Development of a multilevel approach for the evaluation of nanomaterials toxicity

Aim: To develop a multilevel approach that includes different toxicity tests and gene-expression studies for toxicity evaluation of engineered nanomaterials developed for biomedical applications. Materials & methods: K-562, MCF-7 and U-937 human-derived cell lines were used as models for in vitro toxicity tests. These tests included viability assays (3-[4,5-dimethylthiazol-2-yl]-5-[3-carboxymethoxyphenyl]-2-[4-sulfophenyl]-2H-tetrazolium [MTS] assay); evaluation of apoptosis/necrosis by propidium iodide staining and DNA laddering assay; evaluation of mitochondrial toxicity (5,5´,6,6´-tetrachloro-1,1´,3,3´-tetraethyl-benzimidazolcarbocyanine iodide [JC-1] assay); transmission electron microscopy analysis and gene expression analysis by DNA microarray. For in vivo toxicity evaluation, Swiss mice were used for monitoring acute or chronic effects. Two superparamagnetic contrast agents approved for human use (Resovist® and Primovist®) and two new lanthanide-based luminescent nanoparticles were tested. Results & discussion: The nanomaterials approved for human use did not show significant toxicities in our assays. Toxicity studies performed on lanthanide-based nanoparticles (EDTA120 and EDTA120D) complexed with the chelating agent EDTA revealed that these nanomaterials induced necrosis in U-937 and K-562 cells while no toxicity was observed in MCF-7 cells. Moreover, no in vivo effects have been observed. The comparative analysis of the nanomaterials and their separated components showed that the toxicity in U-937 and K-562 cells was mainly due to the presence of EDTA. Conclusion: The multilevel approach proved to be useful for nanomaterial toxicity characterization. In particular, for the lanthanide-based nanoparticles tested in this work, the EDTA was identified as the main cause of the toxicity in vitro, suggesting a possible applicability of these nanoparticle suspensions for in vivo optical imagin

XAS and GIXRD Study of Co Sites in CoAl2O4 Layers Grown by MOCVD

The chemical environment of Co sites in CoAl2O4 layers grown by metal-organic chemical vapor deposition has been investigated by X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD). It is shown that the air- or [O2 + H2O]-annealing at 500 °C of the layers deposited at low temperature induce a partial crystallization with the formation of (Co1-2ηAl2)(Co2Al2η)(Co 2ηAl2(1-η)))O4 spinel (η = 0.2-0.27). Nevertheless, slightly more than half of Co remains in an amorphous phase, and XAS data are consistent with the formation of a medium-range ordered Co3O4 phase, especially upon air-annealing. Layers grown at higher temperatures (600-650 °C) exhibit a similar but more complex structure, since the presence of an additional medium-range ordered phase (likely, CoAl2O4) is also revealed. The air-annealing at high temperature (800 °C) generates blue, almost completely crystalline, CoAl2O4 layers. Optical properties of deposited layers are discussed by referring to the outcomes of structural results. In particular, the optical absorption spectrum results negligibly affected by the presence of the amorphous phase, while absorptions present in the 300-500 nm range, responsible for the green layer color and evident in samples annealed in an oxidizing atmosphere or grown at high temperature, are likely caused by the octahedrally coordinated Co ions of the partially inverted spinel (Co;- 2ηAl2η)(Co2(1-η)Al 2(1-η))O4 -))O4 phase. Despite the XRD analysis that ultimately demonstrates the presence of octahedrally coordinated Co ions, whose oxidation state in the spinel phase is in majority Co(II), the occurrence of Co(III) species with an octahedral environment cannot be ruled out