Fixation on Histology

Sometimes a histology laboratory shopping list can look more like your own home shopping list, with the range of odd items that we have found uses for. One of those obscure items you may come across on your purchasing list is gelatin powder. Used more prevalently in histology days past, but still sometimes utilized, gelatin powder can be used in your water bath, not to make Jell-O, but as an adhesive; put a few tiny scoops into the water bath to help sections adhere to slides.

This is not frequently used nowadays because of the invention of products that incorporate that feature or make the benefits detrimental. For example, pre-coated slides eliminate the need for the gelatin’s adhesive properties. Gelatin powder can also not be used with charged slides, as it will compromise the charge. The prevalence of immunos has also lowered the use of gelatin powder as reports of background staining with IHC are prevalent using the gelatin water bath.

The one area where you may still find gelatin powder used is for silver stains. Charged slides are not recommended for silver stains because of the mirrored effect they cause, which makes gelatin in the water bath a more viable option for these stains. Specifically, you will see gelatin mentioned in relation to the Warthin Starry stain, a silver nitrate-based stain for the detection of spirochetes. (Spirochetes are a type of bacteria commonly causing diseases such as Lyme disease and syphilis.) Gelatin is used as an ingredient in the reducing solution that acts as a developer.

Resources:

https://bitesizebio.com/13423/starry-starry-night-no-warthin-starry-stain/