Dr. Priya Ramakrishna: Correlative cryoSEM-CryoNanoSIMS mapping of vitrified biological tissue

Recording of Dr. Priya Ramakrishna's talk on April 25, 2024, at the EPFL Seminar Series in Imaging. Abstract: Nanoscale Secondary Ion Mass Spectrometry (NanoSIMS) is an ion microprobe based imaging technique that produces quantified maps of chemical and isotopic variations in a wide range of materials with high lateral resolution (typically 100 nm). NanoSIMS is often used to understand complex transport and metabolic processes in living organisms. However, a big challenge has been to preserve the samples' natural state during analysis. The recent development of a CryoNanoSIMS by Prof. Anders Meibom and team at EPFL now enables examination of vitrified biological samples, i.e. samples prepared for analysis without loss or significant displacement of cell constituents, including soluble compounds. This breakthrough enables high-resolution imaging of elements in biological tissue in its most pristine state. In this seminar, I will present the cryo-workflow that includes vitrification by high pressure freezing, cryoplaning of the sample surface, cryoSEM imaging for ultrastructure and correlative CryoNanoSIMS for isotopic and chemical imaging of biological tissues. I will present a case study from plant developmental biology in which the CryoNanoSIMS has been used to visualize multiple physiologically important elements in vitrified plant roots at the subcellular scale, greatly expanding our understanding of salinity stress in plants, which causes significant loss of crop-yield globally.