Previously designed cyclic peptide antagonist c[YYDEGLEE]-NH₂ disrupts the interaction between vascular endothelial growth factor (VEGF) and its receptors (VEGFRs). It represents a promising tool in the fight against cancer and age-related macular degeneration. We described in this paper the optimization of the lead peptide by C-terminal modification. A new strategy for the synthesis of cyclic peptides is developed, improving the cyclisation efficiency. At 100 µM, several new peptides with an aromatic group flexibly linked at C-terminal end showed significantly increased receptor binding affinities in competition ELISA test. The most active peptide carrying a coumarin group may be a useful tool in anti-angiogenic biological studies.

The use of functionalized magnetic particles is increasing because they simplify the analytical process and yield promising results in a wide range of applications. Particularly, streptavidin-coated magnetic beads offer the possibility of rapid and very efficient grafting of biomolecules. Unfortunately, current methods to monitor and compute this grafting process are cumbersome and scarce. We describe herein a simple, rapid and reliable chemiluminescent assay we have developed to check the grafting rate of functionalized magnetic beads. The power of the assay also relies on its ability to predict the amount of ligands required to obtain a precise grafting rate. In addition, results were correlated with a more general parameter in material functionalization characterization like surface ligand density. Finally, the assay was validated for a wide variety of biotinylated biomolecule sizes, ranging from small molecules (around 200 Da) to antibodies (around 150 kDa). This approach will allow a precise quantification and prediction of the functionalization of magnetic particles that is of enormous importance for quality control in many applications.