Silver-Methenamine Borate (SMB): Cost Reduction with Technical Improvement in Silver Nitrate-Gold Chloride Impregnations

AbstractThe solutions used in Grocott's methenamine-silver impregnation were reformulated into two stock solutions mixed in equal volumes immediately before use. Solution 1 is silver nitrate in a concentration of 2.1 grams per liter; solution 2 contains 27.0 grams of hexamethylenetetramine and 3.8 grams of sodium borate decahydrate per liter of water. When automatic dispensers are used, the reagent preparation time is reduced to 30 seconds. No glassware is required other than a Coplin jar for staining purposes. The average impregnation time was reduced to approximately 35 minutes. Because the solutions are combined just prior to use, the method is more consistently reproducible than methods calling for “stock“ methenamine-silver without added borate. This new silver methenamine/borate procedure (SMB) works for the demonstration of fungi in paraffin sections, for argentaffin granules in paraffin and plastic (2-hydroxyethylmethacrylate, HEMA) sections, and for basement membranes in both paraffin and plastic...