Assessing Cellular Uptake of Exogenous Coenzyme Q into Human Skin Cells by X-ray Fluorescence Imaging.

X-ray fluorescence (XRF) imaging is a highly sensitive non-invasive imaging method for detection of small element quantities in objects, from human-sized scales down to single-cell organelles, using various X-ray beam sizes. Our aim was to investigate the cellular uptake and distribution of Q, a highly conserved coenzyme with antioxidant and bioenergetic properties. Q was labeled with iodine (I-Q) and individual primary human skin cells were scanned with nano-focused beams. Distribution of I-Q molecules taken up inside the screened individual skin cells was measured, with a clear correlation between individual Q uptake and cell size. Experiments revealed that labeling Q with iodine causes no artificial side effects as a result of the labeling procedure itself, and thus is a perfect means of investigating bioavailability and distribution of Q in cells. In summary, individual cellular Q uptake was demonstrated by XRF, opening the path towards Q multi-scale tracking for biodistribution studies.