Genotoxicity and gene expression modulation of silver and titanium dioxide nanoparticles in mice

In Vitro Evaluation of DNA Damage Induction by Silver (Ag), Gold (Au), Silica (SiO2), and Aluminum Oxide (Al2O3) Nanoparticles in Human Peripheral Blood Mononuclear Cells

Nanoparticles (NPs) are increasingly applied in a wide range of technological and medical applications. While their use offers numerous benefits, it also raises concerns regarding their safety. Therefore, understanding their cytotoxic effects and DNA-damaging properties is crucial for ensuring the safe application of NPs. In this study, DNA-damaging properties of PVP-coated silver, silica, aluminum oxide (13 nm and 50 nm), and gold (5 nm and 40 nm) NPs in human peripheral blood mononuclear cells (PBMCs) were investigated. NPs' internalization and induction of reactive oxygen species were evaluated using flow cytometry. Cytotoxic properties were determined using a dual acridine orange/ethidium bromide staining technique while DNA-damaging properties were assessed using an alkaline comet assay. We observed that Ag, SiO2, and both sizes of Al2O3 NPs were efficiently internalized by human PBMCs, but only PVP-AgNPs (at 10-30 µg/mL) and SiO2 NPs (at concentrations > 100 µg/mL) induced significant DNA damage after a 24 h exposure. In contrast, the uptake of both sizes of gold nanoparticles was limited, though they were able to cause significant DNA damage after a 3 h exposure. These findings highlight the different responses of human PBMCs to various NPs, emphasizing the importance of their size, composition, and internalization rates in nanotoxicology testing.

Overview of in vitro-in vivo extrapolation approaches for the risk assessment of nanomaterial toxicity

Nanomaterials are increasingly used in many applications due to their enhanced properties. To ensure their safety for humans and the environment, nanomaterials need to be evaluated for their potential risk. The risk assessment analysis on the nanomaterials based on animal or in vivo studies is accompanied by several concerns, including animal welfare, time and cost needed for the studies. Therefore, incorporating in vitro studies in the risk assessment process is increasingly considered. To be able to analyze the potential risk of nanomaterial to human health, there are factors to take into account. Utilizing in vitro data in the risk assessment analysis requires methods that can be used to translate in vitro data to predict in vivo phenomena (in vitro-in vivo extrapolation (IVIVE) methods) to be incorporated, to obtain a more accurate result. Apart from the experiments and species conversion (for example, translation between the cell culture, animal and human), the challenge also includes the unique properties of nanomaterials that might cause them to behave differently compared to the same materials in a bulk form. This overview presents the IVIVE techniques that are developed to extrapolate pharmacokinetics data or doses. A brief example of the IVIVE methods for chemicals is provided, followed by a more detailed summary of available IVIVE methods applied to nanomaterials. The IVIVE techniques discussed include the comparison between in vitro and in vivo studies, methods to rene the dose metric or the in vitro models, allometric approach, mechanistic modeling, Multiple-Path Particle Dosimetry (MPPD), methods using organ burden data and also approaches that are currently being developed.

Titanium Dioxide Nanoparticles Induce Maternal Preeclampsia-like Syndrome and Adverse Birth Outcomes via Disrupting Placental Function in SD Rats

The escalating utilization of titanium dioxide nanoparticles (TiO2 NPs) in everyday products has sparked concerns regarding their potential hazards to pregnant females and their offspring. To address these concerns and shed light on their undetermined adverse effects and mechanisms, we established a pregnant rat model to investigate the impacts of TiO2 NPs on both maternal and offspring health and to explore the underlying mechanisms of those impacts. Pregnant rats were orally administered TiO2 NPs at a dose of 5 mg/kg body weight per day from GD5 to GD18 during pregnancy. Maternal body weight, organ weight, and birth outcomes were monitored and recorded. Maternal pathological changes were examined by HE staining and TEM observation. Maternal blood pressure was assessed using a non-invasive blood analyzer, and the urinary protein level was determined using spot urine samples. Our findings revealed that TiO2 NPs triggered various pathological alterations in maternal liver, kidney, and spleen, and induced maternal preeclampsia-like syndrome, as well as leading to growth restriction in the offspring. Further examination unveiled that TiO2 NPs hindered trophoblastic cell invasion into the endometrium via the promotion of autophagy. Consistent hypertension and proteinuria resulted from the destroyed the kidney GBM. In total, an exposure to TiO2 NPs during pregnancy might increase the risk of human preeclampsia through increased maternal arterial pressure and urinary albumin levels, as well as causing fetal growth restriction in the offspring.

Evaluation of possible cytotoxic, genotoxic and epigenotoxic effects of titanium dioxide nanoparticles and possible protective effect of melatonin

Nanoparticles (NPs) are particles of matter that are between 1 to 100 nm in diameter. They are suggested to cause toxic effects in both humans and environment thorough different mechanisms. However, their toxicity profile may be different from the parent material. Titanium dioxide (TiO2) NPs are widely used in cosmetic, pharmaceutical and food industries. As a white pigment, the use of TiO2 is used in food coloring, industrial paints, clothing and UV filters has increased tremendously in recent years. Melatonin, on the other hand, is a well-known antioxidant and may prevent oxidative stress caused by a variety of different substances, including NPs. In the current study, we aimed to comparatively investigate the effects of normal-sized TiO2 (220 nm) and nano-sized TiO2 (21 nm) on cytopathology, cytotoxicity, oxidative damage (lipid peroxidation, protein oxidation and glutathione), genotoxicity (8-hydroxydeoxyguanosine), apoptosis (caspase 3, 8 and 9) and epigenetic alterations (global DNA methylation, H3 acetylation) on 3T3 fibroblast cells. In addition, the possible protective effects of melatonin, which is known to have strong antioxidant effects, against the toxicity of TiO2 were also evaluated. Study groups were: a. the control group; b. melatonin group; c. TiO2 group; d. nano-sized TiO2 group; e. TiO2 + melatonin group and f. nano-sized TiO2 + melatonin group. We observed that both normal-sized and nano-sized TiO2 NPs showed significant toxic effects. However, TiO2 NPs caused higher DNA damage and global DNA methylation compared to normal-sized TiO2 whereas normal-sized TiO2 led to lower H3 acetylation vs. TiO2 NPs. Melatonin showed partial protective effect against the toxicity caused by TiO2 NPs.

Exposure to Cadmium Telluride Quantum Dots and Gene Expression Profile of Huh-7 Hepatocellular Carcinoma Cell Line

Nanoparticles have shown promising potential for efficient drug delivery, circumventing biological interferences like immunological and renal clearance and mechanical and enzymatic destruction. However, a handful of research papers have questioned the biomedical use of metal-based nanoparticles like cadmium telluride quantum dots (CdTe-QDs) for their cytotoxic, genotoxic, and carcinogenic potential. Herein, we examined the effects of CdTe-QD NPs on gene expression profile of hepatocellular carcinoma (Huh-7) cell line. Huh-7 cells were treated with CdTe-QD NPs (10 μg/ml for 6, 12, and 24 hours, and 25 μg/ml for 6 and 12 hours), and transcriptomic analysis was performed using microarray to evaluate the global gene expression profile. Differential expressed genes (DEGs) were observed for both the doses (10 and 25 μg/ml) of CdTe-QD NPs at different time points. Gene ontology (GO) analysis revealed that genes involved in molecular function of cell cycle, organizational injury and abnormalities, cell death and survival, gene expression, cancer, organismal survival, and cellular development were differentially expressed. Overall, we have demonstrated differential expression of several genes, involved in maintaining cell survival, metabolism, and genome integrity. These findings were confirmed by RT-qPCR study for some canonical pathway genes signifying possible implication in NP toxicity-mediated cell survival and inhibition of cell death.

Xenopus laevis (Daudin, 1802) as a Model Organism for Bioscience: A Historic Review and Perspective

In vitro systems have been mainly promoted by authorities to sustain research by following the 3Rs principle, but continuously increasing amounts of evidence point out that in vivo experimentation is also of extreme relevance. Xenopus laevis, an anuran amphibian, is a significant model organism in the study of evolutionary developmental biology, toxicology, ethology, neurobiology, endocrinology, immunology and tumor biology; thanks to the recent development of genome editing, it has also acquired a relevant position in the field of genetics. For these reasons, X. laevis appears to be a powerful and alternative model to the zebrafish for environmental and biomedical studies. Its life cycle, as well as the possibility to obtain gametes from adults during the whole year and embryos by in vitro fertilization, allows experimental studies of several biological endpoints, such as gametogenesis, embryogenesis, larval growth, metamorphosis and, of course, the young and adult stages. Moreover, with respect to alternative invertebrate and even vertebrate animal models, the X. laevis genome displays a higher degree of similarity with that of mammals. Here, we have reviewed the main available literature on the use of X. laevis in the biosciences and, inspired by Feymann's revised view, "Plenty of room for biology at the bottom", suggest that X. laevis is a very useful model for all possible studies.

Toxic effects of titanium dioxide nanoparticles on reproduction in mammals

Titanium dioxide nanoparticles (nano-TiO₂) are widely used in food, textiles, coatings and personal care products; however, they cause environmental and health concerns. Nano-TiO₂ can accumulate in the reproductive organs of mammals in different ways, affect the development of the ovum and sperm, damage reproductive organs and harm the growth and development of offspring. The oxidative stress response in germ cells, irregular cell apoptosis, inflammation, genotoxicity and hormone synthesis disorder are the main mechanisms of nano-TiO₂ toxicity. Possible measures to reduce the harmful effects of nano-TiO₂ on humans and nontarget organisms have emerged as an underexplored topic requiring further investigation.

Silver nanoparticles induced testicular damage targeting NQO1 and APE1 dysregulation, apoptosis via Bax/Bcl-2 pathway, fibrosis via TGF-β/α-SMA upregulation in rats

In medicine, silver nanoparticles (AgNPs) are employed often. They do, however, have negative impacts, particularly on the reproductive organs. This research aimed to assess AgNP impact on the testis and the possible intracellular mechanisms to induce testicular deteriorations in rats at various concentrations and different time intervals. Sprague Dawley rats (n = 40) were allocated into four equal groups: the control one, and three other groups injected intra-peritoneally with AgNP solution 0.25, 0.5, and 1 mg/kg b.w. respectively for 15 and 30 days. Our findings revealed that AgNPs reduced body and testicular weights, estradiol (E2) and testosterone (T) hormone levels, and sperm parameters while elevating the nitric oxide and malondialdehyde levels with inhibition of reduced glutathione contents in testicular tissue. Interestingly, AgNPs significantly upregulated the testicular inducible nitric oxide synthase, B cell lymphoma 2 (Bcl-2)-associated X, transforming growth factor, and alpha-smooth muscle actin (α-SMA) expression levels. However, apurinic/apyrimidinic endo deoxyribonuclease 1 (APE1), NAD (P) H quinone dehydrogenase 1 (NQO1), and Bcl-2 expression levels were all downregulated indicating exhaustion of body antioxidant and repairing defense mechanisms in testicles in comparison with the control rats. Various histological alterations were also detected which dramatically increased in rats sacrificed after 30 days such as loss of the lining cells of seminiferous tubules with no spermatozoa and tubular irregularities associated with thickening of their basement membranes. Immunolabeling implicated in the apoptotic pathway revealed a negative expression of Bcl-2 and marked immunoreactivity for caspase-3 after 30 days of AgNP treatment in comparison to the control rats. To our knowledge, there have been no previous publications on the role of the α-SMA, APE1, and NQO1 genes in the molecular pathogenesis of AgNP testicular cytotoxicity following AgNP acute and chronic exposure.

Assessing testicular germ cell DNA damage in the comet assay; introduction of a proof-of-concept

The in vivo comet assay is widely used to measure genotoxicity; however, the current OECD test guideline (TG 489) does not recommend using the assay to assess testicular germ cells, due to the presence of testicular somatic cells. An adapted approach to specifically assess testicular germ cells within the comet assay is certainly warranted, considering regulatory needs for germ cell-specific genotoxicity data in relation to the increasing global production of and exposure to potentially hazardous chemicals. Here, we provide a proof-of-concept to selectively analyze round spermatids and primary spermatocytes, distinguishing them from other cells of the testicle. Utilizing the comet assay recordings of DNA content (total fluorescence intensity) and DNA damage (% tail intensity) of individual comets, we developed a framework to distinguish testicular cell populations based on differences in DNA content/ploidy and appearance. Haploid round spermatid comets are identified through (1) visual inspection of DNA content distributions, (2) setting DNA content thresholds, and (3) modeling DNA content distributions using a normal mixture distribution function. We also describe an approach to distinguish primary spermatocytes during comet scoring, based on their high DNA content and large physical size. Our concept allows both somatic and germ cells to be analyzed in the same animal, adding a versatile, sensitive, rapid, and resource-efficient assay to the limited genotoxicity assessment toolbox for germ cells. An adaptation of TG 489 facilitates accumulation of valuable information regarding distribution of substances to germ cells and their potential for inducing germ cell gene mutations and structural chromosomal aberrations.

Putative adverse outcome pathways for silver nanoparticle toxicity on mammalian male reproductive system: a literature review

BACKGROUND

Adverse outcome pathways (AOPs) are conceptual frameworks that organize knowledge about biological interactions and toxicity mechanisms. They present a sequence of events commencing with initial interaction(s) of a stressor, which defines the perturbation in a biological system (molecular initiating event, MIE), and a dependent series of key events (KEs), ending with an adverse outcome (AO). AOPs have recently become the subject of intense studies in a view to better understand the mechanisms of nanomaterial (NM) toxicity. Silver nanoparticles (Ag NPs) are one of the most explored nanostructures and are extensively used in various application. This, in turn, has increased the potential for interactions of Ag NPs with environments, and toxicity to human health. The aim of this study was to construct a putative AOPs (pAOP) related to reproductive toxicity of Ag NPs, in order to lay the groundwork for a better comprehension of mechanisms affecting both undesired toxicity (against human cell) and expected toxicity (against microorganisms).

METHODS

PubMed and Scopus were systematically searched for peer-reviewed studies examining reproductive toxicity potential of Ag NPs. The quality of selected studies was assessed through ToxRTool. Eventually, forty-eight studies published between 2005 and 2022 were selected to identify the mechanisms of Ag NPs impact on reproductive function in human male. The biological endpoints, measurements, and results were extracted from these studies. Where possible, endpoints were assigned to a potential KE and an AO using expert judgment. Then, KEs were classified at each major level of biological organization.

RESULTS

We identified the impairment of intracellular SH-containing biomolecules, which are major cellular antioxidants, as a putative MIE, with subsequent KEs defined as ROS accumulation, mitochondrial damage, DNA damage and lipid peroxidation, apoptosis, reduced production of reproductive hormones and reduced quality of sperm. These successive KEs may result in impaired male fertility (AO).

CONCLUSION

This research recapitulates and schematically represents complex literature data gathered from different biological levels and propose a pAOP related to the reproductive toxicity induced by AgNPs. The development of AOPs specific to NMs should be encouraged in order to provide new insights to gain a better understanding of NP toxicity.

Reduced genotoxicity of lignin-derivable replacements to bisphenol A studied using in silico, in vitro, and in vivo methods

Bisguaiacols, lignin-derivable bisphenols, are considered promising and possibly safer alternatives to bisphenol A (BPA), but comprehensive toxicity investigations are needed to ensure safety. Most toxicity studies of BPA and its analogues have focused on potential estrogenic activity, and only limited toxicological data are available on other toxicity aspects, such as genotoxicity at low exposure levels. In this study, the genotoxicity of six lignin-derivable bisguaiacols with varying regioisomer contents and degrees of methoxy substitution was investigated using a multi-tiered method, consisting of in silico simulations, in vitro Ames tests, and in vivo comet tests. The toxicity estimation software tool, an application that predicts toxicity of chemicals using quantitative structure-activity relationships, calculated that the majority of the lignin-derivable bisguaiacols were non-mutagenic. These results were supported by Ames tests using five tester strains (TA98, TA100, TA102, TA1535, and TA1537) at concentrations ranging from 0.5 pmol/plate to 5 nmol/plate. The potential genotoxicity of bisguaiacols was further evaluated using in vivo comet testing in fetal chicken livers, and in addition to the standard alkaline comet assay, the formamidopyrimidine DNA glycosylase enzyme-modified comet assay was employed to investigate oxidative DNA damage in the liver samples. The oxidative stress analyses indicated that the majority of lignin-derivable analogues showed no signs of mutagenicity (mutagenic index < 1.5) or genotoxicity, in comparison to BPA and bisphenol F, likely due to the methoxy groups on the lignin-derivable aromatics. These findings reinforce the potential of lignin-derivable bisphenols as safer alternatives to BPA.

Inflammatory Genes Associated with Pristine Multi-Walled Carbon Nanotubes-Induced Toxicity in Ocular Cells

Background

The wide application of multi-walled carbon nanotubes (MWCNTs) in various fields has raised enormous concerns regarding their safety for humans. However, studies on the toxicity of MWCNTs to the eye are rare and potential molecular mechanisms are completely lacking. This study was to evaluate the adverse effects and toxic mechanisms of MWCNTs on human ocular cells.

Methods

Human retinal pigment epithelial cells (ARPE-19) were treated with pristine MWCNTs (7-11 nm) (0, 25, 50, 100 or 200 μg/mL) for 24 hours. MWCNTs uptake into ARPE-19 cells was examined using transmission electron microscopy (TEM). The cytotoxicity was evaluated by CCK-8 assay. The death cells were detected by Annexin V-FITC/PI assay. RNA profiles in MWCNT-exposed and non-exposed cells (n = 3) were analyzed using RNA-sequencing. The differentially expressed genes (DEGs) were identified through the DESeq2 method and hub of which were filtered by weighted gene co-expression, protein-protein interaction (PPI) and lncRNA-mRNA co-expression network analyses. The mRNA and protein expression levels of crucial genes were verified using quantitative polymerase chain reaction (qPCR), colorimetric analysis, ELISA and Western blotting. The toxicity and mechanisms of MWCNTs were also validated in human corneal epithelial cells (HCE-T).

Results

TEM analysis indicated the internalization of MWCNTs into ARPE-19 cells to cause cell damage. Compared with untreated ARPE-19 cells, those exposed to MWCNTs exhibited significantly decreased cell viabilities in a dose-dependent manner. The percentages of apoptotic (early, Annexin V positive; late, Annexin V and PI positive) and necrotic (PI positive) cells were significantly increased after exposure to IC50 concentration (100 μg/mL). A total of 703 genes were identified as DEGs; 254 and 56 of them were, respectively, included in darkorange2 and brown1 modules that were significantly associated with MWCNT exposure. Inflammation-related genes (including CXCL8, MMP1, CASP3, FOS, CXCL2 and IL11) were screened as hub genes by calculating the topological characteristics of genes in the PPI network. Two dysregulated long non-coding RNAs (LUCAT1 and SCAT8) were shown to regulate these inflammation-related genes in the co-expression network. The mRNA levels of all eight genes were confirmed to be upregulated, while caspase-3 activity and the release of CXCL8, MMP1, CXCL2, IL11 and FOS proteins were demonstrated to be increased in MWCNT-treated ARPE-19 cells. MWCNTs exposure also can induce cytotoxicity and increase the caspase-3 activity and the expression of LUCAT1, MMP1, CXCL2, and IL11 mRNA and protein in HCE-T cells.

Conclusion

Our study provides promising biomarkers for monitoring MWCNT-induced eye disorders and targets for developing preventive and therapeutic strategies.

Impact of Nanoparticles on Male Fertility: What Do We Really Know? A Systematic Review

The real impact of nanoparticles on male fertility is evaluated after a careful analysis of the available literature. The first part reviews animal models to understand the testicular biodistribution and biopersistence of nanoparticles, while the second part evaluates their in vitro and in vivo biotoxicity. Our main findings suggest that nanoparticles are generally able to reach the testicle in small quantities where they persist for several months, regardless of the route of exposure. However, there is not enough evidence that they can cross the blood-testis barrier. Of note, the majority of nanoparticles have low direct toxicity to the testis, but there are indications that some might act as endocrine disruptors. Overall, the impact on spermatogenesis in adults is generally weak and reversible, but exceptions exist and merit increased attention. Finally, we comment on several methodological or analytical biases which have led some studies to exaggerate the reprotoxicity of nanoparticles. In the future, rigorous clinical studies in tandem with mechanistic studies are needed to elucidate the real risk posed by nanoparticles on male fertility.

Cytocompatibility and osteogenic differentiation of stem cells from human exfoliated deciduous teeth with cotton cellulose nanofibers for tissue engineering and regenerative medicine

Cellulose nanofibers (CNFs) are natural polymers with physical-chemical properties that make them very attractive for modulating stem cell differentiation, a crucial step in tissue engineering and regenerative medicine. Although cellulose is cytocompatible, when materials are in nanoscale, they become more reactive, needing to evaluate its potential toxic effect to ensure safe application. This study aimed to investigate the cytocompatibility of cotton CNF and its differentiation capacity induction on stem cells from human exfoliated deciduous teeth. First, the cotton CNF was characterized. Then, the cytocompatibility and the osteogenic differentiation induced by cotton CNF were examined. The results revealed that cotton CNFs have about 6-18 nm diameters, and the zeta potential was -10 mV. Despite gene expression alteration, the cotton CNF shows good cytocompatibility. The cotton CNF induced an increase in phosphatase alkaline activity and extracellular matrix mineralization. The results indicate that cotton CNF has good cytocompatibility and can promote cell differentiation without using chemical inducers, showing great potential as a new differentiation inductor for tissue engineering and regenerative medicine applications.

Technical Evaluation of Commercial Sperm DFI Quality Control Products in SCSA Testing

With the increase in population and the advancement of medicine, people even more hope that their offspring will be healthier. DNA fragmentation rate is currently one of the more common indicators for evaluating sperm fertility and predicting the outcome of pregnancy. In order to evaluate the technical performance and application value of commercial sperm DFI (DNA fragmentation index) quality control products in the flow cytometry sperm chromatin structure analysis (SCSA), this paper uses flow cytometry to test commercial sperm DFI quality control products (Celula) and laboratory routine self-made DFI quality control products. In this paper, the quality control of new commercial sperm DFI and laboratory-made quality control were compared and tested for 30 consecutive days. And this paper monitors the response of commercial quality control products to the interference of key reagent parameters. This paper compares the stability of the test results of two quality control products and their sensitivity to the interference of key performance parameters of the detection reagent. Experimental results show that commercial sperm DFI quality control products can simulate sperm DNA damage to achieve accurate detection of DNA integrity. The stability of commercial sperm DFI quality control (CV = 2.47%) is better than that of laboratory-made quality control (CV = 11.22%). The new commercial sperm DFI quality control product can sensitively detect changes in the concentration of acidified solution and staining solution at the same time. It can effectively control the quality of detection reagents and experimental procedures. The new commercial sperm DFI quality control product can effectively control sperm DNA integrity testing. It can be used as an external quality control product for quality control of test results to ensure that more accurate test results are provided to the clinic.

Advances in genotoxicity of titanium dioxide nanoparticles in vivo and in vitro

Titanium dioxide nanoparticles (TiO₂ NPs) are currently one of the most widely used nanomaterials. Due to an increasing scope of applications, the exposure of humans to TiO₂ NP is inevitable, such as entering the body through the mouth with food additives or drugs, invading the damaged skin with cosmetics, and entering the body through the respiratory tract during the process of production and handling. Compared with TiO₂ coarse particles, TiO₂ NPs have stronger conductivity, reaction activity, photocatalysis, and permeability, which may lead to greater toxicity to organisms. Given that TiO₂ was classified as a category 2B carcinogen (possibly carcinogenic to humans), the genotoxicity of TiO₂ NPs has become the focus of attention. There have been a series of previous studies investigating the potential genotoxicity of TiO₂ NPs, but the existing research results are still controversial and difficult to conclude. More than half of studies have shown that TiO₂ NPs can cause genotoxicity, suggesting that TiO₂ NPs are likely to be genotoxic to humans. And the genotoxicity of TiO₂ NPs is closely related to the exposure concentration, mode and time, and experimental cells/animals as well as its physicochemical properties (crystal type, size, and shape). This review summarized the latest research progress of related genotoxic effects through in vivo studies and in vitro cell tests, hoping to provide ideas for the evaluation of TiO₂ NPs genotoxicity.

Validation of the in vitro comet assay for DNA cross-links and altered bases detection

Mechanistic toxicology is gaining weight for human health risk assessment. Different mechanistic assays are available, such as the comet assay, which detects DNA damage at the level of individual cells. However, the conventional alkaline version only detects strand breaks and alkali-labile sites. We have validated two modifications of the in vitro assay to generate mechanistic information: (1) use of DNA-repair enzymes (i.e., formamidopyrimidine DNA glycosylase, endonuclease III, human 8-oxoguanine DNA glycosylase I and human alkyladenine DNA glycosylase) for detection of oxidized and alkylated bases as well as (2) a modification for detecting cross-links. Seven genotoxicants with different mechanisms of action (potassium bromate, methyl methanesulfonate, ethyl methanesulfonate, hydrogen peroxide, cisplatin, mitomycin C, and benzo[a]pyrene diol epoxide), as well as a non-genotoxic compound (dimethyl sulfoxide) and a cytotoxic compound (Triton X-100) were tested on TK-6 cells. We were able to detect with high sensitivity and clearly differentiate oxidizing, alkylating and cross-linking agents. These modifications of the comet assay significantly increase its sensitivity and its specificity towards DNA lesions, providing mechanistic information regarding the type of damage.

Gene Expression and Transcriptome Profiling of Changes in a Cancer Cell Line Post-Exposure to Cadmium Telluride Quantum Dots: Possible Implications in Oncogenesis

Cadmium telluride quantum dots (CdTe-QDs) are acquiring great interest in terms of their applications in biomedical sciences. Despite earlier sporadic studies on possible oncogenic roles and anticancer properties of CdTe-QDs, there is limited information regarding the oncogenic potential of CdTe-QDs in cancer progression. Here, we investigated the oncogenic effects of CdTe-QDs on the gene expression profiles of Chang cancer cells. Chang cancer cells were treated with 2 different doses of CdTe-QDs (10 and 25 μg/ml) at different time intervals (6, 12, and 24 h). Functional annotations helped identify the gene expression profile in terms of its biological process, canonical pathways, and gene interaction networks activated. It was found that the gene expression profiles varied in a time and dose-dependent manner. Validation of transcriptional changes of several genes through quantitative PCR showed that several genes upregulated by CdTe-QD exposure were somewhat linked with oncogenesis. CdTe-QD-triggered functional pathways that appear to associate with gene expression, cell proliferation, migration, adhesion, cell-cycle progression, signal transduction, and metabolism. Overall, CdTe-QD exposure led to changes in the gene expression profiles of the Chang cancer cells, highlighting that this nanoparticle can further drive oncogenesis and cancer progression, a finding that indicates the merit of immediate in vivo investigation.

Genotoxicity and Gene Expression in the Rat Lung Tissue following Instillation and Inhalation of Different Variants of Amorphous Silica Nanomaterials (aSiO2 NM)

Several reports on amorphous silica nanomaterial (aSiO2 NM) toxicity have been questioning their safety. Herein, we investigated the in vivo pulmonary toxicity of four variants of aSiO2 NM: SiO2_15_Unmod, SiO2_15_Amino, SiO2_7 and SiO2_40. We focused on alterations in lung DNA and protein integrity, and gene expression following single intratracheal instillation in rats. Additionally, a short-term inhalation study (STIS) was carried out for SiO2_7, using TiO2_NM105 as a benchmark NM. In the instillation study, a significant but slight increase in oxidative DNA damage in rats exposed to the highest instilled dose (0.36 mg/rat) of SiO2_15_Amino was observed in the recovery (R) group. Exposure to SiO2_7 or SiO2_40 markedly increased oxidative DNA lesions in rat lung cells of the exposure (E) group at every tested dose. This damage seems to be repaired, since no changes compared to controls were observed in the R groups. In STIS, a significant increase in DNA strand breaks of the lung cells exposed to 0.5 mg/m3 of SiO2_7 or 50 mg/m3 of TiO2_NM105 was observed in both groups. The detected gene expression changes suggest that oxidative stress and/or inflammation pathways are likely implicated in the induction of (oxidative) DNA damage. Overall, all tested aSiO2 NM were not associated with marked in vivo toxicity following instillation or STIS. The genotoxicity findings for SiO2_7 from instillation and STIS are concordant; however, changes in STIS animals were more permanent/difficult to revert.

Safety and efficacy of a feed additive consisting of titanium dioxide for all animal species (Titanium Dioxide Manufacturers Association)

Following a request from the European Commission, the EFSA was asked to deliver a scientific opinion on the safety and efficacy of titanium dioxide (TiO2) for all animal species. TiO2 is applied to be used as a sensory additive (functional group: colourants; i) substances that add or restore colour in feedingstuffs). The specification for TiO2 used as feed additive meets the specifications of TiO2 used as food additive. The EFSA Panel on Food Additive and Flavourings (FAF) concluded that TiO2 (E171) can no longer be considered as safe when used as a food additive. The EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) endorses this conclusion and considers that it also applies to TiO2 as a feed additive for all animal species. TiO2 is absorbed to a low extent; however, particles of TiO2 can accumulate in the body due to their long half-life. The genotoxicity of TiO2 particles cannot be ruled out raising potential concerns on the safety of the additive for the target species (especially for long-living animals and reproductive animals), consumers and user. Considering this fact and the absence of specific data related to its use as a feed additive, the Panel cannot conclude on the safety of TiO2 for the target species, consumers and environment. In the absence of studies with the additive under assessment, the Panel cannot conclude on the assessment of the effects of the additive on eyes and skin. TiO2 is potentially carcinogenic to workers if inhaled. The concern for genotoxicity of TiO2 particles cannot be ruled out, this should be considered as an additional potential concern to users handling the additive. TiO2 is efficacious in colouring the food for cats and dogs at a minimum content of 1%.

Can nanomaterials induce reproductive toxicity in male mammals? A historical and critical review

The nanotechnology enabled the development of nanomaterials (NMs) with a variety of industrial, biomedical, and consumer applications. However, the mechanism of action (MoA) and toxicity of NMs remain unclear, especially in the male reproductive system. Thus, this study aimed to perform a bibliometric and systematic review of the literature on the toxic effects of different types of NMs on the male reproductive system and function in mammalian models. A series of 236 articles related to the in vitro and in vivo reproductive toxicity of NMs in mammalian models were analyzed. The data concerning the bioaccumulation, experimental conditions (types of NMs, species, cell lines, exposure period, and routes of exposure), and the MoA and toxicity of NMs were summarized and discussed. Results showed that this field of research began in 2005 and has experienced an exponential increase since 2012. Revised data confirmed that the NMs have the ability to cross the blood-testis barrier and bioaccumulate in several organs of the male reproductive system, such as testis, prostate, epididymis, and seminal vesicle. A similar MoA and toxicity were observed after in vitro and in vivo exposure to NMs. The NM reproductive toxicity was mainly related to ROS production, oxidative stress, DNA damage and apoptosis. In conclusion, the NM exposure induces bioaccumulation and toxic effects on male reproductive system of mammal models, confirming its potential risk to human and environmental health. The knowledge concerning the NM reproductive toxicity contributes to safety and sustainable use of nanotechnology.

Safety assessment of titanium dioxide (E171) as a food additive

The present opinion deals with an updated safety assessment of the food additive titanium dioxide (E 171) based on new relevant scientific evidence considered by the Panel to be reliable, including data obtained with TiO2 nanoparticles (NPs) and data from an extended one-generation reproductive toxicity (EOGRT) study. Less than 50% of constituent particles by number in E 171 have a minimum external dimension < 100 nm. In addition, the Panel noted that constituent particles < 30 nm amounted to less than 1% of particles by number. The Panel therefore considered that studies with TiO2 NPs < 30 nm were of limited relevance to the safety assessment of E 171. The Panel concluded that although gastrointestinal absorption of TiO2 particles is low, they may accumulate in the body. Studies on general and organ toxicity did not indicate adverse effects with either E 171 up to a dose of 1,000 mg/kg body weight (bw) per day or with TiO2 NPs (> 30 nm) up to the highest dose tested of 100 mg/kg bw per day. No effects on reproductive and developmental toxicity were observed up to a dose of 1,000 mg E 171/kg bw per day, the highest dose tested in the EOGRT study. However, observations of potential immunotoxicity and inflammation with E 171 and potential neurotoxicity with TiO2 NPs, together with the potential induction of aberrant crypt foci with E 171, may indicate adverse effects. With respect to genotoxicity, the Panel concluded that TiO2 particles have the potential to induce DNA strand breaks and chromosomal damage, but not gene mutations. No clear correlation was observed between the physico-chemical properties of TiO2 particles and the outcome of either in vitro or in vivo genotoxicity assays. A concern for genotoxicity of TiO2 particles that may be present in E 171 could therefore not be ruled out. Several modes of action for the genotoxicity may operate in parallel and the relative contributions of different molecular mechanisms elicited by TiO2 particles are not known. There was uncertainty as to whether a threshold mode of action could be assumed. In addition, a cut-off value for TiO2 particle size with respect to genotoxicity could not be identified. No appropriately designed study was available to investigate the potential carcinogenic effects of TiO2 NPs. Based on all the evidence available, a concern for genotoxicity could not be ruled out, and given the many uncertainties, the Panel concluded that E 171 can no longer be considered as safe when used as a food additive.

High-Throughput Screening Platform for Nanoparticle-Mediated Alterations of DNA Repair Capacity

The potential genotoxic effects of engineered nanomaterials (ENMs) may occur through the induction of DNA damage or the disruption of DNA repair processes. Inefficient DNA repair may lead to the accumulation of DNA lesions and has been linked to various diseases, including cancer. Most studies so far have focused on understanding the nanogenotoxicity of ENM-induced damages to DNA, whereas the effects on DNA repair have been widely overlooked. The recently developed fluorescence multiplex-host-cell reactivation (FM-HCR) assay allows for the direct quantification of multiple DNA repair pathways in living cells and offers a great opportunity to address this methodological gap. Herein an FM-HCR-based method is developed to screen the impact of ENMs on six major DNA repair pathways using suspended or adherent cells. The sensitivity and efficiency of this DNA repair screening method were demonstrated in case studies using primary human small airway epithelial cells and TK6 cells exposed to various model ENMs (CuO, ZnO, and Ga2O3) at subcytotoxic doses. It was shown that ENMs may inhibit nucleotide-excision repair, base-excision repair, and the repair of oxidative damage by DNA glycosylases in TK6 cells, even in the absence of significant genomic DNA damage. It is of note that the DNA repair capacity was increased by some ENMs, whereas it was suppressed by others. Overall, this method can be part of a multitier, in vitro hazard assessment of ENMs as a functional, high-throughput platform that provides insights into the interplay of the properties of ENMs, the DNA repair efficiency, and the genomic stability.

Toxicological Consequences of Titanium Dioxide Nanoparticles (TiO2NPs) and Their Jeopardy to Human Population

Titanium dioxide nanoparticles (TiO2 NPs) are the most produced nanomaterial for food additives, pigments, photocatalysis, and personal care products. These nanomaterials are at the forefront of rapidly developing indispensable nanotechnology. In all these nanomaterials, titanium dioxide (TiO2) is the most common nanomaterial which is being synthesized for many years. These nanoparticles of TiO2 are widely used at the commercial level, especially in cosmetic industries. High usage in such a way has increased the toxicological consequences of the human population. Several studies have shown that TiO2 NPs accumulated after oral exposure or inhalation in the alimentary canal, lungs, heart, liver, spleen, cardiac muscle, and kidneys. Additionally, in mice and rats, they disturb glucose and lipid homeostasis. Moreover, TiO2 nanoparticles primarily cause adverse reactions by inducing oxidative stress that leads to cell damage, inflammation, genotoxicity, and adverse immune responses. The form and level of destruction are strongly based on the physical and chemical properties of TiO2 nanoparticles, which administer their reactivity and bioavailability. Studies give indications that TiO2 NPs cause both DNA strand breaks and chromosomal damages. The effects of genotoxicity do not depend only on particle surface changes, size, and exposure route, but also relies on the duration of exposure. Most of these effects may be because of a very high dose of TiO2 NPs. Despite increased production and use, epidemiological data for TiO2 NPs is still missing. This review discusses previous research regarding the impact of TiO2 NP toxicity on human health and highlights areas that require further understanding in concern of jeopardy to the human population. This review is important to point out areas where extensive research is needed; thus, their possible impact on individual health should be investigated in more details.

Oxidative and/or Inflammatory Thrust Induced by Silver Nanoparticles in Rabbits: Effect of Vitamin E or NSAID Administration on Semen Parameters

The aim of this research was to evaluate the inflammatory and/or oxidative damage related to silver nanoparticles (AgNPs), which are responsible for negative effects on sperm physiology and metabolism. Thirty New Zealand White rabbit bucks were divided into 5 experimental groups (6 animals/group): Control, treated with 0.9% NaCl; AgNP, treated with a 5 mM AgNP solution; LPS, treated with 50 g/kg b.w. E. coli LPS; AgNPs + NSAID, treated with an anti-inflammatory drug at 0.2 mg/kg b.w. and 5 mM AgNPs; and AgNPs + Vit E, treated with 0.18 mg/kg b.w. vitamin E and 5 mM AgNPs. Sperm quality and oxidative and inflammatory status were assessed at different times (0-60 days). Two statistical models were built: the first evaluated the effects of AgNPs and LPS (vs. Control), whereas the second evaluated the protective effect of an NSAID and vitamin E against AgNP-induced damage. Three principal component analyses were performed: sperm traits (motility, volume), oxidative status (antioxidants, oxidative metabolites, and redox reactions), and cytokines (TNF-α, IL-8, and IL-6). A negative effect on reproductive traits resulted after NP administration. In particular, an inflammatory/oxidative response took place in the reproductive tract during the first 2-3 wks of AgNP administration (cytokine and oxidative metabolite generation); the inflammatory/oxidative thrust impaired the status of rabbit tissues (seminal plasma, sperm, and blood), inducing a response (increased antioxidant enzymes and redox reactions) at 4-7 wks; oxidative stress, if not totally counteracted, likely induced toxicity in the late phases of AgNP administration (8-9 wks). In conclusion, exposure to silver nanoparticles produced a similar but more persistent effect than that of LPS on rabbit reproductive tissues: AgNP administration triggered a proinflammatory response linked to oxidative thrust, worsening many sperm parameters. However, only anti-inflammatory treatment counteracted the negative effects of AgNPs, whereas vitamin E seemed to act as an adjuvant, attenuating the oxidative cascade.

The enzyme-modified comet assay: Past, present and future

The enzyme-modified comet assay was developed in order to detect DNA lesions other than those detected by the standard version (single and double strand breaks and alkali-labile sites). Various lesion-specific enzymes, from the DNA repair machinery of bacteria and humans, have been combined with the comet assay, allowing detection of different oxidized and alkylated bases as well as cyclobutane pyrimidine dimers, mis-incorporated uracil and apurinic/apyrimidinic sites. The enzyme-modified comet assay has been applied in different fields - human biomonitoring, environmental toxicology, and genotoxicity testing (both in vitro and in vivo) - as well as in basic research. Up to now, twelve enzymes have been employed; here we describe the enzymes and give examples of studies in which they have been applied. The bacterial formamidopyrimidine DNA glycosylase (Fpg) and endonuclease III (EndoIII) have been extensively used while others have been used only rarely. Adding further enzymes to the comet assay toolbox could potentially increase the variety of DNA lesions that can be detected. The enzyme-modified comet assay can play a crucial role in the elucidation of the mechanism of action of both direct and indirect genotoxins, thus increasing the value of the assay in the regulatory context.

Exposure to silver nanoparticles induces immunological dysfunction in pregnant mice

The adverse outcomes of silver nanoparticles (AgNPs) on pregnancy have been studied in murine animals. However, the potential toxicity of AgNPs to immune balance, which is essential for maintaining a normal pregnancy, still requires further exploration. Therefore, this study assessed the effect of AgNPs on the immune balance during gestation time. Pregnant mice were given a dose of 1 mg/kg of AgNPs and silver ion on gestation days 3.5 to 9.5 by tail vein injection. Results showed that the AgNPs and silver ion decreased the number of CD4⁺ CD25⁺ Treg cells which were the important cells in the immune system, thereby disrupting the balance of normal immune tolerance function, activated the inflammatory responses, together with the reductive production of placental immunoregulatory genes, and the expression of inflammatory factors in the placenta in the Ag-treated groups increased. These effects increased the absorption rate. Furthermore, the inflammatory signaling pathway p38MAPK/AP-1/MMP-9 in the placenta was activated, indicating that Ag induced inflammation through this signaling pathway. All results indicated that undesirable pregnancy outcome caused by AgNPs could be happened by stimulating immunological dysfunction. Therefore, the potential risks to embryogenesis exposure to AgNPs that caused immune imbalance should be given sufficient attention.

Titanium dioxide nanoparticle genotoxicity: A review of recent in vivo and in vitro studies

Titanium dioxide nanoparticles (TiO2 NPs, size <100 nm) find applications in a wide range of products including food and cosmetics. Studies have found that exposure to TiO2 NPs can cause inflammation, cytotoxicity, genotoxicity and cell apoptosis. In this article, we have reviewed the recent literature on the potential of TiO2 NPs to cause genotoxicity and summarized the results of two standard genotoxicity assays, the comet and micronucleus (MN) assays. Analysis of these peer-reviewed publications shows that the comet assay is the most common genotoxicity test, followed by MN, Ames, and chromosome aberration tests. These assays have reported positive as well as negative results, although there is inconsistency in some results that need to be confirmed further by well-designed experiments. We also discuss the possible mechanisms of TiO2 NP genotoxicity and point out areas that warrant further research.

Rethinking Nano-TiO2 Safety: Overview of Toxic Effects in Humans and Aquatic Animals

Titanium dioxide nanoparticles (nano-TiO₂ ) are widely used in consumer products, raising environmental and health concerns. An overview of the toxic effects of nano-TiO₂ on human and environmental health is provided. A meta-analysis is conducted to analyze the toxicity of nano-TiO₂ to the liver, circulatory system, and DNA in humans. To assess the environmental impacts of nano-TiO₂ , aquatic environments that receive high nano-TiO₂ inputs are focused on, and the toxicity of nano-TiO₂ to aquatic organisms is discussed with regard to the present and predicted environmental concentrations. Genotoxicity, damage to membranes, inflammation and oxidative stress emerge as the main mechanisms of nano-TiO₂ toxicity. Furthermore, nano-TiO₂ can bind with free radicals and signal molecules, and interfere with the biochemical reactions on plasmalemma. At the higher organizational level, nano-TiO₂ toxicity is manifested as the negative effects on fitness-related organismal traits including feeding, reproduction and immunity in aquatic organisms. Bibliometric analysis reveals two major research hot spots including the molecular mechanisms of toxicity of nano-TiO₂ and the combined effects of nano-TiO₂ and other environmental factors such as light and pH. The possible measures to reduce the harmful effects of nano-TiO₂ on humans and non-target organisms has emerged as an underexplored topic requiring further investigation.

Coexposed nanoparticulate Ag alleviates the acute toxicity induced by ionic Ag+in vivo

Health concerns of silver nanoparticles (AgNPs) emerged with the increase of their industrial and biomedical application and thus human exposure. The highly dynamic properties of AgNPs lead to coexposure to nanoparticulate and ionic silver, and the combined effects of different Ag species might alter their individual toxicity. Herein, the toxicity of AgNPs combined with ionic Ag⁺ toward the rat was investigated after intravenous (i.v.) exposure to either AgNPs (5 mg/kg), Ag⁺ (5 mg/kg), or a mixture of Ag⁺ and AgNPs (5 mg/kg for both). Comparable results by histopathological and biochemical studies revealed that the exposure to individual AgNPs causes no apparent toxicity in rats, while Ag⁺ ions at the same dose induced marked acute toxicity. More importantly, while there was a negligible combined effect on the Ag accumulation, the less toxic AgNPs ameliorated Ag⁺ induced toxicity to rat organs after coexposure to the mixture of Ag⁺ and AgNPs, which might result from the complexation of Ag⁺ with the thiols like metallothioneins. Therefore, the combined toxicity of particulate and ionic Ag was complicated by their individual toxicities and also their interaction with intracellular detoxification biomolecules, regardless of differences in Ag accumulation. Although further investigations are still needed for the potential toxic mechanisms of the coexposed AgNPs and Ag⁺, considerations of the combined toxicity of different Ag species will reflect more accurate assessments of their health impacts.

Zinc Oxide Nanoparticles Damage Tobacco BY-2 Cells by Oxidative Stress Followed by Processes of Autophagy and Programmed Cell Death

Nanomaterials, including zinc oxide nanoparticles (ZnO NPs), have a great application potential in many fields, such as medicine, the textile industry, electronics, and cosmetics. Their impact on the environment must be carefully investigated and specified due to their wide range of application. However, the amount of data on possible negative effects of ZnO NPs on plants at the cellular level are still insufficient. Thus, we focused on the effect of ZnO NPs on tobacco BY-2 cells, i.e., a widely accepted plant cell model. Adverse effects of ZnO NPs on both growth and biochemical parameters were observed. In addition, reactive oxygen and nitrogen species visualizations confirmed that ZnO NPs may induce oxidative stress. All these changes were associated with the lipid peroxidation and changes in the plasma membrane integrity, which together with endoplasmatic reticulum and mitochondrial dysfunction led to autophagy and programmed cell death. The present study demonstrates that the phytotoxic effect of ZnO NPs on the BY-2 cells is very complex and needs further investigation.

Telomere length and genotoxicity in the lung of rats following intragastric exposure to food-grade titanium dioxide and vegetable carbon particles

Vegetable carbon (E153) and titanium dioxide (E171) are widely used as black and white food colour additives. The aim of this study was to assess gastrointestinal tight junction and systemic genotoxic effects in rats following exposure to E153 and E171 for 10 weeks by oral gavage once a week. The expression of tight junction proteins was assessed in intestinal tissues. Levels of DNA strand breaks, oxidatively damaged DNA and telomere length were assessed in secondary organs. Hydrodynamic suspensions of E153 and E173 indicated mean particles sizes of 230 and 270 nm, respectively, and only E153 gave rise to intracellular production of reactive oxygen species in colon epithelial (Caco-2) cells. Rats exposed to E153 (6.4 mg/kg/week) or E171 (500 mg/kg/week) had decreased gene expression of the tight junction protein TJP1 (P < 0.05). E153 (6.4 mg/kg/week) also decreased OCLN (P < 0.05) in the colon and occludin protein expression in the small intestine (P < 0.05). Furthermore, E153 or E171 exposed rats had shorter telomeres in the lung (P < 0.05). Plasma from particle-exposed rats also produced telomere shortening in cultured lung epithelial cells. There were unaltered levels of oxidatively damaged DNA in the liver and lung and no changes in the DNA repair activity of oxidatively damaged DNA in the lung. Altogether, these results indicate that intragastric exposure to E153 and E171 is associated with reduced tight junction protein expression in the intestinal barrier and telomere length shortening in the lung in rats.

The role of the enzyme-modified comet assay in in vivo studies

The in vivo comet assay is an established genotoxicity test, with an OECD test guideline, but in its standard form it measures only DNA strand breaks. Including in the assay an additional step, in which the DNA is incubated with a lesion-specific enzyme, can provide important information about the nature of the DNA damage. Formamidopyrimidine DNA glycosylase, 8-oxoguanine DNA glycosylase or endonuclease III are commonly used in the in vitro genotoxicity test and in human biomonitoring to detect oxidised bases, but in vivo applications are rarer. A systematic literature search has identified a total of 60 papers that report such in vivo experiments, testing a variety of agents. In many cases, strand breaks were not seen, but significant levels of enzyme-sensitive sites were induced - indicating a mechanism of action involving oxidative stress. Compounds such as methyl methanesulfonate (MMS) or ethyl methanesulfonate (EMS) could be used as positive controls in both the standard and the enzyme-modified in vivo comet assays.

Metagenomic analysis of the biotoxicity of titanium dioxide nanoparticles to microbial nitrogen transformation in constructed wetlands

Extensive use of titanium dioxide nanoparticles (TiO₂ NPs) in various products has increased the release of these particles into wastewater, posing potential environmental risks. As an ecological wastewater treatment facility, constructed wetland (CW) is an important sink of NPs. However, little is known about the effects of NPs on microbial nitrogen transformation and related genes in CWs. In this study, short-term (5 days) and long-term (60 days) exposure experiments were conducted to investigate the effect of TiO₂ NPs (0, 1, and 50 mg/L) on microbial nitrogen removal in CWs. The results showed that nitrogen removal efficiency was decreased by 35%-51% after long-term exposure to TiO₂ NPs. Metagenomic analysis further confirmed that TiO₂ NPs declined the relative abundance of functional genes and those enzyme encoding genes involved in the nitrogen metabolism pathway and glycolysis metabolism process. Furthermore, our data proved that the indigent glycolysis metabolism process resulted in the shortage of electron (NADH) and energy sources (ATP), causing inefficient nitrogen removal. Overall, these results revealed that the accumulation of TiO₂ NPs altered the genetic expression of biofilm in CWs, which had significant impacts on biological nitrogen transformation.

Genotoxicity of Silver Nanoparticles

Silver nanoparticles (AgNPs) are widely used in diverse sectors such as medicine, food, cosmetics, household items, textiles and electronics. Given the extent of human exposure to AgNPs, information about the toxicological effects of such products is required to ensure their safety. For this reason, we performed a bibliographic review of the genotoxicity studies carried out with AgNPs over the last six years. A total of 43 articles that used well-established standard assays (i.e., in vitro mouse lymphoma assays, in vitro micronucleus tests, in vitro comet assays, in vivo micronucleus tests, in vivo chromosome aberration tests and in vivo comet assays), were selected. The results showed that AgNPs produce genotoxic effects at all DNA damage levels evaluated, in both in vitro and in vivo assays. However, a higher proportion of positive results was obtained in the in vitro studies. Some authors observed that coating and size had an effect on both in vitro and in vivo results. None of the studies included a complete battery of assays, as recommended by ICH and EFSA guidelines, and few of the authors followed OECD guidelines when performing assays. A complete genotoxicological characterization of AgNPs is required for decision-making.

Effect of Phosphate, Sulfate, Arsenate, and Pyrite on Surface Transformations and Chemical Retention of Gold Nanoparticles (Au-NPs) in Partially Saturated Soil Columns

The understanding of engineered nanoparticle (ENP) fate and transport in soil-water environments is important for the evaluation of potential risks of ENPs to the ecosystem and human health. The effects of pyrite grains and three types of oxyanions-sulfate, phosphate, and arsenate-on the retention of citrate-coated gold nanoparticles (citrate-Au-NPs) were studied in partially saturated soil column experiments. The mobility of Au-NP was found to be in the order: Au-NP-sulfide (originating from pyrite) > Au-NP-sulfate > citrate-Au-NP > Au-NP-arsenate > Au-NP-phosphate. Chemical retention mechanisms, including hydrogen bonding and calcium bridging, are proposed and discussed. The retention of Au-NPs in soil columns increases with the increased ability of transformed Au-NP surfaces to create strong hydrogen bonding through adsorbed oxyanions with soil surfaces. Oxyanions were also found to reduce aggregation and aggregate size of Au-NPs upon interaction with Ca²⁺ solution. While the effects of cationic substances on ENP transport and stability have been studied frequently, the results here demonstrate that anionic substances have a substantial effect on Au-NP transport and stability. Furthermore, this study highlights the importance of examining ENPs under environmentally relevant condition, and the significant effect of ENP transformations on their mobility in soils.

Biphasic adverse effect of titanium nanoparticles on testicular function in mice

The male reproductive system is being recognized as toxic targets of nanoparticles including titanium dioxide nanoparticles (TiNP). Most of these reports are, however, obtained from the results of long-term exposure of TiNP. In this study, we diversely examined the acute effects of TiNP on the male reproductive system. Male C57BL/6J mice were administered a single intravenous injection of TiNP (10, 50 mg/kg), and were sacrificed at 1, 3, and 9 days post-injection. Testicular functions (estimated by sperm motility and sperm number) were measured via computer-assisted sperm analysis (CASA). Results indicated that sperm motility was significantly reduced from 1 day following TiNP injection (in both dose), and this reduction persisted up to 9 days post-TiNP injection (10 mg/kg injection group). Interestingly, we observed no significant decrease in sperm numbers in both the testis and the cauda epididymis in either treatment groups during the course of the experiment. Therefore, we hypothesized that TiNP may target the mature spermatozoa. In addition, sperm suspensions directly incubated with TiNP showed reduced sperm motility, [³H]-thymidine incorporation, and ATP level. Our results indicated that TiNP possesses “biphasic effects”; the obstacles to mature sperms (short term effect) in addition to the impairment in testis (long-term effect).

Protein Binding Effects of Dopamine Coated Titanium Dioxide Shell Nanoparticles

Non-targeted nanoparticles are capable of entering cells, passing through different subcellular compartments and accumulating on their surface a protein corona that changes over time. In this study, we used metal oxide nanoparticles with iron-oxide core covered with titanium dioxide shell (Fe3O4@TiO2), with a single layer of covalently bound dopamine covering the nanoparticle surface. Mixing nanoparticles with cellular protein isolates showed that these nanoparticles can form complexes with numerous cellular proteins. The addition of non-toxic quantities of nano-particles to HeLa cell culture resulted in their non-specific uptake and accumulation of protein corona on nanoparticle surface. TfRC, Hsp90 and PARP were followed as representative protein components of nanoparticle corona; each protein bound to nanoparticles with different affinity. The presence of nanoparticles in cells also mildly modulated gene expression on the level of mRNA. In conclusion, cells exposed to non-targeted nanoparticles show subtle but numerous changes that are consistent from one experiment to another.

Amelioration of titanium dioxide nanoparticle reprotoxicity by the antioxidants morin and rutin

The present study aimed to examine the ameliorative effects of morin and rutin on the reproductive toxicity induced by titanium dioxide nanoparticles (TiO₂NPs) in male rats. A total of seventy adult male Sprague-Dawley rats were randomly divided into seven groups, each comprising ten rats. Nanoreprotoxicity was induced by treating rats with TiO₂NPs at a dosage of 300 mg/kg body weight for 30 days. Morin (30 mg/kg body weight) and rutin (100 mg/kg body weight) were co-administered with or without TiO₂NPs to rats either individually or combined. Only distilled water was administered to the control group. The results showed that TiO₂NPs enhanced oxidative stress, indicated by reduced levels of antioxidants such as superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH) in testicular tissues, and increased levels of the lipid peroxidation marker malondialdehyde (MDA). TiO₂NPs significantly reduced the levels of sex hormones (testosterone, FSH, and LH), reduced sperm motility, viability, and sperm cell count, and increased sperm abnormalities, in addition to damaging the testicular histological architecture. TiO₂NPs resulted in the downregulation of 17β-HSD and the upregulation of proapoptotic gene (Bax) transcripts in the testicular tissues. Conversely, morin and/or rutin had a protective effect on testicular tissue. They effectively counteracted TiO₂NP-induced oxidative damage and morphological injury in the testis by conserving the endogenous antioxidant mechanisms and scavenging free radicals. Thus, we suggest that morin and rutin could be used to alleviate the toxicity and oxidative damage associated with TiO₂NP intake.

Toxic and Genotoxic Effects of Silver Nanoparticles in Drosophila

The in vivo model Drosophila melanogaster was used here to determine the detrimental effects induced by silver nanoparticles (AgNPs) exposure. The main aim was to explore its interaction with the intestinal barrier and the genotoxic effects induced in hemocytes. The observed effects were compared with those obtained by silver nitrate, as an agent acting via the release of silver ions. Larvae were fed in food media containing both forms of silver. Results indicated that silver nitrate was more toxic than AgNPs when the viability "egg-to-adult" was determined. Depigmentation was observed in adults including those exposed to nontoxic concentrations, as indicative of exposure action. Interestingly, AgNPs were able to cross the intestinal barrier affecting hemocytes that show significant increases in the levels of intracellular reactive oxygen species. Additionally, significant levels of genotoxic damage, as determined by the comet assay, were also induced. When the expression of different stress-response genes was determined, for both AgNPs and silver nitrate, significant upregulation of Sod2 and p53 genes was observed. Our results confirm for the first time that in an in vivo model as Drosophila, AgNPs are able to cross the intestinal barriers and produce primary DNA damage (comet assay) via oxidative stress induction. In general, the effects induced by silver nitrate were more pronounced than those induced by AgNPs what would emphasize the role of silver ions in the observed effects. Environ. Mol. Mutagen. 60:277-285, 2019. © 2018 Wiley Periodicals, Inc.

Size-dependent genotoxicity of silver, gold and platinum nanoparticles studied using the mini-gel comet assay and micronucleus scoring with flow cytometry

Metallic nanoparticles (NPs) are promising nanomaterials used in different technological solutions as well as in consumer products. Silver (Ag), gold (Au) and platinum (Pt) represent three metallic NPs with current or suggested use in different applications. Pt is also used as vehicle exhaust catalyst leading to a possible exposure via inhalation. Despite their use, there is limited data on their genotoxic potential and possible size-dependent effects, particularly for Pt NPs. The aim of this study was to explore size-dependent genotoxicity of these NPs (5 and 50 nm) following exposure of human bronchial epithelial cells. We characterised the NPs and assessed the viability (Alamar blue assay), formation of DNA strand breaks (mini-gel comet assay) and induction of micronucleus (MN) analysed using flow cytometry (in vitro microflow kit). The results confirmed the primary size (5 and 50 nm) but showed agglomeration of all NPs in the serum free medium used. Slight reduced cell viability (tested up to 50 µg/ml) was observed following exposure to the Ag NPs of both particle sizes as well as to the smallest (5 nm) Au NPs. Similarly, at non-cytotoxic concentrations, both 5 and 50 nm-sized Ag NPs, as well as 5 nm-sized Au NPs, increased DNA strand breaks whereas for Pt NPs only the 50 nm size caused a slight increase in DNA damage. No clear induction of MN was observed in any of the doses tested (up to 20 µg/ml). Taken together, by using the comet assay our study shows DNA strand breaks induced by Ag NPs, without any obvious differences in size, whereas effects from Au and Pt NPs were size-dependent in the sense that the 5 nm-sized Au NPs and 50 nm-sized Pt NPs particles were active. No clear induction of MN was observed for the NPs.

Dependence of Nanoparticle Toxicity on Their Physical and Chemical Properties

Studies on the methods of nanoparticle (NP) synthesis, analysis of their characteristics, and exploration of new fields of their applications are at the forefront of modern nanotechnology. The possibility of engineering water-soluble NPs has paved the way to their use in various basic and applied biomedical researches. At present, NPs are used in diagnosis for imaging of numerous molecular markers of genetic and autoimmune diseases, malignant tumors, and many other disorders. NPs are also used for targeted delivery of drugs to tissues and organs, with controllable parameters of drug release and accumulation. In addition, there are examples of the use of NPs as active components, e.g., photosensitizers in photodynamic therapy and in hyperthermic tumor destruction through NP incorporation and heating. However, a high toxicity of NPs for living organisms is a strong limiting factor that hinders their use in vivo. Current studies on toxic effects of NPs aimed at identifying the targets and mechanisms of their harmful effects are carried out in cell culture models; studies on the patterns of NP transport, accumulation, degradation, and elimination, in animal models. This review systematizes and summarizes available data on how the mechanisms of NP toxicity for living systems are related to their physical and chemical properties.

Simultaneous size characterization and mass quantification of the in vivo core-biocorona structure and dissolved species of silver nanoparticles

Size characterization of silver nanoparticles with biomolecule corona (AgNP@BCs) and mass quantification of various silver species in organisms are essential for understanding the in vivo transformation of AgNPs. Herein, we report a versatile method that allows simultaneous determination of the size of AgNP@BCs and mass concentration of various silver species in rat liver. Both particulate and ionic silver were extracted in their original forms from the organs by alkaline digestion, and analyzed by size exclusion chromatography combined with inductively coupled plasma mass spectrometry (SEC-ICP-MS). While the silver mass concentrations were quantified by ICP-MS with a detection limit of 0.1μg/g, the effective diameter of AgNP@BCs was determined based on the retention time in SEC separation with size discrimination of 0.6-3.3nm. More importantly, we found that the BC thickness of AgNP@BCs is core size independent, and a linear correlation was found between the effective diameter and core diameter of AgNP@BCs in extracted tissues, which was used to calibrate the core diameter with standard deviations in the range of 0.2-1.1nm. The utility of this strategy was demonstrated through application to rat livers in vivo. Our method is powerful for investigating the transformation mechanism of AgNPs in vivo.

Silver Nanoparticles in the Lung: Toxic Effects and Focal Accumulation of Silver in Remote Organs

The distribution of silver (Ag) into remote organs secondary to the application of Ag nanoparticles (Ag-NP) to the lung is still incompletely understood and was investigated in the rat with imaging methods. Dose-finding experiments were carried out with 50 nm- or 200 nm-sized polyvinyl pyrrolidine (PVP)-coated Ag-NP using alveolar macrophages in vitro and female rats, which received Ag-NP via intratracheal instillation. In the main study, we administered 37.5–300 µg per rat lung of the more toxic Ag50-PVP and assessed the broncho-alveolar lavage fluid (BALF) for inflammatory cells, total protein and fibronectin after three and 21 days. In parallel, lung tissue was analysed for DNA double-strand breaks and altered cell proliferation. While 75–150 µg Ag50-PVP per rat lung caused a reversible inflammation, 300 µg led to DNA damage, accelerated cell proliferation and progressively increasing numbers of neutrophilic granulocytes. Ag accumulation was significant in homogenates of liver and other peripheral organs upon lung dose of ≥75 µg. Quantitative laser-ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS) combined with enhanced dark field microscopy and autometallography revealed focal accumulations of Ag and/or Ag-NP in sections of peripheral organs: mediastinal lymph nodes contained Ag-NP especially in peripheral macrophages and Ag in argyrophilic fibres. In the kidney, Ag had accumulated within proximal tubuli, while renal filter structures contained no Ag. Discrete localizations were also observed in immune cells of liver and spleen. Overall, the study shows that concentrations of Ag-NP, which elicit a transient inflammation in the rat lung, lead to focal accumulations of Ag in peripheral organs, and this might pose a risk to particular cell populations in remote sites.