On the use of Europium (Eu) for designing new metal-based anticancer drugs

Europium oxide (Eu₂O₃) was used to evaluate the affinity of this rare earth element for interacting with double-stranded (ds) DNA molecules. To perform the study, we used single molecule force spectroscopy with optical tweezers and gel electrophoresis assays. Force spectroscopy experiments show that Eu₂O₃ presents a strong interaction with dsDNA, and the binding is independent on the ionic strength used in the surrounding environment. Among the main characteristics of the interaction, Eu₂O₃ tends to bind in a cooperative way, forming bound clusters of ∼ 3 molecules, and presents a high equilibrium association binding constant on the order of 10⁵ M^-1. In addition, gel electrophoresis confirm the weak electrostatic character of the interaction and explicit show that Eu₂O₃ does not interfere on drug intercalation into the double-helix. Such results demonstrate the potential of europium for interacting with nucleic acids and strongly suggest that this rare earth element may be considered for the design of new metal-based anticancer drugs in the future.