Great efforts have been devoted to the development of sensitive and specific analysis methods for biothiols because of their important roles in
biological systems. We present a new detection system for biothiols that is based on the reversible quenching and restoration of fluorescence of
terbium chelate caused by Hg(2+) and
thiol species. In the presence of biothiols, a restoration of fluorescence of
terbium chelate after quenching by Hg(2+) was observed due to the interaction of Hg(2+) with
thiol groups, and the restored fluorescence increased with the concentration of biothiols. This method was sensitive and selective for biothiols. The detection limit was 80 nM for
glutathione, 100 nM for Hcy, and 400 nM for
Cysteine, respectively. The
terbium chelate-Hg (II) system was successfully applied to determine the levels of biothiols in
cancer cells and urine samples. Further, it was also shown to be comparable to Ellman's assay. Compared to other fluorescence methods, the
terbium chelate probe is advantageous because interference from short-lived nonspecific fluorescence can be efficiently eliminated due to the long fluorescence lifetime of
terbium chelate, which allows for detection by time-resolved fluorescence. The
terbium chelate probe can serve as a diagnostic tool for the detection of abnormal levels of biothiols in disease.