Promising Chelator Research Articles

Heteroatom decorated polythiourethane sorbent for copper (II) extraction in wastewater treatment

AbstractCopper ions in wastewater present substantial environmental hazards, toxic to aquatic species and prone to bioaccumulation. Addressing this, we present a novel cross‐linked polythiourethane (C‐PTU) as a promising chelating adsorbent for the effective removal of copper ions from wastewater. A new monomer, 5‐(2,2,2‐trifluoroacetamide) benzene‐1,3‐bis(carbonyl) isothiocyanate (TFA‐ITC), was synthesized and further condensed with a 1,4‐butane diol to produce a trifluoroacetamide functionalized polythiourethane (TFA‐PTU) and subsequently generating amine functionalized polythiourethane (A‐PTU). The cross‐linking reaction was carried out through amino groups present on the polymer backbone with terephthaloyl chloride, resulting in the formation of C‐PTU. The monomer and polymers underwent characterization using Fourier transform infrared, 1H, and 13C nuclear magnetic resonance spectroscopy, with X‐ray diffraction analyzing the resin's chain alignment. Thermogravimetric and differential scanning calorimetry assessed C‐PTU's thermal properties. The adsorption process for Cu(II) ions was studied using atomic absorption spectroscopy, optimizing conditions for maximal uptake. Results revealed that C‐PTU exhibited a significant adsorption capacity for Cu(II) ions, reaching 67% after a 2 h contact time, with optimal adsorption occurring at pH 6. The Langmuir adsorption isotherm described the sorption mechanism, indicating favorable monolayer cation adsorption via coordination with donor sites on C‐PTU. This research presents a viable solution for copper ion contamination in wastewater, illustrating C‐PTU as an efficient, environmentally friendly adsorbent, marking progress toward cleaner water resources.

Radiolabeling Diaminosarcophagine with Cyclotron-Produced Cobalt-55 and [55Co]Co-NT-Sarcage as a Proof of Concept in a Murine Xenograft Model.

Cobalt-sarcophagine complexes exhibit high kinetic inertness under various stringent conditions, but there is limited literature on radiolabeling and in vivo positron emission tomography (PET) imaging using no carrier added 55Co. To fill this gap, this study first investigates the radiolabeling of DiAmSar (DSar) with 55Co, followed by stability evaluation in human serum and EDTA, pharmacokinetics in mice, and a direct comparison with [55Co]CoCl2 to assess differences in pharmacokinetics. Furthermore, the radiolabeling process was successfully used to generate the NTSR1-targeted PET agent [55Co]Co-NT-Sarcage (a DSar-functionalized SR142948 derivative) and administered to HT29 tumor xenografted mice. The [55Co]Co-DSar complex can be formed at 37 °C with purity and stability suitable for preclinical in vivo radiopharmaceutical applications, and [55Co]Co-NT-Sarcage demonstrated prominent tumor uptake with a low background signal. In a direct comparison with [64Cu]Cu-NT-Sarcage, [55Co]Co-NT-Sarcage achieved a higher tumor-to-liver ratio but with overall similar biodistribution profile. These results demonstrate that Sar would be a promising chelator for constructing Co-based radiopharmaceuticals including 55Co for PET and 58mCo for therapeutic applications.

DFT Exploration of Metal Ion-Ligand Binding: Toward Rational Design of Chelating Agent in Semiconductor Manufacturing.

Chelating agents are commonly employed in microelectronic processes to prevent metal ion contamination. The ligand fragments of a chelating agent largely determine its binding strength to metal ions. Identification of ligands with suitable characteristics will facilitate the design of chelating agents to enhance the capture and removal of metal ions from the substrate in microelectronic processes. This study employed quantum chemical calculations to simulate the binding process between eleven ligands and the hydrated forms of Ni2+, Cu2+, Al3+, and Fe3+ ions. The binding strength between the metal ions and ligands was quantified using binding energy and binding enthalpy. Additionally, we explored the binding interaction mechanisms and explained the differences in binding abilities of the eleven ligands using frontier molecular orbitals, nucleophilic indexes, electrostatic potentials, and energy decomposition calculations based on molecular force fields. Based on our computational results, promising chelating agent structures are proposed, aiming to guide the design of new chelating agents to address metal ion contamination issues in integrated circuit processes.

Inducing and real-time monitoring of lead (de)sulfation processes using scanning electrochemical microscopy for applications in the refurbishment of lead-acid batteries

Lead acid batteries (LABs) remain as a mature, cost-effective energy storage technology for a wide variety of applications. Hard sulfation is one of the primary reasons for the short lifetime of LABs. This phenomenon is primarily characterized by the formation of large, non-redox active crystals of PbSO4 which reduce the negative active material utilization by slowing down the electron transfer (ET) kinetics on the surface. Here, we report a microelectrochemical technique based on the surface interrogation mode of scanning electrochemical microscopy (SI-SECM) to locally probe the phenomenon of sulfation and the loss of ET therein. Thereafter, we validate our technique through an existing in-situ refurbishing strategy for sulfated anodes using EDTA-based chelation treatment and the recovery of ET. Energy dispersive X-ray spectroscopy (EDX) was used to verify the formation of PbSO4 and its subsequent removal post treatment. We propose that our reported microelectrochemical technique promises to be useful in evaluating possible chelator candidates for the refurbishment of sulfated LABs. Finally, we also introduce ammonium acetate as a promising chelator candidate for the removal of PbSO4 and use our proposed technique to evaluate the superior recovery of ET during ammonium acetate refurbishment. We hope this technique will be useful in evaluating the surface treatment of LABs and other energy storage electrodes which undergo redox-induced passivation processes.

Investigation of Chelating Agents for the Removal of Thorium from Human Teeth upon Nuclear Contamination.

Thorium-232 (232Th) is a radioactive heavy metal that is of increasing interest as a source of nuclear energy. However, upon nuclear incidents, the ingestion or inhalation of Th in major quantities can contribute to chemical and radiological health problems, including accumulation in the bone tissue and an increased risk of developing pancreatic, lung, and hematopoietic cancers. The major mineral component of the bone is hydroxyapatite (HAP)─also the major mineral component of the teeth. As such, the teeth are the first site of exposure upon oral ingestion of Th-contaminated materials, and Th can pose a potential risk to teeth development. In essence, in the case of human contamination, it is critical to identify effective chelating agents capable of removing Th. Using a batch study methodology, this present work investigates the uptake and the removal of Th from synthetic HAP and from teeth samples by diethylenetriamine pentaacetate (DTPA), ethylenediaminetetraacetic acid (EDTA), and other promising chelating agents. Th uptake over synthetic HAP exceeds 98% at physiological pH with <1 min of contact time and uptake exceeds 90% across the entire pH range. Regarding teeth, over 1 mg Th uptaken per gram of tooth is observed after 24 h. The overall effectiveness of chelating agents for the removal of Th from is as follows: DTPA > EDTA > NaF/mouthwash/3,4,3-LI(1,2-HOPO); this trend was observed both in synthetic HAP and Th-impregnated teeth samples.

Tetrasodium EDTA for the prevention of urinary catheter infections and blockages.

Long-term catheterised individuals are at significant risk of developing catheter-associated urinary tract infections (CAUTIs), with up to 50% of patients experiencing recurrent episodes of catheter encrustation and blockage. Catheter blockage is a result of accumulation of carbonate apatite and struvite formed upon precipitation of ions within urine due to an infection-induced rise in pH. The aim of this study was to investigate the antimicrobial and anti-encrustation activities of tetrasodium ethylenediaminetetraacetic acid (tEDTA) to evaluate its potential efficacy in preventing CAUTIs and catheter blockages. The antimicrobial activity of tEDTA against uropathogens was assessed using time kill assays performed in artificial urine (AU). Crystallisation studies and in vitro bladder model assays were conducted to investigate the effect of tEDTA on struvite crystallisation and catheter blockage. tEDTA displayed bacteriostatic activity against Proteus mirabilis and prevented precipitation of ions in the AU. Crystallisation studies confirmed tEDTA inhibits struvite nucleation and growth via Mg2+ chelation with 7.63 mM tEDTA, equimolar to the concentration of divalent cations in AU, preventing the formation of crystalline deposits and blockage of Foley catheters for ≥168 h. The promising chelating abilities of low tEDTA concentrations could be exploited to inhibit encrustation and blockage of indwelling catheters. The fundamental research presented will inform our future development of an effective tEDTA-eluting catheter coating aimed at preventing catheter encrustation.

Alpha-Lipoic Acid (ALA), fatty acid and promising chelating agent for neurological ailments

Alpha-lipoic acid, a sulphur-containing fatty acid, also known as thioctic acid, occurs as a coenzyme and component of the pyruvate dehydrogenase complex in the mitochondria of almost all living things with a cell nucleus. As a natural substance, it is considered a safe, well tolerated chelating agent. Unlike the hydrophilic chelating agents DMSA, DMPS or EDTA, which are prescription items, not easily available in some countries, the lipophilic α-lipoic acid (ALA) is a natural substance and as such not regulated as strictly. It has the ability to pass the blood brain barrier (BBB) and can thus penetrate all areas of the nervous system. Consequently, current research investigates whether and to what extent oral administration influences the development of metal-based multiple sclerosis (MS) and M. Alzheimer. With our clinical research we could confirm ALAs metal-binding ability and the extend of urinary excretion for the metals Arsenic, Barium, Manganese, Mercury and Nickel following oral application. We established a treatment protocol, suitable for people of all ages and confirmed the safety of ALA, if given in moderate doses.

Evaluation of the Effect of Macrocyclic Ring Size on [203Pb]Pb(II) Complex Stability in Pyridyl-Containing Chelators.

As an element-equivalent theranostic pair, lead-203 (203Pb, 100% EC, half-life = 51.92 h) and lead-212 (212Pb, 100% β-, half-life = 10.64 h), through the emission of γ rays and an α particle in its decay chain, respectively, can aid in the development of personalized targeted radionuclide treatment for advanced and currently untreatable cancers. With these isotopes currently being used in clinical trials, an understanding of the relationship between the chelator structure, ability to incorporate the radiometal, and metal-complex stability is needed to help design appropriate chelators for clinical use. Herein, we report an investigation into the effect of ring size in macrocyclic chelators where pyridine, an intermediate Lewis base, acts as an electron donor toward lead. Crown-4Py (4,7,13,16-tetrakis(pyridin-2-ylmethyl)-1,10-dioxa-4,7,13,16-tetraazacyclooctadecane), cyclen-4Py (1,4,7,10-tetrakis(pyridin-2-ylmethyl)-1,4,7,10-tetraazacyclododecane), and NOON-2Py (7,16-bis(pyridin-2-ylmethyl)-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane) were synthesized and analyzed for their ability to coordinate Pb2+. Metal complex stability was investigated via [203Pb]Pb2+ radiolabeling studies, 1H NMR spectroscopy, X-ray crystallography, and potentiometry. With the smallest macrocyclic backbone, cyclen-4Py had the highest radiochemical yield, while, in descending order, crown-4Py and NOON-2Py had the lowest. Thermodynamic stability constants (log KML) of 19.95(3), 13.29(5), and 11.67 for [Pb(Cyclen-4Py)]2+, [Pb(Crown-4Py)]2+, and [Pb(NOON-2Py)]2+, respectively, correlated with their radiochemical yields. The X-ray crystal structure of the least stable complexes [Pb(NOON-2Py)]2+ revealed a hemidirected Pb2+ center, as reflected by a void within the coordination sphere, and [Pb(Crown-4Py)]2+ showed an average Pb-N pyridine interatomic distance of >3 Å. By contrast, the crystal structure of [Pb(Cyclen-4Py)]2+ showed shorter Pb-N pyridine interactions, and in solution, only one highly symmetric isomer existed for this complex, whereas conformational flexibility was observed for both [Pb(Crown-4Py)]2+ and [Pb(NOON-2Py)]2+ at the NMR timescale. This study illustrates the importance of the macrocyclic backbone size when incorporating bulky electron-donor groups into the design of a macrocyclic chelator as it affects the accessibility of lead to the donor arms. Our results show that cyclen-4Py is a promising chelator for future studies with this theranostic pair.

NBMI Exerts Protection Against Copper Overload in HepG2 and SH‐SY5Y Cell Lines

Copper (Cu) is a naturally occurring essential element required for many biological processes. At low concentrations, Cu plays a vital role by getting incorporated into various metalloenzymes and at higher concentrations can be harmful to hepatic, central, and renal systems. Chronic toxicity with high concentrations of Cu have been characterized in Wilsons’s disease patients, and chelation has been the mainstay of therapy. As the currently approved chelator D‐pencillamine is associated with many adverse effects, the search for other therapeutic interventions is ongoing. N,N′bis‐(2‐mercaptoethyl) isophthalamide (NBMI) is a novel metal chelator and thiol redox antioxidant. NBMI has been shown to chelate harmful heavy metals such as mercury and lead in vitro. We explored whether NBMI displayed cytoprotective effects in HepG2 and SH‐SY5Y cells exposed to copper sulfate (CuSO4). Both the cell types were treated with either vehicle or NBMI (0 ‐ 100 μM) for 24 hours followed by CuSO4 (750 μM) for an additional 24 hours. Cell viability (CellTiter‐Glo® Assay) and degree of oxidative stress (ROS Assay) were determined. Comparisons between multiple groups were performed using analysis of variance (ANOVA) followed by a post hoc Tukey’s test. Results with p‐value &lt;0.05 were considered statistically significant. Exposure of HepG2 and SH‐SY5Y cells to CuSO4 decreased cell viability in a concentration‐dependent manner. In addition, CuSO4 exposure led to an increase in ROS levels in HepG2 cells indicating oxidative stress. Pretreatment with NBMI diminished CuSO4‐induced cell death in both cell types and decreased ROS levels in HepG2 cells. The results imply that NBMI is a new and promising chelator for treating Cu‐overload genetic disorders.

Synthesis of DOTA-pyridine chelates for 64Cu coordination and radiolabeling of \u03b1MSH peptide

Background64Cu is one of the few radioisotopes that can be used for both imaging and therapy, enabling theranostics with identical chemical composition. Development of stable chelators is essential to harness the potential of this isotope, challenged by the presence of endogenous copper chelators. Pyridyl type chelators show good coordination ability with copper, prompting the present study of a series of chelates DOTA-xPy (x = 1–4) that sequentially substitute carboxyl moieties with pyridyl moieties on a DOTA backbone.ResultsWe found that the presence of pyridyl groups significantly increases 64Cu labeling conversion yield, with DOTA-2Py, −3Py and -4Py quantitatively complexing 64Cu at room temperature within 5 min (1 × 10− 4 M). [64Cu]Cu-DOTA-xPy (x = 2–4) exhibited good stability in human serum up to 24 h. When challenged with 1000 eq. of NOTA, no transmetallation was observed for all three 64Cu complexes. DOTA-xPy (x = 1–3) were conjugated to a cyclized α-melanocyte-stimulating hormone (αMSH) peptide by using one of the pendant carboxyl groups as a bifunctional handle. [64Cu]Cu-DOTA-xPy-αMSH retained good serum stability (> 96% in 24 h) and showed high binding affinity (Ki = 2.1–3.7 nM) towards the melanocortin 1 receptor.ConclusionDOTA-xPy (x = 1–3) are promising chelators for 64Cu. Further in vivo evaluation is necessary to assess the full potential of these chelators as a tool to enable further theranostic radiopharmaceutical development.

Radiolabelling of the octadentate chelators DFO* and oxoDFO* with zirconium-89 and gallium-68.

In recent years, clinical imaging with zirconium-89 (89Zr)-labelled monoclonal antibodies (Ab) by positron emission tomography (immunoPET) has been gaining significant importance in nuclear medicine for the diagnosis of different types of cancer. For complexation of the radiometal 89Zr and its attachment to the Ab, chelating agents are required. To date, only the hexadentate chelator desferrioxamine (DFO) is applied in the clinic for this purpose. However, there is increasing preclinical evidence that the [89Zr]Zr-DFO complex is not sufficiently stable and partly releases the radiometal in vivo due to the incomplete coordination sphere of the metal. This leads to unfavourable unspecific uptake of the osteophilic radiometal in bones, hence decreasing the signal-to-noise-ratio and leading to an increased dose to the patient. In the past, several new chelators with denticities > 6 have been published, notably the octadentate DFO derivative DFO*. DFO*, however, shows limited water solubility, wherefore an oxygen containing analogue, termed oxoDFO*, was developed in 2017. However, no data on the suitability of oxoDFO* for radiolabelling with 89Zr has yet been reported. In this proof-of-concept study, we present the first radiolabelling results of the octadentate, water-soluble chelator oxoDFO*, as well as the in vitro stability of the resulting complex [89Zr]Zr-oxoDFO* in comparison to the analogous octadentate, but less water-soluble derivative DFO* and the current "standard" chelator DFO. In addition, the suitability of DFO* and oxoDFO* for radiolabeling with the short-lived PET metal gallium-68 is discussed. The water-soluble, octadentate chelator oxoDFO* provides stable complexes with the positron emitter Zirconium-89. The radiolabelling can be performed at room temperature and neutral pH and thus, oxoDFO* represents a promising chelator for applications in immunoPET.

Bioproduction of ethylenediamine-N,N'-disuccinic acid using immobilized fumarase-free EDDS lyase

Ethylenediamine-N,N'-disuccinic acid (EDDS) is a promising chelating agent for the remediation of heavy metal-contaminated soil. In general, EDDS is produced through a chemical method. In this study, we report an efficient biotechnological approach for EDDS production using an immobilized enzyme. We expressed the EDDS lyase in E. coli and obtained 19.8 g/L of EDDS through a reaction catalyzed by crude enzymes, containing EDDS lyase and fumarase. After performing metal affinity chromatography-mediated purification, we thoroughly eliminated the fumarase activity, which could result in the unnecessary formation of malate. Then, the purified EDDS lyase was immobilized on a glutaraldehyde-activated amino carrier, and the immobilized enzyme was used in 11 batches (864.5 h). After optimization, 209.3 g/L EDDS was obtained in a 100 mL reaction system, resulting in 20.2 g of EDDS product with a purity of 99.8 % after isolation. The yields of reaction and isolation were 94.0 % and 91.8 %, respectively. In conclusion, this study describes a promising bioproduction process for industrial-level EDDS production.

Hydroxamic Acid: An Underrated Moiety? Marrying Bioinorganic Chemistry and Polymer Science.

Even 150 years after their discovery, hydroxamic acids are mainly known as the starting material for the Lossen rearrangement in textbooks. However, hydroxamic acids feature a plethora of existing and potential applications ranging from medical purposes to materials science, based on their excellent complexation properties. This underrated functional moiety can undergo a broad variety of organic transformations and possesses unique coordination properties for a large variety of metal ions, for example, Fe(III), Zn(II), Mn(II), and Cr(III). This renders it ideal for biomedical applications in the field of metal-associated diseases or the inhibition of metalloenzymes, as well as for the separation of metals. Considering their chemical stability and reactivity, their biological origin and both medical and industrial applications, this Perspective aims at highlighting hydroxamic acids as highly promising chelators in the fields of both medical and materials science. Furthermore, the state of the art in combining hydroxamic acids with a variety of polymer structures is discussed and a perspective regarding their vast potential at the interface of bioinorganic and polymer chemistry is given.

Developing scandium and yttrium coordination chemistry to advance theranostic radiopharmaceuticals

The octadentate siderophore analog 3,4,3-LI(1,2-HOPO), denoted 343-HOPO hereafter, is known to have high affinity for both trivalent and tetravalent lanthanide and actinide cations. Here we extend its coordination chemistry to the rare-earth cations Sc3+ and Y3+ and characterize fundamental metal–chelator binding interactions in solution via UV-Vis spectrophotometry, nuclear magnetic resonance spectroscopy, and spectrofluorimetric metal-competition titrations, as well as in the solid-state via single crystal X-ray diffraction. Sc3+ and Y3+ binding with 343-HOPO is found to be robust, with both high thermodynamic stability and fast room temperature radiolabeling, indicating that 343-HOPO is likely a promising chelator for in vivo applications with both metals. As a proof of concept, we prepared a 86Y-343-HOPO complex for in vivo PET imaging, and the results presented herein highlight the potential of 343-HOPO chelated trivalent metal cations for therapeutic and theranostic applications.

Promising Performance of 4HMS, a New Zirconium-89 Octadendate Chelator.

Over the last decade, the interest in zirconium-89 (89Zr) as a positron-emitting radionuclide increased considerably because of its standardized production and its physical half-life (78.41 h), which matches the biological half-life of antibodies and its successful use in preclinical and clinical applications. So far, desferrioxamine (DFO), a commercially available chelator, has been mainly used as a bifunctional chelating system. However, there are some concerns regarding the in vivo stability of the [89Zr]Zr-DFO complex. In this study, we report the synthesis of an acyclic N-hydroxy-N-methyl succinamide-based chelator (4HMS) with 8 coordination sites and our first investigations into the use of this new chelator for 89Zr complexation. In vitro and in vivo comparative studies with [89Zr]Zr-4HMS and [89Zr]Zr-DFO are presented. The 4HMS chelator was synthesized in four steps starting with an excellent overall yield. Both chelators were quantitatively labeled with 89Zr within 5–10 min at pH 7 and room temperature; the molar activity of [89Zr]Zr-4HMS exceeded (>3 times) that of [89Zr]Zr-DFO. [89Zr]Zr-4HMS remained stable against transmetalation and transchelation and cleared from most tissues within 24 h. The kidney, liver, bone, and spleen uptakes were significantly low for this 89Zr-complex. Positron emission tomography images were in accordance with the results of the biodistribution in healthy mice. Based on DFT calculations, a rationale is provided for the high stability of 89Zr-4HMS. This makes 4HMS a promising chelator for future development of 89Zr-radiopharmaceuticals.

Neuroprotective Effects of N,N′bis‐(2‐mercaptoethyl) Isophthalamide (NBMI) Against Lead Induced Toxicity in U‐87 MG Cells

Background and ObjectiveLead is one of the most dangerous and ubiquitous environmental toxins with no levels safe for human exposure. Lead causes neurotoxicity primarily by inducing oxidative stress. After crossing the blood brain barrier, lead is taken up by glial cells which serve as protective lead‐binding proteins. While chelation is the mainstay of therapy for lead poisoning, currently FDA approved chelators such as dimercaptosuccinic acid (DMSA) are associated with many adverse effects and safety concerns. N,N′bis‐(2‐mercaptoethyl) isophthalamide (NBMI) is a newer lipophilic water insoluble compound with potential metal chelating and antioxidant properties. The purpose of this study was to determine whether NBMI displayed neuroprotective effects in U‐87 malignant glioblastoma (U‐87 MG) cells exposed to lead acetate (PbAc).Materials and MethodsU‐87 MG cells were treated with either vehicle, NBMI (0–100 μM), or DMSA (0–100 μM) for 24 hours followed by PbAc (0–300 μM) for 48 hours. Cell viability (CellTiter‐Glo® Assay), cell morphology (trypan blue staining), degree of oxidative stress (GSH‐GloTM Glutathione Assay), and impact on apoptosis (Bax and Bcl‐2 protein levels using Western blotting) were determined. Comparisons between multiple groups were performed using one‐way or two‐way analysis of variance (ANOVA) followed by a post‐hoc Tukey’s test. Results with a p value &lt;0.05 were considered statistically significant.ResultsExposure of U‐87 MG cells to PbAc decreased cell viability in both a concentration and time‐dependent manner. Trypan blue staining revealed that PbAc negatively altered the cell morphology. In addition, PbAc exposure led to an increase in total glutathione levels, as well as the Bax/Bcl‐2 ratio, indicating increased oxidative stress and initiation of the cell apoptotic pathway. Pretreatment with NBMI diminished PbAc‐induced cell death, morphology changes, increase in total GSH, and increase in the Bax/Bcl‐2 ratio. Interestingly, the effects of NBMI were more prominent compared to DMSA in attenuating PbAc‐induced cell death.ConclusionLead exposure induces cell death and oxidative stress which are reversed by pretreatment with NBMI implying that NBMI is a new and promising chelator for treating PbAc‐induced neurotoxicity.

Evaluation of the effect of SmearOFF on Smear Layer Removal and Erosion of Root Canal Dentin An in Vitro Study

Background and Objectives: Root canal instrumentation produces a smear layer that covers the root canal walls and may have adverse effects on endodontic treatment. SmearOFF is a new endodontic irrigant, which proposes smear layer removal and microbial elimination in one step. The aim of the present study was to evaluate and compare the effect of SmearOFF with other final irrigants regarding smear layer removal and degree of erosion from the apical third of root canals. Methods: Forty mandibular premolar roots with single canals were selected. The teeth were randomly divided into 4 groups of 10 teeth each according to the type of final irrigants used during and after instrumentation: G1 6% NaOCl/ distilled water (control), G2 6% NaOCl/Qmix, G3 6% NaOCL/SmearOFF, G4 6% NaOCL/ 17% EDTA. All teeth were shaped by using ProTaper NEXT rotary system till X2. 6% NaOCl was applied with a 27-G side-vented syringe needle as an initial irrigant followed by the final irrigants. Endoultra ultrasonic device was used for irrigation activation. The samples were then submitted to scanning electron microscopy to evaluate the effectiveness of proposed treatments. Results: In smear layer variables score 2 was the most occurred value for G2 (QMIX) and G3 (SmearOFF), whereas in G1 (Distilled water) and G4 (17% EDTA) are 3 and 1 respectively. For erosion variable, erosion was most evident in G4 (6% NaOCL/ 17% EDTA). There were no significant differences between G2 and G3 and also between G3 and G4 in both smear layers and erosion. Conclusion: 17% EDTA, SmearOFF, and QMix using PUI can remove smear layer effectively from the apical third. In the future, SmearOFF may act as a promising chelating agent as well as an antimicrobial irrigant.

Dramatic enhancement effects of l-cysteine on the degradation of sulfadiazine in Fe3+/CaO2 system

Excessive sulfonamides accumulated in soil and groundwater seriously menace the ecological environment and human health. The performance of a Fenton-like system applying Fe3+ and calcium peroxide (CaO2) in the presence of l-cysteine(l-cys) for sulfadiazine (SDZ) degradation was investigated. Compared with other chelating agents such as citric acid, butyric acid and Ethylenediaminetetraacetic acid, l-cys could effectively promote the SDZ removal in Fe3+/CaO2 system. With the addition of 0.5 mM l-cys, the SDZ degradation increased from 2.14% to 66.53% in 60 min. High concentration of HCO3− inhibited the degradation of SDZ while slightly negative effects on SDZ degradation were observed in the presence of Cl− or humic acid (HA) in l-cys/Fe3+/CaO2 system. Electron paramagnetic resonance (EPR) analysis and radicals scavenge tests affirmed the generation of OH and O2- in l-cys/Fe3+/CaO2 system. Possible degradation pathway of SDZ was speculated and the toxicity of SDZ intermediates was further evaluated. l-cys could enhance the reduction of Fe3+ to Fe2+ and reduced the Fe3+ precipitation due to the l-cys could form stable complexes with Fe3+. l-cys/Fe3+/CaO2 system exhibited high mineralization ability. Overall, these results indicated that l-cys is a promising chelating agent for sulfadiazine wastewater treatment.

AAZTA5/AAZTA5-TOC: synthesis and radiochemical evaluation with 68Ga, 44Sc and 177Lu

PurposeAAZTA (1,4-bis (carboxymethyl)-6-[bis (carboxymethyl)]amino-6-methylperhydro-1,4-diazepine) based chelators were initially developed in the context of magnetic resonance imaging. First radiochemical studies showed the capability of AAZTA to form stable complexes with radiolanthanides and moderately stable complexes with 68Ga. For a systematic comparison of the labelling capabilities with current diagnostic and therapeutic trivalent radiometals, AAZTA5 (1,4-bis (carboxymethyl)-6-[bis (carboxymethyl)]amino-6-[pentanoic-acid]perhydro-1,4-diazepine) was synthesized representing a bifunctional version with a pentanoic acid at the carbon-6 atom. To evaluate the effect of adding a targeting vector (TV) to the bifunctional chelator on the complex formation, AAZTA5-TOC was synthesized, radiolabeled and tested in comparison to the uncoupled AAZTA5.MethodsAAZTA5 was synthesized in a 5-step synthesis. It was coupled to the cyclic peptide TOC (Phe1-Tyr3 octreotide) via amide bound formation. AAZTA and AAZTA5-TOC complex formations with 68Ga, 44Sc and 177Lu were investigated at different pH, temperature and precursor amounts. Stability studies against human serum, PBS buffer, EDTA and DTPA were performed.ResultsAAZTA5 and AAZTA5-TOC achieved quantitative labelling (> 95%) at room temperature in less than 5 min with all three nuclides at pH ranges from 4 to 5.5 with low precursor amounts of 1 to 10 nmol. [44Sc]Sc-AAZTA5 complexes as well as [44Sc]Sc-AAZTA5-TOC were completely stable. The 177Lu complexes of AAZTA5 and AAZTA5-TOC showed high stability comparable to the 44Sc complexes. In contrast, the [68Ga]Ga-AAZTA5 complex stability was rather low, but interestingly, [68Ga]Ga-AAZTA5-TOC was completely stable.ConclusionAAZTA5 appears to be a promising bifunctional chelator for 68Ga, 44Sc and 177Lu with outstanding labelling capabilities at room temperature. Complex stabilities are high in the case of 44Sc and 177Lu. While [68Ga]Ga-AAZTA complexes alone lacking stability, [68Ga]Ga-AAZTA5-TOC demonstrated high stability. The latter indicates an interesting feature of [68Ga]Ga-AAZTA5–labelled radiopharmaceuticals.

Adsorption of U(VI) and Th(IV) from simulated nuclear waste using PAMAM and DGA functionalized PAMAM dendron grafted styrene divinylbenzene chelating resins

The recovery of actinides such as U(VI) and Th(IV) from nuclear waste is a critical challenge and it requires the development of novel selective and high-capacity sequestering materials. Herein a novel chelating adsorbents are prepared by grafting poly(amido)amine (PAMAM) and diglycolamic acid (DGA) functionalized PAMAM dendron on styrene divinyl benzene (SDB) solid support. Adsorption of U(VI) and Th(IV) from simulated nuclear liquid waste (SNLW) using PAMAM–SDB and DGA–PAMAM–SDB chelating resins were carried out. Our studies have found that PAMAM–SDB and DGA–PAMAM–SDB chelating resins exhibited good adsorption selectivity for U(VI) and Th(IV) at pH 5.5 in presence of other metal ions. In addition, these chelating resins finds potential application for total decontamination of SNLW at pH 12. Hence, PAMAM–SDB and DGA–PAMAM–SDB are promising chelating resins for selective removal of U(VI) and Th(IV) and also total decontamination of aqueous radioactive waste.