Coherent X-ray Diffraction Imaging Study of Hydrated Biological Specimens

Abstract

Coherent diffraction imaging, also called as lens-less imaging, is able to reconstruct an image with high-resolution and high-contrast by collecting oversampled diffraction patterns in far-field region and calculating numerical phase without using any lenses. Combining this technique and x-ray, it enables to probe thick biological specimens without invasive sectioning, staining, and crystallizing.We developed a versatile coherent x-ray diffraction microscope. This newly developed microscope has the most noticeable advantage which is its capability of imaging biological specimens in their natural state. This versatile coherent diffraction microscope is designed to record diffraction patterns as a result of interaction between x rays and samples kept in thin solution film. Flexible operating modes, from low vacuum to helium ambience pressure, of this microscope and solution cell holder are available to image samples immerged in solution.We, for the first time, demonstrated wet coherent diffraction imaging technique capable of imaging fully hydrated and unstained whole cells with nano-scale resolution and high-contrast. By using two silicon nitride membranes, the specimens are kept in hydrated state without structural disruption due to dehydration. We acquired the images of fully hydrated and intact biological specimens: yeast cell and cyanobacteria. In this demonstration, we used 5 keV x rays to collect oversampled diffraction patterns by using synchrotron radiation and the reconstructed images by using GHIO algorithm show their morphological information and intercellular compartments clearly with better than 25 nm resolution.