Exploration and application of a highly sensitive bis(salamo)-based fluorescent sensor for B(4)O(7)(2−) in water-containing systems and living cells

A highly selective fluorescent sensor H(4)L based on a bis(salamo)-type compound with two N(2)O(2) chelating moieties as ionophore was successfully developed. Sensor H(4)L was found to have excellent selectivity for B(4)O(7)(2−) over many other anions (Br(−), CI(−), CN(−), CO(3)(2−), HCO(3)(−), H(2)PO(4)(−), HSO(4)(−), NO(3)(−), OAc(−), S(2)O(3)(−), SCN(−), SO(4)(2−), Hcy (homocysteine) and H(2)O(2)), and it exhibited an approximately 150-fold enhancement of the fluorescence response to B(4)O(7)(2−) in Tris-HCl buffer (DMF/H(2)O = 9:1, v/v, pH = 7) solutions. Significantly, its fluorescence intensity was enhanced in a linear fashion with increasing concentrations of B(4)O(7)(2−). The detection limit of sensor H(4)L towards B(4)O(7)(2−) was 8.61 × 10(−7) M. The test strips could conveniently, efficiently and simply detect B(4)O(7)(2−) ions in Tris-HCl buffer (DMF/H(2)O = 9:1, v/v, pH = 7) solutions. Furthermore, sensor H(4)L showed excellent membrane permeability in living cells, and it was successfully used to monitor intracellular B(4)O(7)(2−) by confocal luminescence imaging.