Silver Accumulation Research Articles

Preparation and Biological Activity of Lignin-Silver Hybrid Nanoparticles.

Silver nanoparticles (AgNPs) are excellent antimicrobial agents and promising candidates for preventing or treating bacterial infections caused by antibiotic resistant strains. However, their increasing use in commercial products raises concerns about their environmental impact. In addition, traditional physicochemical approaches often involve harmful agents and excessive energy consumption, resulting in AgNPs with short-term colloidal stability and silver ion leaching. To address these issues, we designed stable hybrid lignin-silver nanoparticles (AgLigNPs) intended to effectively hit bacterial envelopes as a main antimicrobial target. The lignin nanoparticles (LigNPs), serving as a reducing and stabilizing agent for AgNPs, have a median size of 256 nm and a circularity of 0.985. These LigNPs were prepared using the dialysis solvent exchange method, producing spherical particles stable under alkaline conditions and featuring reducing groups oriented toward a wrinkled surface, facilitating AgNPs synthesis and attachment. Maximum accumulation of silver on the LigNP surface was observed at a mass reaction ratio mAg:mLig of 0.25, at pH 11. The AgLigNPs completely inhibited suspension growth and reduced biofilm development by 50% in three tested strains of Pseudomonas aeruginosa at a concentration of 80/9.5 (lignin/silver) mg L-1. Compared to unattached AgNPs, AgLigNPs required two to eight times lower silver concentrations to achieve complete inhibition. Additionally, our silver-containing nanosystems were effective against bacteria at safe concentrations in HEK-293 and HaCaT tissue cultures. Stability experiments revealed that the nanosystems tend to aggregate in media used for bacterial cell cultures but remain stable in media used for tissue cultures. In all tested media, the nanoparticles retained their integrity, and the presence of lignin facilitated the prevention of silver ions from leaching. Overall, our data demonstrate the suitability of AgLigNPs for further valorization in the biomedical sector.

Metal Bioaccumulation and Biochemical Responses in Loggerhead Turtles (Caretta caretta) from the Gulf of Gabès (Tunisia)

Caretta caretta (Cheloniidae, Cryptodira) is a species of turtle considered a ‘flagship species’ in the Mediterranean Sea. Unfortunately, the circular marine currents and semi-enclosed configuration of the Mediterranean Sea encourage the accumulation of pollutants (metals, pesticides, etc.) emitted by human activities. Tunisia suffers particularly from coastal urbanisation and industrial development. Metal concentrations (Ag, Al, As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Zn) were measured in distinct tissues (heart, kidney, liver, lung, muscle) of loggerhead turtles stranded in the Gulf of Gabès (Tunisia) to estimate the pollution levels in this emblematic species. High concentrations of arsenic and cadmium were found in marine turtles. Therefore, the differential accumulation of metals was measured in the tissues. For example, the liver appears to be a preferential organ for the accumulation of copper, iron, silver and zinc. In contrast, cobalt and cadmium were more concentrated in the kidneys, while arsenic, chromium and nickel were mainly found in the muscles. Antioxidant enzyme responses (catalase, GPx and SOD) and lipid peroxidation were more expressed in the liver and kidneys than in the muscles.

Long-term effects of silver nanoparticles and mineral nutrition components on the photosynthetic processes, chloroplast ultrastructure and productivity of Solanum lycopersicum plants

The effects of silver nanoparticles (AgNPs), both alone and in combination with mineral nutrients, on the growth and photosynthesis of Solanum lycopersicum plants during ontogeny were studied. The experiment involved weekly applications of 10 μmol of AgNPs for 15 weeks in a greenhouse over a summer period. A comprehensive characterization of the AgNPs was performed via TEM, ESI/EELS, and zeta potential measurements before and throughout the experiment. The activity of PSII, stomatal conductivity, photosynthesis, transpiration and respiration rates were measured, and the photosynthetic pigments, chloroplast ultrastructure, and dry and fresh masses of leaves, roots, and fruits were assessed. The results indicated that combining AgNPs with mineral nutrients increased PSII activity and the photosynthesis rate and altered the chloroplast ultrastructure. However, the use of mineral nutrients or AgNPs alone did not induce these changes. Atomic absorption spectrometry detected AgNPs in all the plant organs except the fruits. The highest fruit yield was associated with Veni Prisma®, a commercial product containing colloidal silver, which also caused desynchronized fruit maturation. This study hypothesizes that the synergistic effect of AgNPs and mineral nutrients enhances silver accumulation in chloroplasts, improving light utilization and photosynthetic efficiency, particularly under low light, thus increasing fruit quantity and dry mass. Conversely, long-term use of AgNPs alone was accompanied by silver accumulation outside the chloroplasts and did not lead to increased photosynthesis or an increase in fresh fruit mass.

Argyria and Neuropsychiatric Disorders: When not only the Matter is Gray. A Literature Review and a Case Report.

Argyria is the chronic accumulation of silver in biological tissues such as skin, liver, kidneys, lungs, peripheral nerves, and brain. The presence of an actual pathophysiological and clinical correlate related to silver encephalic and peripheral nerve deposition is still much debated. In this paper, we reviewed and described case reports regarding argyria associated with neuropsychiatric symptoms in order to explain the underlying mechanism of the disease. We conducted a narrative review by searching for case reports that described subjects with chronic silver accumulation and who had associated neurological or psychiatric symptoms. Moreover, we report a case of a 50-year-old man admitted to our hospital with a diagnosis of major depression who presented with worsening psychiatric symptoms after abuse of silver-containing nasal spray. We found 15 cases of patients with argyria and neuropsychiatric manifestations such as epilepsy, neurodegenerative syndromes, multiple sclerosis, peripheral neuropathy, and psychiatric disorders. The knowledge of possible pathogenetic mechanisms and recognition of clinical features of argyria can help clinicians prevent brain deposition and its complications.

Exploring the impact of silver-based nanomaterial feed additives on green algae through single-cell techniques

Silver in its various forms, including dissolved silver ions (Ag+) and silver nanoparticles (AgNPs), is a promising alternative to traditional antibiotics, largely used in livestock as feed additives and could contribute to the decrease and avoidance of the development of antibiotic resistance. The present study aims to assess the potential ecotoxicity of a silver-based nanomaterial (Ag-kaolin), the feed supplemented with the nanomaterial and the faeces since the latter are the ones that finally reach the environment. To this end, green alga Raphidocellis subcapitata was exposed to the extracts of Ag-kaolin, supplemented feed, and pig faeces for 72 h, along with Ag+ and AgNPs as controls for comparison purposes. Given the complexity of the studied materials, single-cell techniques were used to follow the changes in the cell numbers and chlorophyll fluorescence by flow cytometry, and the accumulation of silver in the exposed cells by single cell inductively coupled plasma mass spectrometry (SC-ICP-MS). Changes in cell morphology were observed by cell imaging multimode reader. The results revealed a decrease in chlorophyll fluorescence, even at low concentrations of Ag-kaolin (10 μg L−1) after 48 h of exposure. Additionally, complete growth inhibition was found with this material like the results obtained by exposure to Ag+. For the supplemented feed, a concentration of 50 μg L−1 was necessary to achieve complete growth inhibition. However, the behaviour differed for the leachate of faeces, which released Ag2S and AgCl alongside Ag+ and AgNPs. At 50 μg L−1, inhibition was minimal, primarily due to the predominance of less toxic Ag2S in the leachate. The uptake of silver by the cells was confirmed with all the samples through SC-ICP-MS analysis. These findings demonstrate that the use of Ag-kaolin as a feed supplement will lead to a low environmental impact.

Attenuation of photosynthesis in nanosilver-treated Arabidopsis thaliana is inherently linked to the particulate nature of silver

Silver nanoparticles (AgNPs) are known to affect the physiology and morphology of plants in various ways, but the exact mechanism by which they interact with plant cells remains to be elucidated. An unresolved question of silver nanotoxicology is whether the interaction is triggered by the physical features of the particles, or by silver ions leached from their surface. In this study, we germinated and grew Arabidopsis thaliana seedlings in synthetic medium supplemented with sub-morbid concentrations (4 μg/mL) of AgNPs and silver nitrate (AgNO3). This treatment led to in planta accumulation of 106 μg/g and 97 μg/g of silver in the AgNO3- and AgNP-exposed seedlings, respectively. Despite the statistically indistinguishable silver accumulation, RNA sequencing data demonstrated distinct changes in the transcriptome of the AgNP-exposed, but not in the AgNO3-exposed plants. AgNP exposure induced changes in the expression of genes involved in immune response, cell wall organization, photosynthesis and cellular defense against reactive oxygen species. AgNO3 exposure, on the other hand, caused the differential expression of only two genes, neither of which belonged to any AgNP-enriched gene ontology categories. Moreover, AgNP exposure led to a 39% reduction (p < 0.001) in total chlorophyll concentration relative to untreated plants which was associated with a 56.9% and 56.2% drop (p < 0.05) in carbon assimilation rate at ambient and saturating light, respectively. Stomatal conductance was not significantly affected by AgNP exposure, and limitations to carbon assimilation, as determined through analysis of light and carbon dioxide (A/Ci) curves, were attributed to rates of electron transport, maximum carboxylation rates and triose phosphate use. AgNO3-exposure, on the other hand, did not lead to significant reduction either in chlorophyll concentration or in carbon assimilation rate. Given these data, we propose that the impact of AgNPs cannot be simply attributed to the presence of the metal in plants, but is innate to the particulate nature of nanosilver.

Toxicological and morphological aspects of nano-TiO2 and nano-TiO2-Ag acute action on the liver of mice

Aim. To study the toxic effect of TiO2 and TiO2-Ag nanopowders on the morphology and elemental composition of the laboratory mice liver. Materials and methods. The study used a model of acute intoxication on laboratory animals. Mice were injected intraperitoneally with TiO2 and TiO2-Ag nanopowders at 4000 mg/kg, 7000 mg/kg, or 10000 mg/kg doses. During two weeks, the animals were observed, lethality was assessed, the accumulation of nanopowder in the organ and the morphology of liver tissues were investigated. The content of titanium and silver in liver samples was determined by optical emission spectroscopy with inductively coupled plasma. Liver tissue micropreparations were examined using an Olympus BX51 light microscope. Also, the micropreparations of the liver were examined by scanning electron microscopy (SEM) using the Tescan Mira 3 device, and the elemental composition was determined using an energy dispersive spectrometer Oxford instrument, X-max 80 mm2. Results. The dependence of the mice lethality on the nanopowders dose was revealed; mortality was higher when exposed to nano-TiO2-Ag compared to nano-TiO2. Average lethal doses were calculated using probit analysis. For nano-TiO2, the LD50 is 4783.30 mg/kg; for nano-TiO2-Ag – 724.44 mg/kg. The accumulation of titanium, titanium, and silver in the liver after exposure to nano-TiO2 and nano-TiO2-Ag was established. In general, there was a tendency to increase the content of titanium in the skin tissue with an increase in the administered dose of nanopowders. Morphological changes in the liver were studied by histological methods. The most characteristic morphological signs of the toxic effect of nano-TiO2 on tissue were dystrophic changes at the level of 67.7 % (cytoplasmic vacuolization in hepatocytes), and when exposed to nano-TiO2-Ag – initial necrotic changes at the level of 70 % (hepatocytes with nuclear pyknosis). It is worth noting that the toxic effect of nano-TiO2 and nano-TiO2-Ag is much less often manifested by focal necrosis and inflammatory reactions (focal infiltration), in some cases, there were adaptive changes that provoked an increase in the number of binuclear hepatocytes. In case of detection agglomerates of a foreign object (crystalline inclusions) were obtained, which were examined spectrally and showed a high content of titanium (Ti). SEM morphometry showed that the size of nanoparticles and their agglomerates ranged from 80 nm to 20 μm. Conclusions. The lethality of mice was higher when the composition of nano-TiO2-Ag was introduced compared to nano-TiO2. Based on the calculated average lethal doses, both nanopowders were assigned to the 3rd class (moderately dangerous) of the danger of chemical substances according to the classification of GOST 12.1.007-76. It was established that with an increase in the injected dose in the tissue of the products of laboratory mice, the accumulation of titanium (under the action of nano-TiO2) and titanium and silver (under the action of nano-TiO2-Ag) increases. Characteristic microscopic signs of the toxic effect of TiO2 and TiO2-Ag nanopowders after intraperitoneal injection in laboratory bags are dystrophic changes in hepatocytes, necrosis of parenchymal disease, while inflammatory reactions occur less often. SEM and the method of elemental mapping of titanium confirmed the presence of TiO2 nanoparticles and their agglomerates in skin tissue when TiO2 nanopowder was administered.

Nanoscale sulfur alleviates silver nanoparticle toxicity and improves seed and oil yield in Soybean (Glycine max)

Silver nanoparticles (AgNPs) are commonly used in many commercial products due to their antimicrobial properties, and their significant exposure in agricultural systems is anticipated. AgNPs accumulation in soil and subsequent uptake by plants can be harmful to plant growth and exposure to animals and humans through the food chain is a major concern. This study evaluated the potential protective role of nanosulfur (NS) and bulk sulfur (BS) at 200 and 400 mg/kg soil application in alleviating silver nanoparticle (AgNPs; 32 and 64 mg/kg) phytotoxicity to soybean [Glycine max (L) Merr.]. The treatments were added in the soil before soybean transplantation; growth, yield, nutrient, and silver accumulation were measured in the shoot, root, and seeds. Exposure to AgNPs significantly affected plant growth and yield, reducing nodule weight by 40%, fresh shoot weight by 66%, and seed yield by 68% when compared to controls. However, nanosulfur application in soil alleviated AgNPs toxicity, and importantly, this impact was nanoscale specific at the higher concentration because the benefits of corresponding bulk sulfur (BS) treatments were marginal. Specifically, nanosulfur at 400 mg/kg significantly increased seed yield (∼3-fold more than AgNP at 64 mg/kg) and shoot biomass (2.6-fold more than AgNP at 64 mg/kg) upon co-exposure with AgNPs, essentially alleviating AgNPs toxicity. Moreover, NS increased nodule mass by 3.5 times compared to AgNPs-treated plants, which was 170% greater than the Ag- and NS-free controls. Plants treated with NS with AgNPs co-exposure accumulated significantly less Ag in the shoots (∼80% reduction) and roots (∼95% reduction); no Ag contents were detected in seeds. These findings demonstrate the potential of sulfur, especially NS, as a sustainable soil amendment to reduce the accumulation and toxicity of AgNPs and as a valuable nano-enabled strategy to promote food safety and security.

Hydrogel-Containing Biogenic Silver Nanoparticles: Antibacterial Action, Evaluation of Wound Healing, and Bioaccumulation in Wistar Rats.

Wound infections are feared complications due to their potential to increase healthcare costs and cause mortality since multidrug-resistant bacteria reduce treatment options. This study reports the development of a carbomer hydrogel containing biogenic silver nanoparticles (bioAgNPs) and its effectiveness in wound treatment. This hydrogel showed in vitro bactericidal activity after 2 h, according to the time-kill assay. It also reduced bacterial contamination in rat wounds without impairing their healing since the hydrogel hydrophilic groups provided hydration for the injured skin. The high number of inflammatory cells in the first days of the skin lesion and the greater degree of neovascularization one week after wound onset showed that the healing process occurred normally. Furthermore, the hydrogel-containing bioAgNPs did not cause toxic silver accumulation in the organs and blood of the rats. This study developed a bioAgNP hydrogel for the treatment of wounds; it has a potent antimicrobial action without interfering with cicatrization or causing silver bioaccumulation. This formulation is effective against bacteria that commonly cause wound infections, such as Pseudomonas aeruginosa and Staphylococcus aureus, and for which new antimicrobials are urgently needed, according to the World Health Organization's warning.

Toxicity assessment of poultry-waste biosynthesized nanosilver in Anabas testudineus (Bloch, 1792) for responsible and sustainable aquaculture development-A multi-biomarker approach

The current study investigates the potential utilization of poultry intestines for the synthesis of stable silver nanoparticles (AgNPs) and their impact on fish physiology. The AgNPs were synthesized and characterized using various analytical techniques. The toxicity of AgNPs on Anabas testudineus was evaluated, determining a 96-h LC50 value of 25.46 mg l−1. Subsequently, fish were exposed to concentrations corresponding to 1/10th, 1/25th, 1/50th, and 1/100th of the estimated LC50 for a duration of 60 days in a sub-acute study. A comprehensive range of biomarkers, including haematological, serum, oxidative stress, and metabolizing markers, were analyzed to assess the physiological responses of the fish. Additionally, histopathological examinations were conducted, and the accumulation of silver in biomarker organs was measured. The results indicate that silver tends to bioaccumulate in all biomarker organs in a dose- and time-dependent manner, except for the muscle tissue, where accumulation initially increased and subsequently decreased, demonstrating the fish's inherent ability for natural attenuation. Analysis of physiological data and integrated biomarker responses reveal that concentrations of 1/10th, 1/25th, and 1/50th of the LC50 can induce stress in the fish, while exposure to 1/100th of the LC50 shows minimal to no stress response. Overall, this study provides valuable insights into the toxicity and physiological responses of fish exposed to poultry waste biosynthesized AgNPs, offering potential applications in aquaculture while harnessing their unique features.

The Occurrence of Oxidative Stress Induced by Silver Nanoparticles in Chlorella vulgaris Depends on the Surface-Stabilizing Agent.

Silver nanoparticles (AgNPs) are of great interest due to their antimicrobial properties, but their reactivity and toxicity pose a significant risk to aquatic ecosystems. In biological systems, AgNPs tend to aggregate and dissolve, so they are often stabilized by agents that affect their physicochemical properties. In this study, microalga Chlorella vulgaris was used as a model organism to evaluate the effects of AgNPs in aquatic habitats. Algae were exposed to AgNPs stabilized with citrate and cetyltrimethylammonium bromide (CTAB) agents and to AgNO3 at concentrations that allowed 75% cell survival after 72 h. To investigate algal response, silver accumulation, ROS content, damage to biomolecules (lipids, proteins, and DNA), activity of antioxidant enzymes (APX, PPX, CAT, SOD), content of non-enzymatic antioxidants (proline and GSH), and changes in ultrastructure were analyzed. The results showed that all treatments induced oxidative stress and adversely affected algal cells. AgNO3 resulted in the fastest death of algae compared to both AgNPs, but the extent of oxidative damage and antioxidant enzymatic defense was similar to AgNP-citrate. Furthermore, AgNP-CTAB showed the least toxic effect and caused the least oxidative damage. These results highlight the importance of surface-stabilizing agents in determining the phytotoxicity of AgNPs and the underlying mechanisms affecting aquatic organisms.

Nutritional and ameliorative effects of dietary curcumin and its nano-silica and nano-zeolite encapsulated forms on growth, biochemical and fatty acid profile of common carp (Cyprinus carpio).

The present study aimed to examine individual nutritional and ameliorative effects of silica nanoparticles (SiO2NPs) and natural zeolite nanoparticles (ZeNPs) and their potential role as carriers to alter the bioavailability of curcumin. Common carps (Cyprinus carpio) were fed during 60 days with a control diet, and curcumin, turmeric, SiO2NPs, curcumin-loaded SiO2NPs, ZeNPs, and curcumin-loaded ZeNPs each at 1, 50, 6.15, 7.15, 39, and 40 g/kg diet, respectively. The highest weight gain (WG) and specific growth rate (SGR) were observed in fish fed with turmeric (P < 0.05). Moreover, dietary curcumin and ZeNPs increased the content of monounsaturated fatty acids (P < 0.05). After exposure to silver nanoparticles (AgNPs), the lowest amount of aspartate aminotransferase (AST) was obtained in fish fed with curcumin (P < 0.05). In addition, alanine aminotransferase (ALT) decreased significantly in the negative control, curcumin, and curcumin-loaded SiO2NPs treatments in comparison to the positive control group (P < 0.05). The lowest silver accumulation was observed in the negative control and SiO2NPs groups (P < 0.05). This experiment demonstrated that while the nanoencapsulation of curcumin on SiO2NPs and ZeNPs did not enhanced the impact of curcumin on the growth and biochemical factors of carps, it can still be considered a potential dietary supplement for enhancing growth and antioxidant indices when added individually to the diet.

Geochemical Distribution of Platinum Metals, Gold and Silver in Intrusive Rocks of the Norilsk Region

The Norilsk ore district is one of the world leaders in the production of platinum metals. Long-term research focused on the detection of sulfide platinum-copper-nickel ores contributed to the accumulation of a large volume of scientific material on the geology and mineralization of the Norilsk area. Despite this, the issue of the composition of the initial melt for ore-bearing intrusive complexes and its degree of enrichment with noble metals remains open. Intrusive rocks of the Norilsk region are rarely analyzed for their ratio of noble metals. However, the analysis and comparison of geochemical parameters of different types of intrusions allows us to draw important conclusions not only about the composition of the initial magmas of ore-bearing complexes, but also about the formation conditions of the intrusions. This study demonstrates the distribution of platinum metals, gold and silver in the main petrographic differentiates of the Kharaelakh, Talnakh, Vologochan intrusions and Kruglogorsk-type intrusion. The regularities and variations of the distribution of metals depend on the host rocks. There are two series of rocks in the inner structure of the ore-bearing intrusions: 1. Picritic and taxitic gabbro-dolerites enriched in PGE-Au-Ag mineralization which forms disseminated ores at intrusion bottoms (ore-bearing rocks). 2. Olivine-, olivine-bearing, olivine-free gabbro-dolerites and leucogabbro with poor sulfide mineralization at the upper part of the intrusions (ore-free rocks). There is a distinct correlation between PGE, Cu, S and to a lesser extent correlation with Ni in the first rock group, which is a characteristic of sulfide PGE-Cu-Ni deposits. In the second group, correlations are also revealed, but the correlation coefficients are lower. The main element controlling the distribution of platinum metals is copper. The taxitic gabbro-dolerites of the Talnakh intrusion are the most enriched by noble metals. According to noble metal patterns the rocks of the Kharaelakh intrusion show the highest degree of melting of the initial mantle material during the formation of parental magmas chambers. Despite some differences, the geochemical features of the studied rocks indicate the similar characteristics of the accumulation of gold, silver and platinum metals in the intrusions of the Talnakh, Kruglogorsk and Zubovsk types, which allow suggesting the close conditions for the formation of ore mineralization of these intrusions.

PROMISING NANOBIOTECHNOLOGY FOR POULTRY FARMING BASED ON SILVER NANOPARTICLES EMBEDDED IN POLYMER-INORGANIC HYBRID CARRIERS

A promising composite material is proposed to reduce the endogenous and exogenous contamination of chicken eggs with pathogenic microflora during their formation and storage. It is based on hybrid biocompatible and biodegradable silica/polyacrylamide nanocarriers containing small silver nanoparticles (dav=2.4±1.0 nm) that are orally administered to laying hens with drinking water. The features of the formation of nanosilver in hybrid carriers by borohydride reduction of a silver salt at its various concentrations in an aqueous solution have been studied. An interesting effect of the sharp appearance of the second surface plasmon resonance band in the UV-Vis spectra of a silver salt/hybrid mixture at a high salt concentration was found. This was explained by sharp structural changes in the hybrid carriers caused by the simultaneous growth of many AgNPs in them. It was assumed that the intensive growth of many AgNPs in one hybrid particle was accompanied by detachment of the grafted PAAm chains from the SiO2 surface due to the breaking of hydrogen bonds. The change in the state of the composite material under the influence of the pH of the solution, the concentration of nanoparticles, the presence of NaCl (as in a “physiological solution”), and visible light was studied by UV-Vis spectroscopy, potentiometric titration, and TEM. Nanosilver in carriers showed high stability with respect to most of these factors. The influence of the composite material on the clinical state of laying hens and important parameters of their eggs and blood was studied when it was administered orally with drinking water three times every 10 days at doses of 0.2 and 0.4 mg per chicken per day. A striking effect of selective endogenous accumulation of silver in eggshells has been revealed. This confirmed the penetration of the nanosilver composite into the circulatory system of chickens by passing through the digestive tract, absorption through the intestinal epithelium and further transport into the tissues of the chickens, including the oviducts, where protein and eggshell are formed. Such penetration did not cause a toxic effect on the body of laying hens.

Distribution of Silver (Ag) and Silver Nanoparticles (AgNPs) in Aquatic Environment

Nanomaterials, classified as emerging pollutants that are toxic to the environment, are known to bioaccumulate across different trophic levels in the aquatic ecosystem. This study therefore investigates the distribution of silver and silver nanoparticles (AgNPs) in the aquatic environment of Skudai River, Johor, Malaysia. Water, sediment, plant, and fish samples were collected seasonally along four sites along Skudai River between May 2018 and April 2019. All samples were subjected to Ag analysis using an inductively coupled plasma mass spectrometer (ICP-MS). The analysis demonstrated that the concentration of Ag detected in water samples ranging from 0.001 to 0.505 mg/L was the lowest, whereas in the plants, 0.235 to 4.713 mg/kg of Ag was quantified. The upper sediments contained 0.036 to 28.115 mg/kg of Ag, whilst fish samples presented the highest accumulation of Ag, averaging between 9.144 and 53.784 mg/kg of Ag. Subsequently, the formation of silver nanoparticles was further proven by TEM-EDX analysis, where the detected size of AgNPs ranged from 20 nm to 35 nm. The overriding conclusion implied by bioaccumulation factor (BAF) and biota–sediment accumulation factor (BSAF) calculations suggested that Skudai River was indeed polluted by Ag and AgNPs. The values obtained stipulated that silver accumulation is occurring at an alarming rate and could therefore endanger fish consumers.

Metabolomics reveals size-dependent persistence and reversibility of silver nanoparticles toxicity in freshwater algae

Although the toxicity of silver nanoparticles (AgNPs) has been widely reported, the persistence and reversibility of AgNPs toxicity are poorly understood. In the present work, AgNPs with particle sizes of 5 nm, 20 nm, and 70 nm (AgNPs5, AgNPs20, and AgNPs70) were selected to investigate the nanotoxicity and recovery effects of Chlorella vulgaris in the exposure (72 h) and recovery (72 h) stages using non-targeted metabolomics techniques. The exposure of AgNPs exerted size-dependent effects on several aspects of C. vulgaris physiology, including growth inhibition, chlorophyll content, intracellular silver accumulation, and differential expression of metabolites, and most of these adverse effects were reversible. Metabolomics revealed that AgNPs with small sizes (AgNPs5 and AgNPs20) mainly inhibited glycerophospholipid and purine metabolism, and the effects were reversible. In contrast, AgNPs with large sizes (AgNPs70) reduced amino acid metabolism and protein synthesis by inhibiting aminoacyl-tRNA biosynthesis, and the effects were irreversible, demonstrating the persistence of nanotoxicity of AgNPs. The size-dependent persistence and reversibility of AgNPs toxicity provides new insights to further understand the mechanisms of toxicity of nanomaterials.

Osteoconductivity and neurotoxicity of silver-containing hydroxyapatite coating cage for spinal interbody fusion in rats.

The use of spinal instrumentation is an established risk factor for postoperative infection. To address this problem, we prepared silver-containing hydroxyapatite coating, consisting of highly osteoconductive hydroxyapatite interfused with silver. The technology has been adopted for total hip arthroplasty. Silver-containing hydroxyapatite coating has been reported to have good biocompatibility and low toxicity. However, no studies about applying this coating in spinal surgery have addressed the osteoconductivity and direct neurotoxicity to the spinal cord of silver-containing hydroxyapatite cages in spinal interbody fusion. In this study, we evaluated the osteoconductivity and neurotoxicity of silver-containing hydroxyapatite-coated implants in rats. Titanium (non-coated, hydroxyapatite-coated, and silver-containing hydroxyapatite-coated) interbody cages were inserted into the spine for anterior lumbar fusion. At 8 weeks postoperatively, micro-computed tomography and histology were performed to evaluate the osteoconductivity of the cage. Inclined plane test and toe pinch test were performed postoperatively to assess neurotoxicity. Micro-computed tomography data indicated no significant difference in bone volume/total volume among the three groups. Histologically, the hydroxyapatite-coated and silver-containing hydroxyapatite-coated groups showed significantly higher bone contact rate than that of the titanium group. In contrast, there was no significant difference in bone formation rate among the three groups. Data of inclined plane and toe pinch test showed no significant loss of motor and sensory function in the three groups. Furthermore, there was no degeneration, necrosis, or accumulation of silver in the spinal cord on histology. This study suggests that silver-hydroxyapatite-coated interbody cages produce good osteoconductivity and are not associated with direct neurotoxicity.

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

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.

Comparative toxicity of silver nanoparticles and silver nitrate in freshwater fish Oreochromis mossambicus: A multi-biomarker approach

Silver nanoparticles (AgNPs) in the aquatic environment affect ecological repercussions and have fatal impacts on aquatic animals. The current study examined and correlated the toxicity of silver nitrate (AgNO3) and silver nanoparticles (AgNPs) to the Mozambique tilapia, Oreochromis mossambicus. The comparative toxicity studies were done by exposing O. mossambicus to various doses of AgNO3 and AgNPs (0, 25, 50, 75, and 100 μg/L) over a 7-day subacute exposure period. AAS analysis was used to detect Ag accumulation, while the histological examination established gill tissue damage. Oxidative stress affects lipid peroxidation (LPO) and protein carbonyl activity (PCA) in the gill tissue. Antioxidant parameters such as glutathione-S-transferase (GST), glutathione peroxidase (GPx), superoxide dismutase (SOD), catalase activity (CAT), and non-enzymatic antioxidants such as metallothionein (MT) and reduced glutathione. The serum in the blood was used to determine non-specific immunological characteristics such as lysozyme (LYZ), myeloperoxidase (MPO), and respiratory burst activity (RBA). The neurotoxic impact of acetylcholine esterase activity (AChE) was investigated in brain tissues. The findings demonstrated that larger concentrations of AgNO3 than AgNPs improved enzymatic antioxidant activities in the gill tissue. Histological examination of fish gills demonstrated that both AgNPs and AgNO3 induced telangiectasia and epithelial cell hyperplasia. By increasing the concentration of AgNPs and AgNO3, the present research demonstrated that silver accumulation leads to inefficient oxidative stress and altered enzymatic and non-enzymatic parameters, leading to cellular damage.