Dual-Analyte Fluorescent Sensor Based on [5]Helicene Derivative with Super Large Stokes Shift for the Selective Determinations of Cu or Zn in Buffer Solutions and Its Application in a Living Cell.

A new fluorescent sensor, M201-DPA, based on [5]helicene derivative was utilized as dual-analyte sensor for determination of Cu or Zn in different media and different emission wavelengths. The sensor could provide selective and bifunctional determination of Cu in HEPES buffer containing Triton-X100 and Zn in Tris buffer/methanol without interference from each other and other ions. In HEPES buffer, M201-DPA demonstrated the selective ON-OFF fluorescence quenching at 524 nm toward Cu. On the other hand, in Tris buffer/methanol, M201-DPA showed the selective OFF-ON fluorescence enhancement upon the addition of Zn, which was specified by the hypsochromic shift at 448 nm. Additionally, M201-DPA showed extremely large Stokes shifts up to ∼150 nm. By controlling the concentration of Zn and Cu in a living cell, the imaging of a HepG2 cellular system was performed, in which the fluorescence of M201-DPA in the blue channel was decreased upon addition of Cu and was enhanced in UV channel upon addition of Zn. The detection limits of M201-DPA for Cu and Zn in buffer solutions were 5.6 and 3.8 ppb, respectively. Importantly, the Cu and Zn detection limits of the developed sensors were significantly lower than permitted Cu and Zn concentrations in drinking water as established by the U.S. EPA and WHO.