Chromatographic Purification of Some Radiolabeled Photosensitizers of Expected Activity in Nuclear Medicine

Abstract

With the development of nuclear medicine, porphyrins were studied as radionuclide carriers for tumor delineation. Porphyrin and its derivatives exhibit inherent affinity for localization in tumors. Hence, porphyrin derivatives radiolabeled with suitable radionuclides could be envisaged as potential agents for tumor imaging. In this direction, two derivatives of porphyrin, namely 5,10,15,20-tetrakis(pentafluorophenyl) porphyrin (TFPP) and 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine (OEP) were radiolabeled with technetium-99m by direct technique using two different reducing agents; stannous chloride and sodium borohydride. The results showed that higher radiochemical yields of 94.52 ± 0.41% and 98.79 ± 0.43 % for 99mTc-TFPP and 99mTc-OEP, respectively, were obtained on using sodium borohydride reducing agent. Both radiolabeled complexes showed in-vitro stability, up to 8 hours. Different chromatographic techniques (paper chromatography, paper electrophoresis and high performance liquid chromatography) were used to evaluate the rediochemical yield and identify the purity of the final product. Biodistribution studies of 99mTc-TFPP and 99mTc-OEP complexes in tumor bearing mice showed high target/non target (T/NT) ratio, where T/NT= 4.84 ± 0.15 at 30 min post injection for 99mTc-TFPP complex and T/NT= 4.10 ± 0.05 at 60 min post injection for 99mTc-OEP complex, suggesting these complexes as a potential solid tumor imaging radiotracerers.

Keywords: Porphyrin, Technetium-99m, Tumor imaging, TFPP, OEP