Cell viability and cytotoxicity assays: Biochemical elements and cellular compartments

Cell viability and cytotoxicity assays play a crucial role in drug screening and evaluating the cytotoxic effects of various chemicals. The quantification of cell viability and proliferation serves as the cornerstone for numerous in vitro assays that assess cellular responses to external factors. In the last decade, several studies have developed guidelines for defining and interpreting cell viability and cytotoxicity based on morphological, biochemical, and functional perspectives. As this domain continues to experience ongoing growth, revealing new mechanisms orchestrating diverse cell cytotoxicity pathways, we suggest a revised classification for multiple assays employed in evaluating cell viability and cell death. This classification is rooted in the cellular compartment and/or biochemical element involved, with a specific focus on mechanistic and essential aspects of the process. The assays are founded on diverse cell functions, encompassing metabolic activity, enzyme activity, cell membrane permeability and integrity, adenosine 5'-triphosphate content, cell adherence, reduction equivalents, dye inclusion or exclusion, constitutive protease activity, colony formation, DNA fragmentation and nuclear splitting. These assays present straightforward, reliable, sensitive, reproducible, cost-effective, and high-throughput approaches for appraising the effects of newly formulated chemotherapeutic biomolecules on the cell survival during the drug development process.

Mechanistic Approach on the Pulmonary Oxido-Inflammatory Stress Induced by Cobalt Ferrite Nanoparticles in Rats

Cobalt ferrite nanoparticles (CFN) are employed in data storage, imaging, medication administration, and catalysis due to their superparamagnetic characteristics. The widespread use of CFN led to significantly increased exposure to people and the environment to these nanoparticles. Until now, there is not any published paper describing the adverse effect of repeated oral intake of this nanoformulation on rats' lungs. So, the current research aims to elucidate the pulmonary toxicity prompted by different concentrations of CFN in rats as well as to explore the mechanistic way of such toxicity. We used 28 rats that were divided equally into 4 groups. The control group received normal saline, and the experimental groups received CFN at dosage levels 0.05, 0.5, and 5 mg/kg bwt. Our findings revealed that CFN enhanced dose-dependent oxidative stress manifested by raising in the MDA levels and declining in the GSH content. The histopathological examination revealed interstitial pulmonary inflammation along with bronchial and alveolar damage in both 0.5 and 5 mg CFN given groups. All these lesions were confirmed by the immunohistochemical staining that demonstrated strong iNOS and Cox-2 protein expression. There was also a significant upregulation of TNFα, Cox-2, and IL-1β genes with downregulation of IL-10 and TGF-β genes. Additionally, the group receiving 0.05 mg CFN did not exhibit any considerable toxicity in all measurable parameters. We concluded that the daily oral intake of either 0.5 or 5 mg CFN, but not 0.05 mg, could induce pulmonary toxicity via NPs and/or its leached components (cobalt and iron)-mediated oxido-inflammatory stress. Our findings may help to clarify the mechanisms of pulmonary toxicity generated by these nanoparticles through outlining the standards for risk assessment in rats as a human model.

Nanotoxicity of multifunctional stoichiometric cobalt oxide nanoparticles (SCoONPs) with repercussions toward apoptosis, necrosis, and cancer necrosis factor (TNF-α) at nano-biointerfaces

Introduction

Apoptosis, necrosis, and cancer necrosis factor (TNF-a) are all impacted by the nanotoxicity of multifunctional stoichiometric cobalt oxide nanoparticles (SCoONPs) at nano-biointerfaces. The creation of multi-functional nanoparticles has had a considerable impact on the transport of drugs and genes, nanotheranostics (in-vivo imaging, concurrent diagnostics), interventions for external healing, the creation of nano-bio interfaces, and the instigation of desired changes in nanotherapeutics.

Objectives

The quantitative structure-activity relationships, chemical transformations, biological interactions as well as toxicological analyses are considered as main objectives. Discrete dimensions of SCoNPs-cell interaction interfaces, their characteristic physical features (size, shape, shell structure, and surface chemistry), impact on cell proliferation and differentiation are the key factors responsible for nanotoxicity.

Methods

The development of multi-functional nanoparticles has been significant in drug/gene delivery, nanotheranostics (in-vivo imaging, coinciding diagnostics), and external healing interventions, designing a nano-bio interface, as well as inciting desired alterations in nanotherapeutics. Every so often, the cellular uptake of multi-functional cobalt [Co, CoO, Co2(CO)8 and Co3O4] nanoparticles (SCoONPs) influences cellular mechanics and initiates numerous repercussions (oxidative stress, DNA damage, cytogenotoxicity, and chromosomal damage) in pathways, including the generation of dysregulating factors involved in biochemical transformations.

Results

The concerns and influences of multifunctional SCoNPs on different cell mechanisms (mitochondria impermeability, hydrolysis of ATP, the concentration of Ca2+, impaired calcium clearance, defective autophagy, apoptosis, and necrosis), and interlinked properties (adhesion, motility, and internalization dynamics, role in toxicity, surface hydrophilic and hydrophobicity, biokinetics and biomimetic behaviors of biochemical reactions) have also been summarized. SCoONPs have received a lot of interest among the nanocarriers family because of its advantageous qualities such as biodegradability, biocompatibility, nontoxicity, and nonimmunogenicity.

Conclusion

Various applications, such as bio-imaging, cell labeling, gene delivery, enhanced chemical stability, and increased biocompatibility, concerning apoptosis, necrosis, and nano-bio interfaces, along with suitable examples. In this analysis, the multi-functional cobalt [Co, CoO, Co2(CO)8 and Co3O4] nanoparticles (SCoNPs) intricacies (cytogenotoxicity, clastogenicity, and immunomodulatory), nanotoxicity, and associated repercussions have been highlighted and explained.

The colony forming efficiency assay for toxicity testing of nanomaterials—Modifications for higher-throughput

To cope with the high number of nanomaterials manufactured, it is essential to develop high-throughput methods for in vitro toxicity screening. At the same time, the issue with interference of the nanomaterial (NM) with the read-out or the reagent of the assay needs to be addressed to avoid biased results. Thus, validated label-free methods are urgently needed for hazard identification of NMs to avoid unintended adverse effects on human health. The colony forming efficiency (CFE) assay is a label- and interference-free method for quantification of cytotoxicity by cell survival and colony forming efficiency by CFE formation. The CFE has shown to be compatible with toxicity testing of NMs. Here we present an optimized protocol for a higher-throughput set up.

Engineered nanoparticles toxicity on adipose tissue derived mesenchymal stem cells: A preliminary investigation

Nanoscience and nanotechnologies have recently gained importance in several fields, such as industry and medicine. A big issue of the increasing application of nanomaterials is the poor literature regarding their potential toxicity in humans and animals. Recently, adult stem cells have been proposed as putative targets of nanoparticles (NPs). This study aims to investigate the effects of zerovalent-metallic NPs on isolated and amplified equine Adipose tissue derived Mesenchymal Stem Cells (eAdMSCs). Cells were treated with Cobalt (Co-), Iron (Fe-), and Nickel (Ni-) nanoparticles (NPs) at different concentrations and were characterized for the cytotoxic and genotoxic effects of exposure. Treatment with NPs resulted in reduced cell viability and proliferative capability in comparison with untreated cells. However, this did not influence eAdMSCs potency, as treated cells were able to differentiate towards the adipogenic and osteogenic lineages. Ni- and Fe-NPs showed cytoplasmic localization, while Co-NPs entered the nucleus and mitochondria, suggesting a potential genotoxic activity. Regarding p53 expression, it was enhanced in the first 48 h after treatments, with a drastic reduction of expression within 72 h. Higher p53 expression was reported in the case of Co-NP treatment, suggesting the tumorigenic potential of these NPs. Telomerase activity was enhanced by Fe- and Ni-NP treatments in a concentration- and time-dependent way. This was not true for Co-NP treated samples, suggesting a reduced replicative capacity of eAdMSCs upon Co-NP exposure. The present study is a preliminary investigation of the influence exerted by NPs on eAdMSC physiological activity in terms of cytotoxic and genotoxic effects. The present results revealed eAdMSC physiology to be strongly influenced by NPs in a dose-, time- and NP-dependent way.

Genotoxic Potential of Nanoparticles: Structural and Functional Modifications in DNA

The rapid advancement of nanotechnology enhances the production of different nanoparticles that meet the demand of various fields like biomedical sciences, industrial, material sciences and biotechnology, etc. This technological development increases the chances of nanoparticles exposure to human beings, which can threaten their health. It is well known that various cellular processes (transcription, translation, and replication during cell proliferation, cell cycle, cell differentiation) in which genetic materials (DNA and RNA) are involved play a vital role to maintain any structural and functional modification into it. When nanoparticles come into the vicinity of the cellular system, chances of uptake become high due to their small size. This cellular uptake of nanoparticles enhances its interaction with DNA, leading to structural and functional modification (DNA damage/repair, DNA methylation) into the DNA. These modifications exhibit adverse effects on the cellular system, consequently showing its inadvertent effect on human health. Therefore, in the present study, an attempt has been made to elucidate the genotoxic mechanism of nanoparticles in the context of structural and functional modifications of DNA.

Risk Assessment of Oxidative Stress Induced by Metal Ions Released from Fixed Orthodontic Appliances during Treatment and Indications for Supportive Antioxidant Therapy: A Narrative Review

The treatment with fixed orthodontic appliances could have an important role in the induction of oxidative stress and associated negative consequences. Because of the simultaneous effects of corrosion, deformation, friction, and mechanical stress on fixed orthodontic appliances during treatment, degradation of orthodontic brackets and archwires occurs, causing higher concentrations of metal ions in the oral cavity. Corroded appliances cause the release of metal ions, which may lead to the increased values of reactive oxygen species (ROS) due to metal-catalyzed free radical reactions. Chromium, iron, nickel, cobalt, titanium, and molybdenum all belong to the group of transition metals that can be subjected to redox reactions to form ROS. The estimation of health risk due to the amount of heavy metals released and the level of selected parameters of oxidative stress generated for the time of treatment with fixed orthodontic appliances is presented. Approaches to avoid oxidative stress and recommendations for the preventive use of topical or systemic antioxidants during orthodontic treatment are discussed.

Nanomaterials as drug delivery systems with antibacterial properties: current trends and future priorities

Introduction:Despite extensive advances in the production and synthesis of antibiotics, infectious diseases are one of the main problems of the 21st century due to multidrug-resistant (MDR) distributing in organisms. Therefore, researchers in nanotechnology have focused on new strategies to formulate and synthesis the different types of nanoparticles (NPs) with antimicrobial properties.Areas covered:The present review focuses on nanoparticles which are divided into two groups, organic (micelles, liposomes, polymer-based and lipid-based NPs) and inorganic (metals and metal oxides). NPs can penetrate the cell wall then destroy permeability of cell membrane, the structure and function of cell macromolecules by producing of reactive oxygen species (ROS) and eventually kill the bacteria. Moreover, their characteristics and mechanism in various bacteria especially MDR bacteria and finally their biocompatibility and the factors affecting their activity have been discussed.Expert opinion:Nanotechnology has led to higher drug absorption, targeted drug delivery and fewer side effects. NPs can overcome MDR through affecting several targets in the bacteria cell and synergistically increase the effectiveness of current antibiotics. Moreover, organic NPs with regard to their biodegradability and biocompatibility characteristics can be suitable agents for medical applications. However, they are less stable in environment in comparison to inorganic NPs.

Adverse Outcome Pathway Development for Assessment of Lung Carcinogenicity by Nanoparticles

Lung cancer, one of the most common and deadly forms of cancer, is in some cases associated with exposure to certain types of particles. With the rise of nanotechnology, there is concern that some engineered nanoparticles may be among such particles. In the absence of epidemiological evidence, assessment of nanoparticle carcinogenicity is currently performed on a time-consuming case-by-case basis, relying mainly on animal experiments. Non-animal alternatives exist, including a few validated cell-based methods accepted for regulatory risk assessment of nanoparticles. Furthermore, new approach methodologies (NAMs), focused on carcinogenic mechanisms and capable of handling the increasing numbers of nanoparticles, have been developed. However, such alternative methods are mainly applied as weight-of-evidence linked to generally required animal data, since challenges remain regarding interpretation of the results. These challenges may be more easily overcome by the novel Adverse Outcome Pathway (AOP) framework, which provides a basis for validation and uptake of alternative mechanism-focused methods in risk assessment. Here, we propose an AOP for lung cancer induced by nanosized foreign matter, anchored to a selection of 18 standardized methods and NAMs for in silico- and in vitro-based integrated assessment of lung carcinogenicity. The potential for further refinement of the AOP and its components is discussed in relation to available nanosafety knowledge and data. Overall, this perspective provides a basis for development of AOP-aligned alternative methods-based integrated testing strategies for assessment of nanoparticle-induced lung cancer.

Toxicological effects of different-sized Co-Fe (CoFe2O4) nanoparticles on Lepidium sativum L.: towards better understanding of nanophytotoxicity

Due to their widespread therapeutic and agricultural applicability and usefulness in removing metals and metalloids from water, cobalt ferrite nanoparticles (NPs) are currently receiving increasing attention from researchers. However, their potential phytotoxicity is still poorly understood. Thus, the aim of the current study was to assess the effects of synthesized cobalt ferrite (CoFe₂O₄) NPs on biological (morphological, physiological, and biochemical) parameters of edible plant garden-cress (Lepidium sativum L.), depending on particle size and concentrations. In this study, physical characteristics of cobalt ferrite NPs were determined. Increased total content of Co and Fe in L. sativum tissues and their transfer from roots to above-ground parts of seedlings, which depended on the size of NP (15 < 5 < 1.65 nm), indicated that plants had been exposed to Co ferrite NPs. The relative growth of roots, biomass of roots and above-ground parts of seedlings, amounts of chlorophylls a and b, carotenoids, and malondialdehyde (MDA) were determined. The dependence of the tested garden-cress parameters on the size and concentrations of NPs was revealed. Our data showed that the content of MDA in test plants in some cases increased up to 2.5 folds in comparison to control. The increase of the content of chlorophyll b pigment and MDA in test plants is an appropriate indicator of the impact of cobalt ferrite NPs. The findings of our study into toxicological effects of Co-Fe (CoFe₂O₄) NPs on L. sativum are expected to deepen the knowledge of the nanophytotoxicity of ferromagnetic NPs and their potential application in biomedicine and agriculture.

Research progress on the carcinogenicity of metal nanomaterials

With the rapid development of nanotechnology, new nanomaterials with enormous potentials continue to emerge, especially metal nanomaterials. Metal nanomaterials possess the characteristics of metals and nanomaterials, so they are widely used in many fields. But at the same time, whether the use or release of metal nan4omaterials into the environment is toxic to human beings and animals has now attained widespread attention at home and abroad. Currently, it is an indisputable fact that cancer ranks among the top causes of death among residents worldwide. The properties of causing DNA damage and mutations possessed by these metal nanomaterials make them unpredictable influences in the body, subsequently leading to genotoxicity and carcinogenicity. Due to the increasing evidence of their roles in carcinogenicity, this article reviews the toxicological and carcinogenic effects of metal nanomaterials, including nano-metal elements (nickel nanoparticles, silver nanoparticles, and cobalt nanoparticles) and nano-metal oxides (titanium dioxide nanoparticles, silica nanoparticles, zinc oxide nanoparticles, and alumina nanoparticles). This article provides a reference for the researchers and policymakers to use metal nanomaterials rationally in modern industries and biomedicine.

Cobalt oxide nanoparticles induce oxidative stress and alter electromechanical function in rat ventricular myocytes

Background

Nanotoxicology is an increasingly relevant field and sound paradigms on how inhaled nanoparticles (NPs) interact with organs at the cellular level, causing harmful conditions, have yet to be established. This is particularly true in the case of the cardiovascular system, where experimental and clinical evidence shows morphological and functional damage associated with NP exposure. Giving the increasing interest on cobalt oxide (Co₃O₄) NPs applications in industrial and bio-medical fields, a detailed knowledge of the involved toxicological effects is required, in view of assessing health risk for subjects/workers daily exposed to nanomaterials. Specifically, it is of interest to evaluate whether NPs enter cardiac cells and interact with cell function. We addressed this issue by investigating the effect of acute exposure to Co₃O₄-NPs on excitation-contraction coupling in freshly isolated rat ventricular myocytes.

Results

Patch clamp analysis showed instability of resting membrane potential, decrease in membrane electrical capacitance, and dose-dependent decrease in action potential duration in cardiomyocytes acutely exposed to Co₃O₄-NPs. Motion detection and intracellular calcium fluorescence highlighted a parallel impairment of cell contractility in comparison with controls. Specifically, NP-treated cardiomyocytes exhibited a dose-dependent decrease in the fraction of shortening and in the maximal rate of shortening and re-lengthening, as well as a less efficient cytosolic calcium clearing and an increased tendency to develop spontaneous twitches. In addition, treatment with Co₃O₄-NPs strongly increased ROS accumulation and induced nuclear DNA damage in a dose dependent manner. Finally, transmission electron microscopy analysis demonstrated that acute exposure did lead to cellular internalization of NPs.

Conclusions

Taken together, our observations indicate that Co₃O₄-NPs alter cardiomyocyte electromechanical efficiency and intracellular calcium handling, and induce ROS production resulting in oxidative stress that can be related to DNA damage and adverse effects on cardiomyocyte functionality.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12989-020-00396-6.

Evaluation of the Effects of Particle Sizes of Silver Nanoparticles on Various Biological Systems

Seven biological methods were adopted (three bacterial activities of bioluminescence, enzyme, enzyme biosynthetic, algal growth, seed germination, and root and shoot growth) to compare the toxic effects of two different sizes of silver nanoparticles (AgNPs). AgNPs showed a different sensitivity in each bioassay. Overall, the order of inhibitory effects was roughly observed as follows; bacterial bioluminescence activity ≈ root growth > biosynthetic activity of enzymes ≈ algal growth > seed germination ≈ enzymatic activity > shoot growth. For all bacterial activities (bioluminescence, enzyme, and enzyme biosynthesis), the small AgNPs showed statistically significantly higher toxicity than the large ones (p < 0.0036), while no significant differences were observed among other biological activities. The overall effects on the biological activities (except shoot growth) of the small AgNPs were shown to have about 4.3 times lower EC50 (high toxicity) value than the large AgNPs. These results also indicated that the bacterial bioluminescence activity appeared to be an appropriate method among the tested ones in terms of both sensitivity and the discernment of particle sizes of AgNPs.

Synthesis of Cobalt Hydroxide Nano-flakes Functionalized with Glutamic Acid and Conjugated with Thiosemicarbazide for Anticancer Activities Against Human Breast Cancer Cells

In recent years, researchers were attracted to nanomaterials components for their potential role in cancer treatment. This study aimed to develop a novel and biocompatible cobalt hydroxide (Co(OH)₂) nano-flakes that is functionalized by glutamic acid (Glu) and conjugated to thiosemicarbazide (TSC) for anticancer activities against human breast cancer MCF-7 cells. Physico-chemical properties of the Co(OH)₂@Glu-TSC nanomaterial are characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX) analysis, and Fourier-transform infrared (FT-IR) spectroscopy. MTT assay, flow cytometry, and caspase-3 activity analysis used for evaluating anticancer properties of the Co(OH)₂@Glu-TSC nanomaterial. The MTT assay result showed cellular uptake of Co(OH)₂@Glu-TSC and cell viability loss in a concentration-dependent. Results of flow cytometry and caspase-3 activity analysis indicated the stimulation of apoptosis through an increase in Caspase-3 and nucleus fragmentation. In general, our findings indicate the anticancer activities of Co(OH)₂@Glu-TSC nanomaterial and so it can be considered as a new treatment for breast cancer. However, further in vivo studies are required to evaluate the accumulation of Co(OH)₂@Glu-TSC nanomaterial in healthy organs, such as the liver, kidneys, brain, and testes, and potential toxic effects.

Exposure of synthesized Co3O4 nanoparticles to Chlorella minutissima: An ecotoxic evaluation in freshwater microalgae

The current study focuses on the ecotoxicity of cobalt oxide nanoparticles (Co₃O₄ NPs) in the aquatic environment towards freshwater microalgae, Chlorella minutissima. The interaction of Co₃O₄ NPs with microalgae shows the growth suppressing effect. The 72 h EC ₅₀ (effective concentration of a chemical having 50% of its impact) values of Co₃O₄ NPs for C. minutissima was 38.16 ± 1.99 mg/L. The decline in chlorophyll a content and increase in reactive oxygen species (ROS) also indicated the compromised physiological state of microalgae. An increased LDH (lactate dehydrogenase) level in treated samples suggests membrane disintegration by Co₃O₄ NPs. Light microscopy, scanning electron microscopy (SEM) and Energy Dispersive X-Ray-Scanning electron microscopy (EDX-SEM) further confirm cell entrapment and deposition of Co₃O₄ NPs on the cell surface. Cellular internalization of NPs, as shown by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), also contributes towards the toxicity of NPs. The findings suggest the role of extracellular as well as intracellular nanoparticles (NPs) in exerting a toxic effect on the C. minutissima.

Evaluating genotoxicity of metal oxide nanoparticles: Application of advanced supervised and unsupervised machine learning techniques

Presence of missing data points in datasets is among main challenges in handling the toxicological data for nanomaterials. As the processing of missing data is an important part of data analysis, we have introduced a read-across approach that uses a combination of supervised and unsupervised machine learning techniques to fill the missing values. A series of classification models (supervised learning) was developed to predict class label, and self-organizing map approach (unsupervised learning) was used to estimate relative distances between nanoparticles and refine results obtained during supervised learning. In this study, genotoxicity of 49 silicon and metal oxide nanoparticles in Ames and Comet tests. Collected literature data did not demonstrate significant variations related to the change of size including selected bulk materials. Genotoxicity-related features of nanomaterials were represented by ionic characteristics. General tendencies found in the current study were convincingly linked to known theories of genotoxic action at nano-level. Mechanisms of primary and secondary genotoxic effects were discussed in the context of developed models.

Redox interactions and genotoxicity of metal-based nanoparticles: A comprehensive review

Nanotechnology is a growing science that may provide several new applications for medicine, food preservation, diagnostic technologies, and sanitation. Despite its beneficial applications, there are several questions related to the safety of nanomaterials for human use. The development of nanotechnology is associated with some concerns because of the increased risk of carcinogenesis following exposure to nanomaterials. The increased levels of reactive oxygen species (ROS) that are due to exposure to nanoparticles (NPs) are primarily responsible for the genotoxicity of metal NPs. Not all, but most metal NPs are able to directly produce free radicals through the release of metal ions and through interactions with water molecules. Furthermore, the increased production of free radicals and the cell death caused by metal NPs can stimulate reduction/oxidation (redox) reactions, leading to the continuous endogenous production of ROS in a positive feedback loop. The overexpression of inflammatory mediators, such as NF-kB and STATs, the mitochondrial malfunction and the increased intracellular calcium levels mediate the chronic oxidative stress that occurs after exposure to metal NPs. In this paper, we review the genotoxicity of different types of metal NPs and the redox mechanisms that amplify the toxicity of these NPs.

Genotoxicity Assessment of Nanomaterials: Recommendations on Best Practices, Assays, and Methods

Nanomaterials (NMs) present unique challenges in safety evaluation. An international working group, the Genetic Toxicology Technical Committee of the International Life Sciences Institute's Health and Environmental Sciences Institute, has addressed issues related to the genotoxicity assessment of NMs. A critical review of published data has been followed by recommendations on methods alterations and best practices for the standard genotoxicity assays: bacterial reverse mutation (Ames); in vitro mammalian assays for mutations, chromosomal aberrations, micronucleus induction, or DNA strand breaks (comet); and in vivo assays for genetic damage (micronucleus, comet and transgenic mutation assays). The analysis found a great diversity of tests and systems used for in vitro assays; many did not meet criteria for a valid test, and/or did not use validated cells and methods in the Organization for Economic Co-operation and Development Test Guidelines, and so these results could not be interpreted. In vivo assays were less common but better performed. It was not possible to develop conclusions on test system agreement, NM activity, or mechanism of action. However, the limited responses observed for most NMs were consistent with indirect genotoxic effects, rather than direct interaction of NMs with DNA. We propose a revised genotoxicity test battery for NMs that includes in vitro mammalian cell mutagenicity and clastogenicity assessments; in vivo assessments would be added only if warranted by information on specific organ exposure or sequestration of NMs. The bacterial assays are generally uninformative for NMs due to limited particle uptake and possible lack of mechanistic relevance, and are thus omitted in our recommended test battery for NM assessment. Recommendations include NM characterization in the test medium, verification of uptake into target cells, and limited assay-specific methods alterations to avoid interference with uptake or endpoint analysis. These recommendations are summarized in a Roadmap guideline for testing.

Protein corona formation and its constitutional changes on magnetic nanoparticles in serum featuring a polydehydroalanine coating: effects of charge and incubation conditions

The inevitable formation of a protein corona upon contact of nanoparticles with different biological fluids is of great interest in the context of biomedical applications. It is well established that the surface chemistry of the respective nanomaterial has tremendous impact on protein adsorption, both in terms of the actual amount as well as the type of proteins adsorbed. In that regard, especially polyzwitterions are discussed as coating materials as they are known to partially inhibit protein adsorption. We herein present comparative incubation studies on iron oxide nanoparticles (either single core (SPION) or multicore nanoparticles (MCNP)) after coating with either polyanionic or polyzwitterionic polymeric shells based on polydehydroalanine (PDha). Apart from varying surface charge and chemistry, also the influence of incubation time and temperature on the formation and composition of a protein corona upon exposure to fetal calf serum was investigated. The amounts of adsorbed biomolecules were determined using thermogravimetric analysis. SDS-PAGE experiments revealed information on protein composition as major components of the biomolecule corona. Our results show that distinctly lower amounts of proteins are adsorbed onto polyzwitterionic hybrid nanoparticles in general, but also the corona composition varies as indicated by elevated relative ratios of medium molecular weight proteins (i.e. proteins 25-100 kDa) estimated by non-specific silver protein staining. In addition, increasing relative amounts of albumin (67 kDa) via specific Western blot assays on PDha-coated MCNP are detected.

Synthesis of novel pyrazole incorporating a coumarin moiety (PC) for selective and sensitive Co2+ detection

An efficient regioselective synthesis of a novel pyrazole derivative containing a coumarin moiety was achieved, which was electrodeposited as PC/Nafion/GCE sensor probe to detect the selective Co²⁺ ions for the safety of environment and healthcare fields.

Cytotoxicity of Iron (III), Molybdenum (III), and their Mixtures in BALB/3T3 and HepG2 Cells

Introduction

Iron and molybdenum are essential trace elements for cell metabolism. They are involved in maintaining proper functions of enzymes, cell proliferation, and metabolism of DNA.

Material and Methods

BALB/3T3 and HepG2 cells were incubated with iron chloride or molybdenum trioxide at concentrations from 100 to 1,400 μM. The cells were also incubated in mixtures of iron chloride at 200 μM plus molybdenum trioxide at 1,000 μM or iron chloride at 1,000 μM plus molybdenum trioxide at 200 μM. Cell viability was determined with MTT reduction, LHD release, and NRU tests.

Results

A decrease in cell viability was observed after incubating both cell lines with iron chloride or molybdenum trioxide. In cells incubated with mixtures of these trace elements, a decrease in cell viability was observed, assessed by all the used assays.

Conclusion

Iron (III) and molybdenum (III) decrease cell viability in normal and cancer cells. A synergistic effect of the mixture of these elements was observed.

Co3O4 nanoparticles at sublethal concentrations inhibit cell growth by impairing mitochondrial function

Co₃O₄ nanoparticles (NPs) are one kind of the important nanomaterials that have the application potential in catalyst, electrochromic devices, sensors, etc. However, their biological effect remains to be detailed. In this study, we investigated the effect of the as-synthesized Co₃O₄ NPs (15-30 nm) on the growth of mammalian cells, and found that the NPs severely inhibited cell growth at the sublethal concentrations from 12.5 to 200 mg/L. Interestingly, the NPs did not cause obvious cell death and ROS accumulation, indicating that their inhibitory effect was not attributed to both apoptosis- or necrosis-related cell death and ROS accumulation. Transcription profiling analysis revealed that the NPs caused remarkable down regulation of the genes involved in mitochondrial functions. Transmission electron microscopy (TEM) and biochemical analysis further showed that the NPs might interact with the mitochondria, impairing the mitochondrial membrane potential (MMP) and ATP production. This study uncovers a mitochondrial respiratory chain-related and ROS-independent toxicity mechanism of Co₃O₄ NPs in eukaryotic cells.

Differential toxicity of processed and non-processed states of CoCrMo degradation products generated from a hip simulator on neural cells

Physico-chemical characteristics of the CoCrMo degradation products have played an important role in cytotoxicity and clinical complications on the orthopedic patients who have metal implants. Previous studies have limited reflection on the physicochemical characteristics of the degradation products generated in vivo, which are very different from individual metal particles and/or ions obtained from different commercial sources. In this study, we aimed to understand the differences in toxicity induced by the degradation products in as-synthesized form as well as those obtained after post-processing. The degradation products were generated using a hip-simulator by maintaining physiological conditions closer to in vivo and separated into two batches, one with processing by washing and drying called processed degradation products (PDP) and another batch as 'as-synthesized' degradation product (DP). We studied the dose-dependent toxicity response by neural cells derived from induced pluripotent stem cells. The results of the study show that as-synthesized DPs are more toxic to neural cells even at lower concentrations studied with evident low TC50 (1-5 μg/ml) concentrations compared to PDP (25 μg/ml). Flow cytometric analysis showed a significant (p<.01) increase in uptake of the particles after 24 h and corresponding ROS production in DP-treated cells. RT-PCR analysis of oxidative specific gene expression showed, elevated mRNA levels of NADPH oxidase-1, nuclear transcription factor, superoxide dismutase-2 and glutaredoxin-2 in DP-treated cells after 6 h. The results of the study provided a clear evidence of the differential response of neural cells on the degradation products as a function of concentrations and their chemical nature.

Cobalt and nickel impair DNA metabolism by the oxidative stress independent pathway

The oxidative stress that evolves under cobalt and nickel exposure is thought to exert toxicity, though the exact routes of such metal poisoning remain ambiguous. We revisited the metal toxicity in Escherichia coli to show that cobalt and nickel exposure at levels as low as 0.5 and 1 mM, respectively, visibly inhibits growth. We also observed that acidic conditions aggravated, while alkaline conditions alleviated the metal toxicity. Besides, 1 mM manganese, which is non-cytotoxic, as judged by the growth of E. coli, synergistically elevated cobalt and nickel stress. However, the metal toxicity did not lead to oxidative stress in E. coli. On the other hand, we show that cobalt and nickel, but not manganese, reduced the rate of DNA replication to 50% within 2 hours. Interestingly, the metal ions promoted DNA double-strand breaks but did not induce SOS repair pathways, indicating that the metal ions could block SOS induction. To test this, we show that cobalt and nickel, but not manganese, suppressed the nalidixic acid-induced SOS response. Finally, using an in vitro assay system, we demonstrated that cobalt and nickel inhibit RecBCD function, which is essential for SOS induction. Therefore, our data indicate that cobalt and nickel affect DNA replication, damage DNA, and inhibit the SOS repair pathway to exert toxicity.

Interactions between chromium(III) and iron(III), molybdenum(III) or nickel(II): Cytotoxicity, genotoxicity and mutagenicity studies

The aim of this study was to examine the effect of chromium(III) and iron(III) and molybdenum(III) and nickel(II) and their combinations on cyto-, genotoxicity and mutagenicity in BALB/3T3 and HepG2 cells. The results obtained from cytotoxicity assays indicate that there are differences between BALB/3T3 and HepG2 cell lines in their sensitivity to chromium chloride, iron chloride, molybdenum trioxide and nickel chloride. The statistically significant increase of DNA damage of all used microelements in both cell lines was observed. The micronucleus assay performed with the use of all concentrations shows statistically significant induction of chromosomal aberrations in all tested microelements in both cell lines. Moreover, treated cells display characteristic apoptosis in comparison to control cells. In all tested microelements, the increase of number of reverse mutations was observed with and without metabolic activation. Additions of Cr(III) at 200 μM plus Fe(III) at 1000 μM showed synergistic effect in decrease of cell viability and increase of comets, micronuclei and number of revertants in both cell lines. In case of Cr(III) at 200 μM plus Mo(III) at 1000 μM, a protective effect of chromium against molybdenum at 1000 μM toxicity in both cell lines (assessed by MTT, LDH and NRU, comet, micronucleus and Ames assays) was observed. The protective effect of Cr(III) in decrease of cell viability was observed in pair of Cr(III) at 200 μM and Ni(II) at 1000 μM in BALB/3T3 and HepG2 cell lines assessed by MTT, LDH and NRU, comet, micronucleus and Ames assays.

Systemic and local toxicity of metal debris released from hip prostheses: A review of experimental approaches

Despite the technological improvements in orthopedic joint replacement implants, wear and corrosion products associated with the metal components of these implants may result in adverse local tissue and perhaps systemic reactions and toxicities. The current review encompasses a literature review of the local and systemic toxicity studies concerning the effect of CoCrMo wear debris released from wear and corrosion of orthopedic implants and prostheses. Release of metallic debris is mainly in the form of micro- and nano-particles, ions of different valences, and oxides composed of Co and Cr. Though these substances alter human biology, their direct effects of these substances on specific tissue types remain poorly understood. This may partially be the consequence of the multivariate research methodologies employed, leading to inconsistent reports. This review proposes the importance of developing new and more appropriate in-vitro methodologies to study the cellular responses and toxicity mediated by joint replacement wear debris in-vivo.

Palladium Nanoparticles: Toxicological Effects and Potential Implications for Occupational Risk Assessment

The increasing technological applications of palladium nanoparticles (Pd-NPs) and their consequent enhancing release into the community and occupational environments, have raised public health concerns regarding possible adverse effects for exposed subjects, and particularly for workers chronically and highly exposed to these materials, whose toxico-kinetic and dynamic behavior remains to be fully understood. Therefore, this review aimed to critically analyze literature data to achieve a more comprehensive knowledge on the toxicological profile of Pd-NPs. Results from available studies demonstrated the potential for these chemicals to affect the ecosystem function, to exert cytotoxic and pro-inflammatory effects in vitro as well as to induce early alterations in different target organs in in vivo models. However, our revision pointed out the need for future studies aimed to clarify the role of the NP physico-chemical properties in determining their toxicological behavior, as well as the importance to carry out investigations focused on environmental and biological monitoring to verify and validate experimental biomarkers of exposure and early effect in real exposure contexts. Overall, this may be helpful to support the definition of suitable strategies for the assessment, communication and management of Pd-NP occupational risks to protect the health and safety of workers.

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.

Can zinc protect cells from the cytotoxic effects of cobalt ions and nanoparticles derived from metal-on-metal joint arthroplasties?

Objectives

Recently, high failure rates of metal-on-metal (MOM) hip implants have raised concerns of cobalt toxicity. Adverse reactions occur to cobalt nanoparticles (CoNPs) and cobalt ions (Co²⁺) during wear of MOM hip implants, but the toxic mechanism is not clear.

Methods

To evaluate the protective effect of zinc ions (Zn²⁺), Balb/3T3 mouse fibroblast cells were pretreated with 50 μM Zn²⁺ for four hours. The cells were then exposed to different concentrations of CoNPs and Co²⁺ for four hours, 24 hours and 48 hours. The cell viabilities, reactive oxygen species (ROS) levels, and inflammatory cytokines were measured.

Results

CoNPs and Co²⁺ can induce the increase of ROS and inflammatory cytokines, such as tumour necrosis factor α (TNF-α), interleukin-1β (IL-1β) and interleukin-6 (IL-6). However, Zn pretreatment can significantly prevent cytotoxicity induced by CoNPs and Co²⁺, decrease ROS production, and decrease levels of inflammatory cytokines in Balb/3T3 mouse fibroblast cells.

Conclusion

These results suggest that Zn pretreatment can provide protection against inflammation and cytotoxicity induced by CoNPs and Co²⁺ in Balb/3T3 cells.

Cite this article: Y. Liu, H. Zhu, H. Hong, W. Wang, F. Liu. Can zinc protect cells from the cytotoxic effects of cobalt ions and nanoparticles derived from metal-on-metal joint arthroplasties? Bone Joint Res 2017;6:649–655. DOI: 10.1302/2046-3758.612.BJR-2016-0137.R2.

Morphological transformation induced by silver nanoparticles in a Balb/c 3T3 A31-1-1 mouse cell model to evaluate in vitro carcinogenic potential

Carcinogenesis is a complex process involved in genotoxic and non-genotoxic pathways. The carcinogenic potential of silver nanoparticles (AgNPs) has been predicted by examining their genotoxic effects using several in vitro and in vivo models. However, there is no little information regarding the non-genotoxic effects of AgNPs related to carcinogenesis. The in vitro cell transformation assay (CTA) provides specific and sensitive evidence for predicting the tumorigenic potential of a chemical, which cannot be obtained by genotoxicity testing. Therefore, we carried out CTA in Balb/c 3T3 A31-1-1 cells to evaluate the carcinogenic potential of AgNPs. Colony-forming efficiency and crystal violet assays were carried out to determine the cytotoxicity of AgNPs. A cytokinesis-block micronucleus (CBMN) assay and CTA were performed using Balb/c 3T3 A31-1-1 cells to predict the in vitro carcinogenic potential of AgNPs. In the CBMN assay, AgNPs (10.6 μg/mL) induced a significant increase in micronucleus formation indicating a genotoxic effect. Thus, AgNPs could be an initiator of carcinogenesis. In the CTA, used to assess the carcinogenic potential of AgNPs, cells exposed to AgNPs for 72 hours showed significantly induced morphological neoplastic transformation at all tested doses (0.17, 0.66, 2.65, 5.30, and 10.60 μg/mL), and the transformation frequency was significantly increased in a dose-dependent manner. These results indicate that short-term exposure (72 hours) to AgNPs had in vitro carcinogenetic potency in Balb/c 3T3 A31-1-1 cells.

Cobalt nanoparticles induce lung injury, DNA damage and mutations in mice

BACKGROUND

We and other groups have demonstrated that exposure to cobalt nanoparticles (Nano-Co) caused oxidative stress and inflammation, which have been shown to be strongly associated with genotoxic and carcinogenic effects. However, few studies have reported Nano-Co-induced genotoxic effects in vivo. Here, we propose that Nano-Co may have high genotoxic effects due to their small size and high surface area, which have high capacity for causing oxidative stress and inflammation.

METHODS

gpt delta transgenic mice were used as our in vivo study model. They were intratracheally instilled with 50 μg per mouse of Nano-Co. At day 1, 3, 7 and 28 after exposure, bronchoalveolar lavage (BAL) was performed and the number of neutrophils, CXCL1/KC level, LDH activity and concentration of total protein in the BAL fluid (BALF) were determined. Mouse lung tissues were collected for H&E staining, and Ki-67, PCNA and γ-H2AX immunohistochemical staining. 8-OHdG level in the genomic DNA of mouse lungs was determined by an OxiSelect™ Oxidative DNA Damage ELISA Kit, and mutant frequency and mutation spectrum in the gpt gene were also determined in mouse lungs at four months after Nano-Co exposure by 6-TG selection, colony PCR, and DNA sequencing.

RESULTS

Exposure of mice to Nano-Co (50 μg per mouse) resulted in extensive acute lung inflammation and lung injury which were reflected by increased number of neutrophils, CXCL1/KC level, LDH activity and concentration of total protein in the BALF, and infiltration of large amount of neutrophils and macrophages in the alveolar space and interstitial tissues. Increased immunostaining of cell proliferation markers, Ki-67 and PCNA, and the DNA damage marker, γ-H2AX, was also observed in bronchiolar epithelial cells and hyperplastic type II pneumocytes in mouse lungs at day 7 after Nano-Co exposure. At four months after exposure, extensive interstitial fibrosis and proliferation of interstitial cells with inflammatory cells infiltrating the alveolar septa were observed. Moreover, Nano-Co caused increased level of 8-OHdG in genomic DNA of mouse lung tissues. Nano-Co also induced a much higher mutant frequency as compared to controls, and the most common mutation was G:C to T:A transversion, which may be explained by Nano-Co-induced increased formation of 8-OHdG.

CONCLUSION

Our study demonstrated that exposure to Nano-Co caused oxidative stress, lung inflammation and injury, and cell proliferation, which further resulted in DNA damage and DNA mutation. These findings have important implications for understanding the potential health effects of nanoparticle exposure.

Immunotoxicity, genotoxicity and epigenetic toxicity of nanomaterials: New strategies for toxicity testing?

The unique properties of nanomaterials (NMs) are beneficial in numerous industrial and medical applications. However, they could also induce unintended effects. Thus, a proper strategy for toxicity testing is essential in human hazard and risk assessment. Toxicity can be tested in vivo and in vitro; in compliance with the 3Rs, alternative strategies for in vitro testing should be further developed for NMs. Robust, standardized methods are of great importance in nanotoxicology, with comprehensive material characterization and uptake as an integral part of the testing strategy. Oxidative stress has been shown to be an underlying mechanism of possible toxicity of NMs, causing both immunotoxicity and genotoxicity. For testing NMs in vitro, a battery of tests should be performed on cells of human origin, either cell lines or primary cells, in conditions as close as possible to an in vivo situation. Novel toxicity pathways, particularly epigenetic modification, should be assessed along with conventional toxicity testing methods. However, to initiate epigenetic toxicity screens for NM exposure, there is a need to better understand their adverse effects on the epigenome, to identify robust and reproducible causal links between exposure, epigenetic changes and adverse phenotypic endpoints, and to develop improved assays to monitor epigenetic toxicity.

Genotoxicity of two heavy metal compounds: lead nitrate and cobalt chloride in Polychaete Perinereis cultrifera

The present study explores the in vivo and in vitro genotoxic effects of lead nitrate, [Pb(NO₃)₂] a recognized environmental pollutant and cobalt chloride (CoCl₂), an emerging environmental pollutant in polychaete Perinereis cultrifera using comet assay. Despite widespread occurrence and extensive industrial applications, no previous published reports on genotoxicity of these compounds are available in polychaete as detected by comet assay. Polychaetes were exposed in vivo to Pb(NO₃)₂ (0, 100, 500, and 1000 μg/l) and CoCl₂ (0, 100, 300, and 500 μg/l) for 5 days. At 100 μg/l Pb(NO₃)₂ concentration, tail DNA (TDNA) values in coelomocytes were increase by 1.16, 1.43, and 1.55-fold after day 1, day 3, and day 5, whereas, OTM showed 1.12, 2.33, and 2.10-fold increase in in vivo. Pb(NO₃)₂ showed a concentration and time-dependent genotoxicity whereas CoCl₂ showed a concentration-dependent genotoxicity in in vivo. A concentration-dependent increase in DNA damage was observed in in vitro studies for Pb(NO₃)₂ and CoCl₂. DNA damage at 500 μg/L showed almost threefold increase in TDNA and approximately fourfold increase in OTM as compared to control in in vitro. Our studies suggest that Pb(NO₃)₂ and CoCl₂ have potential to cause genotoxic damage, with Pb(NO₃)₂ being more genotoxic in polychaete and should be used more carefully in industrial and other activities. Graphical abstract.

In vitro evaluation of cobalt oxide nanoparticle-induced toxicity

Cobalt oxide (Co₃O₄) nanoparticles have applications in nanomedicine and nanotechnology; therefore, any possible adverse effects require thorough investigation. The present study investigated the effects of Co₃O₄ nanoparticles on four different cell lines: liver, HepG2 hepatocellular carcinoma cells; lung, A549 lung carcinoma cells; gastrointestinal, Caco-2 colorectal adenocarcinoma cells; and nervous system, SH-SY5Y neuroblastoma cells. A difference was observed in cell sensitivity toward Co₃O₄ nanoparticles. Co₃O₄ nanoparticles were taken up by all the cell types. However, no cell death was observed in HepG2, Caco-2, or SH-SY5Y cells; only A549 cells showed cytotoxicity at relatively high exposure concentrations. Co₃O₄ nanoparticles did not induce DNA damage or apoptosis in the cell lines tested except in A549. Interestingly, Co₃O₄ nanoparticles induced cellular oxidative damage in all cell types except Caco-2, resulting in increased malondialdehyde and 8-hydroxydeoxyguanosine levels and decreased glutathione levels. According to our results, it could be indicated that high concentrations of Co₃O₄ nanoparticles affected the pulmonary system but were unlikely to affect the liver, nervous system, or gastrointestinal system. Co₃O₄ nanoparticles might be safely used for industrial, commercial, and nanomedical applications if dose rates are adjusted depending on the route of exposure. However, further in vivo and in vitro studies are required to confirm the safety of Co₃O₄ nanoparticles.

L-Ascorbic Acid Protected Against Extrinsic and Intrinsic Apoptosis Induced by Cobalt Nanoparticles Through ROS Attenuation

Currently, tissue damage induced by cobalt nanoparticles (CoNPs) and cobalt ions (Co²⁺) are the most serious syndrome in the patients with metal-on-metal hip prostheses. Therefore, an urgent need exists for the identification of the mechanisms and the development of therapeutic strategies to limit it. The purpose of this study was to explore the mechanism of this damage and to demonstrate if L-ascorbic acid (L-AA) could protect against the cell toxicities induced by CoNPs and Co²⁺ in vitro. With CoNPs and Co²⁺ treatment, cell viability was significantly decreased; the ROS (reactive oxygen species) level in mitochondria was dramatically increased in CoNPs treated cells, but cobalt ions could barely induce the ROS. Consistently, the level of cell apoptosis was increased with the upregulation of pro-apoptotic factors (caspases 8, 9, and 3, and Bax) and the downregulation of anti-apoptotic factor Bcl-2. Besides that, the levels of cytochrome c and AIF were increased and released from mitochondria into the cytoplasm. After the cells were pretreated with L-AA, the cell viability decreased by CoNPs was reversed and the ROS induced by CoNPs was suppressed. The level of cell apoptosis induced by CoNPs was decreased as well. But it could not reverse the effects induced by Co²⁺. These studies demonstrated that CoNPs induce extrinsic and intrinsic apoptotic pathways via generation of ROS, and L-AA could prevent the cytotoxicity by reducing the level of ROS. While Co²⁺ may induce cytotoxicity through other signals, it could not be protected by L-AA treatment.

Crystallinity depends on choice of iron salt precursor in the continuous hydrothermal synthesis of Fe–Co oxide nanoparticles

A series of Fe–Co oxide nanoparticles (NPs) were prepared by a continuous hydrothermal method using iron nitrate and ammonium iron citrate as alternative iron precursors.

Nanotoxicity of cobalt induced by oxidant generation and glutathione depletion in MCF-7 cells

There are very few studies regarding the biological activity of cobalt-based nanoparticles (NPs) and, therefore, the possible mechanism behind the biological response of cobalt NPs has not been fully explored. The present study was designed to explore the potential mechanisms of the cytotoxicity of cobalt NPs in human breast cancer (MCF-7) cells. The shape and size of cobalt NPs were characterized by scanning and transmission electron microscopy (SEM and TEM). The crystallinity of NPs was determined by X-ray diffraction (XRD). The dissolution of NPs was measured in phosphate-buffered saline (PBS) and culture media by atomic absorption spectroscopy (AAS). Cytotoxicity parameters, such as [3-(4,5-dimethyl thiazol-2-yl)-2,5-diphenyl tetrazolium bromide] (MTT), neutral red uptake (NRU), and lactate dehydrogenase (LDH) release suggested that cobalt NPs were toxic to MCF-7 cells in a dose-dependent manner (50-200μg/ml). Cobalt NPs also significantly induced reactive oxygen species (ROS) generation, lipid peroxidation (LPO), mitochondrial outer membrane potential loss (MOMP), and activity of caspase-3 enzymes in MCF-7 cells. Moreover, cobalt NPs decreased intracellular antioxidant glutathione (GSH) molecules. The exogenous supply of antioxidant N-acetyl cysteine in cobalt NP-treated cells restored the cellular GSH level and prevented cytotoxicity that was also confirmed by microscopy. Similarly, the addition of buthionine-[S, R]-sulfoximine, which interferes with GSH biosynthesis, potentiated cobalt NP-mediated toxicity. Our data suggested that low solubility cobalt NPs could exert toxicity in MCF-7 cells mainly through cobalt NP dissolution to Co²⁺.

Assessment of thyroid endocrine system impairment and oxidative stress mediated by cobalt ferrite (CoFe2 O4 ) nanoparticles in zebrafish larvae

Fascinating super paramagnetic uniqueness of iron oxide particles at nano-scale level make them extremely useful in the state of the art therapies, equipments, and techniques. Cobalt ferrite (CoFe₂ O₄ ) magnetic nanoparticles (MNPs) are extensively used in nano-based medicine and electronics, results in extensive discharge and accumulation into the environment. However, very limited information is available for their endocrine disrupting potential in aquatic organisms. In this study, the thyroid endocrine disrupting ability of CoFe₂ O₄ NPs in Zebrafish larvae for 168-h post fertilization (hpf) was evaluated. The results showed the elevated amounts of T4 and T3 hormones by malformation of hypothalamus pituitary axis in zebrafish larvae. These elevated levels of whole body THs leads to delayed hatching, head and eye malformation, arrested development, and alterations in metabolism. The influence of THs disruption on ROS production and change in activities of catalase (CAT), mu-glutathione s-transferase (mu-GST), and acid phosphatase (AP) were also studied. The production of significantly higher amounts of in vivo generation of ROS leads to membrane damage and oxidative stress. Presences of NPs and NPs agglomerates/aggregates were also the contributing factors in mechanical damaging the membranes and physiological structure of thyroid axis. The increased activities of CAT, mu-GST, and AP confirmed the increased oxidative stress, possible DNA, and metabolic alterations, respectively. The excessive production of in vivo ROS leads to severe apoptosis in head, eye, and heart region confirming that malformation leads to malfunctioning of hypothalamus pituitary axis. ROS-induced oxidative DNA damage by formation of 8-OHdG DNA adducts elaborates the genotoxicity potential of CoFe₂ O₄ NPs. This study will help us to better understand the risk and assessment of endocrine disrupting potential of nanoparticles. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 2068-2080, 2016.

In vitro toxicity assessment of oral nanocarriers

The fascinating properties of nanomaterials opened new frontiers in medicine. Nanocarriers are useful systems in transporting drugs to site-specific targets. The unique physico-chemical characteristics making nanocarriers promising devices to treat diseases may also be responsible for potential adverse effects. In order to develop functional nano-based drug delivery systems, efficacy and safety should be carefully evaluated. To date, no common testing strategy to address nanomaterial toxicological challenges has been generated. Different cell culture models are currently used to evaluate nanocarrier safety using conventional in vitro assays, but overall they have generated a huge amount of conflicting data. In this review we describe state-of-the-art approaches for in vitro testing of orally administered nanocarriers, highlighting the importance of developing harmonized and validated standard operating procedures. These procedures should be applied in a safe-by-design context with the aim to reduce and/or eliminate the uncertainties and risks associated with nanomedicine development.

Cytotoxicity and genotoxicity in liver cells induced by cobalt nanoparticles and ions

Objectives

The cytotoxicity induced by cobalt ions (Co²⁺) and cobalt nanoparticles (Co-NPs) which released following the insertion of a total hip prosthesis, has been reported. However, little is known about the underlying mechanisms. In this study, we investigate the toxic effect of Co²⁺ and Co-NPs on liver cells, and explain further the potential mechanisms.

Methods

Co-NPs were characterised for size, shape, elemental analysis, and hydrodynamic diameter, and were assessed by Transmission Electron Microscope, Scanning Electron Microscope, Energy Dispersive X-ray Spectroscopy and Dynamic Light Scattering. BRL-3A cells were used in this study. Cytotoxicity was evaluated by MTT and lactate dehydrogenase release assay. In order to clarify the potential mechanisms, reactive oxygen species, Bax/Bcl-2 mRNA expression, IL-8 mRNA expression and DNA damage were assessed on BRL-3A cells after Co²⁺ or Co-NPs treatment.

Results

Results showed cytotoxic effects of Co²⁺ and Co-NPs were dependent upon time and dosage, and the cytotoxicity of Co-NPs was greater than that of Co²⁺. In addition, Co-NPs elicited a significant (p < 0.05) reduction in cell viability with a concomitant increase in lactic dehydrogenase release, reactive oxygen species generation, IL-8 mRNA expression, Bax/Bcl-2 mRNA expression and DNA damage after 24 hours of exposure.

Conclusion

Co-NPs induced greater cytotoxicity and genotoxicity in BRL-3A cells than Co²⁺. Cell membrane damage, oxidative stress, immune inflammation and DNA damage may play an important role in the effects of Co-NPs on liver cells.

Cite this article: Y. K. Liu, X. X. Deng, H.L. Yang. Cytotoxicity and genotoxicity in liver cells induced by cobalt nanoparticles and ions. Bone Joint Res 2016;5:461–469. DOI: 10.1302/2046-3758.510.BJR-2016-0016.R1.

Carcinogenic potential of metal nanoparticles in BALB/3T3 cell transformation assay

Metal-based nanoparticles (NPs), are currently used in many application fields including consumer products, pharmaceuticals, and biomedical treatments. In spite to their wide applications, an in-depth study of their potential toxic effects is still lacking. The aim of the present research was to investigate the potential initiator or promoter-like activity of different metallic NPs such as gold, iron, cobalt, and cerium using the Balb/3T3 two-stage transformation assay. The results indicated that all the selected metallic NPs, except for cobalt, when used as initiators did not induce any transformation in Balb/3T3 cell line. Moreover, Au and Fe3 O4 NPs, when used in place of the tumor promoter treatment TPA, increased significantly the number of Foci/dish as compared to the MCA treatment alone. The number of Foci/dish was 2.6 for Au NPs and 2.13 for Fe3 O4 ones, similar to those obtained by the positive control treatment (MCA + TPA), whereas 1.27 for MCA treatment alone. On the contrary, CeO2 NPs did not show any difference in the number of Foci/dish, as compared to MCA alone, but it decreased the number of foci by 65% in comparison to the positive control (MCA + TPA). As expected, cobalt NPs showed an increased cytotoxicity and only a few surviving cells were found at the time of analysis showing a number of Foci/dish of 0.13. For the first time, our data clearly showed that Au and Fe3 O4 NPs act as promoters in the two stage transformational assay, suggesting the importance to fully investigate the NPs carcinogenic potential with different models.

Poorly soluble cobalt oxide particles trigger genotoxicity via multiple pathways

BACKGROUND

Poorly soluble cobalt (II, III) oxide particles (Co3O4P) are believed to induce in vitro cytotoxic effects via a Trojan-horse mechanism. Once internalized into lysosomal and acidic intracellular compartments, Co3O4P slowly release a low amount of cobalt ions (Co(2+)) that impair the viability of in vitro cultures. In this study, we focused on the genotoxic potential of Co3O4P by performing a comprehensive investigation of the DNA damage exerted in BEAS-2B human bronchial epithelial cells.

RESULTS

Our results demonstrate that poorly soluble Co3O4P enhanced the formation of micronuclei in binucleated cells. Moreover, by comet assay we showed that Co3O4P induced primary and oxidative DNA damage, and by scoring the formation of γ-H2Ax foci, we demonstrated that Co3O4P also generated double DNA strand breaks.

CONCLUSIONS

By comparing the effects exerted by poorly soluble Co3O4P with those obtained in the presence of soluble cobalt chloride (CoCl2), we demonstrated that the genotoxic effects of Co3O4P are not simply due to the released Co(2+) but are induced by the particles themselves, as genotoxicity is observed at very low Co3O4P concentrations.

Genotoxicity assessment of cobalt chloride in Eisenia hortensis earthworms coelomocytes by comet assay and micronucleus test

Cobalt and its different compounds are extensively used worldwide and considered as possible environmental pollutant. Earthworms are useful model organism and its different species are used to monitor soil pollution. No study has been found to detect cobalt chloride (CoCl2) genotoxicity in earthworms. So, current study aimed to evaluate CoCl2 induced genotoxicity in Eisenia hortensis earthworms coelomocytes by alkaline comet assay (CA) and micronucleus (MN) test. The earthworms (n = 10 for each group) were exposed to different series of CoCl2 concentrations (100 ppm, 200 ppm, 300 ppm, 400 ppm, 500 ppm, 600 ppm) to find LD50. The LD50 for CoCl2 was found at 226 ppm. Then, doses of LD50/2, LD50 and 2XLD50 for 48 h were used. CA and MN demonstrated the significant increase (P < 0.05) in DNA damage and chromosomal aberrations. Dose dependent relationship was found. Highest DNA damage and chromosomal aberrations were noticed at 2XLD50. The results concluded that CoCl2 induced DNA damage, cytokinesis failure and chromosomal aberrations in E. hortensis earthworms.

The Protective Effect of Bafilomycin A1 Against Cobalt Nanoparticle-Induced Cytotoxicity and Aseptic Inflammation in Macrophages In Vitro

Co ions released due to corrosion of Co nanoparticles (CoNPs) in the lysosomes of macrophages may be a factor in the particle-induced cytotoxicity and aseptic inflammation accompanying metal-on-metal (MOM) hip prosthesis failure. Here, we show that CoNPs are easily dissolved under a low pH, simulating the acidic lysosomal environment. We then used bafilomycin A1 to change the pH inside the lysosome to inhibit intracellular corrosion of CoNPs and then investigated its protective effects against CoNP-induced cytotoxicity and aseptic inflammation on murine macrophage RAW264.7 cells. XTT {2,3-bis (2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino) carbonyl]-2H-tetrazolium hydroxide} assays revealed that bafilomycin A1 can significantly decrease CoNP-induced cytotoxicity in RAW264.7 cells. Enzyme-linked immunosorbent assays showed that bafilomycin A1 can significantly decrease the subtoxic concentration of CoNP-induced levels of pro-inflammatory cytokines (tumor necrosis factor-α, interleukin-1β, and interleukin-6), but has no effect on anti-inflammatory cytokines (transforming growth factor-β and interleukin-10) in RAW264.7 cells. We studied the protective mechanism of bafilomycin A1 against CoNP-induced effects in RAW264.7 cells by measuring glutathione/oxidized glutathione (GSH/GSSG), superoxide dismutase, catalase, and glutathione peroxidase levels and employed scanning electron microscopy, transmission electron microscopy, and energy dispersive spectrometer assays to observe the ultrastructural cellular changes. The changes associated with apoptosis were assessed by examining the pAKT and cleaved caspase-3 levels using Western blotting. These data strongly suggested that bafilomycin A1 can potentially suppress CoNP-induced cytotoxicity and aseptic inflammation by inhibiting intracellular corrosion of CoNPs and that the reduction in Co ions released from CoNPs may play an important role in downregulating oxidative stress in RAW264.7 cells.