The majority of samples are thinly cut sections as this enables great visualization of the cells in the normal range of the light microscope. These slices need to be adhered to a slide, and may need further treatment depending on the embedding medium used. Paraffin embedding makes the sections impervious to water, so they need to be run through clearing agents and graded alcohols to enable the aqueous antibodies to interact with the tissues.
Points to consider:-
Slide Adhesives
Depending on the method to be used, sections may be challenged with a variety of solvents, numerous washes, temperatures and agitated solutions. If sections are not well stuck, your sample can be washed away. There is no universal slide adhesive that is perfect for all applications as some may interfere with the detection systems to be used.
Gelatin is a simple, but a relatively weak adhesive.
Egg white is cheap, however like gelatin, it's not particularly durable and is likely to cause issues when working with biotin based systems, as egg white is a source of avidin.
Poly-l-lysine imparts a negative charge to the slide which attracts the positively charged tissue elements.
VECTABOND and aminopropyltriethoxy silane (APES) imparts a positive charge to the slide which attracts negatively charged tissue elements.
The solutions imparting charges to the slides are usually robust enough for IHC methods, although each can still have its problematic tissues, fatty tissues and calcified tissues tend to be amongst those hardest to stick.
Section Adhesives
Labelling Slides
With the variety of solutions used in the laboratory, finding an ink solvent that is resistant not only water, but to organic solvents too, can be tricky.
We've found some pens to be resistant to most laboratory chemicals and suitable for writing on slides, although frosted glass slides are still recommended.
Labelling Pens
Hydrophobic Barrier
Using a barrier pen around sections can help retain expensive reagents on sections, and also maintain a deeper layer of reagent over the sample, reducing the likelihood of sections having artifacts from drying. Some laboartories may use barrier pens to enable the use of different reagents on parts of the section.
N.B. Hydrophobic barriers should be applied after de-paraffinisation/ rehydration of FFPE tissues; the organic solvents can remove the barrier.
Barrier Pens