Evaluation of a 99mTc-labelled meso-bisphenylporphyrin as a tumour image agent

Porphyrins are excellent agents for photodynamic treatment of various types of cancer and also good metal chelators that form highly stable metallo-complexes with different radionuclides. Therefore, radiolabelled porphyrins could also be potentially used as tumour imaging agents. In this context, the aim of this work was the radiolabelling of meso-bis[3,4-bis(carboxymethyleneoxy)phenyl]porphyrin, 2CPP, with Technetium-99 m (Tc-99m) and the evaluation of its radiochemical and biological properties in vitro and in vivo. The labelling procedure was optimized resulting in an efficiency of 92.52 +/- 0.48%. The complex (TC)-T-99m-2CPP remained stable for more than 4 h. The biodistribution showed that Tc-99m-2CPP is eliminated by gastrointestinal and urinary pathways. The tumour/muscle ratio increases over time, being 3.33 +/- 1.22 and 3.55 +/- 1.29 in WiDr-bearing tumours mice and in H1299-bearing tumours mice, respectively, 6 h post-injection, showing the tumour specificity of the Tc-99m-2CPP complex. The favourable tumour/muscle ratio of Tc-99m-2CPP shows that this complex could potentially be used as tumour imaging agent. Moreover, it could be used to follow the progression or regression of tumours before, during and after the radiotherapy, chemotherapy and photodynamic therapy.