A Novel Tumor Hypoxia Imaging Agent: [^99mTc]Tc(CO)3-CPA-2-NIM

Introduction: Hypoxia imaging agents can selectively remain in hypoxic tissue, which can directly reflect the location and degree of hypoxia. Methods: Synthesized a novel tumor hypoxia imaging probe [^99mTc]Tc(CO)3-CPA-2-NIM and evaluated its biological behavior with the purpose to assess its possibility of becoming a qualified tumor hypoxia imaging agent. Results: Radiochemcial purity of [^99mTc]Tc(CO)3-CPA-2-NIM was greater than 95% after HPLC purification. Lipophilicity coefficient of this complex was -1.74 ± 0.10 (n = 5, number of experiments), indicating it was a hydrophilic complex. In vitro cell experiments demonstrated that this complex has selectivity for hypoxia at oxygen concentrations < 10 ppm (parts per million). Biodistribution experiment in S180 tumor bearing mice showed that tumor uptake reached its highest at 2 h post-injection with mice tumor-to-muscle ratio. Conclusions: Complex [^99mTc]Tc(CO)3-CPA-2-NIM has the possibility of becoming a tumor hypoxia imaging agent.