Inorganic mercury detection and controlled release of chelating agents from ion-responsive liposomes

A liposome system that can detect and detoxify mercury in aqueous solution is demonstrated. The system consists of 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine and 20% PEG-PE (PEG MW 2000 Da) that forms liposome, which encapsulates self-quenching fluorescein for detection, and chelating agent meso-2,3-dimercaptosuccinic acid (meso-DMSA) for chelating detoxification through Hg(2+)-responsive release of fluorescein and meso-DMSA. This system can detect mercury levels as low as 10 nM with high selectivity. In particular, the release profile of meso-DMSA by the local concentration of Hg can be modulated, so that more chelators are released in regions of high concentration and less chelators are released in regions of low concentration. The design has been demonstrated both in vitro and in HeLa cells. This "budgeted" release profile is particularly useful in situations in which the local levels of Hg contamination vary, or if such contamination is time dependent.