Application of TiO2 nanoparticles to reduce bioaccumulation of arsenic in rice seedlings (Oryza sativa L.): A mechanistic study.

The possible application of TiO2 nanoparticles (nano-TiO2) to alleviate arsenic bioaccumulation in rice seedlings and such a functioning with their crystalline structure were investigated. Specifically, nano-TiO2 with anatase and rutile structures and the bulk TiO2 at 0, 10, 100, and 1000 mg/L were amended to the hydroponic exposure systems with arsenic concentration at 1 mg/L, and the plant was exposed for 7 days. Our findings indicated that nano-TiO2 significantly reduced arsenic bioaccumulation in rice seedlings by 40-90% via strong sorption process, but their growth was not affected. Nano-TiO2 amendment notably alleviated oxidative stress resulting from arsenic exposure. Without nano-TiO2 amendment, the iron plaque on root surfaces served as a strong barrier to inhibit arsenic uptake by rice seedlings. Interestingly, nano-TiO2 amendment significantly decreased the iron plaque amount by 50-63% and weakened the arsenic retention in this barrier by 47-99%, further verifying the overwhelming superiority of nano-TiO2 in inhibiting arsenic uptake by rice seedlings. Rutile nano-TiO2 (NRT) at 1000 mg/L presented to be a promising candidate for controlling arsenic uptake by the exposed rice seedlings, with no significant oxidative stress by the amended nano-TiO2, thereby mitigating health risk of arsenic to humans via food chain.