Metal Organic Polyhedron with Four Fe(III) Centers Producing Enhanced T1 MRI Contrast in Tumors

• Published in: Inorganic chemistry 2022-01, Vol.61 (5), p.2603-2611
• Main Authors: Sokolow, Gregory E., Crawley, Matthew R., Morphet, Daniel R., Asik, Didar, Spernyak, Joseph A., McGray, A. J. Robert, Cook, Timothy R., Morrow, Janet R.
• Format: Article
• Language: English
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.1c03660

A metal organic polyhedron (MOP) with four paramagnetic Fe(III) centers was studied as a magnetic resonance imaging (MRI) probe. The MOP was characterized in solution by using EPR and UV-vis spectroscopies, FT-ICR mass spectrometry, and in the solid state with single crystal x-ray diffraction. Water proton T 1 relaxation properties were examined in solution and showed significant enhancement in the presence of human serum albumin (HSA). The r 1 relaxivities in the absence and presence of HSA were 8.7 mM −1 s −1 and 21 mM −1 s −1 , respectively, per molecule (2.2 and 5.3 per Fe) at 4.7 T, 37 °C. In vivo studies of the iron MOP show strong contrast enhancement of blood pool even at a low dose of 0.025 mmol/kg with prolonged residence in vasculature and clearance through the intestinal tract of mice. The MOP binds strongly to serum albumin and shows comparable accumulation in a murine tumor model as a covalently linked Gd-HSA contrast agent.