Direct Ultrastructural Imaging of Macrophages Using a Novel X‐Ray Contact Microscopy

A compact, high‐resolution, laser‐plasma, x‐ray contact microscopy method using a table‐top Nd:glass laser system has been developed. This x‐ray microscopy system was applied for the observation of macrophage ultrastructures. These images were produced using proximity imaging in which a 5‐ns pulse of soft x‐rays with wavelengths near and inside the water windows (23Å–44Å) produced by the laser‐plasma were absorbed by the specimen and then registered on a photo resist. The x‐ray images imprinted on the photo resist were then developed and analyzed with an atomic force microscope (AFM). Mouse thioglycollate‐elicited peritoneal macrophages in suspension were examined by this new x‐ray microscope. The x‐ray images of the macrophages were compared with those observed by conventional transmission electron microscopy (TEM). The x‐ray images showed no obvious organelles, including the nucleus and endoplasmic reticulum, as can be seen with TEM, but high‐ and low‐contrast structures caused by mass distribution of carbon were observed. Thus, using the x‐ray microscopy we visualized the first x‐ray images of macrophage ultrastructures. The successful x‐ray imaging of macrophage ultrastructure indicates that proximity x‐ray microscopy may be of value in studying physiology linked to the dynamics of a cell.