Dual-Analyte Fluorescent Sensor Based on [5]Helicene Derivative with Super Large Stokes Shift for the Selective Determinations of Cu²⁺ or Zn²⁺ in Buffer Solutions and Its Application in a Living Cell

Abstract

A new fluorescent sensor, M201-DPA, based on [5]helicene derivative was utilized as dual-analyte sensor for determination of Cu²⁺ or Zn²⁺ in different media and different emission wavelengths. The sensor could provide selective and bifunctional determination of Cu²⁺ in HEPES buffer containing Triton-X100 and Zn²⁺ 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 Cu²⁺. On the other hand, in Tris buffer/methanol, M201-DPA showed the selective OFF-ON fluorescence enhancement upon the addition of Zn²⁺, 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 Zn²⁺ and Cu²⁺ 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 Cu²⁺ and was enhanced in UV channel upon addition of Zn²⁺. The detection limits of M201-DPA for Cu²⁺ and Zn²⁺ in buffer solutions were 5.6 and 3.8 ppb, respectively. Importantly, the Cu²⁺ and Zn²⁺ detection limits of the developed sensors were significantly lower than permitted Cu²⁺ and Zn²⁺ concentrations in drinking water as established by the U.S. EPA and WHO.