Elucidating the Physiological Mechanisms Underlying Enhanced Arsenic Hyperaccumulation by Glutathione Modified Superparamagnetic Iron Oxide Nanoparticles in Isatis Cappadocica

Widespread arsenic (As) contamination is a severe environmental and public health concern. Isatis cappadocica, an arsenic hyperaccumulator, holds great potential to clean up As-contaminated soil and groundwater. Iron oxide is one of the most common metal oxides in the natural environment and its nanoparticulate form has been previously utilized for the removal of heavy metals/metalloids from wastewater. However, there is a paucity of information on the impact of iron oxide nanoparticles on the growth and physiological properties of I. cappadocica and its effectiveness on As removal. Current study reports for the first time the impact of superparamagnetic iron oxide nanoparticles and glutathione (GSH) modified superparamagnetic iron oxide nanoparticles (nFe3O4 and nFe3O4@GSH) on the physiological characteristic of I. cappadocica and its accumulation of As under hydroponic condition. nFe3O4@GSH alleviated the harmful impact of As and significantly increased the shoot biomass of I. cappadocica by enhancing the plant defense mechanisms. The application of GSH, nFe3O4 and nFe3O4@GSH all lowered the As concentration in plant shoots as a protective mechanism. However, the substantial shoot biomass increase due to nFe3O4@GSH resulted in a 56% higher As accumulation in plant shoots than in plants exposed to As alone, indicating the strong effectiveness of nFe3O4@GSH as a novel enhancer of the As phytoremediation by I. cappadocica. Our data further showed that the beneficial effect of nFe3O4@GSH on As phytoremediation is due to the enhancement of activities of several enzymatic and nonenzymatic antioxidants.