High Exchange Rate Complexes of Xe with Water-Soluble Pillar[5]arenes for Adjustable Magnetization Transfer MRI.

Macrocyclic host structures for generating transiently bound Xe have been used in various ultra-sensitive NMR and MRI applications for molecular sensing of biochemical analytes. They are based on hyperpolarized nuclei chemical exchange saturation transfer (Hyper-CEST). Here, we tested a set of water-soluble pillar[5]arenes with different counterions in order to compare their potential contrast agent abilities with that of cryptophane-A (CrA), the most widely used host for such purposes.