HyperCEST Potential of Members of the Cucurbit[n]uril Family: Revised Signal Assignment and Suitable Host Identification with Accelerated MRI

The full potential of the ultra-sensitive approach of HyperCEST MRI crucially depends on host structures with efficient release of hyperpolarized 129Xe. Cucurbit[n]urils (CB6 and CB7) have been proposed as promising candidates but a quantitative analysis of CEST signatures yet remained an open question. Here, we use MRI-derived z-spectra of multiple samples which provide strong evidence that CB7 is unsuitable as CEST agent and that previously observed signals are solely assigned to CB6 which is also side product in CB7 synthesis. Image acquisition with >20-fold acceleration for the 4-dimensional datasets is possible without compromising a detailed quantitative analysis.