Resonance Energy Transfer Technology Reveals Insights into Molecules in Living Cells

Chemists have developed a method to significantly improve the longevity of fluorescent nanoparticles that may someday help researchers track the motion of a single molecule as it travels through a living cell.

The chemists, from Clemson University (Clemson, SC, USA), are utilizing a process called resonance energy transfer, which occurs when fluorescent dye molecules are added to the nanoparticles. If scientists could track the motion of a single molecule within a living cell, it could reveal a host of information. Among other things, researchers could determine how viruses invade a cell or how proteins function in the body. Such technology also could help scientists target the precise location of cancer cells to better focus treatment and minimize damage to healthy tissue. Outside the body, the technology could help speed up detection of such toxins as anthrax.

The key to developing single-molecule tracking technology may be the development of improved fluorescent nanoparticles. Fluorescent nanoparticles are thousands of times smaller than the width of a human hair and are similar in size to protein molecules, to which they can be attached. When illuminated by a laser beam inside a light microscope equipped with a sensitive digital camera, a nanoparticle attached to a protein will light up, allowing scientists to get an exact fix on the position of the protein and monitor its motion inside a cell.

Until now, nanoparticles have been too dim to detect inside cells, but Clemson chemists have developed an innovative type of nanoparticles containing substances called conjugated polymers that light up and stay illuminated long enough for scientists to string together thousands of images, as in a movie.

Conjugated polymers share many properties with semiconductors, such as silicon, but have the flexibility of plastic. While early efforts at preparing nanoparticles out of conjugated polymers resulted in particles that were very bright, their brightness quickly faded under the bright glare of a laser beam.

"When a conjugated polymer is in a high energy state, it is vulnerable to attack by oxygen,” stated lead investigator and chemist Dr. Jason McNeill. "The dye efficiently removes the energy from the molecule and re-emits the energy as light, which greatly improves the brightness and longevity of the nanoparticles.”

Dr. McNeill reported that other possible targets of study include the formation of plaques and fibrils in the brain associated with Alzheimer's disease and mad cow disease.

The study's findings were presented at the annual American Chemical Society meeting held on August 19-24, 2007, in Boston, MA, USA.


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