Basic Staining

Basic Staining

1. Stains/Dyes

   • Stain depends on chemical structure of tissues & cells
   • Usually dyes used that bind selectively to the tissue/cells
     • Resulting colours reflect nature of tissue /cells - 2 or more the give contrast
   • Binding tissues /cells to dyes like chem bonds
     • Ionic
       • Anionic dye to tissue cation
   • A dye is a coloured substance that has an affinity to the substance to which it is being applied.
     • Most modern dyes are synthesized from organic molecules like benzene or its derivitives
       • benzene etc. are normally colourless to the human eye and so must be coloured by suitable chromophores

2. Why Stain

   • All fixed materials are a dull and similar colour
   • Stain to view structures
     • Wax must be removed
       • Pre-stain = De-wax = Rehydrate
         • 1. Xylene/ Histoclear 3 mins
         • 2. Graded Alcohol (100 - 50%) to remove 1.
         • 3. water
         • 4. H&E or PAP, etc
         • 5. Dehydrate - graded alcohol (50 - 100%)
         • 6. Clear in xylene 1-2mins
         • 7. Mount in glycerol, DPX, coverslip
       • Obscures tissue structure & is poorly permeable to stains