Question

Why is fixing necessary for most staining procedures?

Answer 1

Answer: Fixation step in staining procedure is one of the crucial steps. Fixation is significant because of the following reasons:

1. It retains the shape of the cell

2. In case of microbial staining, fixation of microbial cells helps to kill the bacteria and help them to remain on the slide

3. It alters the cell organelles in a fashion that it becomes compatible with the staining and counterstaining procedure
4. It allows the researcher to easily differentiate between the different types of cells or between the different cell organelles inside the cells
5. In many cases fixative is used with the aim of providing mechanical strength to the tissue
6. It also halts the ongoing biochemical reactions in tissue thereby preventing the further decay of tissue

Fixative agent and the overall process of fixation varies depending upon the objective of the study. A most commonly practiced fixation process is heat-fixation, which is done by passing the air-dried smear on the slide through the flame of the bunsen burner. It allows to heat kill the bacteria and also to attach them to slide for a further staining procedure. Other than heat fixation chemical fixation methods are also widely practiced and the significant ones that need to be mentioned are formaldehyde and methanol. Formaldehyde works by cross-linking
the primary amino groups present in proteins with available nitrogen in other biomolecules and methanol act as the protein denaturant. Nowadays cryopreservation fixation of tissue, where tissues are stored in the cryoprotective medium is also gaining popularity as it a fast-paced and needs no exposure to chemical fixatives.