A versatile water soluble fluorescent probe for ratiometric sensing of Hg2+ and bovine serum albumin

A novel tetraazamacrocycle fluorescent sensor (6-(1-(dimethylamino)-5-naphthalene sulfonyl)-3,6,9,15-tetraazabicyclo[9.3.1] pentadeca-1(15), 11,13-triene, 1) has been designed and prepared, which can be utilized for selective and ratiometric sensing of Hg2+ and bovine serum albumin (BSA) with two different responsive modes in aqueous solution at physiological pH (50 mM Tris-HCl, pH 7.6). Above 0.5 ppb Hg2+ can be discerned by coordination with 1 and the emission color changes enable 1 to be applied to a fast Hg2+ test paper assay. Sensor 1 has also been demonstrated to be easily cell-penetrable and applicable for Hg2+ imaging in living cells. Imaging of BSA in the gel using SDS-PAGE (sodium dodecyl sulfate polyacrylamide gel electrophoresis) stained in the medium containing 1 verified that the binding of 1 and BSA was successful in the presence of nonprotein substances. The linear range of 1 towards BSA utilizing ratiometric fluorescent calibration via noncovalent interaction in solution is 0-100 mu g mL(-1) with a detection limit of 1 mg mL(-1), and has been successfully employed to determine the albumin concentration in blood serum by means of ratiometric fluorescent measurements for the first time. Finally, sensor 1 behaves as a fluorescent molecular switch composed of triple logic gates upon chemical inputs of Hg2+ and BSA, which potentially provides intelligent diagnostics for Hg2+ contaminated serum on the nanoscale.