Chelating Agent Diethylenetriaminepentaacetic Acid Research Articles

Pore-scale study of the effects of DTPA chelating agent flooding on oil recovery utilizing a clay-coated micromodel

The use of diethylenetriaminepentaacetic acid (DTPA) chelating agent has shown promising results for enhanced oil recovery (EOR) in prior research. Several mechanisms, mainly resulting from rock-fluid interaction, have been proposed for chelating agent flooding; however, little attention has been paid to fluid-fluid interaction thus far. The assessment of these mechanisms has primarily relied on macroscopic techniques such as core flooding. This paper aims to investigate the injection of DTPA brine and its dominant mechanisms at the pore scale using a clay-coated micromodel. The micromodel tests were performed under oil-wet and water-wet states. For a more precise examination of fluid/fluid interactions, the dynamic interfacial tension (IFT) and Zeta potential were measured. It was observed that the injection of DTPA brine in water-wet state changed the saturation distribution and increased oil recovery. Based on visual inspections, this change in saturation distribution could potentially be linked to the formation of micro-dispersions and viscoelastic interfacial phenomena. Micro-dispersions facilitate flow to unswept areas, and viscoelastic interface formation reshapes the interface between oil and brine, causing disconnected oil droplets to coalesce and thus increase recovery. Under the oil-wet state, the micro-dispersion formation and wettability alteration can be the dominant mechanisms, and the amount of recovered oil was higher than that observed in the water-wet state. Furthermore, Zeta potential measurements at the interface between brine and oil showed a more negative value for DTPA brine, which is effective in wettability alteration and micro-dispersions stability. The results indicate that IFT reduction was not significant enough to be considered the dominant mechanism, although it assists in DTPA brine penetration into the crude oil and subsequent micro-dispersion formation.

Improved Reversion of Calcifications in Porcine Aortic Heart Valves Using Elastin-Targeted Nanoparticles.

Calcified aortic valve disease in its final stage leads to aortic valve stenosis, limiting cardiac function. To date, surgical intervention is the only option for treating calcific aortic valve stenosis. This study combined controlled drug delivery by nanoparticles (NPs) and active targeting by antibody conjugation. The chelating agent diethylenetriaminepentaacetic acid (DTPA) was covalently bound to human serum albumin (HSA)-based NP, and the NP surface was modified using conjugating antibodies (anti-elastin or isotype IgG control). Calcification was induced ex vivo in porcine aortic valves by preincubation in an osteogenic medium containing 2.5 mM sodium phosphate for five days. Valve calcifications mainly consisted of basic calcium phosphate crystals. Calcifications were effectively resolved by adding 1-5 mg DTPA/mL medium. Incubation with pure DTPA, however, was associated with a loss of cellular viability. Reversal of calcifications was also achieved with DTPA-coupled anti-elastin-targeted NPs containing 1 mg DTPA equivalent. The addition of these NPs to the conditioned media resulted in significant regression of the valve calcifications compared to that in the IgG-NP control without affecting cellular viability. These results represent a step further toward the development of targeted nanoparticular formulations to dissolve aortic valve calcifications.

A comprehensive evaluation of the effect of key parameters on the performance of DTPA chelating agent in modifying sandstone surface charge

Despite the positive aspects of low salinity water (LSW), this technique is relatively expensive and unavailable in some countries. Furthermore, potential problems associated with LSW such as scale precipitation in carbonate reservoirs and fine migration in sandstone reservoirs raise concerns. Chelating agents have the ability to chelate metal ions from solution, effectively reducing the salinity of seawater (SW) and mimicking the behavior of LSW. However, they mitigate the challenges associated with LSW injection. This study focuses on how the Diethylenetriaminepentaacetic acid (DTPA) chelating agent performs in modifying rock surface charge. The impact of concentration, brine salinity, potential determining ions (PDIs), oil presence, Fe3+ ions, and solution pH on the effectiveness of DTPA in altering rock surface charge was evaluated. Furthermore, wettability alteration and sand pack flooding tests were conducted to study the effect of DTPA on rock wettability and oil recovery. Results of wettability alteration, zeta potential, sand pack flooding experiments and ion concentration analysis are reported in this paper. The results showed that reducing salinity, increasing DTPA concentration, and raising solution pH changed rock wettability from oil-wetness towards water-wetness. The presence or absence of PDIs in the solution did not affect the performance of DTPA. However, by tripling the concentration of these ions in the solution, the performance of DTPA in changing rock surface charge was impaired. Based on the wettability alteration and zeta potential experiments, 5 wt% DTPA was determined as the optimum concentration. Subsequent flooding experiments revealed that injecting 5 wt% DTPA chelating agents into the sandstone sand pack after SW injection increased oil recovery from 48 % to 68.3 %. The analysis of ion concentrations also revealed a significant increase in the amount of calcium ions during the DTPA flooding, indicating the chelation of metal ions from both rock and solution and improving the wettability conditions.

Comprehensive analysis of the effect of reservoir key parameters on the efficacy of DTPA chelating agent in minimizing interfacial tension and enhanced oil recovery

Chelating agents reduce the salinity of seawater (SW) and mimic low salinity water (LSW) by binding metal ions in the solution and on the rock surface. This process decreases SW dilution costs and prevents scale formation while improving oil recovery without damaging the reservoir. This study investigates the impact of Diethylenetriaminepentaacetic acid (DTPA) chelating agent on the reduction of interfacial tension (IFT) between oil and SW, without the use of additional chemicals. For the first time, we comprehensively analyzed how reservoir key parameters (concentration, salinity, temperature, and pH) affect the performance of DTPA in reducing IFT. Additionally, rock wettability alteration and sand pack flooding experiments were conducted to evaluate the effect of DTPA on rock wettability and oil recovery. The results revealed that increasing the temperature to 75 °C and the concentration of DTPA to 5 wt% resulted in an IFT reduction to less than 1 mN/m, making the oil miscible in the DTPA solution. Salinity studies demonstrated that by increasing the solution salinity up to the optimal level, the IFT of oil/brine decreased. Furthermore, using 5 wt% DTPA solution altered the rock/oil contact angle from 143° (oil-wet) to 23° (strongly water-wet), highlighting the effect of DTPA on rock wettability alteration. Based on these findings, 5 wt% DTPA was selected as the optimal concentration, resulting in an increase in oil recovery up to 20.3% of original oil in place (OOIP) after SW injection. Elemental analysis of DTPA flooding effluent also confirmed the chelation of metal ions from rock and solution.

99mTc-labeled keratin gold-nanoparticles in a nephron-like microfluidic chip for photo-thermal therapy applications

Biocompatible gold nanoparticles (AuNPs) are particularly interesting for photo-thermal therapy (PTT) of cancer treatment because of their ability to convert light into heating efficiently. Nevertheless, the random accumulation of AuNPs in tissues, mainly determined by their retention time in the bloodstream, is one of the main limiting factors for their use in PTT applications. For this reason, efficient targeting and monitoring of AuNPs in the selected tissues is of paramount importance. This manuscript reports on a new generation of 99mTc-labeled AuNPs coated with keratin (Ker-AuNPs) and their spatial localization investigated by nuclear imaging techniques on an animal-free model. The effective radiolabeling of Ker-AuNPs with 99mTc is achieved using the chelating agent diethylenetriaminepentaacetic acid (DTPA), resulting in the 99mTc-DTPA-Ker-AuNPs nanoconjugate. The 99mTc-DTPA-Ker-AuNPs display a radiochemical purity of 90.7% and excellent photo-thermal properties. In addition, the biocompatibility of the 99mTc-DTPA-Ker-AuNPs with healthy human embryonic kidney (HEK293T) cells is shown. A Lab-On-a-Chip (LoC) approach is used to localize and study the stability of 99mTc-DTPA-Ker-AuNPs under dynamic conditions. To this end, the nanoconjugates are injected into a polydimethylsiloxane microfluidic chip mimicking the renal filtering unit, the nephron, and monitored via radio-imaging and thermo-optical experiments. These detailed studies establish that DTPA-assisted 99mTc-labeled Ker-AuNPs are excellent candidates as biocompatible and non-invasive radiolabeled nanotherapeutic for PTT-based applications.

Covalent functionalization of Ti3C2T MXene flakes with Gd-DTPA complex for stable and biocompatible MRI contrast agent

MXenes are an excellent candidate for medical applications, including diagnostic approaches such as positron emission tomography, computed tomography, and magnetic resonance imaging (MRI). However, the utilization of MXenes for bioimaging is restricted by their commonly diamagnetic nature. MXenes can be functionalized using ferromagnetic or paramagnetic compounds and nanoparticles to develop efficient bioimaging tools. In contrast to previously published approaches based on electrostatic interactions, covalent approaches could enhance MXene stability and prevent self-aggregation with degradation. This work proposes covalent functionalization of Ti3C2T flakes with a chelating agent diethylenetriaminepentaacetic acid (DTPA) and further complexing with Gd3+ ions. The developed functionalization procedure provides a paramagnetic response to the intrinsically diamagnetic Ti3C2T flakes for T1-MR imaging. Moreover, we observed the apparent dependency of magnetic relaxation time on the flake concentration, which enabled us to estimate the spatially resolved flake distribution. The covalent decoration strategy for MXene led to surface protection against oxidation in phosphate buffer saline and blood serum, accompanied by increased cytocompatibility. Moreover, chelation of Gd3+ ions prevented leaking compared with electrostatic chemisorption. We demonstrated a high degree of photothermal conversion efficiency of MXene-Gd, anticipating future application in photothermal therapy. This work broadens the bioapplication of MXenes, not only by introducing an MRI contrast but also by developing covalent functionalization strategies for MXenes.

Tuning the Kinetic Inertness of Bi3+ Complexes: The Impact of Donor Atoms on Diaza-18-Crown-6 Ligands as Chelators for 213Bi Targeted Alpha Therapy.

The radionuclide 213Bi can be applied for targeted α therapy (TAT): a type of nuclear medicine that harnesses α particles to eradicate cancer cells. To use this radionuclide for this application, a bifunctional chelator (BFC) is needed to attach it to a biological targeting vector that can deliver it selectively to cancer cells. Here, we investigated six macrocyclic ligands as potential BFCs, fully characterizing the Bi3+ complexes by NMR spectroscopy, mass spectrometry, and elemental analysis. Solid-state structures of three complexes revealed distorted coordination geometries about the Bi3+ center arising from the stereochemically active 6s2 lone pair. The kinetic properties of the Bi3+ complexes were assessed by challenging them with a 1000-fold excess of the chelating agent diethylenetriaminepentaacetic acid (DTPA). The most kinetically inert complexes contained the most basic pendent donors. Density functional theory (DFT) and quantum theory of atoms in molecules (QTAIM) calculations were employed to investigate this trend, suggesting that the kinetic inertness is not correlated with the extent of the 6s2 lone pair stereochemical activity, but with the extent of covalency between pendent donors. Lastly, radiolabeling studies of 213Bi (30-210 kBq) with three of the most promising ligands showed rapid formation of the radiolabeled complexes at room temperature within 8 min for ligand concentrations as low as 10-7 M, corresponding to radiochemical yields of >80%, thereby demonstrating the promise of this ligand class for use in 213Bi TAT.

Effect of Treatment Conditions on Matrix Stimulation of Carbonate Rocks with Chelating Agents

This study aimed to optimize the acidizing efficiency during stimulation treatments with chelating agents. The performance of hydroxylethylethylenediaminetriacetic acid (HEDTA), diethylenetriaminepentaacetic acid (DTPA), and ethylenediaminetetraacetic acid (EDTA) in stimulating carbonate rocks were investigated. In this paper, the effect of injection rate, chemical type, pH, and concentration on the stimulation performance was studied. Also, the optimum treatment conditions were identified utilizing the acid volume and treatment time. Different measurements were carried out, including solubility tests, coreflooding experiments, and CT scan analysis. Solubility tests were performed to study the impact of solution concentration and pH on the performance of the chelating agent. Coreflooding experiments were carried out at high-pressure, high-temperature conditions to assess the performance of chelating agents in different treatment situations. In addition, CT scan analysis was carried out before and after the acid injections to capture the changes induced in the carbonate matrix due to the stimulation treatment. The success of acidizing treatment was identified by the creation of the dominant wormholes. The pressure-drop profiles and the CT scan analysis were used to confirm the generation of wormholes. Finally, the normalized volume and time to breakthrough were utilized to identify the optimum treatment conditions. In this work, chelating agents successfully created dominant wormholes (WHs) in carbonate rocks at different injection rates and treatment conditions. However, applying an injection rate between 0.7 and 1 cm3/min significantly improved the acidizing performance and reduced the acid volume that was required to create wormholes. EDTA and HEDTA chelating agents showed better performance at low pH. Using a solution pH of 4.5 resulted in reducing the acid volume by 30% compared to using a solution pH of 10 at the same conditions. However, DTPA chelating agent showed better performance at high pH, and dominant WHs were created at a pH of 12 using less acid volume. Finally, the optimum acidizing treatment can be achieved by using EDTA chelating agent with a concentration of 9.25 wt.% and pH of 4.5. Applying the optimum treatment parameters can reduce the acid volume by 40% and the chemical cost by a factor of 6, on average. Overall, this study indicates that chelating agents’ solution can be injected at optimum conditions in terms of chemical concentration, pH, and injection rate, to maximize the treatment efficiency and reduce the cost.

Evidence for a differential translocation of actinides across human lung epithelial cell monolayer in vitro according to their physicochemical properties and the presence of a chelating agent

The epithelial cell plays a key role in the transfer of radionuclides from lungs to blood following pulmonary exposure. The present study was designed to evaluate the transfer across human lung epithelial cells of various actinides (plutonium, americium and uranium), the influence of the physicochemical properties of plutonium compounds and of the chelating agent diethylene triamine pentaacetic acid (DTPA). To address this question, Calu-3 cells grown in a bicameral culture system were used. The integrity of the epithelial barrier was evaluated by measuring transepithelial electrical resistance (TEER) and the passage of a fluorescent marker, lucifer yellow. Activity measurement in basal compartment following periodic collection of culture medium was made from 2 h to seven days. To facilitate data handling and analysis, the statistical tool STATBIODIS was used. The results indicate differences in transfer for the different elements, and according to Pu physicochemical properties. Though to various extents, the chelating agent DTPA always increased the transfer of Pu and Am across the epithelial cells, without altering the integrity of the epithelial barrier.This in vitro cell culture model, by mimicking translocation of actinides from lungs to blood, can represent a valuable tool to further understand the underlying mechanisms and properties controlling this process.

Fluorescent DTPA-Silk Fibroin Nanoparticles Radiolabeled with 111In: A Dual Tool for Biodistribution and Stability Studies.

This work aims to provide an effective and novel dual tool for the biodistribution studies of biopolimeric nanoparticles by using modified silk fibroin nanoparticles as a model. This is an indispensable step in the evaluation of the applicability of biopolymeric nanoparticles as drug delivery systems. In this work, we report a new facile method for radiolabeling silk fibroin nanoparticles conjugated to the chelating agent diethylenetriamine pentaacetic acid and tagged with fluorescein isothiocyanate. Nanoparticles were characterized by means of dynamic light scattering, scanning electron microscopy, and infrared and fluorescence spectroscopy. The in vitro studies included stability in biological media and evaluation of the cytotoxicity of the nanoparticles in a cell culture. The in vivo study was focused on a scintigraphic study over 24 h conducted on New Zealand rabbits, after intra-articular injection of [111In]In-nanoparticles containing 8.03 ± 0.42 MBq. Biodistribution of the nanoparticles was also assessed ex vivo by fluorescence microscopy of post mortem biopsied organs. This radiolabeling method was reproducible and robust with high radiolabeling efficiency (∼80%) and high specific activity suitable for in vivo studies. Radiolabeled nanoparticles, having a hydrodynamic radius of 113.2 ± 2.3 nm, a polydispersity index of 0.101 ± 0.015, and a Z-potential of -30.1 ± 2.0 mV, showed an optimum retention in the articular space, without activity clearance up to 24 h post injection. Thus, an easy and robust radiolabeling method has been developed, and its applicability is demonstrated in vitro and in vivo studies, showing its value for future investigation of silk fibroin nanoparticles as versatile and stable (steady) local drug delivery systems for consideration as a therapeutic option, particularly in the treatment of joint disorders.

Evaluation of the Reaction Kinetics of Diethylenetriaminepentaacetic Acid Chelating Agent and a Converter with Barium Sulfate (Barite) Using a Rotating Disk Apparatus

Barium sulfate (barite) is a major oil and gas field scale formed inside the production equipment as well as in the reservoir. During drilling of oil and gas wells, barite serves as a weighting material in different drilling fluid formulations. Barite solubility is very low in inorganic and organic acids. In this study, diethylenetriaminepentaacetic acid (DTPA) chelating agent and a converter (K2CO3) are introduced to dissolve barite scale. Potassium carbonate was selected as a converter because it is cheap and available and has no environmental concerns. For the first time, the reaction kinetics of DTPA chelating agent and the converter with intact barite rock samples are investigated. Barite core samples were plugged from actual barite rock that is used to prepare the barite powder for the drilling fluid. The reaction kinetics of DTPA and the converter with barite rocks were studied by a rotating disk apparatus (RDA). The results of the RDA show a linear increase in the reaction rate with the disk rotat...

Molecular Modeling Study toward Development of H2S-Free Removal of Iron Sulfide Scale from Oil and Gas Wells.

A common problem that faces the oil and gas industry is the formation of iron sulfide scale in various stages of production. Recently an effective chemical formulation was proposed to remove all types of iron sulfide scales (including pyrite), consisting of a chelating agent diethylenetriaminepentaacetic acid (DTPA) at high pH using potassium carbonate (K2CO3). The aim of this molecular modeling study is to develop insight into the thermodynamics and kinetics of the chemical reactions during scale removal. A cluster approach was chosen to mimic the overall system. Standard density functional theory (B3LYP/6-31G*) was used for all calculations. Low spin K4Fe(II)4(S2H)12 and K3Fe(II)(S2H)5 clusters were derived from the crystal structure of pyrite and used as mimics for surface scale FeS2. In addition, K5DTPA was used as a starting material too. High spin K3Fe(II)DTPA, and K2S2 were considered as products. A series of KmFe(II)(S2H)n complexes (m = n–2, n = 5–0) with various carboxylate and glycinate ligands was used to establish the most plausible reaction pathway. Some ligand exchange reactions were investigated on even simpler Fe(II) complexes in various spin states. It was found that the dissolution of iron sulfide scale with DTPA under basic conditions is thermodynamically favored and not limited by ligand exchange kinetics as the activation barriers for these reactions are very low. Singlet–quintet spin crossover and aqueous solvation of the products almost equally contribute to the overall reaction energy. Furthermore, seven-coordination to Fe(II) was observed in both high spin K3Fe(II)DTPA and K2Fe(II)(EDTA)(H2O) albeit in a slightly different manner.

Interactions of DTPA chelating agent with sandstone rocks during EOR: Rock surface charge study

Enhanced oil recovery (EOR) using low salinity water has been proven experimentally and at the field scale. One of the mechanisms behind recovery enhancement due to low salinity water injection has been related to the change of rock surface charge which might lead to wettability alteration. Low salinity water EOR has its own disadvantages such as the high cost due to the need for enormous amounts of fresh water and it may cause scale precipitation and fines migration. Therefore, efficient and alternative low-cost EOR methods are needed. In this work, chelating agent diethylenetriaminepentaacetic acid (DTPA) for EOR application in sandstone rock was investigated. DTPA is an efficient metal ion control agent and can seize certain cations (especially Fe3+) from rock surfaces. DTPA chelating agent is very stable up to 400 °F at high pH values. The effect of DTPA injection on the surface charge of the sandstone rocks was investigated. Zeta potential measurements, ions analysis after interaction with the rock, and coreflooding experiments were performed. Three different types of sandstone rocks were used to investigate the changes in rock surface after conditioning with DTPA. Several scenarios were tested to compare low salinity water, deionized water, and seawater with DTPA chelating agent. The comparison was made by measuring the zeta potential of the rock powder. Coreflooding experiment was conducted along with effluent analysis for SO42−, Ca2+, Mg2+, Fe3+, and Al3+ ions to observe the effect of injecting DTPA with seawater on oil recovery and permeability. The results showed that the addition of DTPA resulted in Fe+3 ions absorption from the rock surface. Absorbing such trivalent cation resulted in a significant change in surface charge. Zeta potential dropped towards a more negative value for all sandstone rocks samples used in this study. Zeta potential results showed that mixing Berea sandstone with 5 wt% of DTPA in seawater led to similar surface charge value as if it was mixed with low salinity water for the same period. This means that DTPA combats the effect of the concentrated salts in seawater. DTPA chelated all multivalent cations in seawater and eliminated their effects on the surface charge. Also, DTPA increased the pH of the seawater from 7 to 11 and this will drag the surface charge to more negative. From coreflooding experiment, we observed that injecting 5 wt% DTPA solution in seawater after seawater injection enhanced the oil recovery from 56% to 75% in Berea sandstone cores at 100 °C. The additional oil recovery can be explained by more negative values of the zeta potential of the rock surface. We expect that chelating agent EOR using DTPA is a viable alternative to low salinity water flooding where huge fresh water is required to dilute the seawater.

Development of efficient formulation for the removal of iron sulphide scale in sour production wells

AbstractIron sulphide scale, which exists in different forms, is common in sour oil and gas production wells. Iron sulphide hard scales are difficult to remove with acids, requiring mechanical intervention or the replacement of the production tubing. An environmentally friendly formulation with a high pH is proposed for the removal of both soft and hard iron sulphide scale from oil and gas wells. The formulation consists of DTPA (di‐ethylene tri‐amine penta acetic acid) in addition to K2CO3 as a catalyst. High pressure high temperature solubility experiments were performed under both static and dynamic conditions in the temperature range of 70–150 °C and a constant pressure of 3447.38 kPa. Several combinations of the catalyst and DTPA chelating agent were used to optimize the catalyst/DTPA ratio to achieve maximum scale solubility. Field scale samples were collected and analyzed using XRD. The scale removal efficiency of the proposed formulation outperforms that of the current formulations used in the oil industry, with the added advantage of not releasing H2S. The optimum DTPA concentration is 20 wt% and the optimum catalyst concentration is 9 wt%, which provides a solubility of 90 % of the field scale. In addition, the ecotox profile of the proposed formulation is better than that of the currently used formulations because toxic corrosion inhibitors are not used. The maximum reported corrosion rate for the new formulation is 0.036 kg/m2, which is well below the acceptable limit (< 0.227 kg/m2).

Effect of Chlorite Clay-Mineral Dissolution on the Improved Oil Recovery From Sandstone Rocks During Diethylenetriaminepentaacetic Acid Chelating-Agent Flooding

SummarySandstone oil reservoirs consist of different clay minerals, such as kaolinite, illite, and chlorite. While these clay minerals can highly affect oil recovery from sandstone oil reservoirs, no attention has been given to investigating the effects of clay minerals during such oil recovery, and no solution has been introduced to alleviate the effects.In this study, and for the first time, the effect of chlorite clay-mineral content on the improved oil recovery (IOR) from different sandstone rock samples was investigated. A new solution was proposed to eliminate the effect of chlorite on the oil recovery from sandstone rocks. Different sandstone cores were used, such as Berea (BSS), Bandera (BND), Kentucky (KSS), and Scioto (SCS) sandstone rocks with different clay minerals. ζ-potential measurements were used to investigate the surface charge of the different clays and different sandstone rocks with different fluids. Fluids such as seawater (SW), low-salinity water (LSW), fresh water, and chelating agents were used. Diethylenetriaminepentaacetic acid (DTPA) chelating agent was introduced to mitigate the chlorite effect on oil recovery from sandstone rocks. The wettability was evaluated using contact-angle measurements and the Amott test for different solutions and different rocks in the presence of actual crude oil. Coreflooding experiments were conducted using these fluids with different sandstone rocks to identify the effect of chlorite on the oil recovery.Coreflooding experiments showed that sandstone cores with high chlorite content yielded the lowest oil recovery when SW and LSW were used. The effect of chlorite on the oil recovery from the two sandstone rocks was minimized with 3 wt% DTPA chelating agent. More oil was recovered in the case of DTPA because of the iron chelation from chlorite. ζ-potential showed that sandstone with high chlorite content has a surface charge close to zero in the case of SW and fresh water. In addition, contact-angle measurements showed that samples with high chlorite content have less water-wetness, which will reduce oil recovery. Contact-angle measurements on chlorite sheets showed that chlorite is oil-wet compared with mica at the same conditions. The addition of high-pH DTPA chelating agent sequestered the iron from the chlorite clay minerals and changed the surface charge to very high negative value, and the contact angle confirmed that the rock changed to water-wet after adding the chelating agent. The Amott index showed that adding DTPA increased the water-wetness for SCS that contains 4 wt% chlorite.

Delivery of DTPA through Liposomes as a Good Strategy for Enhancing Plutonium Decorporation Regardless of Treatment Regimen.

In this study, we assessed the efficacy of unilamellar 110-nm liposomes encapsulating the chelating agent diethylenetriaminepentaacetic acid (DTPA) in plutonium-exposed rats. Rats were contaminated by intravenous administration of the soluble citrate form of plutonium. The comparative effects of liposomal and free DTPA at similar doses were examined in terms of limitation of alpha activity burden in rats receiving various treatment regimens. Liposomal DTPA given at 1 h after contamination more significantly prevented the accumulation of plutonium in tissues than did free DTPA. Also, when compared to free DTPA, liposome-entrapped DTPA was more efficient when given at late times for mobilization of deposited plutonium. In addition, repeated injections of liposomal DTPA further improved the removal of plutonium compared to single injection. Various possible mechanisms of action for DTPA delivered through liposomes are discussed. The advantage of liposomal DTPA over free DTPA was undoubtedly directly and indirectly due to the better cell penetration of DTPA when loaded within liposomes, mainly in the tissues of the mononuclear phagocytic system. The decorporation induced by liposomal DTPA may result first from intracellular chelation of plutonium deposited in soft tissues, predominantly in the liver. Afterwards, the slow release of free DTPA molecules from these same tissues may enable a sustained action of DTPA, probably mainly by extracellular chelation of plutonium available on bone surfaces. In conclusion, decorporation of plutonium can be significantly improved by liposomal encapsulation of DTPA regardless of the treatment regimen applied.

Stimulation of high temperature carbonate gas reservoirs using seawater and chelating agents: Reaction kinetics

The use of hydrochloric acid (HCl) in gas well stimulation of high temperature reservoirs is currently facing different challenges. These challenges include rapid corrosion of the well tubulars, face dissolution, very high and uncontrolled reaction rate, and formation damage in high clay content and iron-rich reservoirs. In this study, water-soluble diethylene triamine penta acetic acid (DTPA) chelating agent is introduced as alternative to eliminate the risk associated with HCl at high temperatures. In addition, the potential of using seawater to replace fresh water in the stimulation process is explored to save the cost of fresh water transportation to deep offshore oil and gas wells. The effect of seawater on the reaction kinetics of DTPA with carbonate rocks under high pressure and high temperature conditions is investigated using the rotating disk apparatus. The reactions of DTPA solution diluted with fresh water (DTPA/DI) and seawater (DTPA/SW) with carbonate rocks were carried out at the same conditions. In the case of fresh water, the reaction is controlled by the surface reaction regime. Adding HCl to adjust DTPA pH did not turn the reaction into a mass transfer controlled reaction like the case of using HCl alone. The heavy matrix of seawater increased the resistance of ions diffusion, which resulted in a low reaction rate and transformed the reaction into a mass transfer limited regime. Corrosion tests were carried out on production and coiled tubing coupons obtained from the gas wells and the results of the new DTPA/SW formulation is compared to the standard HCl formulation. DTPA showed very low corrosion rate of 0.0034 g/cm2 without adding corrosion inhibitors compared to 0.205 g/cm2 of 15 wt% HCl with 3% corrosion inhibitors while the industry limit is 0.0244 g/cm2 in 6 h. The reaction regime of DTPA chelating agent with calcite is identified to be mass transfer limited in seawater and surface reaction limited in fresh water. The rate expression for the dissolution of Ca2+ in DTPA/SW solution is obtained. Coreflooding experiments were performed to determine the optimum injection rate using low permeability Indiana limestone core samples. The optimum injection rate required to stimulate a very deep carbonate gas well was found to be 1.4 bbl/min after scaling up the coreflooding results to field scale. The application of the new DTPA/SW formulation in treating deep gas wells is expected to save the cost of fresh water and eliminate the cost of corrosion inhibitors.

Developing a physiologically based approach for modeling plutonium decorporation therapy with DTPA

Purpose: To develop a physiologically based compartmental approach for modeling plutonium decorporation therapy with the chelating agent Diethylenetriaminepentaacetic acid (Ca-DTPA/Zn-DTPA).Materials and methods: Model calculations were performed using the software package SAAM II (©The Epsilon Group, Charlottesville, Virginia, USA). The Luciani/Polig compartmental model with age-dependent description of the bone recycling processes was used for the biokinetics of plutonium.Results: The Luciani/Polig model was slightly modified in order to account for the speciation of plutonium in blood and for the different affinities for DTPA of the present chemical species. The introduction of two separate blood compartments, describing low-molecular-weight complexes of plutonium (Pu-LW) and transferrin-bound plutonium (Pu-Tf), respectively, and one additional compartment describing plutonium in the interstitial fluids was performed successfully.Conclusions: The next step of the work is the modeling of the chelation process, coupling the physiologically modified structure with the biokinetic model for DTPA. Results of animal studies performed under controlled conditions will enable to better understand the principles of the involved mechanisms.

Efficacy of a Novel Orally Administered Formulation of DTPA Tablets for Decorporating an Intravenously Injected Radionuclide: A Comparison with Intravenously Administered Licensed DTPA

Abstract Strategy, Management and Health Policy Enabling Tchnology, Genomics, Proteomics Preclinical Research Preclinical Development Toxicology, Formulation Durg Delivery, Pharmacokinetics Clinical Development Phases I‐III Regulatory, Quality, Manufacturing Postmarketing Phase IV A proprietary minitablet formulation of the chelating agent diethylenetriaminepentaacetic acid (DTPAMT) was administered orally to rats injected with (241 Am) (III)‐citrate and compared with untreated controls. The positive control was intravenously administered diethylenetriaminepentaacetate (DTPA) (IVDTPA). Groups of six young adult rats (three male, three female) were injected intravenously with 241 Am, with each rat placed in an individual metabolism cage for excreta collection. The groups were then treated once with IVDTPA or DTPAMT at 1 h, or 1, 5, or 14 days postinjection, with sacrifice at 8, 8, 12, and 21 days postinjection, respectively. Sacrifice of three untreated control groups occurred 8, 12, and 21 days postinjection. At necropsy, all tissues, associated urine, feces, and cage wash samples were collected and analyzed for (241 Am) content. The average recovery for all experimental groups was 95.2 ± 3.6% administered 241 Am dose. Tissue and excreta analyses of (241 Am) were compared for the treatment groups and untreated controls and with IVDTPA using two‐way analysis of variance. DTPAMT 241 Am removal efficacy was statistically significant for all administration times compared with untreated controls. For systemically administered (241 Am), the primary deposition sites, bone and liver, incurred the highest radiation doses. DTPAMT reduced liver (241 Am) content by 60–70% and bone content by 40% at treatment times of 1 h,1 day, and 5 days when compared with untreated controls. For all times, DTPAMT compared well with IVDTPA. For DTPAMT, (241 Am) excretion elevation in urine was protracted beyond that typically observed with IVDTPA.

Uptake, distribution, and velocity of organically complexed plutonium in corn (Zea mays)

Lysimeter experiments and associated simulations suggested that Pu moved into and through plants that invaded field lysimeters during an 11-year study at the Savannah River Site. However, probable plant uptake and transport mechanisms were not well defined, so more detailed study is needed. Therefore, experiments were performed to examine movement, distribution, and velocity of soluble, complexed Pu in corn. Corn was grown and exposed to Pu using a “long root” system in which the primary root extended through a soil pot and into a hydroponic container. To maintain solubility, Pu was complexed with the bacterial siderophore DFOB (Desferrioxamine B) or the chelating agent DTPA (diethylenetriaminepentaacetic acid). Corn plants were exposed to nutrient solutions containing Pu for periods of 10min to 10d. Analysis of root and shoot tissues permitted concentration measurement and calculation of uptake velocity and Pu retardation in corn. Results showed that depending on exposure time, 98.3–95.9% of Pu entering the plant was retained in the roots external to the xylem, and that 1.7–4.1% of Pu entered the shoots (shoot fraction increased with exposure time). Corn Pu uptake was 2–4 times greater as Pu(DFOB) than as Pu2(DTPA)3. Pu(DFOB) solution entered the root xylem and moved 1.74mh−1 or greater upward, which is more than a million times faster than Pu(III/IV) downward movement through soil during the lysimeter study. The Pu(DFOB) xylem retardation factor was estimated to be 3.7–11, allowing for rapid upward Pu transport and potential environmental release.