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Radiolabeling and biological evaluation of amphotericin using fac-[99mTc(I)(H2O)3(CO)3]+
Abstracts
assays with the unlabeled compounds were done in vitro. Tumor-cell uptake of the complexes was assayed in vitro at 37 °C and 4 °C. In vivo assays were carried out to study tumor accumulation and elimination pattern in C57BL/6 mice with B16F10 melanoma. Both complexes showed fast renal bioelimination and low hepatobiliary excretion. High tumor uptake was observed in biodistribution studies and SPECT images one hour post-injection of complexes.
http://dx.doi.org/10.1016/j.nucmedbio.2014.05.003
22 Radiolabeling and biological evaluation of amphotericin using fac-[99mTc(I)(H2O)3(CO)3]+ Leticia Fernández, Laura Reyes, Mariella Terán Cátedra de Radioquímica, Facultad de Química, Universidad de la República, Montevideo, Uruguay Mycoses are fungal infections that usually do not cause serious illness; nevertheless severe immunosuppression may compromise the patient's life. Infection identification and its discrimination from inflammation are a challenging dilemma. The implications of prompt diagnosis on the appropriate management of infectious foci's are vital for the patient's evolution. Nuclear medicine can be an alternative using a suitable radiotracer to detect infection sites [1]. The aim of this study is to assess the feasibility of radiolabeling amphotericin B using fac-[Tc(I)(H2O)3(CO)3]+ precursor and its physicochemical and biological evaluation as potential diagnostic agent for fast and accurate diagnose of fungal infections by scintigraphic images [2]. The complex was obtained with RCP higher than 90% and was stable up to 23 hours post-substitution. Lipophilicity value was − 0.7. Protein binding was 78% and no decomposition products of the complex were observed in plasma stability studies. In vitro binding to yeast was 40%. Biological evaluation was performed in 4 groups of CD1 mice G1: healthy, G2: sterile inflammation, G3: Candida albicans and G4: Aspergillus niger infections. Biodistributions were performed 3 and 6 hours post injection. Main elimination pathway was renal and target/non target ratios at 6 hours were: G2 = 2.4 ± 0.1; G3 = 9.1 ± 0.1; G4 = 1.9 ± 0.3. 99mTcTricarbonyl–amphotericin B complex is a promising agent for scintigraphic detection of C. albicans infections. References [1] Fernández L, et al. Alasbimn Journal 2013 [ISSN: 0717–4055]. [2] Alberto R, et al. J Am Chem Soc 1998;120:7987–8.
http://dx.doi.org/10.1016/j.nucmedbio.2014.05.054
23 Development of a 99mTc(I)-tricarbonyl complex as potential agent for hypoxia imaging S. Fernándeza, J. Gigioa, H. Cerecettob, A. Reya a
Cát. Radioquímica, Fac. de Química, UdelaR-Uruguay Centro Inv. Nucl., Fac. de Ciencias, UdelaR-Uruguay
b
Herein, we present the development of a 99mTc complex bearing the 5-nitroimidazol-1-yl moiety, with recognized hypoxic selectivity, as a potential radiopharmaceutical for imaging tumour hypoxia.
619
Metronidazole was used as starting reagent for the synthesis of the ligand sodium N-methyl-1-[1-(2-(2-methyl-5-nitro-1Himidazol-1-yl)ethyl)-1H-1,2,3-triazole-4-yl]methyl dithiocarbamate (L). Identity of the final product was confirmed by IR and NMR spectroscopy. 99m Tc labelling was achieved by reaction of fac-[99mTc(CO)3(OH2)3]+ (30–40 mCi) with L (4 mg) at 75 °C during 30 minutes. Two radiolabelled species in a 2.5:1 ratio were formed. Furthermore, the minor species reappeared after isolation of the main product by HPLC. The complex mixture is highly lipophilic (logP in octanol:phosphate buffer pH = 7.4: 1.47 ± 0.11) and exhibited high plasma protein binding (67.1 ± 2.1%). Biodistribution studies in C57BL/6 mice bearing induced 3LL Lewis carcinoma showed moderate tumour uptake (0.75 ± 0.01%/g), a slow hepatobiliary elimination and a high liver uptake (64.1 ± 7.0% at 2 h). In order to know the structure of these complexes, synthesis with stable rhenium was achieved. Mass spectrometry results suggest that L could act as bidentate ligand and a water molecule remains in the coordination sphere of the metal. This structure is compatible with physicochemical and biological results since lower thermodynamic stability of the complex with a bidentate ligand is expected. Consequently, the use of a monodentate coligand could be an alternative to improve in vitro but also in vivo behavior of the final complex. Acknowledgments ANII, Pedeciba-Química, Gramon-Bagó.
http://dx.doi.org/10.1016/j.nucmedbio.2014.05.086
24 A novel Tc-99m-labeled lactam bridge-cyclized alpha-MSH peptide with enhanced melanoma uptake Haixun Guo, Yubin Miao College of Pharmacy, University of NM, USA The purpose of this study was to examine the melanoma targeting and imaging properties of 99mTc-labeled lactam bridge-cyclized HYNIC-Aoc-Nle-CycMSHhex {hydrazinonicotinamide-8-aminooctanoic acid-Nle-c[Asp-His-DPhe-Arg-Trp-Lys]-CONH2} peptide. Methods: HYNIC-Aoc-Nle-CycMSHhex was synthesized using fluorenylmethyloxy carbonyl (Fmoc) chemistry. The melanocortin-1 (MC1) receptor binding affinities of the peptide were determined in B16/F1 melanoma cells. The melanoma targeting and imaging properties of 99mTc(EDDA)-HYNIC-AocNle-CycMSHhex were determined in B16/F1 melanoma-bearing C57 mice. Results: The IC50 value of HYNIC-AocNle-CycMSHhex was 0.3 ±0.06 nM in B16/F1 melanoma cells. 99mTc(EDDA)-HYNIC-AocNle-CycMSHhex displayed the highest melanoma uptake (22.3 ± 1.72% ID/g) at 2 h post-injection. 99mTc(EDDA)-HYNIC-AocNle-CycMSHhex exhibited high tumor to normal organ uptake ratios except for the kidneys. The tumor/kidney uptake ratios of 99mTc(EDDA)-HYNIC-AocNleCycMSHhex were 3.29, 3.63 and 6.78 at 2, 4 and 24 h post-injection. The melanoma lesions were clearly visualized by SPECT/CT using 99m Tc(EDDA)-HYNIC-AocNle-CycMSHhex as an imaging probe at 2 h post-injection. Conclusions: High melanoma uptake and fast urinary clearance of 99m Tc(EDDA)-HYNIC-AocNle-CycMSHhex highlighted its potential for metastatic melanoma detection in the future. http://dx.doi.org/10.1016/j.nucmedbio.2014.05.008
assays with the unlabeled compounds were done in vitro. Tumor-cell uptake of the complexes was assayed in vitro at 37 °C and 4 °C. In vivo assays were carried out to study tumor accumulation and elimination pattern in C57BL/6 mice with B16F10 melanoma. Both complexes showed fast renal bioelimination and low hepatobiliary excretion. High tumor uptake was observed in biodistribution studies and SPECT images one hour post-injection of complexes.
http://dx.doi.org/10.1016/j.nucmedbio.2014.05.003
22 Radiolabeling and biological evaluation of amphotericin using fac-[99mTc(I)(H2O)3(CO)3]+ Leticia Fernández, Laura Reyes, Mariella Terán Cátedra de Radioquímica, Facultad de Química, Universidad de la República, Montevideo, Uruguay Mycoses are fungal infections that usually do not cause serious illness; nevertheless severe immunosuppression may compromise the patient's life. Infection identification and its discrimination from inflammation are a challenging dilemma. The implications of prompt diagnosis on the appropriate management of infectious foci's are vital for the patient's evolution. Nuclear medicine can be an alternative using a suitable radiotracer to detect infection sites [1]. The aim of this study is to assess the feasibility of radiolabeling amphotericin B using fac-[Tc(I)(H2O)3(CO)3]+ precursor and its physicochemical and biological evaluation as potential diagnostic agent for fast and accurate diagnose of fungal infections by scintigraphic images [2]. The complex was obtained with RCP higher than 90% and was stable up to 23 hours post-substitution. Lipophilicity value was − 0.7. Protein binding was 78% and no decomposition products of the complex were observed in plasma stability studies. In vitro binding to yeast was 40%. Biological evaluation was performed in 4 groups of CD1 mice G1: healthy, G2: sterile inflammation, G3: Candida albicans and G4: Aspergillus niger infections. Biodistributions were performed 3 and 6 hours post injection. Main elimination pathway was renal and target/non target ratios at 6 hours were: G2 = 2.4 ± 0.1; G3 = 9.1 ± 0.1; G4 = 1.9 ± 0.3. 99mTcTricarbonyl–amphotericin B complex is a promising agent for scintigraphic detection of C. albicans infections. References [1] Fernández L, et al. Alasbimn Journal 2013 [ISSN: 0717–4055]. [2] Alberto R, et al. J Am Chem Soc 1998;120:7987–8.
http://dx.doi.org/10.1016/j.nucmedbio.2014.05.054
23 Development of a 99mTc(I)-tricarbonyl complex as potential agent for hypoxia imaging S. Fernándeza, J. Gigioa, H. Cerecettob, A. Reya a
Cát. Radioquímica, Fac. de Química, UdelaR-Uruguay Centro Inv. Nucl., Fac. de Ciencias, UdelaR-Uruguay
b
Herein, we present the development of a 99mTc complex bearing the 5-nitroimidazol-1-yl moiety, with recognized hypoxic selectivity, as a potential radiopharmaceutical for imaging tumour hypoxia.
619
Metronidazole was used as starting reagent for the synthesis of the ligand sodium N-methyl-1-[1-(2-(2-methyl-5-nitro-1Himidazol-1-yl)ethyl)-1H-1,2,3-triazole-4-yl]methyl dithiocarbamate (L). Identity of the final product was confirmed by IR and NMR spectroscopy. 99m Tc labelling was achieved by reaction of fac-[99mTc(CO)3(OH2)3]+ (30–40 mCi) with L (4 mg) at 75 °C during 30 minutes. Two radiolabelled species in a 2.5:1 ratio were formed. Furthermore, the minor species reappeared after isolation of the main product by HPLC. The complex mixture is highly lipophilic (logP in octanol:phosphate buffer pH = 7.4: 1.47 ± 0.11) and exhibited high plasma protein binding (67.1 ± 2.1%). Biodistribution studies in C57BL/6 mice bearing induced 3LL Lewis carcinoma showed moderate tumour uptake (0.75 ± 0.01%/g), a slow hepatobiliary elimination and a high liver uptake (64.1 ± 7.0% at 2 h). In order to know the structure of these complexes, synthesis with stable rhenium was achieved. Mass spectrometry results suggest that L could act as bidentate ligand and a water molecule remains in the coordination sphere of the metal. This structure is compatible with physicochemical and biological results since lower thermodynamic stability of the complex with a bidentate ligand is expected. Consequently, the use of a monodentate coligand could be an alternative to improve in vitro but also in vivo behavior of the final complex. Acknowledgments ANII, Pedeciba-Química, Gramon-Bagó.
http://dx.doi.org/10.1016/j.nucmedbio.2014.05.086
24 A novel Tc-99m-labeled lactam bridge-cyclized alpha-MSH peptide with enhanced melanoma uptake Haixun Guo, Yubin Miao College of Pharmacy, University of NM, USA The purpose of this study was to examine the melanoma targeting and imaging properties of 99mTc-labeled lactam bridge-cyclized HYNIC-Aoc-Nle-CycMSHhex {hydrazinonicotinamide-8-aminooctanoic acid-Nle-c[Asp-His-DPhe-Arg-Trp-Lys]-CONH2} peptide. Methods: HYNIC-Aoc-Nle-CycMSHhex was synthesized using fluorenylmethyloxy carbonyl (Fmoc) chemistry. The melanocortin-1 (MC1) receptor binding affinities of the peptide were determined in B16/F1 melanoma cells. The melanoma targeting and imaging properties of 99mTc(EDDA)-HYNIC-AocNle-CycMSHhex were determined in B16/F1 melanoma-bearing C57 mice. Results: The IC50 value of HYNIC-AocNle-CycMSHhex was 0.3 ±0.06 nM in B16/F1 melanoma cells. 99mTc(EDDA)-HYNIC-AocNle-CycMSHhex displayed the highest melanoma uptake (22.3 ± 1.72% ID/g) at 2 h post-injection. 99mTc(EDDA)-HYNIC-AocNle-CycMSHhex exhibited high tumor to normal organ uptake ratios except for the kidneys. The tumor/kidney uptake ratios of 99mTc(EDDA)-HYNIC-AocNleCycMSHhex were 3.29, 3.63 and 6.78 at 2, 4 and 24 h post-injection. The melanoma lesions were clearly visualized by SPECT/CT using 99m Tc(EDDA)-HYNIC-AocNle-CycMSHhex as an imaging probe at 2 h post-injection. Conclusions: High melanoma uptake and fast urinary clearance of 99m Tc(EDDA)-HYNIC-AocNle-CycMSHhex highlighted its potential for metastatic melanoma detection in the future. http://dx.doi.org/10.1016/j.nucmedbio.2014.05.008