To determine a cell’s metabolism, scientists need to know how much oxygen it consumes, but current technology limits this study to groups of cells, not individual cells. Now, Dr. Lihong Wang plans to change that. Wang, the Gene K. Beare Distinguished Professor of Biomedical Engineering at Washington University in St. Louis, has received a three-year, $300,000 grant from the National Science Foundation (NSF) to study oxygen consumption rates of individual cells using photoacoustic microscopy, a novel imaging method he developed that uses light and sound to measure change. ”When you image a group of cells, you assume all cells are identical, but they are not — cells are heterogeneous and consume oxygen differently," said Wang, who also is affiliated with the Siteman Cancer Center at Barnes-Jewish Hospital and Washington University School of Medicine. "We will measure oxygen consumption on a per-cell basis but measure many cells at the same time, giving us high specificity and a high-speed, high-yield throughput. As a result, we will be able to rapidly map distributions of cellular metabolism.” Hemoglobin, a protein in red blood cells that carries oxygen, will be used as a biocompatible sensor to determine oxygen consumption. When oxygenated or deoxygenated, the protein changes color, but this change is too slight to see using conventional microscopy, confocal microscopy or two-photon microscopy. Wang’s photoacoustic microscopy method, however, is extremely sensitive to the color change, he said. "Once cells are loaded into a matrix of wells, all we have to do is to use light-induced ultrasound to sense the color of hemoglobin next to each well," Wang says. "The rate of change in color of hemoglobin is used to compute the consumption rate of oxygen by each cell." The proposed method could further the understanding of biological systems from single cells to ecosystems, he said. Potential applications include gauging cellular health and metabolic state for stress response; the technique also could be used in toxicity studies. Differences in oxygen uptake within complex natural communities could lend insight into primary production and the use of energy sources in the environment. Wang is collaborating with Dr. Jun Zou, an associate professor of electrical and computer engineering at Texas A&M University. He has received more than 30 research grants for his work developing new methods of cancer imaging, including the photoacoustic tomography technique, which relies on light and sound to create detailed color pictures of tumors deep inside the body. (See: Photoacoustic imaging penetrates deeply into skin). For more information, visit: www.wustl.edu