Can we develop an early warning system for patients after cell transplantation therapy using X-ray imaging?

Over the last decades, several new therapeutic concepts which include the transplantation of cells have been developed for diseases of the central nervous system (CNS). The migration of implanted cells away from the intended transplantation site as well as tumour formation from unchecked cell proliferation are potential risks of such therapeutic approaches. In order to follow cell migration and possibly proliferation we have developed a technique that allows detection and tracking of implanted cells which have been marked with gold nanoparticles (GNPs) prior to implantation into the host organism. The GNP-loaded cells provide sufficient contrast to be detected with synchrotron X-ray imaging methods. Very small cell clusters and even individual cells can be detected. The price for the high spatial resolution is the exposure of implanted cells and host organism to comparably high radiation doses during the imaging procedures. Therefore, before advocating use of the technique to follow up larger series of transplantation experiments in small animal models of CNS disease it is absolutely mandatory to obtain experimental evidence regarding the threshold X-ray dose above which single or repeated imaging would interfere with the functionality of GNP-loaded cells. Only once this question has been answered should the possibility to develop this method towards clinical application be considered.