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Photochemistry is a rich source of inspiration for developing alternative methods to functionalize proteins with drug molecules, fluorophores, and radioactive probes. Here, we report the synthesis and photochemical reactivity of a modified diethylenediamine pentaacetic acid chelate that was derivatized with a light-responsive aryl azide group (DTPA-PEG 3 -ArN 3 , compound 1 ). The corresponding nonradioactive and radioactive nat/68 Ga 3+ and nat/111 In 3+ complexes of DTPA-PEG 3 -ArN 3 were synthesized and their physical and photochemical properties were studied to evaluate the potential of employing this ligand system in the photochemical synthesis of radiolabeled antibodies. Photodegradation kinetics revealed that irradiation with ultraviolet light (365 nm) induced rapid photoactivation of compound 1 and the metal complexes nat/68 Ga- 1 - and nat/111 In- 1 - . Light-induced reactions were complete in <100 s, with measured first-order rate constants of 0.078 ± 0.045 s -1 , 0.093 ± 0.009 s -1 , and 0.117 ± 0.054 s -1 ( n = 2, per species) for compound 1 , nat Ga- 1 - , and nat In- 1 - , respectively. Photochemically induced bioconjugation reactions between DTPA-PEG 3 -ArN 3 and the monoclonal antibody trastuzumab, as well as pre- and postconjugation 68 Ga- and 111 In-radiolabeling experiments, were performed using either a one-pot or two-step strategy. Both approaches yielded radiolabeled trastuzumab ([ 68 Ga]GaDTPA-azepin-trastuzumab) with average radiochemical conversions of 3.9 ± 1.0% ( n = 4, one-pot), and 10.0 ± 1.0% ( n = 3, two-step). One-pot radiolabeling reactions with [ 111 In]InCl 3 produced the corresponding [ 111 In]InDTPA-azepin-trastuzumab radiotracer in a similar radiochemical conversion of 5.4 ± 0.8% ( n = 3). Radiochemical conversions for the desired bimolecular coupling between the chelate and the protein were comparatively low. This observation is likely caused by the high photoinduced reactivity of the compounds and subsequent competition with background reactions. Nevertheless, access to DTPA-PEG 3 -ArN 3 increases the scope of photoradiochemical methods to include metal ions like In 3+ that form complexes with higher coordination numbers.

Diethylenetriamine penta-acetic acid (DTPA), when complexed with a gamma (γ)-emitter radioisotope like 99m Tc, is used for renal function diagnosis and many other diagnostic applications. The main aim of this study was to develop a novel and versatile single-step methodology for the synthesis of a new 177 Lu-labeled radiopharmaceutical with high radiochemical yield, which can be used for diagnostic purposes and therapeutic purposes also. The single and well-defined 177 Lu-DTPA complex was radiochemically characterized by paper chromatography, thin-layer chromatography, high-performance liquid chromatography, and electrophoresis techniques. Dependence of the labeling yield of 177 Lu-DTPA complex on different factors was studied in detail. Biological evaluation was also performed in a normal rabbit by developing images under a γ camera at various time intervals. More than 99% labeling yield was obtained by reacting DTPA with 177 Lu at specific conditions (pH 7.0, 15 minutes reaction time at 100 °C). 177 Lu-DTPA complex showed high stability both at room temperature and in vitro. Biodistribution studies in normal mice indicated the fractional renal uptake of intravenously administered 177 Lu-DTPA complex, which reached in the kidneys within 2-3 minutes. Scintigraphy showed rapid clearance from the body. Based on these results, we propose that 177 Lu-DTPA complex might be used as an ideal candidate for functional evaluation of kidneys and the urinary tract, especially when needed to be transported to long-range consumer sites, because of its suitable half-life., (© 2019 Wiley Periodicals, Inc.)

Clinically used iodinated computer tomography (CT) contrast agents suffer from low sensitivity, and the emerging lanthanide-chelates and CT imaging nanoagents raise great safety concerns. The fusion of high sensitivity and good biocompatibility is highly desired for the development of CT contrast agents. Herein, we propose a facile and green one-pot synthesis strategy for the fabrication of a small molecular CT contrast agent, Bi-diethylene triamine pentaacetate acid (DTPA) complex, for high-performance CT and spectral CT imaging. The Bi-DTPA exhibits yield of near 100%, outstanding water solubility, favorable biocompatibility, large-scale production capability, and superior X-ray attenuation ability, and is successfully applied in high-quality in vivo kidney imaging and gastrointestinal tract CT imaging and appealing spectral CT imaging. The proposed contrast agent can be rapidly excreted from body, avoiding the potential side effects caused by the long-term retention in vivo. Furthermore, our design shows great potential in developing diverse multifunctional contrast agents via chemical modification. The proposed Bi-DTPA with unique superiorities shows a bright prospect in clinic CT imaging, especially spectral CT imaging, and lays down a new way for the design of high-performance CT contrast agents with great clinical transformation potential., (Copyright © 2019. Published by Elsevier Ltd.)

Background and Purpose: Niosomes are nonionic surfactant-based vesicles that exhibit certain unique features which make them favorable nanocarriers for sustained drug delivery in cancer therapy. Biodistribution studies are critical in assessing if a nanocarrier system has preferential accumulation in a tumor by enhanced permeability and retention effect. Radiolabeling of nanocarriers with radioisotopes such as Technetium-99m ( 99m Tc) will allow for the tracking of the nanocarrier noninvasively via nuclear imaging. The purpose of this study was to formulate, characterize, and optimize 99m Tc-labeled niosomes., Methods: Niosomes were prepared from a mixture of sorbitan monostearate 60, cholesterol, and synthesized D-α-tocopherol polyethylene glycol 1000 succinate-diethylenetriaminepentaacetic acid (synthesis confirmed by 1 H and 13 C nuclear magnetic resonance spectroscopy). Niosomes were radiolabeled by surface chelation with reduced 99m Tc. Parameters affecting the radiolabeling efficiency such as concentration of stannous chloride (SnCl 2 ·H 2 O), pH, and incubation time were evaluated. In vitro stability of radiolabeled niosomes was studied in 0.9% saline and human serum at 37°C for up to 8 hours., Results: Niosomes had an average particle size of 110.2±0.7 nm, polydispersity index of 0.229±0.008, and zeta potential of -64.8±1.2 mV. Experimental data revealed that 30 µg/mL of SnCl 2 ·H 2 O was the optimal concentration of reducing agent required for the radiolabeling process. The pH and incubation time required to obtain high radiolabeling efficiency was pH 5 and 15 minutes, respectively. 99m Tc-labeled niosomes exhibited high radiolabeling efficiency (>90%) and showed good in vitro stability for up to 8 hours., Conclusion: To our knowledge, this is the first study published on the surface chelation of niosomes with 99m Tc. The formulated 99m Tc-labeled niosomes possessed high radiolabeling efficacy, good stability in vitro, and show good promise for potential use in nuclear imaging in the future., Competing Interests: Disclosure The authors report no conflicts of interest in this work.

Macroautophagy is a complex degradative intracellular process by which long-lived proteins and damaged organelles are cleared. Common methods for the analysis of autophagy are bulk measurements which mask organelle heterogeneity and complicate the analysis of interorganelle association and trafficking. Thus, methods for individual organelle quantification are needed to address these deficiencies. Current techniques for quantifying individual autophagy organelles are either low through-put or are dimensionally limited. We make use of the multiparametric capability of mass cytometry to investigate phenotypic heterogeneity in autophagy-related organelle types that have been isolated from murine brain, liver, and skeletal muscle. Detection and phenotypic classification of individual organelles were accomplished through the use of a lanthanide-chelating membrane stain and organelle-specific antibodies. Posthoc sample matrix background correction and nonspecific antibody binding corrections provide measures of interorganelle associations and heterogeneity. This is the first demonstration of multiparametric individual organelle analysis via mass cytometry. The method described here illustrates the potential for further investigation of the inherently complex interorganelle associations, trafficking, and heterogeneity present in most eukaryotic biological systems.

The increasing threats of nuclear terrorism have made the development of medical countermeasures a priority for international security. Injectable formulations of diethylenetriaminepentaacetic acid (DTPA) have been approved by the FDA; however, an oral formulation is more amenable in a mass casualty situation. Here, the diethyl ester of DTPA, named C2E2, is investigated for potential as an oral treatment for internal radionuclide contamination. C2E2 was synthesized and characterized using NMR, MS, and elemental analysis. The physiochemical properties of solubility, lipophilicity, and stability were investigated in order to predict its oral bioavailability. Finally, an animal efficacy study was conducted in Sprague Dawley rats pre-contaminated by intramuscular injection with (241)Am(NO3)3 to establish effectiveness of the therapy via the oral route. Synthesis of C2E2 yielded a crystalline powder with high solubility and improved lipophilicity over DTPA. The ester was stable in both simulated gastric and intestinal fluids over the anticipated time course of absorption. Capsules containing C2E2 were demonstrated to be stable for 12 months under accelerated stability conditions. After a single dose, C2E2 enhanced the elimination of (241)Am in a dose-dependent manner. Significant improvement was seen in both total (241)Am decorporation and reduction of (241)Am liver and skeletal burden. C2E2 was concluded to be effective when orally administered to (241)Am-contaminated rats. It may therefore have potential for medical countermeasure in treating humans contaminated with (241)Am or other transuranic elements. An oral capsule or powder for reconstitution may be suitable formulations for future development based on the physiochemical properties and anticipated dose required for efficacy.

Objective: The objective of this study was to explore the potential of (99m)Tc carbonyl labeled DTPA-bevacizumab as a tumor imaging agent. Bevacizumab (Avastin) is a humanized monoclonal antibody (MoAb) that inhibits the vascular endothelial growth factor (VEGF)., Methods: Bevacizumab was conjugated with paraisothiocyanatobenzyl diethylenetriamine pentaacetic acid (p-SCN-Bn-DTPA) and subsequently radiolabeled with (99m)Tc via the (99m)Tc carbonyl synthon. The radioconjugate after purification was characterized by SE-HPLC and its in vitro stability was determined by histidine challenge experiments. Biodistribution studies to determine the uptake by tumors were carried out in melanoma model., Results: The radiochemical purity of (99m)Tc carbonyl labeled antibody was >98 %. The radiolabeled antibody exhibited good stability in the histidine challenge experiments up to 24 h when stored at 37 °C. Biodistribution studies in mice bearing melanoma showed significant tumor uptake (6.9 ± 2.2 % ID/g at 24 h p.i.) which was reduced to 1.6 ± 0.4 % ID/g on co-injection with cold Bevacizumab., Conclusions: The (99m)Tc carbonyl-DTPA-bevacizumab conjugate with good radiochemical purity, excellent stability and good specificity for VEGF indicates its potential as a radioimmunoscintigraphy agent for various cancers.

A highly versatile synthetic strategy is described to generate multimodal and multivalent platforms based on a diethylenetriaminepentaacetic (DTPA) core. Compounds with different functionalization patterns, from mono- to pentamodal, have been prepared using robust and simple chemistry.

Human hepatocellular carcinoma (HCC) is one of the major causes of death worldwide. To investigate the relative importance of active and passive targeting strategies, the synthesis, characterization, in vitro uptake, and in vivo biodistribution of specific sulfapyridine HPMA (HPMA: N-(2-hydroxypropyl methacrylamide)) copolymer (sulfapyridine: SPD) conjugates, nonspecific HPMA copolymer conjugates, and DTPA are described in this study. The poly(HPMA)-SPD-DTPA (DTPA: diethylenetriaminepentaacetic acid), poly(HPMA)-DTPA, and DTPA conjugates were radiolabeled with the radionuclide (99m)Tc and tested for uptake by cultured H22 cells. The cellular accumulation of poly(HPMA)-SPD-DTPA-(99m)Tc complex was found to be time-dependent. The poly(HPMA)-SPD-DTPA-(99m)Tc tracer exhibited rapid uptake kinetics in cell culture with a t(1/2) of ~5 min. The uptake of poly(HPMA)-SPD-DTPA-(99m)Tc was significantly higher than that of poly(HPMA)-DTPA-(99m)Tc, indicating that the uptake of the poly(HPMA)-SPD-DTPA-(99m)T was active binding. The uptake of poly(HPMA)-DTPA-(99m)Tc was significantly higher than that of DTPA-(99m)Tc, suggesting that the uptake of the poly(HPMA)-DTPA-(99m)T was passive binding. Twenty-four hour necropsy data in the hepatocellular carcinoma tumor model showed significantly higher (p < 0.001) tumor localization for poly(HPMA)-SPD-DTPA-(99m)Tc (4.98 ± 0.48%ID/g [percentage injected dose per gram tissue]) compared with poly(HPMA)-DTPA-(99m)Tc (2.69 ± 0.15% ID/g) and DTPA-(99m)Tc (0.83 ± 0.03%ID/g). Moreover, higher T/B for poly(HPMA)-SPD-DTPA-(99m)Tc indicated reduced extravazation of the targeted polymeric conjugates in normal tissues. Specific molecular targeting and nonspecific vascular permeability are both significant in the relative tumor localization of poly(HPMA)-SPD-DTPA-(99m)Tc. Extravascular leak in nonspecific organs appears to be a major factor in reducing the T/B for the sulfapyridine molecules. Thus, the poly(HPMA)-SPD-DTPA is expected to be used as the potential macromolecular targeting carrier for hepatoma carcinoma in mice.

The convenient and efficient synthesis of two macrocyclic ligands (15- and 18-membered) based on a dipyrido-6,7,8,9-tetrahydrophenazine (dpqc) or 2,2':6',2''-terpyridine (tpy) heterocycle and a DTTA (diethylenetriaminetriacetic acid) skeleton is described. In these ligands the DTTA skeleton contains an additional extracyclic functionality (NH(2) group) suitable for covalent attachment to bioactive molecules. These octa- and nonadentate ligands form very stable and luminescent neutral lanthanide complexes in aqueous solutions at physiological pH. The corresponding Eu(III) and Tb(III) complexes are characterized by a maximum absorption wavelength compatible with nitrogen laser excitation (337 nm) and attractive lifetimes and quantum yields. Further introduction of a maleimide bioconjugatable handle in the Eu(III) complexes was investigated and a valuable luminescence brightness above 1500 dm(3) mol(-1) cm(-1) at 337 nm was obtained with the corresponding Eu(III) tpy-derivative. Finally, these two luminescent chelates were grafted onto thiol residues of a model antibody (Mab GSS11) without loss of their luminescent properties.

Purpose: The aim of the study is to assess the feasibility of imaging specific activity of myeloperoxidase (MPO), a leukocyte-derived enzyme with important role in atherosclerosis, by SPECT/CT using a novel radiotracer, (111)In-bis-5-hydroxytryptamide-diethylenetriamine-pentaacetate ((111)In-bis-5HT-DTPA)., Methods: Bis-5HT-DTPA was synthesized. Oligomerization of bis-5HT-DTPA in the presence of MPO/H(2)O(2) was studied and confirmed using MALDI-TOF. Apolipoprotein E knockout (ApoE KO) mice was used as an atherosclerosis-prone rodent model. Biodistribution assay and micro SPECT/CT imaging were carried out to prove the atherosclerosis targeting of (111)In-bis-5HT-DTPA in the ApoE KO mice., Results: MALDI-TOF spectrum showed that the 5HT base agent can self oligomerize after activating by MPO. From the biodistribution study, (111)In-bis-5HT-DTPA was quantified to be retained markedly higher while eliminated much slower in the aortas of the ApoE KO mice than that of the wild type (WT) mice within 1 h post-injection. The nuclear imaging showed significantly higher uptake in the aorta of the ApoE KO mice than that of the WT mice at least within 2 h post-injection., Conclusion: This study described the pharmacokinetics and biodistribution of (111)In-bis-5HT-DTPA in ApoE KO mice and validated its utilization for early detection of atherosclerotic marker, MPO, in the aortic wall of atherosclerosis-prone rodent model.

Purpose: To develop safe and effective manganese(II) -based biodegradable macromolecular MRI contrast agents., Materials and Methods: In this study, we synthesized and characterized two polydisulfide manganese(II) complexes, Mn-DTPA cystamine copolymers and Mn-EDTA cystamine copolymers, as new biodegradable macromolecular MRI contrast agents. The contrast enhancement of the two manganese-based contrast agents were evaluated in mice bearing MDA-MB-231 human breast carcinoma xenografts, in comparison with MnCl(2) ., Results: The T(1) and T(2) relaxivities were 4.74 and 10.38 mM(-1) s(-1) per manganese at 3T for Mn-DTPA cystamine copolymers (M(n) = 30.50 kDa) and 6.41 and 9.72 mM(-1) s(-1) for Mn-EDTA cystamine copolymers (M(n) = 61.80 kDa). Both polydisulfide Mn(II) complexes showed significant liver, myocardium and tumor enhancement., Conclusion: The manganese-based polydisulfide contrast agents have a potential to be developed as alternative non-gadolinium contrast agents for MR cancer and myocardium imaging., (Copyright © 2011 Wiley-Liss, Inc.)

We report the synthesis of macrocyclic DTPA conjugates of 2,2'-diaminobiphenyl and their Gd complexes of the type [Gd(L)(H(2)O)]·xH(2)O (2a,b; L = 1a,b) for use as new MRI blood-pool contrast agents (MRI BPCAs). Pharmacokinetic inertness of 2 compares well with those of analogous Gd-DTPA MRI CAs currently in use. The present system also shows very high stability in human serum. The R(1) relaxivity reaches 10.9 mM(-1) s(-1), which is approximately 3 times as high as that of structurally related Gd-DOTA (R(1) = 3.7 mM(-1) s(-1)). The R(1) relaxivity in HSA goes up to 37.2 mM(-1) s(-1), which is almost twice as high as that of MS-325, a leading BPCA, demonstrating a strong blood pool effect. The in vivo MR images of mice obtained with 2b are coherent, showing strong signal enhancement in heart, abdominal aorta, and small vessels. Even the brain tumor is vividly enhanced for an extended period of time. The structural uniqueness of 2 is that it is neutral in charge and thus makes no resort to electrostatic interaction, supposedly one of the essential factors for the blood-pool effect.

Radiolabeled peptides have been an important class of compounds in radiopharmaceutical sciences and nuclear medicine for more than 20 years. Despite strong research efforts, only somatostatin-based radiopeptides have a real impact on patient care, diagnostically and therapeutically. [(111)In-diethylenetriaminepentaacetic acid(0)]octreotide is commercially available for imaging. Imaging was highly improved by the introduction of PET radionuclides such as (68)Ga, (64)Cu, and (18)F. Two peptides are successfully used in targeted radionuclide therapy when bound to DOTA and labeled with (90)Y and (177)Lu.

Diethylenetriaminepentaacetic acid (DTPA) is a useful chelating agent for radionuclides such as (68)Ga, (99m)Tc and (111)In, which are applicable to nuclear medicine imaging. In this study, we established a facile synthetic protocol for the production of mono-DTPA-conjugated peptide probes. A novel monoreactive DTPA precursor reagent was synthesized in two steps using the chemistry of the o-nitrobenzenesulfonyl (Ns) protecting group, and under mild conditions this DTPA precursor was incorporated onto an N(ε)-bromoacetylated Lys of a protected peptide resin. The site-specific DTPA conjugation was facilitated by using a highly acid-labile 4-methyltrityl (Mtt) protecting group for the target site of the bioactive peptide during the solid-phase synthesis. A combination of both techniques yielded peptides with disulfide bonds, such as octreotide and polyphemusin II-derived CXCR4 antagonists. DTPA-peptide conjugates were purified in a single step following cleavage from the resin and disulfide bond formation. This site-specific on-resin construction strategy was used for the design and synthesis of a novel In-DTPA-labeled CXCR4 antagonist, which exhibited highly potent inhibitory activity against SDF-1-CXCR4 binding., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

The title complexes were prepared and characterized employing spectral (FAB-Mass, IR, electronic, (1)H and (13)C NMR), thermal and electrochemical techniques. Analytical and FAB-Mass data suggested a homo-dinuclear stoichiometry. IR and electronic ligand field spectral studies coupled with molecular model computations have indicated a distorted octahedral geometry where the ligand coordinates as a hexadentate dianionic [H(3)DTPA](2-)(H(5)DTPA=diethylenetriaminepentaacetic acid) moiety. The electrochemical redox properties and the antibacterial activities of the compounds were also investigated., (Copyright © 2011 Elsevier B.V. All rights reserved.)

N,N'-bis(diethylenetriamine pentaacetic acid)-3,3'-(benzylidene)-bis-(1H-indole-2-carbohydrazide) (bis-DTPA-BI) was radiolabeled with (99m)Tc(CO)(3). The resulting (99m)Tc(CO)(3)-bis-DTPA-BI was characterized (LC-MS) and evaluated as a potential SPECT tracer for imaging of necrosis in Wistar rats with a reperfused partial liver infarction and Wistar rats with ethanol induced muscular necrosis. To study the specificity, uptake of (99m)Tc(CO)(3)-bis-DTPA-BI was also studied in a mouse model of Fas-mediated hepatic apoptosis. The obtained results indicate that (99m)Tc(CO)(3)-bis-DTPA-BI displays selective uptake in necrotic tissue and can be used for in vivo visualization of necrosis by SPECT., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

The use of fluorescent (or luminescent) and metal contrast agents in high-throughput screens, in vitro assays, and molecular imaging procedures has rapidly expanded in recent years. Here we describe the development and utility of high-affinity ligands for cancer theranostics and other in vitro screening -studies. In this context, we also illustrate the syntheses and use of heteromultivalent ligands as targeted imaging agents.

Single-photon emission computed tomography has become a significant imaging modality with huge potential to visualize and provide information of anatomic dysfunctions that are predictive of future diseases. This imaging tool is complimented by radiopharmaceuticals/radiosubstrates that help in imaging specific physiological aspects of the human body. The present study was undertaken to explore the utility of technetium-99m (⁹⁹(m)Tc)-labeled glutamate conjugates for tumor scintigraphy. As part of our efforts to further utilize the application of chelating agents, glutamic acid was conjugated with a multidentate ligand, diethylenetriaminepentaacetic acid (DTPA). The DTPA-glutamate conjugate [DTPA-bis(Glu)] was well characterized by IR, NMR, and mass spectroscopy. The biological activity of glutamic acid was compared with its DTPA conjugate by radiocomplexation with ⁹⁹(m)Tc (labeling efficiency ≥98%). In vivo studies of both the radiolabeled complexes ⁹⁹(m)Tc-Glu and ⁹⁹(m)Tc-DTPA-bis(Glu) were then carried out, followed by gamma scintigraphy in New Zealand albino rabbits. Improved serum stability of ⁹⁹(m)Tc-labeled DTPA conjugate indicated that ⁹⁹(m)Tc remained bound to the conjugate up to 24 hours. Blood clearance showed a relatively slow washout of the DTPA conjugate when compared with the labeled glutamate. Biodistribution characteristics of the conjugate in Balb/c mice revealed that DTPA conjugation of glutamic acid favors less accumulation in the liver and bone and rapid renal clearance. Tumor scintigraphy in mice showed increasing tumor accumulation, stable up to 4 hours. These preliminary studies show that ⁹⁹(m)Tc-DTPA-bis(Glu) can be a useful radiopharmaceutical for diagnostic applications in single-photon emission computed tomography imaging.

Purpose: A novel conjugate, Folate-PEG-CKK(2)-DTPA, was designed and prepared as a carrier for lymphatic metastasized tumor imaging diagnosis and targeting therapy., Methods: Folate-PEG-CKK(2)-DTPA was synthesized and characterized by analysis High Performance Liquid Chromatography, Size Exclusive Chromatography and (1)H-NMR. (99m)Tc-labeled conjugation was prepared, and in vivo quantitative biodistribution and SPECT imaging were studied after subcutaneously injected into the rats and rabbits, respectively. Cell uptake study was carried in a KB cell line using fluorescent methods. In vivo and ex vivo fluorescent imaging study was carried in tumor-bearing nude mouse to evaluate its targeting ability., Results: Folate-PEG-CKK(2)-DTPA was synthesized with high purity. Both in vivo biodistribution study and SPECT imaging study show the rapid direction and high distribution of the conjugation to the lymph nodes. The uptake of fluorescence-labeled Folate-PEG-CKK(2)-DTPA in human oral epidermis carcinoma cells was observed. In vivo and ex vivo fluorescent imaging study indicated it could accumulate in tumor region after vein tail injection in nude mouse., Conclusions: All these findings suggested Folate-PEG-CKK(2)-DTPA as a novel and dependable carrier for tumor diagnosis and therapy, especially for lymph-metastasized tumors.

Methionine-diethylenetriaminepentaaceticacid-methionine [DTPA-bis(Met)] was synthesized by covalently conjugating two molecules of methionine (Met) to DTPA and was labeled with (99m)Tc in high radiochemical purity and specific activity (166-296 MBq/micromol). Kinetic analysis showed K(m) of 12.95 +/- 3.8 nM and a maximal transport rate velocity (V(max)) of 80.35 +/- 0.42 pmol microg protein(-1) min(-1) of (99m)Tc-DTPA-bis(Met) in U-87MG cells. DTPA-bis(Met) had dissociation constants (K(d)) of 0.067 and 0.077 nM in U-87MG and BMG, respectively. (35)S-methionine efflux was trans-stimulated by (99m)Tc-labeled DTPA conjugate demonstrating concentrative transport. The blood kinetic studies showed fast clearance with t(1/2) (F) = 36 +/- 0.5 min and t(1/2) (S) = 5 h 55 min +/- 0.85 min. U-87MG and BMG tumors saturated at approximately 2000 +/- 280 nmol/kg of (99m)Tc-DTPA-bis(Met). Initial rate of transport of (99m)Tc-DTPA-bis(Met) in U-87MG tumor was found to be 4.68 x 10(-4) micromol/kg/min. The tumor (BMG cell line, malignant glioma) grafted in athymic mice were readily identifiable in the gamma images. Semiquantitative analysis from region of interest (ROI) placed over areas counting average counts per pixel with maximum radiotracer uptake on the tumor was found to be 11.05 +/- 3.99 and compared ROI with muscle (0.55 +/- 0.13). The tumor-to-contralateral muscle tissue ratio of (99m)Tc-DTPA-bis(Met) was found to be 23 +/- 3.3. Biodistribution revealed significant tumor uptake and good contrast in the U-87MG, BMG, and EAT tumor-bearing mice. In clinical trials, the sensitivity, specificity, and positive predictive values were found to be 87.8%, 92.8%, and 96.6%, respectively. (99m)Tc-DTPA-bis(Met) showed excellent tumor targeting and has promising utility as a SPECT-radiopharmaceutical for imaging methionine-dependent human tumors and to quantify the ratio of MET(+)/HCY(-).

In this paper, we report a new method to prepare and characterize a contrast agent based on a fourth-generation (G4) polyamidoamine (PAMAM) dendrimer conjugated to the gadolinium complex of the bifunctional diethylenetriamine pentaacetic acid derivative (1B4M-DTPA). The method involves preforming the metal-ligand chelate in alcohol prior to conjugation to the dendrimer. The dendrimer-based agent was purified by a Sephadex G-25 column and characterized by elemental analysis. The analysis and SE-HPLC data gave a chelate to dendrimer ratio of 30:1 suggesting conjugation at approximately every other amine terminal on the dendrimer. Molar relaxivity of the agent measured at pH 7.4 displayed a higher value than that of the analogous G4 dendrimer based agent prepared by the postmetal incorporation method (r(1) = 26.9 vs 13.9 mM(-1) s(-1) at 3 T and 22 degrees C). This is hypothesized to be due to the higher hydrophobicity of this conjugate and the lack of available charged carboxylate groups from noncomplexed free ligands that might coordinate to the metal and thus also reduce water exchange sites. Additionally, the distribution populations of compounds that result from the postmetal incorporation route are eliminated from the current product simplifying characterization as quality control issues pertaining to the production of such agents for clinical use as MR contrast agents. In vivo imaging in mice showed a reasonably fast clearance (t(1/2) = 24 min) suggesting a viable agent for use in clinical application.

N-(2-hydroxypropyl) methacrylamide (HPMA) copolymer-RGDfK conjugates targeting the alpha(v)beta(3) integrin have shown increased accumulation in solid tumors and promise for selective delivery of radiotherapeutics to sites of angiogenesis- or tumor-expressed alpha(v)beta(3) integrin. An unresolved issue in targeting radiotherapeutics to solid tumors is toxicity to non-target organs. To reduce toxicity of radiolabeled conjugates, we have synthesized HPMA copolymer-RGDfK conjugates with varying molecular weight and charge content to help identify a polymeric structure that maximizes tumor accumulation while rapidly clearing from non-targeted organs. Endothelial cell binding studies showed that copolymer conjugates of approximately 43, 20 and 10 kD actively bind to the alpha(v)beta(3) integrin. Scintigraphic images showed rapid clearance of indium-111 ((111)In) radiolabeled conjugates from the blood pool and high kidney accumulation within 1 h in tumor bearing mice. Biodistribution data confirms images with high accumulation in kidney (max 210% ID/g for 43 kD conjugate) and lower tumor accumulation (max 1.8% ID/g for 43 kD conjugate). While actively binding to the alpha(v)beta(3) integrin in vitro, HPMA copolymer-RGDfK conjugates with increased negative charge through increased CHX-A''-DTPA chelator content in the side chains causes increased kidney accumulation with a loss of tumor accumulation in vivo.

A novel bifunctional maleimido CHX-A'' DTPA chelator 5 was developed and conjugated to the monoclonal antibody trastuzumab (Herceptin) and subsequently radiolabeled with (111)In. The resulting (111)In labeled immunoconjugate 2 was demonstrated to bind to SKOV-3 ovarian cancer cells comparably to an isothiocyanato CHX-A'' DTPA modified native trastuzumab, 1. Through efficient thiol-maleimide chemistry, antibodies, peptides or other targeting vectors can now be modified with an established radioactive metal chelating agent CHX-A'' DTPA for imaging and/or therapies of cancer.

Real-time, noninvasive assessment of glomerular filtration rate (GFR) is essential not only for monitoring critically ill patients at the bedside, but also for staging and monitoring patients with chronic kidney disease. In our pursuit to develop exogenous luminescent probes for dynamic optical monitoring of GFR, we have prepared and evaluated Eu(3+) complexes of several diethylenetriamine pentaacetate (DTPA)-monoamide ligands bearing molecular "antennae" to enhance metal fluorescence via intramolecular ligand-metal fluorescence resonance energy transfer process. The results show that Eu-DTPA-monoamide complex 18b, which contains a quinoxanlinyl antenna, exhibits large (ca. 2700-fold) Eu(3+) fluorescence enhancement. Indeed, complex 18b exhibits the highest fluorescent enhancement observed thus far in the DTPA-type metal complexes. The renal clearance property was assessed using the corresponding radioactive (111)In complex 18a, and the data suggest that this complex clears via a complex mechanism that includes glomerular filtration.

To establish a strategy for developing (111)In-diethylenetriaminepentaacetic acid ((111)In-DTPA)-octreotide, a diagnostic radiopharmaceutical agent for tumors, with reduced non-specific renal radio-accumulation, the compounds having D-glutamic acid (Glu) or gamma-carboxy-D-glutamic acid (carboxy-Glu) as the N-terminal amino acid were examined for in vivo radio-distribution. Compounds carrying Glu and carboxy-Glu containing one and two negative charges, respectively, showed lower renal radio-accumulation than that carrying D-phenylalanine. It was revealed that the introduction of a negative charge reduces the renal radio-accumulation independently from the number of negative charges. The present result can be a clue for the development of (111)In-DTPA-octreotides with reduced the renal radio-accumulation.

A novel pyridine-containing DTPA-like ligand, carrying additional hydroxymethyl groups on the pyridine side-arms, was synthesized in 5 steps. The corresponding Gd(III) complex, potentially useful as an MRI contrast agent, was prepared and characterized in detail by relaxometric methods and its structure modeled by computational methods.

Two different fourth-generation (G4) polyaminonamido dendrimer-based magnetic resonsance (MR) agents were prepared by a new synthetic approach wherein tert-butyl-protected forms of 2-(4-isothiocyanatobenzyl)-6-methyldiethylenetriamine pentaacetic acid (1B4M-DTPA), bearing either an isothiocyanate or a succinimidyl ester moiety, respectively, were conjugated to the primary amines of the dendrimer. Purification was facilitated using a solid phase, N-(2-aminoethyl)aminomethyl polystyrene. After Gd(III) incorporation, molar relaxivity measurements of both new dendrimer-based agents as compared to a G4 agent prepared by an aqueous chemistry route indicated no significant changes in relaxivity. Comparative MR imaging revealed equivalent enhancement of the vessels and organs such as the kidney and liver, although slightly different vascular clearance rates were observed. This general synthesis provides a procedure for preparation of dendrimer-based MR agents for clinical applications with higher yields and efficiency while enhancing versatility. The latter aspect is further demonstrated by preparation of a novel maleimide analog of 1B4M-DTPA from a key synthetic intermediate aniline derivative.

A high-molecular weight tetrametallic supramolecular complex [(Ln-DTPA-phen)3Fe]- (Ln = Gd, Eu, La) has been obtained upon self-assembly around one iron(II) ion of three 1,10-phenantroline-based molecules substituted in 5'-position with the polyaminocarboxylate diethylenetriamine-N,N,N',N',N'-pentaacetate, DTPA-phen(4-). The ICP-MS measurements indicated that the lanthanide:iron ratio is 3:1. Photoluminescence spectra of [Eu-DTPA-phen](-) and of [(Eu-DTPA-phen)3Fe]- are nearly identical, implying that the first coordination sphere of the lanthanide(III) ion has not been changed upon coordination of phenantroline unit to iron(II) ion. NMRD measurements revealed that at 20 MHz and 310 K the relaxivity of the [(Gd-DTPA-phen)3Fe]- is equal to 9.5 +/- 0.3 s(-1) mM(-1) of Gd (28.5 s(-1) per millimole per liter of complex) which is significantly higher than that for Gd-DTPA (3.9 s(-1) mM(-1)). The pharmacokinetic parameters of [(Gd-DTPA-phen)3Fe]- in rats indicate that the elimination of [(Gd-DTPA-phen)3Fe]- is significantly slower than that of Gd-DTPA and is correlated with a reduced volume of distribution. The low volume of distribution and the longer elimination time (T(e1/2)) suggest that the agent is confined to the blood compartment, so it could have an important potential as a blood pool contrast agent. The biodistribution profile of [(Gd-DTPA-phen)3Fe]- 2 h after injection indicates significantly higher concentrations of [(Gd-DTPA-phen)3Fe]- as compared with Gd-DTPA in kidney, liver, lungs, heart and spleen. The images obtained on rats by MR angiography show the enhancement of the abdominal blood vessels. The signal intensity reaches a maximum of 55% at 7 min post-contrast and remains around 25% after 90 min. MRI-histomorphological correlation studies of [Gd-DTPA-phen]- and [(Gd-DTPA-phen)3Fe]- showed that both agents displayed potent contrast enhancement in organs including the liver. The necrosis avidity tests indicated that, in contrast to the [Gd-DTPA-phen](-) precursor complex, the supramolecular complex [(Gd-DTPA-phen)3Fe]- exhibits necrosis avidity., (Copyright 2006 John Wiley & Sons, Ltd.)

A neutral bifunctional derivative of diethylenetriaminepentaacetic acid europium(III) (11) was synthesized and its suitability to dissociation-enhanced lanthanide fluorescence immunoassay was investigated.

A novel ligand, diethylenetriamine-N,N''-bis(acetyl-isoniazid)-N,N',N''-triacetic acid (H(3)L) has been synthesized from diethylene triamine pentaacetic acid (DTPA) and isoniazid. Ligand and its five neutral rare earth (RE=La, Sm, Eu, Gd, Tb) complexes holding promise of magnetic resonance imaging (MRI) were characterized on the basis of elemental analysis, molar conductivity, (1)H-NMR spectrum, FAB-MS, TG-DTA analysis and IR spectrum. The relaxivity (R(1)) of complexes and Gd(DTPA)(2-) used as a control were determined. The relaxivity of LaL, SmL, EuL, GdL, TbL and Gd(DTPA)(2-) were 0.14, 1.66, 3.14, 6.08, 2.79 and 4.34 l.mmol(-1).s(-1), respectively. The spin-lattice relaxivity of GdL was larger than that of Gd(DTPA)(2-). The relaxivity of GdL had also been investigated in human serum albumin (HSA) solution, the relaxivity of GdL was enhanced from 6.08 l.mmol(-1).s(-1) in water solution to 9.09 l.mmol(-1).s(-1) in HSA solution. In addition, thermodynamics stability constant of GdL complex was determined, the thermodynamic stability constant of GdL complex (K(GdL)=10(20.84)) was a few larger than that of Gd(DTPA)(2-) (K(Gd-DTPA)=10(20.73)). The results showed that complex of GdL may be a prospective MRI contrast agent with low osmotic pressure due to non-ion complex, high spin-lattice relaxivity, good stability and binding affinity for the serum protein.

A DTPA-based chelate containing one phosphinate group was conjugated to a generation 5 polyamidoamine (PAMAM) dendrimer via a benzylthiourea linkage. The Gd(III) complex of this novel conjugate has potential as a contrast agent for magnetic resonance imaging (MRI). The chelates bind Gd3+via three nitrogen atoms, four carboxylates and one phosphinate oxygen, and one water molecule completes the inner coordination sphere. The monomer Gd(III) chelates bearing nitrobenzyl and aminobenzyl groups ([Gd(DTTAP-bz-NO2)(H2O)]2- and [Gd(DTTAP-bz-NH2)(H2O)]2-) as well as the dendrimeric Gd(III) complex G5-(Gd(DTTAP))63) were studied by multiple-field, variable temperature 17O and 1H NMR. The rate of water exchange is faster than that of [Gd(DTPA)(H2O)]2- and very similar on the two monomeric complexes (8.9 and 8.3 x 10(6) s-1 for [Gd(DTTAP-bz-NO2)(H2O)]2- and [Gd(DTTAP-bz-NH2)(H2O)]2-, respectively), while it is decreased on the dendrimeric conjugate (5.0 x 10(6) s-1). The Gd(III) complex of the dendrimer conjugate has a relaxivity of 26.8 mM-1 s-1 at 37 degrees C and 0.47 T (corresponding to 1H Larmor frequency of 20 MHz). Given the contribution of the second sphere water molecules to the overall relaxivity, this value is slightly higher than those reported for similar size dendrimers. The experimental 17O and 1H NMR data were fitted to the Solomon-Bloembergen-Morgan equations extended with a contribution from second coordination sphere water molecules. The rotational dynamics of the dendrimeric conjugate was described in terms of global and local motions with the Lipari-Szabo approach.

A versatile bifunctional chelating reagent based on a preorganized cyclohexyl derivative of DTPA (CHX-A'') has been developed for the convenient N-terminal labeling of peptides with metal ion radionuclides of Bi(III), In(III), Lu(III), or Y(III). This was achieved via the synthesis of a mono-N-hydroxysuccinimidyl penta-tert-butyl ester derivative of CHX-A'' (trans-cyclohexyldiethylenetriaminepenta-acetic acid) featuring a glutaric acid spacer. Commercially obtained octreotide was modified at its N-terminus by this reagent in the solution phase, and its subsequent radiolabeling with (111)In (T(1/2) = 2.8 d) and (86)Y (T(1/2) = 14.7 h) demonstrated. Small animal PET/CT imaging results of (86)Y-CHX-A''-octreotide in a somatostatin receptor-positive tumor-bearing rat model are presented for the validation of the novel agent.

Purpose: The purpose of this study was to synthesize biodegradable Gd-DTPA L-cystine bisamide copolymers (GCAC) as safe and effective, macromolecular contrast agents for magnetic resonance imaging (MRI) and to evaluate their biodegradability and efficacy in MR blood pool imaging in an animal model., Methods: Three new biodegradable GCAC with different substituents at the cystine bisamide [R = H (GCAC), CH2CH2CH3 (Gd-DTPA L-cystine bispropyl amide copolymers, GCPC), and CH(CH3)2 (Gd-DTPA cystine bisisopropyl copolymers, GCIC)] were prepared by the condensation copolymerization of diethylenetriamine pentaacetic acid (DTPA) dianhydride with cystine bisamide or bisalkyl amides, followed by complexation with gadolinium triacetate. The degradability of the agents was studied in vitro by incubation in 15 microM cysteine and in vivo with Sprague-Dawley rats. The kinetics of in vivo contrast enhancement was investigated in Sprague-Dawley rats on a Siemens Trio 3 T scanner., Results: The apparent molecular weight of the polydisulfide Gd(III) chelates ranged from 22 to 25 kDa. The longitudinal (T1) relaxivities of GCAC, GCPC, and GCIC were 4.37, 5.28, and 5.56 mM(-1) s(-1) at 3 T, respectively. The polymeric ligands and polymeric Gd(III) chelates readily degraded into smaller molecules in incubation with 15 microM cysteine via disulfide-thiol exchange reactions. The in vitro degradation rates of both the polymeric ligands and macromolecular Gd(III) chelates decreased as the steric effect around the disulfide bonds increased. The agents readily degraded in vivo, and the catabolic degradation products were detected in rat urine samples collected after intravenous injection. The agents showed strong contrast enhancement in the blood pool, major organs, and tissues at a dose of 0.1 mmol Gd/kg. The difference of their in vitro degradability did not significantly alter the kinetics of in vivo contrast enhancement of the agents., Conclusion: These novel GCAC are promising contrast agents for cardiovascular and tumor MRI, which are later cleaved into low molecular weight Gd(III) chelates and rapidly cleared from the body.

A very efficient enzymatic method was developed for the synthesis of new enantiomeric benzocispentacin and its six- and seven-membered homologues through the Lipolase (lipase B from Candida antarctica) catalyzed enantioselective (E > 200) ring opening of 3,4-benzo-6-azabicyclo[3.2.0]heptan-7-one, 4,5-benzo-7-azabicyclo[4.2.0]octan-8-one, and 5,6-benzo-8-azabicyclo[5.2.0]nonan-9-one with H2O in iPr2O at 60 degrees C. The (1R,2R)-beta-amino acids (ee > or = 96%, yields > or = 40%) and (1S,6S)-, (1S,7S)-, and (1S,8S)-beta-lactams (ee > 99%, yields > or = 44%) produced could be easily separated. The ring opening of racemic and enantiomeric beta-lactams with 18% HCl afforded the corresponding beta-amino acid hydrochlorides.

Solid-phase synthesis of radiometal chelator-conjugated peptides can facilitate the creation of radioactive peptide libraries to be utilized in high throughput in vivo screening of targeted nuclear-imaging agents. In this study, a new diethylenetriaminepentaacetic acid (DTPA) derivative, 1-(p-succinamidobenzyl)- DTPA penta-t-butyl ester [DTPA(But)(5)-Bz-NH-SA], and its precursor molecule, 1-(p-aminobenzyl)- DTPA penta-t-butyl ester (DTPA(But)(5)-Bz-NH(2)), were applied to the solid-phase synthesis of DTPA-conjugated cyclic peptides containing the Arg-Gly-Asp (RGD) motif with high efficiency. The resulting conjugates, DTPA-Bz-NH-SA-c(Lys-Arg-Gly-Asp-phe) [DTPA-Bz-NH-SA-c(KRGDf)] and DTPA-Bz-NHc( Glu-Arg-Gly-Asp-phe) [DTPA-Bz-NH-c(KRGDf)], demonstrated similar in vitro biologic activities as their corresponding parent peptides. (111)In-labeled, DTPA-conjugated RGD peptides showed selective binding to integrin alphavbeta3 in human melanoma M21 tumors grown in nude mice. Furthermore, (111)In-DTPABz- NH-c(ERGDf) showed lower retention in the liver and the kidney than (111)In-DTPA-Bz-NH-SAc( KRGDf) did, which contributed to higher target to nontarget ratio for (111)In-DTPA-Bz-NH-c(ERGDf). The method reported here can be extended to the construction of peptide libraries containing DTPA for high throughput in vitro and in vivo screening of molecularly targeted imaging agents.

Coupling of ion chromatography with electrospray mass spectrometry (IC-MS) is a simple, sensitive and quick method for the determination of polar organic traces in water samples without derivatization. Analysis of the chelating agents ethylenediamino tetraacetate (EDTA) and diethylenetriamino pentaacetate (DTPA) in aqueous samples was done by IC-MS on an anion exchange column after simple sample preparation steps. Quantification down to a concentration level of 1 microg L(-1) even in wastewater influents and effluents was achieved utilizing 13C marked internal standards and measuring the individual [M - H+]- and stable [M - 4H+ + Fe3+]- cluster ions. The method was validated against certified, but more time consuming routine methods. Applying this method a series of several European water samples were analyzed for EDTA and DTPA indicating their nature as polar persistent pollutants.

A new potential ligand for paramagnetic complexes acting as a receptor-specific MRI contrast agent was investigated by means of one- and two-dimensional NMR spectroscopy and mass spectrometry. A complete assignment of the structure is reported., (Copyright (c) 2005 John Wiley & Sons, Ltd.)

[reaction: see text] The synthesis and some properties of two novel DTPA-bisamides are reported. These derivatives were designed as enzyme-activated contrast agents (CA) for magnetic resonance imaging. Both derivatives bear tyramido or 5-hydroxytryptamido groups that could be oligomerized in situ in the presence of peroxidase/H(2)O(2) pair resulting in a net increase in longitudinal (R1) relaxivity.

We describe the use of two heparin-binding proteins, avidin and lactoferrin, as probes for monitoring the amount of heparin immobilized to plastic surfaces. The proteins were derivatized with either fluorescent labels or europium chelates, enabling sensitive, fast, reproducible, and robust assays, and were used to measure the amount of protein bound to heparinized microplates, with particular attention to plates that have been coated with bovine serum albumin (BSA)-heparin conjugate. This direct method unequivocally shows that BSA-heparin affords an economical, convenient, and reliable method for coating both polystyrene microtiter plates and magnetic beads with heparin. We demonstrate that assays using directly labeled proteins overcome the problems of dissociation of the heparin-protein complex, which can occur during incubation and washing steps associated with antibody-based detection methods, and the loss in binding capacity caused by certain blocking regimes. We suggest that labeled avidin and lactoferrin are convenient probes for heparinized surfaces with the potential for much wider applicability than that presented here.

We wish to report the synthesis and metal complexation properties of new radionuclide chelating agents for use in nuclear medicine. The strategy includes the facile preparation of rigid analogues of DTPA and TTHA possessing an aromatic ring. The aromatic structure used increased the stability of the complexes formed (pre-organization concept) and they are easily functionalised for attaching to any support. The poly(amino)poly(carboxylic) acids, Ph-DTPA (5a) and Ph-TTHA (5b) were obtained in five steps from phenylenediamine as the starting material with overall yields of 42 and 20%, respectively. The key step in this synthetic process is the preparation of tri- and tetra-amino compounds, 3a and 3b, respectively. In order to assess the ability of both ligands to complex with different metals ((111)In, (153)Sm, (90)Y, (177)Lu, (213)Bi, (225)Ac), along with their suitability for use in nuclear medicine, we used a number of complementary tests. We were able to demonstrate the high complexation capacity of Ph-DTPA (5a) with a broad range of radionuclides in a slightly acidic medium. In vitro stability studies show the high stability of Ph-DTPA with (111)In in human serum, a necessary condition for all medical applications. The protonation constant (log K(H)(i)) of Ph-DTPA (5a) was determined by potentiometric methods.

Unlabelled: Radiolabeling of monoclonal antibodies (mAbs) with an intracellularly trapped form of (131)I (residualizing (131)I) involves radioiodinating a small molecular entity, conjugating it to the mAb, and purification. Column purifications are impractical during procedures involving multi-gigabecquerel levels of radioactivity. The goal of this study was to develop a simple, remote, "1-pot" method of radiolabeling and purification for the scaled-up radioiodination of a humanized anti-carcinoembryonic antigen (CEA) mAb, humanized MN-14 (hMN-14; labetuzumab), with an optimized residualizing (131)I moiety, (131)I-IMP-R4. IMP-R4 is MCC-Lys(MCC)-Lys(X)-d-Tyr-d-Lys(X)-OH, where MCC is 4-(N-maleimidomethyl)-cyclohexane-1-carbonyl and X is 1-((4-thiocarbonylamino)benzyl)-diethylenetriaminepentaacetic acid., Methods: An IODO-GEN-based remote labeling system was used. IMP-R4 was radioiodinated (0.13 mumol per 3.7 GBq of (131)I) at a pH of 7.0-7.4 and conjugated to disulfide-reduced hMN-14 after quenching of unused reactive (131)I. The product was purified by stirring for 5 min with a 20% (w/v) suspension of an anion-exchange resin and sterilely filtered into a sealed vial. Human serum albumin was added at a final concentration of 1%-2.5%. Immunoreactivity was determined by mixing with CEA and determining the complexation level by size-exclusion high-pressure liquid chromatography. Two control radiolabelings, either with unreduced hMN-14 or with IMP-R4 omitted, also were performed., Results: In 18 radiolabelings with (131)I in the range of 2.04-4.81 GBq (55-130 mCi), yields of 59.9% +/- 7.9% (mean +/- SD) at specific activities of 200 +/- 26 MBq/mg (5.4 +/- 0.7 mCi/mg) were obtained, with > or =95% of the radioactivity being associated with hMN-14 and with < or =4% aggregation. Similar yields were obtained in a subset of radiolabelings (n = 7) with >3.7 GBq of (131)I. The immunoreactivities of the preparations were typically >95%. Nonspecific incorporation in the absence of IMP-R4 was 0.5%, whereas that obtained with unreduced IgG was approximately 8%, possibly because of conjugation of IMP-R4 at lysine sites. The process also removed >99% of the quenching reagent used. Radiolabelings performed with freshly prepared solutions or lyophilized preparations produced similar yields, a result that suggested the option for a single-use kit design., Conclusion: Efficient removal of (131)I-IMP-R4 and quenched (131)I by 5 min of stirring with anion-exchange resin renders a multi-gigabecquerel-level preparation of (131)I-IMP-R4-hMN-14 safe, convenient, and practical.

A new magnetic resonance imaging (MRI) contrast agent designed to mimic sialyl Lewis X (sLeX) and to target inflammation has been synthesized and characterized. The evolution of its proton longitudinal relaxivity as a function of the magnetic field (NMRD) and temperature has been studied. The exchange rate of the water coordinated to the metal has been assessed by oxygen-17 relaxometry. The transmetalation by zinc(II) ions and the noncovalent binding to human serum albumin have been evaluated. The results show no limitation by the residence time of the coordinated water molecule above room temperature, a higher stability of the complex versus transmetalation by zinc(II) ions than a parent complex, the clinically used Gd-DTPA-BMA, and negligible interaction with human serum albumin.

We have developed an automated system for the preparation of highly concentrated 188Re-perrhenate, diethylenetriamine pentaacetic acid (DTPA) and mercaptoacetyltriglycine (MAG3). The three procedural steps include concentration of 188Re-perrhanerate, chelation and purification and sterilization. The steps are operated by a small micro-controller. The eluted 188Re-perrhenate of 15 GBq/18 ml from 37 GBq 188W/188Re-generator was concentrated to 1.2 ml in 10 +/- 0.5 min with a recovery yield of 95 +/- 1.5%. We obtained the highest radiochemical yield of 95.4 +/- 2.8% and 98.5 +/- 1.2% for 188Re-DTPA and MAG3 at the oil bath temperatures of 95-97 degrees C and 93-97 degrees C, respectively.

Luminescent lanthanide complexes have unusual spectroscopic characteristics, including millisecond excited-state lifetime and sharply spiked emission spectra. These characteristics make them valuable alternatives to conventional organic fluorescent probes in detection applications and for measuring nanometer-scale conformational changes in biomolecules via resonance energy transfer. Our group has previously reported the syntheses and application of various luminescence complexes that have polyaminocarboxylate chelates coupled to a carbostyril antenna and thiol or amine-reactive groups. Here we report the syntheses of new thiol-reactive forms of DTPA-cs124 chelates, including two iodoacetamide forms (phenylalanine-iodoacetamide and ethylenediamine iodoacetamide) and two methane-thio-sulfonate forms (ethylmethanethiosulfonate and carboxyethylmethanethiosulfonate). In addition, we have developed an improved synthesis of a previously reported maleimide form.

The prevalence of neurotensin receptor (NTR) in several human tumors makes it an attractive target for the delivery of cytotoxic drugs and imaging agents. Native neurotensin (NT) is a tridecapeptide that binds to NTR and induces tumor growth. Unfortunately, NT has a short plasma half-life, which hinders its use for in vivo biomedical applications. Numerous reports suggest that Arg(8)-Arg(9) and Tyr(11)-Ile(12) amide bonds are particularly susceptible to degradation by proteolytic enzymes. Predicated on this observation, we substituted Arg(8), Arg(9), and Ile(12) amino acids with the corresponding commercially available mimics. These surrogate amino acids are amenable to standard Fmoc peptide synthesis strategy, and the resulting compounds are stable in biological media for >4 h and bind to NTR with high affinity. Furthermore, conjugating DTPA to the new peptides and subsequent labeling with (111)In-DTPA for nuclear imaging or fluorescein for optical imaging did not diminish the NTR binding affinities of the peptides. In vivo biodistribution of a representative (111)In-DTPA-NT peptide analogue in SCID mice bearing NTR-positive human adenocarcinoma (HT29) xenograft shows that the compound was primarily retained in tumor tissue (2.2% ID/g) and the kidneys (4.8% ID/g) at 4 h postinjection. Coinjection of cold NT and the radiolabeled NT peptide analogue inhibited the tumor but not the kidney uptake, demonstrating that retention of the radiolabeled compound in tumor tissue was mediated by NTR specific uptake while it accumulates in the kidneys by a nonspecific mechanism. These findings show that the new NT peptide analogues are robust and can deliver imaging agents to NTR-positive tumors such as pancreatic cancer.

This paper reports a new method for preconcentration and separation of trace amounts of molybdenum in seawater samples prior to determination by inductively coupled plasma-atomic emission spectroscopy (ICP-OES). Diethylenetriaminetetraacetic acid-functionalized polysiloxane (DETAP) was synthesized by carboxymethylation of amino groups on triamine immobilized polymer, which was prepared by modification of 3-chloropropylpolysiloxane with diethylenetriamine. The resulting polysiloxane is highly selective and efficient in chelating Mo(VI) at trace levels. It can be used as a column packing material. The polysiloxane column can be reused over ten times without losing its original properties, so it is suitable for preconcentration of molybdenum species in seawater samples before determination. The parameters governing the characteristics of polysiloxane for adsorption of Mo(VI) were investigated. These include the effect of pH, amount of polysiloxane, equilibrium time, adsorption isotherm, maximum adsorption capacity, interfering ions, flow rate, capacity for reuse, and desorption. The precision of the preconcentration method, calculated as the relative standard deviation of seawater samples, was 3%. The preconcentration factor was 100. The detection limit, defined as 3 times the standard deviation of five replicate measurements of the blank sample at pH 3, was 0.17 microg L(-1). Measurement results for standard reference materials were in good agreement with the certified values [(CRMs), NASS-2 Seawater (Open Ocean) and CASS-2 Seawater (Coastal)].

The preparation of two Ru(III) polyaminocarboxylate complexes, AMD6245 and AMD6221, and their nitrosyl analogues, AMD6204, AMD6263, and AMD3689, is described. The compounds are characterized by IR, ES-MS, and (13)C and (15)N NMR spectroscopy where appropriate and cyclic voltammetry. The crystal structures for AMD6245, AMD6263, and AMD3689 are presented. AMD6245 (C(10)H(14)N(2)O(9)Ru) crystallized in the P2(1)/c space group with a = 8.4382(2) A, b = 8.8304(2) A, c = 17.6321(4) A, beta = 99.603(o), V = 1295.3(2) A(3), and Z = 4. AMD6263 (C(10)H(14)N(3)O(10)Ru) crystallized in the P2(1)/c space group with a = 9.9043(4) A, b = 13.1144(3) A, c = 12.0914(4) A, beta = 100.191(o), V = 1545.8(5) A(3), and Z = 4. AMD3689 (C(14)H(24.56)N(4)O(13.28)Ru) crystallized in the P1 space group with a = 8.838(2) A, b = 9.452(3) A, c = 13.419(4) A, alpha = 78.413(6)(o), beta = 75.804(6)(o), gamma = 73.562(6)(o), V = 1031.8(5) A(3), and Z = 2. The reaction of AMD6245 and AMD6221 with nitric oxide is investigated using EPR spectroscopy and stopped flow kinetics. Upon reaction with NO, a linear, diamagnetic [RuNO](6) complex is formed. The substitution reaction of AMD6245 with NO proceeds with a second-order rate constant of 2.24 x 10(7) M(-1) s(-1) at 7.3 degrees C (pH = 7.4; 50 mM phosphate buffer). The substitution reaction of AMD6221 with NO proceeds with a second-order rate constant of 3 x 10(5) M(-1) s(-1) at 20 degrees C (pH = 7.4; 50 mM phosphate buffered saline). The NO scavenging ability was assessed using a RAW264 murine macrophage assay by measuring the difference in nitrite produced between untreated control cells and treated cells. At 100 microM AMD6245 has [NO(2-)] = 12.5 microM less than the untreated cells and AMD6221 has [NO(2-)] = 37.6 microM less than the untreated cells. There is an insignificant difference in the amount of nitrite produced between AMD6263 or AMD3689 treated cells and untreated cells.

Liquid radiation sources with beta emitters have advantages of accurate positioning and uniform dose distribution to the vessel walls to prevent the restenosis of coronary artery. As a liquid radiation source, 166Ho-DTPA was prepared and evaluated its in-vivo pharmacokinetic behavior through animal studies.166Ho-DTPA was prepared by simple mixing the Holmium with DTPA at room temperature. The radiolabelling yield was 100% when the DTPA/Holmium molar ratio was >2. Radiolabelling of 166Ho-DTPA was not dependent on the pH range of 1.7-7.5. High radiochemical stability (>98%) was maintained over a period of 6 hours even with a radioactivity ( approximately 11.1 GBq/12 mg of DTPA) stored at room temperature. Biodistribution of 166Ho-DTPA in rats and gamma camera images in rabbits showed that 166Ho-DTPA was quickly excreted via the urinary system. The average of T(max) and T(1/2) of 166Ho-DTPA in the kidneys of rabbits were 3.71 +/- 1.18 min and 9.15 +/- 3.15 min. 166Ho-DTPA is a potential liquid radiation source for radiation brachytherapy to prevent the restenosis of the coronary artery using a liquid-filled balloon.

Rationale and Objectives: A molecular-based computed tomographic (CT) contrast agent with prolonged vascular residence time is needed for vascular and tumor imaging. No particulate agents have reached clinical practice due to nonspecific macrophage activation. The authors' objective was to synthesize a water-soluble macromolecular agent., Materials and Methods: Dysprosium-DTPA-dextran was synthesized through activation of the hydroxyl units of dextran PM40 with allylbromine and subsequent reaction with amino ethanethiol to produce amino-terminated leashes. These leashes were then coupled to DTPA by means of the mixed anhydride method. Complexation of dysprosium by DTPA-dextran was achieved in an acidic solution of 0.2 M dysprosium chloride. One rabbit with a VX2 tumor was imaged with [Dy]DTPA-dextran (0.5 mL, 3.1 g, 1.15 mmol of dysprosium per kilogram). Transaxial scans were acquired through the liver and tumor for 45 minutes. A second healthy rabbit was imaged with Optiray-320 (6.0 mL, 5.0 mmol of iodine per kilogram) at 1-minute intervals for 10 minutes and again at 20 minutes., Results: Each dextran PM40 molecule (diameter, 8.8 nm) contained 95 [Dy]DTPA groups, increasing its average molecular weight from 40,500 to 101,537 g/mol. The baseline-corrected inferior vena cava (IVC) enhancement for [Dy]DTPA-dextran decreased, with an 8-minute half-time during the first 15 minutes followed by a nearly zero slope for the rest of the observation period. The IVC remained brighter than liver throughout the observation period. The solid portion of the tumor was enhanced by 5-10 CT numbers, rendering areas of necrosis more apparent. The baseline-corrected IVC curve for Optiray-320 also demonstrated two phases, with half-times of 2.5 and 45 minutes. The IVC became less dense than liver within 5-8 minutes., Conclusion: [Dy]DTPA-dextran is water soluble and can be synthesized without intermolecular cross-linking to carry a high load of dysprosium. It provides blood pool enhancement characteristics with a long intravascular dwell time.