what is the purposes of staining microscopy

Many dyes, however, require the use of a mordant: a chemical compound which reacts with the stain to form an insoluble, coloured precipitate. For larger pieces of tissue, thin sections (slices) are made using a microtome these slices can then be mounted and inspected.Īt its simplest, the actual staining process may involve immersing the sample (before or after fixation and mounting) in dye solution, followed by rinsing and observation. For samples of loose cells (as with a blood smear or a pap smear) the sample can be directly applied to a slide.

In some cases, cells may be grown directly on a slide. Mounting usually involves attaching the samples to a glass microscope slide for observation and analysis. Pieces of tissue may be embedded in paraffin wax to increase their mechanical strength and stability and to make them easier to cut into thin slices. Common fixative include formaldehyde, ethanol, methanol, and/or picric acid. Most chemical fixatives (chemicals causing fixation) generate chemical bonds between proteins and other substances within the sample, increasing their rigidity. Sometimes heat is used to kill, adhere, and alter the specimen so it will accept stains. This treatment will dissolve the cell membranes, and allow larger dye molecules access to the cell's interior.įixation–which may itself consist of several steps–aims to preserve the shape of the cells or tissue involved as much as possible. Permeabilization involves treatment of cells with (usually) a mild surfactant. The preparatory steps involved depend on the type of analysis planned some or all of the following procedures may be required. A safranin counterstain is applied which stains all cells, allowing the identification of Gram-negative bacteria as well. For example, crystal violet stains only Gram-positive bacteria in Gram staining. A counterstain is stain that makes cells or structures more visible, when not completely visible with the principal stain. Combined with specific protocols for fixation and sample preparation, scientists and physicians can use these standard techniques as consistent, repeatable diagnostic tools. Certain stains are often to reveal more details and features than a single stain alone. In vitro staining involves colouring cells or structures that are no longer living. 1.2.3 Haematoxylin and eosin (H&E) staining.

What is the purposes of staining microscopy