"Investigating the hazards posed by pristine and modified copper nanomaterials using in vitro screens combined with in vivo models"
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Nanomaterial use has increased as the properties of materials at the nanoscale differ substantially from bulk materials. However, there is still a lack of information concerning their impact on human health and environment. Part of this study investigated the hazard of copper oxide nanoparticles (CuO NPs), multi-wall carbon nanotubes, silicon dioxide, pigment Red 254 and cobalt coated tungsten carbide using an in vitro hepatocyte model (HepG2/C3A cell lines). Most of the work was then conducted on CuO NPs together with four Safer by Design modifications of the same NPs (either citrate, ascorbate, polyethylenimine (PEI) or polyvinylpyrrolidone coating) and on both copper amine and micronized copper formulations, investigating their potency as inhibitors of fungal growth and analysing the gene expression in vivo on inhalation and ingestion models (Wistar rats). Copper materials consistently exerted cytotoxicity to HepG2/C3A cells and induced cytokine production 24 hours post exposure. Micronized copper and ascorbate coated CuO were the most and the least toxic respectively. Copper amine was most effective at reducing the fungal growth of Coniophora puteana, Trametes versicolor and Gloeophyllum trabeum while ascorbate coating enhanced the antifungal effect of CuO NPs. In vivo, short-term inhalation studies (STIS) were performed with pristine, ascorbate and PEI coatings. All the materials upregulated tumour necrosis factor alpha (TNFα) in lung tissue; in the short-term oral study (STOS) with CuO NPs and micronized copper, only the latter downregulated chemokine C-X-C motif ligand 2 (CXCL2) in the liver and metallothionein 1A in the ileum. In conclusion, CuO NPs were relatively cytotoxic in vitro and induced pro-inflammatory responses both in vitro and in vivo. However, these NPs were ineffective as antifungal treatment while the ascorbate coating enhanced the antifungal effect together with a significant decrease of cytotoxicity in vitro. The other materials did not induce any significant cytotoxicity nor cytokine production in C3A cells.