Scheme 5.

Integrin-targeting peptide coupling strategies for (A) soft nanoparticles such as liposomes and (B) solid polymer- or metal-based nanoparticles. The peptides are equipped with a conjugation residue that is optionally attached to a surface via a flexible linker or spacer. Anchoring to a surface is mediated by conjugated lipophilic moieties in the case of liposomal delivery system or by direct or indirect coupling in the case of solid nanoparticles. The box contains examples of chemical blocks used for this purpose.