Enhancing specimen preparation for transmission electron microscopy: Trypan Blue staining and low-melting-point agar embedding for ultra-thin cell sections

The observation of ultrathin sections of cells and other specimens using transmission electron microscopy (TEM) is a standard technique in many biological research laboratories. Cells are typically collected, dehydrated through an ascending series of alcohols, and embedded in resin blocks before being sectioned with an ultramicrotome. This multi-step process can be time consuming and error prone. To address these challenges, we introduced modifications to improve sample visualization while avoiding hazardous substances like osmium tetroxide and epoxy resins (e.g., Araldite), which are increasingly regulated internationally. Specifically, we stained cells with Trypan Blue and used low melting point agar, facilitating visual identification of target areas and enabling precise embedding. As a result, visual tracking of samples prior to embedding for TEM was improved, preventing the cutting of empty blocks and ensuring efficient preparation of ultrathin sections.