Visualizing Hg²⁺ ions in living cells using a FRET-based fluorescent sensor

A novel FRET fluorescent sensor for Hg²⁺ imaging in living cells is rationally designed based on a coumarin-rhodamine platform. RBC1 exhibit high selectivity and excellent sensitivity in both absorbance and fluorescence detection of Hg²⁺ in aqueous solution. After addition of increasing concentrations of Hg²⁺, it result in the decrease of coumarin emission at 467 nm and a new emission profile of rhodamine at 590 nm gradually increased. The response time to Hg²⁺ is less than 2 min, and other metal ions including Fe²⁺, Mn²⁺, Ni²⁺, Co ²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Pb ²⁺, and Cr³⁺ had no interference. In addition, fluorescent imaging of Hg²⁺ in A375 cells is also successfully demonstrated. The design strategy of two fluorophores switching in this work would help to extend the development of FRET fluorescent sensors.