Gadolinium-porphyrins: new potential magnetic resonance imaging contrast agents for melanoma detection

Background: two new porphyrin-based magnetic resonance imaging (mrl) contrast agents , gd-hematoporphyrin(gd-h) and gd-tetra-carboranylmethoxyphenyl-porphyrin (gd-tcp) were synthesized and tested in nude mice withhuman melanoma (mm-138) xenografts as new melanoma contrast agents.methods: subcutaneous xenografts of human melanoma cells (mm-138) were studied in 30 (five groups of six) nudemice. the effect of different contrast agents (gd-tcp, gd-h, gdci3 and gd-dtpa) on proton relaxation times wasmeasured in tumors and other organs. t) values, signal enhancement and the gd concentration for different contrastagent solutions were also investigated.results: the porphyrin agents showed higher relaxivity compared to the clincal agent, gd-dtpa. a significant 16%and 21% modification in t1 relaxation time of the water in human melanoma tumors grafted in the nude mice was revealed24 hours after injection ofgd-tcp and gd-h, respectively. the percentage of injected gd localized to the tumormeasured by inductively coupled plasma atomic emission spectrometry (icp-aes) was approximately 21% for gdtcpand 28% for gd-h which were higher than that of gd-dtpa (10%).conclusions: the high concentration of gd in the tumor is indicative of a selective retention of the compounds andindicates that gd-tcp and gd-h are promising mr imaging contrast agents for melanoma detection. gd-porphyrinshave considerable promise for further diagnostic applications in magnetic resonance imaging.