Tissue marking dyes are pivotal to maintaining the correct specimen orientation during grossing and marking tissue margins in sample preparation. However, choosing the correct colours can have a big impact on how they perform during fixation, dehydration, clearing, and embedding processes and ensuring the dyes are visible under the lighting conditions used in your laboratory (e.g. in brightfield microscopy). Here are a few tips on how to make the most out of your tissue marking dyes and how to choose the right colours.
High Contrast
Choose colours that provide high contrast against the background tissue to facilitate easy identification and differentiation under the microscope. For example, using a combination of dark colours (e.g. blue, red, black) on light-coloured tissues and light-coloured dyes (e.g. yellow) on dark-coloured tissues will enable you to identify tissue margins more easily when the sample is at the microscopy stage.
You also need to consider the contrast against stains such as Hematoxylin (blue/purple) and eosin (pink) using colours such as green, yellow, red, or black would stand out against such stains.
Lastly, ensure the dye is stable enough so that it retains its colour through fixation, dehydration, clearing, and embedding processes. High-quality, permanent tissue dyes such as the Davidson Marking Systems Tissue Marking Dyes offer durable pigments that will permanently bind to the tissue and maintains its strong pigmentation on the tissue all the way through to microscopy examination.
Versatility
The tissue structure can influence the dyes performance, select colours that can be easily applied to various tissues and structures without compromising their visibility or staining quality. Choose dyes that adhere well to tissue sections and provide long-lasting marking.
Soft Tissues: Use darker or more vibrant dyes for soft tissues to ensure visibility after processing.
Hard Tissues: For denser or more fibrous tissues, bright dyes like yellow or orange will be more effective.
Thin Sections: For thin tissue sections, less intense dyes, your lighter coloured dyes might be sufficient, while thicker sections may require more robust, darker colouring.
Compatibility
Ensure that the chosen colours are compatible with the staining protocols and techniques being used in the histological analysis. Some dyes may interact with certain stains or fixatives, leading to undesirable effects or interference with the staining process.
Consistency
Maintain consistency in colour usage throughout, use the same colour scheme consistently across different samples to avoid confusion and enable quicker identification of sample orientation, this facilitates continuity and ease of sample interpretation.
When to use each colour:
Red
Strong contrast with blue and purple stains, good for highlighting specific areas.
Blue
Contrasts well with eosin, and is useful for marking larger areas.
Yellow
Visible against darker stains and useful for fine markings.
Green
Provides a good contrast with
both hematoxylin and eosin.
Black
Highly visible against most backgrounds,
ideal for marking margins.