Dual T and T weighted magnetic resonance imaging based on Gd loaded bioinspired melanin dots.

In this report, a novel T/T dual modal nanoprobe based on highly efficient and bioinspired melanin dots (M-dots) with directly loading gadolinium (Gd-M-dots) for magnetic resonance imaging (MRI) is described. In vitro and in vivo investigations have revealed that Gd-M-dots showed nontoxicity and good biocompatibilitity. Gd-M-dots relaxivity values on 3 T were determined to be r = 23.4 and r = 123.3 mM s, which were much higher than both Gd-DTPA (r = 5.1, r = 6.2 mM s) and Fe-M-dots (r = 1.2, r = 2.1 mM s). For in vivo MRI, after injection of Gd-M-dots, simultaneous T and T contrast enhancement have been observed in the MRI of mice abdomen and mice bearing U87MG tumors. Furthermore, all the veins showed high signal intensity on T-weighted MRI and remained for 2 h. Overall, in vitro and in vivo studies indicate that Gd-M-dot with high r relaxivity and r relaxivity has high potential to be a promising nanoprobe for MR venography and molecular imaging.