Interference of CuO nanoparticles with metal homeostasis in hepatocytes under sub-toxic conditions

Remediation of Metal Oxide Nanotoxicity with a Functional Amyloid

Understanding the environmental health and safety of nanomaterials (NanoEHS) is essential for the sustained development of nanotechnology. Although extensive research over the past two decades has elucidated the phenomena, mechanisms, and implications of nanomaterials in cellular and organismal models, the active remediation of the adverse biological and environmental effects of nanomaterials remains largely unexplored. Inspired by recent developments in functional amyloids for biomedical and environmental engineering, this work shows their new utility as metallothionein mimics in the strategically important area of NanoEHS. Specifically, metal ions released from CuO and ZnO nanoparticles are sequestered through cysteine coordination and electrostatic interactions with beta-lactoglobulin (bLg) amyloid, as revealed by inductively coupled plasma mass spectrometry and molecular dynamics simulations. The toxicity of the metal oxide nanoparticles is subsequently mitigated by functional amyloids, as validated by cell viability and apoptosis assays in vitro and murine survival and biomarker assays in vivo. As bLg amyloid fibrils can be readily produced from whey in large quantities at a low cost, the study offers a crucial strategy for remediating the biological and environmental footprints of transition metal oxide nanomaterials.

Schistosoma mansoni infection induces hepatic metallothionein and S100 protein expression alongside metabolic dysfunction in hamsters

Schistosomiasis, a widespread neglected tropical disease, presents a complex and multifaceted clinical-pathological profile. Using hamsters as final hosts, we dissected molecular events following Schistosoma mansoni infection in the liver-the organ most severely affected in schistosomiasis patients. Employing tandem mass tag-based proteomics, we studied alterations in the liver proteins in response to various infection modes and genders. We examined livers from female and male hamsters that were: noninfected (control), infected with either unisexual S. mansoni cercariae (single-sex) or both sexes (bisex). The infection induced up-regulation of proteins associated with immune response, cytoskeletal reorganization, and apoptotic signaling. Notably, S. mansoni egg deposition led to the down-regulation of liver factors linked to energy supply and metabolic processes. Gender-specific responses were observed, with male hamsters showing higher susceptibility, supported by more differentially expressed proteins than found in females. Of note, metallothionein-2 and S100a6 proteins exhibited substantial up-regulation in livers of both genders, suggesting their pivotal roles in the liver's injury response. Immunohistochemistry and real-time-qPCR confirmed strong up-regulation of metallothionein-2 expression in the cytoplasm and nucleus upon the infection. Similar findings were seen for S100a6, which localized around granulomas and portal tracts. We also observed perturbations in metabolic pathways, including down-regulation of enzymes involved in xenobiotic biotransformation, cellular energy metabolism, and lipid modulation. Furthermore, lipidomic analyses through liquid chromatography-tandem mass spectrometry and matrix-assisted laser desorption/ionization mass spectrometry imaging identified extensive alterations, notably in cardiolipin and triacylglycerols, suggesting specific roles of lipids during pathogenesis. These findings provide unprecedented insights into the hepatic response to S. mansoni infection, shedding light on the complexity of liver pathology in this disease.

Antimicrobial Peptide- and Dentin Matrix-Functionalized Hydrogel for Vital Pulp Therapy via Synergistic Bacteriostasis, Immunomodulation, and Dentinogenesis

The preservation of vital pulps is crucial for maintaining the physiological functions of teeth; however, vital pulp therapy (VPT) of pulpitis teeth remains a substantial challenge due to uncontrolled infection, excessive inflammation, and limited regenerative potential. Current pulp capping agents have restricted effects in the infectious and inflammatory microenvironment. To address this, a multifunctional hydrogel (TGH/DM) with antibacterial, immunomodulatory, and mineralization-promoting effects is designed. The antimicrobial peptide (AMP) and demineralized dentin matrix are incorporated into the hydrogel, achieving sustainable delivery of AMP and a cocktail of growth factors. In vitro results show that TGH/DM could kill endodontic microbiota, ameliorate inflammatory responses of human dental pulp stem cells (hDPSCs), and prompt odontogenic differentiation of inflammatory hDPSCs via activation of peroxisome proliferator-activated receptor gamma. In vivo results suggest that TGH/DM is capable of inducing M2 phenotype transformation of macrophages in mice and fostering the regeneration of the dentin-pulp complex in inflamed pulps of beagle dogs. Overall, this study first proposes the synergistic regulation of AMP and tissue-specific extracellular matrix for the treatment of pulpitis, and the advanced hydrogel provides a facile and effective way for VPT.

Exploring the cytotoxicity mechanisms of copper ions and copper oxide nanoparticles in cells from the excretory system

Copper oxide nanoparticles (CuO NPs) are widely applied in various products, including food, cosmetic, biomedical, and environmental goods. Despite their broad use, potential risks are still associated with these NPs, therefore, the aim of this study is to delve deeper into the cytotoxic effects of 85 nm CuO NPs on kidney MDCK and liver AML-12 cells, representing cell models from the excretory system. Our findings pointed out that the viability of both cell lines decreased in a concentration-dependent manner when exposed to CuO NPs. Additionally, CuO NPs induced the overproduction of reactive oxygen species (ROS) and caused depolarization of the mitochondrial membrane, thereby arresting the cell cycle at the G2/M phase in MDCK and AML-12 cells. Importantly, unlike others our study uncovered distinctive forms of cellular death induced by CuO NPs in these cell lines. MDCK cells exhibited a combination of apoptosis and autophagy while early apoptosis was predominant in AML-12 cells. Moreover, the role of Cu2+ ions and CuO NPs in exerting cytotoxic effects was investigated, revealing that MDCK cells were affected by both copper ions and NPs. In contrast, AML-12 cells experienced toxic effects solely from CuO NPs. These findings provide crucial insights into the different cell death mechanisms caused either by CuO NPs or Cu2+ ions in excretory system cells in vitro. Nevertheless, further research is needed to explore the underlying mechanisms at the in vivo level, ensuring the safe use of CuO NPs. The results suggest that specific concentrations of metal oxide NPs can impact the physiology of cells within the excretory system of various mammals, including humans, and pave the way for comparing the toxic effects between ions and nanoparticles for further nanotoxicological studies.

Biochemical effects of copper nanomaterials in human hepatocellular carcinoma (HepG2) cells

In dose-response and structure-activity studies, human hepatic HepG2 cells were exposed for 3 days to nano Cu, nano CuO or CuCl2 (ions) at doses between 0.1 and 30 ug/ml (approximately the no observable adverse effect level to a high degree of cytotoxicity). Various biochemical parameters were then evaluated to study cytotoxicity, cell growth, hepatic function, and oxidative stress. With nano Cu and nano CuO, few indications of cytotoxicity were observed between 0.1 and 3 ug/ml. In respect to dose, lactate dehydrogenase and aspartate transaminase were the most sensitive cytotoxicity parameters. The next most responsive parameters were alanine aminotransferase, glutathione reductase, glucose 6-phosphate dehydrogenase, and protein concentration. The medium responsive parameters were superoxide dismutase, gamma glutamyltranspeptidase, total bilirubin, and microalbumin. The parameters glutathione peroxidase, glutathione reductase, and protein were all altered by nano Cu and nano CuO but not by CuCl2 exposures. Our chief observations were (1) significant decreases in glucose 6-phosphate dehydrogenase and glutathione reductase was observed at doses below the doses that show high cytotoxicity, (2) even high cytotoxicity did not induce large changes in some study parameters (e.g., alkaline phosphatase, catalase, microalbumin, total bilirubin, thioredoxin reductase, and triglycerides), (3) even though many significant biochemical effects happen only at doses showing varying degrees of cytotoxicity, it was not clear that cytotoxicity alone caused all of the observed significant biochemical effects, and (4) the decreased glucose 6-phosphate dehydrogenase and glutathione reductase support the view that oxidative stress is a main toxicity pathway of CuCl2 and Cu-containing nanomaterials.

Copper oxide nanoparticles: In vitro and in vivo toxicity, mechanisms of action and factors influencing their toxicology

Copper oxide nanoparticles (CuO NPs) have received increasing interest due to their distinctive properties, including small particle size, high surface area, and reactivity. Due to these properties, their applications have been expanded rapidly in various areas such as biomedical properties, industrial catalysts, gas sensors, electronic materials, and environmental remediation. However, because of these widespread uses, there is now an increased risk of human exposure, which could lead to short- and long-term toxicity. This review addresses the underlying toxicity mechanisms of CuO NPs in cells which include reactive oxygen species generation, leaching of Cu ion, coordination effects, non-homeostasis effect, autophagy, and inflammation. In addition, different key factors responsible for toxicity, characterization, surface modification, dissolution, NPs dose, exposure pathways and environment are discussed to understand the toxicological impact of CuO NPs. In vitro and in vivo studies have shown that CuO NPs cause oxidative stress, cytotoxicity, genotoxicity, immunotoxicity, neurotoxicity, and inflammation in bacterial, algal, fish, rodents, and human cell lines. Therefore, to make CuO NPs a more suitable candidate for various applications, it is essential to address their potential toxic effects, and hence, more studies should be done on the long-term and chronic impacts of CuO NPs at different concentrations to assure the safe usage of CuO NPs.

Immunotoxicity of metal and metal oxide nanoparticles: from toxic mechanisms to metabolism and outcomes

The influence of metal and metal oxide nanomaterials on various fields since their discovery has been remarkable. They have unique properties, and therefore, have been employed in specific applications, including biomedicine. However, their potential health risks cannot be ignored. Several studies have shown that exposure to metal and metal oxide nanoparticles can lead to immunotoxicity. Different types of metals and metal oxide nanoparticles may have a negative impact on the immune system through various mechanisms, such as inflammation, oxidative stress, autophagy, and apoptosis. As an essential factor in determining the function and fate of immune cells, immunometabolism may also be an essential target for these nanoparticles to exert immunotoxic effects in vivo. In addition, the biodegradation and metabolic outcomes of metal and metal oxide nanoparticles are also important considerations in assessing their immunotoxic effects. Herein, we focus on the cellular mechanism of the immunotoxic effects and toxic effects of different types of metal and metal oxide nanoparticles, as well as the metabolism and outcomes of these nanoparticles in vivo. Also, we discuss the relationship between the possible regulatory effect of nanoparticles on immunometabolism and their immunotoxic effects. Finally, we present perspectives on the future research and development direction of metal and metal oxide nanomaterials to promote scientific research on the health risks of nanomaterials and reduce their adverse effects on human health.

Comparative Evaluation of the Cytotoxic Effects of Metal Oxide and Metalloid Oxide Nanoparticles: An Experimental Study

Industrial production generates aerosols of complex composition, including an ultrafine fraction. This is typical for mining and metallurgical industries, welding processes, and the production and recycling of electronics, batteries, etc. Since nano-sized particles are the most dangerous component of inhaled air, in this study we aimed to establish the impact of the chemical nature and dose of nanoparticles on their cytotoxicity. Suspensions of CuO, PbO, CdO, Fe₂O₃, NiO, SiO₂, Mn₃O₄, and SeO nanoparticles were obtained by laser ablation. The experiments were conducted on outbred female albino rats. We carried out four series of a single intratracheal instillation of nanoparticles of different chemical natures at doses ranging from 0.2 to 0.5 mg per animal. Bronchoalveolar lavage was taken 24 h after the injection to assess its cytological and biochemical parameters. At a dose of 0.5 mg per animal, cytotoxicity in the series of nanoparticles changed as follows (in decreasing order): CuO NPs > PbO NPs > CdO NPs > NiO NPs > SiO₂ NPs > Fe₂O₃ NPs. At a lower dose of 0.25 mg per animal, we observed a different pattern of cytotoxicity of the element oxides under study: NiO NPs > Mn₃O₄ NPs > CuO NPs > SeO NPs. We established that the cytotoxicity increased non-linearly with the increase in the dose of nanoparticles of the same chemical element (from 0 to 0.5 mg per animal). An increase in the levels of intracellular enzymes (amylase, AST, ALT, LDH) in the supernatant of the bronchoalveolar lavage fluid indicated a cytotoxic effect of nanoparticles. Thus, alterations in the cytological parameters of the bronchoalveolar lavage and the biochemical characteristics of the supernatant can be used to predict the danger of new nanomaterials based on their comparative assessment with the available tested samples of nanoparticles.

Cadmium Through Disturbing MTF1-Mediated Metal Response Induced Cerebellar Injury

Cadmium (Cd) is a toxic environmental contaminant, which bio-accumulate in animals through the food chain. Cerebellum is one of the primary target organs for Cd exposure. In this study, we established a chronic Cd exposure model; 60 chickens were treated with Cd (0 mg/kg, 35 mg/kg, 70 mg/kg) for 90 days. Clinical manifestations indicated that the chicken was depressed and has unstable gait under Cd exposure. Histopathological results indicated that Cd induced neuronal shrunken and indistinct nucleoli, and the number of Purkinje cells decreased significantly. Cerebellar metal contents were analyzed by ICP-MS. We found that Cd caused Cd and Cu accumulation and decreased the content of Se, Fe, and Zn, suggesting that Cd disturbed metal homeostasis. Besides, Cd treatment group also showed high levels of malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) content and inhibited selenoprotein transcriptome, suggesting that Cd exposure resulted in oxidative stress. Notably, low-dose Cd exposure activated MTF1 mRNA and protein expression and its target metal-responsive genes, including MT1, MT2, DMT1, ZIP8, ZIP10, TF, and ATP7B which indicate cellular adaptive response against Cd-induced damage. On the other hand, 70 mg/kg Cd downregulated MTF1-mediated metal response, which was involved in Cd-induced cerebellar injury in chicken. In conclusion, our data demonstrated that molecular mechanisms are associated with Cd-induced cerebellar injury due to disturbing MTF1-mediated metal response.

Nanoparticle Effects on Stress Response Pathways and Nanoparticle-Protein Interactions

Nanoparticles (NPs) are increasingly used in a wide variety of applications and products; however, NPs may affect stress response pathways and interact with proteins in biological systems. This review article will provide an overview of the beneficial and detrimental effects of NPs on stress response pathways with a focus on NP-protein interactions. Depending upon the particular NP, experimental model system, and dose and exposure conditions, the introduction of NPs may have either positive or negative effects. Cellular processes such as the development of oxidative stress, the initiation of the inflammatory response, mitochondrial function, detoxification, and alterations to signaling pathways are all affected by the introduction of NPs. In terms of tissue-specific effects, the local microenvironment can have a profound effect on whether an NP is beneficial or harmful to cells. Interactions of NPs with metal-binding proteins (zinc, copper, iron and calcium) affect both their structure and function. This review will provide insights into the current knowledge of protein-based nanotoxicology and closely examines the targets of specific NPs.

Utility of Biogenic Iron and Its Bimetallic Nanocomposites for Biomedical Applications: A Review

Nanotechnology mainly deals with the production and application of compounds with dimensions in nanoscale. Given their dimensions, these materials have considerable surface/volume ratios, and hence, specific characteristics. Nowadays, environmentally friendly procedures are being proposed for fabrication of Fe nanoparticles because a large amount of poisonous chemicals and unfavorable conditions are needed to prepare them. This work includes an inclusive overview on the economical and green procedures for the preparation of such nanoparticles (flower, fruits, tea, carbohydrates, and leaves). Pure and bimetallic iron nanoparticles, for instance, offer a high bandwidth and excitation binding energy and are applicable in different areas ranging from antibacterial, anticancer, and bioimaging agents to drug delivery systems. Preparation of nano-sized particles, such as those of Fe, requires the application of high quantities of toxic materials and harsh conditions, and naturally, there is a tendency to develop more facile and even green pathways (Sultana, Journal of Materials Science & Technology, 2013, 29, 795–800; Bushra et al., Journal of hazardous materials, 2014, 264, 481–489; Khan et al., Ind. Eng. Chem. Res., 2015, 54, 76–82). This article tends to provide an overview on the reports describing green and biological methods for the synthesis of Fe nanoparticles. The present review mainly highlights selenium nanoparticles in the biomedical domain. Specifically, this review will present detailed information on drug delivery, bioimaging, antibacterial, and anticancer activity. It will also focus on procedures for their green synthesis methods and properties that make them potential candidates for various biomedical applications. Finally, we provide a detailed future outlook.

Copper oxide nanoparticles trigger macrophage cell death with misfolding of Cu/Zn superoxide dismutase 1 (SOD1)

Background

Copper oxide (CuO) nanoparticles (NPs) are known to trigger cytotoxicity in a variety of cell models, but the mechanism of cell death remains unknown. Here we addressed the mechanism of cytotoxicity in macrophages exposed to CuO NPs versus copper chloride (CuCl₂).

Methods

The mouse macrophage cell line RAW264.7 was used as an in vitro model. Particle uptake and the cellular dose of Cu were investigated by transmission electron microscopy (TEM) and inductively coupled plasma mass spectrometry (ICP-MS), respectively. The deposition of Cu in lysosomes isolated from macrophages was also determined by ICP-MS. Cell viability (metabolic activity) was assessed using the Alamar Blue assay, and oxidative stress was monitored by a variety of methods including a luminescence-based assay for cellular glutathione (GSH), and flow cytometry-based detection of mitochondrial superoxide and mitochondrial membrane potential. Protein aggregation was determined by confocal microscopy using an aggresome-specific dye and protein misfolding was determined by circular dichroism (CD) spectroscopy. Lastly, proteasome activity was investigated using a fluorometric assay.

Results

We observed rapid cellular uptake of CuO NPs in macrophages with deposition in lysosomes. CuO NP-elicited cell death was characterized by mitochondrial swelling with signs of oxidative stress including the production of mitochondrial superoxide and cellular depletion of GSH. We also observed a dose-dependent accumulation of polyubiquitinated proteins and loss of proteasomal function in CuO NP-exposed cells, and we could demonstrate misfolding and mitochondrial translocation of superoxide dismutase 1 (SOD1), a Cu/Zn-dependent enzyme that plays a pivotal role in the defense against oxidative stress. The chelation of copper ions using tetrathiomolybdate (TTM) prevented cell death whereas inhibition of the cellular SOD1 chaperone aggravated toxicity. Moreover, CuO NP-triggered cell death was insensitive to the pan-caspase inhibitor, zVAD-fmk, and to wortmannin, an inhibitor of autophagy, implying that this was a non-apoptotic cell death. ZnO NPs, on the other hand, triggered autophagic cell death.

Conclusions

CuO NPs undergo dissolution in lysosomes leading to copper-dependent macrophage cell death characterized by protein misfolding and proteasomal insufficiency. Specifically, we present novel evidence for Cu-induced SOD1 misfolding which accords with the pronounced oxidative stress observed in CuO NP-exposed macrophages. These results are relevant for our understanding of the consequences of inadvertent human exposure to CuO NPs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12989-022-00467-w.

Mechanisms of immune response to inorganic nanoparticles and their degradation products

Careful assessment of the biological fate and immune response of inorganic nanoparticles is crucial for use of such carriers in drug delivery and other biomedical applications. Many studies have elucidated the cellular and molecular mechanisms of the interaction of inorganic nanoparticles with the components of the immune system. The biodegradation and dissolution of inorganic nanoparticles can influence their ensuing immune response. While the immunological properties of inorganic nanoparticles as a function of their physicochemical properties have been investigated in detail, little attention has been paid to the immune adverse effects towards the degradation products of these nanoparticles. To fill this gap, we herein summarize the cellular mechanisms of immune response to inorganic nanoparticles and their degradation products with specific focus on immune cells. We also accentuate the importance of designing new methods and instruments for the in situ characterization of inorganic nanoparticles in order to assess their safety as a result of degradation. This review further sheds light on factors that need to be considered in the design of safe and effective inorganic nanoparticles for use in delivery of bioactive and imaging agents.

Cu-based nanoparticle toxicity to zebrafish cells regulated by cellular discharges

Cellular transport of metal nanoparticles (NPs) is critical in determining their potential toxicity, but the transformation of metal ions released from the internalized NPs is largely unknown. Cu-based NPs are the only metallic-based NPs that are reported to induce higher toxicity compared with their corresponding ions, likely due to their unique cellular turnover. In the present study, we developed a novel gold core to differentiate the particulate and ionic Cu in the Cu₂O microparticles (MPs), and the kinetics of bioaccumulation, exocytosis, and cytotoxicity of Au@Cu₂O MPs to zebrafish embryonic cells were subsequently studied. We demonstrated that the internalized MPs were rapidly dissolved to Cu ions, which then undergo lysosome-mediated exocytosis. The uptake rate of smaller MPs (130 nm) was lower than that of larger ones (200 nm), but smaller MPs were dissolved much quickly in cells and therefore activated the exocytosis more quickly. The rapid release of Cu ions resulted in an immediate toxic action of Cu₂O MPs, while the cell deaths mainly occurred by necrosis. During this process, the buffering ability of glutathione greatly alleviated the Cu toxicity. Therefore, although the turnover of intracellular Cu at a sublethal exposure level was hundred times faster than the basal values, labile Cu(I) concentration increased by only 2 times at most. Overall, this work provided new insights into the toxicity of copper NPs, suggesting that tolerance to Cu-based NPs depended on their ability to discharge the released Cu ions.

Development, formulation, and cellular mechanism of a lipophilic copper chelator for the treatment of Wilson's disease

Copper homeostasis is finely regulated in human to avoid any detrimental impact of free intracellular copper ions. Upon copper accumulation, biliary excretion is triggered in liver thanks to trafficking of the ATP7B copper transporter to bile canaliculi. However, in Wilson's disease this protein is mutated leading to copper accumulation. Current therapy uses Cu chelators acting extracellularly and requiring a life-long treatment with side effects. Herein, a new Cu(I) pro-chelator was encapsulated in long-term stable nanostructured lipid carriers. Cellular assays revealed that the pro-chelator protects hepatocytes against Cu-induced cell death. Besides, the cellular stresses induced by moderate copper concentrations, including protein unfolding, are counteracted by the pro-chelator. These data showed the pro-chelator efficiency to deliver intracellularly an active chelator that copes with copper stress and surpasses current and under development chelators. Although its biological activity is more mitigated, the pro-chelator nanolipid formulation led to promising results. This innovative approach is of outmost importance in the quest of better treatments for Wilson's disease.

Time dependent impact of copper oxide nanomaterials on the expression of genes associated with oxidative stress, metal binding, inflammation and mucus secretion in single and co-culture intestinal in vitro models

The potential for ingestion of copper oxide nanomaterials (CuO NMs) is increasing due to their increased exploitation. Investigation of changes in gene expression allows toxicity to be detected at an early stage of NM exposure and can enable investigation of the mechanism of toxicity. Here, undifferentiated Caco-2 cells, differentiated Caco-2 cells, Caco-2/HT29-MTX (mucus secreting) and Caco-2/Raji B (M cell model) co-cultures were exposed to CuO NMs and copper sulphate (CuSO₄) in order to determine their impacts. Cellular responses were measured in terms of production of reactive oxygen species (ROS), the gene expression of an antioxidant (haem oxygenase 1 (HMOX1)), the pro-inflammatory cytokine (interleukin 8 (IL8)), the metal binding (metallothionein 1A and 2A (MT1A and MT2A)) and the mucus secreting (mucin 2 (MUC2)), as well as HMOX-1 protein level. While CuSO₄ induced ROS production in cells, no such effect was observed for CuO NMs. However, these particles did induce an increase in the level of HMOX-1 protein and upregulation of HMOX1, MT2A, IL8 and MUC2 genes in all cell models. In conclusion, the expression of HMOX1, IL8 and MT2A were responsive to CuO NMs at 4 to 12 h post exposure when investigating the toxicity of NMs using intestinal in vitro models. These findings can inform the selection of endpoints, timepoints and models when investigating NM toxicity to the intestine in vitro in the future.

"Nanosize effect" in the metal-handling strategy of the bivalve Scrobicularia plana exposed to CuO nanoparticles and copper ions in whole-sediment toxicity tests

To date, the occurrence, fate and toxicity of metal-based NPs in the environment is under investigated. Their unique physicochemical, biological and optical properties, responsible for their advantageous application, make them intrinsically different from their bulk counterpart, raising the issue of their potential toxic specificity or "nanosize effect". The aim of this study was to investigate copper bioaccumulation, subcellular distribution and toxic effect in the marine benthic species Scrobicularia plana exposed to two forms of sediment-associated copper, as nanoparticles (CuO NPs) and as soluble ions (CuCl₂). Results showed that the exposure to different copper forms activated specific organism's metal handling strategies. Clams bioaccumulated soluble copper at higher concentrations than those exposed to sediment spiked with CuO NPs. Moreover, CuO NPs exposure elicited a stronger detoxification response mediated by a prompt mobilization of CuO NPs to metal-containing granules as well as a delayed induction of MT-like proteins, which conversely, sequestered soluble copper since the beginning of the exposure at levels significantly different from the control. Eventually, exposure to high concentrations of either copper form led to the same acute toxic effect (100% mortality) but the outcome was delayed in bivalves exposed to CuO NPs suggesting that the mechanisms underlying toxicity were copper form-specific. Indeed, while most of soluble copper was associated to the mitochondrial fraction suggesting an impairment of the ATP synthesis capacity at mitochondrial level, CuO NPs toxicity was most likely caused by the oxidative stress mediated by their bioaccumulation in the enzymatic and mitochondrial metabolically available fractions.

A novel assessment system of toxicity and stability of CuO nanoparticles via copper super sensitive Saccharomyces cerevisiae mutants

CuO nanoparticles (CuO-NPs) toxicity in organisms is contributed mainly through the copper uptake by both the ionic and nanoparticle form. However, the relative uptake ratio and bioavailability of the two different forms is not well known due to a lack of sensitive and effective assessment systems. We developed a series of both copper resistant and hyper sensitive Saccharomyces cerevisiae mutants to investigate and compare the effects of CuO-NPs and dissolved copper (CuCl₂), on the eukaryote with the purpose of quantitating the relative contributions of nanoparticles and dissolved species for Cu uptake. We observed the toxicity of 10 mM CuO-NPs for copper sensitive strains is equal to that of 0.5 mM CuCl₂ and the main toxic effect is most likely generated from oxidative stress through reactive oxygen species (ROS) production. About 95% CuO-NPs exist in nanoparticle form under neutral environmental conditions. Assessing the cellular metal content of wild type and copper transporter 1(CTR1) knock out cells showed that endocytosis is the major absorption style for CuO-NPs. This study also found a similar toxicity of Ag for both 10 mM Ag-NPs and 0.2 mM AgNO₃ in the copper super sensitive strains. Our study revealed the absorption mechanism of soluble metal based nanomaterials CuO-NPs and Ag-NPs as well as provided a sensitive and delicate system to precisely evaluate the toxicity and stability of nanoparticles.

Fabrication of monodispersed copper oxide nanoparticles with potential application as antimicrobial agents

Cuprous oxide nanoparticles (Cu2O NPs) were fabricated in reverse micellar templates by using lipopeptidal biosurfactant as a stabilizing agent. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive x-ray spectrum (EDX) and UV-Vis analysis were carried out to investigate the morphology, size, composition and stability of the nanoparticles synthesized. The antibacterial activity of the as-synthesized Cu2O NPs was evaluated against Gram-positive B. subtilis CN2 and Gram-negative P. aeruginosa CB1 strains, based on cell viability, zone of inhibition and minimal inhibitory concentration (MIC) indices. The lipopeptide stabilized Cu2O NPs with an ultra-small size of 30 ± 2 nm diameter exhibited potent antimicrobial activity against both Gram-positive and Gram-negative bacteria with a minimum inhibitory concentration of 62.5 µg/mL at pH5. MTT cell viability assay displayed a median inhibition concentration (IC50) of 21.21 μg/L and 18.65 μg/mL for P. aeruginosa and B. subtilis strains respectively. Flow cytometric quantification of intracellular reactive oxygen species (ROS) using 2,7-dichlorodihydrofluorescein diacetate staining revealed a significant ROS generation up to 2.6 to 3.2-fold increase in the cells treated with 62.5 µg/mL Cu2O NPs compared to the untreated controls, demonstrating robust antibacterial activity. The results suggest that lipopeptide biosurfactant stabilized Cu2O NPs could have promising potential for biocompatible bactericidal and therapeutic applications.

Effective recycling of Cu from electroplating wastewater effluent via the combined Fenton oxidation and hydrometallurgy route

Heavy metals, which commonly occur in complex forms, are difficult to remove in alkali electroplating wastewater effluent, and their resource recycling is rarely reported. Here, a Cu-bearing alkali wastewater effluent was effectively treated through Fenton oxidation, and the generated Fenton sludge was recycled into highly pure tenorite and hematite particles. The effluent contained 1.51 mg/L Cu and was subjected to Fenton oxidation, pH adjustment and coagulation. Amongst the three methods, Fenton oxidation showed superior efficiency to Cu removal, and the residual Cu in the effluent was 0.06 mg/L, thereby meeting the discharge standard for electroplating wastewater. However, Cu removal achieved less than 20% after pH adjustment and coagulation. Cu-bearing sludge, which was generated through the Fenton process, was dissolved in a mixture of hydrochloric and nitric acids. The dissolved solution contained 1.92 g/L Cu and 73.6 g/L Fe impurity. Impure Fe (67.4%) was removed as hematite aggregates after the solution was directly treated via a hydrometallurgy route, whilst 99.2% Cu was kept. When 0.5 mL of methanol was introduced to the hydrometallurgy system, nearly 100% Fe was removed as hematite nanoparticles with 94.8% purity, whilst more than 98% Cu was kept. The residual Cu was 1.88 g/L and precipitated as a tenorite block with a CuO content of 91.1% by adjusting the treated solution to pH 9. This study presented an environment-friendly method for enriching Cu from electroplating wastewater effluent without generating any waste.

Toxicity and Gene Expression Profiling of Copper- and Titanium-Based Nanoparticles Using Air-Liquid Interface Exposure

To assess the toxicity of nanomaterials, most in vitro studies have been performed under submerged conditions, which do not reflect physiological conditions upon inhalation. An air-liquid interface (ALI) exposure may provide more reliable data on dosimetry and prevent interactions with cell culture media components. Therefore, an ALI exposure was combined with a high-throughput RT-qPCR approach to evaluate the toxicological potential of CuO and TiO₂ nanoparticles (NP) in A549 cells. While TiO₂ NP did not show any cytotoxicity or other effects compromising genomic stability up to 25.8 μg/cm², CuO NP revealed a dose-dependent cytotoxicity, starting at 4.9 μg/cm². Furthermore, CuO NP altered distinct gene expression patterns indicative for disturbed metal homeostasis, stress response, and DNA damage induction. Thus, induction of metal homeostasis associated genes (MT1X, MT2A) at 0.4 μg/cm² and higher suggested uptake and intracellular dissolution of CuO NP, which was verified by a dose-dependent increase in intracellular copper concentration. Starting at 4.9 μg/cm², oxidative stress markers (HMOX1, HSPA1A) were induced dose-dependently, supported by elevated ROS levels. Furthermore, a dose-dependent induction of genes associated with DNA damage response (DDIT3, GADD45A) was observed, in concordance with an increase in DNA strand breaks. Finally, transcriptional data suggested the induction of apoptosis at high doses, while flow cytometric analysis revealed increased numbers of either late apoptotic or necrotic cells and clearly necrotic cells at the highest concentrations. Thus, an ALI cell culture system was successfully combined with a comprehensive high-throughput RT-qPCR system, allowing the quantification of NP deposition and their impact on genomic stability. For CuO NP, in principle the data confirm observations made under submerged conditions with respect to intracellular copper ion release, as well as oxidative and genotoxic stress response. However, the results derived from ALI exposure allow the assessment of dose-response-relationships as well as the comparison of relative toxic potencies of different NP.

Cupric Oxide Nanoparticles Induce Cellular Toxicity in Liver and Intestine Cell Lines

Purpose: The wide application of cupric oxide nanoparticles (copper (II) oxide, CuO-NPs) in various fields has increased exposure to the kind of active nanomaterials, which can cause negative effects on human and environment health. Although CuO-NPs were reported to be harmful to human, there is still a lack information related to their toxic potentials. In the present study, the toxic potentials of CuO-NPs were evaluated in the liver (HepG2 hepatocarcinoma) and intestine (Caco-2 colorectal adenocarcinoma) cells. Methods: After the characterization of particles, cellular uptake and morphological changes were determined. The potential of cytotoxic, genotoxic, oxidative and apoptotic damage was investigated with several in vitro assays. Results: The average size of the nanoparticles was 34.9 nm, about 2%-5% of the exposure dose was detected in the cells and mainly accumulated in different organelles, causing oxidative stress, cell damages, and death. The IC50 values were 10.90 and 10.04 µg/mL by MTT assay, and 12.19 and 12.06 µg/mL by neutral red uptake (NRU) assay, in HepG2 and Caco-2 cells respectively. Apoptosis assumes to the main cell death pathway; the apoptosis percentages were 52.9% in HepG2 and 45.5% in Caco-2 cells. Comet assay result shows that the highest exposure concentration (20 µg/mL) causes tail intensities about 9.6 and 41.8%, in HepG2 and Caco-2 cells, respectively. Conclusion: CuO-NPs were found to cause significant cytotoxicity, genotoxicity, and oxidative and apoptotic effects in both cell lines. Indeed, CuO-NPs could be dangerous to human health even if their toxic mechanisms should be elucidated with further studies.

Response of Cupriavidus basilensis B-8 to CuO nanoparticles enhances Cr(VI) reduction

CuO nanoparticles (NPs) released into aqueous environments induce metal toxicity, which generally exerts negative effects on various organisms and leads to great challenge for wastewater biotreatment. In this study, a promotion effect of CuO NPs on biological process was first found. Cr(VI) reduction by Cupriavidus basilensis B-8 (hereafter B-8) was enhanced in the presence of CuO NPs. The efficiency of Cr(VI) bioreduction was much higher with B-8 and CuO NPs (approximately 100%) than with B-8 (approximately 37.6%) and CuO NPs (39.9-44.7%) alone, indicating a stimulatory effect of CuO NPs on Cr(VI) reduction by B-8. Our material analyses revealed different response mechanisms of B-8 to Cr(VI), with and without CuO NPs. The addition of CuO NPs influenced the interaction of Cr(VI) with the N-, P-, S-, and C-related functional groups of B-8. Transcriptomic analysis indicated that multiple mechanisms, including Cr(VI) uptake and reactive oxygen species detoxification, were induced by Cr(VI). Many genes involved in various metabolic processes were significantly upregulated by the addition of CuO NPs. To a certain extent, the pressure of DNA repairment by B-8 induced by Cr(VI) was also alleviated by the presence of CuO NPs. They contributed to facilitate B-8 growth and enhance Cr(VI) reduction, even with 50 mg/L Cr(VI). This study not only elaborated the mechanisms of bacterial Cr(VI) reduction when enhanced by CuO NPs, but also provided a novel perspective for wastewater biotreatment.

More data on in vitro assessment of comparative and combined toxicity of metal oxide nanoparticles

Isolated and combined damaging effects of PbO and CuO nanoparticles were estimated on an established line of human fibroblasts by a decrease in: (a) the cellular dehydrogenase activity (MTT Assay), (b) the ATP content (Luminescent Cell Viability Assay), (c) the cellular proliferation, viability, spreading, and attachment to substrate evaluated integrally by continuous impedance-based measurement of the Normalized Cell Index. Using all these indices, we demonstrate an explicit dependence of cell damage on the concentrations of both metal oxide nanoparticle (MeO-NP) species. This dependence is adequately approximated with a hyperbolic function. At equal exposure levels, PbO-NP and CuO-NP demonstrate quantitatively similar cytotoxicities. The same was observed previously for some non-specific in vivo toxicity measures. The combined in vitro cytotoxicity has also been described mathematically using the Response Surface Methodology and found to be represented by various types, thus corroborating, in this respect also, the findings of a previous animal experiment with the same MeO-NPs.

Assessment of the structural reorganization of liver and biochemical parameters of blood serum after introduction of zinc nanoparticles and its oxides

The demand for nanoparticles of metals and their oxides in medicine and biology is indisputable. To ensure the safe use of the unique capabilities of nanostructures, in particular, essential metals and their oxides, and to further search for ways leveling side effects of toxic effects in biomedical applications, a multifaceted approach to the study of their properties is needed, primarily affecting the effects on the organism level. In this connection, the purpose of the present research was to study the effect of zinc nanoparticles (ZnNPs) and zinc oxide nanoparticles (ZnONPs) on structural reorganization of the liver and morpho-biochemical parameters of rat blood. The test substances exhibit a hepatotoxic effect upon their single intraperitoneal administration to rats. In the experiment, increased activity of gamma glutamyltransferase (GGT) and lactate dehydrogenase (LDH), increased expression of caspase-3, the presence of signs of oxidative stress, inflammation, and capillary-trophic insufficiency, and induction of tumor necrosis factor (TNF-α), and colony stimulating factor 2 (granulocyte-macrophage) (GM-CSF) were registered in the experiment. The level of interferon-γ in the experimental groups tended to decrease in comparison with the control group. The observed effects progressed in time, most noticeably manifested in the case of ZnONPs. Comparing the dosages, ZnNPs are less toxic than ZnONPs.

The most important inferences from the Ekaterinburg nanotoxicology team's animal experiments assessing adverse health effects of metallic and metal oxide nanoparticles

During 2009-2017 we have studied nanoparticles of elemental silver or gold and of iron, copper, nickel, manganese, lead, zinc, aluminium and titanium oxides (Me-NPs) using, in most cases, a single low-dose intratracheal instillation 24 h before the bronchoalveolar lavage to obtain a fluid for cytological and biochemical assessment and, in all cases, repeated intraperitoneal injections in non-lethal doses to induce subchronic intoxications assessed by a lot of toxicodynamic and toxicokinetic features. We have also studied the same effects for a number of relevant combinations of these Me-NPs and have revealed some important patterns of their combined toxicity. Besides, we have carried out long-term inhalation experiments with Fe2O3, NiO and amorphous SiO2 nano-aerosols. We have demonstrated that Me-NPs are much more noxious as compared with their fine micrometric counterparts although the physiological mechanisms of their elimination from the lungs proved to be highly active. Even if water-insoluble, Me-NPs are significantly solubilized in some biological milieus in vitro and in vivo, which may explain some important peculiarities of their toxicity. At the same time, the in situ cytotoxicity, organ-systemic toxicity and in vivo genotoxicity of Me-NPs strongly depends on specific mechanisms characteristic of a particular metal. For some of the Me-NPs studied, we have proposed standards of presumably safe concentrations in workplace air. Along with this, we have proved that the adverse effects of Me-NPs could be significantly alleviated by background or preliminary administration of adequately composed combinations of some bioprotectors.

Differential Contribution of Constituent Metal Ions to the Cytotoxic Effects of Fast-Dissolving Metal-Oxide Nanoparticles

The main mechanism of toxicity for fast-dissolving nanoparticles (NPs) is relatively simple as it originates from the intrinsic toxicity of their constituent elements rather than complicated surface reactivity. However, there is little information about the compared toxicity of fast-dissolving NP and its constituent ion, which is essential for understanding the mechanism of NP toxicity and the development of a structure-toxicity relationship (STR) model. Herein, we selected three types of fast-dissolving metal-oxide NPs (CoO, CuO, and ZnO) and constituent metal chlorides (CoCl₂, CuCl₂, and ZnCl₂) to compare dose-response curves between NP and its constituent metal. These materials were treated relevant cell lines for inhalation setting (i.e., differentiated THP-1 cells for macrophages and A549 cells for alveolar epithelial cells) and cytotoxicity as an endpoint was evaluated at 24 h post-incubation. The results showed that CoO and CuO NPs in both cell types showed similar patterns of dose-response curves and cytotoxic potential compared to that of their respective metal chloride. On the other hand, ZnO NPs in both cell types showed a completely different dose-response curve compared to that of ZnCl₂: ZnO NPs showed modest slope and much less potential for cytotoxicity compared to that of ZnCl₂. These results imply that fast-dissolving metal-oxide NPs are not always have similar dose-response curves and toxic potentials compared to their constituent metal chlorides and this may be due to the differential mechanism of intracellular uptake of these substances and their interaction with intracellular detoxification molecules. Further investigations are needed for the use of toxic potential of metal ions as a predicting factors of fast-dissolving NPs toxicity. In addition, chelating agent specific for dissolved metal ions can be applied for the treatment of these fast-dissolving NPs.

The Influence of Cigarette Smoke Exposure on the Copper Concentration in the Serum Depending on the Use of Menopausal Hormone Therapy

This study evaluated the effect of menopausal hormone therapy (MHT) on serum concentration of copper in postmenopausal women depending on passive or active exposure to tobacco smoke or lack thereof. The study included healthy postmenopausal women aged 42–69 years, who used (n = 76) or did not use (n = 76) MHT. Salivary cotinine and serum copper concentrations were determined in all the study subjects. Salivary cotinine exceeded 14 ng/ml in 14 women from the MHT group (18.5%) and in 16 controls (21.1%). Up to 41 (27%) study subjects had serum copper above the upper normal limit (1.17 mg/l). No correlation was found between salivary cotinine and serum copper in women with cotinine concentrations <14 ng/ml, and these two parameters correlated weakly in subjects with cotinine >14 ng/ml. Salivary concentration of cotinine increased with serum copper level in the MHT group, but not in the controls; smokers using MHT presented with significantly higher serum copper than nonsmokers. These findings imply that MHT does not affect serum concentration of copper in women who are not exposed to tobacco smoke. However, MHT seems to contribute to unfavorable increase in serum copper in passive and active smokers.

Textural, Structural and Biological Evaluation of Hydroxyapatite Doped with Zinc at Low Concentrations

The present work was focused on the synthesis and characterization of hydroxyapatite doped with low concentrations of zinc (Zn:HAp) (0.01 < x_Zn < 0.05). The incorporation of low concentrations of Zn²⁺ ions in the hydroxyapatite (HAp) structure was achieved by co-precipitation method. The physico-chemical properties of the samples were characterized by X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Scanning Electron Microscopy (SEM), zeta-potential, and DLS and N₂-BET measurements. The results obtained by XRD and FTIR studies demonstrated that doping hydroxyapatite with low concentrations of zinc leads to the formation of a hexagonal structure with lattice parameters characteristic to hydroxyapatite. The XRD studies have also shown that the crystallite size and lattice parameters of the unit cell depend on the substitutions of Ca²⁺ with Zn²⁺ in the apatitic structure. Moreover, the FTIR analysis revealed that the water content increases with the increase of zinc concentration. Furthermore, the Energy Dispersive X-ray Analysis (EDAX) and XPS analyses showed that the elements Ca, P, O, and Zn were found in all the Zn:HAp samples suggesting that the synthesized materials were zinc doped hydroxyapatite, Ca_10−xZn_x(PO₄)₆(OH), with 0.01 ≤ x_Zn ≤ 0.05. Antimicrobial assays on Staphylococcus aureus and Escherichia coli bacterial strains and HepG2 cell viability assay were carried out.

In vivo toxicity of copper oxide, lead oxide and zinc oxide nanoparticles acting in different combinations and its attenuation with a complex of innocuous bio-protectors

Stable suspensions of metal oxide nanoparticles (Me-NPs) obtained by laser ablation of 99.99% pure copper, zinc or lead under a layer of deionized water were used separately, in three binary combinations and a triple combination in two independent experiments on rats. In one of the experiments the rats were instilled with Me-NPs intratracheally (i.t.) (for performing a broncho-alveolar lavage in 24h to estimate the cytological and biochemical indices of the response of the lower airways), while in the other, Me-NPs were repeatedly injected intraperitoneally (i.p.) 18 times during 6 weeks (for estimating the accumulation of corresponding metals in the blood and their excretion with urine and feces and for assessing subchronic intoxication by a large number of functional and morphological indices). Mathematical description of the results from both experiments with the help of the Response Surface Methodology has shown that, as well as in the case of any other binary toxic combinations previously investigated by us, the response of the organism to a simultaneous exposure to any two of the Me-NPs under study is characterized by complex interactions between all possible types of combined toxicity (additivity, subadditivity or superadditivity of unidirectional action and different variants of opposite effects) depending on which effect it is estimated for as well as on the levels of the effect and dose. With any third Me-NP species acting in the background, the type of combined toxicity displayed by the other two may change significantly (as in the earlier described case of a triple combination of soluble metal salts). It is shown that various harmful effects produced by CuO-NP+ZnO-NP+PbO-NP combination may be substantially attenuated by giving rats per os a complex of innocuous bioactive substances theoretically expected to provide a protective integral and/or metal-specific effect during one month before i.t. instillation or during the entire period of i.p. injections.

Ecotoxicological effects and mechanism of CuO nanoparticles to individual organisms

Copper oxide nanoparticles (CuO NPs) are used extensively in a variety of applications such as antimicrobial agent, photo-catalyst and gas sensors. The expanding production and widespread utilization of CuO NPs may pose risks to individual organisms and ecosystem. Comprehensive understanding the CuO NPs-induced adverse effects and their underlying mechanism are of great importance to assess the environmental risk of CuO NPs and to expand their use safely. However, toxic effects of CuO NPs to individual organisms and the mechanism of their action are still deficient and ambiguities. To ensure the safely use of CuO NPs, more attention should be paid on the long-term and chronic effects of CuO NPs at low concentration. Efforts should be devoted to develop techniques to differentiate toxicities induced by CuO NPs or dissolved Cu²⁺, and to reduce the toxicity of CuO NPs by controlling the particle diameter, modifying surface characteristic, selecting proper exposure route and regulating the release of Cu²⁺ from CuO NPs. This review provides a brief overview of toxicity of CuO NPs to individual organisms with a broad range of taxa (microorganisms, algae, plants, invertebrates and vertebrates) and to discuss the underlying toxicity mechanisms including oxidative stress, dynamic unbalance and coordination effects.

Metal homeostasis disruption and mitochondrial dysfunction in hepatocytes exposed to sub-toxic doses of zinc oxide nanoparticles

Increased production and use of zinc oxide nanoparticles (ZnO-NPs) in consumer products has prompted the scientific community to investigate their potential toxicity, and understand their impact on the environment and organisms. Molecular mechanisms involved in ZnO-NP toxicity are still under debate and focus essentially on high dose expositions. In our study, we chose to evaluate the effect of sub-toxic doses of ZnO-NPs on human hepatocytes (HepG2) with a focus on metal homeostasis and redox balance disruptions. We showed massive dissolution of ZnO-NPs outside the cell, transport and accumulation of zinc ions inside the cell but no evidence of nanoparticle entry, even when analysed by high resolution TEM microscopy coupled with EDX. Gene expression analysis highlighted zinc homeostasis disruptions as shown by metallothionein 1X and zinc transporter 1 and 2 (ZnT1, ZnT2) over-expression. Major oxidative stress response genes, such as superoxide dismutase 1, 2 and catalase were not induced. Phase 2 enzymes in term of antioxidant response, such as heme oxygenase 1 (HMOX1) and the regulating subunit of the glutamate-cysteine ligase (GCLM) were slightly upregulated, but these observations may be linked solely to metal homeostasis disruptions, as these actors are involved in both metal and ROS responses. Finally, we observed abnormal mitochondria morphologies and autophagy vesicles in response to ZnO-NPs, indicating a potential role of mitochondria in storing and protecting cells from zinc excess but ultimately causing cell death at higher doses.

Visualization, quantification and coordination of Ag+ ions released from silver nanoparticles in hepatocytes

Silver nanoparticles (AgNPs) can enter eukaryotic cells and exert toxic effects, most probably as a consequence of the release of Ag⁺ ions. Due to the elusive nature of Ag⁺ ionic species, quantitative information concerning AgNP intracellular dissolution is missing. By using a synchrotron nanoprobe, silver is visualized and quantified in hepatocytes (HepG2) exposed to AgNPs; the synergistic use of electron microscopy allows for the discrimination between nanoparticular and ionic forms of silver within a single cell. AgNPs are located in endocytosis vesicles, while the visualized Ag⁺ ions diffuse in the cell. The averaged NP dissolution rates, measured by X-ray absorption spectroscopy, highlight the faster dissolution of citrate-coated AgNPs with respect to the less toxic PVP-coated AgNPs; these results are confirmed at the single-cell level. The released Ag⁺ ions recombine with thiol-bearing biomolecules: the Ag-S distances measured in cellulo, and the quantitative evaluation of gene expression, provide independent evidence of the involvement of glutathione and metallothioneins in Ag⁺ binding. The combined use of cutting-edge imaging techniques, atomic spectroscopy and molecular biology brings insight into the fate of AgNPs in hepatocytes, and more generally into the physicochemical transformations of metallic nanoparticles in biological environments and the resulting disruption of metal homeostasis.

Copper oxide nanoparticle toxicity profiling using untargeted metabolomics

BACKGROUND

The rapidly increasing number of engineered nanoparticles (NPs), and products containing NPs, raises concerns for human exposure and safety. With this increasing, and ever changing, catalogue of NPs it is becoming more difficult to adequately assess the toxic potential of new materials in a timely fashion. It is therefore important to develop methods which can provide high-throughput screening of biological responses. The use of omics technologies, including metabolomics, can play a vital role in this process by providing relatively fast, comprehensive, and cost-effective assessment of cellular responses. These techniques thus provide the opportunity to identify specific toxicity pathways and to generate hypotheses on how to reduce or abolish toxicity.

RESULTS

We have used untargeted metabolome analysis to determine differentially expressed metabolites in human lung epithelial cells (A549) exposed to copper oxide nanoparticles (CuO NPs). Toxicity hypotheses were then generated based on the affected pathways, and critically tested using more conventional biochemical and cellular assays. CuO NPs induced regulation of metabolites involved in oxidative stress, hypertonic stress, and apoptosis. The involvement of oxidative stress was clarified more easily than apoptosis, which involved control experiments to confirm specific metabolites that could be used as standard markers for apoptosis; based on this we tentatively propose methylnicotinamide as a generic metabolic marker for apoptosis.

CONCLUSIONS

Our findings are well aligned with the current literature on CuO NP toxicity. We thus believe that untargeted metabolomics profiling is a suitable tool for NP toxicity screening and hypothesis generation.

Comparative proteomic analysis of the molecular responses of mouse macrophages to titanium dioxide and copper oxide nanoparticles unravels some toxic mechanisms for copper oxide nanoparticles in macrophages

Titanium dioxide and copper oxide nanoparticles are more and more widely used because of their catalytic properties, of their light absorbing properties (titanium dioxide) or of their biocidal properties (copper oxide), increasing the risk of adverse health effects. In this frame, the responses of mouse macrophages were studied. Both proteomic and targeted analyses were performed to investigate several parameters, such as phagocytic capacity, cytokine release, copper release, and response at sub toxic doses. Besides titanium dioxide and copper oxide nanoparticles, copper ions were used as controls. We also showed that the overall copper release in the cell does not explain per se the toxicity observed with copper oxide nanoparticles. In addition, both copper ion and copper oxide nanoparticles, but not titanium oxide, induced DNA strands breaks in macrophages. As to functional responses, the phagocytic capacity was not hampered by any of the treatments at non-toxic doses, while copper ion decreased the lipopolysaccharide-induced cytokine and nitric oxide productions. The proteomic analyses highlighted very few changes induced by titanium dioxide nanoparticles, but an induction of heme oxygenase, an increase of glutathione synthesis and a decrease of tetrahydrobiopterin in response to copper oxide nanoparticles. Subsequent targeted analyses demonstrated that the increase in glutathione biosynthesis and the induction of heme oxygenase (e.g. by lovastatin/monacolin K) are critical for macrophages to survive a copper challenge, and that the intermediates of the catecholamine pathway induce a strong cross toxicity with copper oxide nanoparticles and copper ions.

Some inferences from in vivo experiments with metal and metal oxide nanoparticles: the pulmonary phagocytosis response, subchronic systemic toxicity and genotoxicity, regulatory proposals, searching for bioprotectors (a self-overview)

The purpose of this paper is to overview and summarize previously published results of our experiments on white rats exposed to either a single intratracheal instillation or repeated intraperitoneal injections of silver, gold, iron oxide, copper oxide, nickel oxide, and manganese oxide nanoparticles (NPs) in stable water suspensions without any chemical additives. Based on these results and some corroborating data of other researchers we maintain that these NPs are much more noxious on both cellular and systemic levels as compared with their 1 μm or even submicron counterparts. However, within the nanometer range the dependence of systemic toxicity on particle size is intricate and non-unique due to complex and often contra-directional relationships between the intrinsic biological aggressiveness of the specific NPs, on the one hand, and complex mechanisms that control their biokinetics, on the other. Our data testify to the high activity of the pulmonary phagocytosis of NPs deposited in airways. This fact suggests that safe levels of exposure to airborne NPs are possible in principle. However, there are no reliable foundations for establishing different permissible exposure levels for particles of different size within the nanometric range. For workroom air, such permissible exposure levels of metallic NP can be proposed at this stage, even if tentatively, based on a sufficiently conservative approach of decreasing approximately tenfold the exposure limits officially established for respective micro-scale industrial aerosols. It was shown that against the background of adequately composed combinations of some bioactive agents (comprising pectin, multivitamin-multimineral preparations, some amino acids, and omega-3 polyunsaturated fatty acid) the systemic toxicity and even genotoxicity of metallic NPs could be markedly attenuated. Therefore we believe that, along with decreasing NP-exposures, enhancing organisms’ resistance to their adverse action with the help of such bioprotectors can prove an efficient auxiliary tool of health risk management in occupations connected with them.

Some characteristics of free cell population in the airways of rats after intratracheal instillation of copper-containing nano-scale particles

We used stable water suspensions of copper oxide particles with mean diameter 20 nm and of particles containing copper oxide and element copper with mean diameter 340 nm to assess the pulmonary phagocytosis response of rats to a single intratracheal instillation of these suspensions using optical, transmission electron, and semi-contact atomic force microscopy and biochemical indices measured in the bronchoalveolar lavage fluid. Although both nano and submicron ultrafine particles were adversely bioactive, the former were found to be more toxic for lungs as compared with the latter while evoking more pronounced defense recruitment of alveolar macrophages and especially of neutrophil leukocytes and more active phagocytosis. Based on our results and literature data, we consider both copper solubilization and direct contact with cellular organelles (mainly, mitochondria) of persistent particles internalized by phagocytes as probable mechanisms of their cytotoxicity.

Activation of Erk and p53 regulates copper oxide nanoparticle-induced cytotoxicity in keratinocytes and fibroblasts

Copper oxide nanoparticles (CuONP) have attracted increasing attention due to their unique properties and have been extensively utilized in industrial and commercial applications. For example, their antimicrobial capability endows CuONP with applications in dressings and textiles against bacterial infections. Along with the wide applications, concerns about the possible effects of CuONP on humans are also increasing. It is crucial to evaluate the safety and impact of CuONP on humans, and especially the skin, prior to their practical application. The potential toxicity of CuONP to skin keratinocytes has been reported recently. However, the underlying mechanism of toxicity in skin cells has remained unclear. In the present work, we explored the possible mechanism of the cytotoxicity of CuONP in HaCaT human keratinocytes and mouse embryonic fibroblasts (MEF). CuONP exposure induced viability loss, migration inhibition, and G₂/M phase cycle arrest in both cell types. CuONP significantly induced mitogen-activated protein kinase (extracellular signal-regulated kinase [Erk], p38, and c-Jun N-terminal kinase [JNK]) activation in dose- and time-dependent manners. U0126 (an inhibitor of Erk), but not SB 239063 (an inhibitor of p38) or SP600125 (an inhibitor of JNK), enhanced CuONP-induced viability loss. CuONP also induced decreases in p53 and p-p53 levels in both cell types. Cyclic pifithrin-α, an inhibitor of p53 transcriptional activity, enhanced CuONP-induced viability loss. Nutlin-3α, a p53 stabilizer, prevented CuONP-induced viability loss in HaCaT cells, but not in MEF cells, due to the inherent toxicity of nutlin-3α to MEF. Moreover, the experiments on primary keratinocytes are in accordance with the conclusions acquired from HaCaT and MEF cells. These data demonstrate that the activation of Erk and p53 plays an important role in CuONP-induced cytotoxicity, and agents that preserve Erk or p53 activation may prevent CuONP-induced cytotoxicity.

Subchronic toxicity of copper oxide nanoparticles and its attenuation with the help of a combination of bioprotectors

In the copper metallurgy workplace air is polluted with condensation aerosols, which a significant fraction of is presented by copper oxide particles<100 nm. In the scientific literature, there is a lack of their in vivo toxicity characterization and virtually no attempts of enhancing organism's resistance to their impact. A stable suspension of copper oxide particles with mean (±SD) diameter 20±10 nm was prepared by laser ablation of pure copper in water. It was being injected intraperitoneally to rats at a dose of 10 mg/kg (0.5 mg per mL of deionized water) three times a week up to 19 injections. In parallel, another group of rats was so injected with the same suspension against the background of oral administration of a "bio-protective complex" (BPC) comprising pectin, a multivitamin-multimineral preparation, some amino acids and fish oil rich in ω-3 PUFA. After the termination of injections, many functional and biochemical indices for the organism's status, as well as pathological changes of liver, spleen, kidneys, and brain microscopic structure were evaluated for signs of toxicity. In the same organs we have measured accumulation of copper while their cells were used for performing the Random Amplification of Polymorphic DNA (RAPD) test for DNA fragmentation. The same features were assessed in control rats infected intraperitoneally with water with or without administration of the BPC. The copper oxide nanoparticles proved adversely bio-active in all respects considered in this study, their active in vivo solubilization in biological fluids playing presumably an important role in both toxicokinetics and toxicodynamics. The BPC proposed and tested by us attenuated systemic and target organs toxicity, as well as genotoxicity of this substance. Judging by experimental data obtained in this investigation, occupational exposures to nano-scale copper oxide particles can present a significant health risk while the further search for its management with the help of innocuous bioprotectors seems to be justified.