Tetraphenylporphyrin-based dual-functional medical agent for magnetic resonance and fluorescence imaging

A bimodal magnetic resonance imaging contrast agent, TPP-M-Gd, was developed by modifying tetraphenylporphyrin (TPP) with a small dendritic molecule as a ligand (M) to chelate gadolinium (Gd) ions. The ligand featured four carboxylate groups, which contributed to good water solubility and a strong combination with metal ions. The longitudinal relaxivity (R-1) of the resulting agent was calculated to be 12.45 mM(-1) s(-1), which is much higher than that of DTPA-Gd (4.49 mM(-1) s(-1)). The magnetic resonance imaging experiments showed that the newly synthesized contrast agent could enhance T-1-weighted magnetic resonance imaging quality both in vitro and in vivo. In addition, TPP-M-Gd exhibited good fluorescent property as shown in cell imaging experiments. The cytotoxicity of TPP-M-Gd was even better than that of clinically approved DTPA-Gd, which makes it a promising dual-functional medical imaging agent to provide more detailed information about biological and disease-related events.