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.

Energy transfer between CdS nanocrystals and neodymium ions embedded in vitreous substrates.

Experimental evidence has been observed for energy transfer from CdS nanocrystals, synthesized by the fusion method, to Nd(3+) ions embedded in vitreous substrates. These dot samples doped with neodymium have been investigated by combined optical absorption (OA), photoluminescence (PL), and time-resolved photoluminescence (PLRT) techniques. Radiative and nonradiative energy transfers between CdS dot and Nd(3+) ion levels, to our knowledge not reported before, can be clearly observed in the PL spectra where the emission band valleys correspond exactly to the energy absorption peaks of the doping ion. The PLRT data reinforce these energy transfer mechanisms in which the increasing overlap between the CdS PL band and the OA to the Nd(3+) levels decreases stimulated emissions from the doping ions.