Fe(II), Co(II) and Ni(II) complexed DOTA-tetraglycinates as pH and temperature biosensors

Motivation: Gadolinium based contrast agents (GBCAs) are reported to be toxic and associated with nephrogenic systemic fibrosis (NSF). Alternative options should be developed to minimize toxicity. Goal(s): Develop alternative biocompatible transition metal-based MRI agents for advanced imaging. Approach: Using paramagnetic high spin Fe(II), Co(II), and Ni(II) ions coordinated with well-established cyclic ligands for enhanced MRS imaging to detect cancer tumors at an early stage. Results: Fe(II)DOTA-4AmC2-, Co(II)DOTA-4AmC2-, and Ni(II)DOTA-4AmC2- were synthesized and characterized. Their in vitro pH and temperature sensing capabilities were assessed using BIRDS at 11.7T. Impact: These biocompatible pH sensors can be employed for in vivo pH mapping for early cancer diagnosis and can also be adapted for clinical applications.