Researchers are making strides in the field of drug discovery, thanks to holography and lasers. They are now able to detect motion inside three-dimensional tumor spheroids that could show how various drug candidates affect intracellular structures. Researchers at Purdue University have developed holographic tissue dynamics spectroscopy, a technique to measure the living motion inside a cell and to determine the cell’s response to applied drugs. The technology was highlighted in a letter in the Journal of Biomedical Optics. The spectrogram shows how cells react to drugs; for instance, when they interact with a metabolic drug (iodo-acetate) in comparison to an antimitosis drug (cytochalasin). Courtesy of David D. Nolte, Purdue University. The scientists were able to view a tumor’s tissues in three dimensions using holography. Using the holographic technique with lasers allows them to see the tumor’s interior as well as its surface. Like polarized sunglasses, the approach cancels the effect of any light scattered by skin and tissues, uncovering the image-bearing light that is already there. Images similar to voiceprints used in voice recognition security software are left that can show changes taking place within the cells. Upon completion of the hologram, the researchers use fluctuation spectroscopy to measure time-dependent changes within the hologram. They measure the frequency of light fluctuations as a function of time after a drug has been administered. The resulting spectrogram represents a voiceprint of the drug used on the cells, enabling drug researchers and manufacturers to see how various drug candidates affect organlike structures within a cell. With its high throughput, the technology will soon allow manufacturers to more quickly determine which drugs are most effective in battling tumors and other tissue diseases.