The Congo red dye being a molecule that is linear

This method can be applicable to detect collagen fibres in some tissues for example heart and skin tissues on sections that are paraffin embedded and formalin fixed. At times, they may be used on frozen sections also (May and Schaitkin, 2000, p. 154). The method is also used to draw a distinction between smooth muscle and collagen in tumors and in collagen’s increase in sicknesses such as cirrhosis. “Trichrome stains are used mainly to differentiate collagen and muscle fibres and two of the most frequently used as far as skin is concerned are Van Gieson’s and Masson’s trichrome” (Marks, Dykes and Motley, 1993, p. 137).

For kidney and liver biopsies, it acts as a routine stain. The nuclei will be stained black, collagen fibres blue, whereas red is the color that muscle, cytoplasm and erythrocytes will be stained to. On the other hand, Congo red is a stain that has a high PH. It is used to detect amyloid in paraffin embedded tissue of patients who have amyloidosis (Burnett and Crocker, 2005, p. 24). It can still be applicable in frozen sections. The nuclei will be stained blue while the amyloid will be stained red. Congo red can be used in the detection of eosinophils (Howie, 2001, p. 14).

Most of the staining on amyloid by the Congo red special stain seems to be dependent on the configuration of dye. The Congo red dye being a molecule that is linear has a configuration that allows hydrogen bonding of the amine and azo groups of this dye to amyloid’s hydroxyl radicals that are equally spaced. Some methods allow for the pre-treatment of the section with alkali that helps in enhancing internal hydrogen bonding between protein chains that are adjacent. Consequently, these methods provide for more potential sites present for the bonding of the dye. A counterstain especially hematoxylin is normally carried out and ends up coloring the nuclei. After staining with Congo red, amyloid gets berefringent (Anon, 2006, p. 2).