Cytotoxicity and apoptotic effects of nickel oxide nanoparticles in cultured HeLa cells

Developing Benign Ni/g-C3N4 Catalysts for CO2 Hydrogenation: Activity and Toxicity Study

This research discusses the CO2 valorization via hydrogenation over the non-noble metal clusters of Ni and Cu supported on graphitic carbon nitride (g-C3N4). The Ni and Cu catalysts were characterized by conventional techniques including XRD, AFM, ATR, Raman imaging, and TPR and were tested via the hydrogenation of CO2 at 1 bar. The transition-metal-based catalyst designed with atom-economy principles presents stable activity and good conversions for the studied processes. At 1 bar, the rise in operating temperature during CO2 hydrogenation increases the CO2 conversion and the selectivity for CO and decreases the selectivity for methanol on Cu/CN catalysts. For the Ni/CN catalyst, the selectivity to light hydrocarbons, such as CH4, also increased with rising temperature. At 623 K, the conversion attained ca. 20%, with CH4 being the primary product of the reaction (CH4 yield >80%). Above 700 K, the Ni/CN activity increases, reaching almost equilibrium values, although the Ni loading in Ni/CN is lower by more than 90% compared to the reference NiREF catalyst. The presented data offer a better understanding of the effect of the transition metals' small metal cluster and their coordination and stabilization within g-C3N4, contributing to the rational hybrid catalyst design with a less-toxic impact on the environment and health. Bare g-C3N4 is shown as a good support candidate for atom-economy-designed catalysts for hydrogenation application. In addition, cytotoxicity to the keratinocyte human HaCaT cell line revealed that low concentrations of catalysts particles (to 6.25 μg mL-1) did not cause degenerative changes.

Review and Evaluation of the Potential Health Effects of Oxidic Nickel Nanoparticles

The exceptional physical and chemical properties of nickel nanomaterials have been exploited in a range of applications such as electrical conductors, batteries, and biomaterials. However, it has been suggested that these unique properties may allow for increased bioavailability, bio-reactivity, and potential adverse health effects. Thus, the purpose of this review was to critically evaluate data regarding the toxicity of oxidic nickel nanoparticles (nickel oxide (NiO) and nickel hydroxide (Ni(OH)2) nanoparticles) with respect to: (1) physico-chemistry properties; (2) nanomaterial characterization in the defined delivery media; (3) appropriateness of model system and translation to potential human effects; (4) biodistribution, retention, and clearance; (5) routes and relevance of exposure; and (6) current research data gaps and likely directions of future research. Inhalation studies were prioritized for review as this represents a potential exposure route in humans. Oxidic nickel particle size ranged from 5 to 100 nm in the 60 studies that were identified. Inflammatory responses induced by exposure of oxidic nickel nanoparticles via inhalation in rodent studies was characterized as acute in nature and only displayed chronic effects after relatively large (high concentration and long duration) exposures. Furthermore, there is no evidence, thus far, to suggest that the effects induced by oxidic nickel nanoparticles are related to preneoplastic events. There are some data to suggest that nano- and micron-sized NiO particles follow a similar dose response when normalized to surface area. However, future experiments need to be conducted to better characterize the exposure-dose-response relationship according to specific surface area and reactivity as a dose metric, which drives particle dissolution and potential biological responses.

Looking for the LOAEL or NOAEL Concentration of Nickel-Oxide Nanoparticles in a Long-Term Inhalation Exposure of Rats

Rats were exposed to nickel oxide nano-aerosol at a concentration of 2.4 ± 0.4 µg/m³ in a “nose only” inhalation setup for 4 h at a time, 5 times a week, during an overall period of 2 weeks to 6 months. Based on the majority of the effects assessed, this kind of exposure may be considered as close to LOAEL (lowest observed adverse effect level), or even to NOAEL (no observed adverse effect level). At the same time, the experiment revealed genotoxic and allergic effects as early as in the first weeks of exposure, suggesting that these effects may have no threshold at all.

Toxic Effects of Low-Level Long-Term Inhalation Exposures of Rats to Nickel Oxide Nanoparticles

Rats were exposed to nickel oxide nanoparticles (NiO-NP) inhalation at 0.23 ± 0.01 mg/m³ for 4 h a day 5 times a week for up to 10 months. The rat organism responded to this impact with changes in cytological and some biochemical characteristics of the bronchoalveolar lavage fluid along with a paradoxically little pronounced pulmonary pathology associated with a rather low chronic retention of nanoparticles in the lungs. There were various manifestations of systemic toxicity, including damage to the liver and kidneys; a likely allergic syndrome as indicated by some cytological signs; transient stimulation of erythropoiesis; and penetration of nickel into the brain from the nasal mucous membrane along the olfactory pathway. Against a picture of mild to moderate chronic toxicity of nickel, its in vivo genotoxic effect assessed by the degree of DNA fragmentation in nucleated blood cells (the RAPD test) was pronounced, tending to increasing with the length of the exposure period. When rats were given orally, in parallel with the toxic exposure, a set of innocuous substances with differing mechanisms of expected bioprotective action, the genotoxic effect of NiO-NPs was found to be substantially attenuated.

Cationic Substitutions in Hydroxyapatite: Current Status of the Derived Biofunctional Effects and Their In Vitro Interrogation Methods

High-performance bioceramics are required for preventing failure and prolonging the life-time of bone grafting scaffolds and osseous implants. The proper identification and development of materials with extended functionalities addressing socio-economic needs and health problems constitute important and critical steps at the heart of clinical research. Recent findings in the realm of ion-substituted hydroxyapatite (HA) could pave the road towards significant developments in biomedicine, with an emphasis on a new generation of orthopaedic and dentistry applications, since such bioceramics are able to mimic the structural, compositional and mechanical properties of the bone mineral phase. In fact, the fascinating ability of the HA crystalline lattice to allow for the substitution of calcium ions with a plethora of cationic species has been widely explored in the recent period, with consequent modifications of its physical and chemical features, as well as its functional mechanical and in vitro and in vivo biological performance. A comprehensive inventory of the progresses achieved so far is both opportune and of paramount importance, in order to not only gather and summarize information, but to also allow fellow researchers to compare with ease and filter the best solutions for the cation substitution of HA-based materials and enable the development of multi-functional biomedical designs. The review surveys preparation and synthesis methods, pinpoints all the explored cation dopants, and discloses the full application range of substituted HA. Special attention is dedicated to the antimicrobial efficiency spectrum and cytotoxic trade-off concentration values for various cell lines, highlighting new prophylactic routes for the prevention of implant failure. Importantly, the current in vitro biological tests (widely employed to unveil the biological performance of HA-based materials), and their ability to mimic the in vivo biological interactions, are also critically assessed. Future perspectives are discussed, and a series of recommendations are underlined.

Nano NiO induced liver toxicity via activating the NF-κB signaling pathway in rats

Studies have demonstrated that nano NiO could induce liver toxicity in rats, but its mechanism remains unclear. This study aimed to explore the role of the NF-κB signaling pathway in rat liver toxicity after nano NiO exposure. Male Wistar rats were exposed to nano NiO (0.015, 0.06 and 0.24 mg per kg b.w.) and micro NiO (0.24 mg per kg b.w.) by intratracheal instillation twice a week for 6 weeks. To investigate the liver toxicity induced by nano NiO, the indicators of liver function and inflammatory response were detected, and the histopathological changes were observed. The levels of NF-κB signaling pathway related gene and protein expression were examined using RT-qPCR and western blot techniques in the liver tissue. The results showed that the activities of alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP) and gamma-glutamyltranspeptidase (GGT) increased after nano NiO exposure. Cellular edema, hepatic sinus disappearance, and neutrophil and lymphocyte infiltration were observed. Nano NiO increased the concentrations of pro-inflammatory cytokines (IL-1β and IL-6), but decreased the levels of anti-inflammatory cytokines (IL-4 and IL-10). It also induced the upregulation of TNF-α, NF-κB-inducible kinase (NIK), IκB kinase alpha (IKK-α) and NF-κB mRNA, while inducing the downregulation of the inhibitor kappa B (IκB) alpha. In addition, we found that the protein content of NIK, IKK-α, p-IKK-α, p-IκB-α and NF-κB was elevated, whereas that of IκB-α was reduced. The results indicated that the NF-κB signaling pathway played an important role in rat liver toxicity induced by nano NiO.

The Developmental Toxicity of Complex Silica-Embedded Nickel Nanoparticles Is Determined by Their Physicochemical Properties

Complex engineered nanomaterials (CENs) are a rapidly developing class of structurally and compositionally complex materials that are expected to dominate the next generation of functional nanomaterials. The development of methods enabling rapid assessment of the toxicity risk associated with this type of nanomaterial is therefore critically important. We evaluated the toxicity of three differently structured nickel-silica nanomaterials as prototypical CENs: simple, surface-deposited Ni-SiO2 and hollow and non-hollow core-shell Ni@SiO2 materials (i.e., ~1-2 nm Ni nanoparticles embedded into porous silica shells with and without a central cavity, respectively). Zebrafish embryos were exposed to these CENs, and morphological (survival and malformations) and physiological (larval motility) endpoints were coupled with thorough characterization of physiochemical characteristics (including agglomeration, settling and nickel ion dissolution) to determine how toxicity differed between these CENs and equivalent quantities of Ni2+ salt (based on total Ni). Exposure to Ni2+ ions strongly compromised zebrafish larva viability, and surviving larvae showed severe malformations. In contrast, exposure to the equivalent amount of Ni CEN did not result in these abnormalities. Interestingly, exposure to Ni-SiO2 and hollow Ni@SiO2 provoked abnormalities of zebrafish larval motor function, indicating developmental toxicity, while non-hollow Ni@SiO2 showed no toxicity. Correlating these observations with physicochemical characterization of the CENs suggests that the toxicity of the Ni-SiO2 and hollow Ni@SiO2 material may result partly from an increased effective exposure at the bottom of the well due to rapid settling. Overall, our data suggest that embedding nickel NPs in a porous silica matrix may be a straightforward way to mitigate their toxicity without compromising their functional properties. At the same time, our results also indicate that it is critical to consider modification of the effective exposure when comparing different nanomaterial configurations, because effective exposure might influence NP toxicity more than specific "nano-chemistry" effects.

In vitro and in vivo evaluation of the toxicities induced by metallic nickel nano and fine particles

Nickel nanoparticles (Ni NPs) have been applied in various fields along with the rapid development of nanotechnology. However, the potential adverse health effects of the Ni NPs are unclear. To investigate the cyto- and genotoxicity and compare the differences between the Ni NPs and the nickel fine particles (Ni FPs), Sprague-Dawley (SD) rats and A549 cells were treated with different doses of Ni NPs or FPs. Intra-tracheal instillation of Ni NPs and FPs caused acute toxicity in the lungs, liver and kidneys of the SD rats. Even though the histology of the lungs showed hyperplastic changes and the protein expression of HO-1 and Nrf2 detected by western blot showed lung burden overload, no significant increase was observed to the expression level of oncoprotein C-myc. The results from cell titer-Glo assay and comet assay indicated that Ni NPs were more potent in causing cell toxicity and genotoxicity in vitro than Ni FPs. In addition, Ni NPs increased the expression of C-myc in vitro, but these increases may not have been due to oxidative stress since no significant dose-dependent changes were seen in HO-1 and Nrf2 expressions. Although Ni NPs have the potential to cause DNA damage in A549 cells in vitro, the molecular mechanisms that led to these changes and their tumorigenic potential is still debatable. In short, Ni NPs were more potent in causing cell toxicity and genotoxicity in vitro than Ni FPs, and intra-tracheal instillation of Ni NPs and FPs caused toxicity in organs of the SD rats, while it showed similar to the effects for both particle types. These results suggested that both Ni NPs and FPs have the potential to be harmful to human health, and Ni NPs may have higher cyto- and genotoxic effects than Ni FPs under the same treatment dose.

In vitro and in vivo evaluation of the toxicities induced by metallic nickel nano and fine particles

Nickel nanoparticles (Ni NPs) have been applied in various fields along with the rapid development of nanotechnology. However, the potential adverse health effects of the Ni NPs are unclear. To investigate the cyto- and genotoxicity and compare the differences between the Ni NPs and the nickel fine particles (Ni FPs), Sprague-Dawley (SD) rats and A549 cells were treated with different doses of Ni NPs or FPs. Intra-tracheal instillation of Ni NPs and FPs caused acute toxicity in the lungs, liver and kidneys of the SD rats. Even though the histology of the lungs showed hyperplastic changes and the protein expression of HO-1 and Nrf2 detected by western blot showed lung burden overload, no significant increase was observed to the expression level of oncoprotein C-myc. The results from cell titer-Glo assay and comet assay indicated that Ni NPs were more potent in causing cell toxicity and genotoxicity in vitro than Ni FPs. In addition, Ni NPs increased the expression of C-myc in vitro, but these increases may not have been due to oxidative stress since no significant dose-dependent changes were seen in HO-1 and Nrf2 expressions. Although Ni NPs have the potential to cause DNA damage in A549 cells in vitro, the molecular mechanisms that led to these changes and their tumorigenic potential is still debatable. In short, Ni NPs were more potent in causing cell toxicity and genotoxicity in vitro than Ni FPs, and intra-tracheal instillation of Ni NPs and FPs caused toxicity in organs of the SD rats, while it showed similar to the effects for both particle types. These results suggested that both Ni NPs and FPs have the potential to be harmful to human health, and Ni NPs may have higher cyto- and genotoxic effects than Ni FPs under the same treatment dose.