Towards tender X-rays with Zernike phase-contrast imaging of biological samples at 50 nm resolution

X-ray microscopy is a commonly used method especially in material scienceapplication, where the large penetration depth of X-rays is necessary for three-dimensional structural studies of thick specimens with high-Z elements. In thispaper it is shown that full-field X-ray microscopy at 6.2 keV can be utilized forimaging of biological specimens with high resolution. A full-field Zernike phase-contrast microscope based on diffractive optics is used to study lipid dropletformation in hepatoma cells. It is shown that the contrast of the images iscomparable with that of electron microscopy, and even better contrast at tenderX-ray energies between 2.5 keV and 4 keV is expected