A rhodamine based fluorescent probe for Hg2+ and its application to cellular imaging

A new rhodamine-based fluorescent probe (Rh-F) for detection of Hg(2+) ions was synthesized, which could bind Hg(2+) in aqueous ethanol (7:3, v/v) at pH 7.0 with detectable change in color and fluorescence. The response is based on a ring opening reaction and formation of a 1:1 complex, while ring-opening process of spirolactam enables large fluorescent enhancement and colorimetric change upon the addition of Hg(2+). The response is reversible and linear in the range between 200nM and 1000nM, with a detection limit of 4.2nM. Selectivity and competition experiments with various other metal ion revealed that Rh-F possesses highly selective fluorescent response to Hg(2+). Furthermore, the probe was successfully applied to fluorescent imaging of Hg(2+) in L-929 cells confirm that Rh-F can be used as a fluorescent probe for monitoring Hg(2+) in living cells.