Transcriptional regulation of metal metabolism- and nutrient absorption-related genes in Eucalyptus grandis by arbuscular mycorrhizal fungi at different zinc concentrations

BACKGROUND

Eucalyptus spp. are candidates for phytoremediation in heavy metal (HM)-polluted soils as they can adapt to harsh environments, grow rapidly, and have good economic value. Arbuscular mycorrhizal fungi (AMF) are the most widely distributed plant symbiotic fungi in nature, and they play an important role in promoting the phytoremediation of HM-polluted soils. However, few studies have evaluated the HM detoxification mechanism of E. spp. in symbiosis with AMF, and thus, the molecular mechanism remains unclear.

RESULTS

The gene transcription and metabolic pathways of E. grandis were studied with and without inoculation with AMF and at different zinc (Zn) concentrations. Here, we focused on the transcript level of six HM-related gene families (ZNT, COPT/Ctr, YSL, ZIFL and CE). Under high-Zn conditions, thirteen genes (ZNT:2, COPT/Ctr:5, YSL:3, ZIFL:1, CE:2) were upregulated, whereas ten genes (ZNT:3, COPT/Ctr:2, YSL:3, ZIFL:1, CE:1) were downregulated. With AMF symbiosis under high-Zn conditions, ten genes (ZNT:4, COPT/Ctr:2, YSL:3, CE:1) were upregulated, whereas nineteen genes (ZNT:9, COPT/Ctr:2, YSL:3, ZIFL:4, CE:1) were downregulated. Under high-Zn conditions, genes of three potassium-related transporters, six phosphate transporters (PHTs), and two nitrate transporters (NRTs) were upregulated, whereas genes of four potassium-related transporters,four PHTs, and four nitrogen-related transporters were downregulated. With AMF symbiosis under high-Zn conditions, genes of two potassium-related transporters, six ammonium transporters (AMTs) and five PHTs were upregulated, whereas genes of six potassium-related transporters, two AMTs and five PHTs were downregulated.

CONCLUSIONS

Our results indicates that AMF increases the resistance of E. grandis to high-Zn stress by improving nutrients uptake and regulating Zn uptake at the gene transcription level. Meanwhile, our findings provide a genome-level resource for the functional assignments of key genes regulated by Zn treatment and AM symbiosis in six HM-associated gene families and macromineral nutrient-related gene families of E. grandis. This may contribute to the elucidation of the molecular mechanisms of the response to Zn stress in E. grandis with AM symbiosis at the aspect of the interaction between HM tolerance and nutrient acquisition.

A Complex Evaluation of the In-Vivo Biocompatibility and Degradation of an Extruded ZnMgSr Absorbable Alloy Implanted into Rabbit Bones for 360 Days

The increasing incidence of trauma in medicine brings with it new demands on the materials used for the surgical treatment of bone fractures. Titanium, its alloys, and steel are used worldwide in the treatment of skeletal injuries. These metallic materials, although inert, are often removed after the injured bone has healed. The second-stage procedure—the removal of the plates and screws—can overwhelm patients and overload healthcare systems. The development of suitable absorbable metallic materials would help us to overcome these issues. In this experimental study, we analyzed an extruded Zn-0.8Mg-0.2Sr (wt.%) alloy on a rabbit model. From this alloy we developed screws which were implanted into the rabbit tibia. After 120, 240, and 360 days, we tested the toxicity at the site of implantation and also within the vital organs: the liver, kidneys, and brain. The results were compared with a control group, implanted with a Ti-based screw and sacrificed after 360 days. The samples were analyzed using X-ray, micro-CT, and a scanning electron microscope. Chemical analysis revealed only small concentrations of zinc, strontium, and magnesium in the liver, kidneys, and brain. Histologically, the alloy was verified to possess very good biocompatibility after 360 days, without any signs of toxicity at the site of implantation. We did not observe raised levels of Sr, Zn, or Mg in any of the vital organs when compared with the Ti group at 360 days. The material was found to slowly degrade in vivo, forming solid corrosion products on its surface.

Influence of Dairy Products on Bioavailability of Zinc from Other Food Products: A Review of Complementarity at a Meal Level

In this paper, we reviewed the role of dairy products in dietary zinc absorption. Dairy products can have a reasonable contribution for dietary zinc intake in Western diets, where dairy consumption is high. However, the co-ingestion of dairy products can also improve zinc absorption from other food products. Such improvements have been observed when dairy products (e.g., milk or yoghurt) were ingested together with food such as rice, tortillas or bread products, all of which are considered to be high-phytate foods with low inherent zinc absorption. For foods low in phytate, the co-ingestion of dairy products did not improve zinc absorption. Improved zinc absorption of zinc from high-phytate foods following co-ingestion with dairy products may be related to the beneficial effects of the citrate and phosphopeptides present in dairy products. Considering that the main dietary zinc sources in areas in the world where zinc deficiency is most prevalent are typically high in phytate, the inclusion of dairy products in meals may be a viable dietary strategy to improve zinc absorption.

Nutritive Manganese and Zinc Overdosing in Aging C. elegans Result in a Metallothionein-Mediated Alteration in Metal Homeostasis

SCOPE

Manganese (Mn) and zinc (Zn) are not only essential trace elements, but also potential exogenous risk factors for various diseases. Since the disturbed homeostasis of single metals can result in detrimental health effects, concerns have emerged regarding the consequences of excessive exposures to multiple metals, either via nutritional supplementation or parenteral nutrition. This study focuses on Mn-Zn-interactions in the nematode Caenorhabditis elegans (C. elegans) model, taking into account aspects related to aging and age-dependent neurodegeneration.

METHODS AND RESULTS

Chronic co-exposure of C. elegans to Mn and Zn increases metal uptake, exceeding levels of single metal exposures. Supplementation with Mn and/or Zn also leads to an age-dependent increase in metal content, a decline in overall mRNA expression, and metal co-supplementation induced expression of target genes involved in Mn and Zn homeostasis, in particular metallothionein 1 (mtl-1). Studies in transgenic worms reveal that mtl-1 played a prominent role in mediating age- and diet-dependent alterations in metal homeostasis. Metal dyshomeostasis is further induced in parkin-deficient nematodes (Parkinson's disease (PD) model), but this did not accelerate the age-dependent dopaminergic neurodegeneration.

CONCLUSIONS

A nutritive overdose of Mn and Zn can alter interactions between essential metals in an aging organism, and metallothionein 1 acts as a potential protective modulator in regulating homeostasis.

A transporter for delivering zinc to the developing tiller bud and panicle in rice

Tiller number is one of the most important agronomic traits that determine rice (Oryza sativa) yield. Active growth of tiller bud (TB) requires high amount of mineral nutrients; however, the mechanism underlying the distribution of mineral nutrients to TB with low transpiration is unknown. Here, we found that the distribution of Zn to TB is mediated by OsZIP4, one of the ZIP (ZRT, IRT-like protein) family members. The expression of OsZIP4 was highly detected in TB and nodes, and was induced by Zn deficiency. Immunostaining analysis revealed that OsZIP4 was mainly expressed in phloem of diffuse vascular bundles in the nodes and the axillary meristem. The mutation of OsZIP4 did not affect the total Zn uptake, but altered Zn distribution; less Zn was delivered to TB and new leaf, but more Zn was retained in the basal stems at the vegetative growth stage. Bioimaging analysis showed that the mutant aberrantly accumulated Zn in enlarged and transit vascular bundles of the basal node, whereas in wild-type high accumulation of Zn was observed in the meristem part. At the reproductive stage, mutation of OsZIP4 resulted in delayed panicle development, which is associated with decreased Zn distribution to the panicles. Collectively, OsZIP4 is involved in transporting Zn to the phloem of diffuse vascular bundles in the nodes for subsequent distribution to TBs and other developing tissues. It also plays a role in transporting Zn to meristem cells in the TBs.

Role of metal speciation in the exposure medium on the toxicity, bioavailability and bio-reactivity of copper, silver, cadmium and zinc in the rainbow trout gut cell line (RTgutGC)

The role of metal speciation on metal bioavailability, bio-reactivity and toxicity at the fish intestine is poorly understood. To investigate these processes, we used an in vitro model of the rainbow trout (Oncorhynchus mykiss) intestine, the RTgutGC cell line. Cells were exposed to two essential metals (copper and zinc) and two non-essential metals (cadmium and silver) in a medium of well-defined composition, which allowed the determination of metal speciation in solution. Concentrations resulting in a 50% cell viability reduction (EC₅₀) were measured using a viability assay based on two endpoints: metabolic activity and membrane integrity. Metal bioavailability and bio-reactivity was studied at non-toxic (300 nM all metals) and toxic (EC₁₀; Ag-0.6, Cu-0.9, Cd-3, and Zn-9 μM) concentrations. Bioavailability (i.e. intracellular metal accumulation) was determined by ICP-MS, while bio-reactivity (i.e. induction of a metal specific transcriptional response) was determined by measuring the mRNA levels of a known biomarker of metal exposure (i.e. metallothionein) and of copper and zinc transporters (i.e. ATP7A and ZnT1). Dominant metal species in the exposure medium were Zn²⁺, CuHPO₄, CdCl⁺, and AgCl₂^- respectively for Zn, Cu, Cd, and Ag. The EC_50s showed the metal toxicity hierarchy: Ag > Cu > Cd > Zn. In RTgutGC cells, essential metal homeostasis was tightly regulated while non-essential metals accumulated more readily. Non-essential metals were also more bio-reactive inducing higher MT and ZnT1 mRNA levels. Taken together these findings indicate that metal toxicity in RTgutGC cannot solely be explained by extracellular metal speciation but requires the evaluation of metal bioavailability and bio-reactivity.

Heavy metal capture from the suspended particulate matter by Morus alba and evidence of foliar uptake and translocation of PM associated zinc using radiotracer (65Zn)

In urban set up, increasing combustion and processing activities have contaminated the air with toxic heavy metals which are generally enriched on atmospheric particulate matter. Vegetation around urban area act as a sink where such metal enriched particles generally deposit on the foliar surfaces, however, role of vegetation in uptake of metals adhered on the atmospheric particulate matter is yet not explored properly and is important to study to evaluate their role as bio-remediator. The undertaken work examines the foliar surface of Morus alba for its potential to deposit and accumulate atmospheric heavy metals. Further, to understand foliar uptake mechanism and translocation of atmospheric metal enriched on particulate matter a simulated experiment was conducted by labeling the known particle size (45 μm and 120 μm) with radio labeled ⁶⁵Zn, applied on the tagged leaf with two particle loads, 25 mg and 50 mg. The study showed that owing to its rough foliar surface with trichomes and grooves, Morus alba efficiently trap heavy metal enriched particles and was capable of accumulating metals from particulate matter into different plant parts. It was recorded that ⁶⁵Zn adhered on different size particles was taken up by tagged leaf of mulberry and majorly translocated to the lower stem and roots. It was also inferred from the study that both particle size and particle load significantly affect the foliar uptake and translocation of atmospheric heavy metal. The study focuses on the fact that urban avenue trees are capable of taking up atmospheric heavy metals and can play a crucial role in improving air quality.

Biochar effect on crop performance and Pb and Zn uptake of tomato (Solanum lycopersicum, L.) plants grown on heavy metals contaminated Kosovo soils

A greenhouse pot experiment was conducted to evaluate the effect of biochar on the growth and uptake of Pb and Zn by tomato plants (Solanum lycopersicum, L.) cultivated in two highly contaminated Kosovo soils, A and B. Plants were cultivated in the biochar amended and unamended soils. As expected, the biochar addition to the two polluted soils has contributed to significantly improve the crop yields, in terms of both fresh and dry weight. Further, results indicated that the effect of biochar on metal mobility is closely related, besides its properties, to soil's native characteristics. In fact, the addition of biochar to soil B had also beneficial effects on the uptake of both metals, halving in some cases the values of the biological accumulation and transfer coefficients, while it did not show the same efficacy on soil A.

Effects of sodium sulfide application on the growth of Robinia pseudoacacia, heavy metal immobilization, and soil microbial activity in Pb-Zn polluted soil

Sodium sulfide (Na₂S) is usually used as an amendment in industrial sewage treatment. To evaluate the effects of Na₂S on the growth of Robinia pseudoacacia (black locust), heavy metal immobilization, and soil microbial activity, the R. pseudoacacia biomass and nutrient content and the soil heavy metal bioavailability, enzyme activity, and arbuscular mycorrhizal (AM) fungal community were measured by a single-factor pot experiment. The Pb-Zn-contaminated soil was collected from a Pb-Zn mine that had been remediated by R. pseudoacacia for five years. Three pollution levels (unpolluted, mildly polluted, and severely polluted) were evaluated by the pollution load index. Na₂S application increased the shoot biomass under severe and mild contamination. In soil, Na₂S application decreased the bioavailable Pb and Zn contents under severe and mild contamination, which resulted in a decrease in the Pb and Zn content in R. pseudoacacia. However, Na₂S application did not affect the total Pb content per plant and enhanced the total Zn content per plant because of the higher biomass of the plants under Na₂S application. Increased phosphatase activity and increased available phosphorous content may promote the uptake of phosphorus in R. pseudoacacia. Moreover, Na₂S application is beneficial to the diversity of AM fungi under mild and severe pollution. Overall, Na₂S application has great potential for enhancing soil heavy metal immobilization, enhancing soil microbial activity, and improving the growth of R. pseudoacacia in polluted soils. Therefore, Na₂S is suitable for use in Pb-Zn remediation to ameliorate environmental heavy metal pollution.

Zinc status and its requirement by rural adults consuming wheat from control or zinc-treated fields

Human zinc (Zn) deficiency is prevalent in areas where cereals dominate in the diet. Soil Zn application may enhance the concentration of Zn in wheat grains and dietary Zn intake by target populations. However, its value has never been practically quantified in Zn nutrition of any population group. We, therefore, studied farming families in rural Punjab (Pakistan). The selected adults (n = 156, grouped based on age and gender) were Zn undernourished (as assessed by estimated Zn bioavailability in their diet) and their plasma Zn levels also indicated Zn deficiency. On average, wheat consumption by the adults contributed about 68% in total Zn and 93% in total phytate intakes. Soil Zn application to wheat fields significantly increased Zn and decreased phytate concentration in chapati (flatbread made of whole-wheat flour). From dietary phytate intakes by the adults, we calculated desired chapati Zn concentration and dietary Zn intake that would meet their daily Zn requirement. The physiological Zn requirements of adult women and men were estimated to be achieved by intake of, respectively, 10.4-15.3 mg Zn d^-1 (37-46 mg Zn kg^-1 in chapati) and 14.4-23.3 mg Zn d^-1 (41-52 mg Zn kg^-1 in chapati). It was evident that soil Zn application aiming at optimum grain yield of wheat significantly improved Zn nutrition of the studied adults, but not up to desired levels. High Zn applications (via soil and/or foliage) to wheat and growing cultivars specifically selected for Zn biofortification may be needed to optimise Zn nutrition in rural Pakistan.

Nickel and zinc complexes of testosterone N4-substituted thiosemicarbazone: Selective cytotoxicity towards human colorectal carcinoma cell line HCT 116 and their cell death mechanisms

Two new Schiff base ligands (TE and TF) were prepared from conjugation of testosterone with 4-(4-ethylphenyl)-3-thiosemicarbazide and 4-(4-fluorophenyl)-3-thiosemicarbazide, respectively. Their nickel (NE and NF) and zinc (ZE and ZF) complexes were reported. X-ray crystallography revealed a distorted square planar geometry was adopted by NE. The compounds demonstrated excellent selectivity towards the colorectal carcinoma cell line HCT 116 despite their weak preferences towards the prostate cancer cell lines (PC-3 and LNCaP). Against HCT 116, all these compounds were able to arrest cell cycle at G₀/G₁ phase and induce apoptosis via mitochondria-dependent (TE, NE, and TF) and extrinsic apoptotic pathway (ZE, NF, and ZF). Moreover, only ZE was able to act as topoisomease I poison and halt its enzymatic reactions although all compounds presented excellent affinity towards DNA.

Ecological risk of copper and zinc and their different bioavailability change in soil-rice system as affected by biowaste application

A large amount of organic fertilizer application could be accompanied by soil contamination caused by trace heavy metals. A field experiment was carried out in this study to examine the accumulation and availability of copper (Cu) and zinc (Zn) in soil, and their uptake by rice under continuous application of chicken manure, pig manure and sewage sludge. Results showed that after four years of chicken manure, pig manure and sewage sludge application, the soil Cu accumulation rates were 0.15-1.17 mg kg^-1 yr^-1, 1.01-4.22 mg kg^-1 yr^-1 and 0.13-1.15 mg kg^-1 yr^-1, respectively; Zn accumulation rates were 0.54-5.46 mg kg^-1 yr^-1, 1.51-9.65 mg kg^-1 yr^-1 and 1.13-10.47 mg kg^-1 yr^-1, respectively. Compared to the control, the chicken- and pig manure treatments significantly decreased the DTPA-extractable Cu, but increased the DTPA-extractable Zn in soils; thus decreased the Cu contents in rice grain by 2.2-40.6% and increased the grain Zn by 2.6-30.9%, respectively, with increasing application rates and number of years. The addition of sewage sludge significantly increased bioavailability of Zn in soil and its accumulation in rice, while had limited effect on Cu bioavailability. Results suggested that the continuous application of organic fertilizer with elevated Cu and Zn contents at high application rates can induce their accumulation in soil and affect their bioavailability differently.

Zn-Incorporated TiO2 Nanotube Surface Improves Osteogenesis Ability Through Influencing Immunomodulatory Function of Macrophages

PURPOSE

Zinc (Zn), an essential trace element in the body, has stable chemical properties, excellent osteogenic ability and moderate immunomodulatory property. In the present study, a Zn-incorporated TiO2 nanotube (TNT) was fabricated on titanium (Ti) implant material. We aimed to evaluate the influence of nano-scale topography and Zn on behaviors of murine RAW 264.7 macrophages. Moreover, the effects of Zn-incorporated TNT surface-regulated macrophages on the behaviors and osteogenic differentiation of murine MC3T3-E1 osteoblasts were also investigated.

METHODS

TNT coatings were firstly fabricated on a pure Ti surface using anodic oxidation, and then nano-scale Zn particles were incorporated onto TNTs by the hydrothermal method. Surface topography, chemical composition, roughness, hydrophilicity, Zn release pattern and protein adsorption ability of the Zn-incorporated TiO2 nanotube surface were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), surface profiler, contact angle test, Zn release test and protein adsorption test. The cell behaviors and both pro-inflammatory (M1) and pro-regenerative (M2) marker gene and protein levels in macrophages cultured on Zn-incorporated TNTs surfaces with different TNT diameters were detected. The supernatants of macrophages were extracted and preserved as conditioned medium (CM). Furthermore, the behaviors and osteogenic properties of osteoblasts cultured in CM on various surfaces were evaluated.

RESULTS

The release profile of Zn on Zn-incorporated TNT surfaces revealed a controlled release pattern. Macrophages cultured on Zn-incorporated TNT surfaces displayed enhanced gene and protein expression of M2 markers, and M1 markers were moderately inhibited, compared with the LPS group (the inflammation model). When cultured in CM, osteoblasts cultured on Zn-incorporated TNTs showed strengthened cell proliferation, adhesion, osteogenesis-related gene expression, alkaline phosphatase activity and extracellular mineralization, compared with their TNT counterparts and the Ti group.

CONCLUSION

This study suggests that the application of Zn-incorporated TNT surfaces may establish an osteogenic microenvironment and accelerate bone formation. It provided a promising strategy of Ti surface modification for a better applicable prospect.

A Guide to Human Zinc Absorption: General Overview and Recent Advances of In Vitro Intestinal Models

Zinc absorption in the small intestine is one of the main mechanisms regulating the systemic homeostasis of this essential trace element. This review summarizes the key aspects of human zinc homeostasis and distribution. In particular, current knowledge on human intestinal zinc absorption and the influence of diet-derived factors on bioaccessibility and bioavailability as well as intrinsic luminal and basolateral factors with an impact on zinc uptake are discussed. Their investigation is increasingly performed using in vitro cellular intestinal models, which are continually being refined and keep gaining importance for studying zinc uptake and transport via the human intestinal epithelium. The vast majority of these models is based on the human intestinal cell line Caco-2 in combination with other relevant components of the intestinal epithelium, such as mucin-secreting goblet cells and in vitro digestion models, and applying improved compositions of apical and basolateral media to mimic the in vivo situation as closely as possible. Particular emphasis is placed on summarizing previous applications as well as key results of these models, comparing their results to data obtained in humans, and discussing their advantages and limitations.

Differences in uptake and accumulation of copper and zinc by Salix clones under flooded versus non-flooded conditions

The climate-driven flooding poses a challenge for phytoremediation of contaminated soil, and the willow (Salix spp.) is a promising candidate coping with climate change and environmental pollution. In this study, uptake and accumulation of copper (Cu), zinc (Zn) and their bioavailability in the rhizosphere across the Salix clones under flooded versus non-flooded (control) conditions were investigated using a pot experiment. The tested Salix clones grew well without showing any toxic symptoms under non-flooded soil condition; in contrast, the clones showed 100% survival for long-term flooding with the development of hypertrophied lenticels and adventitious roots. There were wide clonal variations in biomass production and accumulation of Cu and Zn under flooded and non-flooded conditions. Flooded treatments dramatically decreased aboveground biomass across the Salix clones to different extents compared to the control. The non-flooded clones exhibited relatively high accumulation capacities of Cu and Zn in aerial parts. However, the flooded clones resulted in more substantial reductions in Cu and Zn accumulation in aerial parts, and most of Cu and Zn were limited in roots. EDTA-extractable Cu and Zn predicted well bioavailability of Cu and Zn to the Salix clones under the current condition. It was concluded that the Salix clones exhibited Cu and Zn phytoextraction traits (non-flooding) or phytostabilization traits (flooding), which provides a valuable insight into phytomanagement of contaminated soils by willows subjected to flooding stress.

Typha latifolia and Thelypteris palustris behavior in a pilot system for the refinement of livestock wastewaters: A case of study

In animal livestock heavy metals are widely used as feed additives to control enteric bacterial infections as well as to enhance the integrity of the immune system. As these metals are only partially adsorbed by animals, the content of heavy metals in manure and wastewaters causes soil and ground water contamination, with Zn²⁺ and Cu²⁺ being the most critical output from pig livestock. Phytoremediation is considered a valid strategy to improve the purity of wastewaters. This work studied the effect of Zn²⁺ and Cu²⁺ on the morphology and protein expression in Thelypteris palustris and Typha latifolia plants, cultured in a wetland pilot system. Despite the absence of macroscopic alterations, remodeling of cell walls and changes in carbohydrate metabolism were observed in the rhizomes of both plants and in leaves of Thelypteris palustris. However, similar modifications seemed to be determined by the alterations of different mechanisms in these plants. These data also suggested that marsh ferns are more sensitive to metals than monocots. Whereas toleration mechanisms seemed to be activated in Typha latifolia, in Thelypteris palustris the observed modifications appeared as slight toxic effects due to metal exposure. This study clearly indicates that both plants could be successfully employed in in situ phytoremediation systems, to remove Cu²⁺ and Zn²⁺ at concentrations that are ten times higher than the legal limits, without affecting plant growth.

Bioaccumulation of heavy metals from wastewater through a Typha latifolia and Thelypteris palustris phytoremediation system

Animal production is a source of heavy metals in livestock wastewater and also a key link in the food chain, with negative impacts on human and animal health. In intensive animal production systems, the most critical elements are zinc and copper. In order to development of innovative non-invasive strategies to reduce the environmental impact of livestock, this study assessed the ability of two plants, Typha latifolia and Thelypteris palustris, to bioaccumulate the heavy metals used in animal nutrition, from wastewater. Four mesocosms (width 2.0 m, length 2.0 m, 695 L of water, 210 kg of soil) were assembled outdoors at the Botanical Garden. Two of them were planted with T. latifolia (TL treated, n = 30; TL control, n = 30) and two with T. palustris (TP treated, n = 60; TP control, n = 60). In T0 a solution of a mineral additive premix (Zn 44.02 mg/L; Cu 8.63 mg/L) was dissolved in the treated mesocosms. At T0, d 15 (T1) and d 45 (T2) samples of roots, leaves, stems, soil and water were collected, dried, mineralized and analyzed using ICP-MS in order to obtain HMs content. We found that T. latifolia and T. palustris accumulate and translocate Zn, Cu from contaminated wastewater into plant tissues in a way that is directly related to the exposure time (T2 for Zn: 271.64 ± 17.70, 409.26 ± 17.70 for Cu: 47.54 ± 3.56, 105.58 ± 3.56 mg/kg of DM, respectively). No visual toxicity signs were observed during the experimental period. This phytoremediation approach could be used as an eco-sustainable approach to counteract the output of heavy metals.

Human intestinal Caco-2 cell line in vitro assay to evaluate the absorption of Cd, Cu, Mn and Zn from urban environmental matrices

The Caco-2 cell line is derived from a human colon adenocarcinoma and is generally used in toxicity assays. The ingestion of soil or dust is a significant route of human exposure to potential harmful elements (PHE), and assays of bioaccessibility or bioavailability can be used to measure the potential hazard posed by exposure to toxic substances. The in vitro digestion (UBM method) and Caco-2 cell model were used to investigate the bioaccessibility and absorption by intestinal cells of the PHE in four matrices (two urban soils and two soils with lead (Pb)-mining tailings) along with the guidance material for bioaccessibility measurements, BGS 102. The gastrointestinal (GI) compartment was simulated, and the resulting material added to Caco-2 cells. In the GI, the average bioaccessibility was 24% for cadmium (Cd), 17% for copper (Cu), 0.2% for Pb, 44% for manganese (Mn) and 6% for zinc (Zn). The poor reproducibility was attributed to the pH (6.3) and the highly complex GI fluid that formed PHE precipitates and complexes. In 2 h, Caco-2 cells absorbed 0.2 ng mg^-1 of cellular protein for Cd, 13.4 ng mg^-1 for Cu, 5 ng mg^-1 for Mn and 31.7 µg mg^-1 for Zn. Lead absorption was lower than the limit of quantification (< 2 µg L^-1). Cd was presented in the cell monolayer and could interfere in the intracellular accumulation of Cu, Mn and Zn. The use of in vitro assays allowed for an estimation of the absorption of Cd, Cu, Mn and Zn from environmental matrices to be made, and except for Mn, it had a positive correlation with bioaccessible concentration, suggesting a common association of these elements in the cellular environment.

Degradation of ZnGa2O4:Cr3+ luminescent nanoparticles in lysosomal-like medium

The ultimate goal of in vivo imaging is to provide safe tools to probe the inside of a body in order to obtain pathological information, monitor activities, and examine disease progression or regression. In this context zinc gallate doped with chromium III (ZGO) nanoparticles with persistent luminescence properties have been previously developed, and their biodistribution as well as in vitro toxicity were evaluated. However, to date, nothing is known about their potential transformations in biological media, which may hinder their biomedical applications. In order to know if these nanoparticles could degrade, the present work consists of studying their fate over time depending on both their coating and the aqueous media in which they are dispersed. ZGO nanoparticles have been dispersed in three different aqueous solutions for up to 90 days and characterized by numerous techniques. Among the evaluated dispersion media, Artificial Lysosomal Fluid (ALF) mimicking the intracellular lysosome environment elicited significant degradation of ZGO nanoparticles. The chelating agents present in ALF have proved to play a major role in the degradation of the ZGO, by stabilizing the nanoparticles and increasing the contact. An important time decrease of the luminescence properties has also been observed, which correlated with the release of ions from ZGO nanoparticles as well as their decreasing size. This information is valuable since it indicates, for the first time, the long-term degradation of persistent luminescent nanoprobes in an in vivo like model medium. Therefore, possible elimination of the imaging probes after in vivo preclinical applications could be foreseen.

Baltic Fucus vesiculosus as potential bio-sorbent for Zn removal: Mechanism insight

This research aimed to find the best phenotype of the brown algae Fucus vesiculosus (kelp) which has the greater potential to become a sorption byproduct for Zn removal from contaminated waters. Thus, the Zn uptake capacity and sorption mechanisms of the kelp collected from the Baltic Sea shore was, for the first time, investigated under various conditions, and compared to the phenotype habiting on the Irish Sea shore. Sorption studies were performed investigating the effect of algal dosage, Zn sources as well as algal harvesting time of the year on Zn uptake capacity. The results suggested that the Baltic algae is a better bio-sorbent for Zn uptake. Sorption mechanisms were studied by employing various indirect and direct approaches, more importantly, including high resolution synchrotron X-Ray Fluorescence and X-Ray Absorption Spectroscopy (XAS) and molecular modelling (MM). The results revealed that alginate and cellulose are among the main polysaccharide bonding Zn at algal surface, via coordination with O atoms from carboxyl and hydroxyl groups. XAS results giving direct measurements of Zn bonding environment on algal surface are supported by MM outputs and suggested that Zn is surrounded by ca. 5 O atoms at interatomic distances varying from 1.94 to 2.02 Å. The results contribute to understanding sorption mechanisms which can further lead to finding the best eluent for Zn desorption from the used biomass, bio sorbent reconditioning and reuse in multiple sorption desorption cycles as well as process optimization before industrial scaling up.

Study of Zn availability, uptake, and effects on earthworms of zinc oxide nanoparticle versus bulk applied to two agricultural soils: Acidic and calcareous

The increasing use of zinc oxide nanoparticles (ZnO NPs) in agriculture renders it necessary to evaluate their impact on soil non-target organisms. This work studies Zn availability to earthworms from the ZnO (NP and bulk) applied to two agricultural soils with a different pH at 20, 225, 500, and 1000 mg Zn kg^-1. Zn uptakes and the effects on Eisenia andrei, grown under controlled conditions, were determined. Effects were assessed at three levels: organisms, mortality, growth and reproduction; biochemical, catalase and glutathione S-transferase activities, malondialdehyde (MDA), and protein content; cellular in coelomocytes, reactive oxygen species (ROS) generation, lysosomal membrane alterations (RN) and mitochondrial dysfunction (MTT). Available Zn was 100-fold higher in acidic than in calcareous soil and did not differ among ZnO (NP or bulk). Zn in worms was auto-regulated regardless of the soil Zn concentration, pH and ZnO size. Effects on mortality and weight were observed only in the acidic soil at the highest concentration, ZnO NPs reduced survival and body weight, while ZnO bulk reduced body weight. Reproduction parameters in acidic soil were: EC50 (fecundity) 277 and 256 mg Zn kg-1 and EC50 (fertility) 177 and 179 mg Zn kg-1 for ZnO NPs and bulk, respectively, with no found NP-specific effects. No responses of enzymatic activities, MDA and MTT were detected. ROS and RN were altered in the coelomocyte cells of earthworms in the two soils, but effects depended on ZnO size suggesting nanospecific effects. Soil pH governs toxicity more than ZnO size regardless of body Zn concentration.

Effects of Dietary Different Levels of Nano, Organic and Inorganic Zinc Sources on Performance, Eggshell Quality, Bone Mechanical Parameters and Mineral Contents of the Tibia, Liver, Serum and Excreta in Laying Hens

This study was conducted to determine the effect of dietary zinc (Zn) sources and their levels on the performance, egg quality, tissue mineral concentrations and bone mechanical traits of laying hens. Two hundred seventy, 44-week-old, Super Nick white laying hens were randomly distributed to 15 experimental groups in a 3 (sources of Zn) × 5 (levels of Zn) factorial arrangement, using groups of 18 birds with 6 replicates. The 15 experimental diets consisted of three sources of Zn (zinc-oxide as an inorganic form, zinc-proteinate as an organic form and nano zinc-oxide powder as a nano form) and five different levels of Zn (20, 40, 60, 80 and 100 mg Zn/kg diet). The experiment lasted 12 weeks. Dietary Zn sources, Zn levels and their interactions had no significant effect on the performance parameters between the treatment groups, nor a significant effect on eggshell weight and eggshell breaking strength. Eggshell thickness and eggshell Ca and P contents were significantly affected by the different dietary Zn sources. Dietary Zn sources, Zn levels and their interactions had no significant effect on tibia Ca and P contents, and also had no significant effect on tibia Zn content. Liver Zn content was significantly affected by the dietary Zn sources. Serum Zn content was not affected by the dietary treatments. Dietary Zn sources, Zn levels and their interactions had no significant effect on tibia weight, tibia stress and tibia breaking strength, as tibia mechanical parameters. Excreta Zn content decreased linearly when hens were fed nano Zn compared to organic and inorganic Zn, and excreta Zn content also linearly increased with increasing dietary Zn levels. In conclusion, 20 mg/kg of supplemental Zn is optimal for sustaining performance, good eggshell quality and bone status, while also reducing Zn excretion and soil pollution, with organic (Zn-proteinate) and nano (ZnO) Zn as the preferred forms in laying hen diets.

Peruvian scallop Argopecten purpuratus: From a key aquaculture species to a promising biondicator species

The present study analyzed the Peruvian scallop Argopecten purpuratus and its food sources for metal and fatty acid concentrations in order to determine spatial and temporal differences. Metals such as copper (Cu), manganese (Mn), and zinc (Zn) in gills and iron (Fe) and Zn in sediments were the most significant explaining factors for spatial differentiations (degree of contamination), while for fatty acids, it was C14:0, C15:0, C16:0 and C18:0 in A. purpuratus' muscle and in its food sources, which explained more temporal differences (El Niño-Southern Oscillation (ENSO) effect). Gills, digestive gland and intestine were the tissues where metal accumulation was the highest in A. purpuratus. Cd in digestive gland was always high, up to ∼250-fold higher than in other tissues, as previously reported in other bioindicator species for metal pollution. Fatty acids were good biomarkers when annual comparisons were performed, while metals when locations were compared. ENSO 2017 played an important role to disentangle A. purpuratus' biological conditions and food sources. A. purpuratus from Paracas locations mostly showed higher metal concentrations in gills and digestive glands, and lower fatty acid concentrations in muscle than those from Sechura and Illescas Reserved Zone.

Will the antimicrobial properties of ZnONPs turn it into a more suitable option than AgNPs for water filtration? Comparative study in the removal of fish pathogen, Aeromonas hydrophila from the culture of juvenile common carp (Cyprinus carpio)

The purpose of this study was to investigate the possibility of using zinc oxide nanoparticles (ZnONPs) instead of silver nanoparticles (AgNPs) for removing Aeromonas hydrophila from water used to culture Cyprinus carpio juvenile. Antibacterial materials as filter media were prepared by coating ZnONPs (two coating methods, referred as ZnA and ZnB) or AgNPs (referred as Ag) on the porous surfaces of zeolite beads. The characterization of coated samples was determined using FESEM, EDS, and GFAAS. The antibacterial activities of prepared samples were evaluated by the zone of inhibition test, tube test, and flow test. The diameter of inhibitory zones formed by ZnONP- and AgNP-coated zeolite beads was significantly higher than uncoated zeolite (control) (P < 0.05). Also, the tube test results revealed 100% killing of the bacterial cells after 24 h of contact to all coated materials. In the flow test (without fish), the antibacterial efficiency of filter columns that contained ZnA, ZnB, and Ag found to be 34.84, 23.77, and 100% after 96 h, respectively. The mortality rate of carp juveniles cultured in infected water treated with AgNP filters was significantly lower than those cultured in infected water or treated with ZnONPs filters (P < 0.05). The results indicated that although ZnONP filter media have somewhat antimicrobial properties (especially in vitro), their ability to complete removal of microorganisms from the water is not as high as AgNP filters. So, it still seems that zeolite coated with AgNPs has a higher potential for water disinfection in aquaculture.

Zinc sulphide nanoparticle (nZnS): A novel nano-modulator for plant growth

In spite of extraordinary properties of zinc sulphide nanoparticle (nZnS), its role on plant system is not well understood, yet. Therefore, this study was aimed to assess the uptake, translocation and effects of nZnS in mung bean (Vigna radiata) plant at 0, 0.1, 0.5 and 1 mg L^-1 concentrations. In this study, nZnS was synthesized by modified reflux method and physicochemical characterizations were conducted. The effects of nZnS on mung bean plant were determined by seed germination, growth parameters, membrane integrity and ROS-antioxidant defense assays. Our results showed that nZnS treatment has significantly increased seed germination, root-shoot length, pigment content and decreased lipid peroxidation. There were increased total antioxidant activity (TAA), DPPH and flavonoid contents found in treated plants. Also, nZnS treatment did not activate oxidative stress determined by SOD, CAT, CPX, APOX and GR activities. The uptake and translocation of nZnS in mung bean plants were determined by Transmission Electron Microscope (TEM) and Scanning Electron Microscope (SEM), revelling that nZnS localized primarily in the vacuoles and chloroplasts. Besides, electron micrographs showed no alteration in cell structures between treated and control plants, further confirming that nZnS treatment has no phytotoxic effects. In vitro and in vivo studies on Zn release from nZnS were also determined using Inductively Coupled Plasma Mass Spectroscopy (ICPMS) and Energy Dispersive X-ray (EDX), which showed that the Zn release and particles uptake were concentration dependent. Overall, results of this study demonstrated the positive role of nZnS on growth and antioxidant defense responses in V. radiata at the experimental concentrations.

Effects of vermicomposting on the main chemical properties and bioavailability of Cd/Zn in pure sludge

To study the effects of vermicomposting on the chemical properties and bioavailability of Cd/Zn in sludge, earthworms (Eisenia foetida) at different densities were inoculated into pure sludge, and sludge and earthworms were collected regularly to determine the earthworm biomass, the main chemical indexes, the structure of the functional groups, and the Cd/Zn content in the sludge. The results showed that the growth curve of earthworms in pure sludge could be well fitted by the logistic model. Earthworm activity eventually reduced the total organic carbon (TOC), fulvic acid (FA), and C/N ratio and increased the electrical conductivity (EC), total nitrogen (TN), humic acid (HA), and HA/FA ratio in the sludge. TOC, TN, and pH inhibited the bioavailability of Cd/Zn, while HA and EC promoted the bioavailability of Cd/Zn. Earthworm activity ultimately increased the content of Cd/Zn in the sludge. The bioavailability of Cd/Zn was reduced during the rapid growth period of the earthworms but increased during the stable growth period of the earthworms. A suitable vermicomposting time should be determined to ensure the activation or passivation of Cd/Zn.

Theoretical and experimental studies concerning monomer/aggregates equilibrium of zinc phthalocyanine for future photodynamic action

Monomeric zinc phthalocyanine has been studied as a promising active photosensitizer in photodynamic therapy against cancer, in which its aggregate form is non-active. This paper aimed to describe the monomer/aggregates equilibrium of zinc phthalocyanine in binary water/DMSO mixtures. To reach this aim theoretical calculation, electronic absorption, static and time-resolved fluorescence, and resonance light scattering was used. Zinc phthalocyanine shows a complex water dependence behavior in the mixture. At least three distinct steps were observed: (i) until 30% water zinc phthalocyanine is essentially in the monomeric form, changing to (ii) small slipped cofacial-aggregates around 30% to 40% water and finally to (iii) a staircase arrangement of large aggregates at higher water percent. The staircase arrangement is driven by the intermolecular coordination between the pyrrolic nitrogen lone-pairs and the central metal zinc. The water-Zn coordination governs the fluorescence quenching by a static mechanism. These results have direct relevance in the better understanding on the behavior of zinc phthalocyanine in vivo and when incorporated in drug delivery systems for clinical applications in photodynamic therapy.

The combined effects of Cr(III) propionate complex supplementation and iron excess on copper and zinc status in rats

It is suggested that both iron overload and chromium(III) deficiency may be risk factors of diabetes. It seems that both Fe and Cr(III) metabolism as well as copper and zinc metabolism are interrelated. However, the direction of these changes may depend on mutual proportions of these elements in the diet and organism. The aim of the study was to evaluate the combined effects of Cr(III) supplementation with Fe excess on the Cu and Zn status in female rats. Thirty-six healthy rats were divided into 6 experimental groups with different Fe levels in the diet. Groups marked with C (control) contained Fe at the recommended level (45 mg kg^-1). The excess groups (E) contained Fe at 180 mg kg^-1. At the same time the animals were supplemented with Cr(III) of doses 1, 50 and 500 mg kg^-1 of diet. The Cr, Fe, Cu and Zn dietary and tissular contents were measured with the AAS method.The excess Fe in the diet significantly decreased the Cu content in the liver and kidneys, but it increased the spleen Cu level. The Cr(III) supplementary did not affect the tissular Cu levels, regardless of Fe supply with diet. The experimental factors did not have significant interactional effect on the Cu status parameters under study.The Fe excess in the diet reduced the renal and splenic Zn content, but increased the heart Zn content. The Cr(III) supplementation decreased the Zn content in the kidneys. The Zn content in the liver and spleen tended to decrease as the Cr(III) supply in the diet increased. There was no significant interactional effect of Cr(III) supplementation and the Fe excessive supply in diet on the parameters of Zn metabolism in Wistar rats. Iron oversupply disturbed the rat's Cu and Zn status. However, Cr(III) supplementation did not affect the tissular levels of these elements, except the kidney Zn content. Simultaneous supplementation with the Cr(III) propionate complex did not deepen changes in tissular Cu and Zn levels caused by the Fe excess in the diet.

Identifying sediment-associated toxicity in rivers affected by multiple pollutants from the contaminant bioavailability

In this study, we estimated the toxicity risks from river sediments that were affected by multiple pollutants in the Haihe River Basin. We used a range of methods to determine the concentrations, bioavailability, and toxicity of a range of metals and contaminants in sediments and sediment porewater and then assessed the ecological risks and toxicity using various multivariate statistical approaches. We found that more than 70% of the samples were toxic. The concentrations of non-ionic ammonia (0.168-9.295 mg L^-1) were generally high in the sediment porewater, while the concentrations of bioavailable chromium (Cr) and polycyclic aromatic hydrocarbons (PAHs) were also high in the porewater samples from NW01 and NW02, respectively. We used the toxic unit (TU) approach, based on the bioavailable pollutant concentrations, to determine the toxicity of PAHs, heavy metals, and non-ionic ammonia in river sediments and sediment porewater. We found that non-ionic ammonia was the main source of toxicity for Daphnia magna, and that Cr and zinc were toxic for Pseudokirchneriella subcapitata and Chironomus dilutus. By combining various indexes, we identified the main contributors to the toxicity in sediments collected from rivers affected by multiple pollutants.

Mechanical Strength, Biodegradation, and in Vitro and in Vivo Biocompatibility of Zn Biomaterials

Zn-based biomaterials have emerged as promising new types of bioresorbable metallics applicable to orthopedic devices, cardiovascular stents, and other medical applications recently. Compared to other degradable metallic biomaterials (i.e., Mg- or Fe-based), Zn biomaterials have a more appropriate corrosion rate without hydrogen gas evolution. Here, we evaluated the potential of Zn-based metallics as medical implants, both in vitro and in vivo, alongside a standard benchmark Mg alloy, AZ31. The mechanical properties of the pure Zn were not strong enough but were significantly enhanced (microhardness > 70 kg/mm², strength > 220 MPa, elongation > 15%) after alloying with Sr or Mg (1.5 at. %), surpassing the minimal design criteria for load-bearing device applications. The corrosion rate of Zn-based biomaterials was about 0.4 mm/year, significantly slower than that of AZ31. The measured cell viability and proliferation of three different human primary cells fared better for Zn-based biomaterials than AZ31 using both direct and indirect culture methods. Platelet adhesion and activation on Zn-based materials were minimal, significantly less than on AZ31. The hemolysis ratio of red cells (<0.5%) after incubation with Zn-based materials was also well below the ISO standard of 5%. Moreover, Zn-based biomaterials promoted stem cell differentiation to induce the extracellular matrix mineralization process. In addition, in vivo animal testing using subcutaneous, bone, and vascular implantations revealed that the acute toxicity and immune response of Zn-based biomaterials were minimal/moderate, comparable to that of AZ31. No extensive cell death and foreign body reactions were observed. Taken together, Zn-based biomaterials may have a great potential as promising candidates for medical implants.

Biochemical, molecular, and elemental profiling of Withania somnifera L. with response to zinc stress

Zn stress seriously induces various toxic responses in Withania somnifera L., when accumulated above the threshold level which was confirmed by investigating the responses of protein, expression of antioxidant enzymes, and elemental profiling on accumulation of Zn. Zn was supplemented in the form of ZnSO₄ (0, 25, 50, 100, and 200 μM) through MS liquid medium and allowed to grow the in vitro germinated plants for 7 and 14 days. The study revealed that when the application of Zn increased, a significant reduction of growth characteristics was noticed with alterations of proteins (both disappearance and de novo synthesis). The activity of CAT, SOD, and GPX were increased up to certain concentrations and then declined, which confirmed through in-gel activity under different treatments. RT-PCR was conducted by taking three sets of genes from CAT (RsCat, Catalase1, Cat1) and SOD (SodCp, TaSOD1.2, MnSOD) and found that gene RsCat from CAT and MnSOD from SOD have shown maximum expression of desired genes under Zn stress, which indicate plant's stress tolerance mechanisms. The proton-induced X-ray emission study confirmed an increasing order of uptake of Zn in plants by suppressing and expressing other elemental constituents which cause metal homeostasis. This study provides insights into molecular mechanisms associated with Zn causing toxicity to plants; however, cellular and subcellular studies are essential to explore molecule-molecule interaction during Zn stress in plants.

The Effect of Maternal Supplementation of Zinc, Selenium, and Cobalt as Slow-Release Ruminal Bolus in Late Pregnancy on Some Blood Metabolites and Performance of Ewes and Their Lambs

The aim of this study was to determine the effect of the supplementation of a slow-release bolus of zinc (Zn), selenium (Se), and cobalt (Co) at late gestation (6 week prepartum) on performance and some blood metabolites of Mehraban ewes and their lambs until weaning. Seventy pregnant ewes, 6 weeks prior to expected lambing, were randomly divided into two groups (35 heads each) including (1) control group and (2) slow-release bolus group. Blood samples of ewes were obtained on day 10 prepartum and 45 and 90 days postpartum, and milk samples were collected on day 45. Blood samples of lambs were collected on days 10, 45, and 90. Body weight at birth and weaning and average daily gain were higher and percentage of mortality and white muscle disease rate were lower in lambs whose mothers were given a bolus (P < 0.05). Slow-release bolus administration increased serum alkaline phosphatase and whole blood glutathione peroxidase activity, plasma concentrations of Zn, Se, and vitamin B₁₂ in ewes and their lambs (P < 0.05). In addition, serum creatine phosphokinase activity of lambs whose mothers were given bolus was lower (P < 0.05). Serum concentration of T₃ in bolus given ewes and their lambs was higher (P < 0.05) and serum T₄ concentration was lower (P < 0.05). Zinc, Se, and vitamin B₁₂ concentrations in milk were significantly higher in treated ewes (P < 0.05). Obtained results showed that maternal supplementation of zinc, selenium, and cobalt as slow-release ruminal bolus in late pregnancy improved some mineral status of ewes and their lambs until weaning and led to higher body weights of lambs at weaning.

Non-invasive microelectrode cadmium flux measurements reveal the decrease of cadmium uptake by zinc supply in pakchoi root (Brassica chinensis L.)

Zinc (Zn) possesses similar properties to cadmium (Cd) and inhibits Cd uptake in plants. To get more detailed mechanisms of Zn-inhibited Cd uptake in pakchoi, a hydroponic experiment was conducted to investigate the effects of various Zn levels on Cd concentrations, real time flux of Cd, expressions of genes related to Cd uptake under Cd exposure. The results showed that the Cd concentrations and Cd accumulations in pakchoi root decreased with increasing Zn levels, which were coincident with that real time Cd influx and net Cd influx of pakchoi root decreased with increasing Zn levels by non-invasive micro-test technology (NMT). Additionally, the expressions of Cd-related transporters including BcNRAMP5, BcIRT1 and BcMGT1 decreased with the increase of Zn levels under Cd exposure, especially BcIRT1 with the highest decreased rates. Furthermore, the expressions of these genes decreased gradually with the prolongation of Zn treated time under Cd toxicity. The results indicate that Zn inhibits Cd uptake by inhibition of the expressions of Cd-related transporters, especially BcIRT1 in pakchoi root.

Chromium-Doped Zinc Gallogermanate@Zeolitic Imidazolate Framework-8: A Multifunctional Nanoplatform for Rechargeable In Vivo Persistent Luminescence Imaging and pH-Responsive Drug Release

Multifunctional theranostic nanoplatforms greatly improve the accuracy and effectiveness in tumor treatments. Much effort has been made in developing advanced optical imaging-based tumor theranostic nanoplatforms. However, autofluorescence and irradiation damage of the conventional fluorescence imaging technologies as well as unsatisfied curative effects of the nanoplatforms remain great challenges against their wide applications. Herein, we constructed a novel core-shell multifunctional nanoplatform, that is, chromium-doped zinc gallogermanate (ZGGO) near-infrared (NIR) persistent luminescent nanoparticles (PLNPs) as a core and zeolitic imidazolate framework-8 (ZIF-8) as a shell (namely ZGGO@ZIF-8). The ZGGO@ZIF-8 nanoplatform possessed dual functionalities of the autofluorescence-free NIR PersL imaging as well as the pH-responsive drug delivery, thus it has high potential in tumor theranostics. Notably, the loading content of doxorubicin (DOX) in ZGGO@ZIF-8 (LC = 93.2%) was quite high, and the drug release of DOX-loaded ZGGO@ZIF-8 was accelerated in an acidic microenvironment such as tumor cells. The ZGGO@ZIF-8 opens up a new material system in the combination of PLNPs with metal-organic frameworks and may offer new opportunities for the development of advanced multifunctional nanoplatforms for tumor theranostics, chemical sensing, and optical information storage.

EDTA and organic acids assisted phytoextraction of Cd and Zn from a smelter contaminated soil by potherb mustard (Brassica juncea, Coss) and evaluation of its bioindicators

Phytoremediation of contaminated soil is an in-situ reclamation technique for removal of potentially toxic metals through hyperaccumulator plants. Potherb mustard (Brassica juncea, Coss.) is less explored for its assisted phytoextraction potential to restore and accelerate potentially toxic metals removal from smelter-contaminated soil. In this study, different levels of ethylene diamine tetraacetic acid (EDTA) alone and combined with citric acid (CA) and oxalic acid (OA) were applied in a greenhouse pot experiment. Chelates added on 25th d and 25/35th d after sowing, enhanced cadmium (Cd) and zinc (Zn) bioavailability in soil due to complexation. As a result, Cd and Zn in shoot and root were significantly amplified by 1.7, 2.15 and 1.93, 2.7 folds than control, respectively. Shoot and root dry weight significantly reduced and ranged between 4.13-9.91 and 0.21-0.77 g pot^-1, respectively. The toxicity induced by potentially toxic metals in plant imposed a series of biological responses. Plant antioxidants like Phenylalanine ammomialyase (PAL), polyphenol oxidase (PPO) Catalase (CAT) content increased, except the peroxidase (POD) with the addition of chelating agents. Besides, biological concentration factor (BCF) of Cd and Zn, translocation factor (TF) of Cd were notably elevated (>1.0), while TF of Zn was reduced. Pearson correlation analysis showed a positive relation between DTPA-extractable and shoot concentration of Cd and Zn, whereas it showed negative correlation with plant dry weight. In general, chelate-assisted phytoremediation of smelter contaminated soil proved effective in this study, and followed the order: EDTA > EDTA + CA ≈ EDTA + OA > CK.

Bioaccumulation of Copper and Zinc and the Effects on Antioxidant Enzyme Activities in the Liver of Acipenser stellatus (Pallas, 1771)

Although water pollution by metals in the Danube River is considered high, little is known about its impact on sturgeons. In this regard, the aim of this study was to investigate the bioaccumulation of copper and zinc as well as their effects on antioxidant enzymes activities in the liver of Acipenser stellatus. The fish were exposed for 7 and 14 days, to two concentrations of copper and zinc (10% and 25% of LC50 96 h), previously determined as 0.54 mg/L Cu²⁺ and, 34.22 mg/L Zn²⁺ respectively. The enzymatic responses of A. stellatus varied greatly depending on metal type, concentration and time. Significant bioaccumulation of the two metals was recorded. Even though the water hardness used in the experiment is known to offer a clear protection against metal contamination, stellate sturgeon remains a sensitive species in the face of metal toxicity.

The response of larvae Brachymystax lenok during continuous and single pulses exposure to copper, zinc, lead and cadmium

The continuous and single pulses exposure of Cu, Zn, Pb and Cd on larvae Brachymystax lenok were tested in this study. The first-order kinetics was employed to obtain better comprehension on the time-toxicity relationship of tested heavy metals in continuous exposure test. For difference in time-varying exposure or recovery, 50% lethal time-averaged concentration (TAC) was used to assess the pulsed toxicity, which took both time and concentration into consideration in exposure and post-exposure period. TAC assessment to the single pulses and the regression analysis of first-order kinetic to continuous exposures demonstrated that Cu and Zn showed greater toxicity than Pb and Cd, indicating a slower uptake and/or depuration effect for zinc or copper. Furthermore, the results showed that recovery effect of larvae to all four metals was found in 24 h exposure followed by 72 h in fresh water, while for 72 h exposure and 24 h non-exposure the delayed lethal phenomenon occurred.

Characterization of composted sewage sludge during the maturation process: a pilot scale study

This paper determines the impact of the maturation process of composted sewage sludge on the quality of the final product and assesses the stabilization effect. The samples of composted sewage sludge were taken from a wastewater treatment plant located in Pomerania in northern Poland. The sewage sludge was composted in an open windrow composting plant with the addition of straw and wood chips in the turning windrow. The aeration of the sewage sludge mixture was conducted based on two methods. The first phase (intensive degradation phase of 6 to 8 weeks) was characterized by frequently turning; the second phase for maturation used aeration channels (2 to 3 months). In three sampling campaigns samples were taken from the same windrow after 2 (no. 1), 8 (no. 2), and 12 weeks (no. 3) of maturation. Fresh samples were used for analyzing the stabilization parameter as static respiration activity (AT₄). Furthermore, the values of pH, organic matter (OM), total organic carbon (TOC), elementary composition, nutrients, total content, and mobile forms of heavy metals were analyzed in the compost samples. A significant decrease was found in the stabilization parameter (AT₄) during the maturation of tested materials. In turn, no significant differences were found in the elementary composition. The concentration of most metals increased in the final product. The total content of heavy metals in the final product did not exceed the limit values for the agricultural use of sewage sludge, compost from municipal waste, and for organic fertilizers. There were no significant changes in the percentage of bioavailable and mobile forms of heavy metals during compost maturation. Zinc was characterized by the highest level of mobile and bioavailable forms, which may cause bioaccumulation after the fertilization of soil. The study has shown that the process of maturation of compost from sewage sludge not affects changes in the content of heavy metal forms. The scope of this study has been planned on a wider scale for different variants of sewage sludge composting, in order to evaluate the process.

Effects of tapeworm infection on absorption and excretion of zinc and cadmium by experimental rats

The main objective of this study was to determine how rat tapeworms affect the excretion of zinc and cadmium through rat feces. Male rats (Rattus norvegicus var. alba) were divided into four groups, and the experiment was conducted over a 6-week period. The control groups (00; 0T) were provided with a standard ST-1 rodent mixture and received 10.5 mg of Zn/week. Groups P0 and PT were fed a mixture supplemented with the hyperaccumulating plant Arabidopsis halleri at a dosage of 123 mg Zn/week and 2.46 mg Cd/week. Groups 0T and PT were infected with the rat tapeworm (Hymenolepis diminuta). Fecal samples were collected 24 h post exposure. Zinc and cadmium concentrations in rat feces were analyzed using inductively coupled plasma optical emission spectrometry. Tapeworm presence decreased the amount of metals excreted through the feces of the host throughout the entire experiment, with the exception of 1 week (control group). No statistically significant differences between zinc excretion rates in the control groups (00 and 0T) were detected at any time throughout the experiment. A statistically significant difference between zinc excretion rates (p < 0.05) in the exposed groups (P0 and PT) was detected in 2 of the 6 monitored weeks. Group PT excreted significantly less cadmium (p < 0.01) than group P0 did in three of the 6 weeks. Overall, our results indicate that tapeworms are able to influence the excretion of metals by their host. Tapeworms accumulate metals from intestinal contents. It is not clear whether tapeworms carry out this process before the host tissues absorb the metals from the intestines or the tapeworms accumulate metals excreted from the body of the host back to the intestines. Most likely, it is a combination of both phenomena.

Seasonal and spatial variations of biomarker responses of rock oysters in a coastal environment influenced by large estuary input

The present study assessed the spatial and temporal variations and the potential influences of the Pearl River discharge on trace metal bioaccumulation and biomarker responses in Hong Kong coastal waters. A suite of biomarkers including antioxidant defense, oxidative stress, metal detoxification, cellular response, neurotoxicity, and energy reserve were quantified in the rock oyster Saccostrea cucullata over spatial scale across the east and west of Hong Kong. We documented the elevated Cd, Cu and Zn concentrations in all western stations in the fall season, as a result of time-integrated accumulation during the peak discharge of the Pearl River Estuary (PRE) in summer. Lipid peroxidation and total glutathione corresponded well with the overall metal gradient and showed significant correlation with the tissue Cu bioaccumulation. The eastern station (Clear Water Bay) also exhibited high Cd and Cu concentrations with increased oxidative stress responses. In the spring, metal bioaccumulation in the oysters was reduced due to the weakened influence of PRE, with correspondingly less obvious biomarker responses. Our coupling measurements of biomarkers and tissue metal concentrations for the first time revealed that the large PRE could have latent and seasonal biological effects on the Hong Kong coastal biota. Sensitive biomarkers such as lipid peroxidation and glutathione responses might be good candidates for detecting the early biological responses in such sub-lethal contaminated environments.

Single and combined effects of Zn, Mn and Fe on the Neotropical freshwater bivalve Anodontites trapesialis: Bioaccumulation and biochemical biomarkers

Important concentrations of Zn, Mn and Fe were detected in a stream near a coal mining area and promoted, in field, biomarkers alterations in the bivalve Anodontites trapesialis. In order to understand the isolated and mixed effects of these metals on these Neotropical bivalves, we run short-term experiments under laboratory controlled conditions. After 96 h-exposure, tissues (gills, mantle, digestive gland, muscle, hemolymph) were removed for metal bioaccumulation analysis, oxidative stress biomarkers (reactive oxygen species (ROS), total antioxidant capacity, lipoperoxidation (LPO), proteins carbonylation (PC), metallothionein (MT), activity of superoxide dismutase and glutathione S-transferase and hemocytes DNA damage) and cholinesterase (ChE versus ASCh activity) activity evaluation. We run three independent tests. In Zn test, clams were exposed to three concentrations of Zn (0.18 mg L^-1, 1.0 mg L^-1, 5.0 mg L^-1); in Mn test, clams were exposed to three concentrations of Mn (0.1 mg L^-1, 0.5 mg L^-1, 5.0 mg L^-1) and in Mix test, clams were exposed to the mixture Zn (1 mg L^-1) + Mn (0.5 mg L^-1), with and without Fe (5.0 mg L^-1). After single exposure to 5.0 mg L^-1, Zn bioaccumulated in all tissues, but only in mantle and hemolymph after exposure to 1.0 mg L^-1. The increased MT in gills of A. trapesialis exposed to Zn appears to be sufficient to avoid damage, since LPO occurred only in digestive glands from animals exposed to 5.0 mg L^-1. We suggested that A. trapesialis had a metabolic suppression in consequence of Mn presence, based on the following results: the decrease of ROS in gills, the decrease of the Zn and Mn concentrations in tissues and the decrease of ChE versus ASCh activity in muscle. Despite this, animals exposed to Mn suffer oxidative damages (LPO and PC) in the mantle and digestive gland and MT increased in the mantle. These results showed A. trapesialis responded differently to each metal and Mn caused more damage. When exposed to Fe, gills level of ROS was increased, despite no changes in metal accumulation occurred. On the other hand, after exposure to the mixtures, tissues bioaccumulated Zn and previously observed damages caused by Mn and Fe disappeared. Consequently, biomarkers were less affected under mixture treatments, demonstrating mixtures effects or responses were not simply a combination of single exposures to Zn, Mn and Fe, but depend on metals toxicokinetics.

Enhanced In Vitro Zinc Bioavailability through Rational Design of a Dual Zinc plus Arginine Dentifrice

OBJECTIVES

To investigate bioavailability enhancement of zinc on model oral surfaces and in oral biofilms in vitro through strategic formulation with two sources of zinc and L-arginine.

METHODS

To modulate the bioavailability of active zinc ions in a zinc citrate dentifrice, an additive research strategy was pursued. A series of zinc citrate dentifrice formulations were prepared with increasing replacement of zinc citrate with zinc oxide (a water insoluble source of zinc ions) to generate a Dual Zinc active system. A screening of isolated zinc and amino acid effects in simple solutions using zeta potential and uptake to model oral surfaces was performed in an effort to determine the effect of particle charge on zinc bioavailability. Zinc delivery and antibacterial efficacy of the Dual Zinc plus Arginine dentifrice formula were tested using in vitro oral epithelial tissue and saliva-derived biofilm models. Furthermore, zinc penetration and retention were determined by subjecting in vitro biofilms to dynamic flow after treatment with the Dual Zinc plus Arginine dentifrice with treated biofilms evaluated for zinc using imaging mass spectrometry (I-MS). Bacterial adhesion to gingival epithelial cells treated with the Dual Zinc plus Arginine dentifrice was imaged upon challenging with Streptococcus gordonii.

RESULTS

Addition of zinc oxide into a zinc citrate dentifrice formula enhanced the efficacy of the system against anaerobic biofilms in a concentration- dependent manner. L-arginine further provided a significant positive charge (+36 mV) to the zinc oxide suspension (+16 mV) as measured by zeta potential. Simple solutions of the Dual Zinc active showed increased zinc uptake on model oral surfaces as a direct function of L-arginine concentration. Antibacterial efficacy of a Dual Zinc plus Arginine dentifrice was evaluated through multiple mechanisms. Enhanced antibacterial performance was observed through significant reductions in metabolic activity as measured through bacterial glycolytic function (p = 0.0001) and total oxygen consumption (p = 0.0001). Greater penetration and retention of zinc was observed in bacterial biofilms treated with the Dual Zinc plus Arginine dentifrice in comparison to treatment with a Dual Zinc dentifrice after twelve hours of dynamic flow (10 mL/hour) in an in vitro drip flow biofilm culture. Confocal microscopy showed adherent bacteria on cheek cells treated with the Dual Zinc plus Arginine dentifrice formula.

CONCLUSIONS

The combination of zinc citrate, zinc oxide, and the amino acid L-arginine in a dentifrice formula enhances the bioavailability of zinc to model oral tissue surfaces, resulting in unique physicochemical effects. The significant antimicrobial control associated with the Dual Zinc plus Arginine dentifrice provides a unique vehicle toward achieving whole mouth health.

Use of Stable Isotopes to Evaluate Bioefficacy of Provitamin A Carotenoids, Vitamin A Status, and Bioavailability of Iron and Zinc

The ability of nutrition scientists to measure the status, bioavailability, and bioefficacy of micronutrients is affected by lack of access to the parts of the body through which a nutrient may travel before appearing in accessible body compartments (typically blood or urine). Stable isotope-labeled tracers function as safe, nonradioactive tools to follow micronutrients in a quantitative manner because the absorption, distribution, metabolism, and excretion of the tracer are assumed to be similar to the unlabeled vitamin or mineral. The International Atomic Energy Agency (IAEA) supports research on the safe use of stable isotopes in global health and nutrition. This review focuses on IAEA's contributions to vitamin A, iron, and zinc research. These micronutrients are specifically targeted by the WHO because of their importance in health and worldwide prevalence of deficiency. These 3 micronutrients are included in food fortification and biofortification efforts in low- and middle-income regions of the world. Vitamin A isotopic techniques can be used to evaluate the efficacy and effectiveness of interventions. For example, total body retinol stores were estimated by using 13C2-retinol isotope dilution before and after feeding Zambian children maize biofortified with β-carotene to determine if vitamin A reserves were improved by the intervention. Stable isotopes of iron and zinc have been used to determine mineral bioavailability. In Thailand, ferrous sulfate was better absorbed from fish sauce than was ferrous lactate or ferric ammonium citrate, determined with the use of different iron isotopes in each compound. Comparisons of one zinc isotope injected intravenously with another isotope taken orally from a micronutrient powder proved that the powder increased total absorbed zinc from a meal in Pakistani infants. Capacity building by the IAEA with appropriate collaborations in low- and middle-income countries to use stable isotopes has resulted in many advancements in human nutrition.

Foliar application of zinc sulphate and zinc EDTA to wheat leaves: differences in mobility, distribution, and speciation

Foliar application of zinc (Zn) to crops is an effective way to increase the grain concentration of Zn. However, the development of more efficient foliar Zn fertilizers is limited by a lack of knowledge regarding the distribution, mobility, and speciation of Zn in leaves once it is taken up by the plant. We performed an experiment using radiolabelled Zn (65Zn), and in situ time-resolved elemental imaging using synchrotron X-ray fluorescence microscopy (XFM), to investigate the behaviour of two commonly used Zn foliar fertilizers (Zn sulphate and ZnEDTA) in wheat (Triticum aestivum) leaves. Both experiments showed that Zn had limited mobility in leaves, moving <25 mm from the application point after 24 h. Although limited, the translocation of Zn occurred quickly for both treatments; moving more between 3 h and 12 h after application than between 12 h and 24 h. Speciation analysis using synchrotron-based X-ray absorption near-edge structure (XANES) showed that ZnEDTA was in fact taken up in chelated form and not as ionic Zn (Zn2+). The XANES data also showed that Zn, from both treatments, was then complexed by ligands in the leaf (e.g. phytate and citrate), potentially in response to localized Zn toxicity. The results of the present study provide important insights into the behaviour of commonly used foliar-applied Zn fertilizers, and can be used to optimize current fertilization strategies and contribute to the development of more efficient foliar Zn fertilizers.

Effects of ZnSO4 and Zn-EDTA broadcast or banded to soil on Zn bioavailability in wheat (Triticum aestivum L.) and Zn fractions in soil

Human Zn deficiency is prevalent in developing countries, and staple grains are commonly bio-fortified to increase their Zn contents. We measured Zn content, distribution, and bioavailability in calcareous soil and in wheat plants (Triticum aestivum L.) in Shaanxi Province, China, when either an organic Zn-ethylenediaminetetraacetate (Zn-EDTA) or an inorganic zinc sulfate heptahydrate (ZnSO₄·7H₂O) Zn source was banded below the seedbed or broadcasted into soil. Compared with ZnSO₄·7H₂O, Zn-EDTA fertilization produced higher Zn concentration and uptake in wheat plants. However, Zn bioavailability in grain remained low, with [phytate]/[Zn] ratio >15 and the resulting estimated dietary total absorbed zinc (TAZ) < 3 mg Zn/d. ZnSO₄ banded into soil had little short-term effect on grain Zn concentration but had a high residual effect and promoted the maintenance of a high concentration of the Zn fraction bound to loose organic matter (LOM-Zn) in rhizosphere soil. Both ZnSO₄ and Zn-EDTA were more efficient if uniformly mixed through the soil than if banded to soil. Both ZnSO₄ and Zn-EDTA had limited effects on Zn bioavailability in wheat plants due to the high rate of Zn fixation in this calcareous soil.

Geochemical fractions and phytoavailability of Zinc in a contaminated calcareous soil affected by biotic and abiotic amendments

Many studies have conducted to determine the best management practice to reduce the mobility and phytoavailability of the trace metals in contaminated soils. In this study, geochemical speciation and phytoavailability of Zn for sunflower were studied after application of nanoparticles (SiO₂ and zeolite, with an application rate of 200 mg kg^-1) and bacteria [Bacillus safensis FO-036b(T) and Pseudomonas fluorescens p.f.169] to a calcareous heavily contaminated soil. Results showed that the biotic and abiotic treatments significantly reduced the Zn concentration in the aboveground to non-toxicity levels compared to the control treatment, and the nanoparticle treatments were more effective than the bacteria and control treatments. The concentration of CaCl₂-extractable Zn in the treated soils was significantly lower than those of the control treatment. The results of sequential extraction showed that the maximum portion of total Zn belonged to the fraction associated with iron and manganese oxides. On the contrary, the minimum percent belonged to the exchangeable and water-soluble Zn (F₁). From the environmental point of view, the fraction associated with iron and manganese oxides is less bioavailable than the F₁ and carbonated fractions. On the basis of plant growth promotion, simultaneous application of the biotic and abiotic treatments significantly increased the aboveground dry biomass yield and also significantly reduced the CaCl₂-extractable form, uptake by aboveground and translocation factor of Zn compared to the control treatment. Therefore, it might be suggested as an efficient strategy to promote the plant growth and reduce the mobile and available forms of toxic metals in calcareous heavily contaminated soils.

Root Engineering in Barley: Increasing Cytokinin Degradation Produces a Larger Root System, Mineral Enrichment in the Shoot and Improved Drought Tolerance

Root size and architecture are important crop plant traits, as they determine access to water and soil nutrients. The plant hormone cytokinin is a negative regulator of root growth and branching. Here, we generated transgenic barley (Hordeum vulgare) plants with an enlarged root system by enhancing cytokinin degradation in roots to explore the potential of cytokinin modulations in improving root functions. This was achieved through root-specific expression of a CYTOKININ OXIDASE/DEHYDROGENASE gene. Enhanced biomass allocation to roots did not penalize shoot growth or seed yield, indicating that these plants were not source limited. In leaves of transgenic lines, the concentrations of several macroelements and microelements were increased, particularly those with low soil mobility (phosphorus, manganese, and zinc). Importantly, seeds contained up to 44% more zinc, which is beneficial for human nutrition. Transgenic lines also demonstrated dampened stress responses to long-term drought conditions, indicating lower drought sensitivity. Taken together, this work demonstrates that root engineering of cereals is a promising strategy to improve nutrient efficiency, biofortification, and drought tolerance.

Tolerance and bioaccumulation of combined copper, zinc, and cadmium in Sesuvium portulacastrum

Sesuvium portulacastrum was treated with mixture of copper, zinc, and cadmium for 60 days, with the concentration of each metal ranging from 0 to 20 mg/L. The tolerance of plants and bioaccumulation of heavy metals were then investigated. The height of S. portulacastrum decreased significantly with increasing heavy metal concentrations from 1 to 20 mg/L. The biomass was adversely impacted when the concentration exceeded 5 mg/L. There were no significant differences in malondialdehyde (MDA) concentration among different treatment groups, while the soluble protein content and superoxide dismutase (SOD) activity decreased with increasing heavy metal concentration. However, the BCF values of the three metals were all higher than 10 and the tolerance in root was up to 1000 mg/kg without causing significant growth inhibition, suggesting that S. portulacastrum should be a potential candidate for phytostabilization for the phytoremediation of polymetallic contaminations in coastal environments.

Metal transport capabilities of anticancer copper chelators

In the present study, several Cu chelators [2,2'-biquinoline, 8-hydroxiquinoline (oxine), ammonium pyrrolidinedithiocarbamate (APDTC), Dp44mT, dithizone, neocuproine] were used to study Cu uptake, depletion and localization in different cancer cell lines. To better understand the concentration dependent fluctuations in the Cu intracellular metal content and Cu-dependent in vitro antiproliferative data, the conditional stability constants of the Cu complex species of the investigated ligands were calculated. Each investigated chelator increased the intracellular Cu content on HT-29 cells causing Cu accumulation depending on the amount of the free Cu(II). Copper accumulation was 159 times higher for Dp44mT compared to the control. Investigating a number of other transition metals, intracellular accumulation of Cd was observed only for two chelators. Intracellular Zn content slightly decreased (cca. 10%) for MCF-7 cells, while a dramatic decrease was observed on MDA-MB-231 ones (cca. 50%). A similar decrease was observed for HCT-116, while Zn depletion for HT-29 corresponded to cca. 20%. The IC₅₀ values were registered for the investigated four cell lines at increasing external Cu(II) concentration, namely, MDA-MB-231 cells had the lowest IC₅₀ values for Dp44mT ranging between 7 and 35 nM. Thus, Zn depletion could be associated with lower IC₅₀ values. Copper depletion was observed for all ligands being less pronounced for Dp44mT and neocuproine. Copper localization and its colocalization with Zn were determined by μ-XRF imaging. Loose correlation (0.57) was observed for the MCF-7 cells independently of the applied chelator. Similarly, a weak correlation (0.47) was observed for HT-29 cells treated with Cu(II) and oxine. Colocalization of Cu and Zn in the nucleus of HT-29 cells was observed for Dp44mT (correlation coefficient of 0.85).

Trace metal mobilization by organic soil amendments: insights gained from analyses of solid and solution phase complexation of cadmium, nickel and zinc

The accumulation of Cd in soils worldwide has increased the demand for methods to reduce the metal's plant bioavailability. Organic matter rich soil amendments have been shown to be effective in achieving this. However, it is not known how long these amendments can retain the Cd, and whether dissolved organic matter (DOM) released from them can enhance the metal's mobility in the environment. In this study we sought to test the Cd binding capacity of various organic soil amendments, and evaluate differences in characteristics of the DOM released to see if they can explain the lability of the Cd-DOM complexes. We collected ten organic soil amendments from around New Zealand: five different composts, biosolids from two sources, two types of peat and spent coffee grounds. We characterised the amendments' elemental composition and their ability to bind the Cd. We then selected two composts and two peats for further tests, where we measured the sorption of Ni or Zn by the amendments. We analysed the quality of the extracted DOM from the four amendments using 3D Excitation Emission Matrix analysis, and tested the lability of the metal-DOM complexes using an adapted diffusive gradients in thin-films (DGT) method. We found that composts bound the most Cd and that the emergent Cd-DOM complexes were less labile than those from the peats. Ni-DOM complexes were the least labile. The aromaticity of the extracted DOM appears to be an important factor in determining the lability of Ni complexes, but less so for Zn and Cd.