Development and biological characterization of the cyclic peptide cRGDTFI with potent binding affinity for integrins αvβ3 and αvβ5

Abstract

The arginine-glycine-aspartic acid (RGD) sequence is a motif that binds to integrins. RGD-containing peptides have applications in cancer treatment, tissue engineering, drug delivery, and imaging. The potent RGD-containing peptides cilengitide (cRGDfMeV) and iRGD (cCRGDKGDPC) show strong affinity for αvβ3- and αvβ5. Although both integrins contribute to the biological activities of these RGD-containing peptides, several studies have highlighted that αvβ5 plays a critical role in mediating specific therapeutic effects. Therefore, αvβ5 represents a promising target for therapeutic and diagnostic applications. Considering that the previously identified RGDTF motif has a high affinity for αvβ5, this study aimed to enhance αvβ5 affinity of RGDTF by designing cyclic RGDTF-containing peptides. Accordingly, a thioether cyclic peptide (cRGDTFI) was successfully developed. The cRGDTFI peptide exhibited stronger inhibitory activity than that of cilengitide against αvβ5-mediated HeLa cell adhesion in solution. Conformational analysis and molecular docking revealed that cRGDTFI fit well with αvβ5. When immobilized on a matrix, cRGDTFI promoted strong cell adhesion. In addition, cRGDTFI showed efficient cell internalization and in vitro blood–brain barrier permeability with a fluorescent payload. Overall, these results suggest that cRGDTFI is a versatile integrin-targeting ligand with potential applications in cancer treatment, cell culture, tissue engineering, drug delivery, and imaging.

Keywords

• Cyclic peptide
• RGD motif
• Integrin
• Cell adhesion