Detecting zinc and cadmium with fura ratiometric probes

Abstract. Fluorescent probes such as fura-2 and its relatives mag-fura-2 and fura-2FF are used to detect changes in intracellular ions such as Ca2+ and Mg2+. However, they are sufficiently non-selective to record changes in other species such as Zn2+, Cd2+, Fe2+ and other transition metals. In the present study we have characterized the responses of these three dyes to Zn2+ and Cd2+, in a buffered salt solution using spectrofluorophotometry. Fura-2, mag-fura-2 and fura-2FF generally reacted to increasing concentrations of Zn2+ or Cd2+ with a shift in the excitation spectra. We found that for a given probe the Zn2+ and Cd2+ excitation spectra were broadly similar, but isosbestic and peak wavelengths were useful in distinguishing between the two metals.