The effect of three additives on properties of mineral trioxide aggregate cements: a systematic review and meta-analysis of in vitro studies

BACKGROUND

Several efforts have been made to improve mechanical and biological properties of calcium silicate-based cements through changes in chemical composition of the materials. This study aimed to investigate the physical (including setting time and compressive strength) and chemical (including calcium ion release, pH level) properties as well as changes in cytotoxicity of mineral trioxide aggregate (MTA) after the addition of 3 substances including CaCl2, Na2HPO4, and propylene glycol (PG).

METHODS

The systematic review was conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). Electronic searches were performed on PubMed, Embase, and Scopus databases, spanning from 1993 to October 2023 in addition to manual searches. Relevant laboratory studies were included. The quality of the included studies was assessed using modified ARRIVE criteria. Meta-analyses were performed by RevMan statistical software.

RESULTS

From the total of 267 studies, 24 articles were included in this review. The results of the meta-analysis indicated that addition of PG increased final setting time and Ca2+ ion release. Addition of Na2HPO4 did not change pH and cytotoxicity but reduced the final setting time. Incorporation of 5% CaCl2 reduced the setting time but did not alter the cytotoxicity of the cement. However, addition of 10% CaCl2 reduced cell viability, setting time, and compressive strength.

CONCLUSION

Inclusion of 2.5% wt. Na2HPO4 and 5% CaCl2 in MTA can be advisable for enhancing the physical, chemical, and cytotoxic characteristics of the admixture. Conversely, caution is advised against incorporating elevated concentrations of PG due to its retarding effect.

TRIAL REGISTRATION

PROSPERO registration number: CRD42021253707.

Cytotoxicity prediction of nano metal oxides on different lung cells via Nano-QSAR

In recent years, nanomaterials have found extensive applications across diverse domains owing to their distinctive physical and chemical characteristics. It is of great importance in theoretical and practical terms to carry out the relationship between structural characteristics of nanomaterials and different cytotoxicity and to achieve practical assessment and prediction of cytotoxicity. This study investigated the intrinsic quantitative constitutive relationships between the cytotoxicity of nano-metal oxides on human normal lung epithelial cells and human lung adenocarcinoma cells. We first employed quasi-SMILES-based nanostructural descriptors by selecting the five physicochemical properties that are most closely related to the cytotoxicity of nanometal oxides, then established SMILES-based descriptors that can effectively describe and characterize the molecular structure of nanometal oxides, and then built the corresponding Nano-Quantitative Structure-Activity Relationship (Nano-QSAR) prediction models, finally, combined with the theory of reactive oxygen species (ROS) biotoxicity, to reveal the mechanism of toxicity and differences between the two cell types. The established model can efficiently and accurately predict the properties of targets, reveal the corresponding toxicity mechanisms, and guide the safe design, synthesis, and application of nanometal oxides.

Dynamic interplay of metal and metal oxide nanoparticles with plants: Influencing factors, action mechanisms, and assessment of stimulatory and inhibitory effects

Nanoparticles (NPs) of metals and metal oxides have received increasing attention regarding their characteristic behavior in plant systems. The fate and transport of metal NPs and metal oxide NPs in plants is of emerging concern for researchers because they ultimately become part of the food chain. The widespread use of metal-based NPs (MBNPs) in plants has revealed their beneficial and harmful effects. This review addresses the main factors affecting the uptake, translocation, absorption, bioavailability, toxicity, and accumulation of MBNPs in different plant species. It appraises the mechanism of nanoparticle-plant interaction in detail and provides understanding of the estimation strategies for the associated pros and cons with this interplay. Critical parameters of NPs include, but are not limited to, particle size and shape, surface chemistry, surface charge, concentration, solubility, and exposure route. On exposure to MBNPs, the molecular, physiological, and biochemical reactions of plants have been assessed. We have filled knowledge gaps and answered research questions regarding the positive and negative effects of metal and metal oxide NPs on seed germination, callus induction, growth and yield of plant, nutritional content, antioxidants, and enzymes. Besides, the phytotoxicity, cytotoxicity, genotoxicity, and detoxification studies of MBNPs in plants have been outlined. Furthermore, the recent developments and future perspectives of the two-way traffic of interplay of MBNPs and plants have been provided in this comprehensive review.

Toxicokinetics of rare earth element oxides administered intravenously to rats

Rare earth elements (REEs) are increasingly used in a wide range of applications. However, their toxicokinetic behaviors in animals and humans are not yet fully documented, hindering health risk assessments. We used a rat experimental model to provide novel data on the toxicokinetics of the insoluble oxide forms of praseodymium (Pr), neodymium (Nd), cerium (Ce) and yttrium (Y) administered intravenously. Detailed blood, urinary and fecal time courses were documented through serial sampling over 21 days in male Sprague-Dawley rats exposed to a mixture of these REE oxides administered at two different doses (0.3 or 1 mg kg-1 bw of each REE oxide commercially sold as bulk μm-sized particles). Tissue REE levels at the time of sacrifice were also measured. Significant effects of the dose on REE time courses in blood and on cumulative urinary and fecal excretion rates were observed for all four REE oxides assessed, as lower cumulative excretion rates were noted at the higher REE dose. In the liver, the main accumulation organ, the fraction of the administered REE dose remaining in the tissue at necropsy was similar at both doses. Toxicokinetic data for the REE oxides were compared to similar data for their chloride salts (also administered intravenously in a mixture, at 0.3 and 1 mg kg-1 bw of each REE chloride) obtained from a previous study. Compared to their chloride counterparts, faster elimination of REE oxides from the blood was observed in the first hours post-dosing. Furthermore, higher mean residence time (MRT) values as well as slower cumulative urinary and fecal excretion were determined for the REE oxides. Also, while liver REE retention was similar for both REE forms, the fractions of the administered REEs recovered in the spleen and lungs were noticeably higher for the REE oxides, at both dose levels. This study highlights the importance of both the dose and form of the administered REEs on their toxicokinetic profiles. Results indicate that chronic exposure and increased doses of REEs may favor bioaccumulation in the body, in particular for insoluble oxide forms of REEs, which are eliminated more slowly from the body.

Evaluation of the genotoxicity, cytotoxicity, and bioactivity of calcium silicate-based cements

BACKGROUND

As calcium silicate-based cements (CSCs) have found success in various vital pulp therapy applications, several new CSC products have emerged. This study aimed to assess the genotoxicity, cytotoxicity, and bioactivity of four CSCs by comparing the newly introduced materials Bio MTA+ and MTA Cem with previously studied materials, Biodentine and NeoMTA.

METHODS

Genotoxicity was evaluated using the micronucleus (MN) assay in human peripheral blood lymphocyte cells, measuring MN frequency and nuclear division index (NDI). Cytotoxicity was assessed in human dental pulp stem cells through the Water-Soluble Tetrazolium Salt-1 (WST-1) colorimetric assay. Bioactivity was determined by ELISA, measuring the levels of angiogenic and odontogenic markers (BMP-2, FGF-2, VEGF, and ALP). Statistical analyses included ANOVA, Dunnet and Sidak tests, and Wald chi-square test. (p < .05).

RESULTS

The MN frequency in the groups was significantly lower than that in the positive control group (tetraconazole) (p < .05). NDI values decreased with increasing concentration (p < .05). Bio MTA+ and NeoMTA showed decreased cell viability at all concentrations in 7-day cultures (p < .01). All materials increased BMP-2, FGF-2, and VEGF levels, with Biodentine and NeoMTA showing the highest levels of BMP-2 and FGF-2 on day 7. Biodentine displayed the highest VEGF levels on day 7. Biodentine and NeoMTA groups exhibited significantly higher ALP activity than the Bio MTA+ and MTA Cem groups by day 7.

CONCLUSION

Bio MTA+ and MTA Cem demonstrated no genotoxic or cytotoxic effects. Moreover, this study revealed bioactive potentials of Bio MTA+ and MTA Cem by enhancing the expression of angiogenic and osteogenic growth factors.

The protective impact of curcumin, vitamin D and E along with manganese oxide and Iron (III) oxide nanoparticles in rats with scrotal hyperthermia: Role of apoptotic genes, miRNA and circRNA

BACKGROUND

Infertility is one of the major factors affecting most people around the world. Short-term exposure to high temperatures can cause hyperthermia, which is one of the causes of male infertility. The aim of this study was to investigate the protective effect of curcumin, vitamins D and E along with Iron (III) oxide nanoparticles (Fe2O3-NPs) and manganese oxide nanoparticles (MnO2-NPs) on semen parameters and its effect on miRNA21 and circRNA0001518 expression.

MATERIAL AND METHODS

In this study, the lower part of the rat was exposed to 43 °C for 5 weeks every other day for 5 weeks. Then the animals were killed. Tissue samples were collected for sperm parameters analysis, and tissue samples were taken for evaluation of apoptosis levels in germ cells, and RNA extraction in order to examine the expression of Bax, Bcl-2, miRNA, and CircRNA genes.

RESULTS

The results of this study showed that administration of curcumin, vitamin D, and vitamin E with Fe2O3-NPs and MnO2-NPs can improve the parameters of semen, Bax gene expression, Bcl-2 as well as miRNA and CircRNA in rats with testicular hyperthermia. In addition, curcumin by reducing the toxicity of Fe2O3 nanoparticles was able to reduce its negative effects and also reduce apoptosis in germ cells. This decrease in apoptosis was attributed to decreased Bcl-2 gene expression and increased expression of Bax, miRNA-21, and circRNA0001518.

CONCLUSION

All the results of this study confirmed that Fe2O3-NPs and Mno2-NPs containing antioxidants or vitamins are useful in improving fertility in rats due to scrotal hyperthermia. Although Fe2O3-NPs and Mno2-NPs containing both antioxidants and vitamins had a greater effect on improving fertility and reducing the toxic effects of nanoparticles.

Vitamin C enhances the sensitivity of osteosarcoma to arsenic trioxide via inhibiting aerobic glycolysis

Osteosarcoma (OS) is a common malignant tumor disease in the department of orthopedics, which is prone to the age of adolescents and children under 20 years old. Arsenic trioxide (ATO), an ancient poison, has been reported to play a critical role in a variety of tumor treatments, including OS. However, due to certain poisonous side effects such as cardiotoxicity and hepatotoxicity, clinical application of ATO has been greatly limited. Here we report that low doses of ATO (1 μM) observably reduced the half-effective inhibitory concentration (IC50) of vitamin C on OS cells. Compared with the treatment alone, the synthetic application of vitamin C (VitC, 800 μM) and ATO (1 μM) significantly further inhibited the proliferation, migration, and invasion of OS cells and promoted cell apoptosis in vitro. Meanwhile, we observed that the combined application of VitC and ATO directly suppresses the aerobic glycolysis of OS cells with the decreased production of pyruvate, lactate, and ATP via inhibiting the expression of the critical glycolytic genes (PGK1, PGM1, and LDHA). Moreover, the combination of VitC (200 mg/kg) and ATO (1 mg/kg) with tail vein injection significantly delayed OS growth and migration of nude mice by inhibiting aerobic glycolysis of OS. Thus, our results demonstrate that VitC effectively increases the sensitivity of OS to low concentrations of ATO via inhibiting aerobic glycolysis to alleviate the toxic side effects of high doses of arsenic trioxide, suggesting that synthetic application of VitC and ATO is a promising approach for the clinical treatment of human OS.

Biotoxicity of Halide Perovskites in Mice

Halide perovskites are crystalline semiconductors with exceptional optoelectronic properties, rapidly developing toward large-scale applications. Lead (II) (Pb2+ ) is the core element used to prepare halide perovskites. Pb2+ can displace key 2+ elements, including calcium, zinc and iron, that regulate vital physiological functions. Sn2+ can replace Pb2+ within the perovskite structure and, if accidentally dispersed in the environment, it readily oxidizes to Sn4+ , which is compatible with physiological functions and thus potentially safe. The 3+ salt bismuth (III) (Bi3+ ) is also potentially safe for the same reason and useful to prepare double perovskites. Here, this work studies the biotoxicity of Pb, Sn, and Bi perovskites in mice for the first time. This work analyses histopathology and growth of mice directly exposed to perovskites and investigate the development of their offspring generation. This study provides the screening of organs and key physiological functions targeted by perovskite exposure to design specific studies in mammalians.

On the Mechanisms of the Cardiotoxic Effect of Lead Oxide Nanoparticles

Lead compounds are one of the most common pollutants of the workplace air and the environment. In the occupational setting, the sources of their emission, including in nanoscale form, are various technological processes associated with lead smelting and handling of non-ferrous metals and their alloys, the production of copper and batteries. Both lead poisoning and lead exposure without obvious signs of poisoning have a detrimental effect on the cardiovascular system. The purpose of this research was to investigate the mechanisms of the cardiotoxic effect of lead oxide nanoparticles (PbO NPs). The toxicological experiment involved male albino rats subchronically exposed to PbO NPs (49.6 ± 16.0 nm in size) instilled intraperitoneally in a suspension. We then assessed post-exposure hematological and biochemical parameters of blood and urine, histological and ultrastructural changes in cardiomyocytes, and non-invasively recorded electrocardiograms and blood pressure parameters in the rodents. Myocardial contractility was studied on isolated preparations of cardiac muscles. We established that PbO NPs induced oxidative stress and damage to the ultrastructure of cardiomyocytes, and decreased efficiency of the contractile function of the myocardium and blood pressure parameters. We also revealed such specific changes in the organism of the exposed rats as anemia, hypoxia, and hypocalcemia.

MnO2 nanoparticles trigger hepatic lipotoxicity and mitophagy via mtROS-dependent Hsf1Ser326 phosphorylation

Manganese (Mn) is an essential element for maintaining normal metabolism in vertebrates. Mn dioxide nanoparticles (MnO2 NPs), a novel Mn source, have shown great potentials in biological and biomedical applications due to their distinct physical and chemical properties. However, little is known about potential adverse effects on animal or cellular metabolism. Here, we investigated whether and how dietary MnO2 NPs affect hepatic lipid metabolism in vertebrates. We found that, excessive MnO2 NPs intake increased hepatic and mitochondrial Mn content, promoted hepatic lipotoxic disease and lipogenesis, and inhibited hepatic lipolysis and fatty acid β-oxidation. Moreover, excessive MnO2 NPs intake induced hepatic mitochondrial oxidative stress, damaged mitochondrial function, disrupted mitochondrial dynamics and activated mitophagy. Importantly, we uncovered that mtROS-activated phosphorylation of heat shock factor 1 (Hsf1) at Ser326 residue mediated MnO2 NPs-induced hepatic lipotoxic disease and mitophagy. Mechanistically, MnO2 NPs-induced lipotoxicity and mitophagy were via mtROS-induced phosphorylation and nucleus translocation of Hsf1 and its DNA binding capacity to plin2/dgat1 and bnip3 promoters, respectively. Overall, our findings uncover novel mechanisms by which mtROS-mediated mitochondrial dysfunction and phosphorylation of Hsf1S326 contribute to MnO2 NPs-induced hepatic lipotoxicity and mitophagy, which provide new insights into the effects of metal oxides nanoparticles on hepatotoxicity in vertebrates.

Toxicity of Metal Oxide Nanoparticles: Looking through the Lens of Toxicogenomics

The impact of solubility on the toxicity of metal oxide nanoparticles (MONPs) requires further exploration to ascertain the impact of the dissolved and particulate species on response. In this study, FE1 mouse lung epithelial cells were exposed for 2-48 h to 4 MONPs of varying solubility: zinc oxide, nickel oxide, aluminum oxide, and titanium dioxide, in addition to microparticle analogues and metal chloride equivalents. Previously published data from FE1 cells exposed for 2-48 h to copper oxide and copper chloride were examined in the context of exposures in the present study. Viability was assessed using Trypan Blue staining and transcriptomic responses via microarray analysis. Results indicate material solubility is not the sole property governing MONP toxicity. Transcriptional signaling through the 'HIF-1α Signaling' pathway describes the response to hypoxia, which also includes genes associated with processes such as oxidative stress and unfolded protein responses and represents a conserved response across all MONPs tested. The number of differentially expressed genes (DEGs) in this pathway correlated with apical toxicity, and a panel of the top ten ranked DEGs was constructed (Hmox1, Hspa1a, Hspa1b, Mmp10, Adm, Serpine1, Slc2a1, Egln1, Rasd1, Hk2), highlighting mechanistic differences among tested MONPs. The HIF-1α pathway is proposed as a biomarker of MONP exposure and toxicity that can help prioritize MONPs for further evaluation and guide specific testing strategies.

Bisphenol A degradation by chlorine dioxide (ClO2) and S(IV)/ClO2 process: Mechanism, degradation pathways and toxicity assessment

Recently, it has been reported that chlorine dioxide (ClO2) and (bi)sulfite/ClO2 showed excellent performance in micropollutant removal from water; however, the degradation mechanisms and application boundaries of the two system have not been identified. In this study, bisphenol A (BPA) was chosen as the target contaminant to give multiple comparisons of ClO2 and S(IV)/ClO2 process regarding the degradation performance of contaminant, generation of reactive species, transformation of products and toxicity variation. Both ClO2 and S(IV)/ClO2 can degrade BPA within 3 min. The BPA degradation mechanism was mainly based on direct oxidation in ClO2 process while it was attributed to radicals (especially SO4·-) generation in S(IV)/ClO2 process. Meanwhile, the effect of pH and coexisting substances (Cl-, Br-, HCO3- and HA) were evaluated. It was found that ClO2 preferred the neutral and alkaline condition and S(IV)/ClO2 preferred the acidic condition for BPA degradation. An unexpected speed-up of BPA degradation was observed in ClO2 process in the presence of Br-, HCO3- and HA. In addition, the intermediate products in BPA degradation were identified. Three exclusive products were found in ClO2 process, in which p-benzoquinone was considered to be the reason of the acute toxicity increase in ClO2 process.

MnO2 nanoparticles and MnSO4 differentially affected hepatic lipid metabolism through miR-92a/acsl3-dependent de novo lipogenesis in yellow catfish Pelteobagrusfulvidraco

With the increasing production and use of MnO2 NPs and MnSO4 in various fields, their discharge into the aquatic environment is inevitable, which poses potential threats to aquatic organisms and humans. However, to date, few studies have been conducted to investigate the potential mechanism of the toxicity of MnO2 NPs, and a comprehensive understanding of the differences between this mechanism and the toxicity mechanism of inorganic Mn (MnSO4) is still lacking. Since lipid metabolism-relevant parameters have been widely recognized as novel biomarkers for risk assessment of environmental contaminants, the present study investigated the differential mechanisms of how MnO2 NPs and MnSO4 affect hepatic lipid metabolism in a freshwater fish yellow catfish. Compared to MnSO4, dietary MnO2 NPs caused liver injury, increased hepatic lipid accumulation and induced lipotoxicity, and up-regulated mRNA expression of de novo lipogenic genes. Moreover, MnO2 NPs downregulated the expression of miR-92a and miR-92b-3p, microRNAs involved in regulation of lipid metabolism, in the liver. Mechanistically, we found that acls3, an acetyl-coenzyme A synthetase, is target gene of miR-92a, and miR-92a-acsl3-dependent de novo lipogenesis contributes to lipid accumulation and lipotoxicity induced by MnO2 NPs. Collectively, these findings provided novel insights into mechanism whereby miRNAs mediate nanoparticles- and inorganic Mn-induced hepatic lipotoxicity and changes of lipid metabolism in vertebrates. Our findings also shed new perspective for ecotoxicity and ecological risk of MnO2 NPs and MnSO4 in aquatic environment.

Mechanistic study of copper oxide, zinc oxide, cadmium oxide, and silver nanoparticles-mediated toxicity on the probiotic Lactobacillus reuteri

The use of metal/metal oxide nanoparticles (NPs) in consumer products has increased dramatically. Accordingly, human exposure to these NPs has increased. Lactobacillus reuteri, a member of the beneficial gut microbiota, is essential for human health. In the present study, the toxic effect of three metal oxides (CuO, ZnO, and CdO) and one metal (Ag) NPs on L. reuteri were investigated in vitro. L. reuteri was susceptible to all the prepared NPs in a dose-dependent manner, visualized as an increase in the zones of inhibition and a significant reduction in the maximum specific growth rates (µmax). The minimal inhibitory concentrations were 5.8, 26, 560, and 560 µg/mL for CdO-, Ag-, ZnO-, and CuO-NPs, respectively, and the respective minimal bactericidal concentrations were 60, 70, 1500, and 1500 µg/mL. Electron microscopic examinations revealed the adsorption of the prepared NPs on L. reuteri cell surface, causing cell wall disruption and morphological changes. These changes were accompanied by significant leakage of cellular protein content by 214%, 191%, 112%, and 101% versus the untreated control when L. reuteri was treated with CdO-, Ag-, CuO-, and ZnO-NPs, respectively. NPs also induced oxidative damage, where the malondialdehyde level was significantly increased, and glutathione content was significantly decreased. Quantifying the DNA damage using comet assay showed that CuONPs had the maximum DNA tail length (8.2 px vs. 2.1 px for the control). While CdONPs showed the maximum percentage of DNA in tail (15.5% vs. 3.1%). This study provides a mechanistic evaluation of the NPs-mediated toxicity to a beneficial microorganism.

New insight into the biocompatibility/toxicity of graphene oxides and their reduced forms on Chlamydomonas reinhardtii

Graphene oxides (GOs) and their reduced forms are often discussed both positively and negatively due to the lack of information about their chemistry and structure. This study utilized GOs with two sheet sizes that were further reduced by two reducing agents (sodium borohydride and hydrazine) to obtain two different degrees of reduction. The synthesized nanomaterials were characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), elemental analysis (EA), Fourier transform infrared (FTIR) spectroscopy, and Raman spectroscopy (RA) to understand their chemistry and structure. The second focus of our investigation included in vitro testing of the biocompatibility/toxicity of these materials on a model organism, the freshwater microalga Chlamydomonas reinhardtii. The effects were studied on the basis of biological endpoints complemented by biomass investigation (FTIR spectroscopy, EA, and atomic absorption spectrometry (AAS)). The results showed that the biocompatibility/toxicity of GOs is dependent on their chemistry and structure and that it is impossible to generalize the toxicity of graphene-based nanomaterials.

Study on myocardial toxicity induced by lead halide perovskites nanoparticles

Lead halide perovskites (LHPs) are outstanding candidates for next-generation optoelectronic materials, with considerable prospects of use and commercial value. However, knowledge about their toxicity is scarce, which may limit their commercialization. Here, for the first time, we studied the cardiotoxicity and molecular mechanisms of representative CsPbBr3 nanoparticles in LHPs. After their intranasal administration to Institute of Cancer Research (ICR) mice, using advanced synchrotron radiation, mass spectrometry, and ultrasound imaging, we revealed that CsPbBr3 nanoparticles can severely affect cardiac systolic function by accumulating in the myocardial tissue. RNA sequencing and Western blotting demonstrated that CsPbBr3 nanoparticles induced excessive oxidative stress in cardiomyocytes, thereby provoking endoplasmic reticulum stress, disturbing calcium homeostasis, and ultimately leading to apoptosis. Our findings highlight the cardiotoxic effects of LHPs and provide crucial toxicological data for the product.

Impact of physico-chemical properties on the toxicological potential of reduced graphene oxide in human bronchial epithelial cells

The increasing use of graphene-based materials (GBM) requires their safety evaluation, especially in occupational settings. The same physico-chemical (PC) properties that confer GBM extraordinary functionalities may affect the potential toxic response. Most toxicity assessments mainly focus on graphene oxide and rarely investigate GBMs varying only by one property. As a novelty, the present study assessed the in vitro cytotoxicity and genotoxicity of six reduced graphene oxides (rGOs) with different PC properties in the human bronchial epithelial 16HBE14o - cell line. Of the six materials, rGO1-rGO4 only differed in the carbon-to-oxygen (C/O) content, whereas rGO5 and rGO6 were characterized by different lateral size and number of layers, respectively, but similar C/O content compared with rGO1. The materials were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, laser diffraction and dynamic light scattering, and Brunauer-Emmett-Teller analysis. Cytotoxicity (Luminescent Cell Viability and WST-8 assays), the induction of reactive oxygen species (ROS; 2',7'-dichlorofluorescin diacetate-based assay), the production of cytokines (enzyme-linked immunosorbent assays) and genotoxicity (comet and micronucleus assays) were evaluated. Furthermore, the internalization of the materials in the cells was confirmed by laser confocal microscopy. No relationships were found between the C/O ratio or the lateral size and any of the rGO-induced biological effects. However, rGO of higher oxygen content showed higher cytotoxic and early ROS-inducing potential, whereas genotoxic effects were observed with the rGO of the lowest density of oxygen groups. On the other hand, a higher number of layers seems to be associated with a decreased potential for inducing cytotoxicity and ROS production.

Transcriptomics-based investigation of manganese dioxide nanoparticle toxicity in rats' choroid plexus

Manganese dioxide nanoparticles (MnO2-NPs) have a wide range of applications in biomedicine. Given this widespread usage, it is worth noting that MnO2-NPs are definitely toxic, especially to the brain. However, the damage caused by MnO2-NPs to the choroid plexus (CP) and to the brain after crossing CP epithelial cells has not been elucidated. Therefore, this study aims to investigate these effects and elucidate potential underlying mechanisms through transcriptomics analysis. To achieve this objective, eighteen SD rats were randomly divided into three groups: the control group (control), low-dose exposure group (low-dose) and high-dose exposure group (high-dose). Animals in the two treated groups were administered with two concentrations of MnO2-NPs (200 mg kg-1 BW and 400 mg kg-1 BW) using a noninvasive intratracheal injection method once a week for three months. Finally, the neural behavior of all the animals was tested using a hot plate tester, open-field test and Y-type electric maze. The morphological characteristics of the CP and hippocampus were observed by H&E stain, and the transcriptome of CP tissues was analysed by transcriptome sequencing. The representative differentially expressed genes were quantified by qRT-PCR. We found that treatment with MnO2-NPs could induce learning capacity and memory faculty decline and destroy the structure of hippocampal and CP cells in rats. High doses of MnO2-NPs had a more obvious destructive capacity. For transcriptomic analysis, we found that there were significant differences in the numbers and types of differential genes in CP between the low- and high-dose groups compared to the control. Through GO terms and KEGG analysis, high-dose MnO2-NPs significantly affected the expression of transporters, ion channel proteins, and ribosomal proteins. There were 17 common differentially expressed genes. Most of them were transporter and binding genes on the cell membrane, and some of them had kinase activity. Three genes, Brinp, Synpr and Crmp1, were selected for qRT-PCR to confirm their expression differences among the three groups. In conclusion, high-dose MnO2-NPs exposure induced abnormal neurobehaviour, impaired memory function, destroyed the structure of the CP and changed its transcriptome in rats. The most significant DEGs in the CP were within the transport system.

The cytotoxicity of nano- and micro-sized graphene oxides on microalgae depends on the characteristics of cell wall and flagella

Cytotoxic effects of emerging contaminants in aquatic environments have been widely studied using diverse microalgal species. However, the role of microalgal characteristics such as presence/absence of cell wall or flagella on cytotoxicity of contaminants was not elucidated yet. In this study, four different Chlamydomonas reinhardtii strains that have different characteristics were used to confirm how these characteristics affect toxicity of contaminants, nano-/micro-sized graphene oxide (GO). The nano-sized GO inhibited the growth of cell wall-deficient strains and reduced the photosynthetic activity. The micro-sized GO inhibited the growth of all strains, but the inhibition efficiency was higher in flagella-deficient strains, indicating that cell wall and flagella have different roles in response to contaminant exposure. The electron microscopy analysis demonstrated that nano-sized GO caused the cell rupture in cell wall-deficient strains. In flagella-deficient strains, the nano- and micro-sized GOs were parallelly attached on the surface of cells, covering the cells. The wrapping of flagella-deficient cells by GO led to the increase of reactive oxygen species (ROS) contents. These results indicate main cytotoxic mechanism of nano-sized GO was the membrane damage of cells, and the presence of cell wall can protect the cells from the attack of nano-sized GO. On the one hand, the presence of flagella might help to avoid the attachment of GO while the cell proliferation and photosynthesis were inhibited in flagella-deficient cells due to the GO wrapping. Overall, given that different microalgal species have different characteristics and these characteristics might affect the cytotoxic effect of the contaminants, it is of great importance to consider the characteristics of test microalgal species when evaluating the cytotoxic mechanism of the nano-/micro-sized pollutants.

Assessing the impact of lime on chromium migration in soil caused by basic chromium sulfate in tannery

Chromium (Cr) pollution is the primary pollution problem of the soil in tannery. However, the effect of tanning chemicals on Cr migration in soil has not been clearly elucidated. Column leaching tests were designed in this study to reveal the transport and transformation of Cr from basic chromium sulfate (BCS) into soil and the effects of lime on Cr migration and transformation. The results showed that BCS was mainly leached out in the state of Cr(VI) after entering the soil, and the Cr concentration in leachate decreased with the increase of the bulking thickness of the BCS. Compared with the soil absent of lime, the concentration of total Cr in the leachate from soil with lime decreased by 8.80-88.1%. The proportions of Cr in the residual fraction were generally increased in the soil with lime, whereas other fractions were decreased. The presence of lime can reduce the migration and toxicity of BCS in soil to a certain extent. The analysis of soil bacterial community showed that the relative abundance of Proteobacteria increased significantly with the exposure to BCS and the Burkholderiaceae was the dominant bacteria family in the BCS contaminated soil. Understanding the mobility of BCS and lime and the bacterial community in BCS contaminated soil is conducive to the risk assessment of the tannery site.

Graphdiyne oxide elicits a minor foreign-body response and generates quantum dots due to fast degradation

Graphdiyne (GDY) is a novel two-dimensional (2D) carbon allotrope that has attracted much attention in materials, physics, chemistry, and microelectronics for its excellent properties. Much effort has been devoted to exploring the biomedical applications of GDY in 2D carbon nanomaterials, especially for smart drugs and gene delivery. However, few studies have focused on the biocompatibility and potential environmental hazards of GDY and its derivatives. In this study, graphdiyne oxide (GDYO) and graphene oxide (GO) were obtained using different oxidation methods. Their cytotoxicity and hemolysis in vitro and biocompatibility in subcutaneous and peritoneal locations in vivo were compared. GDYO had very low biotoxicity in vitro and was moderately biocompatible in the muscle and abdominal cavity in vivo. Highly oxidized products and graphdiyne quantum dots (GDQDs) were observed in peritoneal cells. GDYO had better biocompatibility and its sheet size was easily diminished through oxidative degradation. Therefore, GDYO is a good candidate for use in 2D carbon nanomaterials in biomedicine.

Activation of persulfate by vanadium oxide modified carbon nanotube for 17β-estradiol degradation in soil: Mechanism, application and ecotoxicity assessment

Steroid hormones in the environment have attracted public attention because of their high endocrine-disrupting activity even at rather low exposure level. Excessive hormones in the soil from the pollutant discharge of intensive farming would pose a potential threat to the ecology and the human health. Vanadium oxide modified carbon nanotube (VO_X-CNT) was synthesized and applied as persulfate (PDS) activator to reduce17β-estrogen (17β-E2) in soil. 86.06 % 17β-E2 could be degraded within 12 h. Process of materials exchange during oxidation was interfered by soil, resulting in insufficient degradation of 17β-E2, but the active species involved in 17β-E2 degradation would also be enriched by it. 17β-E2 was adsorbed on the VO_X-CNT surface and directly degraded mainly by the active species generated on the catalyst surface, and ^•OH dominated the degradation of 17β-E2 in VO_X-CNT/PDS system. CO, defective sites and vanadium oxides on the surface of VO_X-CNT contributed to the generation of activate species. Oxidizer dosage, catalyst dosage, water-soil ratio and soil properties would affect the degradation of 17β-E2. The ecotoxicological impact on soil caused by VO_X-CNT/PDS was acceptable, and would be weakened with time. Additionally, a rapid decrease in the concentration of 17β-E2 and the promotion of maize growth were observed with VO_X-CNT/PDS in situ pilot-scale remediation. Those results reveal that VO_X-CNT/PDS is a potential technology to remove excessive steroid hormone from soil around large-scale livestock and poultry farms.

Effect of gamma-ray irradiated reduced graphene oxide (rGO) on environmental health: An in-vitro and in-vivo studies

The unique properties of reduced graphene oxide (rGO) have drawn the attention of scientists worldwide since the last decade and it is explored for a wide range of applications. However, the rapid expansion of rGO use in various products will eventually lead to environenal exposure and rises a safety concern on the environment and humal health risk. Moreover, the utilization of toxic chemicals for the reduction of graphene oxide (GO) into rGO is not environmentally friendly, warranting the exploration of non-toxic approaches. In the present work, rGO was synthesized using a different dose of gamma-ray irradiation and characterized. The in-vitro and in-vivo analysis indicated that the gamma-irradiated rGO induced toxicity depending on its degree of reduction and dosage. In the L929 cells, rGO-30 KGy significantly induced cytotoxicity even at low concentration (1 mg L^-1) by inducing reactive oxygen species (ROS), lactate dehydrogenase (LDH) enzyme production, nuclear fragmentation and apoptosis. The change in morphology of the cells like membrane blebbing and cell rounding was also observed via FESEM. In the in-vivo model Caenorhabditis elegans, rGO-30 KGy significantly affected the functioning of primary and secondary targeted organs and also negatively influenced the nuclear accumulation of transcription factors (DAF-16/FOXO and SKN-1/Nrf2), neuronal health, and antioxidant defense mechanism of the nematodes. The real-time PCR analysis showed significant up-regulation (ced-3, ced-4, cep-1, egl-1, and hus-1) and down-regulation (ced-9) of the gene involved in germ-line and DNA damage-induced apoptosis. The detailed toxicity mechanism of gamma irradiated rGO has been elucidated. This work highlights the toxicity of rGO prepared by gamma-ray radiation and paves way for understating the toxicity mechanism.

Comparative pulmonary toxicity assessment of tungsten trioxide and tungsten trioxide hydrate nanoparticles

Tungsten trioxide (WO₃)-based nanoparticles (NPs) are gaining popularity because of their exciting potential for photocatalytic applications; however, the toxic potential of WO₃-based NPs remains a concern. In this study, we evaluated the toxic risk of WO₃ NPs and hydrated WO₃ NPs (WO₃·H₂O NPs) using lung cells and explored the underlying mechanism. WO₃ NPs and WO₃·H₂O NPs significantly decreased the number of viable cells (59.5 %-85.8 % of control) and promoted apoptosis in human alveolar basal epithelial A549 cells after a 24-h exposure. Both WO₃ NPs and WO₃·H₂O NPs reduced the expression of heme oxygenase-1 (0.15-0.33 folds of control) and superoxide dismutase 2 (0.31-0.66 folds of control) and increased reactive oxygen species production (1.4-2.6 folds of control) and 8-hydroxy-2'-deoxyguanosine accumulation (1.22-1.43 folds of control). The results showed that WO₃ NPs have higher cytotoxicity and oxidative potential than WO₃·H₂O NPs. In addition, the WO₃ NP cellular uptake rate was significantly higher than the WO₃·H₂O NPs uptake rate in pulmonary cells. The greater extent of oxidative adverse effects induced by WO₃-based NPs appears to be related to the enhanced particle uptake. WO₃ NPs and WO₃·H₂O NPs exposure led to the secretion of inflammatory factor interleukin 6 (1.63-3.42 folds of control). Decreases in serpin family A member 1 gene expression (0.28-0.58 folds of control) and increases in the oxidation of neutrophil elastase inhibitor (1.34-1.62 folds of control) in pulmonary cells also suggest that exposure to WO₃ NPs and WO₃·H₂O NPs raises the risk of developing chronic obstructive pulmonary disease. Taken together, our findings indicate that the toxic risk of WO₃ NPs and WO₃·H₂O NPs must be considered when manufacturing and applying WO₃-based NPs.

Modulation mechanism of phytotoxicity on Ipomoea aquatica Forssk. by surface coating-modified copper oxide nanoparticles and its health risk assessment

To evaluate the influence of surface coatings on nano-fertilizers uptake and their phytotoxicity to crops and its health risk to Chinese adults, trisodium citrate (TC) and polyethylene glycol (PEG) coatings were prepared on the surface of copper oxide nanoparticles (CuO NPs), respectively, with 100 and 500 mg/L of bare CuO NPs, TC-CuO NPs, and PEG-CuO NPs were exposed to soil-grown Ipomoea aquatica Forssk. Combined bio-transmission electron microscopy and micro-CT observed cellular migration of coated CuO NPs in symplastic and apoplastic pathways, as well as nanoparticles transported through vascular tissues to the above-ground parts. Since TC-CuO NPs had less inhibition on vascular phylogeny of I. aquatica roots which was determined by RT-qPCR, their migration in plants was more efficient, thus exhibiting greater phytotoxicity to shoots. Meanwhile, coatings significantly reduced the phytotoxicity of CuO NPs by stimulating plant antioxidant defense. The risk of CuO nano-fertilizers on human dietary safety was evaluated, the HQ > 1 in the 500 mg/L CuO NPs treatment indicated a potential health risk to Chinese adults, which was reduced by the coatings. This work explored for the first time the mechanism of coating effects on nanoparticles migration efficiency and phytotoxicity at the molecular level and demonstrated that the migration of nanoparticles between tissues could have an impact on phytotoxicity. It implied that coating can be tailored to target nanoparticles to specific regions of the plant. In addition, this study highlights the potential health risks associated with the consumption of I. aquatica fertilized with CuO NPs and provides valuable insights into the environmental applications of nano-fertilizers.

Combined effects of copper oxide and nickel oxide coated chitosan nanoparticles adsorbed to styrofoam resin beads on hydrothermal vent bacteria

Microplastics are potential carriers of harmful contaminants but their combined effects are largely unknown. It needs intensive monitoring in order to achieve a better understanding of metal-oxide nanoparticles and their dispersion via microplastics such as styrofoam in the aquatic environment. In the present study, an effort was made to provide a preferable perception about the toxic effects of engineered nanoparticles (NPs), namely, copper oxide (CuO NPs), nickel oxide (NiO NPs), copper oxide/chitosan (CuO/CS NPs) and nickel oxide/chitosan (NiO/CS NPs). Characterizations of synthesized NPs included their morphology (SEM and EDX), functional groups (FT-IR) and crystallinity (XRD). Their combined toxic effect after adsorption to styrofoam (SF) was monitored using the hydrothermal vent bacterium Jeotgalicoccus huakuii as a model. This was done by determining MIC (minimum inhibitory concentration) through a resazurin assay measuring ELISA, growth, biofilm inhibition and making a live and dead assay. Results revealed that at high concentrations (60 mg/10 mL) of CuO, CuO/CS NPs and 60 mg of SF adsorbed CuO and CuO/CS NPs inhibited the growth of J. huakuii. However, NPs rather than SF inhibited the growth of bacteria. The toxicity of NPs adsorbed on plain SF was found to be less compared to NPs alone. This study revealed new dimensions regarding the positive impacts of SF at low concentrations. Synthesized NPs applied separately were found to affect the growth of bacteria substantially more than if coated to SF resin beads.

Electrochemically activated peroxymonosulfate with mixed metal oxide electrodes for sulfadiazine degradation: Mechanism, DFT study and toxicity evaluation

Electrochemically activated peroxymonosulfate with mixed metal oxide electrodes (EA-PMS-MMO/MMO) is an emerging advanced oxidation process. It performed well on the degradation of sulfadiazine (SDZ), whose removal rate reached 81.13% within 30 min. Both the MMO anode and cathode played an irreplaceable role in PMS activation. HO^•, SO₄^•-, O₂^•- and ¹O₂ were confirmed to be the major reactive species in the system, among which ¹O₂ was the most abundant. The generation mechanism of the reactive species and the overall mechanism of the system were proposed. Four degradation pathways of SDZ were speculated based on density functional theory. The acute and chronic toxicity of SDZ and its degradation intermediates was evaluated by the quantitative structure-activity relationship method, and the overall toxicity was significantly reduced after the degradation by EA-PMS-MMO/MMO. The results show that EA-PMS-MMO/MMO affords a reliable technology for the degradation of organic contaminants and has promising potential for application.

Nano-QSAR modeling for predicting the cytotoxicity of metallic and metal oxide nanoparticles: A review

Given the rapid development of nanotechnology, it is crucial to understand the effects of nanoparticles on living organisms. However, it is laborious to perform toxicological tests on a case-by-case basis. Quantitative structure-activity relationship (QSAR) is an effective computational technique because it saves time, costs, and animal sacrifice. Therefore, this review presents general procedures for the construction and application of nano-QSAR models of metal-based and metal-oxide nanoparticles (MBNPs and MONPs). We also provide an overview of available databases and common algorithms. The molecular descriptors and their roles in the toxicological interpretation of MBNPs and MONPs are systematically reviewed and the future of nano-QSAR is discussed. Finally, we address the growing demand for novel nano-specific descriptors, new computational strategies to address the data shortage, in situ data for regulatory concerns, a better understanding of the physicochemical properties of NPs with bioactivity, and, most importantly, the design of nano-QSAR for real-life environmental predictions rather than laboratory simulations.

Phytotoxicity of VO2 nanoparticles with different sizes to pea seedlings

Vanadium dioxide nanoparticles (VO2 NPs) have been massively produced due to their excellent metal-insulator transition characteristics for various applications. Pilot studies indicated the toxicity of VO2 NPs to bacteria and mammalian cells, but the environmental hazards of VO2 NPs to plants have been unrevealed to date. In this study, we reported the inhibitive effects of VO2 NPs to the growth and photosynthesis of pea seedlings. Laboratory synthesized monoclinic VO2 NPs (N-VO2), commercial nanosized VO2 NPs (S-VO2), and commercial microsized VO2 particles (M-VO2) were carefully characterized for environmental toxicity evaluations. VO2 particles were supplemented to culture medium for seed germination and seedling growth. All three VO2 samples did not affect the germination rates of pee seeds, while serious growth inhibition of pea seedlings was observed at 10 mg/L for S-VO2 and N-VO2, and 100 mg/L for M-VO2. VO2 particles had no impact on the chlorophyll contents, but the photosynthesis of leaf was significantly decreased following the consequence of N-VO2 > S-VO2 > M-VO2. The inhibition of photosynthesis was attributed to the damage of acceptor side of photosystem II by VO2 particles at high concentrations. Abundant bioaccumulations of vanadium in roots aroused oxidative damage and changed the root structure. Our results collectively indicated that the phytotoxicity of VO2 NPs was related to the concentration, size and crystalline degree.

Double Z-Scheme ZnCo2O4/MnO2/FeS2 photocatalyst with enhanced photodegradation of organic compound: Insights into mechanisms, kinetics, pathway and toxicity studies

The present work highlights the preparation of double Z-scheme ZnCo2O4/MnO2/FeS2 nanocomposite (NCs) and investigated its photocatalytic activity against methyl orange (MO) dye degradation under visible light. An array of techniques was carried out to characterize the nanoparticles (NPs) in order to evaluate their morphological, structural, optical, and photocatalytic properties using FE-SEM, TEM, XRD, N2 adsorption and desorption studies, PL, UV-visible spectrophotometer, XPS, Raman, and UV-vis DRS analysis. The degradation efficiency of NCs was tested along with different parameter studies such as different pH, NCs concentration, dye concentration, reusability and structural stability. The NCs exhibited complete photodegradation of MO dye under visible light within 80 min at pH 4. The structural and compositional stability of the prepared NCs over 6 consecutive cycles was tested via XRD and XPS analysis. The results of active species trapping experiments showed that O2-• and OH• are responsible for the degradation of MO dye. The TOC analysis showed 95% of mineralization by the prepared NCs. The MO dye degradation pathway was determined using GC-MS/MS analysis and drafted all the intermediates involved. End product toxicity via seed germination and intermediate toxicity study using ECOSAR software results in less toxicity of end product compared to parent compound. Finally, the genotoxicity of the prepared NCs was evaluated using Allium cepa and showed its no causes of cytotoxicity & genotoxicity by the prepared NCs. ZnCo2O4/MnO2/FeS2 NCs exhibited its high photocatalytic activity and the toxicity studies confirms that there is no cause of any environmental impact.

Combined exposure to nanoplastics and metal oxide nanoparticles inhibits efflux pumps and causes oxidative stress in zebrafish embryos

The ubiquity of microplastic/nanoplastics (MP/NPs) provides an opportunity for their interaction with other widely spread environmental contaminants. MP/NP and nanoparticles share a similar transport route from sources, production, and disposal. Metal oxide nanoparticles (nMOx) have varied industrial applications, and limited knowledge is available on their interaction with MP/NPs. The present study investigated the effect of NPs (1 mg/L) on the efflux of two nMOx, aluminium oxide nanoparticles (nAl₂O₃, 1 mg/L) and cerium oxide nanoparticles (nCeO₂, 1 mg/L), and their combined toxicity to zebrafish embryos. The results illustrated increased accumulation of aluminium and cerium in the combined exposure group compared to the nMOx alone treatment. The presence of NPs exacerbated the oxidative stress caused by nAl₂O₃ and nCeO₂, as evidenced by an increase in the concentration of reactive oxygen species (ROS), alteration of antioxidants, and lipid peroxidation. The integrated biomarker response (IBRv2) values showed the induction of an antioxidative response in NP + nAl₂O₃, whereas a decline in IBRv2 values was observed in NP + nCeO₂. Our results indicate that NPs aggravated the accumulation of nMOx and their toxicity. The present work highlights that more attention should be paid to the discharge of these contaminants into the natural environment.

Concentration- and time-dependence toxicity of graphene oxide (GO) and reduced graphene oxide (rGO) nanosheets upon zebrafish liver cell line

Graphene oxide (GO) and reduced graphene oxide (rGO) are carbon-based nanomaterials that have a wide range of applicability. Therefore, it is expected that their residual traces reach the aquatic environment, accumulate, and interact with its different compartments and the biota living in them. The concentration- and time-dependency response to GO and rGO in aquatic organisms are still poorly known. In the present study, the effects of GO and rGO on zebrafish hepatocytes were investigated using in vitro assays performed with established liver cell lines from zebrafish (ZFL). GO and rGO nanosheets were applied on ZFL cells at a concentration range of 1-100 µg mL^-1 for 24 and 72 h. The internalization of GO and rGO nanosheets, reactive oxygen species (ROS) production, cell viability, and cell death were evaluated. The internalization of GO increased as the concentrations of GO increased. The rGO nanosheets were smaller than GO nanosheets, and their hydrophobic characteristic favors their interaction with the cell membrane. However, the rGO nanosheets were not observed in the uptake assay. Exposure for 72 h was found to cause harmful effects in ZFL cells, causing higher ROS production in cells exposed to rGO and stopping cell replication. Nevertheless, GO did not stop cell replication, but exposed cells had higher levels of apoptosis and necrosis. After 72 h, both GO and rGO were toxic, but with different mechanisms of toxicity.

In vitro and in silico study of mixtures cytotoxicity of metal oxide nanoparticles to Escherichia coli: a mechanistic approach

Metal oxide nanoparticles (MONPs) are commonly found in the aquatic and terrestrial systems as chemical mixtures. Assessment of cytotoxicity associated with single and combination of MONPs can truly identify the concerned environmental risk. Thus, using Escherichia coli as a test model, in vitro cytotoxicity of 6 single MONPs, 15 binary and 20 tertiary mixtures with equitoxic ratios was evaluated following standard bioassay protocols. Assessment of oxidative stress suggested that the production of reactive oxygen species (ROS) was negligible, and the release of metal zinc ions played an important role in the toxicity of MONP mixtures. From our experimental data points, seven quantitative structure-activity relationships (QSARs) models were developed to model the cytotoxicity of these MONPs, based on our created periodic table-based descriptors and experimentally analyzed Zeta-potential. Two strategic approaches i.e. pharmacological and mathematical hypotheses were considered to identify the mixture descriptors pool for modeling purposes. The stringent validation criteria suggested that the model (Model M4) developed with mixture descriptors generated by square-root mole contribution outperformed the other six models considering validation criteria. While considering the pharmacological approach, the 'independent action' generated descriptor pool offered the best model (Model M2), which firmly confirmed that each MONP in the mixture acts through 'independent action' to induce cytotoxicity to E. coli instead of fostering an additive, antagonistic or synergistic effect among MONPs. The total metal electronegativity in a specific metal oxide relative to the number of oxygen atoms and metal valence was associated with a positive contribution to cytotoxicity. At the same time, the core count, which gives a measure of molecular bulk and Zeta potential, had a negative contribution to cytotoxicity.

Use of dissociation degree in lysosomes to predict metal oxide nanoparticle toxicity in immune cells: Machine learning boosts nano-safety assessment

Potential immune responses resulting from exposure to metal oxide nanoparticles (MeONPs) have been the subject of intensive discussion in the last decade. Despite the extensive use of MeONPs in several applications, their toxic effects on immune cells have rarely been predicted in silico because of the complexity of immune responses and the complicated properties of MeONPs. In the present study, machine learning (ML) methods coupled with high-throughput in vitro bioassays were used to develop models for predicting the toxicity of MeONPs in immune cells. An ML model with a high prediction accuracy (97% and 96% in the training and test sets, respectively) was constructed by resolving the class imbalance problem in training and applying an ensembled algorithm. Further, to verify the model, MeONPs outside the scope of the datasets were selected to examine their cytotoxicity experimentally. The model was validated against independent MeONPs, with an accuracy of 91%. ML methods coupled with intracellular imaging revealed that the toxic ions released in the lysosome were an important determinant of toxicity in immune cells. Furthermore, ζ-potential, electronegativity, and size are crucial factors for predicting nanotoxicity. We believe the established modeling framework will provide useful insights for designing and applying safe nanoparticles and facilitating decision-making for environmental and health protection.

The Role of Extracellular Polymeric Substances in the Toxicity Response of Anaerobic Granule Sludge to Different Metal Oxide Nanoparticles

Wastewater treatment plants (WWTP) are regarded as the last barriers for the release of incompletely separated and recycled nanoparticles (NPs) into the environment. Despite the importance and ubiquity of microbial extracellular polymeric substances (EPSs) in the complex wastewater matrix, the interaction between NPs and EPSs of anaerobic microflora involved in wastewater treatment and the resultant impact on the biomass metabolomics are unclear. Thus, the impacts of different metal oxide (TiO₂, ZnO, and CuO) NPs on functional bacteria in anaerobic granular sludge (AGS) and the possible toxicity mechanisms were investigated. In particular, the binding quality, enhanced resistance mechanism, and chemical fractional contribution of EPSs from AGS against the nanotoxicity of different NPs was assessed. The results showed that CuO NPs caused the most severe inhibition towards acetoclastic and hydrogenotrophic methanogens, followed by ZnO NPs, whereas TiO₂ NPs caused no inhibition to methanogenesis. Excessive EPS production, especially the protein-like substances, was an effective strategy for reducing certain NPs’ toxicity by immobilizing NPs away from AGS cells, whereas the metabolism restriction on inner microorganisms of AGS induced by CuO NPs can deteriorate the protective role of EPS, indicating that the roles of EPS may not be amenable to generalizations. Further investigations with lactate dehydrogenase (LDH) and reactive oxygen species (ROS) assays indicated that there are greatly essential differences between the toxicity mechanisms of metal NPs to AGS, which varied depending on the NPs’ type and dosage. In addition, dynamic changes in the responses of EPS content to different NPs can result in a significant shift in methanogenic and acidogenic microbial communities. Thus, the production and composition of EPSs will be a key factor in determining the fate and potential effect of NPs in the complex biological matrix. In conclusion, this study broadens the understanding of the inhibition mechanisms of metal oxide NPs on the AGS process, and the influence of EPSs on the fate, behavior, and toxicity of NPs.

In vitro toxic interaction of arsenic and hyperglycemia in mitochondria: an important implication of increased vulnerability in pre-diabetics

Environmental pollutants and lifestyle both contribute to the rapidly increasing prevalence of type 2 diabetes mellitus (T2DM) worldwide. Evidence suggests that exposure to environmental contaminants such as arsenic is associated with impaired glucose metabolism and insulin signaling. In the present study, isolated rat liver mitochondria (1 mg/ml) were co-exposed to low concentration of arsenic trioxide (ATO) ( IC₂₅ = 40 µM) and hyperglycemic condition (20, 40, 80, 160 mM glucose or 20, 40, 80, 160 mM pyruvate (PYR)). Mitochondrial dehydrogenase activity (complex II), glutathione content (GSH), reactive oxygen species (ROS), lipid peroxidation, mitochondrial membrane potential (ΔΨ), and mitochondrial swelling were then evaluated in the presence of ATO 40 µM and PYR 40 mM. Unexpectedly, glucose alone (20, 40, 80, 160 mM) had no toxic effect on mitochondria, even at very high concentrations and even when combined with ATO. Interestingly, PYR at low concentrations (≤ 10 mM) has a protective effect on mitochondria, but at higher concentrations (≥ 40 mM) with ATO, it decreased the complex II activity and increased mitochondrial ROS production, lipid peroxidation, GSH depletion, mitochondrial membrane damage, and swelling (p < 0.05). In conclusion, PYR but not glucose increased ATO mitochondrial toxicity even at low concentrations. These results suggest that pre-diabetics with non-clinical hyperglycemia, who are inevitably exposed to low concentrations of arsenic through food and water, may develop mitochondrial dysfunction that accelerates their progression to diabetes over time.

Rare-earth metal oxide nanoparticles decouple the linkage between soil bacterial community structure and function by selectively influencing potential keystone taxa

Excessive production and application of rare-earth metal oxide nanoparticles warrants assessment of their environmental risks. Little is known about the impact of these nanoparticles on soil bacterial communities. We quantified the effects of nano-Gd₂O₃ and nano-La₂O₃, at the different concentrations and exposure regimes, on soil bacterial community structure and function as well as the structure-function relationship. Further, we constructed and analyzed a co-occurrence network to identify and characterize potential keystone taxa that were related to the enzyme activities and responded to the increasing concentrations of nanoparticles. Both nano-Gd₂O₃ and nano-La₂O₃ significantly altered the bacterial community structure and function in a concentration-dependent manner; however, these negative effects were observed on day 1 or day 7 but not on day 60, indicating that these effects were transient and the bacterial communities can mitigate the effect of these nanoparticles over time. Interestingly, the nanoparticle exposure decoupled the relationship between the structure and function of the soil bacterial communities. The decoupling was due to changes in the composition and relative abundances of potential keystone taxa related to bacterial community functions. Altogether, we provide insights into the interactions between the rare-earth metal oxide nanoparticles and soil bacterial communities. Our results facilitate the environmental risk assessment and safe usage of rare-earth metal oxide nanoparticles.

Potential lead toxicity and leakage issues on lead halide perovskite photovoltaics

Recently, lead halide perovskite solar cells have become a promising next-generation photovoltaics candidate for large-scale application to realize low-cost renewable electricity generation. Although perovskite solar cells have tremendous advantages such as high photovoltaic performance, low cost and facile solution-based fabrication, the issues involving lead could be one of the main obstacles for its commercialization and large-scale applications. Lead has been widely used in photovoltaics industry, yielding its environmental and health issues of vital importance because of the widespread application of photovoltaics. When the solar cell panels especially perovskite solar cells are damaged, lead would possibly leak into the surrounding environment, causing air, soil and groundwater contamination. Therefore, lots of research efforts have been put into evaluating the lead toxicity and potential leakage issues, as well as studying the encapsulation of lead to deal with leakage issue during fire hazard and precipitation in photovoltaics. In this review, we summarize the latest progress on investigating the lead safety issue on photovoltaics, especially lead halide perovskite solar cells, and the corresponding solutions. We also outlook the future development towards solving the lead safety issues from different aspects.

Brønsted-acid sites promoted degradation of phthalate esters over MnO2: Mineralization enhancement and aquatic toxicity assessment

Advanced oxidation processes (AOPs) are important technologies for aqueous organics removal. Despite organic pollutants can be degraded via AOPs generally, high mineralization of them is hard to achieve. Herein, we synthesized a manganese oxide nanomaterial (H2-OMS-2) with abundant Brønsted-acid sites via ion-exchange of cryptomelane-type MnO₂ (OMS-2), and tested its catalytic performance for the degradation of phthalate esters via peroxymonosulfate (PMS) activation. About 99% of dimethyl phthalate (DMP) at a concentration of 20 mg/L could be degraded within 90 min and 82% of it could be mineralized within 180 min over 0.6 g/L of catalyst and 1.8 g/L of PMS. The catalyst could activate PMS to generate SO₄^-˙ and ·OH as the dominant reactive oxygen species to reach complete degradation of DMP. Especially, the higher TOC removal rate was obtained due to the rich Brønsted-acid sites and surface oxygen vacancies on the catalyst. Kinetics and mechanism study showed that Mn^II/Mn^III might work as the active sites during the catalytic process with a lower reaction energy barrier of 55.61 kJ/mol. Furthermore, the catalyst could be reused for many times through the regeneration of the catalytic ability. The degradation and TOC removal efficiencies were still above 98% and 65% after seven consecutive cycles, respectively. Finally, H2-OMS-2-catalyzed AOPs significantly reduced the organismal developmental toxicity of the DMP wastewater through the investigation of zebrafish model system. The present work, for the first time, provides an idea for promoting the oxidative degradation and mineralization efficiencies of aqueous organic pollutants by surface acid-modification on the catalysts.

Effects of Metal Oxide Nanoparticles in Zebrafish

Metal oxide nanoparticles (MO NPs) are increasingly employed in many fields with a wide range of applications from industries to drug delivery. Due to their semiconducting properties, metal oxide nanoparticles are commonly used in the manufacturing of several commercial products available in the market, including cosmetics, food additives, textile, paint, and antibacterial ointments. The use of metallic oxide nanoparticles for medical and cosmetic purposes leads to unavoidable human exposure, requiring a proper knowledge of their potentially harmful effects. This review offers a comprehensive overview of the possible toxicity of metallic oxide nanoparticles in zebrafish during both adulthood and growth stages, with an emphasis on the role of oxidative stress.

Graphene oxide toxicity in W1118 flies

The risk of graphene oxide (GO) exposure to various species has been greatly amplified in recent years due to its booming production and applications in various fields. However, a deep understanding of the GO biosafety lags its wide applications. Herein, we used W¹¹¹⁸ flies as a model organism to study GO toxicity at relatively low concentrations. We found that GO exposure led to remarkable weight loss, delayed development, retarded motion, and shortened lifespan of these flies. On the other hand, the GO influence on their sex ratio and the total number of pupae and adults were insignificant. The toxicological effect of GO was shown to be related to its serious compromise of the nutrient absorption in flies due to the severe damages in midguts. These damages were then attributed to the excessive accumulation of reactive oxygen species (ROS), which triggers the oxidative stress. These findings reveal the underlying mechanisms of GO biotoxicities in fruit flies, which might provide a useful reference to assess the risks of these newly invented nanomaterials likely never encountered by various species before.

Pulmonary toxicity, genotoxicity, and carcinogenicity evaluation of molybdenum, lithium, and tungsten: A review

Molybdenum, lithium, and tungsten are constituents of many products, and exposure to these elements potentially occurs at work. Therefore it is important to determine at what levels they are toxic, and thus we set out to review their pulmonary toxicity, genotoxicity, and carcinogenicity. After pulmonary exposure, molybdenum and tungsten are increased in multiple tissues; data on the distribution of lithium are limited. Excretion of all three elements is both via faeces and urine. Molybdenum trioxide exerted pulmonary toxicity in a 2-year inhalation study in rats and mice with a lowest-observed-adverse-effect concentration (LOAEC) of 6.6 mg Mo/m³. Lithium chloride had a LOAEC of 1.9 mg Li/m³ after subacute inhalation in rabbits. Tungsten oxide nanoparticles resulted in a no-observed-adverse-effect concentration (NOAEC) of 5 mg/m³ after inhalation in hamsters. In another study, tungsten blue oxide had a LOAEC of 63 mg W/m³ in rats. Concerning genotoxicity, for molybdenum, the in vivo genotoxicity after inhalation remains unknown; however, there was some evidence of carcinogenicity of molybdenum trioxide. The data on the genotoxicity of lithium are equivocal, and one carcinogenicity study was negative. Tungsten seems to have a genotoxic potential, but the data on carcinogenicity are equivocal. In conclusion, for all three elements, dose descriptors for inhalation toxicity were identified, and the potential for genotoxicity and carcinogenicity was assessed.

Influence of natural organic matter on the transformation of metal and metal oxide nanoparticles and their ecotoxic potency in vitro

Increased use and production of engineered nanoparticles (NPs) lead to an elevated risk of their diffuse dispersion into the aquatic environment and increased concern on unknown effects induced by their release into the aquatic ecosystem. An improved understanding of the environmental transformation processes of NPs of various surface characteristics is hence imperative for risk assessment and management. This study presents results on effects of natural organic matter (NOM) on the environmental transformation and dissolution of metal and metal oxide NPs of different surface and solubility properties in synthetic freshwater (FW) with and without NOM. Adsorption of NOM was evident on most of the studied NPs, except Sb and Sb₂O₃, which resulted in the formation of negatively charged colloids of higher stability and smaller size distribution compared with the same NPs in FW only. The dissolution rate of the NPs in the presence of NOM correlated with the strength of interactions between the carboxylate group of NOM and the particle surface, and resulted in either no (Mn, Sb, ZnO NPs), increased (Co, Sn NPs) and decreased (Ni, NiO, Sb₂O₃, Y₂O₃ NPs) levels of dissolution. One type of metal NP from each group (Mn, Ni, Sn) were investigated to assess whether observed differences in adsorption of NOM and dissolution would influence their ecotoxic potency. The results showed Mn, Ni, and Sn NPs to generate intracellular reactive oxygen species (ROS) in a time and dose-dependent manner. The extent of ROS generation in FW was similar for both Mn and Ni NPs but higher for Sn NPs. These findings are possibly related to interactions and infiltration of the NPs with the cells, which lead to redox imbalances which could induce oxidative stress and cell damage. At the same time, the presence of NOM generally reduced the intracellular ROS generation by 20-40% for the investigated NPs and also reduced cytotoxicity of Sn NPs, which can be attributed to the stronger interaction of carboxylate groups of NOM with the surface of the NPs.

Tracing the toxic ions of an endodontic tricalcium silicate-based sealer in local tissues and body organs

BACKGROUND

This study aimed to track the toxic ions released by MTA Fillapex, BioRoot RCS, and an experimental tricalcium silicate-based sealer (CEO) into local and distant tissues as well as to investigate their potential adverse effects. In addition, the chemical constituents of the sealers were also evaluated. The main components of the dry powders, pastes, and mixed sealers were characterized.

MATERIAL AND METHODS

Dry powder and sealer discs were each set for 72 h and their main components were characterized by energy dispersive X-ray spectroscopy. Polyethylene tubes filled with sealers were used to measure silicon and calcium ions. Polyethylene tubes filled with sealers or empty tubes were implanted into the dorsal connective tissue of Wistar rats. On days 7, 15, 30, and 45, the animals were euthanized and their brains, livers, kidneys, and subcutaneous tissues were removed and processed to determine the concentrations of chromium, cobalt, copper, lead, iron, magnesium and nickel using an inductively coupled plasma optical emission spectrometer.

RESULTS

The main compounds in all sealers were carbon, oxygen, silicon, and calcium. MTA Fillapex release more Si while highest levels of Si were found in presence of BioRoot. The release of Si and Ca ions promoted by MTA Fillapex raise by time. No traces of cobalt, chromium, or magnesium were detected in any tissue. Irrespective of the sealer, no traces of copper and lead were found in the subcutaneous tissue; however, they were observed in the organs. The highest concentration of iron was identified in the liver. All sealers exhibited similar nickel traces in the brain, kidney, and liver except for MTA Fillapex, which demonstrated levels higher than CEO in the subcutaneous tissue on day 7. Tracing nickel ions over time revealed that lowest concentrations were found in subcutaneous tissue.

CONCLUSION

Taken together, our data demonstrate that CEOs have chemical compositions similar to those of other commercial sealers. Furthermore, none of them exhibited a threat to systemic health. Moreover, the minimal amounts of iron and nickel detected were not related to the sealers.

Comparative study of the effects of biocides and metal oxide nanoparticles on microbial community structure in a stream impacted by hydraulic fracturing

Our study goal was to investigate the impact of biocides and nanoparticles (NPs) on the microbial diversity in a hydraulic fracturing impacted stream. Biocides and NPs are known for their antimicrobial properties and controlling microbial growth. Previous work has shown that biocides can alter the microbial community composition of stream water and may select for biocide-resistant bacteria. Additional studies have shown that nanoparticles can also alter microbial community composition. However, previous work has often focused on the response to a single compound. Here we provide a more thorough analysis of the microbial community response to three different biocides and three different nanoparticles. A microcosm-based study was undertaken that exposed stream microbial communities to either biocides or NPs. Our results showed a decrease in bacterial abundance with different types of nanoparticles, but an increase in microbial abundance in biocide-amended treatments. The microbial community composition (MCC) was distinct from the controls in all biocide and NP treatments, which resulted in differentially enriched taxa in the treatments compared to the controls. Our results indicate that NPs slightly altered the MCC compared to the biocide-treated microcosms. After 14 days, the MCC in the nanoparticle-treated conditions was similar to the MCC in the control. Conversely, the MCC in the biocide-treated microcosms was distinct from the controls at day 14 and distinct from all conditions at day 0. This finding may point to the use of NPs as an alternative to biocides in some settings.

How to control fluorescent labeling of metal oxide nanoparticles for artefact-free live cell microscopy

Nanotechnologies hold great promise for various applications. To predict and guarantee the safety of novel nanomaterials, it is essential to understand their mechanism of action in an organism, causally connecting adverse outcomes with early molecular events. This is best investigated using noninvasive advanced optical methods, such as high-resolution live-cell fluorescence microscopy, which require stable labeling of nanoparticles with fluorescent dyes. However, as shown here, when the labeling is performed inadequately, unbound fluorescent dyes and inadvertently altered chemical and physical properties of the nanoparticles can result in experimental artefacts and erroneous conclusions. To prevent such unintentional errors, we introduce a tested minimal combination of experimental methods to enable artefact-free fluorescent labeling of metal-oxide nanoparticles-the largest subpopulation of nanoparticles by industrial production and applications-and demonstrate its application in the case of TiO2 nanotubes. We (1) characterize potential changes of the nanoparticles' surface charge and morphology that might occur during labeling by using zeta potential measurements and transmission electron microscopy, respectively, and (2) assess stable binding of the fluorescent dye to the nanoparticles with either fluorescence intensity measurements or fluorescence correlation spectroscopy, which ensures correct nanoparticle localization. Together, these steps warrant the reliability and reproducibility of advanced optical tracking, which is necessary to explore nanomaterials' mechanism of action and will foster widespread and safe use of new nanomaterials.

Mechanistic actions and contributing factors affecting the antibacterial property and cytotoxicity of graphene oxide

Recent advances in the field of nanotechnology contributed to the increasing use of nanomaterials in the engineering, health and biological sectors. Graphene oxide (GO) has great potentials as it could be fine-tuned to be adapted into various applications, especially in the electrical, electronic, industrial and clinical fields. One of the important applications of GO is its use as an antibacterial material due to its promising activity against a broad range of bacteria. However, our understanding of the mechanism of action of GO towards bacteria is still lacking and is often less described. Therefore, a comprehensive overview of bactericidal mechanistic actions of GO and the roles of physicochemical factors including size, aggregation, functionalization and adsorption behavior contributing to its antibacterial activities are described in this review. As the use of GO is expected to increase exponentially in the health sector, the cytotoxicity of GO among the cell lines is also discussed. Thus, this review emphasizes the physicochemical characteristics of GO that can be tailored for optimal antibacterial properties that is of importance to the health industry.

Arsenic trioxide induces expression of BCL-2 expression via NF-κB and p38 MAPK signaling pathways in BEAS-2B cells during apoptosis

Inorganic arsenic compounds are environmental toxicants that are widely distributed in air, water, and food. B-cell lymphoma 2 (BCL-2) is an oncogene having anti-apoptotic function. In this study, we clarify that BCL-2, as a pro-apoptotic factor, participates in As₂O₃-induced apoptosis in BEAS-2B cells. Specifically, As₂O₃ stimulated the expression of BCL-2 mRNA and protein in a dose-dependent manner which was highly accumulated in the nucleus of BEAS-2B cell together with chromatin condensation and DNA fragmentation during apoptosis. Mechanistically, the process described above is mediated through the NF-κB and p38 MAPK signaling pathways, which can be abated by corresponding inhibitors, such as BAY11-7082 and SB203580, respectively. Additionally, BAY11-7082, actinomycin D, and cycloheximide have inhibitory effects on As₂O₃-induced expression of BCL-2 mRNA and protein, and restore the cell viability of BEAS-2B cells. Suppression of BCL-2 protein activation by ABT-199 also restored viability of BEAS-2B cell in As₂O₃-induced apoptosis. Furthermore, As₂O₃ increased the level of BCL-2 phosphorylation. These results suggest that in BEAS-2B cells, As₂O₃-induced apoptosis is mainly dominated by BCL-2 upregulation, nuclear localization and phosphorylation. The study presented here provides a novel insight into the molecular mechanism of BCL-2-induced apoptosis.