Synthesis and properties of anhydrous rare-earth phosphates, monazite and xenotime: a review.

The synthesis methods, crystal structures, and properties of anhydrous monazite and xenotime (REPO4) crystalline materials are summarized within this review. For both monazite and xenotime, currently available Inorganic Crystal Structure Database data were used to study the effects of incorporating different RE cations on the unit cell parameters, cell volumes, densities, and bond lengths. Domains of monazite-type and xenotime-type structures and other AXO4 compounds (A = RE; X = P, As, V) are discussed with respect to cation sizes. Reported chemical and radiation durabilities are summarized. Different synthesis conditions and chemicals used for single crystals and polycrystalline powders, as well as first-principles calculations of the structures and thermophysical properties of these minerals are also provided.

Reduced Cationic Nanoparticle Cytotoxicity Based on Serum Masking of Surface Potential.

Functionalization of nanoparticles with cationic moieties, such as polyethyleneimine (PEI), enhances binding to the cell membrane; however, it also disrupts the integrity of the cell's plasma and vesicular membranes, leading to cell death. Primary fibroblasts were found to display high surface affinity for cationic iron oxide nanoparticles and greater sensitivity than their immortalized counterparts. Treatment of cells with cationic nanoparticles in the presence of incremental increases in serum led to a corresponding linear decrease in cell death. The surface potential of the nanoparticles also decreased linearly as serum increased and this was strongly and inversely correlated with cell death. While low doses of nanoparticles were rendered non-toxic in 25% serum, large doses overcame the toxic threshold. Serum did not reduce nanoparticle association with primary fibroblasts, indicating that the decrease in nanoparticle cytotoxicity was based on serum masking of the PEI surface, rather than decreased exposure. Primary endothelial cells were likewise more sensitive to the cytotoxic effects of cationic nanoparticles than their immortalized counterparts, and this held true for cellular responses to cationic microparticles despite the much lower toxicity of microparticles compared to nanoparticles.