Europium(III) DOTA-tetraamide complexes as redox active MRI sensors

摘要

PARACEST redox sensors containing the NAD⁺/NADH mimic N-methylated quinolinium moiety as redox active functional group have been designed and synthesized. The Eu³⁺-complex with two quinolinium moieties was nearly completely silent in CEST in the oxidized form, but “turns on” upon reduction with β-NADH. The CEST effect of the Eu³⁺- complex containing only one quinolinium group was much less redox responsive but showed an unexpected sensitivity to pH in the physiologically relevant pH range.