PNAS: Biophotonic imaging reveals real-time cell death changes
Scientists have developed a biophotonic imaging approach for studying the molecular organization and its transformation in cellular processes, with the specific example of apoptosis, according to a study published July 20 in Proceedings of National Academy of Sciences.  

Apoptosis is a process of self-initiated cell death, critically important for physiological regulation and elimination of genetic disorders. The work could help realize the potential of customized molecular medicine, in which chemotherapy, for example, can be precisely targeted to cellular changes exhibited by individual patients. It can also be a valuable drug development tool for screening new compounds, according to Paras N. Prasad, PhD, senior author and executive director of the University at Buffalo Institute for Lasers, Photonics and Biophotonics (ILPB) in Buffalo, New York.

"This new ability provides us with a dynamic mapping of the transformations occurring in the cell at the molecular level," said Prasad. "It provides us with a very clear visual picture of the dynamics of proteins, DNA, RNA and lipids during the cell's disintegration."

To capture the cellular images, the interdisciplinary University at Buffalo team of biologists, chemists and physicists, led by Prasad, utilized an advanced biophotonic approach that combines three techniques: a nonlinear, optical imaging system (CARS or Coherent anti-Stokes Raman scattering), TPEF (two-photon excited fluorescence), which images living tissue and cells at deep penetration and Fluorescence Recovery after Photobleaching (FRAP) to measure dynamics of proteins.

"For the first time, this approach allows us to monitor in a single scan, four different types of images, characterizing the distribution of proteins, DNA, RNA and lipids in the cell," said co-author Aliaksandr V. Kachynski, PhD, research associate professor at the ILPB.

The resulting composite image integrates in one picture the information on all four types of biomolecules, with each type of molecule represented by a different color: proteins in red, RNA in green, DNA in blue and lipids in grey.

Before apoptosis was induced, the distribution of proteins was relatively uniform, but once apoptosis develops, nuclear structures disintegrate, the proteins become irregularly distributed and their diffusion rate slows down, said co-author Artem M. Pliss, PhD, research assistant professor at the ILPB.

Such precise information will be especially useful for monitoring how specific cancer drugs affect individual cells. "For example, say drug therapy is being administered to a cancer patient; this system will allow for the monitoring of cellular changes throughout the treatment process," noted Kachynski. "Clinicians will be able to determine the optimal conditions to kill a cancer cell for the particular type of disease. An improved understanding of the drug-biomolecule interactions will help discover the optimal treatment doses so as to minimize side effects."