, 6, 9 and template-assembled KTA-[Gly-(Gly-Pro-Hyp) n -NH2]3 analogs (n=1, 3, 5, 6), where KTA is the Kemp triacid (cis-1,3,5-trimethyl cyclohexane-1,3,5-tricarboxylic acid), were assessed for triple helicity by CD, thermal denaturation and NMR spectroscopy. The KTA-based template induces a significant gain in free energy and reduces the critical chain length for triple helix formation over the acyl terminated single chain structures. Our approach also includes the incorporation of the peptoid residueN-isobutylglycine into the design for novel collagen-like sequences. We have synthesized and characterized acetylated single chain and template-assembled analogs composed of Gly-Pro-Nleu and Gly-Nleu-Pro sequences. The achiral trimeric unit Gly-Nleu-Nleu was included as a guest sequence in a host structure such as Ac-(Gly-Pro-Hyp)3-(Gly-Nleu-Nleu)3-(Gly-Pro-Hyp)3-NH2 which retains triple helicity. A series of guest-host collagen mimetics composed of Gly-Nleu-Pro sequences as the host were synthesized and assessed for triple helicity. Guest sequences include Gly-Nleu-Nleu and Gly-Nx-Pro units, where Nx is the guest peptoid residue with alkyl and aralkyl side chains. We have continued to investigate functionalized template motifs and sequence variations. We are examining the effects of functionalization and sequence variation on triple helical stabilities and molecular properties in order to design novel collagen-based biomaterials.

Triple Helical Stabilities of Guest–Host Collagen Mimetic Structures

The peptoid Nleu (N-isobutylglycine) has been successfully incorporated into a series of collagen mimetics composed of Gly-Pro-Nleu and Gly-Nleu-Pro sequences and has been able to maintain triple helices in appropriate structures. The achiral trimeric sequence Gly-Nleu-Nleu as a guest sequence in structures such as Ac-(Gly-Pro-Hyp)3-(Gly-Nleu-Nleu)3-(Gly-Pro-Hyp)3-NH2 retains triple helicity. As an extension of this study, we report, in this paper, on a series of guest–host collagen mimetic structures in which Gly-Nleu-Pro sequences are employed as the host. The guest sequences for these guest–host structures include Gly-Nleu-Nleu and Gly-Nx-Pro sequences where Nx is composed of a variety of alkyl and aralkyl peptoid residues. From these guest–host collagen mimetic structures, we are able to elucidate the contributions of hydrophobic and steric effects on triple helix formation. The Gly-Nleu-Pro sequences have been shown to be effective in inducing triple helicity. Conformational characterization of the guest–host collagen mimetic structures was established by techniques such as temperature-dependent optical rotation measurements and circular dichroism (CD) spectroscopy.

Incorporation of Achiral Peptoid-Based Trimeric Sequences into Collagen Mimetics

This report represents initial studies of collagen mimetics with achiral peptoid-based trimeric sequences. The incorporation of achiral units into collagen-like structures is of considerable interest for the structural simplification of collagen-like biomaterials. The achiral unit Gly-Nleu-Nleu (where Nleu represents N-isobutylglycine) was positioned between Gly-Pro-Hyp trimeric repeats in collagen-like structures in order to examine the effect of an achiral block on triple helicity. A series of single chain structures, Ac-(Gly-Pro-Hyp)n-(Gly-Nleu-Nleu)n-(Gly-Pro-Hyp)n-NH2 (where n = 1−3), and a template-assembled structure, KTA-[Gly-(Gly-Pro-Hyp)2-(Gly-Nleu-Nleu)2-(Gly-Pro-Hyp)2-NH2]3 (where KTA represents cis,cis-1,3,5-trimethylcyclohexane-1,3,5-tricarboxylic acid), were investigated. Biophysical studies were carried out in both H2O and ethylene glycol (EG)/H2O (2:1, v/v) solvents, using circular dichroism and optical rotation measurements. Highly cooperative melting curves from optical rotation determi...

Collagen mimetics.

Collagen peptidomimetics have been synthesized as an alternative to natural collagen. The incorporation of unnatural residues such as peptoids in the collagen sequences can demonstrate potent and specific biological activity and enhance the biostability against enzymatic degradation. Furthermore, the use of achiral peptoids simplifies synthetic strategies by reducing racemization problems. The peptoid residue N-isobutylglycine (Nleu) has been successfully incorporated into a series of collagen mimetics composed of Gly-Pro-Nleu, Gly-Nleu-Pro, and Gly-Nleu-Nleu. The discovery of template-assembled collagen mimetics and metal binding ability has laid the foundation for new opportunities in the design of novel collagen mimetic complexes. The review summarizes the synthesis and integrated biophysical analyses of the structures of these collagen mimetics. Solid phase segment condensation techniques have been utilized for the synthesis of the single chain and template-assembled analogues. The characterization of the collagen-like structures has been established by temperature-dependent optical rotation measurements. CD, NMR spectroscopy, and molecular modelling simulations.