Study of silver nanoparticles bioaccumulation in cultured red and green seaweed

The bioaccumulation of polyvinylpyrrolidone-coated silver nanoparticles (PVP-AgNPs) in Palmaria palmata and Ulva sp. seaweed was investigated by ICP-MS and SP-ICP-MS (determination of nanoparticles and size distribution after an enzymatic extraction). Seaweeds were exposed to 0.1 and 1.0 mg L^-1 of PVP-AgNPs of small particle size (15 nm) for 28 days. They were cultured in 40-L seawater tanks and nanoparticles were mixed with growing media and the phytoplankton used for feeding. Bioaccumulation changed with the type of seaweed and was not proportional to the concentration. Palmaria palmata and Ulva sp. reached the maximum total Ag concentration at 14 and 21 days of exposure to 1.0 mg L^-1, respectively. The Ag concentrations measured (until 0.79 ± 0.06 μg g^-1 w.w.) were much smaller than those found in previous studies after short-term exposure (up to 48 h) under laboratory conditions, probably due to the presence of organic matter in the growing media. The maximum concentrations of AgNPs were achieved at 14 and 28 days for Palmaria palmata and Ulva sp., respectively, with most frequent sizes of approximately 20 nm. The size values measured by SP-ICP-MS agreed with TEM sizes in the enzymatic extracts. No changes were observed in the concentrations of most metals (Co, Cr, Cu, Mo, Ni, Rb and V) in exposed seaweed; only a decrease of Cd and Pb at the dose of 1 mg L^-1 in Palmaria was observed. Studies simulating the real marine environment are important to estimate bioaccumulation and safety, which change depending on the type of seaweed and nanoparticle.