Stain uptake depends upon the tissue element's affinity for the dye component of the stain solution. Affinity refers to the tendency of a dye to transfer from a staining solution onto the tissue section.
Factors that affect staining include:
- Concentration of the dye - The more significant the concentration of the dye, the more the dye is bound to tissue components.
- Temperature - An increase in temperature increases the rate at which the dye diffuses throughout the tissue sample. It can also alter tissue components, making them more receptive to dye penetration.
- pH of the staining solution - Cells and other tissue elements often have an affinity for stains/dyes with specific pH ranges. Thus, the pH of the staining solution can directly impact a dye's ability to bind with its intended tissue element.
- Tissue fixation - Fixation alters and reorganizes specific molecular structures in tissue samples, increasing their permeability and receptivity to staining. Unfixed tissue elements have limited binding sites for dyes.
