Toxicity Of AgNPs Research Articles

Ecotoxicity of nanosilver on cladocerans and the role of algae provision.

Silver nanoparticles (AgNPs) are applied in diverse industries due to their biocide and physicochemical properties; therefore, they can be released into aquatic systems, interact with environmental factors, and ultimately exert adverse effects on the biota. We analyzed AgNPs effects on Ceriodaphnia reticulata (Cladocera) through mortality and life-history traits, considering the influence of food (Tetradesmus obliquus, Chlorophyceae) presence and concentration. C. reticulata was exposed to AgNPs in acute (absence and two algae concentrations plus five AgNPs treatments) and chronic assays (two algae concentrations plus three AgNPs treatments). AgNPs did not affect algae flocculation but increased Ag+ release, being these ions less toxic than AgNPs (as proved by the exposure to AgNO3). A reduction in AgNPs acute toxicity was observed when algae concentration increased. Acute AgNP exposure decreased C. reticulata body size and heart rate. The chronic AgNP exposure reduced C. reticulata molt number, growth, heart rate, and neonate size:number ratio, being these effects mitigated at the highest algae concentration. Increases in relative size and number of neonates were observed in AgNP treatments suggesting energy trade off. The increased Ag+ release with food presence suggests that the AgNP-algae interaction might be responsible of the decreased toxicity. Although algae reduced AgNP toxicity, they still exerted adverse effects on C. reticulata below predicted environmental concentrations. Since algae presence reduces AgNP effects but increases Ag+ release, studies should be continued to provide evidence on their toxicity to other organisms.

Ethylene Renders Silver Nanoparticles Stress Tolerance in Rice Seedlings by Regulating Endogenous Nitric Oxide Accumulation.

Developments in the field of nanotechnology over the past few years have increased the prevalence of silver nanoparticles (AgNPs) in the environment, resulting in increased exposure of plants to AgNPs. Recently, various studies have reported the effect of AgNPs on plant growth at different concentrations. However, identifying the mechanisms and signaling molecules involved in plant responses against AgNPs stress is crucial to find an effective way to deal with the phytotoxic impacts of AgNPs on plant growth and development. Therefore, this study was envisaged to investigate the participation of ethylene in mediating the activation of AgNPs stress tolerance in rice (Oryza sativa L.) through a switch that regulates endogenous nitric oxide (NO) accumulation. Treatment of AgNPs alone hampered the growth of rice seedlings due to severe oxidative stress as a result of decline in sulfur assimilation, glutathione (GSH) biosynthesis and alteration in the redox status of GSH. These results are also accompanied by the higher endogenous NO level. However, addition of ethephon (a donor of ethylene) reversed the AgNP-induced effects. Though the application of silicon nanoparticles (SiNPs) alone promoted the growth of rice seedlings but, interestingly their application in combination with AgNPs enhanced the AgNP-induced toxicity in the seedlings through the same routes as exhibited in the case of AgNPs alone treatment. Interestingly, addition of ethephon reversed the negative effects of SiNPs under AgNPs stress. These results suggest that ethylene might act as a switch to regulate the level of endogenous NO, which in turn could be associated with AgNPs stress tolerance in rice. Furthermore, the results also indicated that addition of l-NG-nitro arginine methyl ester (l-NAME) (an inhibitor of endogenous NO synthesis) also reversed the toxic effects of SiNPs together with AgNPs, further suggesting that the low level of endogenous NO was associated with AgNPs stress tolerance. Overall, the results indicate that the low level of endogenous NO triggers AgNPs stress tolerance, while high level leads to AgNPs toxicity by regulating sulfur assimilation, GSH biosynthesis, redox status of GSH and oxidative stress markers. The results revealed that ethylene might act as a switch for regulating AgNPs stress in rice seedlings by controlling endogenous NO accumulation.

Nanodelivery of antiretroviral drugs to nervous tissues.

Despite the development of effective combined antiretroviral therapy (cART), the neurocognitive impairments associated with human immunodeficiency virus (HIV) remain challenging. The presence of the blood-brain barrier (BBB) and blood-cerebrospinal fluid barrier (BCFB) impedes the adequate penetration of certain antiretroviral drugs into the brain. In addition, reports have shown that some antiretroviral drugs cause neurotoxicity resulting from their interaction with nervous tissues due to long-term systemic exposure. Therefore, the research into the effective therapeutic modality that would cater for the HIV-associated neurocognitive disorders (HAND) and ART toxicity is now receiving broad research attention. Thus, this review explores the latest information in managing HAND using a nanoparticle drug delivery system (NDDS). We discussed the neurotoxicity profile of various approved ART. Also, we explained the applications of silver nanoparticles (AgNPs) in medicine, their different synthesis methods and their interaction with nervous tissues. Lastly, while proposing AgNPs as useful nanoparticles in properly delivering ART to enhance effectiveness and minimize neurocognitive disorders, we hypothesize that the perceived toxicity of AgNPs could be minimized by taking appropriate precautions. One such precaution is using appropriate reducing and stabilizing agents such as trisodium citrate to reduce silver ion Ag + to ground state Ag0 during the synthesis. Also, the usage of medium-sized, spherical-shaped AgNPs is encouraged in AgNPs-based drug delivery to the brain due to their ability to deliver therapeutic agents across BBB. In addition, characterization and functionalization of the synthesized AgNPs are required during the drug delivery approach. Putting all these factors in place would minimize toxicity and enhance the usage of AgNPs in delivering therapeutic agents across the BBB to the targeted brain tissue and could cater for the HIV-associated neurocognitive disorders and neurotoxic effects of antiretroviral drugs (ARDs).

Silver nanoparticle toxicity to the larvae of oyster Crassostrea angulata: Contribution of in vivo dissolution

Understanding the toxic mechanism of silver nanoparticles (AgNPs) is crucial for it risk assessment in marine environment, but the role of Ag+ release in the AgNP toxicity to marine biota is not yet well addressed. This study investigated the toxicity of AgNPs to the veliger larvae of oyster Crassostrea angulata, with a specific focus on the possibility of the involvement of in vivo dissolution of AgNPs in the toxicity via an aggregation-induced emission luminogen (AIEgen)-based imaging technique. AgNO3 exhibited significantly greater toxicity than AgNPs based on the total Ag, as indicated by lower 50 % growth inhibition concentration (EC50). The average concentration of soluble Ag in seawater at the EC50 of AgNPs was far lower than the EC50 of AgNO3, indicating that the AgNP toxicity could not be fully explained by the dissolved Ag in the medium. Despite the comparable soluble Ag concentration in seawater for both treatments, more Ag was accumulated in the larvae exposed to AgNPs, suggesting their ability to directly ingest particulate Ag, which was further confirmed by the presence of AgNPs aggregates in the esophagus and stomach. With the application of AIEgen-based imaging technique, in vivo dissolution of AgNPs in oyster larvae was thoroughly verified by an increase in Ag(I) content in the larvae exposed to AgNPs after depuration. The results collectively implied that apart from the Ag released in the medium, the Ag dissolved from the ingested AgNPs may also greatly contribute to the toxicity of AgNPs toward the oyster larvae. The findings of this work shed new light on the bioavailability and toxicity of AgNPs in marine environment.

Toxicity of Silver Nanoparticles in the Presence of Zinc Oxide Nanoparticles Differs for Acute and Chronic Exposures in Zebrafish.

We assessed the acute toxicity effects (96h) of silver nanoparticles (Ag NPs) and zinc oxide nanoparticles (ZnO NPs) and chronic (28d) exposure to Ag NPs, including in combination with ZnO NPs. In the chronic studies, we further assessed the toxicokinetics and bioaccumulation of Ag and the resulting histopathological effects in the gill, intestine, and liver of zebrafish. Co-exposures with ZnO NPs reduced the toxicity of Ag NPs for acute (lethality) but enhanced the toxicity effects (tissue histopathology) for chronic exposures. The histological lesions for both NPs exposures in the gill included necrosis and fusion of lamellae, for the intestine necrosis and degeneration, and in the liver, mainly necrosis. The severity of the histological lesions induced by the Ag NPs was related to the amount of accumulated Ag in the zebrafish organs. The Ag accumulation in different organs was higher in the presence of ZnO NPs in the order of the gill > intestine > liver. Depuration kinetics illustrated the lowest half-life for Ag occurred in the gill and for the combined exposure of Ag with ZnO NPs. Our findings illustrate that in addition to tissue, time, and exposure concentration dependencies, the Ag NPs toxicity can also be influenced by the co-exposure to other NPs (here ZnO NPs), emphasizing the need for more combination exposure effects studies for NPs to more fully understand their potential environmental health risks.

Effects of silver nanoparticles on denitrification and anammox in sediments of hypertrophic and mesotrophic lakes

The abundant production and wide usage of silver nanoparticles (Ag NPs) inevitably lead to their release into aquatic ecosystems. However, it is still unclear about how Ag NPs influence denitrification and anammox (DA) in freshwater sediments. To address this, the sediments of hypertrophic and mesotrophic lakes were exposed to 0.5 and 50 mg/L Ag NPs under anaerobic conditions for 7 days to explore the effects of Ag NPs on environmental variables, including redox potential (Eh), pH, organic matter (OM) and acid volatile sulfide (AVS), and the resulting influence on DA. Experimental results indicated that NO3−-N and NH4+-N levels were increased by the low (p > 0.05) and high doses of Ag NPs (p < 0.05) in comparison with the non-Ag control, revealing an inhibitive impact on DA. The level of total nitrogen (TN) was notably increased by the low and high doses of Ag NPs (p < 0.05), perhaps due to inhibited enzyme activity and corresponding encoding gene abundance, which were related to generating gaseous nitrogen such as N2O and N2. In addition, environmental factor Eh was significantly raised by Ag NPs (p < 0.05), further inhibiting DA. Moreover, the quantitative analysis unveiled that denitrifying and anammox bacteria in hypertrophic lakes evinced a stronger resistance to Ag NPs toxicity than those in mesotrophic lakes. Overall, our study revealed that short-term exposure to Ag NPs could inhibit DA in sediments. These findings provide an understanding enabling evaluation and prediction of the environmental risks of Ag NPs in freshwater lakes.

Changes in Gut Microbiota Structure: A Potential Pathway for Silver Nanoparticles to Affect the Host Metabolism.

Silver nanoparticles (AgNPs) are one of the most widely used NPs. Their adverse effects on either the host or its gut microbiota (GM) have been examined. Nevertheless, whether the GM plays any role in AgNP toxicity to the host remains unclear. In the present study, AgNPs were administered to mice by oral gavage once a day for 120 days. A significant dose-dependent accumulation of Ag in the liver was observed, with a steady state reached within 21 days. The AgNPs changed the structure of the GM, mainly with respect to microorganisms involved in the metabolism of energy, amino acids, organic acids, and lipids, as predicted in a PICRUST analysis. Effects of the AgNPs on liver metabolism were also demonstrated, as a KEGG pathway analysis showed the enrichment of pathways responsible for the metabolism of amino acids, purines and pyrimidine, lipids, and energy. More interestingly, the changes in GM structure and liver metabolism were highly correlated, evidenced by the correlation between ∼23% of the differential microorganisms at the genus level and ∼60% of the differential metabolites. This implies that the metabolic variations in liver as affected by AgNPs were partly attributable to NP-induced changes of GM structure. Therefore, our results demonstrate the importance of considering the roles of GM in the toxicity of NPs to the host in evaluations of the health risks of NPs.

Toxic Effects of Silver Ions on Early Developing Zebrafish Embryos Distinguished from Silver Nanoparticles.

Currently, effects of nanomaterials and their ions, such as silver nanoparticles (Ag NPs) and silver ions (Ag+), on living organisms are not yet fully understood. One of the vital questions is whether nanomaterials have distinctive effects on living organisms from any other conventional chemicals (e.g., their ions), owing to their unique physicochemical properties. Due to various experimental protocols, studies of this crucial question have been inconclusive, which hinders rational design of effective regulatory guidelines for safely handling NPs. In this study, we chronically exposed early developing zebrafish embryos (cleavage-stage, 2 hours post-fertilization, hpf) to a dilution series of Ag+ (0-1.2 μM) in egg water (1 mM NaCl, solubility of Ag+ = 0.18 μM) until 120 hpf. We systematically investigated effects of Ag+ on developing embryos and compared them with our previous studies of effects of purified Ag NPs on developing embryos. We found the concentration- and time-dependent effects of Ag+ on embryonic development, and only half of the embryos developed normally after being exposed to 0.25 μM (27 μg/L) Ag+ until 120 hpf. As the Ag+ concentration increases, the number of embryos that developed normally decreases, while the number of embryos that became dead increases. The number of abnormally developing embryos increases as the Ag+ concentration increases from 0 to 0.3 μM and then decreases as the concentration increases from 0.3 to 1.2 μM because the number of embryos that became dead increases. The concentration-dependent phenotypes were observed, showing fin fold abnormality, tail and spinal cord flexure, and yolk sac edema at low Ag+ concentrations (≤0.2 μM) and head and eye abnormalities along with fin fold abnormality, tail and spinal cord flexure, and yolk sac edema at high concentrations (≥0.3 μM). Severities of phenotypes and the number of abnormally developing embryos were far less than those observed in Ag NPs. The results also show concentration-dependent effects on heart rates and hatching rates of developing embryos, attributing to the dose-dependent abnormally developing embryos. In summary, the results show that Ag+ and Ag NPs have distinctive toxic effects on early developing embryos, and toxic effects of Ag+ are far less severe than those of Ag NPs, which further demonstrates that the toxicity of Ag NPs toward embryonic development is attributed to the NPs themselves and their unique physicochemical properties but not the release of Ag+ from the Ag NPs.

Beneficial effects of Spirulina platensis on mice testis damaged by silver nanoparticles.

Silver nanoparticles (AgNPs) have been used widely in medical applications and various industries. Humans could be exposed to the risk of AgNPs toxicity through different routes. The current study aimed to investigate the role of Spirulina platensis (SP) against the side effects of AgNPs on mice testis. Adult male NMRI mice were divided into four groups: control group, SP group (300 mg/kg bwt), AgNPs (20 nm) group (500 mg/kg bwt), Co-treated group (SP + AgNPs). The groups were treated orally for 35 days. Subsequently, epididymal sperm parameters, sperm DNA integrity, daily sperm production (DSP), sexual hormones level, malondialdehyde (MDA), total antioxidant capacity (TAC) and spermatogenesis indices were measured. In addition, the histopathology of testes was evaluated using tissue processing, haematoxylin-eosin staining and stereology techniques. A significant decrease in the number of spermatogenic cells, Leydig cells and sperm parameters was observed in the AgNPs treated group. Serum levels of testosterone and TAC were decreased significantly following AgNPs treatment. Also, MDA incremented in the serum of AgNPs treated mice. The stereological analysis revealed that AgNPs exposure induced histopathological changes in the seminiferous tubules, degeneration and dissociation of spermatogenic cells. In contrast, SP co-administration significantly counteracted AgNPs reproductive toxicity impacts. SP co-exposure caused an increase in spermatogenesis indices, TAC and also a decrease in MDA. SP improved the histopathological changes of testes tissue and spermatozoa abnormalities. In parallel, SP modulated levels of testosterone, FSH and LH. Spirulina platensis exhibited the protective potential by regulating oxidative stress against AgNPs-induced reproductive toxicity. SP could be a candidate therapy against AgNPs reprotoxic impacts.

Synthesis of Silver Nanoparticles by Raoultella Planticola and Their Potential Antibacterial Activity Against Multidrug-Resistant Isolates.

Nanoparticles can be chemically, physically, or biologically synthesized. Biosynthesis of silver nanoparticles (AgNPs) utilizing microbes is a promising process due to the low toxicity and high stability of AgNPs. Here, AgNPs were fabricated by Gram-negative Raoultella planticola. This study aimed to assess the ability of Raoultella planticola to produce nanoparticles (NPs) and evaluate their antibacterial potential against multidrug-resistant pathogens (MDR). Additionally, the study aimed to compare the antibacterial activity of biosynthesized nanoparticles to well-known conventional antibiotics Azithromycin and Tetracycline. AgNPs were characterized using visual observation, UV-visible spectroscopy (UV-vis), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR). The TEM and SEM were used to determine the size and shape of the nanoparticles. The XRD data were recorded in the 2θ ranging from 20-80° to analyze the crystalline structure of nanoparticles. The antibacterial activity was detected using a 96-well microtiter plate. The UV-vis absorption recorded from the 300 - 900 nm spectrum was well defined at 420 nm, and the XRD pattern was compatible with Braggs's reflection of the silver nanocrystals. FTIR showed absorbance bands corresponding to different functional groups. TEM and SEM images showed non-uniform spherical and AgNPs of 10-80 nm. XRD data confirmed that the resultant particles are AgNPs. The AgNPs showed effective activity against multi-drug resistant (MDR) Pseudomonas aeruginosa, Salmonella sp., Shigella sp., E. coli, Enterobacter sp., Staphylococcus aureus, and Bacillus cereus. The AgNPs demonstrated effectiveness in lower concentrations compared to broad-spectrum antibiotics. These data reveal that AgNP generated by R. planticola was more efficient against MDR microorganisms than commercial antibiotics. However, the cytotoxicity of these nanoparticles must be further studied.

Particle surface functionalization affects mechanism of endocytosis and adverse effects of silver nanoparticles in mammalian kidney cells.

Silver nanoparticles (AgNPs) show a plethora of possible applications due to their antimicrobial properties. Different coatings of AgNPs are used in order to increase stability, availability, and activity. However, the question about the toxicity after prolonged exposure still remains. Here, we show that different surface coatings affect in vitro toxicity and internalization of AgNPs in porcine kidney (PK15) cells. AgNPs coated with cetyltrimethylammonium bromide (CTAB), poly(vinylpyrrolidone) (PVP), sodium bis(2-ethylhexyl)-sulfosuccinate (AOT), poly-L-lysine (PLL), and bovine serum albumin (BSA) were toxic at the concentration of 10mg Ag/L and higher. The toxicity increased in the following manner: PVP-AgNPs < CTAB-AgNPs < PLL-AgNPs < AOT-AgNPs < BSA-AgNPs. All types of AgNPs were internalized by the PK15 cells in a dose-dependent manner with greater internalization of AgNPs bearing positive surface charge. Transmission electron microscopy (TEM) experiments showed that AgNPs were located in the lysosomal compartments, while the co-treatment with known inhibitors of endocytosis pathways suggested macropinocytosis as the preferred internalization pathway. When inside the cell, all types of AgNPs induced the formation of reactive oxygen species while decreasing the concentration of the cell's endogenous antioxidant glutathione. The comet assay indicated possible genotoxicity of tested AgNPs starting at the concentration of 2mg Ag/L or higher, depending on the surface functionalization. This study demonstrates the toxicity of AgNPs pointing to the importance of biosafety evaluation when developing novel AgNPs-containing materials.

Shape-Dependent Toxicity of Silver Nanoparticles on Freshwater Cnidarians.

Silver nanoparticles (AgNPs) are increasingly used in various consumer products, leading to their inadvertent release in aquatic ecosystems. The toxicity of AgNPs could be associated with the leaching of ionic Ag but also with the size, shape and surface properties. The purpose of this study was to test the null hypothesis that toxicity of AgNPs was independent of shape in the invertebrate Hydra vulgaris. The hydranths were exposed to increasing concentrations of ionic Ag and AgNPs of three different shapes (spherical, cubic and prismatic) with the same size and coating (polyvinylpyrrolidone). The data revealed that between 68% and 75% of total Ag remained in solution after the 96 h exposure period, while 85–90% of ionic Ag remained in solution. The 96 h lethal concentration (LC50) was lower with ionic (4 µg/L) and spherical AgNPs (56 µg/L), based on irreversible morphological changes such as loss of tentacles and body disintegration. Cubic and prismatic AgNPs were not toxic at a concentration of <100 µg/L. The sublethal toxicity was also determined at 96 h based on characteristic morphological changes (clubbed and/or shortened tentacles) and showed the following toxicity: ionic (2.6 µg/L), spherical (22 µg/L) and prismatic (32.5 µg/L) AgNPs. The nanocube was not toxic at this level. The data indicated that toxicity was shape-dependent where nanoparticles with a low aspect ratio in addition to high circularity and elongation properties were more toxic at both the lethal and sublethal levels. In conclusion, the shape of AgNPs could influence toxicity and warrants further research to better understand the mechanisms of action at play.

Antibacterial and Wound Healing Properties of AgNPs Combined with Other Natural Materials

With the development of new technology industry, nanoparticle is more and more getting valued as one of the most promising technologies in the technological revolution in the 21st century. In recent years, nanotechnology applied in biomedicine is in the ascendant and among the most metal nanoparticles, the silver nanoparticle(AgNP) is s kind of the most common nanomaterials used in wound healing according to its antibacterial properties. For the consideration of biocompatibility and dispersion of the AgNPs, nanocomposites that AgNPs combined with other natural materials like lignin, chitosan, nanofiber and cellulose have been researched a lot to apply to synthesize the wound healing materials. However, there is no sufficient evidence to prove the mechanism of the AgNPs’ toxicology until now. Nowadays, AgNPs have been widely used in products, as a result, how to correctly explain the toxicity of AgNPs and the safety to human body and the environment is urgent. In this article, the use of AgNPs combined with other natural materials is reviewed. Furthermore, the possible toxicology which is not mentioned before and the possible solutions are proposed.

Surface chemistry driven selective anticancer potential of functional silver nanoparticles toward lung cancer cells

Decades of nanomedicine research has demonstrated the importance of physicochemical properties to tightly regulate cytotoxicity of nanoparticles. Wherein, the tailor-made surface corona of nanoparticles may dictate nano-bio interfacial interactions toward therapeutic benefits without any significant nanotoxicity. Therefore, in the current research, selective anticancer effects originating from the specific surface chemistry of silver nanoparticles (AgNPs) is demonstrated employing lung cells. The AgNPs are synthesized by bioactive curcumin (Cur) to form a stable corona around AgNPs, and further surface functionalized with an antibiotic isonicotinic acid hydrazide (INH, isoniazid). These NPs were subjected to various structural and spectroscopy analysis for deeper understanding of the surface chemistry, followed by the anticancer potential assessment on LK-2 lung cancer cells. The higher production of reactive oxygen species (ROS) was responsible for therapeutic effects on LK-2 cells. The TUNEL and apoptotic dye studies revealed and confirmed the role of apoptosis in the ROS-mediated selective death of lung cancer cells over human foetus lung diploid fibroblasts (WI-38). Furthermore, the involvement of mitochondria in mediating the effects of AgNP's toxicity is demonstrated. The study provides a deeper understanding regarding the mechanism of anti-cancer actions of the formulated functional AgNPs, and it has potential to open new avenues for tailor-made surfaces chemistry driven nanomedicine development.

New Insights for Exploring the Risks of Bioaccumulation, Molecular Mechanisms, and Cellular Toxicities of AgNPs in Aquatic Ecosystem

Silver nanoparticles (AgNPs) are commonly used in numerous consumer products, including textiles, cosmetics, and health care items. The widespread usage of AgNPs results in their unavoidable discharge into the ecosystem, which pollutes the aquatic, groundwater, sediments, and marine environments. These nanoparticles (NPs) activate the production of free radicals reactive species in aquatic organisms that interrupt the functions of DNA, cause mitochondrial dysfunction, and increase lipid peroxidation, which terminates the development and reproduction both in vivo and in vitro. The life present in the aquatic ecosystem is becoming threatened due to the release and exploitation of AgNPs. Managing the aquatic ecosystem from the AgNP effects in the near future is highly recommended. In this review, we discussed the background of AgNPs, their discharge, and uptake by aquatic organisms, the mechanism of toxicity, different pathways of cytotoxicity, and bioaccumulation, particularly in aquatic organisms. We have also discussed the antimicrobial activities of AgNPs along with acute and chronic toxicity in aquatic groups of organisms.

Green nanopriming: responses of alfalfa (Medicago sativa L.) seedlings to alfalfa extracts capped and light-induced silver nanoparticles

The application of nanotechnology in agriculture can remarkably improve the cultivation and growth of crop plants. Many studies showed that nanoparticles (NPs) made plants grow more vigorously. Light can make NPs aggregated, leading to the reduction of the NPs toxicity. In addition, treatment with NPs had a “hormesis effect” on plants. In this study, light-induced silver nanoparticles (AgNPs) were synthesized by using the alfalfa (Medicago sativa L.) extracts, and then the optimal synthetic condition was determined. Light-induced AgNPs were aggregated, spherical and pink, and they were coated with esters, phenols, acids, terpenes, amino acids and sugars, which were the compositions of alfalfa extracts. The concentration of free Ag+ was less than 2 % of the AgNPs concentration. Through nanopriming, Ag+ got into the seedlings and caused the impact of AgNPs on alfalfa. Compared with the control group, low concentration of light-induced AgNPs had a positive effect on the photosynthesis. It was also harmless to the leaf cells, and there was no elongation effect on shoots. Although high concentration of AgNPs was especially beneficial to root elongation, it had a slight toxic effect on seedlings due to the accumulation of silver. With the increase of AgNPs concentration, the content of silver in the seedlings increased and the silver enriched in plants was at the mg/kg level. Just as available research reported the toxicity of NPs can be reduced by using suitable synthesis and application methods, the present light induction, active material encapsulation and nanopriming minimized the toxicity of AgNPs to plants, enhancing the antioxidant enzyme system.Graphical

Effect of organic matter on the trophic transfer of silver nanoparticles in an aquatic food chain

The behavior and toxicity of nanoparticles could be affected significantly by the ubiquitous natural organic matter (NOM) in aquatic environments. However, the influence of NOM on nanoparticles along the food chain remains largely unknown. This study constructed bacteria Escherichia coli (E. coli) - protozoa Tetrahymena thermophila (T. thermophila) to evaluate the influence of NOM on the bioaccumulation, trophic transfer and toxicity of silver nanoparticles (Ag NPs). Results demonstrated that NOM could reduce the toxicity of Ag NPs to E. coli and T. thermophila by different influence mechanisms (e.g., reduce Ag NPs accumulation or complex with dissolved silver ion (Ag+)) which related to the type of NOM and organisms. Moreover, Ag NPs can be transferred and biomagnified to T. thermophila via trophic transfer. Three typical NOM could significantly increase the trophic transfer factors of Ag NPs ranging from 1.16 to 2.49, which may be ascribed to NOM reducing the capacity for T. thermophila to excrete total silver (Ag) as NOM could significantly change the form of Ag. These findings provide a novel insight into the impact of NOM on the ecological risk posed by Ag NPs through the food chain and emphasize the need to understand further the interactions between nanoparticles and NOM in various ecosystems.

Differential tolerance of Trichoderma harzianum and Rhizoctonia solani towards silver nanoparticles: potential for agricultural applications?

In the previous study, we examined the effect of silver nanoparticles (AgNPs) on beneficial soil fungus including Trichoderma harzianum (T22), and pathogenic soil-borne fungus, Rhizoctonia solani (AG3-PT). The result exhibited that T. harzianum (T22) is tolerance towards AgNPs. On the other hand, the pathogenic fungi, R.solani (AG3-PT), is more sensitive to AgNPs. T. harzianum is well known as biocontrol agent to suppress R. solani. Therefore, in this study we investigated the combination of T. harzianum (T22) and AgNPs at low concentration to control two strains of R. solani (AG3-PT and AG2-1). The effect of AgNPs at two different levels (20 mg L-1 and 50 mg L-1) was examined over the growth of the two strains of R. solani and T. harzianum (T22) using dual culture technique. The results shows that this combination have a potential to reduce colony growth of R. solani (AG2-1) at higher AgNPs concentration. However, it was not the case for R. solani (AG3-PT). It can be concluded that AgNPs toxicity depend on several factors including species strain and the size of AgNPs particle.

Trophic transfer and toxicity of silver nanoparticles along a phytoplankton-zooplankton-fish food chain

This study evaluated the bioconcentration metrics, organ-specific distribution, and trophic consequences of silver nanoparticles along a Dunaliella salina-Artemia salina-Poecilia reticulata food chain. To this end, accumulation, tissue-specific distribution, bioconcentration and biomagnification factors, and trophic toxicity of AgNPs were quantitatively investigated along di- and tri-trophic food chains. Overall, silver accumulation increased markedly in intestine and liver tissues, carcass, and embryos of guppy fish with rising exposure concentrations and reducing trophic levels. Following trophic and waterborne exposure, AgNPs illustrated a regular tendency in following order: intestine > liver > embryos > carcass. BCF displayed values of 826, 131, and ≈ 1000 for microalgae, brine shrimp, and guppy fish, respectively. Moreover, BMF showed values <1.00 for 48-h post-hatched nauplii and guppy fish received AgNPs-exposed phytoplankton, yet >1.00 for the liver and whole body of guppy fish treated with AgNPs-exposed nauplii through algae and water, indicating that AgNPs could be biomagnified from the second to third trophic level, but not from the first to second or third levels. Furthermore, the waterborne and trophic exposure of AgNPs considerably induced oxidative stress and reproductive toxicity. Together, this study demonstrated that AgNPs could be biomagnified across trophic chain and consequently cause trophic toxicity.

Silver nanoparticles induced hippocampal neuronal damage involved in mitophagy, mitochondrial biogenesis and synaptic degeneration

Silver nanoparticles (AgNPs) could accumulate in the central nervous system (CNS) and induce neurotoxicity for their widespread use in industry and medicine. Mitochondria are vulnerable to toxicity of AgNPs, however, their role in the neurotoxicity remains unclear. This study aimed to evaluate AgNPs-induced synaptic degeneration in mouse hippocampal neurons (at a dose of 12–120 mg/kg BW via intravenous injection), and to further investigate mechanism of mitophagy, mitochondrial biogenesis process in the neurotoxicity. The results indicated that AgNPs accumulated in mouse hippocampal neurons and induced neurological deficits of learning and memory, which involved in synaptic degeneration accompanied with mitochondrial damage. Mechanistically, AgNPs exposure increased protein expression of PTEN-induced kinase 1 (PINK1), Parkin and inhibited peroxisome proliferator-activated receptor coactivator 1 alpha (PGC-1α) protein expression, caused disturbed mitophagy and mitochondrial biogenesis. AgNPs also induced synaptic damage by increasing the protein expression of synaptophysin and decreasing PSD95, MAP2 protein expression. AgNPs exposure even promoted protein expression of amyloid precursor protein (APP) using in amyloid-β (Aβ) cleavage. Furthermore, AgNPs induced hippocampal neuronal synaptic degeneration, mitophagy and mitochondrial biogenesis is dependent on particle-specific AgNPs rather than released silver ions. Our research could provide insights into the regulatory mechanisms of AgNPs-induced neurotoxicity. This study will shed the light of neurotoxicological evaluation of nanoparticles and possible early warning of biomedical applications.