Ce4+-triggered cascade reaction for ratiometric fluorescence detection of alendronate

A ratiometric fluorescence assay for alendronate (ALDS) has been designed with Ce 4+ -triggered cascade chromogenic reaction. This strategy involves three processes: (1) Ce 4+ oxidizes ascorbic acid (AA) into dehydroascorbic acid (DHAA), which then condenses with o -phenlenediamine (OPD) to generate fluorescent 3-(dihydroxyethyl)furo[3,4- b ] quinoxaline-1-one (DFQ), presenting the maximum emission at 434 nm; (2) As oxidase-mimics, Ce 4+ can oxidize OPD into fluorescent 2,3-diaminophenazine (DAP) which shows a strong emission at 568 nm; (3) ALDS inhibits the oxidation ability of Ce 4+ towards OPD, thus inhibiting the generation of DAP. Accordingly, a homogeneous ratiometric fluorescence system with dual emission comes into being and the presence of ALDS can change the fluorescence intensity ratio obviously. With F 434 / F 568 as readout, ALDS can be detected sensitively with the detection limit of 30 nM. Moreover, this ratiometric method was used to analyze ALDS in both human serum and pharmaceutical samples.