EDTA and DTPA modified ligands as sequestering agents for uranyl decorporation

A novel fluorescence platform for specific detection of tetracycline antibiotics based on [MQDA-Eu3+] system

Tetracycline antibiotics (TCs) are extensively used in clinical medicine, animal husbandry, and aquaculture because of their cost-effectiveness and high antibacterial efficacy. However, the presence of TCs residues in the environment poses risks to humans. In this study, an inner filter effect (IFE) fluorescent probe, 2,2'-(ethane-1,2-diylbis((2-((2-methylquinolin-8-yl)amino)-2-oxoethyl)azanediyl))diacetic acid (MQDA), was developed for the rapid detection of Eu3+ within 30 s. And its complex [MQDA-Eu3+] was successfully used for the detection of TCs. Upon coordination of a carboxyl of MQDA with Eu3+ to form a [MQDA-Eu3+] complex, the carboxyl served as an antenna ligand for the effective detection of Eu3+ to intensify the emission intensity of MQDA via "antenna effect", the process was the energy absorbed by TCs via UV excitation was effectively transferred to Eu3+. Fluorescence quenching of the [MQDA-Eu3+] complex was caused by the IFE in multicolor fluorescence systems. The limits of detection of [MQDA-Eu3+] for oxytetracycline, chlorotetracycline hydrochloride, and tetracycline were 0.80, 0.93, and 1.7 μM in DMSO/HEPES (7:3, v/v, pH = 7.0), respectively. [MQDA-Eu3+] demonstrated sensitive detection of TCs in environmental and food samples with satisfactory recoveries and exhibited excellent imaging capabilities for TCs in living cells and zebrafish with low cytotoxicity. The proposed approach demonstrated considerable potential for the quantitative detection of TCs.

Bis-Catecholamide-Based Materials for Uranium Extraction

This work reports the synthesis of formo-phenolic resins containing four catecholamide (CAM) moieties with admixture of phenol, catechol or resorcinol. These chelating resins have been developed to selectively extract U(VI) from seawater. This media is a challenging environment due to a pH around 8.2 and a large excess of alkaline and earth-alkaline cations. From the various sorption experiments investigated, the results indicate that the synthesized material exhibit good sorbent properties for U(VI) with uptake capacity about 50 mg/g for the more promising resins with a pronounced selectivity for uranium even under saline conditions. Thermodynamic and kinetic adsorption data were determined for the best resin (Langmuir adsorption model and pseudo-second order model).

Chelating Agents in Assisting Phytoremediation of Uranium-Contaminated Soils: A Review

Massive stockpiles of uranium (U) mine tailings have resulted in soil contamination with U. Plants for soil remediation have low extraction efficiency of U. Chelating agents can mobilize U in soils and, hence, enhance phytoextraction of U from the soil. However, the rapid mobilization rate of soil U by chelating agents in a short period than plant uptake rate could increase the risk of groundwater contamination with soluble U leaching down the soil profile. This review summarizes recent progresses in synthesis and application of chelating agents for assisting phytoremediation of U-contaminated soils. In detail, the interactions between chelating agents and U ions are initially elucidated. Subsequently, the mechanisms of phytoextraction and effectiveness of different chelating agents for phytoremediation of U-contaminated soils are given. Moreover, the potential risks associated with chelating agents are discussed. Finally, the synthesis and application of slow-release chelating agents for slowing down metal mobilization in soils are presented. The application of slow-release chelating agents for enhancing phytoextraction of soil U is still scarce. Hence, we propose the preparation of slow-release biodegradable chelating agents, which can control the release speed of chelating agent into the soil in order to match the mobilization rate of soil U with plant uptake rate, while diminishing the risk of residual chelating agent leaching to groundwater.

Controllable preparation and performance of bio-based poly(lactic acid-iminodiacetic acid) as sustained-release Pb2+ chelating agent

The bio-based lactic acid (LA) and the common metal ion chelating agent iminodiacetic acid (IDA) are used to design and prepare a polymeric sustained-release Pb2+ chelating agent by a brief one-step reaction. After the analysis on theoretical calculation for this reaction, poly(lactic acid-iminodiacetic acid) [P(LA-co-IDA)] with different monomer molar feed ratios is synthesized via direct melt polycondensation. P(LA-co-IDA) mainly has star-shaped structure, and some of them have two-core or three-core structure. Thus, a possible mechanism of the polymerization is proposed. The degradation rate of P(LA-co-IDA)s can reach 70% in 4 weeks. The change of IDA release rate is consistent with the trend of the degradation rate, and the good Pb2+ chelating performance is confirmed. P(LA-co-IDA) is expected to be developed as a lead poisoning treatment drug or Pb2+ adsorbent in the environment with long-lasting effect, and this research provides a new strategy for the development of such drugs.

A novel WH-flags method based on reducing the acidity of molybdenum blue (MB) reaction and stabilization by EDTA for quickly detecting phosphorus in water

There are two popular methods to measure reactive phosphorus (P) and total P: the GB11893-89 method in China and the 4500-P E method of the APHA in the US. However, their drawbacks, including long reaction time and narrow linear range, cannot satisfy the demand for modern analytic techniques. Here, based on reducing the acidity of the molybdenum blue (MB) reaction, and then stabilizing with EDTA, we have developed a novel method (WH-flags) to quickly measure both reactive P and total P. In the WH-flags method, "W" stands for Wide linear ranges (0-1.4 mg L-1 for reactive P & 0-1.8 mg L-1 for total P), "H" stands for High tolerance of different matrices (it can be adapted to a wide spectrum of samples), "f" is fast reaction time (2 min), "l" is long stabilization (40 min), "a" stands for appropriate recovery rates (89.1-103.2%), "g" is good precision and accuracy (CVs < 5% & Res < 5%) and "s" is small volume of samples (5-10 mL). The WH-flags method showed good linearity (R2 > 0.999). The WH-flags method should have broad application in monitoring P from different aqueous samples in the future.

Catechol amide derivatized polyhydroxylated fullerene as potential chelating agents of radionuclides: Synthesis, reactive oxygen species scavenging, and cytotoxic studies

Radionuclide internal contamination can induce chemical and radioactive intoxication and produce harmful free radicals in vivo. At present, administration of chelating agents is the most effective treatment against nuclide contamination. However, traditional studies on chelating agents have ignored the damage caused by free radicals to the body. The present study aimed to develop a type of a bifunctional sequestering agent that can chelates nuclides and scavenges free radicals simultaneously. Therefore, a novel catechol amide-derivatized polyhydroxylated fullerene was designed and prepared. The poor water solubility of fullerene was ameliorated by chemically modifying hydrophilic catechol amide and multiple hydroxyl groups, and obtaining high water-soluble fullerene derivatives. The affinities of chelators were investigated via sulfochlorophenol competitive complexing method and antioxidant capacities were examined by electron paramagnetic resonance. The results revealed the good complexation of the designed and synthesized chelating agent with uranyl ions; and its efficiency in scavenging hydroxyl radicals. This chelating agent showed extremely low toxicity and notable protective effect against oxidative stress on A549 cells. Besides, in U(VI)-exposed A549 cells, immediate treatment with catechol amide-derivatized polyhydroxylated fullerene significantly decreased the lactate dehydrogenase (LDH) release by inhibiting the cellular U(VI) intake, promoting the intracellular U(VI) release and inhibiting the production of intracellular reactive oxygen species (ROS). These results suggest that this fullerene derivative may be a valuable in vivo antioxidant and radionuclide decorporation agent.

Design and synthesis of a novel fluorescent probe, EuIII-dtpa-bis(adenine), and application for the detection of orotic acid in urine

For detection of orotic acid (OA), a novel fluorescent probe, EuIII-dtpa-bis(adenine), was designed and synthesized based on the complementation base pairing principle. The dtpa-bis(adenine) ligand was characterized by nuclear magnetic resonance spectroscopy (1H NMR and 13C NMR), Fourier transform infrared spectra (FTIR), and elemental analysis. Then, the effects of solution pH values and some coexisting interfering substances on OA detection using EuIII-dtpa-bis(adenine) as a fluorescent probe were investigated. The linear relationship of F0/F and OA concentration in the range of 10–150 μmol/L was obtained, where F0 and F are the fluorescence intensities of EuIII-dtpa-bis(adenine) at 320 nm in the absence and presence of OA, respectively. The calculated limit of detection is about 0.807 μmol/L. The detection mechanism of OA was proposed. In addition, the detection of OA in urine samples has also been studied. It was found that the designed and synthesized fluorescent probe is effective for the detection of OA in urine samples.

Design, solid-phase synthesis and evaluation of enterobactin analogs for iron delivery into the human pathogen Campylobacter jejuni

The human enteropathogen Campylobacter jejuni, like many bacteria, employs siderophores such as enterobactin for cellular uptake of ferric iron. This transport process has been shown to be essential for virulence and presents an attractive opportunity for further study of the permissiveness of this pathway to small-molecule intervention and as inspiration for the development of synthetic carriers that may effectively transport cargo into Gram-negative bacteria. In this work, we have developed a facile and robust microscale assay to measure growth recovery of C. jejuni NCTC 11168 in liquid culture as a result of ferric iron uptake. In parallel, we have established the solid-phase synthesis of catecholamide compounds modeled on enterobactin fragments. Applying these methodological developments, we show that small synthetic iron chelators of minimal dimensions provide ferric iron to C. jejuni with equal or greater efficiency than enterobactin.

Design and synthesis of a novel lanthanide fluorescent probe (TbIII-dtpa-bis(2,6-diaminopurine)) and its application to the detection of uric acid in urine sample

In this study, a novel fluorescent probe, Tb^III-dtpa-bis(2,6-diaminopurine) (Tb-dtpa-bdap), is designed based on the principle of complementary base pairing and synthesized for uric acid detection. The synthesized fluorescent probe is characterized by ¹H NMR, ¹³C NMR, infra-red (IR) spectrum and ultraviolet-visible (UV-vis) spectra. It is found that the fluorescence of Tb-dtpa-bdap solution can be quenched obviously in the presence of uric acid. The affecting factors, including solution acidity, uric acid concentration and interfering substances, on the detection of uric acid using this probe are examined. Under optimized conditions, the fluorescence intensities of Tb-dtpa-bdap solution towards different uric acid concentrations show a linear response in the range from 1.00 × 10^-5 mol·L^-1 to 5.00 × 10^-5 mol·L^-1 with a linear correlation coefficient (R²) of 0.9877. And the obtained limit of detection (LOD) is about 5.80 × 10^-6 mol·L^-1, which is lower than the level of uric acid in actual urine. The mechanism on the detection of uric acid by using Tb-dtpa-bdap is inferred from the experimental results. The facts demonstrate that the proposed fluorescent probe can be successfully applied for the determination of uric acid in human urine samples.

A novel fluorescent probe (dtpa-bis(cytosine)) for detection of Eu(III) in rare earth metal ions

In this paper, a novel fluorescent probe, dtpa-bis(cytosine), was designed and synthesized for detecting europium (Eu³⁺) ion. Upon addition of Eu³⁺ ions into the dtpa-bis(cytosine) solution, the fluorescence intensity can strongly be enhanced. Conversely, adding other rare earth metal ions, such as Y³⁺, Ce³⁺, Pr³⁺, Nd³⁺, Sm³⁺, Gd³⁺, Tb³⁺, Dy³⁺, Ho³⁺, Er³⁺, Yb³⁺ and Lu³⁺, into dtpa-bis(cytosine) solution, the fluorescence intensity is decreased slightly. Some parameters affecting the fluorescence intensity of dtpa-bis(cytosine) solution in the presence of Eu³⁺ ions were investigated, including solution pH value, Eu³⁺ ion concentration and interfering substances. The detection mechanism of Eu³⁺ ion using dtpa-bis(cytosine) as fluorescent probe was proposed. Under optimum conditions, the fluorescence emission intensities of Eu^III-dtpa-bis(cytosine) at 375nm in the concentration range of 0.50×10^-5mol∙L^-1-5.00×10^-5mol∙L^-1 of Eu³⁺ ion display a better linear relationship. The limit of detection (LOD) was determined as 8.65×10^-7mol∙L^-1 and the corresponding correlation coefficient (R²) of the linear equation is 0.9807. It is wished that the proposed method could be applied for sensitively and selectively detecting Eu³⁺ ion.

Magnetic resonance imaging of osteosarcoma using a bis(alendronate)-based bone-targeted contrast agent

Magnetic resonance (MR) is currently used for diagnosis of osteosarcoma but not well even though contrast agents are administered. Here, we report a novel bone-targeted MR imaging contrast agent, Gd₂-diethylenetriaminepentaacetate-bis(alendronate) (Gd₂-DTPA-BA) for the diagnosis of osteosarcoma. It is the conjugate of a bone cell-seeking molecule (i.e., alendronate) and an MR imaging contrast agent (i.e., Gd-DTPA). Its physicochemical parameters were measured, including pK_a, complex constant, and T₁ relaxivity. Its bone cell-seeking ability was evaluated by measuring its adsorption on hydroxyapatite. Hemolysis was investigated. MR imaging and biodistribution of Gd₂-DTPA-BA and Gd-DTPA were studied on healthy and osteosarcoma-bearing nude mice. Gd₂-DTPA-BA showed high adsorption on hydroxyapatite, the high MR relaxivity (r₁) of 7.613mM^-1s^-1 (2.6 folds of Gd-DTPA), and no hemolysis. The MR contrast effect of Gd₂-DTPA-BA was much higher than that of Gd-DTPA after intravenous injection to the mice. More importantly, the MR imaging of osteosarcoma was significantly improved by Gd₂-DTPA-BA. The signal intensity of Gd₂-DTPA-BA reached 120.3% at 50min, equal to three folds of Gd-DTPA. The bone targeting index (bone/blood) of Gd₂-DTPA-BA in the osteosarcoma-bearing mice was very high to 130 at 180min. Furthermore, the contrast enhancement could also be found in the lung due to metastasis of osteosarcoma. Gd₂-DTPA-BA plays a promising role in the diagnoses of osteosacomas, including the primary bone tumors and metastases.