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Philip J Smith1, Maude Giroud2, Helen L Wiggins2, Florence Gower2, Jennifer A Thorley2, Bjorn Stolpe3, Julie Mazzolini2, Rosemary J Dyson4, Joshua Z Rappoport21Physical Sciences of Imaging for the Biomedical Sciences (PSIBS) Doctoral Training Center, School of Chemistry, 2School of Biosciences, 3School of Geography, Earth, and Environmental Sciences, 4School of Mathematics, University of Birmingham, Edgbaston, Birmingham, United KingdomAbstract: Increasing production and application of nanomaterials raises significant questions regarding the potential for cellular entry and toxicity of nanoparticles. It was observed that the presence of serum reduces the cellular association of 20 nm carboxylate-modified fluorescent polystyrene beads up to 20-fold, relative to cells incubated in serum-free media. Analysis by confocal microscopy demonstrated that the presence of serum greatly reduces the cell surface association of nanoparticles, as well as the potential for internalization. However, both in the presence and absence of serum, nanoparticle entry depends upon clathrin-mediated endocytosis. Finally, experiments performed with cells cooled to 4°C suggest that a proportion of the accumulation of nanoparticles in cells was likely due to direct permeabilization of the plasma membrane.Keywords: nanoparticles, polystyrene beads, serum, endocytosis, dynamin, clathrin, permeabilization

Corrigendum Smith PJ, Giroud M, Wiggins HL, et al. Int J Nanomedicine. 2012;7:2045–2055.Page 2054, Figure 11, the text “Average no of NPs in lumen: Nf =2.1×10-3” should read “Average no of NPs in lumen:Nf =2.1×10-2”. Page 2054, Figure 11, the figure legend “Figure 11 A series of calculations to estimate the number of nanoparticles that could enter a vesicle under the incubation conditions described in materials and methods. It is estimated that nanoparticles are nearly 25,000 times more likely to enter cells when they are bound to the membrane than in the fluid phase.” should read “Figure 11 A series of calculations to estimate the number of nanoparticles that could enter a vesicle under the incubation conditions described in materials and methods. It is estimated that nanoparticles are nearly 2,500 times more likely to enter cells when they are bound to the membrane than in the fluid phase.” Page 2054, first column, line 13, the sentence “Even though the latter might be an overestimation, the current analyses suggest that under these conditions nanoparticles are nearly 25,000 times more likely to enter cells bound to the inner membrane of a vesicle than through the fluid phase.” should read “Even though the latter might be an overestimation, the current analyses suggest that under these conditions nanoparticles are nearly 2,500 times more likely to enter cells bound to the inner membrane of a vesicle than through the fluid phase”.Read the original article

Measurements of the physiochemical speciation of Fe in the euphotic zone were performed at three different locations, over a well defined salinity gradient, during spring and summer in the Baltic Sea. The average of total Fe changed from 114nM in the Bothnian Sea, 44nM at Landsort Deep and 15nM at Gotland Deep. Particulate Fe (PFe) was the dominating phase at all stations and on average accounted for 75-85% of the total Fe pool. At all three locations, a decrease in total Fe of 80-90% from initial measurements compared to the summer was found. A strong positive correlation between PFe and chl-a was observed. Hence, primary production strongly regulates cycling of suspended Fe. However, this relation is not dominated by active uptake of Fe in phytoplankton; instead this reflects cycling of phosphorus, growth of diatoms, and removal of PFe during phytoplankton sedimentation. The average colloidal iron fraction, CFe, showed decreasing concentrations along the salinity gradient; Bothnian Sea 15 nM; Landsort Deep 1nM and Gotland Deep 0.5 nM. Field Flow Fractionation data indicate that the main colloidal carrier phase for Fe in the Baltic Sea is a carbon-rich fulvic acid associated compound, likely of riverine origin. The Fe isotope composition (δ56Fe) of the PFe showed constant positive values in the Bothnian Sea surface waters (+0.08 to +0.20‰. Enrichment of heavy Fe in the Bothnian Sea PFe is most likely associated to input of aggregated land derived Feoxyhydroxides and a rapid overturn 20 of Fe(II). At the Landsort deep, the fractionation of PFe changed between -0.08% to +0.28‰. The negative values, in early spring, probably indicate exchange over the oxic-anoxic boundary at ∼80m depth. [ABSTRACT FROM AUTHOR]