Emerging synchrotron radiation X-ray-sensitive probes for in situ bioimaging at the nanoscale

X-ray imaging technologies have developed rapidly in bioimaging due to their unparalleled qualities such as nano-spatial resolution, three-dimensional panoramic observation, and element specificity, making up for the shortcomings of the traditional optical, electron, and super-resolution microscope. However, it has insufficient signal for specific imaging of cell biomolecules or structures. Hence, it is increasingly crucial to develop X-ray-sensitive probes. The targeted signal can be enhanced by integrating high-Z elements in probes to exploit the differential absorption and phase contrast with cellular components, leveraging the advantages of X-ray microscopy. In this review, we focus on the recent progress of X-ray probe-based imaging approaches from molecules to organ scales. We assess the advantages and limitations faced by these probes in X-ray imaging. Some future demands and improvements were suggested for further development of X-ray probes. These advancements are expected to inspire innovative bioimaging tools and new discoveries in cell biology and precise medicine.