Synthesis and evaluation of 111In-labeled d-glucose as a potential SPECT imaging agent

The purpose of this study was to develop an efficient synthetic method for labeling d-Glucosamine with indium-111 (¹¹¹In), and to investigate the imaging properties of the resulting radiotracer in MDA-MB-468 xenograft models using single-photon emission computed tomography (SPECT). The precursor compound, 2-(4-Isothiocyanato benzyl)-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid-deoxyglucosone (DOTA-DG), was synthesized from 2-d-Glucosamine. DOTA-DG was labeled with ¹¹¹In within 20 min. The labeling efficiency and radiochemical purity of ¹¹¹In-DOTA-DG were >95 and >96 % as determined by radio-HPLC. SPECT imaging studies were performed using nude mice bearing MDA-MB-468 mammary tumors after intravenous injection of at a dose of 1.11 MBq (0.1 mL) ¹¹¹In-DOTA-DG. Tumors were clearly delineated by SPECT imaging at 120 min after injection.     

Reoxidation of uranium in electrolytically reduced simulated oxide fuel during residual salt distillation

Apoptosis is one of the fundamental phenomena behind successful radiation and chemotherapy treatments. Non-invasive imaging of apoptosis can offer an early diagnosis of disease and the true efficiency of an ongoing treatment procedure. The present study describes an attempt to develop ^99mTc-labeled 2-methyl-2-pentylmalonic acid ([^99mTc] 8) as a new SPECT based apoptosis imaging agent. An optimized chemical and radiosynthesis procedure provided desired product [^99mTc] 8 with high radiochemical yield (84%, n = 3) and radiochemical purity (>99%) as determined by radio HPLC. Biodistribution data indicated that the radiotracer has a rapid clearance from blood and other background tissues. High testes accumulation confirmed the ability of the radiotracer to detect testicular apoptosis in mice.

     

Preliminary Study of a 1,5-Benzodiazepine-Derivative Labelled with Indium-111 for CCK-2 Receptor Targeting

The cholecystokinin-2 receptor (CCK-2R) is overexpressed in several human cancers but displays limited expression in normal tissues. For this reason, it is a suitable target for developing specific radiotracers. In this study, a nastorazepide-based ligand functionalized with a 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) chelator (IP-001) was synthesized and labelled with indium-111. The radiolabeling process yielded >95% with a molar activity of 10 MBq/nmol and a radiochemical purity of >98%. Stability studies have shown a remarkable resistance to degradation (>93%) within 120 h of incubation in human blood. The in vitro uptake of [¹¹¹In]In-IP-001 was assessed for up to 24 h on a high CCK-2R-expressing tumor cell line (A549) showing maximal accumulation after 4 h of incubation. Biodistribution and single photon emission tomography (SPECT)/CT imaging were evaluated on BALB/c nude mice bearing A549 xenograft tumors. Implanted tumors could be clearly visualized after only 4 h post injection (2.36 ± 0.26% ID/cc), although a high amount of radiotracer was also found in the liver, kidneys, and spleen (8.25 ± 2.21%, 6.99 ± 0.97%, and 3.88 ± 0.36% ID/cc, respectively). Clearance was slow by both hepatobiliary and renal excretion. Tumor retention persisted for up to 24 h, with the tumor to organs ratio increasing over-time and ending with a tumor uptake (1.52 ± 0.71% ID/cc) comparable to liver and kidneys.     

Preparation and Evaluation of Novel Folate Isonitrile 99mTc Complexes as Potential Tumor Imaging Agents to Target Folate Receptors

In order to seek novel technetium-99m folate receptor-targeting agents, two folate derivatives (CN5FA and CNPFA) were synthesized and radiolabeled to obtain [^99mTc]Tc-CN5FA and [^99mTc]Tc-CNPFA complexes, which exhibited high radiochemical purity (>95%) without purification, hydrophilicity, and good stability in vitro. The KB cell competitive binding experiments indicated that [^99mTc]Tc-CN5FA and [^99mTc]Tc-CNPFA had specificity to folate receptor. Biodistribution studies in KB tumor-bearing mice illustrated that [^99mTc]Tc-CN5FA and [^99mTc]Tc-CNPFA had specific tumor uptake. Compared with [^99mTc]Tc-CN5FA, the tumor/muscle ratios of [^99mTc]Tc-CNPFA were higher, resulting in a better SPECT/CT imaging background. According to the results, the two ^99mTc complexes have potential as tumor imaging agents to target folate receptors.     

Preparation and preliminary evaluation of [<Superscript>67</Superscript>Ga]-tetra phenyl porphyrin complexes as possible imaging agents

[⁶⁷Ga]labeled tetraphenyl porphyrin ([⁶⁷Ga]-TPP) was prepared using freshly prepared [⁶⁷Ga]GaCl₃ and tetraphenyl porphyrin (TPPH₂) for 30–60 min at 25 °C (radiochemical purity: >97 ± 1% ITLC, >98 ± 0.5% HPLC, specific activity: 13–14 GBq/mmol). Stability of the complex was checked in final formulation and human serum for 24 h. The partition coefficient was calculated for the compound (log P 1.89). The biodistribution of the labeled compound in vital organs of wild-type rats was studied using scarification studies and SPECT imaging up to 24 h. A detailed comparative pharmacokinetic study performed for ⁶⁷Ga cation and [⁶⁷Ga]-TPP. The complex is mostly washed out from the circulation through kidneys and can be an interesting tumor imaging/targeting agent due to low liver uptake and rapid excretion through the urinary tract.     

Design and preliminary assessment of 99mTc-labeled ultrasmall superparamagnetic iron oxide-conjugated bevacizumab for single photon emission computed tomography/magnetic resonance imaging of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) has a very high incidence and mortality. Early diagnosis and timely treatments are therefore required to improve the quality of life and survival rate of HCC patients. Here, we developed a vascular endothelial growth factor (VEGF)-based multimodality imaging agent for single photon emission computed tomography (SPECT), computed tomography (CT) and magnetic resonance imaging (MRI) and used it to assess HCC mice and explore the combinative value of CT/MRI-based morphological imaging and SPECT functional imaging. HCC targeting with ¹²⁵I-labeled bevacizumab monoclonal antibody (mAb) was examined using SPECT/CT in HepG2 tumor-bearing mice after intravenous mAb injection. Based on this, an integrated, bimodal, VEGF-targeted, ultrasmall superparamagnetic iron oxide (USPIO)-conjugated ^99mTc-labeled bevacizumab mAb was synthesized to increase tumor penetration and accumulations. The in vivo pharmacokinetics and HepG2 tumor targeting were explored through in vivo planar imaging and SPECT/CT using a mouse model of HepG2 liver cancer. The specificity of the radiolabeled nanoparticles for HepG2 HCC was verified using in vitro immunohistochemistry and Prussian blue staining. With diethylenetriamine pentaacetic acid as a bifunctional chelating agent, USPIO-bevacizumab achieved a ^99mTc labeling efficiency of >90 %. The in vivo imaging results also exhibited the targeting of USPIO on HepG2 HCC. The specificity of these results was confirmed using in vitro immunohistochemistry and Prussian blue staining. Our preliminary findings showed the potential of USPIO as an imaging agent for the SPECT/MRI of HepG2 HCC.     

Design,Synthesis and Preclinical Assessment of 99mTc-iFAP for In Vivo Fibroblast Activation Protein (FAP) Imaging

Fibroblast activation protein (FAP) is expressed in the microenvironment of most human epithelial tumors. ⁶⁸Ga-labeled FAP inhibitors based on the cyanopyrrolidine structure (FAPI) are currently used for the detection of the tumor microenvironment by PET imaging. This research aimed to design, synthesize and preclinically evaluate a new FAP inhibitor radiopharmaceutical based on the ^99mTc-((R)-1-((6-hydrazinylnicotinoyl)-D-alanyl) pyrrolidin-2-yl) boronic acid (^99mTc-iFAP) structure for SPECT imaging. Molecular docking for affinity calculations was performed using the AutoDock software. The chemical synthesis was based on a series of coupling reactions of 6-hidrazinylnicotinic acid (HYNIC) and D-alanine to a boronic acid derivative. The iFAP was prepared as a lyophilized formulation based on EDDA/SnCl₂ for labeling with ^99mTc. The radiochemical purity (R.P.) was verified via ITLC-SG and reversed-phase radio-HPLC. The stability in human serum was evaluated by size-exclusion HPLC. In vitro cell uptake was assessed using N30 stromal endometrial cells (FAP positive) and human fibroblasts (FAP negative). Biodistribution and tumor uptake were determined in Hep-G2 tumor-bearing nude mice, from which images were acquired using a micro-SPECT/CT. The iFAP ligand (Ki = 0.536 nm, AutoDock affinity), characterized by UV-Vis, FT-IR, ¹H–NMR and UPLC-mass spectroscopies, was synthesized with a chemical purity of 92%. The ^99mTc-iFAP was obtained with a R.P. >98%. In vitro and in vivo studies indicated high radiotracer stability in human serum (>95% at 24 h), specific recognition for FAP, high tumor uptake (7.05 ± 1.13% ID/g at 30 min) and fast kidney elimination. The results found in this research justify additional dosimetric and clinical studies to establish the sensitivity and specificity of the ^99mTc-iFAP.     

Diagnostic value of female genital malignant tumors by using 111In-bleomycin scintigraphy.

In order to know if it is possible to objectively decide the extent of infiltration of female genital malignant tumors into parametrium by using 111In-bleomycin scintigraphy, a fundamental and clinical investigation was made. The result was as follows; 1) The radiochemical purity and stability of 111In-BLM were comparatively unchangeable. When this complex was kept at room temperature for a week, there was not more than 2% of the free 111In. 2) As to blood clearance, when the blood radioactivity of 111In-BLM 5 minutes after the injection was counted as 100%, about 80% of the radioactivity was cleared from the blood in 48 hours. Over 50% of the radioactivity was excreted into the urine in 48 hours. 3) Of 29 cases of female genital malignant tumors, 23 cases (79%) showed positive images. Therefore 111In-BLM was found to be one of the suitable radiopharmaceuticals for the diagnosis of female genital malignant tumors. 4) 111In-BLM scintigraphy was of great use for deciding the extent of the invasion of carcinoma cervicis uteri into parametrium and for the search of metastasis.     

Evaluation and comparison of 99mTc-labeled d-glucosamine derivatives with different 99mTc cores as potential tumor imaging agents

Isocyanide is a strong coordination ligand that can coordinate with [^99mTc(I)(CO)₃]⁺ core and [^99mTc(I)]⁺ core to produce stable ^99mTc complexes, therefore developing a ^99mTc-labeled isocyanide complex for single-photon emission computed tomography (SPECT) imaging is considered to be of great interest. In order to develop potential tumor imaging agents with satisfied tumor uptake and suitable pharmacokinetic properties in vivo, a novel d -glucosamine isocyanide derivative, 4-isocyano-N-(2,4,5-trihydroxy-6-(hydroxymethyl)tetrahydro-2H-pyran-3-yl)butanamide (CN3DG), was synthesized and radiolabeled with [^99mTc(I)]⁺ and [^99mTc(CO)₃]⁺ cores to obtain [^99mTc(CN3DG)₆]⁺ and [^99mTc(CO)₃(CN3DG)₃]⁺ in high radiolabeling yields (>95%). Both of the complexes showed good hydrophilicity and great stability in vitro. Cell uptake studies performed in S180 cells demonstrated they were transported into cells by glucose transporters. Biodistribution studies of the two complexes in mice bearing S180 tumor showed they had high tumor uptakes and rapid clearance from muscle and blood so that the tumor/blood and tumor/muscle ratios were high. By comparison, [^99mTc(CN3DG)₆]⁺ was superior to [^99mTc(CO)₃(CN3DG)₃]⁺ in regard to tumor uptake, tumor/blood and tumor/liver ratios. S180 tumors could be seen clearly from the SPECT/CT images with [^99mTc(CN3DG)₆]⁺. Considering its favorable properties, [^99mTc(CN3DG)₆]⁺ would be a promising tumor imaging agent and needs to be further studied.     

Development and evaluation of a 166holmium labelled porphyrin complex as a possible therapeutic agent

Porphyrins are interesting derivatives with low toxicity, tumor avidity and rapid wash-out suggested as potential radiopharmaceuticals in radiolabeled form. In this work, [¹⁶⁶Ho] labeled 5,10,15,20-tetrakis(phenyl) porphyrin ([¹⁶⁶Ho]-TPP) was prepared using [¹⁶⁶Ho]HoCl₃ and 5,10,15,20-tetrakis(phenyl)porphyrin (H₂TPP) for 12 h at 50 °C (radiochemical purity: >95 ± 2 % ITLC, >99 ± 0.5 % HPLC, specific activity: 0.9–1.1 GBq/mmol). Stability of the complex was checked in final formulation and human serum for 48 h. The partition coefficient was calculated for the compound (log P = 2.01). The biodistribution of the labeled compound in vital organs of wild-type rats was studied using scarification studies and SPECT. A detailed comparative pharmacokinetic study performed for ¹⁶⁶Ho cation and [¹⁶⁶Ho]-TPP performed up to 24 h. The complex is mostly washed out from the circulation through kidneys and in less extends from the liver. The kidney:blood, kidney:liver and kidney:muscle ratios 4 h post injection were 14, 3.6 and 7.38 respectively.     

Preparation and SPECT imaging of the novel Anxa 1-targeted probe 99mTc-p-SCN-Bn-DTPA-GGGRDN-IF7

Annexin 1 (Anxa1) is a highly specific surface marker of tumor vasculature in several solid tumors. The IF7 peptide was modified with a hydrophic linkers,GGGRDN, and introduced into a new bifunctional chelating agent p-SCN-Bn-DTPA. The resulting peptides (p-SCN-Bn-DTPA-GGGRDN-IF7) was successfuly labeled with ^99mTc. The targeting characteristics to Anxa1 of the radiolabeled peptide were evaluated by in vitro and in vivo study is on U87 tumor models. SPECT imaging revealed that the U87 tumors were clearly visualized (3.64 ± 0.44%ID/g at 2 h p.i.). ^99mTc-p-SCN-Bn-DTPA-GGGRDN-IF7 (Tc-RIF7) might be a potential target probe for detecting Anxa1 levels in cancers due to the favorable characterizations such as convenient synthesis, specific Anxa1 targeting and moderate tumor uptakes.

     

Chemical and biological properties of verapamil labeled with technetium-99m: A potential myocardial imaging agents

On the base of property to enter into myocardial cells as a calcium channel blocker, verapamil was labeled with technetium-99m in order to investigate the possibility to obtain new radiopharmaceutical for myocardial imaging. The conditions of labeling verapamil with technetium-99m for different ammounts of stannous(II) ion, mannitol, cystein and pH range 2.5–3.5 were examined. Investigation of radiochemical purity (>95%) and biodistribution of ^99mTc-verapamil in rats showed that it was stable during 2 hours after labeling. Accumulation of ^99mTc-verapamil in heart was 1.2% and in liver 9.4%, 5 minutes after injection. Biodistribution of ^99mTc-verapamil in rats in conditions of stress, pharmacologically caused by dipiridamol, showed that the elimination of ^99mTc-verapamil from the heart was slower related to the control group. In the group of rats previously treated with isoproterenol uptake of ^99mTc-verapamil in heart was lower related to the control group (0.7% versus 1.0%) 5 minutes after injection. Lipophilicity of ^99mTc-verapamil was examined by determination of partition coefficient (log P = 0.62) and protein binding (79%). Imaging studies on dogs provided relatively good myocardial images with partially overlap of activity in the lung and liver.     

A novel peptide-based probe 99mTc-PEG6-RD-PDP2 for the molecular imaging of tumor PD-L2 expression

Tumor-related PD-L2 expression is associated with the clinical efficacy of PD-1/PD-L1 blockade therapy. PD-L2-specific imaging can help selecting patients for appropriate immunotherapy. In this study, a PD-L2-targeting peptide (PDP2) was screened by the one-bead one-compound combinatorial library approach. Using the retro-inverso d-peptide of PDP2 (RD-PDP2) and PEGylation strategies, we developed a novel Tc-99m-labeled PD-L2-targeting peptide as a SPECT tracer (^99mTc-PEG₆-RD-PDP2) for imaging of tumor PD-L2 expression. The radiolabeling yield of ^99mTc-PEG₆-RD-PDP2 was greater than 95% by the standard HYNIC/tricine/TPPTS labeling procedure. ^99mTc-PEG₆-RD-PDP2 displayed high PD-L2-binding specificity both in vitro and in vivo. SPECT/CT imaging with ^99mTc-PEG₆-RD-PDP2 showed that the A549-PD-L2 tumors were clearly visualized, whereas the signals in PD-L2-negative A549 tumors were much lower. In vivo blocking study suggested that the tumor uptake of ^99mTc-PEG₆-RD-PDP2 was PD-L2 specifically mediated. ^99mTc-PEG₆-RD-PDP2 is a promising SPECT probe for the non-invasive imaging of tumor PD-L2 expression and has a great potential in guiding the anti-PD-1 or anti-PD-L1 immunotherapy of cancer.     

Synthesis and biological evaluation of <Superscript>99m</Superscript>Tc-DHPM complex: a potential new radiopharmaceutical for lung imaging studies

In the recent years interests on dihydropyrimidinone and their analogues have increased potentially due to their wide range of pharmacological/biological activities. Synthesis, radiolabeling with technetium-99 m (^99mTc) and biological evaluation of 5-etoxycarbonyl-4-phenyl-6-methyl-3,4-dihydro-(1H)-pyrimidine-2-one (DHPM) were studied in this present work. After synthesis complexation of DHPM with ^99mTc was carried out using stannous chloride as the reducing agent. The complex (^99mTc-DHPM) was characterized by thin layer chromatography, radio-HPLC technique and determination of partition co-efficient. Radiochemical stability and particle size distribution of the complex were also measured. Biodistribution/scintigraphy studies were performed in rats and rabbits to evaluate the pharmacological characteristics of this complex. The radiochemical purity of the complex was over 95% as studied by thin layer chromatography and radio-HPLC. It was stable over 24 h at room temperature. Its partition coefficient indicated that it was a lipophilic complex. According to the European Pharmacopeia, >80% of ^99mTc labeled radiopharmaceutical (^99mTc-MAA) in the size range 10–50 μm, must be accumulated in the lungs 15 min after intravenous administration. In this study >85% of the ^99mTc-DHPM complex in the average size of 40 μm. Biodistribution studies of ^99mTc-DHPM in rat revealed that the complex accumulated in the lung with high uptake and good retention after intravenous administration. Scintigraphic studies in rabbit also revealed that most of the administered radiolabeled complex was accumulated in the lungs and after 1 h slowly excreted through the renal system. The lung uptake (ID%/g) was 10.12, 9.67, 8.60 and 5.01 and the lung/liver ratio was 7.49, 2.88, 2.62 and 1.87 at 2, 15, 30 and 60 min post-injection, respectively. These results suggested that ^99mTc-DHPM could be suitable as a potential lung perfusion imaging agent. Further studies with ^99mTc-DHPM and its derivatives are warranted to develop new ^99mTc-labeled imaging agents for clinical applications.     

Synthesis and preliminary evaluation of 99mTc-spermine as a tumor imaging agent

Polyamines are essential for the growth and survival of all cells with biosynthesis and transportation of polyamines being very active in tumors. With the aim of developing a new tumor imaging agent, the endogenous polyamine, spermine was labeled with ^99mTc, and its characters were also evaluated via in vitro and in vivo studies. ^99mTc-labeled spermine probe (^99mTc-spermine) was synthesized by the direct pretinning procedure and the labeling procedure was optimized with regard to the pH, reaction time, amounts of spermine and SnCl₂. The stability of the ^99mTc-spermine and its capacity to accumulate into 4T1 tumor cells were also evaluated. Biodistribution of ^99mTc-spermine was studied in 4T1 tumor-bearing mice. In the optimal conditions, the whole radiosynthesis was accomplished within 10 min with a decay-corrected yield of 96.5 ± 1.3 % and radiochemical purity of >95 %.^99mTc-spermine was stable at both 37 and 4 °C for at least 6 h. In vitro tests revealed that the ability of ^99mTc-spermine to penetrate in 4T1 tumour cells and an excess of spermine blocked the accumulation of the compound in the models. Biodistribution studies showed a high tumor uptake peaked at 30 min post-injection with 1.82 ± 0.19 % ID%/g. The tumor to muscle uptake ratios of the probe were 3.60 ± 0.51, 4.48 ± 0.29, 4.82 ± 0.18, 5.64 ± 0.10, respectively at 30 min, 1, 2 and 4 h postinjection. Block studies indicated that ^99mTc-spermine had specific binding of tumor via polyamine transport systems. ^99mTc-spermine is a promising radiopharmaceutical in tumor imaging. Further studies are required to determine the usability of ^99mTc–spermine for diagnosis purposes.     

Preparation and biological evaluation of radiogallium labeled glucagon for SPECT imaging

In this work, recently prepared ⁶⁷Ga-labeled glucagon (⁶⁷Ga-DTPA-GCG) for imaging studies (radiochemical purity >94%; HPLC, S.A. 296–370 GBq/mM) was used in biological studies. The wild-type rat biodistribution results, 2 h post injection, demonstrated high tissue:muscle ratios for target tissues (liver, kidney, heart, spleen, fat intestine stomach and pancreas), 234, 18.45, 7.12, 1.75, 128.7, 4.9, 6.3 and 1.11, respectively. The tracer binding capacity using freshly prepared rat brain homogenate demonstrated significant specific binding of the tracer to neuronal GCG receptors (⁶⁷Ga-DTPA-GCG/⁶⁷Ga:3 and ⁶⁷Ga-DTPA-GCG/⁶⁷GaDTPA:2.2 at 90 min). SPECT images also demonstrated target specific binding of the tracer at 4 h. The data suggests the tracer is accumulated in GCGR rich tissues 2–4 h post injection, suggesting potentials of the tracer for future imaging studies in glocagonoma models.     

Kit for instant 99mTc labeling of the antimicrobial peptide ubiquicidin 29-41

Summary The ubiquicidin 29-41 fragment (UBI) is a cationic antimicrobial peptide. The aim of this study was to develop an instant kit formulation for the preparation of ^99mTc-UBI 29-41 in high radiochemical yield and to evaluate its use as an infection imaging agent in humans. The components were selected to produce a direct ^99mTc labeling, presumably to the amine groups of Lys and Arg7. ^99mTc-UBI 29-41 obtained from the lyophilized kit showed radiochemical purity of >97% with an average target/non-target ratio of 2.3±0.6 in positive infection sites at 2 hours. Kits were stable at 4 °C for over 6 months.     

Preparation and Biological Evaluation of [99mTc]Tc-CNGU as a PSMA-Targeted Radiotracer for the Imaging of Prostate Cancer

Prostate-specific membrane antigen (PSMA) is a well-established biological target that is overexpressed on the surface of prostate cancer lesions. Radionuclide-labeled small-molecule PSMA inhibitors have been shown to be promising PSMA-specific agents for the diagnosis and therapy of prostate cancer. In this study, a glutamate-urea-based PSMA-targeted ligand containing an isonitrile (CNGU) was synthesized and labeled with ^99mTc to prepare [^99mTc]Tc-CNGU with a high radiochemical purity (RCP). The CNGU ligand showed a high affinity toward PSMA (K_i value is 8.79 nM) in LNCaP cells. The [^99mTc]Tc-CNGU exhibited a good stability in vitro and hydrophilicity (log P = −1.97 ± 0.03). In biodistribution studies, BALB/c nude mice bearing LNCaP xenografts showed that the complex had a high tumor uptake with 4.86 ± 1.19% ID/g, which decreased to 1.74 ± 0.90% ID/g after a pre-injection of the selective PSMA inhibitor ZJ-43, suggesting that it was a PSMA-specific agent. Micro-SPECT imaging demonstrated that the [^99mTc]Tc-CNGU had a tumor uptake and that the uptake was reduced in the image after blocking with ZJ-43, further confirming its PSMA specificity. All of the results in this work indicated that [^99mTc]Tc-CNGU is a promising PSMA-specific tracer for the imaging of prostate cancer.     

Labeling of ursodeoxycholic acid with technetium-99m for hepatobiliary imaging

An adopted method for the preparation of high radiochemical purity ^99mTc-ursodeoxycholic acid (UDCA) was conducted with a high radiochemical yield up to 97.5 %. The reaction proceeds well using 2 mg UDCA, 50 μg tin chloride in solution of pH 8 at room temperature for 30 min. The radiochemical yield was up to 97.5 % as pure as ^99mTc-UDCA. Different chromatographic techniques (paper chromatography and electrophoresis) were used to evaluate the radiochemical yield and purity of the labeled product. Biodistribution studies were carried out in Albino Swiss mice at different time intervals after administration of ^99mTc-UDCA. The uptake of ^99mTc-UDCA in the liver gave the chance to diagnose it. The results indicate that the labeled compound cleared from the systematic circulation within 2 h after administration and majority of organs showed significant decrease in uptake of ^99mTc-UDCA. Finally, the liver uptake was high and the results indicate the possibility of using ^99mTc-UDCA for hepatobiliary imaging.     

Synthesis and biodistribution of a novel <Superscript>99m</Superscript>Tc-DMSA-metronidazole ester as a potential tumor hypoxia imaging agent

The dimercaptosuccinic acid metronidazole ester (DMSAMe) was synthesized and radiolabeled with ^99mTc to form the ^99mTc-DMSAMe complex in high yield. The radiochemical purity of the ^99mTc-DMSAMe complex was over 90%, as measured by TLC and by HPLC, without any notable decomposition at room temperature over a period of 6 h. Its partition coefficient indicated that it was a lipophilic complex. The tumor cell experiment and the biodistribution in mice bearing S 180 tumor showed that the ^99mTc-DMSAMe complex had a certain hypoxic selectivity and accumulated in the tumor with high uptake and good retention. The tumor/blood and tumor/muscle ratios increased with time, suggesting it would be a possible tumor hypoxia imaging agent.