Complexation of europium( iii ) with exopolysaccharides from a marine bacterium envisaged as luminescent probe in a theranostic approach
Résumé
Exopolysaccharide (EPS) derivatives, produced by Alteromonas infernus bacterium, showed anti-metastatic properties in osteosarcoma (bone tumor). These EPSs could be employed as new drug delivery
systems for therapeutic uses. They may represent a new class of ligands to be combined in a theranostic
approach with fluorescent metals, such as Eu(III), to serve as imaging probe. The goal of this work was to
investigate the feasibility of such coupling by time-resolved laser-induced fluorescence spectroscopy
(TRLFS). Since these EPSs are polyelectrolytes their conformation could affect the complexation properties.
Thus, viscosimetric measurements were performed as a function of their concentration as well as
the background electrolyte concentration. Polysaccharides conformation exhibited a lower hydrodynamic
volume for the highest ionic strengths. The resulting random-coiled conformation could affect the complexation
with metal for high concentration but no change was evidenced when increasing europium
concentration. Two sites of complexation of Eu(III) were evidenced by TRLFS in heparin, whereas only one
site was evidenced in two modified EPSs produced from Alteromonas infernus.