Apr 5, 2004
Hybrid imaging beats resolution limit
Scientists in the US claim to have found a new way to image tiny structures and molecules, such as DNA, which are smaller than the 200 nm diffraction-limited resolution of optical microscopes.
Dehong Hu and Peter Lu from the Pacific Northwest National Laboratory (PNNL) in Washington State, revealed their technique to delegates at the American Chemical Society's national meeting which took place in Anaheim, California last week.
The duo have successfully combined fluorescence lifetime imaging microscopy (FLIM) with atomic force microscopy (AFM) to generate sharp images of fluorescing nanobeads which are just 40 nm in diameter, as well as a cluster of DNA molecules.
The technique involves scanning a gold-tipped silicon wand over a fluorescing sample. Hu says that the gold tip generates a strong electric field when illuminated with a laser and that the interaction between the sample and this field provides the contrast for the image.
The hybrid imaging technique is non-destructive and is thus ideal for probing the structure of biological molecules, such as DNA.
In the image above, a cluster of DNA molecules about 1 micron long appear blurred when imaged by FLIM alone (left). However, when the new technique is used the structure of the molecules can be seen.
PNNL is a laboratory for the US Department of Energy and investigates complex problems in the fields of energy, national security, the environment and life sciences. It employs 3800 staff and has a $600 m annual budget.
About the author
Oliver Graydon is editor of Optics.org and Opto & Laser Europe magazine.