Wednesday, December 18, 2013

Why Biologists Prefer Phase Contrast Microscopes

Why would a biologist prefer a phase contrast microscope over a standard brightfield microscope? Here are a few reasons why phase contrast microscopes are preferred by many biologists over a variety of other microscopes available to them.

image of cheek cells under microscope captured with phase contrast
Cheek cells - phase contrast
image of cheek cells under microscope with brightfield
Cheek cells - brightfield

The images shown above are both of the exact same slide of human cheek cells. The image shown at left was captured with brightfield and the image at right was captured with phase contrast.
  1. A phase contrast microscope allows viewing a clear (transparent) specimen - a living cell - without staining the specimen, which effectively kills it, thereby eliminating the time consuming process of staining the specimen. This is preferred by biologists since living cells can be studied during cell division.
  2. Light passing through a clear specimen undergoes phase changes, brightening areas of the specimen that creates a contrast against the darker areas. This contrast of light and dark makes the specimen visible to the human eye. This is important to biologists because the light contrasts with various mechanisms of the specimen, such as the membrane, cilia and flagella, against a lighter/darker background, making them visible under the microscope. Of importance in molecular biology, the phase contrast microscope enables biologists working in such fields as cancer research and developmental biology to distinguish one type of cell from another.
  3. Phase contrast microscopes are capable of 50x to 1000x magnification. Such magnification is important to biologists because it allows visibility of activities at the cellular level such as protein motility, autography, cell signaling, and metabolism thereby broadening our understanding of cells.
  4. A phase contrast microscope can be used for brightfield, (often darkfield) and phase contrast. Whereas a brightfield microscope can typically only be used for brightfield work.
phase contrast microscope image
Differences between a phase contrast microscope and a brightfield microscope.