Toxic Ions Research Articles

Physiological and Transcriptional Analyses Provide Insight into Maintaining Ion Homeostasis of Sweet Sorghum under Salt Stress

Sweet sorghum is an important bioenergy grass and valuable forage with a strong adaptability to saline environments. However, little is known about the mechanisms of sweet sorghum coping with ion toxicity under salt stresses. Here, we first evaluated the salt tolerance of a sweet sorghum cultivar “Lvjuren” and determined its ion accumulation traits under NaCl treatments; then, we explored key genes involved in Na+, Cl−, K+ and NO3− transport using transcriptome profiling and the qRT-PCR method. The results showed that growth and photosynthesis of sweet sorghum were unaffected by 50 and 100 mM NaCl treatments, indicative of a strong salt tolerance of this species. Under NaCl treatments, sweet sorghum could efficiently exclude Na+ from shoots and accumulate Cl− in leaf sheaths to avoid their overaccumulation in leaf blades; meanwhile, it possessed a prominent ability to sustain NO3− homeostasis in leaf blades. Transcriptome profiling identified several differentially expressed genes associated with Na+, Cl−, K+ and NO3− transport in roots, leaf sheaths and leaf blades after 200 mM NaCl treatment for 6 and 48 h. Moreover, transcriptome data and qRT-PCR results indicated that HKT1;5, CLCc and NPF7.3-1 should be key genes involved in Na+ retention in roots, Cl− accumulation in leaf sheaths and maintenance of NO3− homeostasis in leaf blades, respectively. Many TFs were also identified after NaCl treatment, which should play important regulatory roles in salt tolerance of sweet sorghum. In addition, GO analysis identified candidate genes involved in maintaining membrane stability and photosynthetic capacity under salt stresses. This work lays a preliminary foundation for clarifying the molecular basis underlying the adaptation of sweet sorghum to adverse environments.

A highly hydrophilic hydrazone-linked covalent organic framework as a fluorescent multianalyte sensor for detection of Cu2+ and Hg2+ in aqueous solution

Heavy metal pollution is of great threat to public health and the environment, and an effective method to detect and remove toxic heavy ions from water is highly desirable. The emerging covalent organic frameworks (COFs) with well-defined pore structures and specific functional units provide an excellent platform for fluorescent sensing. The hydrazone-linked framework material SH-COF with excellent hydrophilicity and abundant chelating sites was synthesized by bottom-up strategy under solvothermal conditions. The resultant SH-COF with specific binding sites was proposed to detect and remove Cu2+ and Hg2+. The SH-COF also exhibited the characteristics of high selectivity, high sensitivity, a lower limit of detection (0.244 μM for Cu2+ and 0.239 μM for Hg2+), and real-time response. Furthermore, the highly selective interaction of Cu2+ or Hg2+ with SH-COF was confirmed by X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy and Fourier transform infrared spectra. A proposed sensing mechanism of COF for Cu2+ and Hg2+ was presented. This research also demonstrates the great potential of COFs in practical sensing applications.

Low temperature sulfonated biochar from Macauba’s endocarp for lead adsorption from wastewater

Lead is a heavy metal that can be present in different types of effluents. This toxic ion is harmful both to human health and to other species. Therefore, it is necessary to study materials that can be used to remove lead from aquatic environments. In this context, the use of modified biomass residues for the production of efficient adsorbents for this purpose stands out. In this work was synthesized a new type of adsorbent material, sulfonated carbon, from macauba oil extraction residue for application in the removal of lead ions from aqueous media. The sulfonated carbons were produced from the reaction of macauba endocarp with concentrated sulfuric acid at 100 °C at 1, 2 and 4 h. The materials were characterized by XRD, MS-TG, Raman and infrared spectroscopies, SEM, potential titration, elemental analysis and by N2 adsorption/desorption. All synthetic conditions were efficient to produce functionalized carbonaceous materials with amorphous characteristics and good thermal stability. Although the material carbonized for 4 h had a low specific surface area (2 m2.g−1), it showed the higher efficiency for the removal of lead ions from aqueous solution. The adsorption occurred due to interactions of these ions with the functional groups present on the surface of the coal. The greatest lead removal occurred at pH 5.0 (83.8%), where –COOH and SO3H groups are in the deprotonated form, what favors the electrostatic attraction of Pb2+ ions. The experimental results were fitted using pseudo-first-order and pseudo-second-order models. A high concentration of lead ions was removed in the first 40 min, and the removal percentage was 97.5% for the less concentrated solution (10 mg·L−1) and 55.0% for the solution with the highest concentration (100 mg·L−1). The increase in the concentration of adsorbent provided an increase in the removal of this contaminant. The isotherm of adsorption was adjusted by Langmuir and Freundlich models. The better adjust was obtained by Langmuir and the maximum adsorption capacity by this model was 104.2 mg·g−1. The best lead removal conditions were: adsorbent concentration: 0.5 g.L−1; pH 5; Pb2+ concentration 80 mg.L−1 and time 2 h.

SALT STRESS IN FRUIT CROPS AND ITS MANAGEMENT

Due to the presence of excess soluble salt in the soil, soil salinity is a key abiotic stress and one of the major environmental issues affecting plant productivity, especially in arid and semi-arid areas. Salt damage typically shows up as leaf burn and defoliation and is linked to dangerous amounts of Na+ and/or Cl building up in leaf cells. The osmotic effect and/or excessive ion accumulation in the plant tissues, which may result in ionic toxicity and/or nutritional imbalance, are common causes of crop growth inhibition under saline circumstances. The degree to which any stress condition impacts a plant’s growth or development depends on a number of variables, including the kind of plant, cultivar, and phenological stage, the composition of the soluble salts, the intensity and duration of the stress, and the edaphoclimatic conditions.

Removal of Metal Ions via Adsorption Using Carbon Magnetic Nanocomposites: Optimization through Response Surface Methodology, Kinetic and Thermodynamic Studies

The toxicity of metal ions on ecosystems has led to increasing amounts of research on their removal from wastewater. This paper presents the efficient application of a carbon magnetic nanocomposite as an adsorbent for the elimination of metal ions (copper, lead and zinc) from aqueous solutions. A Box–Behnken factorial design combined with the response surface methodology was conducted to investigate the effect and interactions of three variables on the pollutant removal process. Highly significant (p < 0.001) polynomial models were developed for each metal ion: the correlation coefficient was 0.99 for Cu(II) and Pb(II), and 0.96 for Zn(II) ion removal. The experimental data were in agreement and close to the theoretical results, which supports the applicability of the method. Working at the natural pH of the solutions, with a quantity of carbon magnetic nanocomposite of 1 g/L and a metal ions’ concentration of 10 mg/L, for 240 min, removal efficiencies greater than 75% were obtained. The kinetic study indicated that a combination of kinetic models pseudo-second order and intraparticle diffusion were applied appropriately for copper, lead and zinc ion adsorption on carbon magnetic nanocomposite. The maximum adsorption capacities determined from the Langmuir isotherm model were 81.36, 83.54 and 57.11 mg/g for copper, lead and zinc ions. The average removal efficiency for five adsorption–desorption cycles was 82.21% for Cu(II), 84.50% for Pb(II) and 72.68% for Zn(II). The high adsorption capacities of metal ions, in a short time, as well as the easy separation of the nanocomposite from the solution, support the applicability of the magnetic carbon nanocomposite for wastewater treatment.

Enhanced Hg(II) efficient and selective removal by post-functional Ti-MOF with 2，5 thiophene dicarboxylic acid

Toxic mercury ions in wastewater from industrial activities can wreak havoc on the natural environment and ecosystems. Adsorption treatment has been proved to be an effective measure to reduce mercury load in wastewater, but conventional adsorbents have lower adsorption performance. In this study, titanium-metal organic framework (Ti-MOF) was synthesized by solvothermal method, and then further modified by 2,5-thiophene dicarboxylic acid. In order to explore the morphology of the resulting material (OB-MIL-125 (Ti)) and the differences before and after modification, different characterization instruments have been employed. Meanwhile, the properties of materials at different pH were explored, and the adsorption capacity was deeply studied through thermodynamics, kinetics, and adsorption isotherms. The surface of OB-MIL-125 (Ti) had a rich pore structure, so the specific surface area is large, reaching 328.7 m2/g. At room temperature and pH= 5, the maximum removal rate of a 100 ppm solution reached 93.66%. The actual measured maximum adsorption capacity was 1435.98 mg/g. According to isotherm, kinetic and thermodynamic analysis, the process of removing Hg2+ was a multi-layer heterogeneous process, relying on chemical action for adsorption, and it was also a spontaneous exothermic process. The adsorbent presented excellent affinity for mercury and good regeneration ability. To sum up, the OB-MIL-125 (Ti) has great potential for remediation mercury-containing wastewater.

Poly(ionic liquids)-functionalized metal-organic frameworks for sustainable water purification

Ion exchange adsorption has demonstrated great promise for the removal of toxic ion contaminants from wastewater. Here, by combining in situ polymerization and quaternization, we successfully fabricated a series of poly(ionic liquids)/aluminum-based metal-organic framework composites, DUT-5-(X)I. The optimized DUT-5-(60)I possesses relatively large surface area and abundant exchangeable free iodide ions, which endow this composite with highly efficient adsorption of anionic pollutants. Specifically, over 90% of permanganate, methyl blue and methyl orange can be removed within 10 min. In addition, effects of pH and coexisting ions on the removal of adsorbates were examined. Pseudo-second-order kinetics and Langmuir isotherm model can well describe the adsorption results. The Langmuir isotherm model based maximum adsorption capacities of DUT-5-(60)I for permanganate, methyl blue, and methyl orange reached up to 1132, 1548, and 1474 mg/g, respectively. Adsorption mechanism studies suggest that the removal of these adsorbates was mainly controlled by electrostatic adsorption. This study will provide new insights for the development of MOF-based materials for environmental remediation.

Toxicity of Metal Ions Released from a Fixed Orthodontic Appliance to Gastrointestinal Tract Cell Lines.

The mechanism of toxicity and cellular response to metal ions present in the environment is still a very current area of research. In this work, which is a continuation of the study of the toxicity of metal ions released by fixed orthodontic appliances, eluates of archwires, brackets, ligatures, and bands are used to test the prooxidant effect, cytotoxicity, and genotoxicity on cell lines of the gastrointestinal tract. Eluates obtained after three immersion periods (3, 7, and 14 days) and with known amounts and types of metal ions were used. Four cell lines-CAL 27 (human tongue), Hep-G2 (liver), AGS (stomach) and CaCo-2 (colon)-were treated with each type of eluate at four concentrations (0.1×, 0.5×, 1.0×, and 2.0×) for 24 h. Most eluates had toxic effects on CAL 27 cells over the entire concentration range regardless of exposure time, while CaCo-2 proved to be the most resistant. In AGS and Hep-G2 cells, all samples tested induced free radical formation, with the highest concentration (2×) causing a decrease in free radicals formed compared to the lowest concentrations. Eluates containing Cr, Mn, and Al showed a slight pro-oxidant effect on DNA (on plasmid φX-174 RF I) and slight genotoxicity (comet assay), but these effects are not so great that the human body could not "resist" them. Statistical analysis of data on chemical composition, cytotoxicity, ROS, genotoxicity, and prooxidative DNA damage shows the influence of metal ions present in some eluates on the toxicity obtained. Fe and Ni are responsible for the production of ROS, while Mn and Cr have a great influence on hydroxyl radicals, which cause single-strand breaks in supercoiled plasmid DNA in addition to the production of ROS. On the other hand, Fe, Cr, Mn, and Al are responsible for the cytotoxic effect of the studied eluates. The obtained results confirm that this type of research is useful and brings us closer to more accurate in vivo conditions.

A Simple Method to Fabricate the Highly Sensitive SERS Substrate by Femtosecond Laser-Based 3D Printer

Surface-enhanced Raman spectroscopy (SERS) is a potent technique for analyzing and detecting various targets, including toxic ions, pesticides, and biomarkers, at the single-molecule level. The efficiency of SERS techniques relies heavily on the underlying SERS substrate, which is primarily responsible for the strong induction of localized plasmon resonance on nanostructures. Noble metals such as gold and silver were commonly used to fabricate SERS substrates, leveraging the electromagnetic mechanism (EM) to enhance the Raman signal. However, chemically synthesized nanoparticle-based SERS substrates suffer from low uniformity and reproducibility. Furthermore, the high cost associated with noble metals makes most SERS substrates expensive to produce. In this study, we present a straightforward method for fabricating a highly uniform and reproducible SERS substrate using a femtosecond laser-based 3D printer. Notably, our method offers good cost competitiveness since it requires only a minimal amount of gold coating for the SERS signal. Moreover, the proposed method exhibits exceptional versatility in SERS analysis and detection, catering to numerous targets in the field.

Multicolor emission from lanthanide ions doped lead-free Cs3Sb2Cl9 perovskite nanocrystals

The toxicity of lead ions has become the severe challenge for the all-inorganic lead halide perovskite materials, although some works have reported the lead-free perovskite nanocrystals (NCs), the photoluminescence quantum yield (PLQY) of these materials is still unsatisfactory. Meanwhile, because the halogen ions can be easily exchanged, the controllable multicolor emission in perovskite NCs is difficult to realize in current reports. In this work, we introduced lanthanide ions into lead-free Cs3Sb2Cl9 perovskite NCs. Benefitting from the energy transfer between Cs3Sb2Cl9 perovskite NC host and lanthanide ions, the multicolor emission was realized. Based on controlling the doping concentration of Tb3+ and Eu3+ ions, the white light emission under UV excitation would be turned easily in the Tb3+/Eu3+ codoped NCs. In addition, efficient energy transfer from perovskite NCs to Tb3+ or Eu3+ ions is beneficial to improving the optical properties of lead-free perovskite NCs, resulting in maximum PLQYs of red, green and white light emission of 22.6%, 19.7% and 28.5%, respectively. Finally, a white light emitting device (WLED) was fabricated with a power efficiency of 18.5 lm/W, which presents the Commission Internationale de l’Eclairage (CIE) of (0.33, 0.35).

Environmentally benign fouling release metallosurfactant coatings; evaluation of surface properties, leaching rate, biocorrosion resistance and durability

Biofouling is the biggest issue that impair the success of marine infrastructure. The biofilm forming aerobic bacteria Pseudomonas aeruginosa present in sea water causes considerable environmental and economic losses by initiating microbially induced corrosion. Concerning the importance of fouling release coatings, we are aimed to fabricate non-toxic metallosurfactants (MS) coating on carbon steel to mitigate growth and adhesion of biofilm and consequent corrosive reactions on its surface. As the toxic ion release from fouling-release metallic coatings have deleterious effect on the aquatic eco-system therefore the MS coatings with slow release of metal ions can be a greener approach in this field. Here, we report the surface modification of CS with self-assembly of a series of MS viz. MC42H76N2Cl4, where M = Co, Ni and Cu. The MS under study is a complex of an anti-corrosive surfactant ligand cetyl pyridinium chloride (CPC) and transition metal salts in a stoichiometry of 2:1 (CPC: M). For surface modification, a cost-effective sol–gel technique was adopted. The coatings were characterized by Fourier Transform Infra-Red Spectroscopy (FT-IR), Atomic force microscopy (AFM), Energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The chemical composition of coatings reveals the presence of anti-bacterial metal ions present in mixed oxidation state causing the variable rate of their leaching in sea water media (M1942). The quantification of metal ions leached from metallosurfactant coating after immersing in M1942 media was done using inductively coupled plasma-mass spectrometry (ICP-MS). The ICP-MS data shows 19.86 ng/mL release of Cu ions from coating after 21 days of immersion which advocates its slow-release nature. The corrosion activities of sea water salts and marine bacteria Pseudomonas aeruginosa on bare and modified CS substrates was extensively studied by employing standard electrochemical tests like potentiodynamic and potentiostatic polarisation, Electrochemical Impedance Spectroscopy (EIS). The potentiodynamic polarisation test shows the coatings exhibit corrosion inhibition efficiency up to 93.5%. The coatings remained intact even after polarisation at +0.7 V in sea water media. Atomic force microscopy (AFM) and Scanning Electron Microscopy (SEM) was conducted to check corrosion morphology and biofilm characteristics. The DEAD/LIVE test of biofilm displays a higher ratio of dead bacteria on modified surface as compared to bare which demonstrate the antibacterial character of coatings. The results obtained from various corrosion tests reveal this strategy can be used to develop long term and eco-friendly anti-fouling coatings.

Disruption of zinc (II) binding and dimeric protein structure of the XIAP-RING domain by copper (I) ions.

Modulation of metalloprotein structure and function via metal ion substitution may constitute a molecular basis for metal ion toxicity and/or metal-mediated functional control. The X-linked Inhibitor of Apoptosis Protein (XIAP) is a metalloprotein that requires zinc for proper structure and function. In addition to its role as a modulator of apoptosis, XIAP has been implicated in copper homeostasis. Given the similar coordination preferences of copper and zinc, investigation of XIAP structure and function upon interaction with copper is relevant. The Really Interesting New Gene (RING) domain of XIAP is representative of a class of zinc finger proteins that utilize a bi-nuclear zinc-binding motif to maintain proper structure and ubiquitin ligase function. Herein, we report the characterization of copper (I) binding to the Zn2-RING domain of XIAP. Electronic absorption studies that monitor copper-thiolate interactions demonstrate that the RING domain of XIAP binds 5-6 Cu(I) ions and that copper is thermodynamically preferred relative to zinc. Repetition of the experiments in the presence of the Zn(II)-specific dye Mag-Fura2 shows that Cu(I) addition results in Zn(II) ejection from the protein, even in the presence of glutathione. Loss of dimeric structure of the RING domain, which is a requirement for its ubiquitin ligase activity, upon copper substitution at the zinc-binding sites, was readily observed via size exclusion chromatography. These results provide a molecular basis for the modulation of RING function by copper and add to the growing body of literature that describe the impact of Cu(I) on zinc metalloprotein structure and function.

Activation of peroxymonosulfate by a magnetic Co doped NiFe2O4 catalyst for efficient Bisphenol A degradation in water

BackgroundSulfate radicals-based advanced oxidation process (AOPs) were considered to be an effective process for treating organic wastewater. However, the difficult separation of catalysts and the toxicity of metal ions may cause secondary pollution. A new efficient and separable heterogeneous catalyst is desirable to be explored. MethodsMagnetic porous Co-doped NiFe2O4 (CoxNi1-xFe2O4, x = 0, 0.05, 0.2 and 0.5), prepared by a simple sol-gel method, were used as heterogeneous catalysts for the removal of Bisphenol A (BPA) in aqueous solution by the generation of strong oxidizing radicals and reactive oxygen species from activating peroxymonosulfate (PMS). Significant findingsCo addition increased the saturation magnetism of the catalyst and decreased the redox preparation temperature. Increasing the amount of Co-doping resulted in a pronounced enhancement of BPA removal, which the removal rate increased by 33.6% with Co-doping amount from 0 to 0.2. The hydroxyl groups on the catalyst surface plays a vital role in activating PMS, and the main reactive species for BPA degradation was determined as sulfate radical (SO4•-) and singlet oxygen (1O2) in Co0.2Ni0.8Fe2O4/PMS system. The conversion of Ni2+/Ni3+, Co2+/Co3+, and O2-/O2 for maintaining Co0.2Ni0.8Fe2O4 charge balance, PMS was activated simultaneously.

DFT calculation and experimental study of nitrogen-doped carbon nanotube nanocomposite in As+3 toxic ions removal

DFT calculation and experimental study of nitrogen-doped carbon nanotube nanocomposite in As+3 toxic ions removal

Research on the surface characterization, corrosion and bioactivity of nano-featured tantalum coating on selective electron beam melted Ti6Al4V alloy

A nano-featured tantalum coatings with an average thickness of 800 nm and grain size of 50 nm were successfully prepared by Selective Electron Beam Melted (SEBM) Ti6Al4V substrates by DC magnetron sputtering technology. The details of the physicochemical properties, corrosion resistance and in vitro biocompatibility of the coating were systematically investigated. Elastic modulus of the nano tantalum coatings was around 123.8 GPa and the hardness was 8.08 GPa. Compared with uncoated Ti6Al4V matrix, the corrosion potential of the Ta-Ti64 samples was positively shifted and the corrosion current density decreased from 2.07 × 10−7 to 2.85 × 10−8 A·cm−2 (0.1 mV/s). EIS and PDP results show that the coating enhances the humoral corrosion resistance of Ti6Al4V, which can provide active protection for the substrate to prevent the release of toxic ions caused by long-term corrosion. The mouse osteoblast cell line (MC3T3-E1) is applied in this study for biological evaluation. The optical density at 450 nm results showed that the cell proliferation rate of tantalum coated surface was faster than that of Ti6Al4V sheet and pure tantalum sheet. The 5-day cell adhesion density is 1.26 and 1.32 times higher than uncoated Ti6Al4V and pure tantalum respectively. The nano-structured Ta layer significantly improved the initial adhesion of MC3T3-E1 cells and promoted cell proliferation. The corrosion resistance and biocompatibility of Ta coating are not only better than titanium matrix, but also better than pure tantalum. The results prove that tantalum coating is an effective method to modify titanium alloy and holds a great potential value on 3D printed personalized implants application.

Correction: Bringolf et al. Major Ion Toxicity to Glochidia of Common and Imperiled Freshwater Mussel Species. Diversity 2022, 14, 95

Figures 5 and 6 (and their corresponding legends) were inadvertently omitted from the final publication of the original paper [...]

Advancement in biological and mechanical behavior of 3D printed poly lactic acid bone plates using polydopamine coating: Innovation for healthcare

The metallic biomaterials have been proclaimed to exhibit stress shielding with discharge of toxic ions, leading to polymeric implants attracting interest in 3D Printing domain. In this study, Poly Lactic Acid based 336 bone plates are fabricated using Fused Filament Fabrication with printing parameters being varied. Polydopamine, being biocompatible, is deposited on fabricated bone plates at varying submersion time, shaker speed and coating solutions concentration. The study involves witnessing the effect of printing and coating parameters on biological behavior of bone plates upon preservation in Simulated Body Fluid and Hank's Balanced Salt Solution. The findings propose the close relation of degradation with apatite growth. The highest degradation rate with significant reduction in mechanical characteristics are shown by uncoated bone plates. These bone plates have porous structure at 20% infill density, 0.5 mm layer height, 0.4 mm wall thickness and 100 mm/s print speed which could result in complete degradation with partial healing of bone fracture. The study suggests the preservation of bone plates coated at 120 h' submersion time and 120 RPM shaker speed in 3 mg/ml concentrated solution which showed lower apatite formation. Thus, the coating would slow down degradation of PLA bone plates, resulting in complete healing of bone fracture.

Construction of 1, 10-phenanthroline functionalized magnetic starch as a lead (II) tagged surface imprinted biopolymer for highly selective targeting of toxic lead ions

In this research 1, 10 - phenanthroline functionalized CaFe2O4 - starch was employed as a magnetic ion-imprinted polymer (IIP) for highly selective targeting toxic Pb2+ ions from aqueous media. VSM analysis revealed that the sorbent has magnetic saturation of 10 emu g−1 which is appropriate for magnetic separation. Moreover, TEM analysis confirmed that the adsorbent is composed of particles with a mean diameter of 10 nm. According to XPS analysis, lead coordination with phenanthroline is the main adsorption mechanism that is along with electrostatic interaction. A maximum adsorption capacity of 120 mg g−1 was obtained within 10 min at a pH of 6 and an adsorbent dosage of 20 mg. Kinetic and isotherm studies showed that lead adsorption followed the pseudo-second–order and Freundlich models, respectively. The selectivity coefficient of Pb (II) relative to Cu(II), Co(II), Ni(II), Zn(II), Mn(II), and Cd(II) was 4.7, 14, 20, 36, 13 and 25, respectively. Moreover, the IIP represents the imprinting factor of 1.32. The sorbent showed good regeneration after five cycles of the sorption/desorption process with an efficiency of >93 %. Finally represented IIP was used for lead preconcentration from various matrices i.e., water, vegetable, and fish samples.

The corrosion resistance and biomineralization of the DCPD-PCL coating on the surface of the additively manufactured NiTi alloy

Selective laser melting (SLM)-manufactured shape memory Nickel-Titanium (NiTi) alloy has great potential to use as an implant because it can achieve sophisticated structures and possess excellent mechanical properties. However, poor corrosion performance, biological inertness, and toxic Ni ions release limit its wide application. This study reports a multifunctional composite coating which composed of polycaprolactone (PCL) and dicalcium phosphate dihydrate (DCPD) by dipping method and electrodeposition to improve biomineralization and corrosion resistance of SLM-NiTi alloy. The results revealed that PCL coating successfully sealed the pores and cracks of DCPD coating and significantly improved the corrosion resistance of the coating (the corrosion current density decreased from 2.6 × 10−7 to 1.4 × 10−8 A/cm2) and the binding force was also improved (from 2397 to 2910 mN). In long-term immersion tests, the composite coating exhibited good biomineralization properties which promoted the deposition of Ca and P in simulated body fluids to form hydroxyapatite (HA). Moreover, the in vitro cell experiment showed that the composite coating was beneficial to cell adhesion and proliferation. Therefore, the DCPD-PCL-coated SLM-NiTi alloy has enormous potential as a medical implant in clinical applications.

Full Copper Resistance in Cupriavidus metallidurans Requires the Interplay of Many Resistance Systems.

The metal-resistant bacterium Cupriavidus metallidurans uses its copper resistance components to survive the synergistic toxicity of copper ions and gold complexes in auriferous soils. The cup, cop, cus, and gig determinants encode as central component the Cu(I)-exporting PIB1-type ATPase CupA, the periplasmic Cu(I)-oxidase CopA, the transenvelope efflux system CusCBA, and the Gig system with unknown function, respectively. The interplay of these systems with each other and with glutathione (GSH) was analyzed. Copper resistance in single and multiple mutants up to the quintuple mutant was characterized in dose-response curves, Live/Dead-staining, and atomic copper and glutathione content of the cells. The regulation of the cus and gig determinants was studied using reporter gene fusions and in case of gig also RT-PCR studies, which verified the operon structure of gigPABT. All five systems contributed to copper resistance in the order of importance: Cup, Cop, Cus, GSH, and Gig. Only Cup was able to increase copper resistance of the Δcop Δcup Δcus Δgig ΔgshA quintuple mutant but the other systems were required to increase copper resistance of the Δcop Δcus Δgig ΔgshA quadruple mutant to the parent level. Removal of the Cop system resulted in a clear decrease of copper resistance in most strain backgrounds. Cus cooperated with and partially substituted Cop. Gig and GSH cooperated with Cop, Cus, and Cup. Copper resistance is thus the result of an interplay of many systems. IMPORTANCE The ability of bacteria to maintain homeostasis of the essential-but-toxic "Janus"-faced element copper is important for their survival in many natural environments but also in case of pathogenic bacteria in their respective host. The most important contributors to copper homeostasis have been identified in the last decades and comprise PIB1-type ATPases, periplasmic copper- and oxygen-dependent copper oxidases, transenvelope efflux systems, and glutathione; however, it is not known how all these players interact. This publication investigates this interplay and describes copper homeostasis as a trait emerging from a network of interacting resistance systems.