Bicyclic RGD peptides enhance nerve growth in synthetic PEG-based Anisogels.

Nerve regeneration scaffolds often consist of soft hydrogels modified with extracellular matrix (ECM) proteins or fragments, as well as linear and cyclic peptides. One of the commonly used integrin-mediated cell adhesive peptide sequences is Arg-Gly-Asp (RGD). Despite its straightforward coupling mechanisms to artificial extracellular matrix (aECM) constructs, linear RGD peptides suffer from low stability towards degradation and lack integrin selectivity.

High-Affinity αβ-Integrin-Selective Bicyclic RGD Peptides Identified via Screening of Designed Random Libraries.

We report the identification of high-affinity and selectivity integrin αβ-binding bicyclic peptides via "designed random libraries", that is, the screening of libraries comprising the universal integrin-binding sequence Arg-Gly-Asp (RGD) in the first loop in combination with a randomized sequence (XXX) in the second loop. Screening of first-generation libraries for αβ-binding peptides yielded a triple-digit nanomolar bicyclic αβ-binder (RGDAYG, IC = 406 nM). Next-generation libraries were designed by partially varying the structure of the strongest first-generation lead inhibitor and screened for improved affinities and selectivities for this receptor.

Bicyclic RGD peptides with high integrin α β and α β affinity promote cell adhesion on elastin-like recombinamers.

Biomaterial design in tissue engineering aims to identify appropriate cellular microenvironments in which cells can grow and guide new tissue formation. Despite the large diversity of synthetic polymers available for regenerative medicine, most of them fail to fully match the functional properties of their native counterparts. In contrast, the few biological alternatives employed as biomaterials lack the versatility that chemical synthesis can offer.

Bicyclic RGD Peptides with Exquisite Selectivity for the Integrin αβ Receptor Using a "Random Design" Approach.

We describe the identification of bicyclic RGD peptides with high affinity and selectivity for integrin αβ via high-throughput screening of partially randomized libraries. Peptide libraries (672 different compounds) comprising the universal integrin-binding sequence Arg-Gly-Asp (RGD) in the first loop and a randomized sequence XXX (X being one of 18 canonical l-amino acids) in the second loop, both enclosed by either an l- or d-Cys residue, were converted to bicyclic peptides via reaction with 1,3,5-tris(bromomethyl)benzene (T3). Screening of first-generation libraries yielded lead bicyclic inhibitors displaying submicromolar affinities for integrin αβ (e.

High-Affinity RGD-Knottin Peptide as a New Tool for Rapid Evaluation of the Binding Strength of Unlabeled RGD-Peptides to αβ, αβ, and αβ Integrin Receptors.

We describe a highly sensitive competition ELISA to measure integrin-binding of RGD-peptides in high-throughput without using cells, ECM-proteins, or antibodies. The assay measures (nonlabeled) RGD-peptides' ability to inhibit binding of a biotinylated "knottin"-RGD peptide to surface-immobilized integrins and, thus, enables quantification of the binding strength of high-, medium-, and low-affinity RGD-binders. We introduced the biotinylated knottin-RGD peptide instead of biotinylated cyclo[RGDfK] (as reported by Piras et al.