EDITOR'S NOTE: This is the first article in an ASU feature series that will highlight the tools of the trade scientists use in their quest for new discoveries.
Scientists probe the mysteries of the natural world across an astonishing range of dimensions, from the subatomic domain of quarks and leptons to walls or sheets of supercluster galaxies known as filaments – gargantuan structures measuring over a billion light years across.
Cells and other features of the living microworld figure between these extremes. Their domain was first brought into focus when investigators in antiquity began to develop an ever-expanding toolkit to assist their observations.
Among the powerful techniques available to modern researchers is the laser confocal scanning microscope. One such instrument can be found at Arizona State University’s Biodesign Institute, where it is used extensively for imaging varied biological specimens. The Institute’s Zeiss Duo Scanning Laser Microscope is overseen by Doug Daniel, who also assists with other sophisticated optical instruments used for Institute research.
Confocal is a form of fluorescence microscopy, in which the molecules of the material under study are rendered into an excited state by means of high-intensity light. In response to this excitation, the sample will emit light of longer wavelength – this is the fluorescence that will form the image. A small aperture or pinhole a few tens of microns in diameter, located in the detection pathway, acts to reject of any out-of-focus light, ensuring that the final image will reveal the specimen in vivid detail. This differs from conventional light microscopy in which images are a composite of both in focus and out of focus signals.
One of the critical features of confocal microscopy is its ability to image successive layers through a specimen. These slices can then be reassembled by computer into highly detailed 3-D images. Many post-imaging techniques can also be applied, Daniel said, which can reveal delicate details that would otherwise be lost.
The popularity of confocal microscopy in biology and clinical medicine has grown significantly in recent years, thanks to the instrument’s ability to easily produce stunningly detailed images, with minimal sample preparation. By comparing normal cells with those associated with diseases such as cancer, diabetes or Alzheimer’s, scientists have made progress in identifying internal cellular components that may go awry during the transition to a diseased state.
Neuronal images in the slideshow were produced by Dr. Page Baluch from the School of Life Sciences Keck Bioimaging Laboratory.
Written by Richard Harth
Biodesign Institute science writer