Molecular Concentration Determination Using Long-Interval Chemical Exchange Inversion Transfer (CEIT) NMR Spectroscopy.

Functionalized hyperpolarized xenon "cage" molecules have often been used for ultrasensitive detection of biomolecules and microenvironment properties. However, the rapid and accurate measurement of molecule concentration is still a challenge. Here, we report a molecule concentration measurement method using long-interval chemical exchange inversion transfer (CEIT) NMR spectroscopy. The molecule concentration can be quantitatively measured with only 2 scans, which shortens the acquisition time by about 10 times compared to conventional Hyper-CEST (chemical exchange saturation transfer) z-spectrum method. Moreover, we found that the accuracy of concentration determination would be the best when the CEIT effect is 1-1/e or close to it, and a relative deviation of CrA-(COOH)6 less than ±1% has been achieved by only a one-step optimization of the number of cycles. The proposed method enables efficient and accurate determination of molecule concentration, which provides a potential way for rapid quantitative molecular imaging applications.