Professor Jia-Ming Liu and his students have built a prototype stimulated emission depletion microscope that achieves sub-diffraction resolution imaging capabilities at a fraction of the expected cost

By Wileen Wong Kromhout

As biological research advances, the need to see smaller and smaller objects is increasingly important. Knowing the location of intercellular constituents, such as proteins, lipids, or nucleic acids, will help scientists elicit the causes for diseases and develop subsequent cures. Since these objects are less than 10 nanometers in size, imaging systems with super-resolution capabilities is needed.

Now, using commercial off-the-shelf photonics components, Electrical Engineering Professor Jia-Ming Liu and his students, Margaret Chiang and Juan Garcia, have built a prototype STED (stimulated emission depletion) microscope that achieves sub-diffraction resolution imaging capabilities at a fraction of the cost normally expected of a STED microscope.

Through intensive studies into the physics of STED microscopy, the group was able to break the diffraction limit by 18.5%. Along the way, the group has invented new methods and simpler approaches that allowed the system to be built less expensively. The group hopes that their efforts will lead to greater acceptance of STED microscopy that will subsequently open up a new era of biological investigations.

The next version of their STED microscopy system will employ a higher magnification objective lens, which along with their new hardware approach, will enable the group to achieve resolutions beyond what has been demonstrated with STED microscopy.

Several microscopy approaches have been invented that are capable of super-resolution. However, while the electron microscopy, scanning tunneling microscopy, atomic force microscopy, and near-field light microscopy can see tiny objects, these techniques are limited to surface imaging and/or are destructive to live cells. Therefore, for biological applications, far-field light microscope is still preferred by scientists.

For more than a century, the resolution of a far-field light microscope was confined by Abbe’s diffraction limit. Recently, various techniques have been developed to successfully break the diffraction limit and achieve super-resolution. The stimulated emission depletion (STED) microscopy technique has an advantage over the others by requiring minimal post-processing.

However, it was not readily adopted into the mainstream due to the complexity and cost of the system. In fact, for more than a decade since the concept was proposed, no research group working independently of STED microscopy’s founder had demonstrated STED microscopy capabilities. Furthermore, no such system had been developed in the United States until now.

Professor Liu’s group is actively seeking funding for the next phases and is excited about nearing the development of the first STED microscope system in the United States.

This research was partially supported by University of California Systemwide Biotechnology Research & Education Program GREAT Training Grant #2006-04.