Fe(III) bipyridyl or phenanthroline complexes with oxidase-like activity for sensitive colorimetric detection of glutathione

In this study, three types of Fe(III) bipyridyl or phenanthroline (Fe(III)-L 3 ) complex could directly catalyze 3,3′,5,5′-tetramethylbenzidine (TMB) to induce blue chromogenic changes without H 2 O 2 . Fe(III)-L 3 complex could induce a colour change in TMB directly after a short incubation time. Due to the high oxidase-like activity of the Fe(III)-L 3 complexes, superoxide anion radicals (O 2 •– ) were formed in solution. Intermediates radical involving oxo-iron species were then produced that oxidized TMB to its oxidation products (oxTMB), which had an absorbance maximum at 652 nm. Glutathione (GSH) could inhibit the oxidation reaction of the Fe(III)-L 3 complex–TMB system, a rapidly colorimetric method was established for the specific detection of GSH that had a detection limit of 0.1 μM. Furthermore, Fe(III)-L 3 complexes could catalyze TMB to oxTMB directly without H 2 O 2 . This fast and simple colorimetric method may open a new avenue for application in the point-of-care diagnosis field using the TMB chromogenic system.