SEM of Biological Surface

Surface Observation Using Electron Microscopy 4.1. SEM of Biological Surface 

The basic procedure of biological sample preparation for SEM involves in specimen fixation, dehydration, drying, and coating (see Ref 27 for a comprehensive review of procedures). The purpose of fixation is to immobilize the cellular components, such 

Following the glutaraldehyde fixation, the tissue should be washed thoroughly before post-fixation with osmium tetroxide, which mainly forms cross-finks among lipids. Osmium tetroxide can also help to enhance the electron signal and reduce electron charging. Osmium tetroxide (l%-2%) is commonly used and usually the fixation is done at the same temperature used for aldehyde fixation. 

In sublimation, an organic compound (Peldri II for example) that is miscible with dehydrant is added in the final stage of dehydration. The compound becomes solid and then subhmes without producing surface-tension eflFects.  

An alternative of critical point drying or subfimation is liquid substitution, in which a low-vapor-pressure liquid, such as glycerol or triethylene glycol, is used to infiltrate the sample and the sample can be examined by SEM without drying and coating. This technique has been successfully applied to different biological samples.  

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