Amphiphilic polypyridyl ruthenium complexes: Synthesis, characterization and aggregation studies

Organoplatinum(II) Complexes Self-Assemble and Recognize AT-Rich Duplex DNA Sequences

The specific recognition of AT-rich DNA sequences opens up the door to promising diagnostic and/or therapeutic strategies against gene-related diseases. Here, we demonstrate that amphiphilic Pt^II complexes of the type [Pt(dmba)(N∧N)]NO₃ (dmba = N,N-dimethylbenzylamine-κN, κC; N∧N = dpq (3), dppz (4), and dppn (5)) recognize AT-rich oligonucleotides over other types of DNA, RNA, and model proteins. The crystal structure of 4 shows the presence of significant π-stacking interactions and a distorted coordination sphere of the d⁸ Pt^II atom. Complex 5, containing the largest π-conjugated ligand, forms supramolecular assemblies at high concentrations under aqueous environment. However, its aggregation can be promoted in the presence of DNA at concentrations as low as 10 μM in a process that “turns on” its excimer emission around 600 nm. Viscometry, gel electrophoresis, and theoretical calculations demonstrate that 5 binds to minor groove when self-assembled, while the monomers of 3 and 4 intercalate into the DNA. The complexes also inhibit cancer cell growth with low-micromolar IC₅₀ values in 2D tissue culture and suppress tumor growth in 3D tumor spheroids with a multicellular resistance (MCR) index comparable to that of cisplatin.

Cyclometalated Pt^II complexes containing π-conjugated ligands form supramolecular assemblies under aqueous environment, and DNA-induced aggregation occurs for the one containing the highest conjugated N,N-diimine ligand. The complexes recognize AT-rich DNA sequences over others in DNA, RNA, and proteins. Their DNA binding mode switches from intercalation to minor groove binding when self-assembled. The complexes suppress tumor growth in 3D tumor spheroids.