The Wet Tissue SEM - A New Technology with Applications in Drug Development and Safety

Abstract

Scanning electron microscopy of wet tissue, wet SEM (WETSEM™), is a new technology that permits ultrastructural examination of fully hydrated biological samples. This review provides a description of this innovative achievement in relation to its reported and potential applications in pathology and toxicology. Possessing LM, SEM and TEM functionality, wet SEM provides a resolution that enables visualizing common ultrastructural targets of disease and toxicity, such as mitochondria and the cytoskeleton. Additionally, this confluence of multiple microscopic modalities allows for a continuous spectrum of inspection options for all structural aspects of cells and tissues. Broad overviews of the sample surface smoothly interdigitate with a detailed scrutiny of the cell interior. Elemental microanalysis and immuno-gold labeling are also possible with the wet SEM, which facilitates diagnostic applications and structuralfunctional correlations. Importantly, all these options are possible on the same sample during a single scoping session using one instrument. Since hydrated material is being directly examined, there is no need for embedment and microtome sectioning, so that preparation time is minimal. With such a rapid preparation phase and multifaceted inspection options, wet SEM appears particularly advantageous for the multi-arm design of drug development and safety studies. Naturally, as in any new form of microscopy, limitations exist that should be appreciated, and the image repertoire will need to be defined so that the most suitable and practical applications can be identified. Within its niche, wet SEM is likely to serve as a uniquely useful tool in pathological investigation. (J Toxicol Pathol 2007; 20: 1-11)

Calcium phosphate mineralization in bone tissues directly observed in aqueous liquid by atmospheric SEM (ASEM) without staining: microfluidics crystallization chamber and immuno-EM

“…Environmental capsules were developed to image wet samples for TEM 11–13 and SEM 14 . Such systems have been successfully employed to image hydrophilic molecular complexes 15 , cells 16 and tissues 17,18 . This development led to the first visualization of biological mineralization in wet conditions.…”

Observation of tissues in open aqueous solution by atmospheric scanning electron microscopy: Applicability to intraoperative cancer diagnosis

“…The surface level of tissue blocks excised from various organs (heart and kidney) ( 5 ), kidney ( 6 ), brain tumor ( 7 , 8 ), liver, sciatic nerve, spinal cord ( 9 ), colon ( 10 ) has been successfully observed in an environmental capsule by scanning electron microscopy (SEM). Environmental capsules allow ‘wet’ samples to be examined in the vacuum of the microscope, avoiding dehydration artifacts.…”

Differentiating Trypanosoma cruzi in a Host Mammalian Cell Imaged in Aqueous Liquid by Atmospheric Scanning Electron Microscopy

“…This technique permits the presence of very thin layer of water above the specimen in a low vacuum at temperatures just above freezing point. For more stable liquid-phase observation, environmental capsules have been developed for TEM ( 10 – 12 ) and SEM ( 13 ), which have been successfully used to image hydrophilic molecular complexes ( 14 ) as well as cells ( 15 ) and tissues ( 16 , 17 ). Previously, related protozoan parasite T. brucei was observed under SEM in wet condition using such sealed capsule ( 13 ).…”