Applications of Polarized Light Microscopy

In polarized light microscopy, plane polarized light is passed through a double refracting material and then collected using a second polarizing filter to generate a high-contrast image. This technique finds application in several fields, such as medicine, basic biology, industry, and to study rock minerals.

Photo through a microscope of crystals growing from the melt of sulfur. Polarized light technology. Image Credit: alex7370 / Shutterstock
Photo through a microscope of crystals growing from the melt of sulfur. Polarized light technology. Image Credit: alex7370 / Shutterstock

Medical Applications

Gout diagnosis

Gout occurs because of the deposition of urate crystals in the synovial fluid of the joints which causes inflammation and pain. Polarized microcopy is used to examine synovial fluid for the diagnosis of gout. Urate crystals causing gout have negative elongated optical features, while pyrophosphoric acids which cause pseudo-gout have positive optical features. These differences in the crystal direction and the interference colour on polarized light microscopy are used to differentiate these crystals.

Amyloid protein examination

Amyloid proteins are created by abnormal metabolism of proteins which leads to their aggregation within cells. These proteins may be deposited in various organs, such as the spleen, liver, kidney, brain among others. These aggregates are not observed in normal cells. Using polarized light, these amyloid structures can be visualised. The presence of amyloid proteins is ascertained by the appearance of a bright green color on polarization light microscopy.

Applications in Basic Biology

Polarized light microscopy is used to visualize several birefringent or double-refractive structures in the body, including teeth, striated bone, muscle tissue, neurons, spindles, and actomyosin fibers. These structures can be visualized with great contrast by adding a dye; however, as these are living structures, this step causes cell death. Thus, this technique offers a non-invasive method of high-contrast imaging for these tissues and cells. Polarized light microscopy does not require any contrast agent or dye, can be performed in a non-invasive manner, and generates high-contrast images.

Examination of Rocks

Polarized light microscopy can be used to examine rock structures and their optical characteristics. This method can also be used to identify minerals inside rocks. Two methods are used for this purpose.

Transmitted polarizing microscopy

In this method, a rock cutter is used to cut a thin slice of rock. One side is polished and the specimen is fixed on to a glass slide using an adhesive. Subsequently, the opposite side is also polished and fixed to a cover glass using balsam.

Immersion method

In this method, the rock is ground to a fine powder and then sprinkled on a glass slide. The powder is surrounded with an immersion liquid and then a cover slip is added. However, in this method the structure of the rock is destroyed. The advantage is that it does not require the preparation of thin rock sections.

Applications in Industry

Liquid crystals

Liquid crystals are materials with properties in between liquids and solids. Polarizing microscopes are used to detect peculiar optical patterns and phase defects in liquid crystals. They can also be used to determine if a crystal is optically positive or negative. Liquid crystal retardation can also be measured using polarized microscopes.

Macromolecular materials

Spherulites are transparent, double refractive materials of spherical shape, belonging to the class called macromolecular crystals. Polarized microscopes can be used to determine their density and size which in turn determines the strength and transparency.

Food chemicals

Polarized microscopes can be used to determine the properties of emulsions of butter and cream as they possess optical anisotropy. Thus, using this method, any deviations in the emulsion conditions or impurities can be determined.

Glass and ceramics

Polarized microscopy can be used to determine the quality of and defects in glass and ceramics by identifying their colour, shape, diffraction index, and crystal impurities.

Metals

Metal inspection for composition, surface impurities and properties is possible using polarizing microscopy on a polished metal sample.

Further Reading

Last Updated: Aug 24, 2018

P Surat

Written by

P Surat

Surat graduated with a Ph.D. in Cell Biology and Mechanobiology from the Tata Institute of Fundamental Research (Mumbai, India) in 2016. Prior to her Ph.D., Surat studied for a Bachelor of Science (B.Sc.) degree in Zoology, during which she was the recipient of an Indian Academy of Sciences Summer Fellowship to study the proteins involved in AIDs. She produces feature articles on a wide range of topics, such as medical ethics, data manipulation, pseudoscience and superstition, education, and human evolution. She is passionate about science communication and writes articles covering all areas of the life sciences.  

Comments

The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of News-Medical.Net.
Post a new comment
Post
You might also like... ×
University of Wuerzburg implements new turnkey confocal imaging system