Lanthanide(III)-based metallacrowns functionalized with ruthenium(II) complexes for multiplex imaging and oxygen sensing in the NIR-II
Résumé
Oxygen is one of the key metabolites in aerobic organisms. Oxygen deprivation (hypoxia) is connected to various diseases, including cancers, cardiovascular diseases and strokes.[1] Therefore, it is essential to quantify oxygen levels in biological systems in real-time to ensure an early diagnosis of dysfunction. Multiplex imaging in the second near-infrared window (NIR-II, 1000–1700 nm) opens new perspectives for the comprehensive understanding of complex biological processes and for more accurate diagnosis of diseases by enabling real-time acquisition of images with improved contrast and spatial resolution in deeper tissues.[2] However, today, the number of suitable NIR-II imaging agents remains highly limited. Lanthanide(III)-based metallacrowns (MCs) belong to a class of metal complexes that have demonstrated unique luminescence properties and perspectives to be used as NIR-II imaging agents.[3-6] In this work, we present synthetic pathways to generate two families of Ln(III)/Ga(III) MCs functionalized with Ru(II) complexes. Detailed photophysical studies have been performed in air- and N2-saturated solutions. We have shown that the characteristic emissions of Yb(III), Nd(III) and Er(III) in the NIR-II range can be sensitized upon excitation in the visible range, through Ru(II)-centered metal-to-ligand charge transfer states. In contrast to many fluorescent oxygen sensors for which the presence of the analyte induces a decrease of the emission signal, the presence of oxygen leads to the enhancement of Ln(III)-centered emission in studied Ln(III)/Ga(III) MCs. NIR-II imaging experiments using capillaries and biological tissue-mimicking phantoms have shown that signals arising from different Ln(III) can be detected and discriminated unambiguously.