Copper oxide nanoparticles (CuO-NPs) are frequently used for many technical applications, but are also known for their cell toxic potential. In order to investigate a potential use of CuO-NPs as a therapeutic drug for glioma treatment, we have investigated the consequences of an application of CuO-NPs on the cellular copper content and cell viability of C6 glioma cells. CuO-NPs were synthesized by a wet-chemical method and were coated with dimercaptosuccinic acid and bovine serum albumin to improve colloidal stability in physiological media. Application of these protein-coated nanoparticles (pCuO-NPs) to C6 cells caused a strong time-, concentration- and temperature-dependent copper accumulation and severe cell death. The observed loss in cellular MTT-reduction capacity, the loss in cellular LDH activity and the increase in the number of propidium iodide-positive cells correlated well with the specific cellular copper content. C6 glioma cells were less vulnerable to pCuO-NPs compared to primary astrocytes and toxicity of pCuO-NPs to C6 cells was only observed for incubation conditions that increased specific cellular copper contents above 20 nmol copper per mg protein. Both cellular copper accumulation as well as the pCuO-NP-induced toxicity in C6 cells were prevented by application of copper chelators, but not by endocytosis inhibitors, suggesting that liberation of copper ions from the pCuO-NPs is the first step leading to the observed toxicity of pCuO-NP-treated glioma cells.

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Investigations on colloidal stability and ecotoxicological effects of DMSA-coated and uncoated IONP with Raphidocelis, Daphnia and Lemna.

To investigate the cellular uptake of iron oxide nanoparticles (IONPs), we have synthesized fluorescent IONPs by using dimercaptosuccinate (DMSA) which had been covalently modified with the fluorescence dyes BODIPY (BP), Oregon Green (OG) or tetramethylrhodamine (TMR) as coating material. Dispersed in physiological media, the synthesized IONPs did not differ in hydrodynamic diameter, ζ-potential and colloidal stability compared to non-fluorescent IONPs. Uptake studies of the fluorescent IONPs on C6 glioma cells at 37 °C in serum-free medium revealed that the cells accumulated after exposure to non-fluorescent or fluorescent IONPs almost identical specific cellular iron contents. The cellular iron accumulation during exposure to IONPs at 37 °C was lowered by around 30%, if the cells were incubated with IONPs at 4 °C, and by 85%, if the cells had been incubated in the presence of serum. Fluorescence microscopy of the cells exposed to fluorescent IONPs confirmed these results and revealed a perinuclear doted fluorescence staining of the cells after exposure to fluorescent IONPs. Comparison of the three types of fluorescent IONPs revealed that the fluorescence in cells treated with OG-IONPs or TMR-IONPs remained stable while rapid fluorescence bleaching was observed for cells that had been exposed to BP-IONPs. These data demonstrate that C6 cells efficiently accumulate DMSA-coated IONPs in a time-and concentration-dependent manner by a mechanism which is strongly affected by the temperature and the presence of serum.