In-Cell Quantification of Drugs by Magic-Angle Spinning Dynamic Nuclear Polarization NMR

The determination of intracellular drug concentrations can provide a better understanding of the drug function and efficacy. Ideally, this should be performed nondestructively, with no modification of either the drug or the target, and with the capability to detect low amounts of the molecule of interest, in many cases in the mu M to nM range (pmol to fmol per million cells). Unfortunately, it is currently challenging to have an experimental technique that provides direct quantitative measurements of intracellular drug concentrations that simultaneously satisfies these requirements. Here, we show that magic-angle spinning dynamic nuclear polarization (MAS DNP) can be used to fulfill these requirements. We apply a quantitative N-15 MAS DNP approach in combination with N-15 labeling to quantify the intracellular amount of the drug [N-15]CHIR-98014, an activator of the Wingless and hit-1 signaling pathway, determining intracellular drug amounts in the range of tens to hundreds of picomoles per million cells. This is, to our knowledge, the first time that MAS DNP has been used to successfully estimate intracellular drug amounts.

Automated summary

Determination of intracellular drug concentrations is crucial for understanding drug function and efficacy, but currently there is no experimental technique that satisfies the requirements of nondestructive measurement, no modification of drugs or targets, and detection of low concentrations. In this study, the use of magic-angle spinning dynamic nuclear polarization technique is proposed to fulfill these requirements, and successful estimation of intracellular drug amounts is demonstrated for the first time.