Bimetallic porphyrin PET radiotracers for Low-Dose MRI contrast enhancement

In medical imaging, concerns over the risks associated with imaging agents have been consistently raised by doctors and patients, and ongoing efforts are being made to cautiously explore safer and more efficient com­pounds. There is continued interest in combining the well-known imaging modalities of positron emission to­mography (PET) and magnetic resonance imaging (MRI). However, there has not been reported a singlemolecule probe offering dual-modal imaging without performance degradation. We herein present a potential solution wherein the compound, PGaLGd, incorporates radioactive Ga(III) for PET imaging whilst simultaneously being able to exhibit MRI contrast through a coordinated Gd(III) ion but at low concentrations/doses. Besides elucidating MRI enhancing mechanisms through computational chemistry techniques, our compound has proven to be a successful dual-imaging agent for both PET and MRI in mice. Additionally, we conducted comprehensive in vitro and in vivo studies, assessing biosafety and photodynamic therapeutic potential across various cell lines and organoids. We have placed importance on interlinking structures, coordinated metals, adjacent ligands, and frontier molecular orbitals in our probe design to enhance water relaxation ability and move towards the design of next-generation low-dose imaging agents.