A noninvasive method that measures internal cell temperatures using green fluorescent proteins (GFPs) could help scientists to learn more about cellular processes and to distinguish healthy cells from cancerous ones. The technique, which was developed by a European research team led by the Institute of Photonic Sciences (ICFO), measures intracellular heat without altering the cells’ metabolism, and more quickly and precisely than earlier methods. “A unique characteristic of our method is that it does not alter any cellular process,” said Romain Quidant, an ICFO researcher and coordinator of the study. The green fluorescent proteins help measure intracellular heat. (Image: Richard Wheeler) Unlike other techniques, this method does not stress or alter the behavior of the cell because it does not need to be inserted into any molecules or any other synthetic nano-object that is sensitive to the internal temperature. Intracellular temperatures make it possible to study the body’s energy flow during the uncontrolled spreading of cancer cells. Measurement of energy transmission can help investigate processes such as gene expression, metabolism and cell splitting. Using fluorescence polarization anisotropy, the team measured the polarization difference between light that fluorescent molecules received and that which they emitted later. “This difference in polarization (anisotropy) is directly connected to the rotating of the GFP molecules and therefore with temperature,” Quidant said. Biologists will be able to implement this technique in experimental setups and to obtain the cell temperature as another observable detail, the scientists said. Harnessing the ability to measure intracellular activity could be instrumental in developing a field that has not been widely studied: thermal biology at the cellular level. Next, the ICFO team plans to improve the method’s sensitivity and resolution. To achieve this, its members hope to fine-tune the properties of the fluorescent proteins to optimize the detection method of their “thermometer.” The research was published in Nano Letters. For more information, visit: www.icfo.es