Efficient DNA condensation induced by ruthenium(II) complexes of a bipyridine-functionalized molecular clip ligand

Complexes of the type [Ru(bxbg)(2) (N-N)](2+), where N-N denotes 2,2'-bipyridine (bpy) (1), 1,10-phenanthroline (phen) (2), dipyrido[3,2-d:2',3-f] quinoxaline (dpq) (3), and dipyrido[3,2-a:2',3'-c]phenazine (dppz) (4), incorporating bis(o-xylene)bipyridine-glycoluril (bxbg) as an ancillary "molecular clip" ligand, have been synthesized and characterized. These ruthenium(II) complexes of bis(o-xylene)bipyridine-glycoluril self-associate in water through specific molecular recognition processes to form polycationic arrays. These arrays containing electrostatic binders as well as intercalator ligands at micromolar doses rapidly condense free DNA into globular nanoparticles of various sizes. The DNA condensation induced by these complexes has been investigated by electrophoretic mobility assay, dynamic light scattering, and transmission electron microscopy. The cellular uptake of complex-DNA condensates and the low cytotoxicity of these complexes satisfy the requirements of a gene vector.