Effect of surface charge on the uptake and distribution of gold nanoparticles in four plant species.

Small (6-10 nm) functionalized gold nanoparticles (AuNPs) featuring different, well-defined surface charges were used to probe the uptake and distribution of nanomaterials in terrestrial plants, including rice, radish, pumpkin, and perennial ryegrass. Exposure of the AuNPs to plant seedlings under hydroponic conditions for a 5-day period was investigated. Results from these studies indicate that AuNP uptake and distribution depend on both nanoparticle surface charge and plant species. The experiments show that positively charged AuNPs are most readily taken up by plant roots, while negatively charged AuNPs are most efficiently translocated into plant shoots (including stems and leaves) from the roots. Radish and ryegrass roots generally accumulated higher amounts of the AuNPs (14-900 ng/mg) than rice and pumpkin roots (7-59 ng/mg). Each of the AuNPs used in this study were found to accumulate to statistically significant extents in rice shoots (1.1-2.9 ng/mg), while none of the AuNPs accumulated in the shoots of radishes and pumpkins.