Free Metal Ion Research Articles

Activation of peroxymonosulfate by natural pyrite for efficient degradation of V(IV)-citrate complex in groundwater

The V(IV)-organic complexes are difficult to be removed from water by the traditional water treatment processes due to their strong mobility, high stability, and possible formation of V(V) with stronger toxicity during oxidation. In this study, we applied a natural iron-based ore, pyrite, to catalyze peroxymonosulfate (PMS) activation assisted with alkali precipitation to remove V(IV) containing complexes. The effects of initial V(IV)-citrate concentration, PMS concentration, ore dosage and natural anions were comprehensively investigated using citric acid as a model ligand. Results showed that pyrite can effectively purify V(IV)-citrate. Specifically, 99.4 ± 0.4% of total vanadium and 73.6 ± 0.9% of total organic carbon are removed, and the pyrite maintained high catalytic activity after multiple uses. Characterization analyses revealed that free metal ions including Fe and V(IV) ions in the solution were removed by subsequent alkali precipitation. Radical quenching experiments indicated that sulfate radical (SO4•−) and hydroxyl radical (HO•) were generated and SO4•− is the primary reactive oxygen species. This study provides an effective strategy treating V(IV)-citrate complexes in contaminated water using low-cost natural ore.

Use of diffusive gradients in thin films (DGT) to measure potentially bioavailable metals in southeastern USA blackwater streams

We used diffusive gradients in thin films (DGT) to measure potentially bioavailable metals in coastal plain streams in the southeastern USA that exhibited strong to moderate blackwater characteristics. Metals were partitioned into particulate metals, DGT-inert metals (i.e., colloidal and refractory organic complexes not accumulated by DGT), and DGT-labile metals (i.e., free metal ions, small inorganic complexes, and labile organic complexes). We also examined the influence of different DGT deployment times using data collected from the field and a follow-up laboratory study. The DGT-measured fraction of dissolved metals in the streams was 15% for Cd, 21% for Zn, 33% for Cu, 37% for Pb, and 98% for Mn. Metals bound to particulates predominated only for Pb. Most of the Cd, Pb, Zn, and Cu were associated with colloids, refractory organic complexes, or particles. Relatively small amounts were in free ion or labile complexes likely to be bioavailable through respiratory surfaces. Modeled concentrations of free and inorganically bound Cu and Pb were lower than the DGT fraction indicating that DGT accumulated some organically bound Cu and Pb that might not have been bioavailable. DGT-exposure times in excess of 5days may have contributed to the accumulation of partly labile organic-metal complexes and were associated with substantial biofouling that caused metal uptake by DGT to depart from linearity.

POSSMs: a parsimonious speciation model for metals in soils

Environmental context Predicting the chemistry of metals is important for understanding their movement and impacts in the environment. Metal chemistry models are generally complex and difficult to apply, but a simpler model, which does not need large amounts of input data, can also provide good results. A simpler model can be more easily included in large-scale models of metal transport and impacts in the environment. Abstract Mechanistic geochemical models are useful for detailed study of the speciation of metals in well-characterised soils, but can be challenging to apply when driving soil compositional data are sparse, for example, at large scales. Empirical models, using minimal driving data, have been developed either for prediction of solid–solution partitioning or for the computation of the free metal ion from the total or geochemically active metal. This work presents an empirical speciation model, POSSMs (ParsimOniouS Speciation of Metals in soils), which predicts the free, solution-bound and sorbed metal in a soil in a single calculation, using a minimal set of soil parameters. The model has been parameterised for Ni, Cu, Zn, Cd and Pb using datasets of geochemically active soil metal and solution phase composition. The parameterised model can also be used to compute the free metal ion from the solution metal. The model was tested by applying it to literature datasets on the speciation of metals in soil solutions and extracts, and on the metal solid–solution partitioning. The performance of the model was comparable to other empirical models of similar complexity. Some test datasets produced biased predictions, particularly in the underestimation of measured free ion at circumneutral and alkaline pH, where the model predicted low free ion concentrations. The model is not a replacement for mechanistic geochemical models, but is a useful tool for soil metal speciation where comprehensive driving data are not available.

Metal contaminants of emerging concern in aquatic systems

Environmental context There is potential for a range of metals being used in emerging industries to pose a risk if they reach aquatic environments. This is assessed by evaluating known environmental concentrations against available toxicity data. In most instances risks are low with current usage. Areas are identified where additional data are needed. Abstract The environmental concentrations and aquatic toxicity of a range of technology-critical metals comprising platinum group and rare earth group elements, together with gallium, germanium, indium, lithium, niobium, rhenium, tantalum, tellurium and thallium, have been reviewed to determine whether they pose a risk to aquatic ecosystem health. There is a reasonable body of toxicity data for most, but the quality is quite variable, and more data are required. Chronic toxicity EC10 or NOEC values are generally in the low mg L–1 range, far higher than the current environmental concentrations in the ng L–1 range, meaning that the existing risks to ecosystem health are extremely low. Missing are reliable toxicity data for niobium and tantalum, while confounding results for lanthanum toxicity need to be resolved. There is a likelihood that the currently low concentrations of most of these elements will increase in future years. Whether these concentrations are in bioavailable forms remains to be reliably determined. For most of the elements, measured speciation information is scarce, and unfortunately the thermodynamic data required to calculate their speciation are incomplete. In addition to this problem of uncertain speciation for some of these metals, notably those present in oxidation states of III or higher, there is also a need to explore the links between speciation and bioavailability for these higher valence metals. For circumneutral solutions, the calculated concentrations of the free metal ion tend to be very low for these metals and under such conditions the link between metal speciation and bioavailability is unclear.

Bacterial microenvironment-responsive dual-channel smart imaging-guided on-demand self-regulated photodynamic/chemodynamic synergistic sterilization and wound healing.

Bacterial infections pose a serious threat to public health. The integration of photodynamic therapy (PDT) and chemodynamic therapy (CDT) has emerged as a promising means to combat bacterial infection. However, most photosensitizers are often in the "always on" activated state and lack bacterial targeting, leading to non-specific damage to normal tissues. Besides, most of the conventional CDT systems are directly complexed with metal ions. The toxicity of excess free metal ions cannot be ignored. Therefore, it is a huge challenge to construct a bacteria-specific activated PDT/CDT synergistic therapy platform to achieve precise sterilization. Herein, we report a bacterial microenvironment-responsive phosphorescence/fluorescence dual-channel smart imaging-guided on-demand self-regulating CDT/PDT theranostic platform for precise sterilization and wound healing. Acid-degradable persistent luminescence nanoparticles were prepared as bacterial microenvironment-responsive phosphorescence imaging units and CDT agents. Piperazine-modified PEG was then introduced as an intelligent targeting and hydrophilic group, which was further bonded with a pH-reversibly-activated fluorescence/PDT-in-one probe to construct the intelligent theranostic platform. The developed platform combines the features of good biocompatibility, prolonged blood circulation, charge-reversed intelligent targetability, dual-channel smart imaging and on-demand self-regulating CDT/PDT effect, holding great potential for precise imaging-guided bacteria-specific synergistic sterilization without side effects.

Cadmium thiosulfate complexes can be assimilated by a green alga via a sulfate transporter but do not increase Cd toxicity

Environmental context Thiosulfate is present in natural waters, especially those influenced by sulfide oxidation, and it has a marked affinity for metals such as cadmium. Normally the binding of cadmium by thiosulfate would be expected to reduce the metal’s bioavailability. However, here we demonstrate that algal uptake of cadmium is enhanced in the presence of thiosulfate, indicating that Cd can enter the alga via a novel route as an intact Cd-thiosulfate complex. Rationale For a given free metal ion activity in the exposure solution, the Biotic Ligand Model assumes that metal uptake will be independent of the various ligands present in solution that are buffering [Mz+]. In this context, we have evaluated cadmium bioavailability in the absence or presence of thiosulfate, using Chlamydomonas reinhardtii as the test alga. Methodology Short-term exposures (≤41 min) were run with a fixed concentration of the free Cd2+ ion (3.0 ± 0.1 nM), buffered with either nitrilotriacetate or thiosulfate, to determine Cd uptake. Subsequent long-term exposures (72 h) over a range of free Cd2+ concentrations were used to determine the effects of Cd on algal growth. Results Contrary to Biotic Ligand Model predictions, Cd uptake was enhanced when Cd2+ was buffered with thiosulfate. Removal of sulfate from this exposure medium increased Cd uptake; conversely, if [SO42−] was increased, Cd uptake decreased. In the absence of thiosulfate, Cd uptake was unaffected by changes in [SO42−]. In the long-term exposures, the cellular Cd quota needed to reduce algal growth by 50% was significantly higher in the presence of thiosulfate than in its absence. Discussion In the presence of thiosulfate, Cd can enter the algal cell not only by cation transport but also by transport of the intact Cd-thiosulfate complex via the anion transporter responsible for sulfate uptake. We speculate that some of the Cd taken up by anion transport remains in complexed form and is less bioavailable than the Cd that enters the cell via cation transport.

Synthesis of Gadolinium Complexes Using Medicinal Plant Extracts

Background: Gadolinium compounds are used as contrast enhancers in MRI imaging. Generally, free metal ions are not used in MRI imaging due to their toxicity. To reduce the toxicity of the free form of the metal, complexing agents are employed for making nanoparticles. Due to their low toxicity and natural abundance, plant extracts having potential to function as chelating agents are good alternatives for the formation of gadolinium nanoparticles. Methods: Aqueous extracts of five plant species, including Thymus daenensis Celak, Nepeta sessilifolia Bung, Crocus sativus L., Salvia hydrangea DC. ex Benth, and Hymenocrater incanus Bunge were prepared. Five complexes were produced as the result of each extract’s reaction with gadolinium nitrate solution in the presence of 1 mM solution of NaOH. The obtained complexes were analyzed adopting the Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and Energy dispersive x-ray analysis (EDAX) techniques. Results: EDAX analysis of the obtained complexes confirmed the presence of gadolinium in all complexes. Among the five complexes, the highest percentage of gadolinium (21.07) was recorded for the complex derived from the extract of H. incanus Bunge, while the lowest one (9.33) was detected for the complex derived from the T. daenensis Celak. Despite adopting various methods to disperse the complex particles in deionized water in order for determining the particle size, the high adhesion of the particles prevented the determination of the desired particle size in nanoscale. Conclusion: Although synthesizing the complexes was successful and EDAX confirmed the presence of gadolinium metal in them, SEM analysis failed to prove their nanoparticle structure. The high tendency of solid particles to adhere was found to prevent the formation of independent nanoparticles in solution.

WaterQuality Guidelines for Metal Contaminants in Stormwater Runoff: Insights and Considerations.

WaterQuality Guidelines for Metal Contaminants in Stormwater Runoff: Insights and Considerations.

Assessment of the risks of copper- and zinc oxide-based nanoparticles used in Vigna radiata L. culture on food quality, human nutrition and health

The present article aims to assess the phytotoxic effects of copper and zinc oxide nanoparticles (Cu NPs, ZnO NPs) on mung bean (Vigna radiata L.) and their possible risk on food quality and safety. We also study the molecular mechanisms underlying the toxicity of nanosized Cu and ZnO. Seeds of mung bean were germinated under increasing concentrations of Cu NPs and ZnO NPs (10, 100, 1000, 2000mg/L). We analyzed levels of free amino acids, total soluble sugars, minerals, polyphenols and antioxidant capacity. Our results showed that depending on the concentrations used of Cu NPs and ZnO NPs, the physiology of seed germination and embryo growth were modified. Both free metal ions and nanoparticles themselves may impact plant cellular and physiological processes. At 10mg/L, an improvement of the nutritive properties, in terms of content in free amino acids, total soluble sugars, essential minerals, antioxidant polyphenols and flavonoids, was shown. However, higher concentrations (100-2000mg/L) caused an alteration in the nutritional balance, which was revealed by the decrease in contents and quality of phenolic compounds, macronutrients (Na, Mg, Ca) and micronutrients (Cu, Fe, Mn, Zn, K). The overall effects of Cu and ZnO nanoparticles seem to interfere with the bioavailability of mineral and organic nutrients and alter the beneficial properties of the antioxidant phytochemicals, mineral compounds, phenolic acids and flavonoids. This may result in a potential hazard to human food and health, at some critical doses of nanofertilizers. This study may contribute in the guidelines to the safe use of nanofertilizers or nanosafety, for more health benefit and less potential risks.

Phenotypic changes in microalgae at acidic pH mediate their tolerance to higher concentrations of transition metals.

Acclimatory phenotypic response is a common phenomenon in microalgae, particularly during heavy metal stress. It is not clear so far whether acclimating to one abiotic stressor can alleviate the stress imposed by another abiotic factor. The intent of the present study was to demonstrate the implication of acidic pH in effecting phenotypic changes that facilitate microalgal tolerance to biologically excess concentrations of heavy metals. Two microalgal strains, Desmodesmus sp. MAS1 and Heterochlorella sp. MAS3, were exposed to biologically excess concentrations of Cu (0.50 and 1.0mg L‒1), Fe (5 and 10mg L‒1), Mn (5 and 10mg L‒1) and Zn (2, 5 and 10mg L‒1) supplemented to the culture medium at pH 3.5 and 6.7. Chlorophyll autofluorescence and biochemical fingerprinting using FTIR-spectroscopy were used to assess the microalgal strains for phenotypic changes that mediate tolerance to metals. Both the strains responded to acidic pH by effecting differential changes in biochemicals such as carbohydrates, proteins, and lipids. Both the microalgal strains, when acclimated to low pH of 3.5, exhibited an increase in protein (<2-fold) and lipid (>1.5-fold). Strain MAS1 grown at pH 3.5 showed a reduction (1.5-fold) in carbohydrates while strain MAS3 exhibited a 17-fold increase in carbohydrates as compared to their growth at pH 6.7. However, lower levels of biologically excess concentrations of the selected transition metals at pH 6.7 unveiled positive or no effect on physiology and biochemistry in microalgal strains, whereas growth with higher metal concentrations at this pH resulted in decreased chlorophyll content. Although the bioavailability of free-metal ions is higher at pH 3.5, as revealed by Visual MINTEQ model, no adverse effect was observed on chlorophyll content in cells grown at pH 3.5 than at pH 6.7. Furthermore, increasing concentrations of Fe, Mn and Zn significantly upregulated the carbohydrate metabolism, but not protein and lipid synthesis, in both strains at pH 3.5 as compared to their growth at pH 6.7. Overall, the impact of pH 3.5 on growth response suggested that acclimation of microalgal strains to acidic pH alleviates metal toxicity by triggering physiological and biochemical changes in microalgae for their survival.

A Polymer Inclusion Membrane for Sensing Metal Complexation in Natural Waters

Metal speciation studies are of great importance in assessing metal bioavailability in aquatic environments. Functionalized membranes are a simple tool to perform metal chemical speciation. In this study, we have prepared and tested a polymer inclusion membrane (PIM) made of the polymer cellulose triacetate (CTA), the extractant di-(2-ethylhexyl) phosphoric acid (D2EHPA), and the plasticizer 2-nitrophenyloctyl ether (NPOE) as a sensor for Zn and Cu complexation studies. This PIM, incorporated in a device with an 0.01 M HNO3 receiving solution, is shown to effectively transport free metal ions, and it is demonstrated that the presence of ligands that form stable complexes with divalent metallic ions, such as ethylenediaminetetraacetic acid (EDTA) and humic acid (HA), greatly influences the accumulation of the metals in the receiving phase due to the increasing metal fraction complexed in the feed phase. Moreover, the effect of major ions found in natural waters has been investigated, and it is found that the presence of calcium did not decrease the accumulation of either Zn or Cu. Finally, the PIM sensor has been used successfully to evaluate metal complexation in a river water affected by Zn pollution.

Metals and Metal-Nanoparticles in Human Pathologies: From Exposure to Therapy.

An increasing number of pathologies correlates with both toxic and essential metal ions dyshomeostasis. Next to known genetic disorders (e.g., Wilson’s Disease and β-Thalassemia) other pathological states such as neurodegeneration and diabetes are characterized by an imbalance of essential metal ions. Metal ions can enter the human body from the surrounding environment in the form of free metal ions or metal-nanoparticles, and successively translocate to different tissues, where they are accumulated and develop distinct pathologies. There are no characteristic symptoms of metal intoxication, and the exact diagnosis is still difficult. In this review, we present metal-related pathologies with the most common onsets, biomarkers of metal intoxication, and proper techniques of metal qualitative and quantitative analysis. We discuss the possible role of drugs with metal-chelating ability in metal dyshomeostasis, and present recent advances in therapies of metal-related diseases.

AGNES in irreversible systems: The indium case

• In 3+ /In 0 irreversibility is by-passed due to the lability of In hydroxy species. • AGNES conditions are met in the Nernstian region of the foot of an SSCP wave. • They can be recognized as a linear segment when plotting ln (τ/τ*) vs E d. Free indium concentrations can be determined using AGNES (Absence of Gradients and Nernstian Equilibrium Stripping) with no relevant hindrance from the irreversibility of the In 3+ /In° redox couple at a mercury electrode. The electroactivity, high lability and mobility of the In hydroxy species help in reaching AGNES conditions for a relatively moderate ratio (deposition time):(gain), which decreases with increasing pH due to the growing contribution of the hydroxy species. In the related technique SSCP (Scanned Stripping ChronoPotentiometry), points corresponding to more positive deposition potentials are said to be “at the foot of the wave”. Some of these points can reach equilibrium along the fixed SSCP deposition time, so that these points are effectively AGNES experiments, and free metal ion concentrations (such as those of free indium) can also be computed from them provided sufficiently accurate data are available. A new representation of the SSCP wave allows for the diagnosis of the potential region where AGNES conditions are fulfilled.

Characteristics of the Polyphenolic Profile and Antioxidant Activity of Cone Extracts from Conifers Determined Using Electrochemical and Spectrophotometric Methods.

The aim of the study was to analyze the polyphenolic profile of cone extracts of Douglas fir, Scots pine and Korean fir, and to study their antioxidant activity. The mechanism of electro-oxidation of polyphenols (such as procyanidins and catechins) from cone extracts was investigated using cyclic voltammetry (CV) and differential pulse voltammetry (DPV), as well as spectrophotometric methods—ABTS (2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonate)), DPPH (2,2-diphenyl-1-picrylhydrazyl), FRAP (Ferric Reducing Antioxidant Power ) and CUPRAC (CUPric Reducing Antioxidant Capacity). The scientific novelty of the research is the comprehensive analysis of cone extracts in terms of antioxidant properties. Due to the high polyphenol content, the extracts showed significant ability to reduce oxidative reactions, as well as the ability to scavenge free radicals and transition metal ions. Douglas fir, Scots pine and Korean fir cone extracts can potentially be used as natural stabilizers, preservatives and antimicrobial substances in the food industry and in medications.

Development of Cotton Linter Nanocellulose for Complexation of Ca, Fe, Mg and Mn in Effluent Organic Matter

Effluent organic matter (EfOM) is present in different domestic and industrial effluents, and its capacity to hold metallic ions can interfere in the wastewater treatment process. Due to the low quality of water, new sustainable technologies for this purpose have become extremely important, with the development of renewable-source nanomaterials standing out in the literature. Nanocellulose (NC) deserves to be highlighted in this context due to its physicochemical characteristics and its natural and abundant origin. In this context, the interactions between NC extracted from cotton linter, organic matter fraction (humic substances) and metal ions have been evaluated. Free metal ions (Ca, Fe, Mg and Mn) were separated by ultrafiltration and quantified by atomic absorption spectrometry. The nanomaterial obtained showed potential for the treatment of effluents containing iron even in the presence of organic matter. The probable interaction of organic matter with NC prevents the efficient removal of calcium, magnesium and manganese. For these elements, it is desirable to increase the interaction between metal and NC by modifying the surface of the nanomaterial.

The In Vitro Anti-Pseudomonal Activity of Cu2+, Strawberry Furanone, Gentamicin, and Lytic Phages Alone and in Combination: Pros and Cons.

In this study, we investigated the anti-pseudomonal activity of cupric ions (Cu2+), strawberry furanone (HDMF), gentamicin (GE), and three lytic Pseudomonas aeruginosa bacteriophages (KT28, KTN4, LUZ19), separately and in combination. HDMF showed an anti-virulent effect but only when applied with Cu2+ or GE. GE, at a sub-minimal inhibitory concentration, slowed down phage progeny production due to protein synthesis inhibition. Cu2+ significantly reduced both the bacterial cell count and the number of infective phage particles, likely due to its genotoxicity or protein inactivation and cell membrane disruption effects. Furthermore, Cu2+‘s probable sequestration by phage particles led to the reduction of free toxic metal ions available in the solution. An additive antibacterial effect was only observed for the combination of GE and Cu2+, potentially due to enhanced ROS production or to outer membrane permeabilization. This study indicates that possible interference between antibacterial agents needs to be carefully investigated for the preparation of effective therapeutic cocktails.

Optimization of heterogeneous Fenton-like process with Cu-Fe@CTS as catalyst for degradation of organic matter in leachate concentrate and degradation mechanism research

The heterogeneous Fenton-like process with bimetallic chelated magnetic chitosan aerogel (Cu-Fe@CTS) as catalyst was applied to treat pre-coagulated leachate nanofiltration concentrate. The process conditions were optimized by Box-Behnken Design (BBD) and the maximum UV254 removal reached 96.06% under the conditions of temperature 87.62 °C, oxidant dosage 0.2395 mol/L and catalyst dosage 1 g/L. The TOC concentration was reduced from 847.5 to 99.7 mg/L and COD concentration was reduced from 1625 to 464 mg/L. The three-dimensional (3D) fluorescence analysis showed that most of Fulvic acid-like (FA-like) was removed. The adsorption experiment showed that the catalyst reached the adsorption balanced after 60 min and the corresponding FA adsorption removal reached 14.1%. The addition of Tert-butanol (TBA) reduced the FA removal by 59.4%, indicating that the hydroxyl radicals (OH) was the main active species. Experiments of the OH capture at different pH showed that the Fenton-like system produced more OH at pH of 4, at which the maximum FA removal was 96.61%, while the FA removal still reached 94.26% at pH of 7. The OH capture at different temperature showed that the Fenton-like system produced more OH at 90 °C. KI and TBA shielding experiments showed that OH was produced on the catalyst surface rather than being produced by catalysis of free metal ions in the solution.

Development of an Immunoassay for the Detection of Copper Residues in Pork Tissues.

The presence of high concentrations of copper (Cu) residues in pork is highly concerning and therefore, this study was designed to develop a high-throughput immunoassay for the detection of such residues in edible pork tissues. The Cu content in the pork samples after digestion with HNO3 and H2O2 was measured using a monoclonal antibody (mAb) against a Cu (II)–ethylenediaminetetraacetic acid (EDTA) complex. The resulting solution was neutralized using NaOH at pH 7 and the free metal ions in the solution were chelated with EDTA for the immunoassay detection. An indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) method was developed for Cu ion analysis. The half maximal inhibitory concentration of the mAb against Cu (II)–EDTA was 5.36 ng/mL, the linear detection range varied between 1.30 and 27.0 ng/mL, the limit of detection (LOD) was 0.43 μg/kg, and the limit of quantification (LOQ) was 1.42 μg/kg. The performances of the immunoassay were evaluated using fortified pig serum, liver, and pork samples and had a recovery rate of 94.53–102.24%. Importantly, the proposed immunoassay was compared with inductively coupled plasma mass spectroscopy (ICP-MS) to measure its performance. The detection correlation coefficients of the three types of samples (serum, pork, and liver) were 0.967, 0.976, and 0.983, respectively. Thirty pork samples and six pig liver samples were collected from local markets and Cu was detected with the proposed ic-ELISA. The Cu content was found to be 37.31~85.36 μg/kg in pork samples and 1.04–1.9 mg/kg in liver samples. Furthermore, we detected the Cu content in pigs with feed supplemented with tribasic copper chloride (TBCC) and copper sulfate (CS) (60, 110, and 210 mg/kg in feed). There was no significant difference in Cu accumulation in pork tissues between the TBCC and CS groups, while a remarkable Cu accumulation was found for the CS group in liver at 210 mg/kg, representing more than a two-fold higher level than seen in the TBCC group. Therefore, the proposed immunoassay was found to be robust and sensitive for the detection of Cu, providing a cost effective and practical tool for its detection in food and other complicated samples.

Conjugated Polymer-Ferrocence Nanoparticle as an NIR-II Light Powered Nanoamplifier to Enhance Chemodynamic Therapy.

Chemodynamic therapy (CDT) is a promising therapeutic modality with transition metal ions and endogenous H2O2 as reagents, but its efficiency is impaired by low endogenous H2O2 levels and nonregeneration of metal ions. Most intracellular H2O2 supplement strategies use oxidases and are intensively dependent on oxygen participation. The hypoxia microenvironments of solid tumors weaken their performance. Here, we develop a near-infrared II light powered nanoamplifier to improve the local oxygen level and to enhance CDT. The nanoamplifier CPNP-Fc/Pt consists of ferrocene (Fc)- and cisplatin prodrug (Pt(IV))-modified conjugated polymer nanoparticles (CPNPs). CPNP has a donor-acceptor structure and demonstrates a good photothermal effect under 1064 nm light irradiation, which accelerates blood flow and efficiently elevates the local oxygen content. In response to intracellular glutathione, Pt(II) is released from CPNP-Fc/Pt and triggers enzymatic cascade reactions with nicotinamide adenine dinucleotide phosphate oxidase (NADPH oxidase) and superoxide dismutase to convert oxygen into H2O2. The enhanced oxygen level results in efficient intracellular H2O2 supply. Fc is reacted with H2O2 and converted to Fc+ via the Fenton reaction, with the generation of hydroxyl radicals for CDT. Unlike free metal ions, the Fe(III) in Fc+ is reduced to Fe(II) by intracellular NAD(P)H, which achieves the regeneration of Fc. The sufficient intracellular H2O2 supply and efficient Fc regeneration effectively enhance the Fenton reaction and demonstrate good in vivo CDT results with tumor growth suppression. This design offers a promising strategy to enhance CDT efficiency in the hypoxia microenvironment of solid tumors.

Effects of free metal ions and organo-metal complexes on the absorption of lead and cadmium by plants

토양 중 중금속은 자유이온, 유기산-중금속 복합체를 포함한 다양한 화학종으로 존재한다. 이 중 중금속 자유이온 비율은 식물체의 중금속 흡수와 밀접한 관련이 있는 것으로 알려져 있다. 본 연구는 중금속 자유이온과 유기산-중금속 복합체 존재 비율이 식물의 납, 카드뮴 흡수에 어떤 영향을 미치는지 알아보기 위하여 수행되었다. 이를 위해 순환식 양액재배 장치에서 28일간 키운 상추를 48시간 동안 납과 카드뮴 용액에 침지시키는 실험을 진행하였다. 침지 전 시트르산, 옥살산, 아세트산, 휴믹산을 이용해 납과 카드뮴 용액의 중금속 자유이온과 유기산-중금속 복합체의 비율이 100:0, 90:10, 70:30, 60:40이 되도록 조절하였다. 침지 후 상추 뿌리와 잎의 납, 카드뮴 농도를 분석한 결과, 용액 중 중금속 자유이온의 비율과 식물이 흡수한 납, 카드뮴 농도는 상관관계를 보이지 않았다. 반면에 처리한 유기산의 종류와 중금속 종류에 따른 차이가 더 큰 것으로 나타났다. 시트르산은 납 흡수는 증가시켰지만 카드뮴 흡수는 감소시켰다. 시트르산은 다른 유기산보다 상추의 납 흡수율을 높였는데 이는 시트르산이 분자량이 크기 때문에 중금속 이온과 복합체를 형성할 수 있는 용량이 더 크기 때문인 것으로 보인다. 그러므로 본 연구 결과는 식물에 의한 중금속 흡수가 단순히 자유이온의 양에 따라 달라지기 보다는 존재하는 유기산의 분자량에 의한 결합용량 차이가 중금속 종류에 따라 달리 작용하여 결정된다는 것을 보여준다.