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A new bone imaging agent,99Tcm-BIPrDP, its preparation and biological properties

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Author:
No author available
Journal Title:
Chinese Journal of Nuclear Medicine and Molecular Imaging
Issue:
5
DOI:
10.3760/cma.j.issn.2095-2848.2012.05.014
Key Word:
BIPrDP;锝;小鼠;骨骼;放射性核素显像;BIPrDP;Technetium;Mice;Skeleton;Radionuclide imaging

Abstract: Objective To investigate the feasibility of 99Tcm-1-hydroxy-3-(2-butyl-1H-imidazol-1-yl) propane-1,1-diphosphonic acid (BIPrDP) as a new bone imaging agent.Methods BIPrDP was synthesized by three steps from the raw material 2-butyl-1H-imidazole.99Tcm-BIPrDP were prepared with mixed BIPrDP (50 mg/ml,100 μl) and freshly eluted Na99TcmO4 (37.0 MBq) in the presence of the reducing agent SnCl2 (1 rng/ml,100 μl) at boiling temperature for 30 min.The labeling yield and stability of 99Tcm-BIPrDP were measured with TLC.Partition coefficient in octanol-water and plasma protein binding ratio to human heparin anticoagulation plasma of 99Tcm-BIPrDP was checked.ICR mice were sacrificed at 5,10,15,30,60,120 and 240 min after tail vein injection of 0.2 ml (7.4 MBq) freshly prepared 99Tcm-BIPrDP.Samples of blood,heart,liver,spleen,lung,kidney,bone,muscle,gonad,intestine,stomach and brain were taken,weighed and the gamma counts measured.The biodistribution of the radiolabeled compound in different organs was calculated and expressed as % ID/g.Bone-to-organ uptake ratios were calculated by the % ID/g values.The kinetics of blood clearance was calculated.Bone imaging was performed in New Zealand rabbit after intravenous injection of 99Tcm-BIPrDP.One-way analysis of variance was used to analyze the % ID/g at different times points.Results Radiolabeling yield of 99Tcm-BIPrDP was more than 95% and the labeled complex was stable at least up to 6 h in vitro.The octanol-water partition coefficients (log P) for 99Tcm-BIPrDP were-2.396 ± 0.035 and-2.242 ± 0.025 at pH values of 7.0 and 7.4,respectively.The plasma protein binding rate of 99Tcm-BIPrDP was (47.07 ± 0.05)%.The bone uptake of 99Tcm-BIPrDP in mice reached a maximum of 19.20 % ID/g at 30 min after injection,and this high level of uptake persisted 4 h later at 18.98 % ID/g.Kidney uptake was highest among all the non-target organs,but decreased from 24.50 % ID/g at 5 min to 5.22 % ID/g at 4 h.The labeling compounds were excreted mainly through the kidneys,and the uptake in other important organs were extremely low.The muscle and brain exhibited the two lowest uptake,with values of 0.18 % ID/g and 0.03 % ID/g at 4 h,respectively.The uptake of blood was 18.60 % ID/g at 5 min,and then decreased rapidly; the uptake was only 0.40 % ID/g at 4 h.The pharmacokinetic equation was C =9.109e-0.262t + 2.696e-0.00558t.From the blood kinetic curve,it was concluded that the complex 99Tcm-BIPrDP eliminated rapidly from the blood,which was consistent with the biodistribution results in mice.A clear bone image of rabbit was obtained 1 h after the injection of 99Tcm-BIPrDP,which suggested that the selectivity of bone absorption was very good.Low uptake and rapid clearance in other soft tissues could be seen from the whole-body images.The % ID/g at different time points was significantly different (F=5.65-859.24,all P<0.05).Conclusion The preparation of 99Tcm-BIPrDP is convenient and exhibits high uptake in bone,which suggests its potential as a novel bone imaging agent.

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