Schematic diagram of an oligonucleotide cluster agent. Oligonucleotides are covalently conjugated to generation 3 dendrimers with specific functional groups. Complementary oligonucleotides are coupled to a core generation 5 dendrimer. Different units are then combined in physiologic conditions and aggregate into a device. Oligonucleotides are designed to assure the specificity of the hybridization and the stability of the duplex at physiologic conditions.