Adsorption at cell surface and cellular uptake of silica nanoparticles with different surface chemical functionalizations: impact on cytotoxicity

International audienceSilica nanoparticles are particularly interesting for medical applications because of the high inertness and chemical stability of silica material. However, at the nanoscale their innocuousness must be carefully verified before clinical use. The aim of this study was to investigate the in vitro biological toxicity of silica nanoparticles depending on their surface chemical functionalization. To that purpose, three kinds of 50 nm fluorescent silica-based nanoparticles were synthesized: 1) sterically stabilized silica nanoparticles coated with neutral polyethylene glycol (PEG) molecules, 2) positively charged silica nanoparticles coated with amine groups and 3) negatively charged silica nanoparticles coated with carboxylic acid groups. RAW 264.7 murine macrophages were incubated for 20 hours with each kind of nanoparticles. Their cellular uptake and adsorption at the cell membrane were assessed by a fluorimetric assay and cellular responses were evaluated in terms of cytotoxicity, pro-inflammatory factor production and oxidative stress. Results showed that the highly positive charged nanoparticle, were the most adsorbed at cell surface and triggered more cytotoxicity than other nanoparticles types. To conclude, this study clearly demonstrated that silica nanoparticles surface functionalization represents a key parameter in their cellular uptake and biological toxicity

Radiocesium and potassium decreases in wild edible plants by food processing

More than 4 years has been past since March 11, 2011, and, at this stage, foods exceeding the standard limits of radiocesium were mainly from the wild. Thus one of the public’s main concerns is how to decrease ingestion of radiocesium from foods they have collected from the wild as well as from their home-grown fruits because these food materials are not monitored. In this study, we focused on wild edible plants and fruits and the effects of washing, boiling and pealing to remove radiocesium were observed. Samples were collected in 2013 and 2014 from Chiba and Fukushima Prefectures, e.g., young bamboo shoots, giant butterbur, chestnuts, etc. For wild edible plants were separated into three portions to make raw, washed and boiled samples. For fruit samples (i.e. persimmon, loquat and Japanese plum) fruit parts were separated into skin, flesh and seeds. It was found that washing plants is not effective to remove both 137Cs and 40K, and boiling provided different removal effects by plant tissues. There was a tendency that the retention factors of 137Cs and 40K for thinner plant body sample (leaves) were higher than those of thicker plant body types, e.g. giant butterbur petiole and bamboo shoots. Thus the boiling time as well as the crop thickness should affect radiocesium retention in processed foods. For fruits, 137Cs concentration was higher in skin than in fruit flesh for persimmon and loquat, however, Japanese apricot showed different distribution