ethylenediamine-N,N'-diacetic Acid Research Articles

Synthesis and Bioevaluation of Novel Technetium-99m-Labeled Complexes with Norfloxacin HYNIC Derivatives for Bacterial Infection Imaging.

To seek a novel 99mTc-labeled quinolone derivative for bacterial infection SPECT imaging that aims to lower nontarget organ uptake, a novel norfloxacin 6-hydrazinoicotinamide (HYNIC) derivative (HYNICNF) was designed and synthesized. It was radiolabeled with different coligands, such as tricine, trisodium triphenylphosphine-3,3',3″-trisulfonate (TPPTS), sodium triphenylphosphine-3-monosulfonate (TPPMS), and ethylenediamine-N,N'-diacetic acid (EDDA), to obtain three 99mTc-labeled norfloxacin HYNIC complexes, namely, [99mTc]Tc-tricine-TPPTS-HYNICNF, [99mTc]Tc-tricine-TPPMS-HYNICNF, and [99mTc]Tc-EDDA-HYNICNF. These complexes were purified (RCP > 95%) and evaluated in vitro and in vivo for targeting bacteria. All three complexes are hydrophilic, maintain good stability, and specifically bind Staphylococcus aureus in vitro. The biodistribution in mice with bacterial infection demonstrated that [99mTc]Tc-EDDA-HYNICNF showed a higher abscess uptake and lower nontarget organ uptake and was able to distinguish bacterial infection and sterile inflammation. Single photon emission computed tomography (SPECT) image study in bacterial infection mice showed there was a visible accumulation in the infection site, suggesting that [99mTc]Tc-EDDA-HYNICNF is a potential radiotracer for bacterial infection imaging.

Synthesis, radiolabeling and evaluation of [99mTc][Tc-HYNIC/EDDA]-Met(O) as a early agent for amino acid metabolic imaging in C6 glioblastoma tumor

Amino acid metabolism is recognized as a target for medical imaging due to its increase in malignant cells. Several radiotracers with primary achievement and possible subsequent chances have been designed and tested to image amino acid metabolism. Here, we report a new amino acid conjugate, with the purpose of extending [99mTc][Tc-HYNIC/EDDA]-Met(O) for single photon emission tomography (SPECT) imaging.The S-oxo-l-methionine (Met(O)) amino acid hydrazinonicotinamide (HYNIC) chelator conjugate (HYNIC-Met(O)) was prepared, using Fmoc solid-phase synthesis, and was radiolabeled with [99mTc]technetium pertechnetate, using tricine and ethylenediamine-N,N-diacetic acid (EDDA) as co-ligands. In vitro cellular uptake profile and saturation binding of radiotracer were determined on C6 glioma cells. Biodistribution and imaging studies were carried out on rat bearing C6 tumor tissue grafts.[99mTc][Tc-HYNIC/EDDA]-Met(O) was prepared in high yield and radiochemical purity (>98 %). The partition coefficient result showed that radioconjugate was very hydrophilic. The radioconjugate indicated both high cell uptake and in vitro internalization. Low nanomolar dissociation constant (66.02 nM) in C6 glioma cells was obtained for it as well. [99mTc][Tc-HYNIC/EDDA]-Met(O) revealed magnificent tumor uptake at early time points, with 1.98 ± 0.33 % injected activity per gram tumor (% IA/g) at 30 min post injection. The tumor uptake continued for 1 and 2 h and was 0.45 ± 0.33 % IA/g at 4 h. The uptake in other organs decreased much more rapidly causing high tumor to normal organ ratios so that the highest ratio of 13.25 of tumor-to-muscle at 60 min after injection was obtained with high contrast in gamma imaging.These results point out a very favorable [99mTc]Tc-labeled amino acid for targeting amino acid metabolism through target system L amino acid transporter (LAT1) in malignant cells especially C6 glioma cells. [99mTc][Tc-HYNIC/EDDA]-Met(O) manifests extremely good distribution, excretion and imaging attributes. So it seems to be an appropriate nominate for clinical imaging.

99mTc]-labeling and evaluation of a new linear peptide for imaging of glioblastoma as a αvβ3-positive tumor.

In this study, we designed a new linear 6-Hydrazinonicotinamide (HYNIC)-conjugated peptide (HYNIC-KRWrNM) (M-6) and labeled with technetium-99m for gamma imaging of glioblastoma as a αvβ3-positive tumor. We evaluated tumor targeting ability of this radio-peptide and compared with previous 99mTc-labeled HYNIC-conjugated RGD analogue peptides. One new linear peptide (HYNIC-KRWrNM) (M-6) was designed and labeled with technetium-99m in the presence of 2-[[1,3-dihydroxy-2-(hydroxymethyl) propan-2-yl] amino] acetic acid (Tricine)/Ethylenediamine-N,N'-diacetic acid(EDDA) as co-ligand system. Then, this 99mTc-labeled peptide ([99mTc]Tc-M-7) was evaluated for in vitro stability in saline and serum, specific binding assay, internalization, and binding affinity (Kd). In addition, we performed biodistribution study and planar imaging on nude mice bearing U87-MG xenograft as a αvβ3-positive tumor. The radiochemical yield of [99mTc]Tc-M-7 was obtained ˃95%. This 99mTc-labeled peptide remained stable and intact in saline solution after 24h incubation. In addition, metabolic stability of this 99mTc-labeled peptide was obtained ˃60% after 4h incubation in serum. The Kd value for [99mTc]Tc-M-7 was obtained 5.2 ± 1.0nM. Based on biodistribution results in nude mice bearing U87-MG xenograft, tumor/muscle activity ratio was 6.22 and decreased to 1.89 in blocking group at the same time point (4h p.i.). The blocking experiment results also indicated that tumor uptake and kidney uptake were αvβ3-mediated. In comparison with previous HYNIC-conjugated RGD analogue peptides, kidneys had the highest uptake of this 99mTc-labeled peptide (52.29 ± 11.48 at 1.5h p.i. and 27.04 ± 0.66%ID/g at 4h p.i.). Finally, similar to previous 99mTc-labeled HYNIC-conjugated RGD analogue peptides, [99mTc]Tc-M-7 showed acceptable tumor uptake after 4h post-injection (based on ROI technique, target-to-background activity ratio = 3.80). This small linear 99mTc-labeled peptide, with high affinity to αvβ3 integrin, desirable water solubility, and cost efficient, demonstrates a potent tumor targeting ability as well as previous HYNIC-conjugated RGD analogue peptides. Hence, [99mTc]Tc-M-7 can be of service to as a new candidate for early detection of αvβ3-positive tumors.

Enhanced Degradation of Phenol by a Fenton-Like System (Fe/EDTA/H2O2) at Circumneutral pH

This work deals with the degradation of phenol based on the classical Fenton process, which is enhanced by the presence of chelating agents. Several iron-chelating agents such as ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), diethylenetriamine pentaacetic acid (DTPA), and ethylenediamine-N,N’-diacetic acid (EDDA) were explored, although particular attention was given to EDTA. The effect of the molar ligand to iron ratio, EDTA:Fe, initial pH, and temperature on the oxidation process was studied. The results demonstrate that the proposed alternative approach allows the capacity for degrading phenol to be extended from the usual acidic pH (around 3.0) to circumneutral pH range (6.5–7.5). The overall feasibility of the process depends on the concentration of the chelating agent and the initial pH of the solution. The maximum phenol conversion, over 95%, is achieved using a 0.3 to 1 molar ratio of EDTA:Fe, stoichiometric ratio of H2O2 at an initial pH of 7.0, and a temperature of 30 °C after 2 hours of reaction, whereas only 10% of phenol conversion is obtained without EDTA. However, in excess of ligand (EDTA:Fe > 1), the generation of radicals seems to be strongly suppressed. Improvement of the phenol removal efficiency at neutral pH also occurs for the other chelating agents tested.

Evaluation of 99mTc-Labeled Bevacizumab-N-HYNIC Conjugate in Human Ovarian Tumor Xenografts.

Aim: The aim of the present investigation was to examine the suitability of 99mTc-N-HYNIC-BZMB as a specific vascular endothelial growth factor (VEGF)-targeting agent. Bevacizumab is a recombinant humanized monoclonal antibody that inhibits VEGF. Methods: N-hydroxysuccinimide-2-hydrazinonicotinic acid (N-HYNIC) was conjugated to BZMB, followed by labeling with 99mTc using N-[Tris(hydroxymethyl)methyl] glycine (tricine), ethylenediamine-N,N'-diacetic acid (EDDA), and nicotinic acid as coligands. 99mTc-labeled BZMB was characterized in terms of 99mTcO4, radiocolloids, and labeled N-HYNIC-BZMB using thin-layer chromatography and HPLC. Poor metastatic SKOV-3 and high metastatic SKOV-3.ip1 human ovarian cancer cell lines were used for in vitro binding uptake of 99mTc-N-HYNIC-BZMB. Biodistribution and scintigraphy accuracy were examined in human ovarian tumor xenografts in rats and rabbits. Results: 99mTc-N-HYNIC-BZMB prepared by using a mixture of tricine and EDDA demonstrated relatively high radiochemical purity (more than 98%). In L-cysteine and serum, it exhibited a stable behavior up to 16 h. In vitro binding uptake indicated that it targets high metastatic SKOV-3.ip1 tumors. Biodistribution in human ovarian tumor xenografts in rats confirmed a significant uptake in SKOV-3.ip1 tumors (5.69% ± 1.86%, 4 h). Scintigraphic accuracy in human ovarian tumor xenografts in rabbits validated its suitability as a high metastatic SKOV-3.ip1 radiotracer. Conclusion: High radiochemical purity, stability in saline and serum, biodistribution, and scintigraphy of 99mTc-N-HYNIC-BZMB in human ovarian tumor xenografts in rats and rabbits confirmed its suitability as a potential radiotracer for imaging high metastatic SKOV-3.ip1 sites.

A small heterobifunctional ligand provides stable and water dispersible core-shell CdSe/ZnS quantum dots (QDs).

We describe a simple method to prepare water dispersible core-shell CdSe/ZnS quantum dots (QDs) 1 by capping QDs with a new thiol-containing heterobifunctional dicarboxylic ligand 4 (DHLA-EDADA). This ligand, obtained on a gram scale through a few synthetic steps, provides a compact layer on the QDs, whose hydrodynamic size in H2O is 15 nm ± 3 nm. The colloidal stability is dramatically enhanced with respect to the well-known (±) α-lipoic acid (DHLA). The ligand affinity towards QDs and the water dispersibility of nanocrystals 1 are addressed by the dithiol groups of DHLA, which chelate the zinc of the shell, and by the dicarboxylic groups of the ethylenediamine-N,N-diacetic acid (EDADA) residue, respectively. The effects of pH, buffer solutions, and biological medium on the stability of QDs 1 were assessed by monitoring the photoluminescence (PL) and hydrodynamic size over time. Highly fluorescent QD dispersions, stable over extended periods of time and over broad pH ranges and buffer types, were obtained. Furthermore, we show that the DHLA-EDADA ligand 4 also endows QDs with functional groups suitable for further conjugation and for metal ion detection. As a case study to illustrate the potential of our approach, we report the preparation and characterization of a highly luminescent orange light emitting polymer-QD 1 composite film.

Retraction of "Synthesis and Solution Studies of the Complexes of Trivalent Lanthanides with the Tetraazamacrocycle TETA-(PO)2".

A new potentially multidentate hexaprotic ligand H6[TETA-(PO)2] has been prepared by reaction of ethylenediamine-N,N‘-diacetic acid (EDDA), paraformaldehyde, and phosphinic acid; its coordination properties with three lanthanide ions (La3+, Gd3+, and Lu3+) have been explored. The structures of the complexes were studied in aqueous solution by potentiometric pH titrations and by 31P NMR spectroscopy. Four acidity constants were determined potentiometrically in the range 2.5 < pH < 14. The four measured pKa values can be divided into two groups, and within each group the initial deprotonation was found to have little effect on the second. Variable temperature 31P and 31P{1H} EXSY NMR spectra showed that, for [Lu(TETA-(PO)2)]3-, the two phosphorus atoms exist in different chemical environments and undergo an exchange process which is very fast on the NMR time scale at room temperature. This result is consistent with one of the phosphinate residues coordinating the metal ion and exchanging with a free analogu...

Rates of nickel(II) capture from complexes with NTA, EDDA, and related tetradentate chelating agents by the hexadentate chelating agents EDTA and CDTA: Evidence of a “semijunctive” ligand exchange pathway

Many siderophores and metallophores produced by soil organisms, as well as anthropogenic chelating agent soil amendments, rely upon amine and carboxylate Lewis base groups for metal ion binding. UV–visible spectra of metal ion-chelating agent complexes are often similar and, as a consequence, whole-sample absorbance measurements are an unreliable means of monitoring the progress of exchange reactions. In the present work, we employ capillary electrophoresis to physically separate Ni(II)-tetradentate chelating agent complexes (NiL) from Ni(II)-hexadentate chelating agent complexes (NiY) prior to UV detection, such that progress of the reaction NiL+Y→NiY+L can be conveniently monitored. Rates of ligand exchange for Ni(II) are lower than for other +II transition metal ions. Ni(II) speciation in environmental media is often under kinetic rather than equilibrium control. Nitrilotriacetic acid (NTA), with three carboxylate groups all tethered to a central amine Lewis base group, ethylenediamine-N,N′-diacetic acid (EDDA), with carboxylate-amine-amine-carboxylate groups arranged linearly, plus four structurally related compounds, are used as tetradentate chelating agents. Ethylenediaminetetraacetic acid (EDTA) and the structurally more rigid analog trans-cyclohexaneethylenediaminetetraacetic acid (CDTA) are used as hexadentate chelating agents. Effects of pH and reactant concentration are explored. Ni(II) capture by EDTA was consistently more than an order of magnitude faster than capture by CDTA, and too fast to quantify using our capillary electrophoresis-based technique. Using NiNTA as a reactant, Ni(II) capture by CDTA is independent of CDTA concentration and greatly enhanced by a proton-catalyzed pathway at low pH. Using NiEDDA as reactant, Ni(II) capture by CDTA is first order with respect to CDTA concentration, and the contribution from the proton-catalyzed pathway diminished by CDTA protonation. While the convention is to assign either a disjunctive pathway or adjunctive pathway to multidentate ligand exchange reactions, our results indicate that a third “semijunctive” pathway is necessary to account for slow reactions progressing through LNiY ternary complexes. Ligand exchange pathways with NTA-type chelating agents are assigned a disjunctive pathway, while pathways with EDDA-type chelating agents are assigned a semijunctive pathway. Based upon operative mechanism(s), magnitudes of exchange rates and effects of ambient geochemical conditions can be predicted.

Synthesis and preliminary evaluation of a new (99m)tc labeled substance p analogue as a potential tumor imaging agent.

Neurokinin 1 receptors (NK1R) are overexpressed on several types of important human cancer cells. Substance P (SP) is the most specific endogenous ligand known for NK1Rs. Accordingly,a new SP analogue was synthesized and evaluated for detection of NK1R positive tumors.[6-hydrazinopyridine-3-carboxylic acid (HYNIC)-Tyr(8)-Met(O)(11)-SP] was synthesized and radiolabeled with (99m)Tc using ethylenediamine-N,N'-diacetic acid (EDDA)and Tricine as coligands. Common physicochemical properties of radioconjugate were studied and in-vitro cell line biological tests were accomplished to determine the receptor mediated characteristics. In-vivo biodistribution in normal and tumor bearingnude mice was also assessed. The cold peptide was prepared in high purity (>99%) and radiolabeled with (99m)Tc at high specific activities (84-112GBq/µmol) with an acceptable labeling yield (>95%). The radioconjugate was stable in-vitro in the presence of human serum and showed 44% protein binding to human serumalbumin. In-vitro cell line studies on U373MG cells showed an acceptable uptake up to 4.91 ± 0.22% with the ratio of 60.21 ± 1.19% for its specific fraction and increasing specific internalization during 4 h. Receptor binding assays on U373MG cells indicated a mean Kd of 2.46 ± 0.43 nM and Bmax of 128925 ± 8145 sites/cell. In-vivo investigations determined the specific tumor uptake in 3.36 percent of injected dose per gram (%ID/g) for U373MG cells and noticeable accumulations of activity in the intestines and lung. Predominant renal excretion pathway was demonstrated. Therefore, this new radiolabeled peptide could be a promising radiotracer for detection of NK1R positive primary or secondary tumors.

Evaluation of 99mTc-HYNIC-TMTP1 as a tumor-homing imaging agent targeting metastasis with SPECT

IntroductionTMTP1 (NVVRQ) is a novel tumor-homing peptide, which specifically targets tumor metastases, even at the early stage of occult metastasis foci. Fusing TMTP1 to therapeutic peptides or proteins can increase its anti-cancer efficacy both in vivo and in vitro. Here, we labeled TMTP1 with 99mTc to evaluate its targeting properties in an ovarian cancer xenograft tumor mouse model and a gastric cancer xenograft mouse model. MethodsThe invasion ability of SKOV3 and highly metastatic SKOV3.ip cell lines were performed by the Transwell Invasion Assays, and then Rhodamine-TMTP1 was used to detect its affinity to these two cells. Using the co-ligand ethylenediamine-N, N′-diacetic acid (EDDA) and the bifunctional chelator 6-hydrazinonicotinic acid (HYNIC), the TMTP1 peptide was labeled with 99mTc. A cell-binding assay was performed by incubating cancer cells with 99mTc-HYNIC-TMTP1 with or without an excess dose of cold HYNIC-TMTP1. To evaluate the probe in vivo, nude mice bearing SKOV3, SKOV3.ip and MNK-45 tumor cells were established and subjected to SPECT imaging after injection with 99mTc-HYNIC-TMTP1. Ex vivo γ-counting of dissected tissues from the mice was used to evaluate its biodistribution. Results99mTc-HYNIC-TMTP1 was successfully synthesized. The radiotracer also exhibited high hydrophilicity and excellent stability in vitro and in vivo. It has strong affinity to highly metastatic cancer cell lines but not to poorly metastatic cell lines. After mice were injected with 99mTc-HYNIC-TMTP1, non-invasive SPECT imaging detected SKOV3.ip and MNK-45 xenograft tumors but not SKOV3 xenograft tumors. This result can be inhibited by excess HYNIC-TMTP1. The uptake of 99mTc-HYNIC-TMTP1 in SKOV3.ip xenograft tumors was 0.182±0.017% ID/g at 2h p.i. with high renal uptake (74.32±15.05% ID/g at 2h p.i.). Conclusion99mTc-HYNIC-TMTP1 biodistribution and SPECT imaging demonstrated its ability to target highly metastatic tumors. Therefore, metastasis can be non-invasively investigated by SPECT imaging using 99mTc-HYNIC-TMTP1. Meanwhile, this radiotracer has some shortages in the low % ID/g of tumors and high accumulation in the kidney.

Synthesis and biological evaluation of novel technetium-99m-labeled HYNIC-d-glucose as a potential tumor imaging agent

A conjugate of 6-hydrazinopyridine-3-carboxylic acid (HYNIC) with the d-Glucosamine Hydrochloride (DG) was synthesized though a multiple-step reaction. HYNIC-DG could be labeled successfully and efficiently with 99mTc using N-[2-hydroxy-1,1-bis(hydroxymethyl)ethyl]glycine (tricine) and ethylenediamine-N,N′-diacetic acid (EDDA) or tricine and triphenylphosphine-3,3′,3″-trisulfonic acid trisodium salt (TPPTS) as co-ligands to form two 99mTc-HYNIC-DG complexes 99mTc-(t/E)HYNIC-DG and 99mTc-(t/T)HYNIC-DG in high yields (>95 %). The partition coefficient and electrophoresis results indicated they were very hydrophilic and electronegative. The biodistribution studies of two 99mTc-HYNIC-DG complexes in Kunming mice bearing S 180 tumor showed that 99mTc-(t/T)HYNIC-DG has more favorable characteristics than 99mTc-(t/E)HYNIC-DG. High tumor uptake, low or negligible accumulation in non-target organs, and good retention, suggesting 99mTc-(t/T)HYNIC-DG would be a novel potential tumor imaging agent.

Kit preparation and biokinetics in women of 99mTc-EDDA/HYNIC-E-[c(RGDfK)]2 for breast cancer imaging

In breast cancer, α(ν)β(3) and/or α(ν)β(5) integrins are overexpressed in both endothelial and tumour cells. Radiolabelled peptides based on the Arg-Gly-Asp (RGD) sequence are radiopharmaceuticals with high affinity and selectivity for these integrins. The RGD-dimer peptide (E-[c(RGDfK)]2) radiolabelled with (99m)Tc has been reported as a radiopharmaceutical with a 10-fold higher affinity for the α(ν)β(3) integrin compared with the RGD-monomer. Ethylenediamine-N,N'-diacetic acid (EDDA) is a hydrophilic molecule that may favour renal excretion when used as coligand in the (99m)Tc labelling of hydrazinonicotinamide (HYNIC) peptides and can easily be formulated in a lyophilized kit. The aim of this study was to establish a biokinetic model for (99m)Tc-EDDA/HYNIC-E-[c(RGDfK)]2 prepared from lyophilized kits and evaluate its dosimetry as a tumour-imaging agent in seven healthy women and three breast cancer patients. (99m)Tc labelling was performed by adding sodium pertechnetate solution and 0.2 mol/l phosphate buffer (pH 7.0) to a lyophilized formulation containing E-[c(RGDfK)]2, EDDA, tricine, mannitol and stannous chloride. The radiochemical purity was evaluated using reverse-phase high-performance liquid chromatography and instant thin-layer chromatography on silica gel analyses. Stability studies in human serum were carried out using size-exclusion high-performance liquid chromatography. In-vitro cell uptake was tested using breast cancer cells (MCF7, T47D and MDA-MB-231) with blocked and nonblocked receptors. Biodistribution and tumour uptake were determined in MCF7 tumour-bearing nude mice with blocked and nonblocked receptors, and images were obtained using a micro-SPECT/PET/CT. Whole-body images from seven healthy women were acquired at 0.5, 1, 3, 6 and 24 h after (99m)Tc-EDDA/HYNIC-E-[c(RGDfK)]2 administration with radiochemical purities greater than 94%. Regions of interest were drawn around the source organs at each time frame. Each region of interest was converted to activity using the conjugate view counting method. The image sequence was used to extrapolate the (99m)Tc-EDDA/HYNIC-E-[c(RGDfK)]2 time-activity curves of each organ to adjust the biokinetic model and calculate the total number of disintegrations (N) that occurred in the source regions. N data were the input for the OLINDA/EXM code to calculate internal radiation dose estimates. In three breast cancer patients with histologically confirmed cancer, static images were obtained at 1 h in the supine position with hands placed behind the head. (99m)Tc-EDDA/HYNIC-E-[c(RGDfK)]2 obtained from lyophilized kits demonstrated high stability in human serum and specific cell receptor binding. The biodistribution data from mice showed rapid blood clearance, with both renal and hepatobiliary excretion, and specific binding towards α(ν)β(3) integrins in the MCF7 tumours. In women, the blood activity showed a half-life value of 1.60 min for the fast component (T1/2α = ln2/26.01) and half-life values of 1.0 h for the first slow component (T1/2β = ln2/0.69) and 4.03 h for the second slow component (T1/2γ = ln2/0.16). Images from patients showed an average tumour/heart (blood) ratio of 3.61 ± 0.62 at 1 h. The average equivalent doses calculated for a study using 740 MBq were 4.9, 6.2, 20.7, 34.5 and 57.0 mSv for the liver, intestines, spleen, kidneys and thyroid, respectively, and the effective dose was 6.1 mSv. All absorbed doses were comparable to those known from most of the (99m)Tc studies. (99m)Tc-EDDA/HYNIC-E-[c(RGDfK)]2 obtained from kit formulations showed high tumour uptake in patients with malignant lesions, making it a promising imaging radiopharmaceutical for targeting site-specific breast cancer. The results obtained in this study warrant further clinical studies to determine the specificity and sensitivity of (99m)Tc-EDDA/HYNIC-E-[c(RGDfK)]2.

An improved radiolabelled RNA aptamer molecule for HER2 imaging in cancers

Human epidermal growth factor receptor 2 (HER2) expression has been shown to be increased in several types of human tumours. In this study, for the imaging of HER2-related tumours, a modified RNA aptamer with HER2-specific targeting was labelled with 99mTc, by using hydrazino nicotinamide (HYNIC) as the chelator in the presence of tricine or ethylenediamine-N,N′-diacetic acid (EDDA) as the co-ligand. Stability testing of the radiolabelled aptamers in the serum was performed through SDS-PAGE. The aptamer–radionuclide conjugate was evaluated for its cellular HER2-specific binding in ovarian cancer cells (SKOV-3), and its biodistribution properties were assessed in normal and SKOV-3 tumour-bearing mice. In the presence of either tricine or EDDA, the HYNIC-RNA aptamers were labelled with 99mTc at a high yield and radiochemical purity. Cellular experiments confirmed the specific binding of the RNA aptamer to the HER2 receptor. In the animal biodistribution study, uptake of the EDDA-co-liganded 99mTc-HYNIC-RNA aptamer by the liver and spleen was remarkably lower than that of the aptamer with tricine. Tumours also showed a higher accumulation of radioactivity with the EDDA-co-liganded aptamer complex. This study demonstrated EDDA to be better than tricine for use as a co-ligand with the RNA aptamer, which can be a potential tool for the molecular imaging of HER2-overexpressing cancers.

Preparation and Biological Evaluation of [99mTc/EDDA/Tricine/HYNIC0, BzThi3]-Octreotide for Somatostatin Receptor-Positive Tumor Imaging

Somatostatin-derived analogues play an important role in the diagnosis and treatment of neuroendocrine tumors. The aim of this study was to evaluate a new somatostatin analogue designed for labeling with (99m)Tc: [6-hydrazinopyridine-3-carboxylic acid (HYNIC(0)), β-(3-benzothienyl)-Ala (BzThi(3))]-octreotide ([HYNIC]-BOC), using ethylenediamine-N,N'-diacetic acid (EDDA) and tricine as coligands. Synthesis was performed on a solid phase using a standard Fmoc strategy. The HYNIC-peptide conjugate was radiolabeled with (99m)Tc and characterized by ITLC and high-performance liquid chromatography (HPLC). In vitro studies were carried out in sstr2 expressing AR4-2J cell lines. In vivo distribution studies were performed in rats bearing the AR4-2J tumor. The radiolabeled complex could be prepared at high-specific activities and >95% radiochemical yield as determined by HPLC. The peptide conjugate showed high-affinity binding for sstr2. The radioligand showed high and specific internalization into AR4-2J cells (18.19%±0.21% at 4 hours). In vivo distribution studies in rats bearing tumor have shown a receptor-specific uptake of radioactivity in somatostatin receptor-positive organs. After 4 hours, uptake in the AR4-2J tumor was 1.71%±0.36% injected dose per gram tissue (%ID/g). These data show that [(99m)Tc/EDDA/Tricine/HYNIC(0), BzThi(3)]-octreotide is a specific radioligand for the somatostatin receptor-positive tumors and is a suitable candidate for clinical studies.

Synthesis and molecular study of a new NMB analogue (BBN) for imaging prostate cancer

Radiolabeled somatostatin analogues are important tools for the in vivo localization and targeted radionuclide therapy of somatostatin-receptor-positive tumors. The aim of this study was to evaluate a new somatostatin analogue designed for the labeling with 99mTc: [6-hydrazinopyridine-3-carboxylic acid (HYNIC0), 1-Nal3, Thr8]-octreotide ([HYNIC]-NATE), using ethylenediamine-N,N′-diacetic acid (EDDA) and tricine as coligands.Synthesis was preformed on a solid phase using a standard Fmoc strategy. Labeling with 99mTc was performed at 100°C for 10 min using SnCl2 as a reductant. Radiochemical analysis involved ITLC and high-performance liquid chromatography methods. Peptide conjugate affinity was determined in AR4-2J cell membranes. The internalization and externalization rates were studied in sstr2-expressing AR4-2J cells. Biodistribution of radiopeptide was studied in rats bearing the AR4-2J tumor.Radiolabeling was performed at high specific activities, and radiochemical purity was >95%. Peptide conjugate showed high affinity binding for sstr2. The radioligand showed a moderate and specific internalization into AR4-2J cells (14.13±0.61% at 4 h). In animal biodistribution studies, a receptor-specific uptake of radioactivity was observed in somatostatin-receptor-positive organs. After 4 h, uptake in the AR4-2J tumor was 1.33±0.23%ID/g (percentage of injected dose per gram of tissue).These data show that [99mTc/EDDA/tricine/HYNIC]-NATE is a specific radioligand for the somatostatin-receptor-positive tumors and is a suitable candidate for clinical studies.

Efficient Methanolytic Cleavage of Phosphate, Phosphonate, and Phosphonothioate Esters Promoted by Solid Supported Lanthanide Ions

The methanolyses of three neutral organophosphorus esters, namely paraoxon (O,O-diethyl O-p-nitrophenyl phosphate (12), O-ethyl O-p-nitrophenyl methylphosphonate (13), O-ethyl S-3,5-dichlorophenyl methylphosphonothioate (14, a model for VX), and an anionic phosphonate ester, O-hydrogen S-3,5-dichlorophenyl methylphosphonothioate (15, a model for a toxic hydrolytic decomposition product of VX known as EA2192)), promoted by solid supported lanthanide ion catalysts (La3+, Sm3+, Eu3+, Yb3+) were investigated at 25 °C under sspH controlled conditions in methanol. The supports were derived from commercially available chlorobenzylated silica and chloromethylated polystyrene functionalized with two chelating ligands, iminodiacetic acid (IDA) and ethylenediamine-N,N′-diacetic acid (EDDA), followed by exposure to Ln3+ ions. The catalysts showed good activity at two investigated sspH values of 8.8 and 11 (in methanol). Despite the fact that the methoxide promoted reactions for the four substrates span a range of ∼20...

99mTc-labeling of Peptidomimetic Antagonist to Selectively Target αvβ3 Receptor-Positive Tumor: Comparison of PDA and EDDA as Co-Ligands

OBJECTIVES: The aim of this research was to synthesize radiolabeled peptidomimetic integrin alpha(v)beta(3) antagonist with (99m)Tc for rapid targeting of integrin alpha(v)beta(3) receptors in tumor to produce a high tumor to background ratio. METHODS: The amino terminus of 4-[2-(3,4,5,6-tetra-hydropyrimidin-2-ylamino)-ethyloxy]benzoyl-2-(S)-[N-(3-amino-neopenta-1-carbamyl)]-aminoethylsulfonyl-amino-beta-alanine hydrochloride (IAC) was conjugated with N-hydroxysuccinimide ester of HYNIC and labeled with (99m)Tc using tricine with either 1,5-pyridinedicarboxylic acid (PDA) or ethylenediamine-N,N'-diacetic acid (EDDA) as the co-ligand. The products, (99m)Tc EDDA(2)/HYNIC-IAC (P1) and (99m)Tc PDA (tricin)/HYNIC-IAC (P2) were subjected to in vitro serum stability, receptor-binding, biodistribution and imaging studies. RESULTS: P1 and P2 were synthesized with an overall yield of >80%. P1 was slightly more stable than P2 when incubated in serum at 37 degrees C for 18 hrs (84 vs 77% intact). The In vitro receptor-binding of P1 was higher than that of P2 (78.02 +/- 13.48 vs 51.05 +/- 14.05%) when incubated with alpha(v)beta(3) at a molar excess (0.8 muM). This receptor binding was completely blocked by a molar excess of an unlabeled peptidomimetic antagonist. Their differences shown in serum stability and the receptor-binding appeared to be related to their biological behaviors in tumor uptake and retention; the 1 h tumor uptakes of P1 and P2 were 3.17+/-0.52 and 2.13+/-0.17 % ID/g, respectively. P1 was retained in the tumor longer than P2. P1 was excreted primarily through the renal system whereas P2 complex was excreted equally via both renal and hepatobiliary systems. Thus, P1 was retained in the whole-body with 27.25 +/- 3.67% ID at 4 h whereas 54.04 +/- 3.57% ID of P2 remained in the whole-body at 4 h. This higher whole-body retention of P2 appeared to be resulted from a higher amount of radioactivity retained in liver and intestine. These findings were supported by imaging studies showing higher tumor-to-abdominal contrast for P1 than for P2 at 3 h postinjection. CONCLUSIONS: P1 showed good tumor targeting properties with a rapid tumor uptake, prolonged tumor retention and fast whole-body clearance kinetics. These findings warrant further investigation of the HYNIC method of (99m)Tc labeling of other peptidomimetic antagonists using EDDA as a coligand.

Application of the Parabolic Model, Specific Ion Interaction, and Debye−Hückel Theories for the Complexation of Dioxovanadium(V) with Ethylenediamine-N,N′-diacetic Acid

Interaction between dioxovanadium(V) and ethylenediamine-N,N′-diacetic acid (EDDA) has been investigated by potentiometric and UV spectrophotometric measurements in an aqueous solution of pH = 1.00 to 2.50 at I = (0.1 to 0.9) mol·dm−3 (NaClO4) and 25 °C. Different speciation models were used to detect the species, but the model that best fits the experimental data takes into account the formation of two species, VO2H2L+ and VO2HL. Distribution diagrams for the main species at different ionic strengths have been calculated as a function of pH. The dependence on ionic strength of the stability and dissociation constants was studied by using the extended Debye−Hückel-type equation (EDH), specific ion interaction theory (SIT), and the parabolic model. All of these approaches gave comparable and satisfactory results. Literature data were also considered and compared.

Estimation of the association and dissociation rate constants of Cd complexes with various aminopolycarboxylic acids by an exchange method

Environmental context. Phytoremediation is a potential way to remove cadmium from polluted soils. The process of plant uptake of cadmium can be enhanced by the addition of chelating compounds. The ability of roots to effectively take up Cd when bound to these complexes is dependent on the speed at which the Cd is associated or dissociated (bound or unbound) from the complex. An exchange method is used here to estimate these association and dissociation rates for a series of Cd–aminopolycarboxylate complexes (some of which have been tested elsewhere in phytoextraction studies). The results of these studies may make it possible to better model the bioavailability of Cd to plant roots. Abstract. Plant uptake of Cd depends not only on the concentration of Cd2+ in the soil solution but also on Cd complexes, the contribution of the latter depending on their association (ka) and dissociation (kd) rate constants. We used a previously designed exchange method to estimate ka and kd constants of Cd complexed with chelates of the aminopolycarboxylic acid series, i.e. ethylenediamine-N,N′-diacetic acid (EDDA), nitrilotriacetic acid (NTA), N-(2-hydroxyethyl)ethylene-diamine-N,N′,N′-triacetic acid (HEDTA), ethylenediaminetetraacetic acid (EDTA), ethylene glycol-bis(2-aminoethyl)-N,N,N′,N′-tetraacetic acid (EGTA), and trans-1,2-diaminocyclohexane-N,N,N′,N′-tetraacetic acid (CDTA) for future mechanistic modelling of Cd bioavailability including the lability of complexes. The precision of ka and kd estimates depended on the stability of the complexes. For the chelates with the highest stability, HEDTA, EDTA, EGTA and CDTA, the constants were estimated with a good precision. The knowledge of these constants enables improved modelling of bioavailability of Cd to plant roots by considering the contribution of Cd-complexes.

Critical evaluation of three indirect assays for quantifying phytosiderophores released by the roots of Poaceae

SummaryIndirect assays are commonly used to measure phytosiderophore (PS) concentrations in the root exudates of grasses. The Cu‐mobilizing, Cu‐CAS and Fe‐binding assays are three commonly used assays but there have been few published attempts to validate or calibrate them rigorously. Thus, we undertook to compare, validate and, where appropriate, to improve and/or optimize each assay. Ethylenediamine‐N,N′‐diacetic acid (EDDA) and N‐2‐hydroxyethylethylenediamine‐N,N′,N′‐triacetic acid (HEDTA) bracket deoxymugineic acid for binding strength with both Fe and Cu and were thus used as model ligands. For the Cu‐mobilizing assay, reasonable regressions (as R2) were obtained between measured and known ligand concentrations for all resin combinations tested. However, the relationship was non‐stoichiometric; less than 5% of the ligand present was recovered as a Cu‐complex. Testing of the Cu‐CAS assay yielded good 1:1 stoichiometric relationships (slopes of 0.97 and 1.08 for EDDA and HEDTA, respectively) with little scatter (R2= 0.97). However, the limits of quantification were approximately 30 μm, which is greater than concentrations generally found in root‐exudate collections. Thus, the Cu‐CAS assay is best suited to situations where large concentrations of PSs are expected. Results from the original Fe‐binding assay indicated a lack of linearity and considerable scatter (R2= 0.57 for EDDA; R2= 0.28 for HEDTA). Thus, as published, use of the original Fe‐binding assay is not recommended. The effects of filter paper, FeCl3 reagent concentration and increase in the reduction time were tested and a revised Fe‐binding assay developed with both good stoichiometry and great precision (R2≥ 0.99). We suggest the use of the revised Fe‐binding assay in most situations where PS concentration would be expected to be &lt; 30 μm.