Pyridine-biquinoline-metal complexes for sensing pyrophosphate and hydrogen sulfide in aqueous buffer and in cells

Herein, we report a new pyridine-biquinoline-derivative fluorophore L for effectively sensing pyrophosphate (PPi) and monohydrogen sulfide (HS(-)) in aqueous buffer and in living cells. L could selectively coordinate with metal ions (M(n+)) in Groups IB and IIB to form L-M(n+) complexes with 1:1 stoichiometry, resulting in fluorescence quenching via photoinduced electron transfer (PET) mechanism. L-Zn(2+) complex was applied to competitively coordinate with PPi to form a new "ate"-type complex, turning on the fluorescence by a 21-fold-increase. The limit of detection (LOD) of this assay for PPi detection in aqueous buffer is 0.85 μM. L-Cu(2+) complex was applied for highly selective detection of HS(-) with an excellent sensitivity by 25-fold decomplexation-induced fluorescence increase. LOD of L-Cu(2+) complex for HS(-) detection in aqueous buffer is 2.24 μM. With the in vitro data obtained, we successfully applied these two complexes for sequential imaging Zn(2+) and PPi, Cu(2+) and HS(-) in living cells, respectively. Since PPi and HS(-) occur in vascular calcification in positive correlation, our multifunctional probe L might help doctors to more precisely diagnose this disease in vivo in the future. For example, we could use radioactive tracer L-(64)Cu for qualitative and quantitative positron emission tomography/computed tomography (PET/CT) imaging of HS(-) in vivo.