Comparing dendritic and self-assembly strategies to multivalency-RGD peptide-integrin interactions

This paper compares covalent and non-covalent approaches for the organisation of ligand arrays to bind integrins. In the covalent strategy, linear RGD peptides are conjugated to first and second generation dendrons, and using a fluorescence polarisation competition assay, the first generation compound is demonstrated to show the most effective integrin binding, with an EC50 of 125 mu M (375 mu M per peptide unit). As such, this dendritic compound is significantly more effective than a monovalent ligand, which does not bind integrin, even at concentrations as high as 1 mM. However, the second generation compound is significantly less effective, demonstrating that there is an optimum ligand density for multivalency in this case. In the non-covalent approach to multivalency, the same RGD peptide is functionalised with a hydrophobic C12 chain, giving rise to a lipopeptide which is demonstrated to be capable of self-assembly. This lipopeptide is capable of effective integrin binding at concentrations of 200 mu M. These results therefore demonstrate that covalent (dendritic) and non-covalent (micellar self-assembly) approaches have, in this case, comparable efficiency in terms of achieving multivalent organisation of a ligand array.