Metal-Based Nanotoxicity and Detoxification Pathways in Higher Plants

The potential risks from metal-based nanoparticles (NPs) in the environment have increased with the rapidly rising demand for and use of nanoenabled consumer products. Plant’s central roles in ecosystem function and food chain integrity ensure intimate contact with water and soil systems, both of which are considered sinks for NPs accumulation. In this review, we document phytotoxicity caused by metal-based NPs exposure at physiological, biochemical, and molecular levels. Although the exact mechanisms of plant defense against nanotoxicity are unclear, several relevant studies have been recently published. Possible detoxification pathways that might enable plant resistance to oxidative stress and facilitate NPs detoxification are reviewed herein. Given the importance of understanding the effects and implications of metal-based NPs on plants, future research should focus on the following: (1) addressing key knowledge gaps in understanding molecular and biochemical responses of plants to NPs stress through global transcriptome, proteome, and metablome assays; (2) designing long-term experiments under field conditions at realistic exposure concentrations to investigate the impact of metal-based NPs on edible crops and the resulting implications to the food chain and to human health; and (3) establishing an impact assessment to evaluate the effects of metal-based NPs on plants with regard to ecosystem structure and function

Nylon Bristles and Elastomers Retain Centigram Levels of Triclosan and Other Chemicals from Toothpastes: Accumulation and Uncontrolled Release

Triclosan (TCS), a broad-spectrum antimicrobial, is used in commercial toothpastes with reported dental benefits. Our studies on 22 popular manual toothbrushes in the U.S. showed that common toothbrush head components can accumulate substantial amounts of TCS after brushing with TCS-formulated toothpastes (TCS-TPs). After simulated 3-month brushing with a commercial best-selling TCS-TP, over one third of the adults’ toothbrushes showed a cumulative TCS uptake of 21–37.5 mg, equivalent to 7–12.5 doses of the TCS used per brushing. Similar results were observed on children’s toothbrushes with small pea-size heads. Elastomer components were found to be the main contributor while both nylon bristles and elastomers could act as absorptive sinks for TCS during brushing. Studies on six different TCS-TPs containing 0.3 wt% TCS showed similar profiles of TCS accumulation. The absorbed TCS was gradually released into toothpaste slurries after switching to TCS-free alternatives. Release of TCS, which typically measured at a fraction (<75%) of the standard dose using the TCS-TPs, continued for over 2 weeks and occurred most rapidly in peroxide-containing “whitening” toothpastes, followed by alkaline and surfactant-rich toothpastes. The accumulating effect was not exclusive to TCS but was commonly observed on several chemicals identified in TCS-TPs and a range of regular toothpastes

Plant Response to Metal-Containing Engineered Nanomaterials: An Omics-Based Perspective

The increasing use of engineered nanomaterials (ENMs) raises questions regarding their environmental impact. Improving the level of understanding of the genetic and molecular basis of the response to ENM exposure in biota is necessary to accurately assess the true risk to sensitive receptors. The aim of this Review is to compare the plant response to several metal-based ENMs widely used, such as quantum dots, metal oxides, and silver nanoparticles (NPs), integrating available “omics” data (transcriptomics, miRNAs, and proteomics). Although there is evidence that ENMs can release their metal components into the environment, the mechanistic basis of both ENM toxicity and tolerance is often distinct from that of metal ions and bulk materials. We show that the mechanisms of plant defense against ENM stress include the modification of root architecture, involvement of specific phytohormone signaling pathways, and activation of antioxidant mechanisms. A critical meta-analysis allowed us to identify relevant genes, miRNAs, and proteins involved in the response to ENMs and will further allow a mechanistic understanding of plant–ENM interactions

CuO Nanoparticle Interaction with Human Epithelial Cells: Cellular Uptake, Location, Export, and Genotoxicity

The toxicity of CuO nanoparticles (NPs) to human lung epithelial (A549) cells was investigated in this study. CuO NPs (10–100 mg/L) had significant toxicity to A549 cells, whereas CuO bulk particles (BPs) showed much lower toxicity (24 h IC₅₀, 58 and 15 mg/L for CuO BPs and NPs, respectively). Transmission electron microscopic analysis demonstrated CuO NP entry into A549 cells and organelles, including lysosomes, mitochondria, and nucleus. Endocytosis was the primary pathway of CuO NPs uptake. CuO NPs (15 mg/L) induced mitochondrial depolarization, possibly mediated by reactive oxygen species (ROS) generation. Intracellular CuO NPs first generate ROS, which subsequently induces the expression of <i>p38</i> and <i>p53</i> and ultimately causes DNA damage (Comet assay). We confirm for the first time that the primary cytotoxic response is oxidative stress rather than DNA damage. A fraction of the CuO NPs was exported to the extracellular environment. In this study, centrifugal ultrafiltration tubes were successfully employed to determine the dissolved Cu²⁺ from CuO NPs in the cell medium. Dissolved Cu²⁺ ions contributed less than half of the total toxicity caused by CuO NPs, including ROS generation and DNA damage. This study provided useful data for understanding transport and toxicity of metal oxide NPs in human cells

CuO Nanoparticle Interaction with <i>Arabidopsis thaliana</i>: Toxicity, Parent-Progeny Transfer, and Gene Expression

CuO nanoparticles (NPs) (20, 50 mg L^–1) inhibited seedling growth of different <i>Arabidopsis thaliana</i> ecotypes (Col-0, Bay-0, and Ws-2), as well as the germination of their pollens and harvested seeds. For most of growth parameters (e.g., biomass, relative growth rate, root morphology change), Col-0 was the more sensitive ecotype to CuO NPs compared to Bay-0 and Ws-2. Equivalent Cu²⁺ ions and CuO bulk particles had no effect on <i>Arabidopsis</i> growth. After CuO NPs (50 mg L^–1) exposure, Cu was detected in the roots, leaves, flowers and harvested seeds of <i>Arabidopsis</i>, and its contents were significantly higher than that in CuO bulk particles (50 mg L^–1) and Cu²⁺ ions (0.15 mg L^–1) treatments. Based on X-ray absorption near-edge spectroscopy analysis (XANES), Cu in the harvested seeds was confirmed as being mainly in the form of CuO (88.8%), which is the first observation on the presence of CuO NPs in the plant progeny. Moreover, after CuO NPs exposure, two differentially expressed genes (C-1 and C-3) that regulated root growth and reactive oxygen species generation were identified, which correlated well with the physiological root inhibition and oxidative stress data. This current study provides direct evidence for the negative effects of CuO NPs on <i>Arabidopsis</i>, including accumulation and parent-progeny transfer of the particles, which may have significant implications with regard to the risk of NPs to food safety and security

Plant Response to Metal-Containing Engineered Nanomaterials: An Omics-Based Perspective

The increasing use of engineered nanomaterials (ENMs) raises questions regarding their environmental impact. Improving the level of understanding of the genetic and molecular basis of the response to ENM exposure in biota is necessary to accurately assess the true risk to sensitive receptors. The aim of this Review is to compare the plant response to several metal-based ENMs widely used, such as quantum dots, metal oxides, and silver nanoparticles (NPs), integrating available “omics” data (transcriptomics, miRNAs, and proteomics). Although there is evidence that ENMs can release their metal components into the environment, the mechanistic basis of both ENM toxicity and tolerance is often distinct from that of metal ions and bulk materials. We show that the mechanisms of plant defense against ENM stress include the modification of root architecture, involvement of specific phytohormone signaling pathways, and activation of antioxidant mechanisms. A critical meta-analysis allowed us to identify relevant genes, miRNAs, and proteins involved in the response to ENMs and will further allow a mechanistic understanding of plant–ENM interactions

Additional file 1 of Vitamin D modulation of brain-gut-virome disorder caused by polystyrene nanoplastics exposure in zebrafish (Danio rerio)

Additional file 1: Text S1. TEM analysis. Text S2. Determination of biochemical parameters. Text S3. Gut Virome Analysis. Figure S1. Accumulation of PS-NPs in the brain tissues of zebrafish and changes of related growth parameters (0.2 μm). (A) TEM observation of PS-NPs in brain tissue, (a), (b), (c), (d), (e), and (f) represent the group of 0-, 0+, 15-, 15+, 150-, and 150+, respectively, the blue arrow points to the NPs; (B) The number of NPs in brain tissue (n=3 replicates); (C) BSI (%). Data are expressed as means±SD. *p<0.05 indicate significant differences between the exposure groups and the control group. Figure S2. (A) Average velocity (mm/s); (B) Average acceleration (mm/s2); (C) and (D) represents the content of cortisol and OT in zebrafish brain samples. Data are expressed as means±SD. *p<0.05 indicate significant differences between the exposure groups and the control group. Figure S3. (A) Relative abundance of bacteria at the genus level (top 10) (n=3 replicates); (B) The relative abundance of Exiguobacterium. Data are expressed as means±SD. *p<0.05 indicate significant differences between exposure groups and the control group; #p<0.05 indicate significant differences between vitamin D-high and vitamin D-low groups at the same PS-NPs concentration. Table S1. Differentially expressed virus in 15+ vs 15- comparison. Table S2. Differentially expressed virus in 150+ vs 150- comparison. Table S3. Primer information used in qRT-PCR. All sequences are shown 5’-3’

Interactions of CuO nanoparticles with the algae <i>Chlorella pyrenoidosa</i>: adhesion, uptake, and toxicity

<p>The potential adverse effects of CuO nanoparticles (NPs) have increasingly attracted attention. Combining electron microscopic and toxicological investigations, we determined the adhesion, uptake, and toxicity of CuO NPs to eukaryotic alga <i>Chlorella pyrenoidosa</i>. CuO NPs were toxic to <i>C. pyrenoidosa</i>, with a 72 h EC₅₀ of 45.7 mg/L. Scanning electron microscopy showed that CuO NPs were attached onto the surface of the algal cells and interacted with extracellular polymeric substances (EPS) excreted by the organisms. Transmission electron microscopy (TEM) showed that EPS layer of algae was thickened by nearly 4-fold after CuO NPs exposure, suggesting a possible protective mechanism. In spite of the thickening of EPS layer, CuO NPs were still internalized by endocytosis and were stored in algal vacuoles. TEM and electron diffraction analysis confirmed that the internalized CuO NPs were transformed to Cu₂O NPs (d-spacing, ∼0.213 nm) with an average size approximately 5 nm. The toxicity investigation demonstrated that severe membrane damage was observed after attachment of CuO NPs with algae. Reactive oxygen species generation and mitochondrial depolarization were also noted upon exposure to CuO NPs. This work provides useful information on understanding the role of NPs–algae physical interactions in nanotoxicity.</p

Nanoparticle interactions with co-existing contaminants: joint toxicity, bioaccumulation and risk

<p>With their growing production and application, engineered nanoparticles (NPs) are increasingly discharged into the environment. The released NPs can potentially interact with pre-existing contaminants, leading to biological effects (bioaccumulation and/or toxicity) that are poorly understood. Most studies on NPs focus on single analyte exposure; the existing literature on joint toxicity of NPs and co-existing contaminants is rather limited but beginning to develop rapidly. This is the first review paper evaluating the current state of knowledge regarding the joint effects of NPs and co-contaminants. Here, we review: (1) methods for investigating and evaluating joint effects of NPs and co-contaminants; (2) simultaneous toxicities from NPs co-exposed with organic contaminants, metal/metalloid ions, dissolved organic matter (DOM), inorganic ligands and additional NPs; and (3) the influence of NPs co-exposure on the bioaccumulation of organic contaminants and heavy metal ions, as well as the influence of contaminants on NPs bioaccumulation. In addition, future research needs are discussed so as to better understand risk associated with NPs-contaminant co-exposure.</p

Nitrogen-Doped Carbon Dots Facilitate CRISPR/Cas for Reducing Antibiotic Resistance Genes in the Environment

The continued acquisition and propagation of antibiotic resistance genes (ARGs) in the environment confound efforts to manage the global rise in antibiotic resistance. Here, CRISPR-Cas9/sgRNAs carried by nitrogen-doped carbon dots (NCDs) were developed to precisely target multi-“high-risk” ARGs (tet, cat, and aph(3′)-Ia) commonly detected in the environment. NCDs facilitated the delivery of Cas9/sgRNAs to Escherichia coli (E. coli) without cytotoxicity, achieving sustained elimination of target ARGs. The elimination was optimized using different weight ratios of NCDs and Cas9 protein (1:1, 1:20, and 1:40), and Cas9/multi sgRNAs were designed to achieve multi-cleavage of ARGs in either a single strain or mixed populations. Importantly, NCDs successfully facilitated Cas9/multi sgRNAs for resensitization of antibiotic-resistant bacteria in soil (approaching 50%), whereas Cas9/multi sgRNAs alone were inactivated in the complex environment. This work highlights the potential of a fast and precise strategy to minimize the reservoir of antibiotic resistance in agricultural system