| Bisphosphonates with a imidazole ring have higher affinity for bone mineral,and zoledronate is just a good example which is extensively used clinically for the treatment of patients with tumour-induced,hypercalcaemia and osteolytic bone metastases. 2-(2-ethylicimidazol-1-yl)-1-hydroxyethane-1,1-diphosphonic acid (EIDP) that has the similar structure to zoledronic acid,is therefore considered potentially useful as a bone-imaging agent if labeled with 99Tcm,which has not been reported in and abroad. 99Tcm-EIDP was therefore prepared for bone imaging in order to develop a new excellent bone-imaging agent.EIDP was synthesized by three steps from the raw material 2-ethylicimidazol. 99Tcm- EIDP was prepared by the reduction of 99Tcm-pertechnetate in the presence of SnCl2˙2H2O.The effects of the amounts of SnCl2˙2H2O and EIDP and pH value on the radiochemical purity and labeling yield of 99Tcm- EIDP were investigated.Meantime, some properties such as shape character, EIDP purity,pH value,labeling method and yield,stability were controlled.Some biological characters including pharmacokinetics,plasma protein binding ratio,partition coefficients, biodistribution and bone scan were studied;also a comparison among 99Tcm- EIDP, 99Tcm-MIDP 99Tcm-ZL and 99Tcm-MDP was made.EIDP and intermediates were all identified by IR,elementary analysis,MS and HNMR. When the amounts of EIDP and SnCl2˙2H2O were more than 3.0mg and 50μg,respectively;the pH value was between 2 and 7 ,and the labeling reaction continued for 10min,both radiochemical purity and labeling yield of 99Tcm- EIDP were over 90% and remained within 6 hours.The pharmacokinetic equation was C=1090.736e-6.982t + 84.956e-0.379t ,the plasma protein binding rate and partition coefficients were 20.00% and 0.0011 (pH7.0), 0.0017 (pH7.4).The results of biodistribution and bone scan showed that the bone uptake was up to 23.76%ID/g at 60min after injection of 99Tcm-EIDP,bone-to-muscle and bone-to-blood uptake ratios were 95.04and 33.94,respectively.The clear bone image was obtained at 120min after injection of 99Tcm-EIDP and clearance in renal was visible.The bone-imaging of 99Tcm-EIDP is superior to 99Tcm-MIDP,99Tcm-ZL and is correspond to 99Tcm-MDP .The preparation of 99Tcm- EIDP is convenient and 99Tcm- EIDP has good stability,which express that 99Tcm- EIDP is an excellent bone-imaging agent and is worth developing.
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