Ultrastructural analysis of Drosophila melanogaster using Helium Ion Microscopy. Dennis R. LaJeunesse^1,3, Adam Boseman¹, Kyle Nowlin¹, Jijin Yang². 1) Dept Nanoscience, Joint School of Nanoscience and Nanoengineering, Greensboro, NC; 2) Carl Zeiss NTS, LLC, Peabody, Massachusetts; 3) Department of Biology, UNCG, Greensboro, NC 27402.

   Scanning electron microscopy (SEM) has been the traditional method used to image the micro and nanoscale surface topology of biological samples. Here, we present a new ultrahigh resolution particle beam microscopy technology, called Helium Ion Microscopy (HIM), which is exceptional for imaging surface structures on biological samples at the nanometer scale. While operationally similar to SEM, HIM uses a beam of helium ions to probe a surface. This offers several unique advantages. HIM eliminates the need to use a conductive metal coating on the sample, thereby allowing the imaging of biological samples in their natural state. This allows the resolution of surface details that were concealed beneath a sputtered layer. Additionally, the low mass of the helium ion yields a small footprint for the generation of secondary electrons in biological materials. This permits imaging at high magnification without decreasing beam energy, thus resulting in higher resolution. The result is an increased depth of field, allowing three-dimensional surfaces to be imaged with uniform clarity across the field of view. In this study we use HIM to characterize cuticular nanostructures in the epicuticle of wild type and mutant Drosophila melanogaster. Of note, we identified novel linear arrays of 55nm nanoribs that decorate the macro and microchaetes of the adult body. In this presentation we will also demonstrate the utility of HIM for imaging cells and cellular components, such as the actin cytoskeleton and polytene chromosomes. HIM provides a powerful new tool for characterization of biological samples at the nanoscale. The identification and characterization of nanoscale structures in Drosophila melanogaster allows the use of genetic and molecular tools to facilitate the functional characterization of these structures, as well as the identification and characterization of the composition and mechanisms involved in the formation of these nanostructures.