A novel bisphosphonate derivative (1-aminoethane-1,1-diyl)diphosphonic acid (AEDP) has been prepared and successfully labeled with 99mTc at high labeling yields. The in vivo biodistribution of 99mTc-AEDP has been investigated and compared with two reference compounds Tc-99m methylene diphosphonate (99mTc-MDP) and Tc-99m (1-hydroxyethylidene) diphosphonate (99mTc-HEDP). The biodistribution studies have demonstrated a high uptake of the radiotracer 99mTc-AEDP in the bone and a rapid clearance from the blood (such as the two technetium-labeled bone imaging agents in current use: 99mTc-MDP and 99mTc-HEDP). Additionally, the scintigraphic images of 99mTc-AEDP in normal rats have revealed high selective skeletal uptake.
The preparation of 165Dy-labeled chitosan for radiosynovectomy applications is described in this paper. 165Dy (T1/2 = 2.33 h) was prepared by irradiation of natural Dy(NO3)3 at a flux of 3.4 x 1013 neutrons/cm2.s for about 6 h. The irradiation resulted in the production of 11.1 GBq (300 mCi) of 165Dy activity. Emitting gamma ray (94.7 keV) and beta particles (Emax = 1.3 MeV, 83%) 165Dy decays to 165Ho. Eight hours after bombardment, the corresponding specific activity was 703 MBq/mg (19 mCi/mg). The irradiated target was dissolved in 0.1 N HCl solution. Radionuclidic purity was ascertained by high resolution gamma spectrometry. Chitosan solution was prepared in acetic acid solution (pH 3). The chitosan solution was labeled with 165Dy to prepare 165Dy-chitosan (165Dy-Chit) complex (labeling yield, greater than 99% and specific activity small tilde 3.7 TBq/mmol). In optimized conditions (pH 3, 35 mg/4 ml chitosan acidic solution, and 370 MBq of 165Dy) Chit was stable after 48 h. Bioevaluation of the prepared 165Dy-Chit was carried out by injecting 37 MBq (1 mCi, 50.100 mi1) directly into the knee joints of wild rats. Free 165Dy cation was also injected to study the effect of complex formation on the retention of radionuclide in the administered site. To study the consequence of radioactivity leakage from the administration site, a dilute sample of the complex was injected intravenously into the rats followed by biodistribution studies. It was observed that there was no significant extra-articular leakage of the injected activity over the study period of 24 h post-injection.
Due to interesting therapeutic properties of 177Lu and antineoblastic antibiotic, bleomycin (BLM), 177Lu-bleomycin (177Lu-BLM) was developed as a possible therapeutic compound. Lu-177 of 2.6-3 GBq/mg specific activity was obtained by irradiation of a natural Lu2O3 sample with a thermal neutron flux of 4 × 1013 nźcm-2źs-1. The product was converted into chloride form which was further used for labeling of BLM. In optimized conditions a radiochemical purity of 98% was obtained for 177Lu-BLM shown by instant thin-layer chromatography (ITLC) (specific activity, 740 GBq/mmole). Biodistribution studies of Lu-177 chloride and 177Lu-BLM were performed in wild-type rats. The accumulation of the radiolabeled compound in lungs, liver and spleen demonstrates a pattern similar to the other radiolabeled bleomycins. Lu-BLM is a possible therapeutic agent in human malignancies and the efficacy of the compound should be tested in various tumor-bearing models.
In order to develop a possible Ga-labeled glucagon (GCG) compound for imaging studies, biosynthetic glucagon (GCG) was labeled with [67Ga]-gallium chloride after conjugation with freshly prepared diethylenetriaminepentaacetic acid dianhydride (ccDTPA). After solid phase purification of the radiolabeled hormone, high performance liquid chromatography (HPLC) and instant thin-layer chromatography (ITLC) showed a radiochemical purity around 95 per cent in optimized conditions (specific activity = 296–370 GBq/mM; labeling efficiency 85 per cent). Preliminary in vivo studies (IDźg–1 per cent) in male wild-type rats showed heart:muscle, liver:muscle, lung:muscle and stomach:muscle ratios to be 5.53, 2.9, 7.56, 3.69, 3.2 (in 5 min), respectively while after 2 h liver:blood, lung:blood and spleen:blood ratios were 14.21, 16.86 and 7.8, respectively. The data suggests 5 min post injection, the tracer is accumulated in GCGR rich tissues which is in agreement with biodistribution studies and reported GCG receptors (GCGRs). The results of the present study can possibly offer a candidate for non-invasive imaging of glucagon receptor related diseased and malignancies such as glucagonoma.
Due to interesting role of dihydropyridines in cardiovascular diseases and drug resistance studies and lack of a fluorine-18 labeled imaging agent for L-type calcium channel studies, this study was designed. [18F]Dimethyl 2-(fluoromethyl)-6-methyl-4-(2-nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylate 2 was prepared in no-carrier-added (n.c.a.) form from a starting brominated compound in one step at 80°C in Kryptofix2.2.2/[18F]. Compound 2 was administered to normal rats via their tail veins for preliminary biodistribution studies and the ID/g% of the labeled compound was determined up to 3 h post injections. Coincidence images were obtained in rats 5 to 120 min. Radiofluorination on bromo precursor gave a fluorinated compound in 95% radiochemical purity and a 8% yield shown by RTLC and HPLC. Biodistribution studies showed that the tracer is accumulated in the heart in the first few minutes, followed by metabolism resulting in very soluble 18F-containing metabolites eliminated through the urinary tract. In coincidence images, the target organ was shown to be the heart. Lung had high accumulation possibly due to the presence of Ca2+ channels and/or hydrolyzing enzymes showing a significant myocardial uptake at 120 min. The data demonstrates a significant agreement with the reported L-type calcium channels throughout the animal body. To our knowledge, this is the first example of 18F-DHPs in the literature.
Human recombinant insulin was successively labeled with [67Ga]-gallium chloride after conjugation with freshly prepared cyclic DTPA-dianhydride (ccDTPA). The best results of the conjugation were obtained by the addition of 0.5 ml of an insulin pharmaceutical solution (5 mg/ml, in phosphate buffer, pH = 8) to a glass tube precoated with DTPA-dianhydride (0.01 mg) at 25°C with continuous mild stirring for 30 min. Radiothin-layer chromatography (RTLC), instant thin-layer chromatography (ITLC) and high-performance liquid chromatography (HPLC) showed overall radiochemical purity higher than 96% in optimized conditions (specific activity = 300 500 MBq/mg, labeling efficiency 77%). Preliminary in vivo studies with normal rats were performed to determine the biodistribution of the radiotracer up to 110 h. They showed a high liver uptake of the tracer which is consistent with other reported radiolabeled insulins.
Abstract Bleomycin (BLM), labeled with radioisotopes, is widely used in therapy and diagnosis. In this study, BLM was labeled with 62Zn for oncologic PET studies. The complex was obtained at pH = 2 in saline at 90°C in 25 min. Radio-TLC showed an overall radiochemical yield of 95 97% (radiochemical purity > 97%). Stability of complex was checked in vitro in mice and human plasma/urine. Preliminary in vivo studies were performed to determine complex stability and distribution of 62Zn BLM in normal and fibrosarcoma-bearing mice. 62Zn BLM accumulated significantly in induced fibrosarcoma tumors in mice according to biodistribution/imaging studies. 62Zn BLM can be used in PET oncology studies due to its suitable physicochemical properties as a diagnostic complex in vitro and in vivo. Further studies should be performed for evaluation of the complex behavior in larger mammals.
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