PAMAM dendrimers functionalized with ruthenium nitrosyl as nitric oxide carriers

The functionalization of three generations of polyamidoamine (PAMAM G0, G2 and G3) dendrimers with the NO-donor trans-[Ru(NO)(NH3)4(ina)](BF4)3 (ina = isonicotinic acid) is reported. PAMAMs were modified through a peptide-type bond between the carboxyl group of the ina ligand and the dendrimer superficial amines. Compounds were characterized by FT-IR, UV–Vis, CV, DPV, 1H NMR, ICP-OES, and the structure of the complextrans-[Ru(NO)(NH3)4(ina)](BF4)(SiF6)·H2O was determined by single crystal X-Ray analysis. The experimental data indicated the immobilization of 4, ∼8 and ∼27 nitrosyl complexes on the G0, G2 and G3 dendrimer’s surface, respectively, which corresponds to ∼1.0–1.43 μmol NO per mg of dendrimer. FT-IR, UV–Vis and electrochemical assays suggest that the functionalization of PAMAM did not alter the coordination sphere of the ruthenium nitrosyl complex neither the formal reduction potential of RuIINO+/RuIINO0 couple regarding to the complex not attached to PAMAM. The NO release in these compounds, through light irradiation (λ = 355 nm) and one-electron reduction (Eu2+), was investigated.