Noninvasive Green Fluorescent Proteins Help Measure Intracellular Heat

A technique to measure internal cell temperatures could be used to differentiate normal cells from cancerous ones in a quick, noninvasive manner.

A European research team led by the Institute of Photonic Sciences (ICFO; Barcelona, Spain), which has the Severo Ochoa mark of excellence, has published a noninvasive method that offers quicker, precise data from measuring intracellular heat from green fluorescent proteins (GFP) in the journal Nano Letters on March 6, 2012.

In the interdisciplinary study, physical measurements of energy transmission were used to study processes such as gene expression, metabolism, and cell splitting.

The technique used is known as fluorescence polarization anisotropy (FPA) as it measures the difference in polarization between light that fluorescent molecules receive, and that which they emit later. Roman Quidant, IFCO investigator and study coordinator noted, "this difference in polarization (anisotropy) is directly connected to the rotating of the GFP molecules and therefore with temperature."

"A unique characteristic of our method is that it does not alter any cellular process," Romain Quidant explained to the Scientific Information and News Service (SINC). Unlike other techniques, this method does not stress or alter the behavior of the cell, as it does not need to be inserted into any molecules or any other synthetic nano-object that is sensitive to the internal temperature.

One of the most promising outcomes of the method is a better understanding of cellular processes, such as those involved in metastasis. Additionally, from intracellular temperature, energy used by the body can be determined in the uncontrolled spreading of cancer cells.

The authors of the study are sure that biologists will be able to implement this technique in experimental set-ups and obtain the cell temperature as another observable detail. The option of measuring intracellular activity could establish the basis to develop a field that has not been widely studied: thermal biology at cellular level.

The method's sensitivity and resolution still need to be improved. The scientists are working to fine tune the properties of the fluorescent proteins and optimize the detection method of its thermometer.

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