Synthesis and Biological Evaluation of Novel 99mTc-Labelled Bisphosphonates as Superior Bone Imaging Agents

A series of novel zoledronic acid (ZL) derivatives 1-hydroxy-3-(2-methyl-1H-imidazol-1-yl)propane-1,1-diyldiphosphonic acid (MIPrDP), 1-hydroxy-4-(2-methyl-1H-imidazol-1-yl)butane-1,1-diyldiphosphonic acid (MIBDP), and 1-hydroxy-5-(2-methyl-1H-imidazol-1-yl)pentane-1,1-diyldiphosphonic acid (MIPeDP) were prepared and successfully labeled with 99mTc in high labeling yields. The in vitro stability and in vivo biodistribution of 99mTc-MIPrDP, 99mTc-MIBDP and 99mTc-MIPeDP were investigated and compared. The biodistribution studies indicate that the radiotracer 99mTc-MIPrDP has highly selective uptake in the skeletal system and rapid clearance from soft tissues. The present findings indicate that 99mTc-MIPrDP holds great potential for use in bone imaging.