RELAXIVITY MEASUREMENT OF PORFHYRIN-BASED MAGNETIC RESONANCE IMAGING (MRI) CONTRAST AGENTS

摘要

Magnetic Resonance Imaging (MRI) has become a prominent imaging technique in medicine. MRI contrast agents are used to increase the sensitivity of this technique. Recently, a new method for cancer treatment with a less side effect called photodynamic therapy (PDT) has been introduced. In this method cancer tissues are selectively destroyed without injuring the surrounding healthy cells. However, for the successful use of this method, the selection of an appropriate photosensitizer is important. Hence, diagnosis-treat union of MRI and PDT will be significantly promoted if a new family of bi-functional agents is found, which would combine the effects of a contrast agent in MRI and of a photosensitizer in PDT. It will bring great improvement to the cancer diagnosis and treatment. Porphyrins have proved to be useful photosensitizing agents in PDT due to their promising photophysical efficiency and a less side effect. This work briefly describes the research development of porphyrins as a photosensitizer applied in PDT, and also highlights the recent progress in the research on bi-fonctional agents of MRI-PDT. Diethylenetriamine pentaacetic acid (DTPA) units are incorporated at a meso-position of the porphyrin ring to synthesize new bi-functional agents of MRI-PDT with sufficient water solubility and high relaxation potency. Gd~(3+) complexes are prepared by the reaction of the high molecular weight porphyrin-based ligand with GdCl3 · 6H2O. The longitudinal relaxivity measurement indicates 154% and 251 % enhancement compared to that of the widely used MRI contrast agent Gd—DTPA. These results indicate that the two complexes could possibly be used as bi-functional agents of MRI-PDT.