High Concentrations Of Zn2 Research Articles

Feasibility Insights of the Green-Assisted Calcium-Phosphate Coating on Biodegradable Zinc Alloys for Biomedical Application: In Vitro and In Vivo Studies.

In the field of bone tissue engineering, recently developed Zn alloy scaffolds are considered potential candidates for biodegradable implants for bone regeneration and defect reconstruction. However, the clinical success of these alloys is limited due to their insufficient surface bioactivities. Further, the higher concentration of Zn2+ produced during degradation promotes antibacterial activity, but deteriorates osteogenic properties. This study fabricated an Azadirachta indica (neem)-assisted brushite-hydroxyapatite (HAp) coating on the recently developed Zn-2Cu-0.5Mg alloy to tackle the above dilemma. The microstructure, degradation behavior, antibacterial activity, and hemocompatibility, along with in vitro and in vivo cytocompatibility of the coated alloys, are systematically investigated. Microstructural analysis reveals flower-like morphology with uniformly grown flakes for neem-assisted deposition. The neem-assisted deposition significantly improves the adhesion strength from 12.7 to 18.8 MPa, enhancing the mechanical integrity. The potentiodynamic polarization study shows that the neem-assisted deposition decreases the degradation rate, with the lowest degradation rate of 0.027 mm/yr for the ZHN2 sample. In addition, the biomineralization process shows the apatite formation on the deposited coating after 21 days of immersion. In vitro cytotoxicity assay exhibits the maximum cell viability of 117% for neem-assisted coated alloy in 30% extract after 5d and the improved cytocompatibility which is due to the controlled release of Zn2+ ions. Meanwhile, neem-assisted coated alloy increases the ZOI by 32 and 24% for Gram-positive and Gram-negative bacteria, respectively. Acceptable hemolysis (<5%) and anticoagulation parameters demonstrate a promising hemocompatibility of the coated alloy. In vivo implantation illustrates a slight inflammatory response and vascularization after 2 weeks of subcutaneous implantation, and neo-bone formation in the defect areas of the rat femur. Micro-CT and histology studies demonstrate better osseointegration with satisfactory biosafety response for the neem-assisted coated alloy as compared to that without neem-assisted deposition. Hence, this neem-assisted brushite-Hap coating strategy elucidates a new perspective on the surface modification of biodegradable implants for the treatment of bone defects.

The Effects of Zinc on Proprioceptive Sensory Function and Nerve Conduction.

Zinc (Zn2+) is an essential element that can promote proper organ function, cell growth, and immune response; it can also, however, be present in too great a quantity. Zinc toxicity caused by overexposure may result in both minor and major physiological effects, with chronic exposure at low levels and acute exposure at high levels being harmful or even toxic. This investigation examines the effects of acute exposure to relatively high concentrations of Zn2+ on sensory nerve function and nerve conduction. A proprioceptive nerve in marine crab (Callinectes sapidus) limbs was used as a model to assess the effects of Zn2+ on stretch-activated channels (SACs) and evoked nerve conduction. Exposure to Zn2+ slowed nerve condition rapidly; however, several minutes were required before the SACs in sensory endings were affected. A depression in conduction speed and an increase followed by a decrease in amplitude were observed for the evoked compound action potential, while the frequency of nerve activity upon joint movement and stretching of the chordotonal organ significantly decreased. These altered responses could be partially reversed via extensive flushing with fresh saline to remove the zinc. This indicates that subtle, long-term exposure to Zn2+ may alter an organism's SAC function for channels related to proprioception and nerve conduction.

Mechanism of Zn2+ regulation of cellulase production in Trichoderma reesei Rut-C30

BackgroundTrichoderma reesei Rut-C30 is a hypercellulolytic mutant strain that degrades abundant sources of lignocellulosic plant biomass, yielding renewable biofuels. Although Zn2+ is an activator of enzymes in almost all organisms, its effects on cellulase activity in T. reesei have yet to be reported.ResultsAlthough high concentrations of Zn2+ severely suppressed the extension of T. reesei mycelia, the application of 1–4 mM Zn2+ enhanced cellulase and xylanase production in the high-yielding cellulase-producing Rut-C30 strain of T. reesei. Expression of the major cellulase, xylanase, and two essential transcription activator genes (xyr1 and ace3) increased in response to Zn2+ stimulation. Transcriptome analysis revealed that the mRNA levels of plc-e encoding phospholipase C, which is involved in the calcium signaling pathway, were enhanced by Zn2+ application. The disruption of plc-e abolished the cellulase-positive influence of Zn2+ in the early phase of induction, indicating that plc-e is involved in Zn2+-induced cellulase production. Furthermore, treatment with LaCl3 (a plasma membrane Ca2+ channel blocker) and deletion of crz1 (calcineurin-responsive zinc finger transcription factor 1) indicated that calcium signaling is partially involved in this process. Moreover, we identified the zinc-responsive transcription factor zafA, the transcriptional levels of which declined in response to Zn2+ stress. Deletion of zafA indicates that this factor plays a prominent role in mediating the Zn2+-induced excessive production of cellulase.ConclusionsFor the first time, we have demonstrated that Zn2+ is toxic to T. reesei, although promotes a marked increase in cellulase production. This positive influence of Zn2+ is facilitated by the plc-e gene and zafA transcription factor. These findings provide insights into the role of Zn2+ in T. reesei and the mechanisms underlying signal transduction in cellulase synthesis.

The preparation and effect of Sr-doped phosphate coatings on the ion release and cytocompatibility of biodegradable zinc

The high concentration of Zn2+ ion locally released due to the degradation of zinc (Zn) implants causes cytotoxicity, hindering the clinical application of Zn. Herein, bioactive Sr2+ doped zinc phosphate (Sr-P) coatings were prepared by a feasible chemical conversion method to improve the biocompatibility of biomedical Zn. The reaction thermodynamics were regulated by different reaction parameters to further regulate the chemical composition and surface morphology, and in vitro release of metal ions of the Sr-P coatings. The Sr-P coating with the most obvious inhibition effect on Zn2+ ion release was selected for the in vitro cell assays. Sr-P coating presents a promising surface modification strategy to improve biocompatibility for biodegradable Zn.

Extending Ag Nanoparticles as Colorimetric Sensor to Industrial Zinc Electrolyte for Cobalt Ion Detection

The direct and rapid determination of trace cobalt ion (Co2+) in the electrolyte of zinc smelting plants is urgently needed but is impeded by the severe interference of extremely high-concentration zinc ions in the solution. Herein, colorimetric detection of Co2+ by the polyvinylpyrrolidone functionalized silver nanoparticles (PVP-AgNPs) is realized in solutions with the Zn/Co ratio being high, up to (0.8-5) × 104, which is located within the ratio range in industrial solution. The high concentration of Zn2+ induces a strong attenuation of Co2+-related signals in ultraviolet-visible (UV-vis) extinction spectra; nevertheless, a good linear range for detecting 1-6 mg/L Co2+ in 50 g/L Zn2+ solution is still acquired. The strong anti-interference toward other metal ions and the mechanism understanding for trace Co2+ detection in such a high-concentration Zn2+ solution are also revealed by systematic analysis techniques. The results extend the AgNPs as colorimetric sensors to industrial solutions, providing a new strategy for detecting trace-metal ions in industrial plants.

Study of zinc salt concentration effect on the growth of zno nanostructured oxides obtained by direct electrodeposition

"Effect of zinc salt concentration on the growth of electrodeposited zinc oxide phases was investigated. ZnO thin films were elaborated via chronoamperometry on fluorine doped tin oxide (FTO) substrates from aqueous mixed bath of zinc nitrate and chlorate at 70°C. X ray diffraction patterns showed nanocrystalline films of hexagonal wurtzite phase with (101) preferential orientation for ZnO as grown in low concentration of Zn2+ salt. High concentration of Zn2+ favor the formation of Zn5(OH)8Cl2H2O simonkolleite phase. After heat treatment at 400 °C for 1h this later decomposes to ZnO oxide which presents no preferential orientation. The route mean square RMS roughness of surfaces estimated from AFM technique shows that ZnO generated from heat treated Zn5(OH)8Cl2H2O present more increasing roughness than ZnO deposits obtained at lower salt concentration. The photoelectrochemical answer indicated important generated photocurrents for both films which present n-type electrical conductivity"

Zinc and copper supplements enhance trichloroethylene removal by Pseudomonas plecoglossicida in water

ABSTRACT The effects of two microelements, zinc and copper, on the aerobic co-metabolic removal of trichloroethylene (10 mg/L) by the isolate Pseudomonas plecoglossicida were investigated. The strain was previously isolated from a petroleum-contaminated site using toluene (150 mg/L) as substrate. Different concentrations (1, 10 and 100 mg/L) of microelements provided with SO4 2− and Cl− were tested. The results showed the supplement of Zn2+ and Cu2+ at the low concentration (1 mg/L) significantly enhanced cell growth. The removal efficiencies for toluene and trichloroethylene were also enhanced at the low concentration (1 mg/L) of Zn2+ and Cu2+. Compared to the control without zinc supplement, higher concentrations of zinc (10 and 100 mg/L) enhanced the removal efficiencies for both toluene and trichloroethylene in the first three days but showed some inhibitory effect afterward. However, the higher concentrations of Cu2+ (10 and 100 mg/L) always showed inhibitory to the toluene removal while showing inhibitory to the TCE removal after three days. For both Zn2+ and Cu2+, the anions SO4 2− and Cl− did not show significant difference in their effects on the toluene removal. A possible mechanism for Zn2+ and Cu2+ to enhance the removal of toluene and trichloroethylene would be their involvement in toluene oxygenase-based transformation processes. In addition, high concentrations of Zn2+ and Cu2+ ions could be removed from the liquid by the cells accordingly. The results imply a potential of supplementing low concentrations of zinc and copper to enhance bioremediation of the sites co-contaminated with toluene and trichloroethylene.

Zinc Anodes Modified by One-Molecular-Thick Self-Assembled Monolayers for Simultaneous Suppression of Side-Reactions and Dendrite-Formation in Aqueous Zinc-Ion Batteries.

Repeated charge/discharge in aqueous zinc-ion batteries (ZIBs) commonly results in surface corrosion/passivation and dendrite formation on zinc anodes, which is a major challenge for the commercialization of zinc-based batteries. In this work, metallic Zn modified by self-assembled monolayers is described as a viable anode for ZIBs. ω-mercaptoundecanoic acid that is spontaneously adsorbed on Zn (MUDA/Zn) contributes to the simultaneous suppression of side reactions and dendrite formation in ZIBs. Though one-molecular-thick, densely packed alkyl chains prohibit H2 O and H+ from making direct contact with the underlying Zn, and surface carboxylate moieties (-COO- ) effectively repel anionic species (OH- ) in a solution, which renders a Zn anode inert against zincate formation within a wide range of pH. In contrast, the electrostatic attraction between surface-carboxylates and cations increases the concentration of Zn2+ on the surface of MUDA/Zn to facilitate Zn plating/stripping with less overpotentials. The high concentration of Zn2+ also results in an increased number of nucleation sites, which enhances the lateral growth of Zn with no formation of dendrites. As a result, MUDA/Zn shows excellent stability during prolonged Zn plating/stripping within a wide range of pH. The advantageous properties of MUDA/Zn are also retained in full-cells coupled with δ-MnO2 cathodes.

Multivariable Analysis of Electrodeposited Silane/Zinc Coating—Improvement of Cathodic Protection of Steel

In order to enhance corrosion protection efficiency of electrodeposited sol–gel zinc/silica coatings, this paper resorted to a central composite design as a tool to improve cathodic protection effectiveness time and electrochemical tests to understand the film protection mechanism. Coatings were produced by electrodeposition of a mixture of tetraethoxysilane (TEOS) and Zn2+ onto carbon steel. The amount of silane agent, concentration of zinc nitrate and the applied potential were chosen as the variables to be studied. Open-circuit potentials in NaCl 3.5% (wt.) solution were monitored to verify the duration of cathodic protection, according to ISO 15589-2:201. Microstructures characterization and distribution of deposited zinc were determined by scanning electron microscopy and energy-dispersive x-ray spectroscopy. At last, coating degradation was analyzed by potentiodynamic polarization curves, electrochemical impedance spectroscopy and visual inspection of corrosion products. Results revealed films whose cathodic protection endured more than 600 min of immersion when higher concentrations of Zn2+ were combined with lower potentials and lower silane content. Furthermore, visual inspection of immersed specimens showed no corrosion signs for carbon steel samples deposited with zinc and TEOS, even after 20 h, providing a superior protection when compared to the sample deposited solely with zinc.

Impact of Acetyl Acetone on Zinc Uptake and Oxidative Stress in Cucumber (Cucumis sativus)

The purpose of this research is to determine the impacts of acetyl acetone on zinc uptake and oxidative stress in cucumber (Cucumis sativus) seedlings grown in hydroponic solutions. Thirty seedlings of cucumber were collected from Kura local government area Kano, Kano state. Concentrations of Zn2+ in the hydroponics were varied from 0.000 to 0.025 mol dm-3 and of acetyl acetone were also varied from 0.000 to 0.025 mol dm-3. The seedlings were replanted and kept at Department of Agriculture Kano University of Science and Technology, Wudil garden. The weight of plants increased significantly (p&lt;0.05) with concentration of Zn2+ in the absence of acetyl acetone and highly insignificantly (p&gt;0.05) with concentration of acetyl acetone in the absence of Zn2+. In the presence of acetyl acetone and Zn2+ plant weight decreased highly insignificant (p&gt;0.05). Leaf fall was observed from plants in all hydroponic, the number of falling leaves was insignificant (p&gt;0.05) with concentration of Zn2+ but it is insignificant (p&gt;0.05) with concentration of acetyl acetone and highly insignificant in the presence of acetyl acetone and Zn2+ (p&gt;0.05). The volume of the solution decreased highly significant (p&lt;0.05) with concentration of Zn2+ and significant with concentration of acetyl acetone (p&lt;0.05) the volume also increased insignificantly in the presence of acetyl acetone and Zn2+ (p&gt;0.05). The pH values of treated hydroponics before replanting and after harvest were insignificant with increased in the concentration of Zn2+ (p&gt;0.05). Both shoot and root zinc accumulated were insignificant at lower concentration of Zn2+ (p&gt;0.05) and significant at higher concentration of Zn2+ (p&lt;0.05). The zinc translocation factor decreased highly insignificantly (p&gt;0.05) at lower concentration of Zn2+ and significant at higher concentration of Zn2+ (p&gt;0.05) in treated plants compared to control. The chlorophyll, carotenoid and proline content varied in the presence and absence of acetyl acetone and or combination of the two, with (p&lt;0.05) or (p&gt;0.05).

The Vacuolar Zinc Transporter TgZnT Protects Toxoplasma gondii from Zinc Toxicity.

Zinc (Zn2+) is the most abundant biological metal ion aside from iron and is an essential element in numerous biological systems, acting as a cofactor for a large number of enzymes and regulatory proteins. Zn2+ must be tightly regulated, as both the deficiency and overabundance of intracellular free Zn2+ are harmful to cells. Zn2+ transporters (ZnTs) play important functions in cells by reducing intracellular Zn2+ levels by transporting the ion out of the cytoplasm. We characterized a Toxoplasma gondii gene (TgGT1_251630, TgZnT), which is annotated as the only ZnT family Zn2+ transporter in T. gondii TgZnT localizes to novel vesicles that fuse with the plant-like vacuole (PLV), an endosome-like organelle. Mutant parasites lacking TgZnT exhibit reduced viability in in vitro assays. This phenotype was exacerbated by increasing zinc concentrations in the extracellular media and was rescued by media with reduced zinc. Heterologous expression of TgZnT in a Zn2+-sensitive Saccharomyces cerevisiae yeast strain partially restored growth in media with higher Zn2+ concentrations. These results suggest that TgZnT transports Zn2+ into the PLV and plays an important role in the Zn2+ tolerance of T. gondii extracellular tachyzoites.IMPORTANCEToxoplasma gondii is an intracellular pathogen of human and animals. T. gondii pathogenesis is associated with its lytic cycle, which involves invasion, replication, egress out of the host cell, and invasion of a new one. T. gondii must be able to tolerate abrupt changes in the composition of the surrounding milieu as it progresses through its lytic cycle. We report the characterization of a Zn2+ transporter of T. gondii (TgZnT) that is important for parasite growth. TgZnT restored Zn2+ tolerance in yeast mutants that were unable to grow in media with high concentrations of Zn2+ We propose that TgZnT plays a role in Zn2+ homeostasis during the T. gondii lytic cycle.

Zinc Ions Affect Siderophore Production by Fungi Isolated from the Panax ginseng Rhizosphere.

Although siderophore compounds are mainly biosynthesized as a response to iron deficiency in the environment, they also bind with other metals. A few studies have been conducted on the impact of heavy metals on the siderophore-mediated iron uptake by microbiome. Here, we investigated siderophore production by a variety of rhizosphere fungi under different concentrations of Zn²⁺ ion. These strains were specifically isolated from the rhizosphere of Panax ginseng (Korean ginseng). The siderophore production of isolated fungi was investigated with chrome azurol S (CAS) assay liquid media amended with different concentrations of Zn²⁺ (50 to 250 μg/ml). The percentage of siderophore units was quantified using the ultra-violet (UV) irradiation method. The results indicated that high concentrations of Zn²⁺ ion increase the production of siderophore in iron-limited cultures. Maximum siderophore production by the fungal strains was detected at Zn²⁺ ion concentration of 150 μg/ml except for Mortierella sp., which had the highest siderophore production at 200 μg/ml. One potent siderophore-producing strain (Penicillium sp. JJHO) was strongly influenced by the presence of Zn²⁺ ions and showed high identity to P. commune (100% using 18S-rRNA sequencing). The purified siderophores of the Penicillium sp. JJHO strain were chemically identified using UV, Fourier-transform infrared spectroscopy (FTIR), and matrix-assisted laser desorption/ionization time-of-flight mass spectrometer (MALDI-TOF-MS) spectra.

Bacterial Growth and Death on Cotton Fabrics Conformally Coated with ZnO Thin Films of Varying Thicknesses via Atomic Layer Deposition (ALD)

Hospital fabrics are commonly exposed to multiple patients and contaminated surfaces between washing/sterilization cycles. Consequently, these textiles act as vectors for the spread of diseases, especially bacterial pathogens. Many modification schemes have been proposed to mitigate the growth and spread of bacteria on fabrics, including use of antimicrobial metal oxide nanoparticles. The aim of this study is to examine the effectiveness of conformal nanoscale ZnO coatings applied to cotton fabrics via atomic layer deposition to control bacterial spread. We find that, at low ZnO loading fractions, bacteria metabolize Zn2+ ions and reproduce more rapidly. However, as the ZnO loading is increased, the higher concentrations of Zn2+ overwhelm the bacteria and the nanocoatings become effective antibacterial treatments, killing all bacteria present. These results map out an important design space for implementing ZnO coatings as a potential antimicrobial treatment for textiles and other surfaces.

Understanding the Endogenous Inhibition of IAPP Aggregation

Amyloid aggregation of islet amyloid polypeptide (IAPP) is associated with β-cell death in type-2 diabetes (T2D)[1]. IAPP readily forms amyloid fibrils in vitro at μM concentrations. However, no apparent IAPP aggregates are observed in healthy individuals where IAPP is stored in β-cell granules at mM concentrations. Therefore, physiological conditions of β-cell granules endogenously inhibit the amyloid aggregation of IAPP. Disruption of the inhibitive environment of β-cell granules may lead to the accumulation of toxic IAPP aggregates, causing β-cell death in T2D. The cellular environment of beta-cell granules is unique in its high concentrations of Zn2+, insulin and proinsulin c-peptide. Combining discrete molecular dynamics simulations with experimental characterizations and validations, we have investigated both the effects of individual molecules and also their cooperative effects on IAPP aggregation. For example, insulin inhibits IAPP aggregation by competing for the amyloid core around residues 22-29 with its B-chain[2]. Depending on relative concentrations, zinc either promotes or inhibits IAPP aggregation by changing distributions of zinc-coordinated IAPP oligomers with distinct aggregation propensities[3]. Zinc and C-peptide synergistically inhibits IAPP aggregation by stabilizing IAPP in an aggregation-incompetent state upon the formation of zinc-coordinated molecular complex with C-peptide[4]. These mechanistic insights to the endogenous inhibition of IAPP aggregation may help design novel therapeutic strategies that either mimic or promote the native inhibition of IAPP aggregation.

Determination of Cadmium in Brown Rice Samples by Fluorescence Spectroscopy Using a Fluoroionophore after Purification of Cadmium by Anion Exchange Resin.

Simple analytical methods are needed for determining the cadmium (Cd) content of brown rice samples. In the present study, we developed a new analytical procedure consisting of the digestion of rice using HCl, Cd purification using anion exchange resin, and then determining the Cd content using fluorescence spectroscopy. Digestion with 0.1 M HCl for 10 min at room temperature was sufficient to extract Cd from the ground rice samples. The Cd in the extract was successfully purified in preference to other metals using Dowex 1X8 chloride form resin. Low concentrations of Cd in the eluate could be determined using fluorescence spectroscopy with a fluoroionophore. Overall, the actual limit of quantification value for the Cd content in rice was about 0.1 mg-Cd/kg-rice, which was sufficiently low compared with the regulatory value (0.4 mg-Cd/kg-rice) given by the Codex Alimentarius Commission. We analyzed authentic brown rice samples using our new analytical procedure and the results agreed well with those determined using inductively coupled plasma optical emission spectrometry (ICP-OES). Since the fluoroionophore recognized Zn2+ and Hg2+ as well as Cd2+, a sample containing high concentration of Zn2+ or Hg2+ might cause a false positive result.

In Vitro Evaluation of the Feasibility of Commercial Zn Alloys as Biodegradable Metals

In this work, three widely used commercial Zn alloys (ZA4-1, ZA4-3, ZA6-1) were purchased and prepared by hot extrusion at 200 °C. The microstructure, mechanical properties, corrosion behaviors, biocompatibility and hemocompatibility of Zn alloys were studied with pure Zn as control. Commercial Zn alloys demonstrated increased strength and superb elongation compared with pure Zn. Accelerated corrosion rates and uniform corrosion morphologies were observed in terms of commercial Zn alloys due to galvanic effects between Zn matrix and α-Al phases. 100% extracts of ZA4-1 and ZA6-1 alloys showed mild cytotoxicity while 50% extracts of all samples displayed good biocompatibility. Retardant cell cycle and inhibited stress fibers expression were observed induced by high concentration of Zn2+ releasing during corrosion. The hemolysis ratios of Zn alloys were lower than 1% while the adhered platelets showed slightly activated morphologies. In general, commercial Zn alloys possess promising mechanical properties, appropriate corrosion rates, significantly improved biocompatibility and good hemocompatibility in comparison to pure Zn. It is feasible to develop biodegradable metals based on commercial Zn alloys.

Purification, characterization, and cDNA cloning of a matrix metalloproteinase from the skeletal muscle of silver carp (Hypophthalmichthys molitrix) with collagen degradation activity

A 72-kDa matrix metalloproteinase (MMP; sMP) was purified from silver carp skeletal muscle by 30–70% ammonium sulfate fractionation and chromatography. The sMP revealed high gelatinolytic activity from 30 to 60°C and showed an optimal pH of 8.0. The gelatin-hydrolyzing activity of sMP was inhibited by ethylenediaminetetraacetic acid (EDTA), dithiothreitol (DTT), l-Cys, and l-His. Ca2+ enhanced the proteinase activity, while a higher concentration of Zn2+ inhibited this activity. Peptide mass fingerprinting revealed that 14 fragments were identical to MMP-2 from grass carp (Ctenopharyngodon idella). The full length of the cDNA sequence encoding sMP was 3005bps, with an open reading frame (ORF) of 1977 bps encoding 658 amino acid residues. Further, sMP could effectively hydrolyze type I collagen even at 4°C; its activity remained steady during the entire storage period at 4°C. These results indicated that sMP is MMP-2 and may have been involved in the protein degradation of fish muscle during the postmortem stage.

Endothelial Cellular Responses to Biodegradable Metal Zinc.

Biodegradable zinc (Zn) metals, a new generation of biomaterials, have attracted much attention due to their excellent biodegradability, bioabsorbability, and adaptability to tissue regeneration. Compared with magnesium (Mg) and iron (Fe), Zn exhibits better corrosion and mechanical behaviors in orthopedic and stent applications. After implantation, Zn containing material will slowly degrade, and Zn ions (Zn2+) will be released to the surrounding tissue. For stent applications, the local Zn2+concentration near endothelial tissue/cells could be high. However, it is unclear how endothelia will respond to such high concentrations of Zn2+, which is pivotal to vascular remodeling and regeneration. Here, we evaluated the short-term cellular behaviors of primary human coronary artery endothelial cells (HCECs) exposed to a concentration gradient (0-140 μM) of extracellular Zn2+. Zn2+ had an interesting biphasic effect on cell viability, proliferation, spreading, and migration. Generally, low concentrations of Zn2+ promoted viability, proliferation, adhesion, and migration, while high concentrations of Zn2+ had opposite effects. For gene expression profiles, the most affected functional genes were related to cell adhesion, cell injury, cell growth, angiogenesis, inflammation, vessel tone, and coagulation. These results provide helpful information and guidance for Zn-based alloy design as well as the controlled release of Zn2+in stent and other related medical applications.

Zn(II)-concentration dependent Raman spectra in the dithizone complex on gold nanoparticle surfaces in environmental water samples

After the formation of dithizone with metal ion complexes, a selective Raman detection method for the Zn2+ ions in aqueous solutions was developed by observing the intensity change of the ring mode peaks at ∼1585cm−1 on gold nanoparticles (AuNPs). At high concentrations of Zn2+ ions, the conformation of the dithizone complex may have different orientations on AuNPs to yield the spectral changes at ca. ∼510 and ∼1585cm−1. The concentration dependent spectra changes indicated that a detection limit would be in the submicromolar region of Zn2+ ions. The other ions of Mg2+, K+, Fe3+, Hg2+, Co2+, Fe2+, Pb2+, Cu2+, Ni2+, Cr3+, NH4+, Cd2+, Na+, Ca2+, and Mn2+ at micromolar concentrations of 1μM did not produce such spectral changes. The detection limit based on the Raman band intensities was estimated to be as low as 500nM of Zn2+ ion in aqueous solutions. The three real samples of tap, river, and seawater were tested under the interference of the commonly existing interfering ions. Despite the presence of highly concentrated Na, Ca, Mg, and K, our interfacial spectroscopic methodology of Zn2+ determination could be applied in the environmental water samples.

Synthesis of Zinc Phosphonated Poly(ethylene imine) and Its Fire-Retardant Effect in Low-Density Polyethylene

A novel oligomeric intumescent fire-retardant chelate, zinc phosphonated poly(ethylene imine) (Zn-PEIP), with a variable Zn2+ loading, was synthesized. The chemical structure of Zn-PEIP was confirmed by FTIR, 13C NMR, and 31P NMR spectroscopies. The thermal behavior and fire retardancy of low-density polyethylene (LDPE) containing 25 wt % Zn-PEIPs with different amounts of Zn2+ were investigated by thermogravimetric analysis (TGA), limiting oxygen index (LOI) measurements, and cone calorimetry. The TGA results showed that higher concentrations of Zn2+ improved the thermal stability and increased the residue yield of LDPE. However, the data from the LOI and cone calorimetry tests showed that there is an optimum concentration of Zn2+ for the best fire-retardancy performance of LDPE. This behavior is ascribed to the high cross-link density resulting from zinc bridges, preventing normal swelling of the intumescent system. The surface morphology of the char was characterized by digital photography and scanning...