A peroxidase-mimicking nanosensor with Hg~(2+) -triggered enzymatic activity of cysteine-decorated ferromagnetic particles for ultrasensitive Hg~(2+) detection in environmental and biological fluids

摘要

In this work, we developed a novel strategy for ultrasensitive Hg2+ detection based on the Hg2+-triggered peroxidase-mimicking activity of a cysteine-decorated ferromagnetic particle (Cys-Fe3O4). The as-synthesized Cys-Fe3O4 exhibited almost no peroxidase-like activity due to the Cys-Fe coordinative interaction and subsequently blocking of active sites on Fe3O4 by the Cys outerwear. In contrast, in the presence of Hg2+, surface Cys could be despoiled from the Cys-Fe3O4 particles by a stronger Cys-Hg2+-Cys coordination, resulting in the exposure of active Fe3O4 that could catalyze the oxidation of colorless 3,3', 5,5'-tetramethylbenzidine (TMB) into blue TMBox. The Cys-Fe3O4 particles were then employed to fabricate a colorimetric Hg2+ nanosensor. We found that the fabricated enzyme-mimicking biosensor enabled to monitor Hg2+ in a linear range of 0.02-90 nM, providing a limit of detection down to 5.9 pM. The enzyme-mimetic nanosensor also exhibited excellent selectivity for Hg2+ sensing against other common metal ions thanks to the strong coordinative interaction between Cys and Hg2+. Further, the nanosensor was applied to determine trace Hg2+ in environmental and biological fluids. Despite the relatively complex components of these samples, the enzyme-like biosensor still showed excellent accuracy, demonstrating its great promise in environmental monitoring and clinical examination.